Merge pull request #1337 from lightpanda-io/ci-check

ci: try to fix tag

.github/actions/install/action.yml

@@ -2,10 +2,6 @@ name: "Browsercore install"
 description: "Install deps for the project browsercore"
 
 inputs:
-  zig:
-    description: 'Zig version to install'
-    required: false
-    default: '0.15.1'
   arch:
     description: 'CPU arch used to select the v8 lib'
     required: false
@@ -17,7 +13,7 @@ inputs:
   zig-v8:
     description: 'zig v8 version to install'
     required: false
-    default: 'v0.1.30'
+    default: 'v0.1.35'
   v8:
     description: 'v8 version to install'
     required: false
@@ -38,9 +34,8 @@ runs:
         sudo apt-get update
         sudo apt-get install -y wget xz-utils python3 ca-certificates git pkg-config libglib2.0-dev gperf libexpat1-dev cmake clang
 
+    # Zig version used from the `minimum_zig_version` field in build.zig.zon
     - uses: mlugg/setup-zig@v2
-      with:
-        version: ${{ inputs.zig }}
 
     - name: Cache v8
       id: cache-v8
@@ -61,11 +56,8 @@ runs:
     - name: install v8
       shell: bash
       run: |
-        mkdir -p v8/out/${{ inputs.os }}/debug/obj/zig/
-        ln -s ${{ inputs.cache-dir }}/v8/libc_v8.a v8/out/${{ inputs.os }}/debug/obj/zig/libc_v8.a
-
-        mkdir -p v8/out/${{ inputs.os }}/release/obj/zig/
-        ln -s ${{ inputs.cache-dir }}/v8/libc_v8.a v8/out/${{ inputs.os }}/release/obj/zig/libc_v8.a
+        mkdir -p v8
+        ln -s ${{ inputs.cache-dir }}/v8/libc_v8.a v8/libc_v8.a
 
     - name: Cache libiconv
       id: cache-libiconv

.github/workflows/build.yml

@@ -5,8 +5,12 @@ env:
   AWS_SECRET_ACCESS_KEY: ${{ secrets.NIGHTLY_BUILD_AWS_SECRET_ACCESS_KEY }}
   AWS_BUCKET: ${{ vars.NIGHTLY_BUILD_AWS_BUCKET }}
   AWS_REGION: ${{ vars.NIGHTLY_BUILD_AWS_REGION }}
+  RELEASE: ${{ github.ref_type == 'tag' && github.ref_name || 'nightly' }}
 
 on:
+  push:
+    tags:
+      - '*'
   schedule:
     - cron: "2 2 * * *"
 
@@ -26,10 +30,9 @@ jobs:
     timeout-minutes: 15
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
-          # fetch submodules recusively, to get zig-js-runtime submodules also.
           submodules: recursive
 
       - uses: ./.github/actions/install
@@ -38,7 +41,7 @@ jobs:
           arch: ${{env.ARCH}}
 
       - name: zig build
-        run: zig build --release=safe -Doptimize=ReleaseSafe -Dcpu=x86_64 -Dgit_commit=$(git rev-parse --short ${{ github.sha }})
+        run: zig build -Dprebuilt_v8_path=v8/libc_v8.a -Doptimize=ReleaseSafe -Dcpu=x86_64 -Dgit_commit=$(git rev-parse --short ${{ github.sha }})
 
       - name: Rename binary
         run: mv zig-out/bin/lightpanda lightpanda-${{ env.ARCH }}-${{ env.OS }}
@@ -53,7 +56,7 @@ jobs:
         with:
           allowUpdates: true
           artifacts: lightpanda-${{ env.ARCH }}-${{ env.OS }}
-          tag: nightly
+          tag: ${{ env.RELEASE }}
 
   build-linux-aarch64:
     env:
@@ -76,7 +79,7 @@ jobs:
           arch: ${{env.ARCH}}
 
       - name: zig build
-        run: zig build --release=safe -Doptimize=ReleaseSafe -Dcpu=generic -Dgit_commit=$(git rev-parse --short ${{ github.sha }})
+        run: zig build -Dprebuilt_v8_path=v8/libc_v8.a -Doptimize=ReleaseSafe -Dcpu=generic -Dgit_commit=$(git rev-parse --short ${{ github.sha }})
 
       - name: Rename binary
         run: mv zig-out/bin/lightpanda lightpanda-${{ env.ARCH }}-${{ env.OS }}
@@ -91,7 +94,7 @@ jobs:
         with:
           allowUpdates: true
           artifacts: lightpanda-${{ env.ARCH }}-${{ env.OS }}
-          tag: nightly
+          tag: ${{ env.RELEASE }}
 
   build-macos-aarch64:
     env:
@@ -116,7 +119,7 @@ jobs:
           arch: ${{env.ARCH}}
 
       - name: zig build
-        run: zig build --release=safe -Doptimize=ReleaseSafe -Dgit_commit=$(git rev-parse --short ${{ github.sha }})
+        run: zig build -Dprebuilt_v8_path=v8/libc_v8.a -Doptimize=ReleaseSafe -Dgit_commit=$(git rev-parse --short ${{ github.sha }})
 
       - name: Rename binary
         run: mv zig-out/bin/lightpanda lightpanda-${{ env.ARCH }}-${{ env.OS }}
@@ -131,19 +134,14 @@ jobs:
         with:
           allowUpdates: true
           artifacts: lightpanda-${{ env.ARCH }}-${{ env.OS }}
-          tag: nightly
+          tag: ${{ env.RELEASE }}
 
   build-macos-x86_64:
     env:
       ARCH: x86_64
       OS: macos
 
-    # macos-13 runs on x86 CPU. see
-    # https://github.com/actions/runner-images?tab=readme-ov-file
-    # If we want to build for macos-14 or superior, we need to switch to
-    # macos-14-large.
-    # No need for now, but maybe we will need it in the short term.
-    runs-on: macos-13
+    runs-on: macos-14-large
     timeout-minutes: 15
 
     steps:
@@ -159,7 +157,7 @@ jobs:
           arch: ${{env.ARCH}}
 
       - name: zig build
-        run: zig build --release=safe -Doptimize=ReleaseSafe -Dgit_commit=$(git rev-parse --short ${{ github.sha }})
+        run: zig build -Dprebuilt_v8_path=v8/libc_v8.a -Doptimize=ReleaseSafe -Dgit_commit=$(git rev-parse --short ${{ github.sha }})
 
       - name: Rename binary
         run: mv zig-out/bin/lightpanda lightpanda-${{ env.ARCH }}-${{ env.OS }}
@@ -174,4 +172,4 @@ jobs:
         with:
           allowUpdates: true
           artifacts: lightpanda-${{ env.ARCH }}-${{ env.OS }}
-          tag: nightly
+          tag: ${{ env.RELEASE }}

.github/workflows/cla.yml

@@ -28,7 +28,7 @@ jobs:
           path-to-document: 'https://github.com/lightpanda-io/browser/blob/main/CLA.md'
           # branch should not be protected
           branch: 'main'
-          allowlist: krichprollsch,francisbouvier,katie-lpd,sjorsdonkers,bornlex
+          allowlist: krichprollsch,francisbouvier,katie-lpd
 
           remote-organization-name: lightpanda-io
           remote-repository-name: cla

.github/workflows/e2e-integration-test.yml

@@ -0,0 +1,68 @@
+name: e2e-integration-test
+
+env:
+  LIGHTPANDA_DISABLE_TELEMETRY: true
+
+on:
+  schedule:
+    - cron: "4 4 * * *"
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+jobs:
+  zig-build-release:
+    name: zig build release
+
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+
+    # Don't run the CI with draft PR.
+    if: github.event.pull_request.draft == false
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          # fetch submodules recusively, to get zig-js-runtime submodules also.
+          submodules: recursive
+
+      - uses: ./.github/actions/install
+
+      - name: zig build release
+        run: zig build -Dprebuilt_v8_path=v8/libc_v8.a -Doptimize=ReleaseFast -Dcpu=x86_64 -Dgit_commit=$(git rev-parse --short ${{ github.sha }})
+
+      - name: upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: lightpanda-build-release
+          path: |
+            zig-out/bin/lightpanda
+          retention-days: 1
+
+  demo-scripts:
+    name: demo-integration-scripts
+    needs: zig-build-release
+
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          repository: 'lightpanda-io/demo'
+          fetch-depth: 0
+
+      - run: npm install
+
+      - name: download artifact
+        uses: actions/download-artifact@v4
+        with:
+          name: lightpanda-build-release
+
+      - run: chmod a+x ./lightpanda
+
+      - name: run end to end integration tests
+        run: |
+          ./lightpanda serve & echo $! > LPD.pid
+          go run integration/main.go
+          kill `cat LPD.pid`

.github/workflows/e2e-test.yml

@@ -49,16 +49,15 @@ jobs:
     if: github.event.pull_request.draft == false
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
-          # fetch submodules recusively, to get zig-js-runtime submodules also.
           submodules: recursive
 
       - uses: ./.github/actions/install
 
       - name: zig build release
-        run: zig build -Doptimize=ReleaseFast -Dcpu=x86_64 -Dgit_commit=$(git rev-parse --short ${{ github.sha }})
+        run: zig build -Dprebuilt_v8_path=v8/libc_v8.a -Doptimize=ReleaseFast -Dcpu=x86_64 -Dgit_commit=$(git rev-parse --short ${{ github.sha }})
 
       - name: upload artifact
         uses: actions/upload-artifact@v4
@@ -122,7 +121,7 @@ jobs:
     needs: zig-build-release
 
     env:
-      MAX_MEMORY: 27000
+      MAX_MEMORY: 28000
       MAX_AVG_DURATION: 23
       LIGHTPANDA_DISABLE_TELEMETRY: true
 

.github/workflows/wpt.yml

@@ -22,16 +22,15 @@ jobs:
     timeout-minutes: 90
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
-          # fetch submodules recusively, to get zig-js-runtime submodules also.
           submodules: recursive
 
       - uses: ./.github/actions/install
 
       - name: json output
-        run: zig build -Doptimize=ReleaseFast wpt -- --json > wpt.json
+        run: zig build wpt -- --json > wpt.json
 
       - name: write commit
         run: |

.github/workflows/zig-fmt.yml

@@ -1,8 +1,5 @@
 name: zig-fmt
 
-env:
-  ZIG_VERSION: 0.15.1
-
 on:
   pull_request:
 
@@ -32,14 +29,13 @@ jobs:
     timeout-minutes: 15
 
     steps:
-      - uses: mlugg/setup-zig@v2
-        with:
-          version: ${{ env.ZIG_VERSION }}
-
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 
+      # Zig version used from the `minimum_zig_version` field in build.zig.zon
+      - uses: mlugg/setup-zig@v2
+
       - name: Run zig fmt
         id: fmt
         run: |
@@ -58,6 +54,7 @@ jobs:
           fi
 
           echo "${delimiter}" >> "${GITHUB_OUTPUT}"
+
       - name: Fail the job
         if: steps.fmt.outputs.zig_fmt_errs != ''
         run: exit 1

.github/workflows/zig-test.yml

@@ -47,16 +47,15 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
-          # fetch submodules recusively, to get zig-js-runtime submodules also.
           submodules: recursive
 
       - uses: ./.github/actions/install
 
       - name: zig build debug
-        run: zig build
+        run: zig build -Dprebuilt_v8_path=v8/libc_v8.a
 
       - name: upload artifact
         uses: actions/upload-artifact@v4
@@ -104,7 +103,7 @@ jobs:
       - uses: ./.github/actions/install
 
       - name: zig build test
-        run: zig build test -- --json > bench.json
+        run: zig build  -Dprebuilt_v8_path=v8/libc_v8.a test -- --json > bench.json
 
       - name: write commit
         run: |

.gitignore

@@ -1,5 +1,6 @@
 zig-cache
 /.zig-cache/
+/.lp-cache/
 zig-out
 /vendor/netsurf/out
 /vendor/libiconv/

.gitmodules

@@ -22,12 +22,12 @@
 [submodule "vendor/nghttp2"]
 	path = vendor/nghttp2
 	url = https://github.com/nghttp2/nghttp2.git
-[submodule "vendor/mbedtls"]
-	path = vendor/mbedtls
-	url = https://github.com/Mbed-TLS/mbedtls.git
 [submodule "vendor/zlib"]
 	path = vendor/zlib
 	url = https://github.com/madler/zlib.git
 [submodule "vendor/curl"]
 	path = vendor/curl
 	url = https://github.com/curl/curl.git
+[submodule "vendor/brotli"]
+	path = vendor/brotli
+	url = https://github.com/google/brotli

Dockerfile

@@ -1,10 +1,9 @@
-FROM debian:stable
+FROM debian:stable-slim
 
 ARG MINISIG=0.12
-ARG ZIG=0.15.1
 ARG ZIG_MINISIG=RWSGOq2NVecA2UPNdBUZykf1CCb147pkmdtYxgb3Ti+JO/wCYvhbAb/U
 ARG V8=14.0.365.4
-ARG ZIG_V8=v0.1.30
+ARG ZIG_V8=v0.1.34
 ARG TARGETPLATFORM
 
 RUN apt-get update -yq && \
@@ -17,25 +16,25 @@ RUN apt-get update -yq && \
 
 # install minisig
 RUN curl --fail -L -O https://github.com/jedisct1/minisign/releases/download/${MINISIG}/minisign-${MINISIG}-linux.tar.gz && \
-    tar xvzf minisign-${MINISIG}-linux.tar.gz
-
-# install zig
-RUN case $TARGETPLATFORM in \
-    "linux/arm64") ARCH="aarch64" ;; \
-    *) ARCH="x86_64" ;; \
-    esac && \
-    curl --fail -L -O https://ziglang.org/download/${ZIG}/zig-${ARCH}-linux-${ZIG}.tar.xz && \
-    curl --fail -L -O https://ziglang.org/download/${ZIG}/zig-${ARCH}-linux-${ZIG}.tar.xz.minisig && \
-    minisign-linux/${ARCH}/minisign -Vm zig-${ARCH}-linux-${ZIG}.tar.xz -P ${ZIG_MINISIG} && \
-    tar xvf zig-${ARCH}-linux-${ZIG}.tar.xz && \
-    mv zig-${ARCH}-linux-${ZIG} /usr/local/lib && \
-    ln -s /usr/local/lib/zig-${ARCH}-linux-${ZIG}/zig /usr/local/bin/zig
+    tar xvzf minisign-${MINISIG}-linux.tar.gz -C /
 
 # clone lightpanda
 RUN git clone https://github.com/lightpanda-io/browser.git
-
 WORKDIR /browser
 
+# install zig
+RUN ZIG=$(grep '\.minimum_zig_version = "' "build.zig.zon" | cut -d'"' -f2) && \
+    case $TARGETPLATFORM in \
+      "linux/arm64") ARCH="aarch64" ;; \
+      *) ARCH="x86_64" ;; \
+    esac && \
+    curl --fail -L -O https://ziglang.org/download/${ZIG}/zig-${ARCH}-linux-${ZIG}.tar.xz && \
+    curl --fail -L -O https://ziglang.org/download/${ZIG}/zig-${ARCH}-linux-${ZIG}.tar.xz.minisig && \
+    /minisign-linux/${ARCH}/minisign -Vm zig-${ARCH}-linux-${ZIG}.tar.xz -P ${ZIG_MINISIG} && \
+    tar xvf zig-${ARCH}-linux-${ZIG}.tar.xz && \
+    mv zig-${ARCH}-linux-${ZIG} /usr/local/lib && \
+    ln -s /usr/local/lib/zig-${ARCH}-linux-${ZIG}/zig /usr/local/bin/zig
+
 # install deps
 RUN git submodule init && \
     git submodule update --recursive
@@ -50,11 +49,16 @@ RUN case $TARGETPLATFORM in \
     *) ARCH="x86_64" ;; \
     esac && \
     curl --fail -L -o libc_v8.a https://github.com/lightpanda-io/zig-v8-fork/releases/download/${ZIG_V8}/libc_v8_${V8}_linux_${ARCH}.a && \
-    mkdir -p v8/out/linux/release/obj/zig/ && \
-    mv libc_v8.a v8/out/linux/release/obj/zig/libc_v8.a
+    mkdir -p v8/ && \
+    mv libc_v8.a v8/libc_v8.a
 
 # build release
-RUN make build
+RUN zig build -Doptimize=ReleaseSafe -Dprebuilt_v8_path=v8/libc_v8.a -Dgit_commit=$$(git rev-parse --short HEAD)
+
+FROM debian:stable-slim
+
+RUN apt-get update -yq && \
+    apt-get install -yq tini
 
 FROM debian:stable-slim
 
@@ -62,7 +66,12 @@ FROM debian:stable-slim
 COPY --from=0 /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
 
 COPY --from=0 /browser/zig-out/bin/lightpanda /bin/lightpanda
+COPY --from=1 /usr/bin/tini /usr/bin/tini
 
 EXPOSE 9222/tcp
 
-CMD ["/bin/lightpanda", "serve", "--host", "0.0.0.0", "--port", "9222"]
+# Lightpanda install only some signal handlers, and PID 1 doesn't have a default SIGTERM signal handler.
+# Using "tini" as PID1 ensures that signals work as expected, so e.g. "docker stop" will not hang.
+# (See https://github.com/krallin/tini#why-tini).
+ENTRYPOINT ["/usr/bin/tini", "--"]
+CMD ["/bin/lightpanda", "serve", "--host", "0.0.0.0", "--port", "9222", "--log_level", "info"]

Makefile

@@ -34,7 +34,7 @@ endif
 
 ## Display this help screen
 help:
-	@printf "\e[36m%-35s %s\e[0m\n" "Command" "Usage"
+	@printf "\033[36m%-35s %s\033[0m\n" "Command" "Usage"
 	@sed -n -e '/^## /{'\
 		-e 's/## //g;'\
 		-e 'h;'\
@@ -47,77 +47,60 @@ help:
 
 # $(ZIG) commands
 # ------------
-.PHONY: build build-dev run run-release shell test bench download-zig wpt data get-v8 build-v8 build-v8-dev
-.PHONY: end2end
-
-zig_version = $(shell grep 'recommended_zig_version = "' "vendor/zig-js-runtime/build.zig" | cut -d'"' -f2)
-
-## Download the zig recommended version
-download-zig:
-	$(eval url = "https://ziglang.org/download/$(zig_version)/zig-$(OS)-$(ARCH)-$(zig_version).tar.xz")
-	$(eval dest = "/tmp/zig-$(OS)-$(ARCH)-$(zig_version).tar.xz")
-	@printf "\e[36mDownload zig version $(zig_version)...\e[0m\n"
-	@curl -o "$(dest)" -L "$(url)" || (printf "\e[33mBuild ERROR\e[0m\n"; exit 1;)
-	@printf "\e[33mDownloaded $(dest)\e[0m\n"
+.PHONY: build build-dev run run-release shell test bench wpt data end2end
 
 ## Build in release-safe mode
 build:
-	@printf "\e[36mBuilding (release safe)...\e[0m\n"
-	$(ZIG) build -Doptimize=ReleaseSafe -Dgit_commit=$$(git rev-parse --short HEAD) || (printf "\e[33mBuild ERROR\e[0m\n"; exit 1;)
-	@printf "\e[33mBuild OK\e[0m\n"
+	@printf "\033[36mBuilding (release safe)...\033[0m\n"
+	$(ZIG) build -Doptimize=ReleaseSafe -Dgit_commit=$$(git rev-parse --short HEAD) || (printf "\033[33mBuild ERROR\033[0m\n"; exit 1;)
+	@printf "\033[33mBuild OK\033[0m\n"
 
 ## Build in debug mode
 build-dev:
-	@printf "\e[36mBuilding (debug)...\e[0m\n"
-	@$(ZIG) build -Dgit_commit=$$(git rev-parse --short HEAD) || (printf "\e[33mBuild ERROR\e[0m\n"; exit 1;)
-	@printf "\e[33mBuild OK\e[0m\n"
+	@printf "\033[36mBuilding (debug)...\033[0m\n"
+	@$(ZIG) build -Dgit_commit=$$(git rev-parse --short HEAD) || (printf "\033[33mBuild ERROR\033[0m\n"; exit 1;)
+	@printf "\033[33mBuild OK\033[0m\n"
 
 ## Run the server in release mode
 run: build
-	@printf "\e[36mRunning...\e[0m\n"
-	@./zig-out/bin/lightpanda || (printf "\e[33mRun ERROR\e[0m\n"; exit 1;)
+	@printf "\033[36mRunning...\033[0m\n"
+	@./zig-out/bin/lightpanda || (printf "\033[33mRun ERROR\033[0m\n"; exit 1;)
 
 ## Run the server in debug mode
 run-debug: build-dev
-	@printf "\e[36mRunning...\e[0m\n"
-	@./zig-out/bin/lightpanda || (printf "\e[33mRun ERROR\e[0m\n"; exit 1;)
+	@printf "\033[36mRunning...\033[0m\n"
+	@./zig-out/bin/lightpanda || (printf "\033[33mRun ERROR\033[0m\n"; exit 1;)
 
 ## Run a JS shell in debug mode
 shell:
-	@printf "\e[36mBuilding shell...\e[0m\n"
-	@$(ZIG) build shell || (printf "\e[33mBuild ERROR\e[0m\n"; exit 1;)
+	@printf "\033[36mBuilding shell...\033[0m\n"
+	@$(ZIG) build shell || (printf "\033[33mBuild ERROR\033[0m\n"; exit 1;)
 
 ## Run WPT tests
 wpt:
-	@printf "\e[36mBuilding wpt...\e[0m\n"
-	@$(ZIG) build wpt -- $(filter-out $@,$(MAKECMDGOALS)) || (printf "\e[33mBuild ERROR\e[0m\n"; exit 1;)
+	@printf "\033[36mBuilding wpt...\033[0m\n"
+	@$(ZIG) build wpt -- $(filter-out $@,$(MAKECMDGOALS)) || (printf "\033[33mBuild ERROR\033[0m\n"; exit 1;)
 
 wpt-summary:
-	@printf "\e[36mBuilding wpt...\e[0m\n"
-	@$(ZIG) build wpt -- --summary $(filter-out $@,$(MAKECMDGOALS)) || (printf "\e[33mBuild ERROR\e[0m\n"; exit 1;)
+	@printf "\033[36mBuilding wpt...\033[0m\n"
+	@$(ZIG) build wpt -- --summary $(filter-out $@,$(MAKECMDGOALS)) || (printf "\033[33mBuild ERROR\033[0m\n"; exit 1;)
 
-## Test
+## Test - `grep` is used to filter out the huge compile command on build
+ifeq ($(OS), macos)
 test:
-	@TEST_FILTER='${F}' $(ZIG) build test -freference-trace --summary all
+	@script -q /dev/null sh -c 'TEST_FILTER="${F}" $(ZIG) build test -freference-trace --summary all' 2>&1 \
+		| grep --line-buffered -v "^/.*zig test -freference-trace"
+else
+test:
+	@script -qec 'TEST_FILTER="${F}" $(ZIG) build test -freference-trace --summary all' /dev/null 2>&1 \
+		| grep --line-buffered -v "^/.*zig test -freference-trace"
+endif
 
 ## Run demo/runner end to end tests
 end2end:
 	@test -d ../demo
 	cd ../demo && go run runner/main.go
 
-## v8
-get-v8:
-	@printf "\e[36mGetting v8 source...\e[0m\n"
-	@$(ZIG) build get-v8
-
-build-v8-dev:
-	@printf "\e[36mBuilding v8 (dev)...\e[0m\n"
-	@$(ZIG) build build-v8
-
-build-v8:
-	@printf "\e[36mBuilding v8...\e[0m\n"
-	@$(ZIG) build -Doptimize=ReleaseSafe build-v8
-
 # Install and build required dependencies commands
 # ------------
 .PHONY: install-submodule
@@ -144,27 +127,27 @@ ICONV := $(BC)vendor/libiconv/out/$(OS)-$(ARCH)
 # TODO: this way of linking libiconv is not ideal. We should have a more generic way
 # and stick to a specif version. Maybe build from source. Anyway not now.
 _install-netsurf: clean-netsurf
-	@printf "\e[36mInstalling NetSurf...\e[0m\n" && \
-	ls $(ICONV)/lib/libiconv.a 1> /dev/null || (printf "\e[33mERROR: you need to execute 'make install-libiconv'\e[0m\n"; exit 1;) && \
+	@printf "\033[36mInstalling NetSurf...\033[0m\n" && \
+	ls $(ICONV)/lib/libiconv.a 1> /dev/null || (printf "\033[33mERROR: you need to execute 'make install-libiconv'\033[0m\n"; exit 1;) && \
 	mkdir -p $(BC_NS) && \
 	cp -R vendor/netsurf/share $(BC_NS) && \
 	export PREFIX=$(BC_NS) && \
 	export OPTLDFLAGS="-L$(ICONV)/lib" && \
 	export OPTCFLAGS="$(OPTCFLAGS) -I$(ICONV)/include" && \
-	printf "\e[33mInstalling libwapcaplet...\e[0m\n" && \
+	printf "\033[33mInstalling libwapcaplet...\033[0m\n" && \
 	cd vendor/netsurf/libwapcaplet && \
 	BUILDDIR=$(BC_NS)/build/libwapcaplet make install && \
 	cd ../libparserutils && \
-	printf "\e[33mInstalling libparserutils...\e[0m\n" && \
+	printf "\033[33mInstalling libparserutils...\033[0m\n" && \
 	BUILDDIR=$(BC_NS)/build/libparserutils make install && \
 	cd ../libhubbub && \
-	printf "\e[33mInstalling libhubbub...\e[0m\n" && \
+	printf "\033[33mInstalling libhubbub...\033[0m\n" && \
 	BUILDDIR=$(BC_NS)/build/libhubbub make install && \
 	rm src/treebuilder/autogenerated-element-type.c && \
 	cd ../libdom && \
-	printf "\e[33mInstalling libdom...\e[0m\n" && \
+	printf "\033[33mInstalling libdom...\033[0m\n" && \
 	BUILDDIR=$(BC_NS)/build/libdom make install && \
-	printf "\e[33mRunning libdom example...\e[0m\n" && \
+	printf "\033[33mRunning libdom example...\033[0m\n" && \
 	cd examples && \
 	$(ZIG) cc \
 	-I$(ICONV)/include \
@@ -181,14 +164,14 @@ _install-netsurf: clean-netsurf
 	$(ICONV)/lib/libiconv.a && \
 	./a.out > /dev/null && \
 	rm a.out && \
-	printf "\e[36mDone NetSurf $(OS)\e[0m\n"
+	printf "\033[36mDone NetSurf $(OS)\033[0m\n"
 
 clean-netsurf:
-	@printf "\e[36mCleaning NetSurf build...\e[0m\n" && \
+	@printf "\033[36mCleaning NetSurf build...\033[0m\n" && \
 	rm -Rf $(BC_NS)
 
 test-netsurf:
-	@printf "\e[36mTesting NetSurf...\e[0m\n" && \
+	@printf "\033[36mTesting NetSurf...\033[0m\n" && \
 	export PREFIX=$(BC_NS) && \
 	export LDFLAGS="-L$(ICONV)/lib -L$(BC_NS)/lib" && \
 	export CFLAGS="-I$(ICONV)/include -I$(BC_NS)/include" && \

README.md

@@ -18,7 +18,7 @@ Lightpanda is the open-source browser made for headless usage:
 
 - Javascript execution
 - Support of Web APIs (partial, WIP)
-- Compatible with Playwright[^1], Puppeteer, chromedp through CDP
+- Compatible with Playwright[^1], Puppeteer, chromedp through [CDP](https://chromedevtools.github.io/devtools-protocol/)
 
 Fast web automation for AI agents, LLM training, scraping and testing:
 
@@ -158,22 +158,21 @@ Here are the key features we have implemented:
 
 NOTE: There are hundreds of Web APIs. Developing a browser (even just for headless mode) is a huge task. Coverage will increase over time.
 
-You can also follow the progress of our Javascript support in our dedicated [zig-js-runtime](https://github.com/lightpanda-io/zig-js-runtime#development) project.
-
 ## Build from sources
 
 ### Prerequisites
 
-Lightpanda is written with [Zig](https://ziglang.org/) `0.15.1`. You have to
+Lightpanda is written with [Zig](https://ziglang.org/) `0.15.2`. You have to
 install it with the right version in order to build the project.
 
 Lightpanda also depends on
-[zig-js-runtime](https://github.com/lightpanda-io/zig-js-runtime/) (with v8),
+[zig-v8-fork](https://github.com/lightpanda-io/zig-v8-fork/),
 [Libcurl](https://curl.se/libcurl/),
+[Brotli](https://github.com/google/brotli),
 [Netsurf libs](https://www.netsurf-browser.org/) and
 [Mimalloc](https://microsoft.github.io/mimalloc).
 
-To be able to build the v8 engine for zig-js-runtime, you have to install some libs:
+To be able to build the v8 engine, you have to install some libs:
 
 For Debian/Ubuntu based Linux:
 
@@ -190,10 +189,10 @@ For systems with [Nix](https://nixos.org/download/), you can use the devShell:
 nix develop
 ```
 
-For MacOS, you only need cmake:
+For MacOS, you need [Xcode](https://developer.apple.com/xcode/) and the following pacakges from homebrew:
 
 ```
-brew install cmake
+brew install cmake pkgconf
 ```
 
 ### Install and build dependencies
@@ -246,22 +245,6 @@ Note: when Mimalloc is built in dev mode, you can dump memory stats with the
 env var `MIMALLOC_SHOW_STATS=1`. See
 [https://microsoft.github.io/mimalloc/environment.html](https://microsoft.github.io/mimalloc/environment.html).
 
-**v8**
-
-First, get the tools necessary for building V8, as well as the V8 source code:
-
-```
-make get-v8
-```
-
-Next, build v8. This build task is very long and cpu consuming, as you will build v8 from sources.
-
-```
-make build-v8
-```
-
-For dev env, use `make build-v8-dev`.
-
 ## Test
 
 ### Unit Tests

build.zig

@@ -21,36 +21,21 @@ const builtin = @import("builtin");
 
 const Build = std.Build;
 
-/// Do not rename this constant. It is scanned by some scripts to determine
-/// which zig version to install.
-const recommended_zig_version = "0.15.1";
-
 pub fn build(b: *Build) !void {
-    switch (comptime builtin.zig_version.order(std.SemanticVersion.parse(recommended_zig_version) catch unreachable)) {
-        .eq => {},
-        .lt => {
-            @compileError("The minimum version of Zig required to compile is '" ++ recommended_zig_version ++ "', found '" ++ builtin.zig_version_string ++ "'.");
-        },
-        .gt => {
-            std.debug.print(
-                "WARNING: Recommended Zig version '{s}', but found '{s}', build may fail...\n\n",
-                .{ recommended_zig_version, builtin.zig_version_string },
-            );
-        },
-    }
-
-    var opts = b.addOptions();
-    opts.addOption(
-        []const u8,
-        "git_commit",
-        b.option([]const u8, "git_commit", "Current git commit") orelse "dev",
-    );
-
     const target = b.standardTargetOptions(.{});
     const optimize = b.standardOptimizeOption(.{});
 
-    // We're still using llvm because the new x86 backend seems to crash
-    // with v8. This can be reproduced in zig-v8-fork.
+    const manifest = Manifest.init(b);
+
+    const git_commit = b.option([]const u8, "git_commit", "Current git commit");
+    const prebuilt_v8_path = b.option([]const u8, "prebuilt_v8_path", "Path to prebuilt libc_v8.a");
+
+    var opts = b.addOptions();
+    opts.addOption([]const u8, "version", manifest.version);
+    opts.addOption([]const u8, "git_commit", git_commit orelse "dev");
+
+    // We're still using llvm because the new x86 backend seems to crash with v8.
+    // This can be reproduced in zig-v8-fork.
 
     const lightpanda_module = b.addModule("lightpanda", .{
         .root_source_file = b.path("src/main.zig"),
@@ -59,7 +44,7 @@ pub fn build(b: *Build) !void {
         .link_libc = true,
         .link_libcpp = true,
     });
-    try addDependencies(b, lightpanda_module, opts);
+    try addDependencies(b, lightpanda_module, opts, prebuilt_v8_path);
 
     {
         // browser
@@ -113,7 +98,7 @@ pub fn build(b: *Build) !void {
             .target = target,
             .optimize = optimize,
         });
-        try addDependencies(b, wpt_module, opts);
+        try addDependencies(b, wpt_module, opts, prebuilt_v8_path);
 
         // compile and install
         const wpt = b.addExecutable(.{
@@ -131,27 +116,9 @@ pub fn build(b: *Build) !void {
         const wpt_step = b.step("wpt", "WPT tests");
         wpt_step.dependOn(&wpt_cmd.step);
     }
-
-    {
-        // get v8
-        // -------
-        const v8 = b.dependency("v8", .{ .target = target, .optimize = optimize });
-        const get_v8 = b.addRunArtifact(v8.artifact("get-v8"));
-        const get_step = b.step("get-v8", "Get v8");
-        get_step.dependOn(&get_v8.step);
-    }
-
-    {
-        // build v8
-        // -------
-        const v8 = b.dependency("v8", .{ .target = target, .optimize = optimize });
-        const build_v8 = b.addRunArtifact(v8.artifact("build-v8"));
-        const build_step = b.step("build-v8", "Build v8");
-        build_step.dependOn(&build_v8.step);
-    }
 }
 
-fn addDependencies(b: *Build, mod: *Build.Module, opts: *Build.Step.Options) !void {
+fn addDependencies(b: *Build, mod: *Build.Module, opts: *Build.Step.Options, prebuilt_v8_path: ?[]const u8) !void {
     try moduleNetSurf(b, mod);
     mod.addImport("build_config", opts.createModule());
 
@@ -159,6 +126,8 @@ fn addDependencies(b: *Build, mod: *Build.Module, opts: *Build.Step.Options) !vo
     const dep_opts = .{
         .target = target,
         .optimize = mod.optimize.?,
+        .prebuilt_v8_path = prebuilt_v8_path,
+        .cache_root = b.pathFromRoot(".lp-cache"),
     };
 
     mod.addIncludePath(b.path("vendor/lightpanda"));
@@ -171,36 +140,6 @@ fn addDependencies(b: *Build, mod: *Build.Module, opts: *Build.Step.Options) !vo
         const v8_mod = b.dependency("v8", dep_opts).module("v8");
         v8_mod.addOptions("default_exports", v8_opts);
         mod.addImport("v8", v8_mod);
-
-        const release_dir = if (mod.optimize.? == .Debug) "debug" else "release";
-        const os = switch (target.result.os.tag) {
-            .linux => "linux",
-            .macos => "macos",
-            else => return error.UnsupportedPlatform,
-        };
-        var lib_path = try std.fmt.allocPrint(
-            mod.owner.allocator,
-            "v8/out/{s}/{s}/obj/zig/libc_v8.a",
-            .{ os, release_dir },
-        );
-        std.fs.cwd().access(lib_path, .{}) catch {
-            // legacy path
-            lib_path = try std.fmt.allocPrint(
-                mod.owner.allocator,
-                "v8/out/{s}/obj/zig/libc_v8.a",
-                .{release_dir},
-            );
-        };
-        mod.addObjectFile(mod.owner.path(lib_path));
-
-        switch (target.result.os.tag) {
-            .macos => {
-                // v8 has a dependency, abseil-cpp, which, on Mac, uses CoreFoundation
-                mod.addSystemFrameworkPath(.{ .cwd_relative = "/System/Library/Frameworks" });
-                mod.linkFramework("CoreFoundation", .{});
-            },
-            else => {},
-        }
     }
 
     {
@@ -245,6 +184,7 @@ fn addDependencies(b: *Build, mod: *Build.Module, opts: *Build.Step.Options) !vo
             mod.addCMacro("HAVE_ASSERT_H", "1");
             mod.addCMacro("HAVE_BASENAME", "1");
             mod.addCMacro("HAVE_BOOL_T", "1");
+            mod.addCMacro("HAVE_BROTLI", "1");
             mod.addCMacro("HAVE_BUILTIN_AVAILABLE", "1");
             mod.addCMacro("HAVE_CLOCK_GETTIME_MONOTONIC", "1");
             mod.addCMacro("HAVE_DLFCN_H", "1");
@@ -373,15 +313,30 @@ fn addDependencies(b: *Build, mod: *Build.Module, opts: *Build.Step.Options) !vo
             mod.addCMacro("STDC_HEADERS", "1");
             mod.addCMacro("TIME_WITH_SYS_TIME", "1");
             mod.addCMacro("USE_NGHTTP2", "1");
-            mod.addCMacro("USE_MBEDTLS", "1");
+            mod.addCMacro("USE_OPENSSL", "1");
+            mod.addCMacro("OPENSSL_IS_BORINGSSL", "1");
             mod.addCMacro("USE_THREADS_POSIX", "1");
             mod.addCMacro("USE_UNIX_SOCKETS", "1");
         }
 
         try buildZlib(b, mod);
-        try buildMbedtls(b, mod);
+        try buildBrotli(b, mod);
+        const boringssl_dep = b.dependency("boringssl-zig", .{
+            .target = target,
+            .optimize = mod.optimize.?,
+            .force_pic = true,
+        });
+
+        const ssl = boringssl_dep.artifact("ssl");
+        ssl.bundle_ubsan_rt = false;
+        const crypto = boringssl_dep.artifact("crypto");
+        crypto.bundle_ubsan_rt = false;
+
+        mod.linkLibrary(ssl);
+        mod.linkLibrary(crypto);
         try buildNghttp2(b, mod);
         try buildCurl(b, mod);
+        try buildAda(b, mod);
 
         switch (target.result.os.tag) {
             .macos => {
@@ -484,6 +439,30 @@ fn buildZlib(b: *Build, m: *Build.Module) !void {
     } });
 }
 
+fn buildBrotli(b: *Build, m: *Build.Module) !void {
+    const brotli = b.addLibrary(.{
+        .name = "brotli",
+        .root_module = m,
+    });
+
+    const root = "vendor/brotli/c/";
+    brotli.addIncludePath(b.path(root ++ "include"));
+    brotli.addCSourceFiles(.{ .flags = &.{}, .files = &.{
+        root ++ "common/constants.c",
+        root ++ "common/context.c",
+        root ++ "common/dictionary.c",
+        root ++ "common/platform.c",
+        root ++ "common/shared_dictionary.c",
+        root ++ "common/transform.c",
+        root ++ "dec/bit_reader.c",
+        root ++ "dec/decode.c",
+        root ++ "dec/huffman.c",
+        root ++ "dec/prefix.c",
+        root ++ "dec/state.c",
+        root ++ "dec/static_init.c",
+    } });
+}
+
 fn buildMbedtls(b: *Build, m: *Build.Module) !void {
     const mbedtls = b.addLibrary(.{
         .name = "mbedtls",
@@ -815,11 +794,68 @@ fn buildCurl(b: *Build, m: *Build.Module) !void {
             root ++ "lib/vauth/spnego_sspi.c",
             root ++ "lib/vauth/vauth.c",
             root ++ "lib/vtls/cipher_suite.c",
-            root ++ "lib/vtls/mbedtls.c",
-            root ++ "lib/vtls/mbedtls_threadlock.c",
+            root ++ "lib/vtls/openssl.c",
+            root ++ "lib/vtls/hostcheck.c",
+            root ++ "lib/vtls/keylog.c",
             root ++ "lib/vtls/vtls.c",
             root ++ "lib/vtls/vtls_scache.c",
             root ++ "lib/vtls/x509asn1.c",
         },
     });
 }
+
+pub fn buildAda(b: *Build, m: *Build.Module) !void {
+    const ada_dep = b.dependency("ada-singleheader", .{});
+
+    const ada_mod = b.createModule(.{
+        .root_source_file = b.path("vendor/ada/root.zig"),
+    });
+
+    const ada_lib = b.addLibrary(.{
+        .name = "ada",
+        .root_module = b.createModule(.{
+            .link_libcpp = true,
+            .target = m.resolved_target,
+            .optimize = m.optimize,
+        }),
+        .linkage = .static,
+    });
+
+    ada_lib.addCSourceFile(.{
+        .file = ada_dep.path("ada.cpp"),
+        .flags = &.{ "-std=c++20", "-O3" },
+        .language = .cpp,
+    });
+
+    ada_lib.installHeader(ada_dep.path("ada_c.h"), "ada_c.h");
+
+    // Link the library to ada module.
+    ada_mod.linkLibrary(ada_lib);
+    // Expose ada module to main module.
+    m.addImport("ada", ada_mod);
+}
+
+const Manifest = struct {
+    version: []const u8,
+    minimum_zig_version: []const u8,
+
+    fn init(b: *std.Build) Manifest {
+        const input = @embedFile("build.zig.zon");
+
+        var diagnostics: std.zon.parse.Diagnostics = .{};
+        defer diagnostics.deinit(b.allocator);
+
+        return std.zon.parse.fromSlice(Manifest, b.allocator, input, &diagnostics, .{
+            .free_on_error = true,
+            .ignore_unknown_fields = true,
+        }) catch |err| {
+            switch (err) {
+                error.OutOfMemory => @panic("OOM"),
+                error.ParseZon => {
+                    std.debug.print("Parse diagnostics:\n{f}\n", .{diagnostics});
+                    std.process.exit(1);
+                },
+            }
+        };
+    }
+};

build.zig.zon

@@ -1,13 +1,22 @@
 .{
     .name = .browser,
-    .paths = .{""},
     .version = "0.0.0",
-    .fingerprint = 0xda130f3af836cea0,
+    .fingerprint = 0xda130f3af836cea0, // Changing this has security and trust implications.
+    .minimum_zig_version = "0.15.2",
     .dependencies = .{
         .v8 = .{
-            .url = "https://github.com/lightpanda-io/zig-v8-fork/archive/7177ee1ae267a44751a0e7e012e257177699a375.tar.gz",
-            .hash = "v8-0.0.0-xddH63TCAwC1D1hEiOtbEnLBbtz9ZPHrdiGWLcBcYQB7",
+            .url = "https://github.com/lightpanda-io/zig-v8-fork/archive/e047d2a4d5af5783763f0f6a652fab8982a08603.tar.gz",
+            .hash = "v8-0.0.0-xddH65gMBACRBQMM7EwmVgfi94FJyyX-0jpe5KhXYhfv",
+        },
+        // .v8 = .{ .path = "../zig-v8-fork" },
+        .@"ada-singleheader" = .{
+            .url = "https://github.com/ada-url/ada/releases/download/v3.3.0/singleheader.zip",
+            .hash = "N-V-__8AAPmhFAAw64ALjlzd5YMtzpSrmZ6KymsT84BKfB4s",
+        },
+        .@"boringssl-zig" = .{
+            .url = "git+https://github.com/Syndica/boringssl-zig.git#c53df00d06b02b755ad88bbf4d1202ed9687b096",
+            .hash = "boringssl-0.1.0-VtJeWehMAAA4RNnwRnzEvKcS9rjsR1QVRw1uJrwXxmVK",
         },
-        // .v8 = .{ .path = "../zig-v8-fork" }
     },
+    .paths = .{""},
 }

flake.lock

@@ -75,11 +75,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1756822655,
-        "narHash": "sha256-xQAk8xLy7srAkR5NMZFsQFioL02iTHuuEIs3ohGpgdk=",
+        "lastModified": 1760968520,
+        "narHash": "sha256-EjGslHDzCBKOVr+dnDB1CAD7wiQSHfUt3suOpFj9O1Q=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "4bdac60bfe32c41103ae500ddf894c258291dd61",
+        "rev": "e755547441a0413942a37692f7bf7fc6315bb7f6",
         "type": "github"
       },
       "original": {
@@ -136,11 +136,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1756555914,
-        "narHash": "sha256-7yoSPIVEuL+3Wzf6e7NHuW3zmruHizRrYhGerjRHTLI=",
+        "lastModified": 1760747435,
+        "narHash": "sha256-wNB/W3x+or4mdNxFPNOH5/WFckNpKgFRZk7OnOsLtm0=",
         "owner": "mitchellh",
         "repo": "zig-overlay",
-        "rev": "d0df3a2fd0f11134409d6d5ea0e510e5e477f7d6",
+        "rev": "d0f239b887b1ac736c0f3dde91bf5bf2ecf3a420",
         "type": "github"
       },
       "original": {

flake.nix

@@ -49,7 +49,7 @@
           targetPkgs =
             pkgs: with pkgs; [
               # Build Tools
-              zigpkgs."0.15.1"
+              zigpkgs."0.15.2"
               zls
               python3
               pkg-config

src/TestHTTPServer.zig

@@ -100,6 +100,11 @@ fn getContentType(file_path: []const u8) []const u8 {
         return "application/json";
     }
 
+    if (std.mem.endsWith(u8, file_path, ".mjs")) {
+        // mjs are ECMAScript modules
+        return "application/json";
+    }
+
     if (std.mem.endsWith(u8, file_path, ".html")) {
         return "text/html";
     }

src/app.zig

@@ -4,7 +4,7 @@ const Allocator = std.mem.Allocator;
 
 const log = @import("log.zig");
 const Http = @import("http/Http.zig");
-const Platform = @import("runtime/js.zig").Platform;
+const Platform = @import("browser/js/Platform.zig");
 
 const Telemetry = @import("telemetry/telemetry.zig").Telemetry;
 const Notification = @import("notification.zig").Notification;
@@ -19,6 +19,7 @@ pub const App = struct {
     telemetry: Telemetry,
     app_dir_path: ?[]const u8,
     notification: *Notification,
+    shutdown: bool = false,
 
     pub const RunMode = enum {
         help,
@@ -36,6 +37,7 @@ pub const App = struct {
         http_connect_timeout_ms: ?u31 = null,
         http_max_host_open: ?u8 = null,
         http_max_concurrent: ?u8 = null,
+        user_agent: [:0]const u8,
     };
 
     pub fn init(allocator: Allocator, config: Config) !*App {
@@ -53,6 +55,7 @@ pub const App = struct {
             .http_proxy = config.http_proxy,
             .tls_verify_host = config.tls_verify_host,
             .proxy_bearer_token = config.proxy_bearer_token,
+            .user_agent = config.user_agent,
         });
         errdefer http.deinit();
 
@@ -80,9 +83,14 @@ pub const App = struct {
     }
 
     pub fn deinit(self: *App) void {
+        if (@atomicRmw(bool, &self.shutdown, .Xchg, true, .monotonic)) {
+            return;
+        }
+
         const allocator = self.allocator;
         if (self.app_dir_path) |app_dir_path| {
             allocator.free(app_dir_path);
+            self.app_dir_path = null;
         }
         self.telemetry.deinit();
         self.notification.deinit();

src/browser/Scheduler.zig

@@ -17,7 +17,6 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
-const log = @import("../log.zig");
 const Allocator = std.mem.Allocator;
 
 const Scheduler = @This();
@@ -38,8 +37,10 @@ pub fn init(allocator: Allocator) Scheduler {
 }
 
 pub fn reset(self: *Scheduler) void {
-    self.high_priority.clearRetainingCapacity();
-    self.low_priority.clearRetainingCapacity();
+    // Our allocator is the page arena, it's been reset. We cannot use
+    // clearAndRetainCapacity, since that space is no longer ours
+    self.high_priority.clearAndFree();
+    self.low_priority.clearAndFree();
 }
 
 const AddOpts = struct {

src/browser/SlotChangeMonitor.zig

@@ -0,0 +1,189 @@
+const std = @import("std");
+
+const log = @import("../log.zig");
+const parser = @import("netsurf.zig");
+const collection = @import("dom/html_collection.zig");
+
+const Page = @import("page.zig").Page;
+
+const SlotChangeMonitor = @This();
+
+page: *Page,
+event_node: parser.EventNode,
+slots_changed: std.ArrayList(*parser.Slot),
+
+// Monitors the document in order to trigger slotchange events.
+pub fn init(page: *Page) !*SlotChangeMonitor {
+    // on the heap, we need a stable address for event_node
+    const self = try page.arena.create(SlotChangeMonitor);
+    self.* = .{
+        .page = page,
+        .slots_changed = .empty,
+        .event_node = .{ .func = mutationCallback },
+    };
+    const root = parser.documentToNode(parser.documentHTMLToDocument(page.window.document));
+
+    _ = try parser.eventTargetAddEventListener(
+        parser.toEventTarget(parser.Node, root),
+        "DOMNodeInserted",
+        &self.event_node,
+        false,
+    );
+
+    _ = try parser.eventTargetAddEventListener(
+        parser.toEventTarget(parser.Node, root),
+        "DOMNodeRemoved",
+        &self.event_node,
+        false,
+    );
+
+    _ = try parser.eventTargetAddEventListener(
+        parser.toEventTarget(parser.Node, root),
+        "DOMAttrModified",
+        &self.event_node,
+        false,
+    );
+
+    return self;
+}
+
+// Given a element, finds its slot, if any.
+pub fn findSlot(element: *parser.Element, page: *const Page) !?*parser.Slot {
+    const target_name = (try parser.elementGetAttribute(element, "slot")) orelse return null;
+    return findNamedSlot(element, target_name, page);
+}
+
+// Given an element and a name, find the slo, if any. This is only useful for
+// MutationEvents where findSlot is unreliable because parser.elementGetAttribute(element, "slot")
+// could return the new or old value.
+fn findNamedSlot(element: *parser.Element, target_name: []const u8, page: *const Page) !?*parser.Slot {
+    // I believe elements need to be added as direct descendents of the host,
+    // so we don't need to go find the host, we just grab the parent.
+    const host = parser.nodeParentNode(@ptrCast(element)) orelse return null;
+    const state = page.getNodeState(host) orelse return null;
+    const shadow_root = state.shadow_root orelse return null;
+
+    // if we're here, we found a host, now find the slot
+    var nodes = collection.HTMLCollectionByTagName(
+        @ptrCast(@alignCast(shadow_root.proto)),
+        "slot",
+        .{ .include_root = false },
+    );
+    for (0..1000) |i| {
+        const n = (try nodes.item(@intCast(i))) orelse return null;
+        const slot_name = (try parser.elementGetAttribute(@ptrCast(n), "name")) orelse "";
+        if (std.mem.eql(u8, target_name, slot_name)) {
+            return @ptrCast(n);
+        }
+    }
+    return null;
+}
+
+// Event callback from the mutation event, signaling either the addition of
+// a node, removal of a node, or a change in attribute
+fn mutationCallback(en: *parser.EventNode, event: *parser.Event) void {
+    const mutation_event = parser.eventToMutationEvent(event);
+    const self: *SlotChangeMonitor = @fieldParentPtr("event_node", en);
+    self._mutationCallback(mutation_event) catch |err| {
+        log.err(.web_api, "slot change callback", .{ .err = err });
+    };
+}
+
+fn _mutationCallback(self: *SlotChangeMonitor, event: *parser.MutationEvent) !void {
+    const event_type = parser.eventType(@ptrCast(event));
+    if (std.mem.eql(u8, event_type, "DOMNodeInserted")) {
+        const event_target = parser.eventTarget(@ptrCast(event)) orelse return;
+        return self.nodeAddedOrRemoved(@ptrCast(event_target));
+    }
+
+    if (std.mem.eql(u8, event_type, "DOMNodeRemoved")) {
+        const event_target = parser.eventTarget(@ptrCast(event)) orelse return;
+        return self.nodeAddedOrRemoved(@ptrCast(event_target));
+    }
+
+    if (std.mem.eql(u8, event_type, "DOMAttrModified")) {
+        const attribute_name = try parser.mutationEventAttributeName(event);
+        if (std.mem.eql(u8, attribute_name, "slot") == false) {
+            return;
+        }
+
+        const new_value = parser.mutationEventNewValue(event);
+        const prev_value = parser.mutationEventPrevValue(event);
+        const event_target = parser.eventTarget(@ptrCast(event)) orelse return;
+        return self.nodeAttributeChanged(@ptrCast(event_target), new_value, prev_value);
+    }
+}
+
+// A node was removed or added. If it's an element, and if it has a slot attribute
+// then we'll dispatch a slotchange event.
+fn nodeAddedOrRemoved(self: *SlotChangeMonitor, node: *parser.Node) !void {
+    if (parser.nodeType(node) != .element) {
+        return;
+    }
+    const el: *parser.Element = @ptrCast(node);
+    if (try findSlot(el, self.page)) |slot| {
+        return self.scheduleSlotChange(slot);
+    }
+}
+
+// An attribute was modified. If the attribute is "slot", then we'll trigger 1
+// slotchange for the old slot (if there was one) and 1 slotchange for the new
+// one (if there is one)
+fn nodeAttributeChanged(self: *SlotChangeMonitor, node: *parser.Node, new_value: ?[]const u8, prev_value: ?[]const u8) !void {
+    if (parser.nodeType(node) != .element) {
+        return;
+    }
+
+    const el: *parser.Element = @ptrCast(node);
+    if (try findNamedSlot(el, prev_value orelse "", self.page)) |slot| {
+        try self.scheduleSlotChange(slot);
+    }
+
+    if (try findNamedSlot(el, new_value orelse "", self.page)) |slot| {
+        try self.scheduleSlotChange(slot);
+    }
+}
+
+// OK. Our MutationEvent is not a MutationObserver - it's an older, deprecated
+// API. It gets dispatched in the middle of the change. While I'm sure it has
+// some rules, from our point of view, it fires too early. DOMAttrModified fires
+// before the attribute is actually updated and DOMNodeRemoved before the node
+// is actually removed. This is a problem if the callback will call
+// `slot.assignedNodes`, since that won't return the new state.
+// So, we use the page schedule to schedule the dispatching of the slotchange
+// event.
+fn scheduleSlotChange(self: *SlotChangeMonitor, slot: *parser.Slot) !void {
+    for (self.slots_changed.items) |changed| {
+        if (slot == changed) {
+            return;
+        }
+    }
+
+    try self.slots_changed.append(self.page.arena, slot);
+    if (self.slots_changed.items.len == 1) {
+        // first item added, schedule the callback
+        try self.page.scheduler.add(self, scheduleCallback, 0, .{ .name = "slot change" });
+    }
+}
+
+// Callback from the schedule. Time to dispatch the slotchange event
+fn scheduleCallback(ctx: *anyopaque) ?u32 {
+    var self: *SlotChangeMonitor = @ptrCast(@alignCast(ctx));
+    self._scheduleCallback() catch |err| {
+        log.err(.app, "slot change schedule", .{ .err = err });
+    };
+    return null;
+}
+
+fn _scheduleCallback(self: *SlotChangeMonitor) !void {
+    for (self.slots_changed.items) |slot| {
+        const event = try parser.eventCreate();
+        defer parser.eventDestroy(event);
+        try parser.eventInit(event, "slotchange", .{});
+        _ = try parser.eventTargetDispatchEvent(
+            parser.toEventTarget(parser.Element, @ptrCast(@alignCast(slot))),
+            event,
+        );
+    }
+    self.slots_changed.clearRetainingCapacity();
+}

src/browser/State.zig

@@ -26,17 +26,16 @@
 // this quickly proved necessary, since different fields are needed on the same
 // data at different levels of the prototype chain. This isn't memory efficient.
 
-const Env = @import("env.zig").Env;
+const js = @import("js/js.zig");
 const parser = @import("netsurf.zig");
 const DataSet = @import("html/DataSet.zig");
 const ShadowRoot = @import("dom/shadow_root.zig").ShadowRoot;
 const StyleSheet = @import("cssom/StyleSheet.zig");
-const CSSStyleSheet = @import("cssom/CSSStyleSheet.zig");
 const CSSStyleDeclaration = @import("cssom/CSSStyleDeclaration.zig");
 
 // for HTMLScript (but probably needs to be added to more)
-onload: ?Env.Function = null,
-onerror: ?Env.Function = null,
+onload: ?js.Function = null,
+onerror: ?js.Function = null,
 
 // for HTMLElement
 style: CSSStyleDeclaration = .empty,
@@ -54,7 +53,7 @@ style_sheet: ?*StyleSheet = null,
 
 // for dom/document
 active_element: ?*parser.Element = null,
-adopted_style_sheets: ?Env.JsObject = null,
+adopted_style_sheets: ?js.Object = null,
 
 // for HTMLSelectElement
 // By default, if no option is explicitly selected, the first option should

src/browser/browser.zig

@@ -21,8 +21,8 @@ const std = @import("std");
 const Allocator = std.mem.Allocator;
 const ArenaAllocator = std.heap.ArenaAllocator;
 
+const js = @import("js/js.zig");
 const State = @import("State.zig");
-const Env = @import("env.zig").Env;
 const App = @import("../app.zig").App;
 const Session = @import("session.zig").Session;
 const Notification = @import("../notification.zig").Notification;
@@ -34,11 +34,12 @@ const HttpClient = @import("../http/Client.zig");
 // You can create multiple browser instances.
 // A browser contains only one session.
 pub const Browser = struct {
-    env: *Env,
+    env: *js.Env,
     app: *App,
     session: ?Session,
     allocator: Allocator,
     http_client: *HttpClient,
+    call_arena: ArenaAllocator,
     page_arena: ArenaAllocator,
     session_arena: ArenaAllocator,
     transfer_arena: ArenaAllocator,
@@ -48,7 +49,7 @@ pub const Browser = struct {
     pub fn init(app: *App) !Browser {
         const allocator = app.allocator;
 
-        const env = try Env.init(allocator, &app.platform, .{});
+        const env = try js.Env.init(allocator, &app.platform, .{});
         errdefer env.deinit();
 
         const notification = try Notification.init(allocator, app.notification);
@@ -63,6 +64,7 @@ pub const Browser = struct {
             .allocator = allocator,
             .notification = notification,
             .http_client = app.http.client,
+            .call_arena = ArenaAllocator.init(allocator),
             .page_arena = ArenaAllocator.init(allocator),
             .session_arena = ArenaAllocator.init(allocator),
             .transfer_arena = ArenaAllocator.init(allocator),
@@ -73,6 +75,7 @@ pub const Browser = struct {
     pub fn deinit(self: *Browser) void {
         self.closeSession();
         self.env.deinit();
+        self.call_arena.deinit();
         self.page_arena.deinit();
         self.session_arena.deinit();
         self.transfer_arena.deinit();

src/browser/canvas/CanvasRenderingContext2D.zig

@@ -0,0 +1,58 @@
+// Copyright (C) 2023-2025  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+
+const color = @import("../cssom/color.zig");
+const Page = @import("../page.zig").Page;
+
+/// This class doesn't implement a `constructor`.
+/// It can be obtained with a call to `HTMLCanvasElement#getContext`.
+/// https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D
+const CanvasRenderingContext2D = @This();
+/// Fill color.
+/// TODO: Add support for `CanvasGradient` and `CanvasPattern`.
+fill_style: color.RGBA = color.RGBA.Named.black,
+
+pub fn _fillRect(
+    self: *const CanvasRenderingContext2D,
+    x: f64,
+    y: f64,
+    width: f64,
+    height: f64,
+) void {
+    _ = self;
+    _ = x;
+    _ = y;
+    _ = width;
+    _ = height;
+}
+
+pub fn get_fillStyle(self: *const CanvasRenderingContext2D, page: *Page) ![]const u8 {
+    var w = std.Io.Writer.Allocating.init(page.call_arena);
+    try self.fill_style.format(&w.writer);
+    return w.written();
+}
+
+pub fn set_fillStyle(
+    self: *CanvasRenderingContext2D,
+    value: []const u8,
+) !void {
+    // Prefer the same fill_style if fails.
+    self.fill_style = color.RGBA.parse(value) catch self.fill_style;
+}

src/browser/canvas/WebGLRenderingContext.zig

@@ -0,0 +1,145 @@
+// Copyright (C) 2023-2025  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+
+const WebGLRenderingContext = @This();
+_: u8 = 0,
+
+/// On Chrome and Safari, a call to `getSupportedExtensions` returns total of 39.
+/// The reference for it lists lesser number of extensions:
+/// https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/Using_Extensions#extension_list
+pub const Extension = union(enum) {
+    ANGLE_instanced_arrays: void,
+    EXT_blend_minmax: void,
+    EXT_clip_control: void,
+    EXT_color_buffer_half_float: void,
+    EXT_depth_clamp: void,
+    EXT_disjoint_timer_query: void,
+    EXT_float_blend: void,
+    EXT_frag_depth: void,
+    EXT_polygon_offset_clamp: void,
+    EXT_shader_texture_lod: void,
+    EXT_texture_compression_bptc: void,
+    EXT_texture_compression_rgtc: void,
+    EXT_texture_filter_anisotropic: void,
+    EXT_texture_mirror_clamp_to_edge: void,
+    EXT_sRGB: void,
+    KHR_parallel_shader_compile: void,
+    OES_element_index_uint: void,
+    OES_fbo_render_mipmap: void,
+    OES_standard_derivatives: void,
+    OES_texture_float: void,
+    OES_texture_float_linear: void,
+    OES_texture_half_float: void,
+    OES_texture_half_float_linear: void,
+    OES_vertex_array_object: void,
+    WEBGL_blend_func_extended: void,
+    WEBGL_color_buffer_float: void,
+    WEBGL_compressed_texture_astc: void,
+    WEBGL_compressed_texture_etc: void,
+    WEBGL_compressed_texture_etc1: void,
+    WEBGL_compressed_texture_pvrtc: void,
+    WEBGL_compressed_texture_s3tc: void,
+    WEBGL_compressed_texture_s3tc_srgb: void,
+    WEBGL_debug_renderer_info: Type.WEBGL_debug_renderer_info,
+    WEBGL_debug_shaders: void,
+    WEBGL_depth_texture: void,
+    WEBGL_draw_buffers: void,
+    WEBGL_lose_context: Type.WEBGL_lose_context,
+    WEBGL_multi_draw: void,
+    WEBGL_polygon_mode: void,
+
+    /// Reified enum type from the fields of this union.
+    const Kind = blk: {
+        const info = @typeInfo(Extension).@"union";
+        const fields = info.fields;
+        var items: [fields.len]std.builtin.Type.EnumField = undefined;
+        for (fields, 0..) |field, i| {
+            items[i] = .{ .name = field.name, .value = i };
+        }
+
+        break :blk @Type(.{
+            .@"enum" = .{
+                .tag_type = std.math.IntFittingRange(0, if (fields.len == 0) 0 else fields.len - 1),
+                .fields = &items,
+                .decls = &.{},
+                .is_exhaustive = true,
+            },
+        });
+    };
+
+    /// Returns the `Extension.Kind` by its name.
+    fn find(name: []const u8) ?Kind {
+        // Just to make you really sad, this function has to be case-insensitive.
+        // So here we copy what's being done in `std.meta.stringToEnum` but replace
+        // the comparison function.
+        const kvs = comptime build_kvs: {
+            const T = Extension.Kind;
+            const EnumKV = struct { []const u8, T };
+            var kvs_array: [@typeInfo(T).@"enum".fields.len]EnumKV = undefined;
+            for (@typeInfo(T).@"enum".fields, 0..) |enumField, i| {
+                kvs_array[i] = .{ enumField.name, @field(T, enumField.name) };
+            }
+            break :build_kvs kvs_array[0..];
+        };
+        const Map = std.StaticStringMapWithEql(Extension.Kind, std.static_string_map.eqlAsciiIgnoreCase);
+        const map = Map.initComptime(kvs);
+        return map.get(name);
+    }
+
+    /// Extension types.
+    pub const Type = struct {
+        pub const WEBGL_debug_renderer_info = struct {
+            pub const UNMASKED_VENDOR_WEBGL: u64 = 0x9245;
+            pub const UNMASKED_RENDERER_WEBGL: u64 = 0x9246;
+
+            pub fn get_UNMASKED_VENDOR_WEBGL() u64 {
+                return UNMASKED_VENDOR_WEBGL;
+            }
+
+            pub fn get_UNMASKED_RENDERER_WEBGL() u64 {
+                return UNMASKED_RENDERER_WEBGL;
+            }
+        };
+
+        pub const WEBGL_lose_context = struct {
+            _: u8 = 0,
+            pub fn _loseContext(_: *const WEBGL_lose_context) void {}
+            pub fn _restoreContext(_: *const WEBGL_lose_context) void {}
+        };
+    };
+};
+
+/// Enables a WebGL extension.
+pub fn _getExtension(self: *const WebGLRenderingContext, name: []const u8) ?Extension {
+    _ = self;
+
+    const tag = Extension.find(name) orelse return null;
+
+    return switch (tag) {
+        .WEBGL_debug_renderer_info => @unionInit(Extension, "WEBGL_debug_renderer_info", .{}),
+        .WEBGL_lose_context => @unionInit(Extension, "WEBGL_lose_context", .{}),
+        inline else => |comptime_enum| @unionInit(Extension, @tagName(comptime_enum), {}),
+    };
+}
+
+/// Returns a list of all the supported WebGL extensions.
+pub fn _getSupportedExtensions(_: *const WebGLRenderingContext) []const []const u8 {
+    return std.meta.fieldNames(Extension.Kind);
+}

src/browser/canvas/root.zig

@@ -0,0 +1,13 @@
+//! Canvas API.
+//! https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API
+
+const CanvasRenderingContext2D = @import("CanvasRenderingContext2D.zig");
+const WebGLRenderingContext = @import("WebGLRenderingContext.zig");
+const Extension = WebGLRenderingContext.Extension;
+
+pub const Interfaces = .{
+    CanvasRenderingContext2D,
+    WebGLRenderingContext,
+    Extension.Type.WEBGL_debug_renderer_info,
+    Extension.Type.WEBGL_lose_context,
+};

src/browser/console/console.zig

@@ -20,48 +20,47 @@ const std = @import("std");
 const builtin = @import("builtin");
 const log = @import("../../log.zig");
 
-const Allocator = std.mem.Allocator;
+const js = @import("../js/js.zig");
 const Page = @import("../page.zig").Page;
-const JsObject = @import("../env.zig").Env.JsObject;
 
 pub const Console = struct {
     // TODO: configurable writer
     timers: std.StringHashMapUnmanaged(u32) = .{},
     counts: std.StringHashMapUnmanaged(u32) = .{},
 
-    pub fn _lp(values: []JsObject, page: *Page) !void {
+    pub fn _lp(values: []js.Object, page: *Page) !void {
         if (values.len == 0) {
             return;
         }
         log.fatal(.console, "lightpanda", .{ .args = try serializeValues(values, page) });
     }
 
-    pub fn _log(values: []JsObject, page: *Page) !void {
+    pub fn _log(values: []js.Object, page: *Page) !void {
         if (values.len == 0) {
             return;
         }
         log.info(.console, "info", .{ .args = try serializeValues(values, page) });
     }
 
-    pub fn _info(values: []JsObject, page: *Page) !void {
+    pub fn _info(values: []js.Object, page: *Page) !void {
         return _log(values, page);
     }
 
-    pub fn _debug(values: []JsObject, page: *Page) !void {
+    pub fn _debug(values: []js.Object, page: *Page) !void {
         if (values.len == 0) {
             return;
         }
         log.debug(.console, "debug", .{ .args = try serializeValues(values, page) });
     }
 
-    pub fn _warn(values: []JsObject, page: *Page) !void {
+    pub fn _warn(values: []js.Object, page: *Page) !void {
         if (values.len == 0) {
             return;
         }
         log.warn(.console, "warn", .{ .args = try serializeValues(values, page) });
     }
 
-    pub fn _error(values: []JsObject, page: *Page) !void {
+    pub fn _error(values: []js.Object, page: *Page) !void {
         if (values.len == 0) {
             return;
         }
@@ -72,6 +71,16 @@ pub const Console = struct {
         });
     }
 
+    pub fn _trace(values: []js.Object, page: *Page) !void {
+        if (values.len == 0) {
+            return;
+        }
+        log.debug(.console, "debug", .{
+            .stack = page.js.stackTrace() catch "???",
+            .args = try serializeValues(values, page),
+        });
+    }
+
     pub fn _clear() void {}
 
     pub fn _count(self: *Console, label_: ?[]const u8, page: *Page) !void {
@@ -133,7 +142,7 @@ pub const Console = struct {
         log.warn(.console, "timer stop", .{ .label = label, .elapsed = elapsed - kv.value });
     }
 
-    pub fn _assert(assertion: JsObject, values: []JsObject, page: *Page) !void {
+    pub fn _assert(assertion: js.Object, values: []js.Object, page: *Page) !void {
         if (assertion.isTruthy()) {
             return;
         }
@@ -144,7 +153,7 @@ pub const Console = struct {
         log.info(.console, "assertion failed", .{ .values = serialized_values });
     }
 
-    fn serializeValues(values: []JsObject, page: *Page) ![]const u8 {
+    fn serializeValues(values: []js.Object, page: *Page) ![]const u8 {
         if (values.len == 0) {
             return "";
         }

src/browser/crypto/crypto.zig

@@ -17,14 +17,14 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
-const Env = @import("../env.zig").Env;
+const js = @import("../js/js.zig");
 const uuidv4 = @import("../../id.zig").uuidv4;
 
 // https://w3c.github.io/webcrypto/#crypto-interface
 pub const Crypto = struct {
     _not_empty: bool = true,
 
-    pub fn _getRandomValues(_: *const Crypto, js_obj: Env.JsObject) !Env.JsObject {
+    pub fn _getRandomValues(_: *const Crypto, js_obj: js.Object) !js.Object {
         var into = try js_obj.toZig(Crypto, "getRandomValues", RandomValues);
         const buf = into.asBuffer();
         if (buf.len > 65_536) {

src/browser/css/css.zig

@@ -46,17 +46,15 @@ pub fn parse(alloc: std.mem.Allocator, s: []const u8, opts: parser.ParseOptions)
 // matchFirst call m.match with the first node that matches the selector s, from the
 // descendants of n and returns true. If none matches, it returns false.
 pub fn matchFirst(s: *const Selector, node: anytype, m: anytype) !bool {
-    var c = try node.firstChild();
-    while (true) {
-        if (c == null) break;
-
-        if (try s.match(c.?)) {
-            try m.match(c.?);
+    var child = node.firstChild();
+    while (child) |c| {
+        if (try s.match(c)) {
+            try m.match(c);
             return true;
         }
 
-        if (try matchFirst(s, c.?, m)) return true;
-        c = try c.?.nextSibling();
+        if (try matchFirst(s, c, m)) return true;
+        child = c.nextSibling();
     }
     return false;
 }
@@ -64,13 +62,11 @@ pub fn matchFirst(s: *const Selector, node: anytype, m: anytype) !bool {
 // matchAll call m.match with the all the nodes that matches the selector s, from the
 // descendants of n.
 pub fn matchAll(s: *const Selector, node: anytype, m: anytype) !void {
-    var c = try node.firstChild();
-    while (true) {
-        if (c == null) break;
-
-        if (try s.match(c.?)) try m.match(c.?);
-        try matchAll(s, c.?, m);
-        c = try c.?.nextSibling();
+    var child = node.firstChild();
+    while (child) |c| {
+        if (try s.match(c)) try m.match(c);
+        try matchAll(s, c, m);
+        child = c.nextSibling();
     }
 }
 

src/browser/css/libdom.zig

@@ -26,71 +26,67 @@ const Allocator = std.mem.Allocator;
 pub const Node = struct {
     node: *parser.Node,
 
-    pub fn firstChild(n: Node) !?Node {
-        const c = try parser.nodeFirstChild(n.node);
+    pub fn firstChild(n: Node) ?Node {
+        const c = parser.nodeFirstChild(n.node);
         if (c) |cc| return .{ .node = cc };
 
         return null;
     }
 
-    pub fn lastChild(n: Node) !?Node {
-        const c = try parser.nodeLastChild(n.node);
+    pub fn lastChild(n: Node) ?Node {
+        const c = parser.nodeLastChild(n.node);
         if (c) |cc| return .{ .node = cc };
 
         return null;
     }
 
-    pub fn nextSibling(n: Node) !?Node {
-        const c = try parser.nodeNextSibling(n.node);
+    pub fn nextSibling(n: Node) ?Node {
+        const c = parser.nodeNextSibling(n.node);
         if (c) |cc| return .{ .node = cc };
 
         return null;
     }
 
-    pub fn prevSibling(n: Node) !?Node {
-        const c = try parser.nodePreviousSibling(n.node);
+    pub fn prevSibling(n: Node) ?Node {
+        const c = parser.nodePreviousSibling(n.node);
         if (c) |cc| return .{ .node = cc };
 
         return null;
     }
 
-    pub fn parent(n: Node) !?Node {
-        const c = try parser.nodeParentNode(n.node);
+    pub fn parent(n: Node) ?Node {
+        const c = parser.nodeParentNode(n.node);
         if (c) |cc| return .{ .node = cc };
 
         return null;
     }
 
     pub fn isElement(n: Node) bool {
-        const t = parser.nodeType(n.node) catch return false;
-        return t == .element;
+        return parser.nodeType(n.node) == .element;
     }
 
     pub fn isDocument(n: Node) bool {
-        const t = parser.nodeType(n.node) catch return false;
-        return t == .document;
+        return parser.nodeType(n.node) == .document;
     }
 
     pub fn isComment(n: Node) bool {
-        const t = parser.nodeType(n.node) catch return false;
-        return t == .comment;
+        return parser.nodeType(n.node) == .comment;
     }
 
     pub fn isText(n: Node) bool {
-        const t = parser.nodeType(n.node) catch return false;
-        return t == .text;
+        return parser.nodeType(n.node) == .text;
     }
 
-    pub fn text(n: Node) !?[]const u8 {
-        const data = try parser.nodeTextContent(n.node);
+    pub fn text(n: Node) ?[]const u8 {
+        const data = parser.nodeTextContent(n.node);
         if (data == null) return null;
         if (data.?.len == 0) return null;
 
         return std.mem.trim(u8, data.?, &std.ascii.whitespace);
     }
 
-    pub fn isEmptyText(n: Node) !bool {
-        const data = try parser.nodeTextContent(n.node);
+    pub fn isEmptyText(n: Node) bool {
+        const data = parser.nodeTextContent(n.node);
         if (data == null) return true;
         if (data.?.len == 0) return true;
 
@@ -98,7 +94,7 @@ pub const Node = struct {
     }
 
     pub fn tag(n: Node) ![]const u8 {
-        return try parser.nodeName(n.node);
+        return parser.nodeName(n.node);
     }
 
     pub fn attr(n: Node, key: []const u8) !?[]const u8 {
@@ -140,7 +136,7 @@ const MatcherTest = struct {
 test "Browser.CSS.Libdom: matchFirst" {
     const alloc = std.testing.allocator;
 
-    try parser.init();
+    parser.init();
     defer parser.deinit();
 
     var matcher = MatcherTest.init(alloc);
@@ -285,7 +281,7 @@ test "Browser.CSS.Libdom: matchFirst" {
 test "Browser.CSS.Libdom: matchAll" {
     const alloc = std.testing.allocator;
 
-    try parser.init();
+    parser.init();
     defer parser.deinit();
 
     var matcher = MatcherTest.init(alloc);

src/browser/css/parser.zig

@@ -821,7 +821,8 @@ pub const Parser = struct {
 // nameStart returns whether c can be the first character of an identifier
 // (not counting an initial hyphen, or an escape sequence).
 fn nameStart(c: u8) bool {
-    return 'a' <= c and c <= 'z' or 'A' <= c and c <= 'Z' or c == '_' or c > 127;
+    return 'a' <= c and c <= 'z' or 'A' <= c and c <= 'Z' or c == '_' or c > 127 or
+        '0' <= c and c <= '9';
 }
 
 // nameChar returns whether c can be a character within an identifier
@@ -890,7 +891,7 @@ test "parser.parseIdentifier" {
         err: bool = false,
     }{
         .{ .s = "x", .exp = "x" },
-        .{ .s = "96", .exp = "", .err = true },
+        .{ .s = "96", .exp = "96", .err = false },
         .{ .s = "-x", .exp = "-x" },
         .{ .s = "r\\e9 sumé", .exp = "résumé" },
         .{ .s = "r\\0000e9 sumé", .exp = "résumé" },
@@ -975,6 +976,7 @@ test "parser.parse" {
         .{ .s = ":root", .exp = .{ .pseudo_class = .root } },
         .{ .s = ".\\:bar", .exp = .{ .class = ":bar" } },
         .{ .s = ".foo\\:bar", .exp = .{ .class = "foo:bar" } },
+        .{ .s = "[class=75c0fa18a94b9e3a6b8e14d6cbe688a27f5da10a]", .exp = .{ .attribute = .{ .key = "class", .val = "75c0fa18a94b9e3a6b8e14d6cbe688a27f5da10a", .op = .eql } } },
     };
 
     for (testcases) |tc| {

src/browser/css/selector.zig

@@ -334,41 +334,39 @@ pub const Selector = union(enum) {
                         if (!try v.second.match(n)) return false;
 
                         // The first must match a ascendent.
-                        var p = try n.parent();
-                        while (p != null) {
-                            if (try v.first.match(p.?)) {
+                        var parent = n.parent();
+                        while (parent) |p| {
+                            if (try v.first.match(p)) {
                                 return true;
                             }
-                            p = try p.?.parent();
+                            parent = p.parent();
                         }
 
                         return false;
                     },
                     .child => {
-                        const p = try n.parent();
-                        if (p == null) return false;
-
-                        return try v.second.match(n) and try v.first.match(p.?);
+                        const p = n.parent() orelse return false;
+                        return try v.second.match(n) and try v.first.match(p);
                     },
                     .next_sibling => {
                         if (!try v.second.match(n)) return false;
-                        var c = try n.prevSibling();
-                        while (c != null) {
-                            if (c.?.isText() or c.?.isComment()) {
-                                c = try c.?.prevSibling();
+                        var child = n.prevSibling();
+                        while (child) |c| {
+                            if (c.isText() or c.isComment()) {
+                                child = c.prevSibling();
                                 continue;
                             }
-                            return try v.first.match(c.?);
+                            return try v.first.match(c);
                         }
                         return false;
                     },
                     .subsequent_sibling => {
                         if (!try v.second.match(n)) return false;
 
-                        var c = try n.prevSibling();
-                        while (c != null) {
-                            if (try v.first.match(c.?)) return true;
-                            c = try c.?.prevSibling();
+                        var child = n.prevSibling();
+                        while (child) |c| {
+                            if (try v.first.match(c)) return true;
+                            child = c.prevSibling();
                         }
                         return false;
                     },
@@ -438,10 +436,10 @@ pub const Selector = union(enum) {
                 // Only containsOwn is implemented.
                 if (v.own == false) return Error.UnsupportedContainsPseudoClass;
 
-                var c = try n.firstChild();
-                while (c != null) {
-                    if (c.?.isText()) {
-                        const text = try c.?.text();
+                var child = n.firstChild();
+                while (child) |c| {
+                    if (c.isText()) {
+                        const text = c.text();
                         if (text) |_text| {
                             if (contains(_text, v.val, false)) { // we are case sensitive. Is this correct behavior?
                                 return true;
@@ -449,7 +447,7 @@ pub const Selector = union(enum) {
                         }
                     }
 
-                    c = try c.?.nextSibling();
+                    child = c.nextSibling();
                 }
                 return false;
             },
@@ -477,16 +475,16 @@ pub const Selector = union(enum) {
                     .empty => {
                         if (!n.isElement()) return false;
 
-                        var c = try n.firstChild();
-                        while (c != null) {
-                            if (c.?.isElement()) return false;
+                        var child = n.firstChild();
+                        while (child) |c| {
+                            if (c.isElement()) return false;
 
-                            if (c.?.isText()) {
-                                if (try c.?.isEmptyText()) continue;
+                            if (c.isText()) {
+                                if (c.isEmptyText()) continue;
                                 return false;
                             }
 
-                            c = try c.?.nextSibling();
+                            child = c.nextSibling();
                         }
 
                         return true;
@@ -494,7 +492,7 @@ pub const Selector = union(enum) {
                     .root => {
                         if (!n.isElement()) return false;
 
-                        const p = try n.parent();
+                        const p = n.parent();
                         return (p != null and p.?.isDocument());
                     },
                     .link => {
@@ -564,7 +562,7 @@ pub const Selector = union(enum) {
 
                         const ntag = try n.tag();
 
-                        if (std.ascii.eqlIgnoreCase("intput", ntag)) {
+                        if (std.ascii.eqlIgnoreCase("input", ntag)) {
                             const ntype = try n.attr("type");
                             if (ntype == null) return false;
 
@@ -609,24 +607,23 @@ pub const Selector = union(enum) {
     }
 
     fn hasLegendInPreviousSiblings(n: anytype) anyerror!bool {
-        var c = try n.prevSibling();
-        while (c != null) {
-            const ctag = try c.?.tag();
+        var child = n.prevSibling();
+        while (child) |c| {
+            const ctag = try c.tag();
             if (std.ascii.eqlIgnoreCase("legend", ctag)) return true;
-            c = try c.?.prevSibling();
+            child = c.prevSibling();
         }
         return false;
     }
 
     fn inDisabledFieldset(n: anytype) anyerror!bool {
-        const p = try n.parent();
-        if (p == null) return false;
+        const p = n.parent() orelse return false;
 
         const ntag = try n.tag();
-        const ptag = try p.?.tag();
+        const ptag = try p.tag();
 
         if (std.ascii.eqlIgnoreCase("fieldset", ptag) and
-            try p.?.attr("disabled") != null and
+            try p.attr("disabled") != null and
             (!std.ascii.eqlIgnoreCase("legend", ntag) or try hasLegendInPreviousSiblings(n)))
         {
             return true;
@@ -642,7 +639,7 @@ pub const Selector = union(enum) {
         // ```
         // https://github.com/andybalholm/cascadia/blob/master/pseudo_classes.go#L434
 
-        return try inDisabledFieldset(p.?);
+        return try inDisabledFieldset(p);
     }
 
     fn langMatch(lang: []const u8, n: anytype) anyerror!bool {
@@ -656,10 +653,8 @@ pub const Selector = union(enum) {
         }
 
         // if the tag doesn't match, try the parent.
-        const p = try n.parent();
-        if (p == null) return false;
-
-        return langMatch(lang, p.?);
+        const p = n.parent() orelse return false;
+        return langMatch(lang, p);
     }
 
     // onlyChildMatch implements :only-child
@@ -667,25 +662,24 @@ pub const Selector = union(enum) {
     fn onlyChildMatch(of_type: bool, n: anytype) anyerror!bool {
         if (!n.isElement()) return false;
 
-        const p = try n.parent();
-        if (p == null) return false;
+        const p = n.parent() orelse return false;
 
         const ntag = try n.tag();
 
         var count: usize = 0;
-        var c = try p.?.firstChild();
+        var child = p.firstChild();
         // loop hover all n siblings.
-        while (c != null) {
+        while (child) |c| {
             // ignore non elements or others tags if of-type is true.
-            if (!c.?.isElement() or (of_type and !std.mem.eql(u8, ntag, try c.?.tag()))) {
-                c = try c.?.nextSibling();
+            if (!c.isElement() or (of_type and !std.mem.eql(u8, ntag, try c.tag()))) {
+                child = c.nextSibling();
                 continue;
             }
 
             count += 1;
             if (count > 1) return false;
 
-            c = try c.?.nextSibling();
+            child = c.nextSibling();
         }
 
         return count == 1;
@@ -696,27 +690,25 @@ pub const Selector = union(enum) {
     fn simpleNthLastChildMatch(b: isize, of_type: bool, n: anytype) anyerror!bool {
         if (!n.isElement()) return false;
 
-        const p = try n.parent();
-        if (p == null) return false;
-
+        const p = n.parent() orelse return false;
         const ntag = try n.tag();
 
         var count: isize = 0;
-        var c = try p.?.lastChild();
+        var child = p.lastChild();
         // loop hover all n siblings.
-        while (c != null) {
+        while (child) |c| {
             // ignore non elements or others tags if of-type is true.
-            if (!c.?.isElement() or (of_type and !std.mem.eql(u8, ntag, try c.?.tag()))) {
-                c = try c.?.prevSibling();
+            if (!c.isElement() or (of_type and !std.mem.eql(u8, ntag, try c.tag()))) {
+                child = c.prevSibling();
                 continue;
             }
 
             count += 1;
 
-            if (n.eql(c.?)) return count == b;
+            if (n.eql(c)) return count == b;
             if (count >= b) return false;
 
-            c = try c.?.prevSibling();
+            child = c.prevSibling();
         }
 
         return false;
@@ -727,27 +719,25 @@ pub const Selector = union(enum) {
     fn simpleNthChildMatch(b: isize, of_type: bool, n: anytype) anyerror!bool {
         if (!n.isElement()) return false;
 
-        const p = try n.parent();
-        if (p == null) return false;
-
+        const p = n.parent() orelse return false;
         const ntag = try n.tag();
 
         var count: isize = 0;
-        var c = try p.?.firstChild();
+        var child = p.firstChild();
         // loop hover all n siblings.
-        while (c != null) {
+        while (child) |c| {
             // ignore non elements or others tags if of-type is true.
-            if (!c.?.isElement() or (of_type and !std.mem.eql(u8, ntag, try c.?.tag()))) {
-                c = try c.?.nextSibling();
+            if (!c.isElement() or (of_type and !std.mem.eql(u8, ntag, try c.tag()))) {
+                child = c.nextSibling();
                 continue;
             }
 
             count += 1;
 
-            if (n.eql(c.?)) return count == b;
+            if (n.eql(c)) return count == b;
             if (count >= b) return false;
 
-            c = try c.?.nextSibling();
+            child = c.nextSibling();
         }
 
         return false;
@@ -759,29 +749,27 @@ pub const Selector = union(enum) {
     fn nthChildMatch(a: isize, b: isize, last: bool, of_type: bool, n: anytype) anyerror!bool {
         if (!n.isElement()) return false;
 
-        const p = try n.parent();
-        if (p == null) return false;
-
+        const p = n.parent() orelse return false;
         const ntag = try n.tag();
 
         var i: isize = -1;
         var count: isize = 0;
-        var c = try p.?.firstChild();
+        var child = p.firstChild();
         // loop hover all n siblings.
-        while (c != null) {
+        while (child) |c| {
             // ignore non elements or others tags if of-type is true.
-            if (!c.?.isElement() or (of_type and !std.mem.eql(u8, ntag, try c.?.tag()))) {
-                c = try c.?.nextSibling();
+            if (!c.isElement() or (of_type and !std.mem.eql(u8, ntag, try c.tag()))) {
+                child = c.nextSibling();
                 continue;
             }
             count += 1;
 
-            if (n.eql(c.?)) {
+            if (n.eql(c)) {
                 i = count;
                 if (!last) break;
             }
 
-            c = try c.?.nextSibling();
+            child = c.nextSibling();
         }
 
         if (i == -1) return false;
@@ -794,21 +782,21 @@ pub const Selector = union(enum) {
     }
 
     fn hasDescendantMatch(s: *const Selector, n: anytype) anyerror!bool {
-        var c = try n.firstChild();
-        while (c != null) {
-            if (try s.match(c.?)) return true;
-            if (c.?.isElement() and try hasDescendantMatch(s, c.?)) return true;
-            c = try c.?.nextSibling();
+        var child = n.firstChild();
+        while (child) |c| {
+            if (try s.match(c)) return true;
+            if (c.isElement() and try hasDescendantMatch(s, c)) return true;
+            child = c.nextSibling();
         }
 
         return false;
     }
 
     fn hasChildMatch(s: *const Selector, n: anytype) anyerror!bool {
-        var c = try n.firstChild();
-        while (c != null) {
-            if (try s.match(c.?)) return true;
-            c = try c.?.nextSibling();
+        var child = n.firstChild();
+        while (child) |c| {
+            if (try s.match(c)) return true;
+            child = c.nextSibling();
         }
 
         return false;
@@ -859,23 +847,23 @@ pub const NodeTest = struct {
     name: []const u8 = "",
     att: ?[]const u8 = null,
 
-    pub fn firstChild(n: *const NodeTest) !?*const NodeTest {
+    pub fn firstChild(n: *const NodeTest) ?*const NodeTest {
         return n.child;
     }
 
-    pub fn lastChild(n: *const NodeTest) !?*const NodeTest {
+    pub fn lastChild(n: *const NodeTest) ?*const NodeTest {
         return n.last;
     }
 
-    pub fn nextSibling(n: *const NodeTest) !?*const NodeTest {
+    pub fn nextSibling(n: *const NodeTest) ?*const NodeTest {
         return n.sibling;
     }
 
-    pub fn prevSibling(n: *const NodeTest) !?*const NodeTest {
+    pub fn prevSibling(n: *const NodeTest) ?*const NodeTest {
         return n.prev;
     }
 
-    pub fn parent(n: *const NodeTest) !?*const NodeTest {
+    pub fn parent(n: *const NodeTest) ?*const NodeTest {
         return n.par;
     }
 
@@ -891,7 +879,7 @@ pub const NodeTest = struct {
         return false;
     }
 
-    pub fn text(_: *const NodeTest) !?[]const u8 {
+    pub fn text(_: *const NodeTest) ?[]const u8 {
         return null;
     }
 
@@ -899,7 +887,7 @@ pub const NodeTest = struct {
         return false;
     }
 
-    pub fn isEmptyText(_: *const NodeTest) !bool {
+    pub fn isEmptyText(_: *const NodeTest) bool {
         return false;
     }
 
@@ -993,6 +981,11 @@ test "Browser.CSS.Selector: matchFirst" {
             .n = .{ .child = &.{ .name = "p", .sibling = &.{ .name = "p", .att = "bar" } } },
             .exp = 0,
         },
+        .{
+            .q = "[foo=1baz]",
+            .n = .{ .child = &.{ .name = "p", .sibling = &.{ .name = "p", .att = "bar" } } },
+            .exp = 0,
+        },
         .{
             .q = "[foo!=bar]",
             .n = .{ .child = &.{ .name = "p", .sibling = &.{ .name = "p", .att = "bar" } } },

src/browser/cssom/CSSRuleList.zig

@@ -19,7 +19,6 @@
 const std = @import("std");
 
 const CSSRule = @import("CSSRule.zig");
-const StyleSheet = @import("StyleSheet.zig").StyleSheet;
 
 const CSSImportRule = CSSRule.CSSImportRule;
 

src/browser/cssom/CSSStyleDeclaration.zig

@@ -190,7 +190,7 @@ fn isNumericWithUnit(value: []const u8) bool {
     return CSSKeywords.isValidUnit(unit);
 }
 
-fn isHexColor(value: []const u8) bool {
+pub fn isHexColor(value: []const u8) bool {
     if (value.len == 0) {
         return false;
     }
@@ -199,7 +199,7 @@ fn isHexColor(value: []const u8) bool {
     }
 
     const hex_part = value[1..];
-    if (hex_part.len != 3 and hex_part.len != 6 and hex_part.len != 8) {
+    if (hex_part.len != 3 and hex_part.len != 4 and hex_part.len != 6 and hex_part.len != 8) {
         return false;
     }
 
@@ -551,6 +551,7 @@ test "Browser: CSS.StyleDeclaration: isNumericWithUnit - edge cases and invalid
 
 test "Browser: CSS.StyleDeclaration: isHexColor - valid hex colors" {
     try testing.expect(isHexColor("#000"));
+    try testing.expect(isHexColor("#0000"));
     try testing.expect(isHexColor("#fff"));
     try testing.expect(isHexColor("#123456"));
     try testing.expect(isHexColor("#abcdef"));
@@ -563,7 +564,6 @@ test "Browser: CSS.StyleDeclaration: isHexColor - invalid hex colors" {
     try testing.expect(!isHexColor("#"));
     try testing.expect(!isHexColor("000"));
     try testing.expect(!isHexColor("#00"));
-    try testing.expect(!isHexColor("#0000"));
     try testing.expect(!isHexColor("#00000"));
     try testing.expect(!isHexColor("#0000000"));
     try testing.expect(!isHexColor("#000000000"));

src/browser/cssom/CSSStyleSheet.zig

@@ -18,7 +18,7 @@
 
 const std = @import("std");
 
-const Env = @import("../env.zig").Env;
+const js = @import("../js/js.zig");
 const Page = @import("../page.zig").Page;
 const StyleSheet = @import("StyleSheet.zig");
 const CSSRuleList = @import("CSSRuleList.zig");
@@ -73,15 +73,13 @@ pub fn _deleteRule(self: *CSSStyleSheet, index: usize) !void {
     _ = self.css_rules.list.orderedRemove(index);
 }
 
-pub fn _replace(self: *CSSStyleSheet, text: []const u8, page: *Page) !Env.Promise {
+pub fn _replace(self: *CSSStyleSheet, text: []const u8, page: *Page) !js.Promise {
     _ = self;
     _ = text;
     // TODO: clear self.css_rules
     // parse text and re-populate self.css_rules
 
-    const resolver = page.main_context.createPromiseResolver();
-    try resolver.resolve({});
-    return resolver.promise();
+    return page.js.resolvePromise({});
 }
 
 pub fn _replaceSync(self: *CSSStyleSheet, text: []const u8) !void {

src/browser/cssom/color.zig

@@ -0,0 +1,283 @@
+// Copyright (C) 2023-2025  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+const Io = std.Io;
+
+const CSSParser = @import("CSSParser.zig");
+const isHexColor = @import("CSSStyleDeclaration.zig").isHexColor;
+
+pub const RGBA = packed struct(u32) {
+    r: u8,
+    g: u8,
+    b: u8,
+    /// Opaque by default.
+    a: u8 = std.math.maxInt(u8),
+
+    pub const Named = struct {
+        // Basic colors (CSS Level 1)
+        pub const black: RGBA = .init(0, 0, 0, 1);
+        pub const silver: RGBA = .init(192, 192, 192, 1);
+        pub const gray: RGBA = .init(128, 128, 128, 1);
+        pub const white: RGBA = .init(255, 255, 255, 1);
+        pub const maroon: RGBA = .init(128, 0, 0, 1);
+        pub const red: RGBA = .init(255, 0, 0, 1);
+        pub const purple: RGBA = .init(128, 0, 128, 1);
+        pub const fuchsia: RGBA = .init(255, 0, 255, 1);
+        pub const green: RGBA = .init(0, 128, 0, 1);
+        pub const lime: RGBA = .init(0, 255, 0, 1);
+        pub const olive: RGBA = .init(128, 128, 0, 1);
+        pub const yellow: RGBA = .init(255, 255, 0, 1);
+        pub const navy: RGBA = .init(0, 0, 128, 1);
+        pub const blue: RGBA = .init(0, 0, 255, 1);
+        pub const teal: RGBA = .init(0, 128, 128, 1);
+        pub const aqua: RGBA = .init(0, 255, 255, 1);
+
+        // Extended colors (CSS Level 2+)
+        pub const aliceblue: RGBA = .init(240, 248, 255, 1);
+        pub const antiquewhite: RGBA = .init(250, 235, 215, 1);
+        pub const aquamarine: RGBA = .init(127, 255, 212, 1);
+        pub const azure: RGBA = .init(240, 255, 255, 1);
+        pub const beige: RGBA = .init(245, 245, 220, 1);
+        pub const bisque: RGBA = .init(255, 228, 196, 1);
+        pub const blanchedalmond: RGBA = .init(255, 235, 205, 1);
+        pub const blueviolet: RGBA = .init(138, 43, 226, 1);
+        pub const brown: RGBA = .init(165, 42, 42, 1);
+        pub const burlywood: RGBA = .init(222, 184, 135, 1);
+        pub const cadetblue: RGBA = .init(95, 158, 160, 1);
+        pub const chartreuse: RGBA = .init(127, 255, 0, 1);
+        pub const chocolate: RGBA = .init(210, 105, 30, 1);
+        pub const coral: RGBA = .init(255, 127, 80, 1);
+        pub const cornflowerblue: RGBA = .init(100, 149, 237, 1);
+        pub const cornsilk: RGBA = .init(255, 248, 220, 1);
+        pub const crimson: RGBA = .init(220, 20, 60, 1);
+        pub const cyan: RGBA = .init(0, 255, 255, 1); // Synonym of aqua
+        pub const darkblue: RGBA = .init(0, 0, 139, 1);
+        pub const darkcyan: RGBA = .init(0, 139, 139, 1);
+        pub const darkgoldenrod: RGBA = .init(184, 134, 11, 1);
+        pub const darkgray: RGBA = .init(169, 169, 169, 1);
+        pub const darkgreen: RGBA = .init(0, 100, 0, 1);
+        pub const darkgrey: RGBA = .init(169, 169, 169, 1); // Synonym of darkgray
+        pub const darkkhaki: RGBA = .init(189, 183, 107, 1);
+        pub const darkmagenta: RGBA = .init(139, 0, 139, 1);
+        pub const darkolivegreen: RGBA = .init(85, 107, 47, 1);
+        pub const darkorange: RGBA = .init(255, 140, 0, 1);
+        pub const darkorchid: RGBA = .init(153, 50, 204, 1);
+        pub const darkred: RGBA = .init(139, 0, 0, 1);
+        pub const darksalmon: RGBA = .init(233, 150, 122, 1);
+        pub const darkseagreen: RGBA = .init(143, 188, 143, 1);
+        pub const darkslateblue: RGBA = .init(72, 61, 139, 1);
+        pub const darkslategray: RGBA = .init(47, 79, 79, 1);
+        pub const darkslategrey: RGBA = .init(47, 79, 79, 1); // Synonym of darkslategray
+        pub const darkturquoise: RGBA = .init(0, 206, 209, 1);
+        pub const darkviolet: RGBA = .init(148, 0, 211, 1);
+        pub const deeppink: RGBA = .init(255, 20, 147, 1);
+        pub const deepskyblue: RGBA = .init(0, 191, 255, 1);
+        pub const dimgray: RGBA = .init(105, 105, 105, 1);
+        pub const dimgrey: RGBA = .init(105, 105, 105, 1); // Synonym of dimgray
+        pub const dodgerblue: RGBA = .init(30, 144, 255, 1);
+        pub const firebrick: RGBA = .init(178, 34, 34, 1);
+        pub const floralwhite: RGBA = .init(255, 250, 240, 1);
+        pub const forestgreen: RGBA = .init(34, 139, 34, 1);
+        pub const gainsboro: RGBA = .init(220, 220, 220, 1);
+        pub const ghostwhite: RGBA = .init(248, 248, 255, 1);
+        pub const gold: RGBA = .init(255, 215, 0, 1);
+        pub const goldenrod: RGBA = .init(218, 165, 32, 1);
+        pub const greenyellow: RGBA = .init(173, 255, 47, 1);
+        pub const grey: RGBA = .init(128, 128, 128, 1); // Synonym of gray
+        pub const honeydew: RGBA = .init(240, 255, 240, 1);
+        pub const hotpink: RGBA = .init(255, 105, 180, 1);
+        pub const indianred: RGBA = .init(205, 92, 92, 1);
+        pub const indigo: RGBA = .init(75, 0, 130, 1);
+        pub const ivory: RGBA = .init(255, 255, 240, 1);
+        pub const khaki: RGBA = .init(240, 230, 140, 1);
+        pub const lavender: RGBA = .init(230, 230, 250, 1);
+        pub const lavenderblush: RGBA = .init(255, 240, 245, 1);
+        pub const lawngreen: RGBA = .init(124, 252, 0, 1);
+        pub const lemonchiffon: RGBA = .init(255, 250, 205, 1);
+        pub const lightblue: RGBA = .init(173, 216, 230, 1);
+        pub const lightcoral: RGBA = .init(240, 128, 128, 1);
+        pub const lightcyan: RGBA = .init(224, 255, 255, 1);
+        pub const lightgoldenrodyellow: RGBA = .init(250, 250, 210, 1);
+        pub const lightgray: RGBA = .init(211, 211, 211, 1);
+        pub const lightgreen: RGBA = .init(144, 238, 144, 1);
+        pub const lightgrey: RGBA = .init(211, 211, 211, 1); // Synonym of lightgray
+        pub const lightpink: RGBA = .init(255, 182, 193, 1);
+        pub const lightsalmon: RGBA = .init(255, 160, 122, 1);
+        pub const lightseagreen: RGBA = .init(32, 178, 170, 1);
+        pub const lightskyblue: RGBA = .init(135, 206, 250, 1);
+        pub const lightslategray: RGBA = .init(119, 136, 153, 1);
+        pub const lightslategrey: RGBA = .init(119, 136, 153, 1); // Synonym of lightslategray
+        pub const lightsteelblue: RGBA = .init(176, 196, 222, 1);
+        pub const lightyellow: RGBA = .init(255, 255, 224, 1);
+        pub const limegreen: RGBA = .init(50, 205, 50, 1);
+        pub const linen: RGBA = .init(250, 240, 230, 1);
+        pub const magenta: RGBA = .init(255, 0, 255, 1); // Synonym of fuchsia
+        pub const mediumaquamarine: RGBA = .init(102, 205, 170, 1);
+        pub const mediumblue: RGBA = .init(0, 0, 205, 1);
+        pub const mediumorchid: RGBA = .init(186, 85, 211, 1);
+        pub const mediumpurple: RGBA = .init(147, 112, 219, 1);
+        pub const mediumseagreen: RGBA = .init(60, 179, 113, 1);
+        pub const mediumslateblue: RGBA = .init(123, 104, 238, 1);
+        pub const mediumspringgreen: RGBA = .init(0, 250, 154, 1);
+        pub const mediumturquoise: RGBA = .init(72, 209, 204, 1);
+        pub const mediumvioletred: RGBA = .init(199, 21, 133, 1);
+        pub const midnightblue: RGBA = .init(25, 25, 112, 1);
+        pub const mintcream: RGBA = .init(245, 255, 250, 1);
+        pub const mistyrose: RGBA = .init(255, 228, 225, 1);
+        pub const moccasin: RGBA = .init(255, 228, 181, 1);
+        pub const navajowhite: RGBA = .init(255, 222, 173, 1);
+        pub const oldlace: RGBA = .init(253, 245, 230, 1);
+        pub const olivedrab: RGBA = .init(107, 142, 35, 1);
+        pub const orange: RGBA = .init(255, 165, 0, 1);
+        pub const orangered: RGBA = .init(255, 69, 0, 1);
+        pub const orchid: RGBA = .init(218, 112, 214, 1);
+        pub const palegoldenrod: RGBA = .init(238, 232, 170, 1);
+        pub const palegreen: RGBA = .init(152, 251, 152, 1);
+        pub const paleturquoise: RGBA = .init(175, 238, 238, 1);
+        pub const palevioletred: RGBA = .init(219, 112, 147, 1);
+        pub const papayawhip: RGBA = .init(255, 239, 213, 1);
+        pub const peachpuff: RGBA = .init(255, 218, 185, 1);
+        pub const peru: RGBA = .init(205, 133, 63, 1);
+        pub const pink: RGBA = .init(255, 192, 203, 1);
+        pub const plum: RGBA = .init(221, 160, 221, 1);
+        pub const powderblue: RGBA = .init(176, 224, 230, 1);
+        pub const rebeccapurple: RGBA = .init(102, 51, 153, 1);
+        pub const rosybrown: RGBA = .init(188, 143, 143, 1);
+        pub const royalblue: RGBA = .init(65, 105, 225, 1);
+        pub const saddlebrown: RGBA = .init(139, 69, 19, 1);
+        pub const salmon: RGBA = .init(250, 128, 114, 1);
+        pub const sandybrown: RGBA = .init(244, 164, 96, 1);
+        pub const seagreen: RGBA = .init(46, 139, 87, 1);
+        pub const seashell: RGBA = .init(255, 245, 238, 1);
+        pub const sienna: RGBA = .init(160, 82, 45, 1);
+        pub const skyblue: RGBA = .init(135, 206, 235, 1);
+        pub const slateblue: RGBA = .init(106, 90, 205, 1);
+        pub const slategray: RGBA = .init(112, 128, 144, 1);
+        pub const slategrey: RGBA = .init(112, 128, 144, 1); // Synonym of slategray
+        pub const snow: RGBA = .init(255, 250, 250, 1);
+        pub const springgreen: RGBA = .init(0, 255, 127, 1);
+        pub const steelblue: RGBA = .init(70, 130, 180, 1);
+        pub const tan: RGBA = .init(210, 180, 140, 1);
+        pub const thistle: RGBA = .init(216, 191, 216, 1);
+        pub const tomato: RGBA = .init(255, 99, 71, 1);
+        pub const transparent: RGBA = .init(0, 0, 0, 0);
+        pub const turquoise: RGBA = .init(64, 224, 208, 1);
+        pub const violet: RGBA = .init(238, 130, 238, 1);
+        pub const wheat: RGBA = .init(245, 222, 179, 1);
+        pub const whitesmoke: RGBA = .init(245, 245, 245, 1);
+        pub const yellowgreen: RGBA = .init(154, 205, 50, 1);
+    };
+
+    pub fn init(r: u8, g: u8, b: u8, a: f32) RGBA {
+        const clamped = std.math.clamp(a, 0, 1);
+        return .{ .r = r, .g = g, .b = b, .a = @intFromFloat(clamped * 255) };
+    }
+
+    /// Finds a color by its name.
+    pub fn find(name: []const u8) ?RGBA {
+        const match = std.meta.stringToEnum(std.meta.DeclEnum(Named), name) orelse return null;
+
+        return switch (match) {
+            inline else => |comptime_enum| @field(Named, @tagName(comptime_enum)),
+        };
+    }
+
+    /// Parses the given color.
+    /// Currently we only parse hex colors and named colors; other variants
+    /// require CSS evaluation.
+    pub fn parse(input: []const u8) !RGBA {
+        if (!isHexColor(input)) {
+            // Try named colors.
+            return find(input) orelse return error.Invalid;
+        }
+
+        const slice = input[1..];
+        switch (slice.len) {
+            // This means the digit for a color is repeated.
+            // Given HEX is #f0c, its interpreted the same as #FF00CC.
+            3 => {
+                const r = try std.fmt.parseInt(u8, &.{ slice[0], slice[0] }, 16);
+                const g = try std.fmt.parseInt(u8, &.{ slice[1], slice[1] }, 16);
+                const b = try std.fmt.parseInt(u8, &.{ slice[2], slice[2] }, 16);
+                return .{ .r = r, .g = g, .b = b, .a = 255 };
+            },
+            4 => {
+                const r = try std.fmt.parseInt(u8, &.{ slice[0], slice[0] }, 16);
+                const g = try std.fmt.parseInt(u8, &.{ slice[1], slice[1] }, 16);
+                const b = try std.fmt.parseInt(u8, &.{ slice[2], slice[2] }, 16);
+                const a = try std.fmt.parseInt(u8, &.{ slice[3], slice[3] }, 16);
+                return .{ .r = r, .g = g, .b = b, .a = a };
+            },
+            // Regular HEX format.
+            6 => {
+                const r = try std.fmt.parseInt(u8, slice[0..2], 16);
+                const g = try std.fmt.parseInt(u8, slice[2..4], 16);
+                const b = try std.fmt.parseInt(u8, slice[4..6], 16);
+                return .{ .r = r, .g = g, .b = b, .a = 255 };
+            },
+            8 => {
+                const r = try std.fmt.parseInt(u8, slice[0..2], 16);
+                const g = try std.fmt.parseInt(u8, slice[2..4], 16);
+                const b = try std.fmt.parseInt(u8, slice[4..6], 16);
+                const a = try std.fmt.parseInt(u8, slice[6..8], 16);
+                return .{ .r = r, .g = g, .b = b, .a = a };
+            },
+            else => return error.Invalid,
+        }
+    }
+
+    /// By default, browsers prefer lowercase formatting.
+    const format_upper = false;
+
+    /// Formats the `Color` according to web expectations.
+    /// If color is opaque, HEX is preferred; RGBA otherwise.
+    pub fn format(self: *const RGBA, writer: *Io.Writer) Io.Writer.Error!void {
+        if (self.isOpaque()) {
+            // Convert RGB to HEX.
+            // https://gristle.tripod.com/hexconv.html
+            // Hexadecimal characters up to 15.
+            const char: []const u8 = "0123456789" ++ if (format_upper) "ABCDEF" else "abcdef";
+            // This variant always prefers 6 digit format, +1 is for hash char.
+            const buffer = [7]u8{
+                '#',
+                char[self.r >> 4],
+                char[self.r & 15],
+                char[self.g >> 4],
+                char[self.g & 15],
+                char[self.b >> 4],
+                char[self.b & 15],
+            };
+
+            return writer.writeAll(&buffer);
+        }
+
+        // Prefer RGBA format for everything else.
+        return writer.print("rgba({d}, {d}, {d}, {d:.2})", .{ self.r, self.g, self.b, self.normalizedAlpha() });
+    }
+
+    /// Returns true if `Color` is opaque.
+    pub inline fn isOpaque(self: *const RGBA) bool {
+        return self.a == std.math.maxInt(u8);
+    }
+
+    /// Returns the normalized alpha value.
+    pub inline fn normalizedAlpha(self: *const RGBA) f32 {
+        return @as(f32, @floatFromInt(self.a)) / 255;
+    }
+};

src/browser/dom/Animation.zig

@@ -18,19 +18,17 @@
 
 const std = @import("std");
 
+const js = @import("../js/js.zig");
 const Page = @import("../page.zig").Page;
-const JsObject = @import("../env.zig").JsObject;
-const Promise = @import("../env.zig").Promise;
-const PromiseResolver = @import("../env.zig").PromiseResolver;
 
 const Animation = @This();
 
-effect: ?JsObject,
-timeline: ?JsObject,
-ready_resolver: ?PromiseResolver,
-finished_resolver: ?PromiseResolver,
+effect: ?js.Object,
+timeline: ?js.Object,
+ready_resolver: ?js.PromiseResolver,
+finished_resolver: ?js.PromiseResolver,
 
-pub fn constructor(effect: ?JsObject, timeline: ?JsObject) !Animation {
+pub fn constructor(effect: ?js.Object, timeline: ?js.Object) !Animation {
     return .{
         .effect = if (effect) |eo| try eo.persist() else null,
         .timeline = if (timeline) |to| try to.persist() else null,
@@ -49,37 +47,37 @@ pub fn get_pending(self: *const Animation) bool {
     return false;
 }
 
-pub fn get_finished(self: *Animation, page: *Page) !Promise {
+pub fn get_finished(self: *Animation, page: *Page) !js.Promise {
     if (self.finished_resolver == null) {
-        const resolver = page.main_context.createPromiseResolver();
+        const resolver = page.js.createPromiseResolver(.none);
         try resolver.resolve(self);
         self.finished_resolver = resolver;
     }
     return self.finished_resolver.?.promise();
 }
 
-pub fn get_ready(self: *Animation, page: *Page) !Promise {
+pub fn get_ready(self: *Animation, page: *Page) !js.Promise {
     // never resolved, because we're always "finished"
     if (self.ready_resolver == null) {
-        const resolver = page.main_context.createPromiseResolver();
+        const resolver = page.js.createPromiseResolver(.none);
         self.ready_resolver = resolver;
     }
     return self.ready_resolver.?.promise();
 }
 
-pub fn get_effect(self: *const Animation) ?JsObject {
+pub fn get_effect(self: *const Animation) ?js.Object {
     return self.effect;
 }
 
-pub fn set_effect(self: *Animation, effect: JsObject) !void {
+pub fn set_effect(self: *Animation, effect: js.Object) !void {
     self.effect = try effect.persist();
 }
 
-pub fn get_timeline(self: *const Animation) ?JsObject {
+pub fn get_timeline(self: *const Animation) ?js.Object {
     return self.timeline;
 }
 
-pub fn set_timeline(self: *Animation, timeline: JsObject) !void {
+pub fn set_timeline(self: *Animation, timeline: js.Object) !void {
     self.timeline = try timeline.persist();
 }
 

src/browser/dom/IntersectionObserver.zig

@@ -0,0 +1,329 @@
+// Copyright (C) 2023-2025  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+
+const js = @import("../js/js.zig");
+const log = @import("../../log.zig");
+const parser = @import("../netsurf.zig");
+const Page = @import("../page.zig").Page;
+const Node = @import("node.zig").Node;
+const Element = @import("element.zig").Element;
+
+pub const Interfaces = .{
+    IntersectionObserver,
+    Entry,
+};
+
+// This implementation attempts to be as less wrong as possible. Since we don't
+// render, or know how things are positioned, our best guess isn't very good.
+const IntersectionObserver = @This();
+page: *Page,
+root: *parser.Node,
+callback: js.Function,
+event_node: parser.EventNode,
+observed_entries: std.ArrayList(Entry),
+pending_elements: std.ArrayList(*parser.Element),
+ready_elements: std.ArrayList(*parser.Element),
+
+pub fn constructor(callback: js.Function, opts_: ?IntersectionObserverOptions, page: *Page) !*IntersectionObserver {
+    const opts = opts_ orelse IntersectionObserverOptions{};
+
+    const self = try page.arena.create(IntersectionObserver);
+    self.* = .{
+        .page = page,
+        .callback = callback,
+        .ready_elements = .{},
+        .observed_entries = .{},
+        .pending_elements = .{},
+        .event_node = .{ .func = mutationCallback },
+        .root = opts.root orelse parser.documentToNode(parser.documentHTMLToDocument(page.window.document)),
+    };
+
+    _ = try parser.eventTargetAddEventListener(
+        parser.toEventTarget(parser.Node, self.root),
+        "DOMNodeInserted",
+        &self.event_node,
+        false,
+    );
+
+    _ = try parser.eventTargetAddEventListener(
+        parser.toEventTarget(parser.Node, self.root),
+        "DOMNodeRemoved",
+        &self.event_node,
+        false,
+    );
+
+    return self;
+}
+
+pub fn _disconnect(self: *IntersectionObserver) !void {
+    // We don't free as it is on an arena
+    self.ready_elements = .{};
+    self.observed_entries = .{};
+    self.pending_elements = .{};
+}
+
+pub fn _observe(self: *IntersectionObserver, target_element: *parser.Element, page: *Page) !void {
+    for (self.observed_entries.items) |*observer| {
+        if (observer.target == target_element) {
+            return; // Already observed
+        }
+    }
+
+    if (self.isPending(target_element)) {
+        return; // Already pending
+    }
+
+    for (self.ready_elements.items) |element| {
+        if (element == target_element) {
+            return; // Already primed
+        }
+    }
+
+    // We can never fire callbacks synchronously. Code like React expects any
+    // callback to fire in the future (e.g. via microtasks).
+    try self.ready_elements.append(self.page.arena, target_element);
+    if (self.ready_elements.items.len == 1) {
+        // this is our first ready entry, schedule a callback
+        try page.scheduler.add(self, processReady, 0, .{
+            .name = "intersection ready",
+        });
+    }
+}
+
+pub fn _unobserve(self: *IntersectionObserver, target: *parser.Element) !void {
+    if (self.removeObserved(target)) {
+        return;
+    }
+
+    for (self.ready_elements.items, 0..) |el, index| {
+        if (el == target) {
+            _ = self.ready_elements.swapRemove(index);
+            return;
+        }
+    }
+
+    for (self.pending_elements.items, 0..) |el, index| {
+        if (el == target) {
+            _ = self.pending_elements.swapRemove(index);
+            return;
+        }
+    }
+}
+
+pub fn _takeRecords(self: *IntersectionObserver) []Entry {
+    return self.observed_entries.items;
+}
+
+fn processReady(ctx: *anyopaque) ?u32 {
+    const self: *IntersectionObserver = @ptrCast(@alignCast(ctx));
+    self._processReady() catch |err| {
+        log.err(.web_api, "intersection ready", .{ .err = err });
+    };
+    return null;
+}
+
+fn _processReady(self: *IntersectionObserver) !void {
+    defer self.ready_elements.clearRetainingCapacity();
+    for (self.ready_elements.items) |element| {
+        // IntersectionObserver probably doesn't work like what your intuition
+        // thinks. As long as a node has a parent, even if that parent isn't
+        // connected and even if the two nodes don't intersect, it'll fire the
+        // callback once.
+        if (try Node.get_parentNode(@ptrCast(element)) == null) {
+            if (!self.isPending(element)) {
+                try self.pending_elements.append(self.page.arena, element);
+            }
+            continue;
+        }
+        try self.forceObserve(element);
+    }
+}
+
+fn isPending(self: *IntersectionObserver, element: *parser.Element) bool {
+    for (self.pending_elements.items) |el| {
+        if (el == element) {
+            return true;
+        }
+    }
+    return false;
+}
+
+fn mutationCallback(en: *parser.EventNode, event: *parser.Event) void {
+    const mutation_event = parser.eventToMutationEvent(event);
+    const self: *IntersectionObserver = @fieldParentPtr("event_node", en);
+    self._mutationCallback(mutation_event) catch |err| {
+        log.err(.web_api, "mutation callback", .{ .err = err, .source = "intersection observer" });
+    };
+}
+
+fn _mutationCallback(self: *IntersectionObserver, event: *parser.MutationEvent) !void {
+    const event_type = parser.eventType(@ptrCast(event));
+
+    if (std.mem.eql(u8, event_type, "DOMNodeInserted")) {
+        const node = parser.mutationEventRelatedNode(event) catch return orelse return;
+        if (parser.nodeType(node) != .element) {
+            return;
+        }
+        const el: *parser.Element = @ptrCast(node);
+        if (self.removePending(el)) {
+            // It was pending (because it wasn't in the root), but now it is
+            // we should observe it.
+            try self.forceObserve(el);
+        }
+        return;
+    }
+
+    if (std.mem.eql(u8, event_type, "DOMNodeRemoved")) {
+        const node = parser.mutationEventRelatedNode(event) catch return orelse return;
+        if (parser.nodeType(node) != .element) {
+            return;
+        }
+
+        const el: *parser.Element = @ptrCast(node);
+        if (self.removeObserved(el)) {
+            // It _was_ observed, it no longer is in our root, but if it was
+            // to get re-added, it should be observed again (I think), so
+            // we add it to our pending list
+            try self.pending_elements.append(self.page.arena, el);
+        }
+
+        return;
+    }
+
+    // impossible event type
+    unreachable;
+}
+
+// Exists to skip the checks made _observe when called from a DOMNodeInserted
+// event. In such events, the event handler has alread done the necessary
+// checks.
+fn forceObserve(self: *IntersectionObserver, target: *parser.Element) !void {
+    try self.observed_entries.append(self.page.arena, .{
+        .page = self.page,
+        .root = self.root,
+        .target = target,
+    });
+
+    var result: js.Function.Result = undefined;
+    self.callback.tryCall(void, .{self.observed_entries.items}, &result) catch {
+        log.debug(.user_script, "callback error", .{
+            .err = result.exception,
+            .stack = result.stack,
+            .source = "intersection observer",
+        });
+    };
+}
+
+fn removeObserved(self: *IntersectionObserver, target: *parser.Element) bool {
+    for (self.observed_entries.items, 0..) |*observer, index| {
+        if (observer.target == target) {
+            _ = self.observed_entries.swapRemove(index);
+            return true;
+        }
+    }
+    return false;
+}
+
+fn removePending(self: *IntersectionObserver, target: *parser.Element) bool {
+    for (self.pending_elements.items, 0..) |el, index| {
+        if (el == target) {
+            _ = self.pending_elements.swapRemove(index);
+            return true;
+        }
+    }
+    return false;
+}
+
+const IntersectionObserverOptions = struct {
+    root: ?*parser.Node = null, // Element or Document
+    rootMargin: ?[]const u8 = "0px 0px 0px 0px",
+    threshold: ?Threshold = .{ .single = 0.0 },
+
+    const Threshold = union(enum) {
+        single: f32,
+        list: []const f32,
+    };
+};
+
+// https://developer.mozilla.org/en-US/docs/Web/API/Entry
+// https://w3c.github.io/IntersectionObserver/#intersection-observer-entry
+pub const Entry = struct {
+    page: *Page,
+    root: *parser.Node,
+    target: *parser.Element,
+
+    // Returns the bounds rectangle of the target element as a DOMRectReadOnly. The bounds are computed as described in the documentation for Element.getBoundingClientRect().
+    pub fn get_boundingClientRect(self: *const Entry) !Element.DOMRect {
+        return Element._getBoundingClientRect(self.target, self.page);
+    }
+
+    // Returns the ratio of the intersectionRect to the boundingClientRect.
+    pub fn get_intersectionRatio(_: *const Entry) f32 {
+        return 1.0;
+    }
+
+    // Returns a DOMRectReadOnly representing the target's visible area.
+    pub fn get_intersectionRect(self: *const Entry) !Element.DOMRect {
+        return Element._getBoundingClientRect(self.target, self.page);
+    }
+
+    // A Boolean value which is true if the target element intersects with the
+    // intersection observer's root. If this is true, then, the
+    // Entry describes a transition into a state of
+    // intersection; if it's false, then you know the transition is from
+    // intersecting to not-intersecting.
+    pub fn get_isIntersecting(_: *const Entry) bool {
+        return true;
+    }
+
+    // Returns a DOMRectReadOnly for the intersection observer's root.
+    pub fn get_rootBounds(self: *const Entry) !Element.DOMRect {
+        const root = self.root;
+        if (@intFromPtr(root) == @intFromPtr(self.page.window.document)) {
+            return self.page.renderer.boundingRect();
+        }
+
+        const root_type = parser.nodeType(root);
+
+        var element: *parser.Element = undefined;
+        switch (root_type) {
+            .element => element = parser.nodeToElement(root),
+            .document => {
+                const doc = parser.nodeToDocument(root);
+                element = (try parser.documentGetDocumentElement(doc)).?;
+            },
+            else => return error.InvalidState,
+        }
+
+        return Element._getBoundingClientRect(element, self.page);
+    }
+
+    // The Element whose intersection with the root changed.
+    pub fn get_target(self: *const Entry) *parser.Element {
+        return self.target;
+    }
+
+    // TODO: pub fn get_time(self: *const Entry)
+};
+
+const testing = @import("../../testing.zig");
+test "Browser: DOM.IntersectionObserver" {
+    try testing.htmlRunner("dom/intersection_observer.html");
+}

src/browser/dom/MessageChannel.zig

@@ -20,13 +20,11 @@ const std = @import("std");
 const log = @import("../../log.zig");
 const parser = @import("../netsurf.zig");
 
-const Env = @import("../env.zig").Env;
+const js = @import("../js/js.zig");
 const Page = @import("../page.zig").Page;
 const EventTarget = @import("../dom/event_target.zig").EventTarget;
 const EventHandler = @import("../events/event.zig").EventHandler;
 
-const JsObject = Env.JsObject;
-const Function = Env.Function;
 const Allocator = std.mem.Allocator;
 
 const MAX_QUEUE_SIZE = 10;
@@ -72,29 +70,28 @@ pub const MessagePort = struct {
     pair: *MessagePort,
     closed: bool = false,
     started: bool = false,
-    onmessage_cbk: ?Function = null,
-    onmessageerror_cbk: ?Function = null,
+    onmessage_cbk: ?js.Function = null,
+    onmessageerror_cbk: ?js.Function = null,
     // This is the queue of messages to dispatch to THIS MessagePort when the
     // MessagePort is started.
-    queue: std.ArrayListUnmanaged(JsObject) = .empty,
+    queue: std.ArrayListUnmanaged(js.Object) = .empty,
 
     pub const PostMessageOption = union(enum) {
-        transfer: JsObject,
+        transfer: js.Object,
         options: Opts,
 
         pub const Opts = struct {
-            transfer: JsObject,
+            transfer: js.Object,
         };
     };
 
-    pub fn _postMessage(self: *MessagePort, obj: JsObject, opts_: ?PostMessageOption, page: *Page) !void {
+    pub fn _postMessage(self: *MessagePort, obj: js.Object, opts_: ?PostMessageOption, page: *Page) !void {
         if (self.closed) {
             return;
         }
 
         if (opts_ != null) {
             log.warn(.web_api, "not implemented", .{ .feature = "MessagePort postMessage options" });
-            return error.NotImplemented;
         }
 
         try self.pair.dispatchOrQueue(obj, page.arena);
@@ -125,10 +122,10 @@ pub const MessagePort = struct {
         self.pair.closed = true;
     }
 
-    pub fn get_onmessage(self: *MessagePort) ?Function {
+    pub fn get_onmessage(self: *MessagePort) ?js.Function {
         return self.onmessage_cbk;
     }
-    pub fn get_onmessageerror(self: *MessagePort) ?Function {
+    pub fn get_onmessageerror(self: *MessagePort) ?js.Function {
         return self.onmessageerror_cbk;
     }
 
@@ -153,7 +150,7 @@ pub const MessagePort = struct {
 
     // called from our pair. If port1.postMessage("x") is called, then this
     // will be called on port2.
-    fn dispatchOrQueue(self: *MessagePort, obj: JsObject, arena: Allocator) !void {
+    fn dispatchOrQueue(self: *MessagePort, obj: js.Object, arena: Allocator) !void {
         // our pair should have checked this already
         std.debug.assert(self.closed == false);
 
@@ -168,7 +165,7 @@ pub const MessagePort = struct {
         return self.queue.append(arena, try obj.persist());
     }
 
-    fn dispatch(self: *MessagePort, obj: JsObject) !void {
+    fn dispatch(self: *MessagePort, obj: js.Object) !void {
         // obj is already persisted, don't use `MessageEvent.constructor`, but
         // go directly to `init`, which assumes persisted objects.
         var evt = try MessageEvent.init(.{ .data = obj });
@@ -183,7 +180,7 @@ pub const MessagePort = struct {
         alloc: Allocator,
         typ: []const u8,
         listener: EventHandler.Listener,
-    ) !?Function {
+    ) !?js.Function {
         const target = @as(*parser.EventTarget, @ptrCast(self));
         const eh = (try EventHandler.register(alloc, target, typ, listener, null)) orelse unreachable;
         return eh.callback;
@@ -208,12 +205,12 @@ pub const MessageEvent = struct {
     pub const union_make_copy = true;
 
     proto: parser.Event,
-    data: ?JsObject,
+    data: ?js.Object,
 
     // You would think if port1 sends to port2, the source would be port2
     // (which is how I read the documentation), but it appears to always be
     // null. It can always be set explicitly via the constructor;
-    source: ?JsObject,
+    source: ?js.Object,
 
     origin: []const u8,
 
@@ -227,8 +224,8 @@ pub const MessageEvent = struct {
     ports: []*MessagePort,
 
     const Options = struct {
-        data: ?JsObject = null,
-        source: ?JsObject = null,
+        data: ?js.Object = null,
+        source: ?js.Object = null,
         origin: []const u8 = "",
         lastEventId: []const u8 = "",
         ports: []*MessagePort = &.{},
@@ -244,7 +241,7 @@ pub const MessageEvent = struct {
         });
     }
 
-    // This is like "constructor", but it assumes JsObjects have already been
+    // This is like "constructor", but it assumes js.Objects have already been
     // persisted. Necessary because this `new MessageEvent()` can be called
     // directly from JS OR from a port.postMessage. In the latter case, data
     // may have already been persisted (as it might need to be queued);
@@ -264,7 +261,7 @@ pub const MessageEvent = struct {
         };
     }
 
-    pub fn get_data(self: *const MessageEvent) !?JsObject {
+    pub fn get_data(self: *const MessageEvent) !?js.Object {
         return self.data;
     }
 
@@ -272,7 +269,7 @@ pub const MessageEvent = struct {
         return self.origin;
     }
 
-    pub fn get_source(self: *const MessageEvent) ?JsObject {
+    pub fn get_source(self: *const MessageEvent) ?js.Object {
         return self.source;
     }
 

src/browser/dom/attribute.zig

@@ -25,24 +25,24 @@ pub const Attr = struct {
     pub const prototype = *Node;
     pub const subtype = .node;
 
-    pub fn get_namespaceURI(self: *parser.Attribute) !?[]const u8 {
-        return try parser.nodeGetNamespace(parser.attributeToNode(self));
+    pub fn get_namespaceURI(self: *parser.Attribute) ?[]const u8 {
+        return parser.nodeGetNamespace(parser.attributeToNode(self));
     }
 
-    pub fn get_prefix(self: *parser.Attribute) !?[]const u8 {
-        return try parser.nodeGetPrefix(parser.attributeToNode(self));
+    pub fn get_prefix(self: *parser.Attribute) ?[]const u8 {
+        return parser.nodeGetPrefix(parser.attributeToNode(self));
     }
 
     pub fn get_localName(self: *parser.Attribute) ![]const u8 {
-        return try parser.nodeLocalName(parser.attributeToNode(self));
+        return parser.nodeLocalName(parser.attributeToNode(self));
     }
 
     pub fn get_name(self: *parser.Attribute) ![]const u8 {
-        return try parser.attributeGetName(self);
+        return parser.attributeGetName(self);
     }
 
     pub fn get_value(self: *parser.Attribute) !?[]const u8 {
-        return try parser.attributeGetValue(self);
+        return parser.attributeGetValue(self);
     }
 
     pub fn set_value(self: *parser.Attribute, v: []const u8) !?[]const u8 {

src/browser/dom/character_data.zig

@@ -51,7 +51,7 @@ pub const CharacterData = struct {
     }
 
     pub fn get_nextElementSibling(self: *parser.CharacterData) !?ElementUnion {
-        const res = try parser.nodeNextElementSibling(parser.characterDataToNode(self));
+        const res = parser.nodeNextElementSibling(parser.characterDataToNode(self));
         if (res == null) {
             return null;
         }
@@ -59,7 +59,7 @@ pub const CharacterData = struct {
     }
 
     pub fn get_previousElementSibling(self: *parser.CharacterData) !?ElementUnion {
-        const res = try parser.nodePreviousElementSibling(parser.characterDataToNode(self));
+        const res = parser.nodePreviousElementSibling(parser.characterDataToNode(self));
         if (res == null) {
             return null;
         }
@@ -68,8 +68,8 @@ pub const CharacterData = struct {
 
     // Read/Write attributes
 
-    pub fn get_data(self: *parser.CharacterData) ![]const u8 {
-        return try parser.characterDataData(self);
+    pub fn get_data(self: *parser.CharacterData) []const u8 {
+        return parser.characterDataData(self);
     }
 
     pub fn set_data(self: *parser.CharacterData, data: []const u8) !void {
@@ -96,18 +96,18 @@ pub const CharacterData = struct {
     }
 
     pub fn _substringData(self: *parser.CharacterData, offset: u32, count: u32) ![]const u8 {
-        return try parser.characterDataSubstringData(self, offset, count);
+        return parser.characterDataSubstringData(self, offset, count);
     }
 
     // netsurf's CharacterData (text, comment) doesn't implement the
     // dom_node_get_attributes and thus will crash if we try to call nodeIsEqualNode.
-    pub fn _isEqualNode(self: *parser.CharacterData, other_node: *parser.Node) !bool {
-        if (try parser.nodeType(@ptrCast(@alignCast(self))) != try parser.nodeType(other_node)) {
+    pub fn _isEqualNode(self: *parser.CharacterData, other_node: *parser.Node) bool {
+        if (parser.nodeType(@ptrCast(@alignCast(self))) != parser.nodeType(other_node)) {
             return false;
         }
 
         const other: *parser.CharacterData = @ptrCast(other_node);
-        if (std.mem.eql(u8, try get_data(self), try get_data(other)) == false) {
+        if (std.mem.eql(u8, get_data(self), get_data(other)) == false) {
             return false;
         }
 

src/browser/dom/document.zig

@@ -17,8 +17,9 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
-
 const log = @import("../../log.zig");
+
+const js = @import("../js/js.zig");
 const parser = @import("../netsurf.zig");
 const Page = @import("../page.zig").Page;
 
@@ -38,8 +39,6 @@ const Range = @import("range.zig").Range;
 
 const CustomEvent = @import("../events/custom_event.zig").CustomEvent;
 
-const Env = @import("../env.zig").Env;
-
 const DOMImplementation = @import("implementation.zig").DOMImplementation;
 
 // WEB IDL https://dom.spec.whatwg.org/#document
@@ -156,22 +155,14 @@ pub const Document = struct {
     // the spec changed to return an HTMLCollection instead.
     // That's why we reimplemented getElementsByTagName by using an
     // HTMLCollection in zig here.
-    pub fn _getElementsByTagName(
-        self: *parser.Document,
-        tag_name: []const u8,
-        page: *Page,
-    ) !collection.HTMLCollection {
-        return try collection.HTMLCollectionByTagName(page.arena, parser.documentToNode(self), tag_name, .{
+    pub fn _getElementsByTagName(self: *parser.Document, tag_name: js.String) !collection.HTMLCollection {
+        return collection.HTMLCollectionByTagName(parser.documentToNode(self), tag_name.string, .{
             .include_root = true,
         });
     }
 
-    pub fn _getElementsByClassName(
-        self: *parser.Document,
-        classNames: []const u8,
-        page: *Page,
-    ) !collection.HTMLCollection {
-        return try collection.HTMLCollectionByClassName(page.arena, parser.documentToNode(self), classNames, .{
+    pub fn _getElementsByClassName(self: *parser.Document, class_names: js.String) !collection.HTMLCollection {
+        return collection.HTMLCollectionByClassName(parser.documentToNode(self), class_names.string, .{
             .include_root = true,
         });
     }
@@ -308,24 +299,87 @@ pub const Document = struct {
         return &.{};
     }
 
-    pub fn get_adoptedStyleSheets(self: *parser.Document, page: *Page) !Env.JsObject {
+    pub fn get_adoptedStyleSheets(self: *parser.Document, page: *Page) !js.Object {
         const state = try page.getOrCreateNodeState(@ptrCast(@alignCast(self)));
         if (state.adopted_style_sheets) |obj| {
             return obj;
         }
 
-        const obj = try page.main_context.newArray(0).persist();
+        const obj = try page.js.createArray(0).persist();
         state.adopted_style_sheets = obj;
         return obj;
     }
 
-    pub fn set_adoptedStyleSheets(self: *parser.Document, sheets: Env.JsObject, page: *Page) !void {
+    pub fn set_adoptedStyleSheets(self: *parser.Document, sheets: js.Object, page: *Page) !void {
         const state = try page.getOrCreateNodeState(@ptrCast(@alignCast(self)));
         state.adopted_style_sheets = try sheets.persist();
     }
+
+    pub fn _hasFocus(_: *parser.Document) bool {
+        log.debug(.web_api, "not implemented", .{ .feature = "Document hasFocus" });
+        return true;
+    }
+
+    pub fn _open(_: *parser.Document, page: *Page) !*parser.DocumentHTML {
+        if (page.open) {
+            return page.window.document;
+        }
+
+        // This implementation is invalid.
+        // According to MDN, we should cleanup registered listeners.
+        // So we sould cleanup previous DOM memory.
+        // But this implementation is more simple for now.
+        const html_doc = try parser.documentHTMLParseFromStr("");
+        try page.setDocument(html_doc);
+        page.open = true;
+
+        return page.window.document;
+    }
+
+    pub fn _close(_: *parser.Document, page: *Page) !void {
+        page.open = false;
+    }
+
+    pub fn _write(self: *parser.Document, str: []const u8, page: *Page) !void {
+        _ = try _open(self, page);
+
+        const document = parser.documentHTMLToDocument(page.window.document);
+        const fragment = try parser.documentParseFragmentFromStr(document, str);
+        const fragment_node = parser.documentFragmentToNode(fragment);
+
+        const fragment_html = parser.nodeFirstChild(fragment_node) orelse return;
+        const fragment_head = parser.nodeFirstChild(fragment_html) orelse return;
+        const fragment_body = parser.nodeNextSibling(fragment_head) orelse return;
+
+        const document_node = parser.documentToNode(document);
+        const document_html = parser.nodeFirstChild(document_node) orelse return;
+        const document_head = parser.nodeFirstChild(document_html) orelse return;
+        const document_body = parser.nodeNextSibling(document_head) orelse return;
+
+        {
+            const children = try parser.nodeGetChildNodes(fragment_head);
+            // always index 0, because nodeAppendChild moves the node out of
+            // the nodeList and into the new tree
+            while (parser.nodeListItem(children, 0)) |child| {
+                _ = try parser.nodeAppendChild(document_head, child);
+            }
+        }
+
+        {
+            const children = try parser.nodeGetChildNodes(fragment_body);
+            // always index 0, because nodeAppendChild moves the node out of
+            // the nodeList and into the new tree
+            while (parser.nodeListItem(children, 0)) |child| {
+                _ = try parser.nodeAppendChild(document_body, child);
+            }
+        }
+    }
 };
 
 const testing = @import("../../testing.zig");
 test "Browser: DOM.Document" {
     try testing.htmlRunner("dom/document.html");
 }
+test "Browser: DOM.Document.write" {
+    try testing.htmlRunner("dom/document_write.html");
+}

src/browser/dom/document_fragment.zig

@@ -38,8 +38,8 @@ pub const DocumentFragment = struct {
         );
     }
 
-    pub fn _isEqualNode(self: *parser.DocumentFragment, other_node: *parser.Node) !bool {
-        const other_type = try parser.nodeType(other_node);
+    pub fn _isEqualNode(self: *parser.DocumentFragment, other_node: *parser.Node) bool {
+        const other_type = parser.nodeType(other_node);
         if (other_type != .document_fragment) {
             return false;
         }

src/browser/dom/document_type.zig

@@ -29,21 +29,21 @@ pub const DocumentType = struct {
     pub const subtype = .node;
 
     pub fn get_name(self: *parser.DocumentType) ![]const u8 {
-        return try parser.documentTypeGetName(self);
+        return parser.documentTypeGetName(self);
     }
 
-    pub fn get_publicId(self: *parser.DocumentType) ![]const u8 {
-        return try parser.documentTypeGetPublicId(self);
+    pub fn get_publicId(self: *parser.DocumentType) []const u8 {
+        return parser.documentTypeGetPublicId(self);
     }
 
-    pub fn get_systemId(self: *parser.DocumentType) ![]const u8 {
-        return try parser.documentTypeGetSystemId(self);
+    pub fn get_systemId(self: *parser.DocumentType) []const u8 {
+        return parser.documentTypeGetSystemId(self);
     }
 
     // netsurf's DocumentType doesn't implement the dom_node_get_attributes
     // and thus will crash if we try to call nodeIsEqualNode.
     pub fn _isEqualNode(self: *parser.DocumentType, other_node: *parser.Node) !bool {
-        if (try parser.nodeType(other_node) != .document_type) {
+        if (parser.nodeType(other_node) != .document_type) {
             return false;
         }
 
@@ -51,10 +51,10 @@ pub const DocumentType = struct {
         if (std.mem.eql(u8, try get_name(self), try get_name(other)) == false) {
             return false;
         }
-        if (std.mem.eql(u8, try get_publicId(self), try get_publicId(other)) == false) {
+        if (std.mem.eql(u8, get_publicId(self), get_publicId(other)) == false) {
             return false;
         }
-        if (std.mem.eql(u8, try get_systemId(self), try get_systemId(other)) == false) {
+        if (std.mem.eql(u8, get_systemId(self), get_systemId(other)) == false) {
             return false;
         }
         return true;

src/browser/dom/dom.zig

@@ -25,7 +25,6 @@ const NodeList = @import("nodelist.zig");
 const Node = @import("node.zig");
 const ResizeObserver = @import("resize_observer.zig");
 const MutationObserver = @import("mutation_observer.zig");
-const IntersectionObserver = @import("intersection_observer.zig");
 const DOMParser = @import("dom_parser.zig").DOMParser;
 const TreeWalker = @import("tree_walker.zig").TreeWalker;
 const NodeIterator = @import("node_iterator.zig").NodeIterator;
@@ -44,7 +43,6 @@ pub const Interfaces = .{
     Node.Interfaces,
     ResizeObserver.Interfaces,
     MutationObserver.Interfaces,
-    IntersectionObserver.Interfaces,
     DOMParser,
     TreeWalker,
     NodeIterator,
@@ -54,4 +52,5 @@ pub const Interfaces = .{
     @import("range.zig").Interfaces,
     @import("Animation.zig"),
     @import("MessageChannel.zig").Interfaces,
+    @import("IntersectionObserver.zig").Interfaces,
 };

src/browser/dom/element.zig

@@ -18,6 +18,7 @@
 
 const std = @import("std");
 
+const js = @import("../js/js.zig");
 const parser = @import("../netsurf.zig");
 const Page = @import("../page.zig").Page;
 
@@ -33,7 +34,6 @@ const HTMLElem = @import("../html/elements.zig");
 const ShadowRoot = @import("../dom/shadow_root.zig").ShadowRoot;
 
 const Animation = @import("Animation.zig");
-const JsObject = @import("../env.zig").JsObject;
 
 pub const Union = @import("../html/elements.zig").Union;
 
@@ -61,7 +61,7 @@ pub const Element = struct {
     pub fn toInterfaceT(comptime T: type, e: *parser.Element) !T {
         const tagname = try parser.elementGetTagName(e) orelse {
             // If the owner's document is HTML, assume we have an HTMLElement.
-            const doc = try parser.nodeOwnerDocument(parser.elementToNode(e));
+            const doc = parser.nodeOwnerDocument(parser.elementToNode(e));
             if (doc != null and !doc.?.is_html) {
                 return .{ .HTMLElement = @as(*parser.ElementHTML, @ptrCast(e)) };
             }
@@ -73,7 +73,7 @@ pub const Element = struct {
 
         const tag = parser.Tag.fromString(tagname) catch {
             // If the owner's document is HTML, assume we have an HTMLElement.
-            const doc = try parser.nodeOwnerDocument(parser.elementToNode(e));
+            const doc = parser.nodeOwnerDocument(parser.elementToNode(e));
             if (doc != null and doc.?.is_html) {
                 return .{ .HTMLElement = @as(*parser.ElementHTML, @ptrCast(e)) };
             }
@@ -87,12 +87,12 @@ pub const Element = struct {
     // JS funcs
     // --------
 
-    pub fn get_namespaceURI(self: *parser.Element) !?[]const u8 {
-        return try parser.nodeGetNamespace(parser.elementToNode(self));
+    pub fn get_namespaceURI(self: *parser.Element) ?[]const u8 {
+        return parser.nodeGetNamespace(parser.elementToNode(self));
     }
 
-    pub fn get_prefix(self: *parser.Element) !?[]const u8 {
-        return try parser.nodeGetPrefix(parser.elementToNode(self));
+    pub fn get_prefix(self: *parser.Element) ?[]const u8 {
+        return parser.nodeGetPrefix(parser.elementToNode(self));
     }
 
     pub fn get_localName(self: *parser.Element) ![]const u8 {
@@ -103,6 +103,14 @@ pub const Element = struct {
         return try parser.nodeName(parser.elementToNode(self));
     }
 
+    pub fn get_dir(self: *parser.Element) ![]const u8 {
+        return try parser.elementGetAttribute(self, "dir") orelse "";
+    }
+
+    pub fn set_dir(self: *parser.Element, dir: []const u8) !void {
+        return parser.elementSetAttribute(self, "dir", dir);
+    }
+
     pub fn get_id(self: *parser.Element) ![]const u8 {
         return try parser.elementGetAttribute(self, "id") orelse "";
     }
@@ -127,6 +135,10 @@ pub const Element = struct {
         return try parser.elementSetAttribute(self, "slot", slot);
     }
 
+    pub fn get_assignedSlot(self: *parser.Element, page: *const Page) !?*parser.Slot {
+        return @import("../SlotChangeMonitor.zig").findSlot(self, page);
+    }
+
     pub fn get_classList(self: *parser.Element) !*parser.TokenList {
         return try parser.tokenListCreate(self, "class");
     }
@@ -150,7 +162,7 @@ pub const Element = struct {
 
     pub fn set_innerHTML(self: *parser.Element, str: []const u8, page: *Page) !void {
         const node = parser.elementToNode(self);
-        const doc = try parser.nodeOwnerDocument(node) orelse return parser.DOMError.WrongDocument;
+        const doc = parser.nodeOwnerDocument(node) orelse return parser.DOMError.WrongDocument;
         // parse the fragment
         const fragment = try parser.documentParseFragmentFromStr(doc, str);
 
@@ -168,9 +180,9 @@ pub const Element = struct {
         // or an actual document. In a blank page, something like:
         //    x.innerHTML = '<script></script>';
         // does _not_ create an empty script, but in a real page, it does. Weird.
-        const html = try parser.nodeFirstChild(fragment_node) orelse return;
-        const head = try parser.nodeFirstChild(html) orelse return;
-        const body = try parser.nodeNextSibling(head) orelse return;
+        const html = parser.nodeFirstChild(fragment_node) orelse return;
+        const head = parser.nodeFirstChild(html) orelse return;
+        const body = parser.nodeNextSibling(head) orelse return;
 
         if (try parser.elementTag(self) == .template) {
             // HTMLElementTemplate is special. We don't append these as children
@@ -179,11 +191,9 @@ pub const Element = struct {
             // a new fragment
             const clean = try parser.documentCreateDocumentFragment(doc);
             const children = try parser.nodeGetChildNodes(body);
-            const ln = try parser.nodeListLength(children);
-            for (0..ln) |_| {
-                // always index 0, because nodeAppendChild moves the node out of
-                // the nodeList and into the new tree
-                const child = try parser.nodeListItem(children, 0) orelse continue;
+            // always index 0, because nodeAppendChild moves the node out of
+            // the nodeList and into the new tree
+            while (parser.nodeListItem(children, 0)) |child| {
                 _ = try parser.nodeAppendChild(@ptrCast(@alignCast(clean)), child);
             }
 
@@ -197,27 +207,102 @@ pub const Element = struct {
         {
             // First, copy some of the head element
             const children = try parser.nodeGetChildNodes(head);
-            const ln = try parser.nodeListLength(children);
-            for (0..ln) |_| {
-                // always index 0, because nodeAppendChild moves the node out of
-                // the nodeList and into the new tree
-                const child = try parser.nodeListItem(children, 0) orelse continue;
+            // always index 0, because nodeAppendChild moves the node out of
+            // the nodeList and into the new tree
+            while (parser.nodeListItem(children, 0)) |child| {
                 _ = try parser.nodeAppendChild(node, child);
             }
         }
 
         {
             const children = try parser.nodeGetChildNodes(body);
-            const ln = try parser.nodeListLength(children);
-            for (0..ln) |_| {
-                // always index 0, because nodeAppendChild moves the node out of
-                // the nodeList and into the new tree
-                const child = try parser.nodeListItem(children, 0) orelse continue;
+            // always index 0, because nodeAppendChild moves the node out of
+            // the nodeList and into the new tree
+            while (parser.nodeListItem(children, 0)) |child| {
                 _ = try parser.nodeAppendChild(node, child);
             }
         }
     }
 
+    /// Parses the given `input` string and inserts its children to an element at given `position`.
+    /// https://developer.mozilla.org/en-US/docs/Web/API/Element/insertAdjacentHTML
+    ///
+    /// TODO: Support for XML parsing and `TrustedHTML` instances.
+    pub fn _insertAdjacentHTML(self: *parser.Element, position: []const u8, input: []const u8) !void {
+        const self_node = parser.elementToNode(self);
+        const doc = parser.nodeOwnerDocument(self_node) orelse {
+            return parser.DOMError.WrongDocument;
+        };
+
+        // Parse the fragment.
+        // Should return error.Syntax on fail?
+        const fragment = try parser.documentParseFragmentFromStr(doc, input);
+        const fragment_node = parser.documentFragmentToNode(fragment);
+
+        // We always get it wrapped like so:
+        // <html><head></head><body>{ ... }</body></html>
+        // None of the following can be null.
+        const maybe_html = parser.nodeFirstChild(fragment_node);
+        std.debug.assert(maybe_html != null);
+        const html = maybe_html orelse return;
+
+        const maybe_body = parser.nodeLastChild(html);
+        std.debug.assert(maybe_body != null);
+        const body = maybe_body orelse return;
+
+        const children = try parser.nodeGetChildNodes(body);
+
+        // * `target_node` is `*Node` (where we actually insert),
+        // * `prev_node` is `?*Node`.
+        const target_node, const prev_node = blk: {
+            // Prefer case-sensitive match.
+            // "beforeend" was the most common case in my tests; we might adjust the order
+            // depending on which ones websites prefer most.
+            if (std.mem.eql(u8, position, "beforeend")) {
+                break :blk .{ self_node, null };
+            }
+
+            if (std.mem.eql(u8, position, "afterbegin")) {
+                // Get the first child; null indicates there are no children.
+                const first_child = parser.nodeFirstChild(self_node);
+                break :blk .{ self_node, first_child };
+            }
+
+            if (std.mem.eql(u8, position, "beforebegin")) {
+                // The node must have a parent node in order to use this variant.
+                const parent = parser.nodeParentNode(self_node) orelse return error.NoModificationAllowed;
+                // Parent cannot be Document.
+                // Should have checks for document_fragment and document_type?
+                if (parser.nodeType(parent) == .document) {
+                    return error.NoModificationAllowed;
+                }
+
+                break :blk .{ parent, self_node };
+            }
+
+            if (std.mem.eql(u8, position, "afterend")) {
+                // The node must have a parent node in order to use this variant.
+                const parent = parser.nodeParentNode(self_node) orelse return error.NoModificationAllowed;
+                // Parent cannot be Document.
+                if (parser.nodeType(parent) == .document) {
+                    return error.NoModificationAllowed;
+                }
+                // Get the next sibling or null; null indicates our node is the only one.
+                const sibling = parser.nodeNextSibling(self_node);
+                break :blk .{ parent, sibling };
+            }
+
+            // Thrown if:
+            // * position is not one of the four listed values.
+            // * The input is XML that is not well-formed.
+            return error.Syntax;
+        };
+
+        while (parser.nodeListItem(children, 0)) |child| {
+            _ = try parser.nodeInsertBefore(target_node, child, prev_node);
+        }
+    }
+
     // The closest() method of the Element interface traverses the element and its parents (heading toward the document root) until it finds a node that matches the specified CSS selector.
     // Returns the closest ancestor Element or itself, which matches the selectors. If there are no such element, null.
     pub fn _closest(self: *parser.Element, selector: []const u8, page: *Page) !?*parser.Element {
@@ -234,7 +319,7 @@ pub const Element = struct {
                 }
                 return parser.nodeToElement(current.node);
             }
-            current = try current.parent() orelse return null;
+            current = current.parent() orelse return null;
         }
     }
 
@@ -350,28 +435,18 @@ pub const Element = struct {
         return try parser.elementRemoveAttributeNode(self, attr);
     }
 
-    pub fn _getElementsByTagName(
-        self: *parser.Element,
-        tag_name: []const u8,
-        page: *Page,
-    ) !collection.HTMLCollection {
-        return try collection.HTMLCollectionByTagName(
-            page.arena,
+    pub fn _getElementsByTagName(self: *parser.Element, tag_name: js.String) !collection.HTMLCollection {
+        return collection.HTMLCollectionByTagName(
             parser.elementToNode(self),
-            tag_name,
+            tag_name.string,
             .{ .include_root = false },
         );
     }
 
-    pub fn _getElementsByClassName(
-        self: *parser.Element,
-        classNames: []const u8,
-        page: *Page,
-    ) !collection.HTMLCollection {
+    pub fn _getElementsByClassName(self: *parser.Element, class_names: js.String) !collection.HTMLCollection {
         return try collection.HTMLCollectionByClassName(
-            page.arena,
             parser.elementToNode(self),
-            classNames,
+            class_names.string,
             .{ .include_root = false },
         );
     }
@@ -407,13 +482,13 @@ pub const Element = struct {
     // NonDocumentTypeChildNode
     // https://dom.spec.whatwg.org/#interface-nondocumenttypechildnode
     pub fn get_previousElementSibling(self: *parser.Element) !?Union {
-        const res = try parser.nodePreviousElementSibling(parser.elementToNode(self));
+        const res = parser.nodePreviousElementSibling(parser.elementToNode(self));
         if (res == null) return null;
         return try toInterface(res.?);
     }
 
     pub fn get_nextElementSibling(self: *parser.Element) !?Union {
-        const res = try parser.nodeNextElementSibling(parser.elementToNode(self));
+        const res = parser.nodeNextElementSibling(parser.elementToNode(self));
         if (res == null) return null;
         return try toInterface(res.?);
     }
@@ -426,7 +501,7 @@ pub const Element = struct {
         while (true) {
             next = try walker.get_next(root, next) orelse return null;
             // ignore non-element nodes.
-            if (try parser.nodeType(next.?) != .element) {
+            if (parser.nodeType(next.?) != .element) {
                 continue;
             }
             const e = parser.nodeToElement(next.?);
@@ -474,7 +549,7 @@ pub const Element = struct {
     // Returns a 0 DOMRect object if the element is eventually detached from the main window
     pub fn _getBoundingClientRect(self: *parser.Element, page: *Page) !DOMRect {
         // Since we are lazy rendering we need to do this check. We could store the renderer in a viewport such that it could cache these, but it would require tracking changes.
-        if (!try page.isNodeAttached(parser.elementToNode(self))) {
+        if (!page.isNodeAttached(parser.elementToNode(self))) {
             return DOMRect{
                 .x = 0,
                 .y = 0,
@@ -493,7 +568,7 @@ pub const Element = struct {
     // We do not render so it only always return the element's bounding rect.
     // Returns an empty array if the element is eventually detached from the main window
     pub fn _getClientRects(self: *parser.Element, page: *Page) ![]DOMRect {
-        if (!try page.isNodeAttached(parser.elementToNode(self))) {
+        if (!page.isNodeAttached(parser.elementToNode(self))) {
             return &.{};
         }
         const heap_ptr = try page.call_arena.create(DOMRect);
@@ -524,6 +599,8 @@ pub const Element = struct {
         contentVisibilityAuto: bool,
         opacityProperty: bool,
         visibilityProperty: bool,
+        checkVisibilityCSS: bool,
+        checkOpacity: bool,
     };
 
     pub fn _checkVisibility(self: *parser.Element, opts: ?CheckVisibilityOpts) bool {
@@ -549,7 +626,7 @@ pub const Element = struct {
         }
 
         // Not sure what to do if there is no owner document
-        const doc = try parser.nodeOwnerDocument(@ptrCast(self)) orelse return error.InvalidArgument;
+        const doc = parser.nodeOwnerDocument(@ptrCast(self)) orelse return error.InvalidArgument;
         const fragment = try parser.documentCreateDocumentFragment(doc);
         const sr = try page.arena.create(ShadowRoot);
         sr.* = .{
@@ -583,7 +660,7 @@ pub const Element = struct {
         return sr;
     }
 
-    pub fn _animate(self: *parser.Element, effect: JsObject, opts: JsObject) !Animation {
+    pub fn _animate(self: *parser.Element, effect: js.Object, opts: js.Object) !Animation {
         _ = self;
         _ = opts;
         return Animation.constructor(effect, null);
@@ -595,7 +672,7 @@ pub const Element = struct {
         // for related elements JIT by walking the tree, but there could be
         // cases in libdom or the Zig WebAPI where this reference is kept
         const as_node: *parser.Node = @ptrCast(self);
-        const parent = try parser.nodeParentNode(as_node) orelse return;
+        const parent = parser.nodeParentNode(as_node) orelse return;
         _ = try Node._removeChild(parent, as_node);
     }
 };

src/browser/dom/event_target.zig

@@ -17,7 +17,6 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
-const Env = @import("../env.zig").Env;
 const parser = @import("../netsurf.zig");
 const Page = @import("../page.zig").Page;
 
@@ -35,6 +34,7 @@ pub const Union = union(enum) {
     screen_orientation: *@import("../html/screen.zig").ScreenOrientation,
     performance: *@import("performance.zig").Performance,
     media_query_list: *@import("../html/media_query_list.zig").MediaQueryList,
+    navigation: *@import("../navigation/Navigation.zig"),
 };
 
 // EventTarget implementation
@@ -48,7 +48,7 @@ pub const EventTarget = struct {
     pub fn toInterface(et: *parser.EventTarget, page: *Page) !Union {
         // libdom assumes that all event targets are libdom nodes. They are not.
 
-        switch (try parser.eventTargetInternalType(et)) {
+        switch (parser.eventTargetInternalType(et)) {
             .libdom_node => {
                 return .{ .node = try nod.Node.toInterface(@as(*parser.Node, @ptrCast(et))) };
             },
@@ -83,6 +83,11 @@ pub const EventTarget = struct {
             .media_query_list => {
                 return .{ .media_query_list = @fieldParentPtr("base", @as(*parser.EventTargetTBase, @ptrCast(et))) };
             },
+            .navigation => {
+                const NavigationEventTarget = @import("../navigation/NavigationEventTarget.zig");
+                const base: *NavigationEventTarget = @fieldParentPtr("base", @as(*parser.EventTargetTBase, @ptrCast(et)));
+                return .{ .navigation = @fieldParentPtr("proto", base) };
+            },
         }
     }
 
@@ -90,6 +95,7 @@ pub const EventTarget = struct {
     // --------
     pub fn constructor(page: *Page) !*parser.EventTarget {
         const et = try page.arena.create(EventTarget);
+        et.* = .{};
         return @ptrCast(&et.base);
     }
 
@@ -101,6 +107,9 @@ pub const EventTarget = struct {
         page: *Page,
     ) !void {
         _ = try EventHandler.register(page.arena, self, typ, listener, opts);
+        if (std.mem.eql(u8, typ, "slotchange")) {
+            try page.registerSlotChangeMonitor();
+        }
     }
 
     const RemoveEventListenerOpts = union(enum) {

src/browser/dom/html_collection.zig

@@ -23,7 +23,6 @@ const parser = @import("../netsurf.zig");
 
 const Element = @import("element.zig").Element;
 const Union = @import("element.zig").Union;
-const JsThis = @import("../env.zig").JsThis;
 const Walker = @import("walker.zig").Walker;
 
 const Matcher = union(enum) {
@@ -52,13 +51,13 @@ pub const MatchByTagName = struct {
     tag: []const u8,
     is_wildcard: bool,
 
-    fn init(arena: Allocator, tag_name: []const u8) !MatchByTagName {
+    fn init(tag_name: []const u8) MatchByTagName {
         if (std.mem.eql(u8, tag_name, "*")) {
             return .{ .tag = "*", .is_wildcard = true };
         }
 
         return .{
-            .tag = try arena.dupe(u8, tag_name),
+            .tag = tag_name,
             .is_wildcard = false,
         };
     }
@@ -69,15 +68,14 @@ pub const MatchByTagName = struct {
 };
 
 pub fn HTMLCollectionByTagName(
-    arena: Allocator,
     root: ?*parser.Node,
     tag_name: []const u8,
     opts: Opts,
-) !HTMLCollection {
-    return HTMLCollection{
+) HTMLCollection {
+    return .{
         .root = root,
         .walker = .{ .walkerDepthFirst = .{} },
-        .matcher = .{ .matchByTagName = try MatchByTagName.init(arena, tag_name) },
+        .matcher = .{ .matchByTagName = MatchByTagName.init(tag_name) },
         .mutable = opts.mutable,
         .include_root = opts.include_root,
     };
@@ -86,9 +84,9 @@ pub fn HTMLCollectionByTagName(
 pub const MatchByClassName = struct {
     class_names: []const u8,
 
-    fn init(arena: Allocator, class_names: []const u8) !MatchByClassName {
+    fn init(class_names: []const u8) !MatchByClassName {
         return .{
-            .class_names = try arena.dupe(u8, class_names),
+            .class_names = class_names,
         };
     }
 
@@ -107,15 +105,14 @@ pub const MatchByClassName = struct {
 };
 
 pub fn HTMLCollectionByClassName(
-    arena: Allocator,
     root: ?*parser.Node,
-    classNames: []const u8,
+    class_names: []const u8,
     opts: Opts,
 ) !HTMLCollection {
     return HTMLCollection{
         .root = root,
         .walker = .{ .walkerDepthFirst = .{} },
-        .matcher = .{ .matchByClassName = try MatchByClassName.init(arena, classNames) },
+        .matcher = .{ .matchByClassName = try MatchByClassName.init(class_names) },
         .mutable = opts.mutable,
         .include_root = opts.include_root,
     };
@@ -124,10 +121,8 @@ pub fn HTMLCollectionByClassName(
 pub const MatchByName = struct {
     name: []const u8,
 
-    fn init(arena: Allocator, name: []const u8) !MatchByName {
-        return .{
-            .name = try arena.dupe(u8, name),
-        };
+    fn init(name: []const u8) !MatchByName {
+        return .{ .name = name };
     }
 
     pub fn match(self: MatchByName, node: *parser.Node) !bool {
@@ -138,7 +133,6 @@ pub const MatchByName = struct {
 };
 
 pub fn HTMLCollectionByName(
-    arena: Allocator,
     root: ?*parser.Node,
     name: []const u8,
     opts: Opts,
@@ -146,7 +140,7 @@ pub fn HTMLCollectionByName(
     return HTMLCollection{
         .root = root,
         .walker = .{ .walkerDepthFirst = .{} },
-        .matcher = .{ .matchByName = try MatchByName.init(arena, name) },
+        .matcher = .{ .matchByName = try MatchByName.init(name) },
         .mutable = opts.mutable,
         .include_root = opts.include_root,
     };
@@ -203,8 +197,8 @@ pub fn HTMLCollectionChildren(
     };
 }
 
-pub fn HTMLCollectionEmpty() !HTMLCollection {
-    return HTMLCollection{
+pub fn HTMLCollectionEmpty() HTMLCollection {
+    return .{
         .root = null,
         .walker = .{ .walkerNone = .{} },
         .matcher = .{ .matchFalse = .{} },
@@ -226,14 +220,11 @@ pub const MatchByLinks = struct {
     }
 };
 
-pub fn HTMLCollectionByLinks(
-    root: ?*parser.Node,
-    opts: Opts,
-) !HTMLCollection {
-    return HTMLCollection{
+pub fn HTMLCollectionByLinks(root: ?*parser.Node, opts: Opts) HTMLCollection {
+    return .{
         .root = root,
         .walker = .{ .walkerDepthFirst = .{} },
-        .matcher = .{ .matchByLinks = MatchByLinks{} },
+        .matcher = .{ .matchByLinks = .{} },
         .mutable = opts.mutable,
         .include_root = opts.include_root,
     };
@@ -252,14 +243,11 @@ pub const MatchByAnchors = struct {
     }
 };
 
-pub fn HTMLCollectionByAnchors(
-    root: ?*parser.Node,
-    opts: Opts,
-) !HTMLCollection {
-    return HTMLCollection{
+pub fn HTMLCollectionByAnchors(root: ?*parser.Node, opts: Opts) HTMLCollection {
+    return .{
         .root = root,
         .walker = .{ .walkerDepthFirst = .{} },
-        .matcher = .{ .matchByAnchors = MatchByAnchors{} },
+        .matcher = .{ .matchByAnchors = .{} },
         .mutable = opts.mutable,
         .include_root = opts.include_root,
     };
@@ -298,7 +286,7 @@ const Opts = struct {
 
 // WEB IDL https://dom.spec.whatwg.org/#htmlcollection
 // HTMLCollection is re implemented in zig here because libdom
-// dom_html_collection expects a comparison function callback as arguement.
+// dom_html_collection expects a comparison function callback as argument.
 // But we wanted a dynamically comparison here, according to the match tagname.
 pub const HTMLCollection = struct {
     matcher: Matcher,
@@ -344,7 +332,7 @@ pub const HTMLCollection = struct {
         var node = try self.start() orelse return 0;
 
         while (true) {
-            if (try parser.nodeType(node) == .element) {
+            if (parser.nodeType(node) == .element) {
                 if (try self.matcher.match(node)) {
                     len += 1;
                 }
@@ -371,7 +359,7 @@ pub const HTMLCollection = struct {
         }
 
         while (true) {
-            if (try parser.nodeType(node) == .element) {
+            if (parser.nodeType(node) == .element) {
                 if (try self.matcher.match(node)) {
                     // check if we found the searched element.
                     if (i == index) {
@@ -405,7 +393,7 @@ pub const HTMLCollection = struct {
         var node = try self.start() orelse return null;
 
         while (true) {
-            if (try parser.nodeType(node) == .element) {
+            if (parser.nodeType(node) == .element) {
                 if (try self.matcher.match(node)) {
                     const elem = @as(*parser.Element, @ptrCast(node));
 
@@ -440,24 +428,23 @@ pub const HTMLCollection = struct {
         return null;
     }
 
-    pub fn postAttach(self: *HTMLCollection, js_this: JsThis) !void {
-        const len = try self.get_length();
-        for (0..len) |i| {
-            const node = try self.item(@intCast(i)) orelse unreachable;
-            const e = @as(*parser.Element, @ptrCast(node));
-            const as_interface = try Element.toInterface(e);
-            try js_this.setIndex(@intCast(i), as_interface, .{});
+    pub fn indexed_get(self: *HTMLCollection, index: u32, has_value: *bool) !?Union {
+        return (try _item(self, index)) orelse {
+            has_value.* = false;
+            return undefined;
+        };
+    }
 
-            if (try item_name(e)) |name| {
-                // Even though an entry might have an empty id, the spec says
-                // that namedItem("") should always return null
-                if (name.len > 0) {
-                    // Named fields should not be enumerable (it is defined with
-                    // the LegacyUnenumerableNamedProperties flag.)
-                    try js_this.set(name, as_interface, .{ .DONT_ENUM = true });
-                }
-            }
+    pub fn named_get(self: *const HTMLCollection, name: []const u8, has_value: *bool) !?Union {
+        // Even though an entry might have an empty id, the spec says
+        // that namedItem("") should always return null
+        if (name.len == 0) {
+            return null;
         }
+        return (try _namedItem(self, name)) orelse {
+            has_value.* = false;
+            return undefined;
+        };
     }
 };
 

src/browser/dom/intersection_observer.zig

@@ -1,186 +0,0 @@
-// Copyright (C) 2023-2025  Lightpanda (Selecy SAS)
-//
-// Francis Bouvier <francis@lightpanda.io>
-// Pierre Tachoire <pierre@lightpanda.io>
-//
-// This program is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Affero General Public License as
-// published by the Free Software Foundation, either version 3 of the
-// License, or (at your option) any later version.
-//
-// This program is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU Affero General Public License for more details.
-//
-// You should have received a copy of the GNU Affero General Public License
-// along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-const std = @import("std");
-
-const log = @import("../../log.zig");
-const parser = @import("../netsurf.zig");
-const Page = @import("../page.zig").Page;
-
-const Env = @import("../env.zig").Env;
-const Element = @import("element.zig").Element;
-
-pub const Interfaces = .{
-    IntersectionObserver,
-    IntersectionObserverEntry,
-};
-
-// This is supposed to listen to change between the root and observation targets.
-// However, our rendered stores everything as 1 pixel sized boxes in a long row that never changes.
-// As such, there are no changes to intersections between the root and any target.
-// Instead we keep a list of all entries that are being observed.
-// The callback is called with all entries everytime a new entry is added(observed).
-// Potentially we should also call the callback at a regular interval.
-// The returned Entries are phony, they always indicate full intersection.
-// https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver
-pub const IntersectionObserver = struct {
-    page: *Page,
-    callback: Env.Function,
-    options: IntersectionObserverOptions,
-
-    observed_entries: std.ArrayListUnmanaged(IntersectionObserverEntry),
-
-    // new IntersectionObserver(callback)
-    // new IntersectionObserver(callback, options) [not supported yet]
-    pub fn constructor(callback: Env.Function, options_: ?IntersectionObserverOptions, page: *Page) !IntersectionObserver {
-        var options = IntersectionObserverOptions{
-            .root = parser.documentToNode(parser.documentHTMLToDocument(page.window.document)),
-            .rootMargin = "0px 0px 0px 0px",
-            .threshold = .{ .single = 0.0 },
-        };
-        if (options_) |*o| {
-            if (o.root) |root| {
-                options.root = root;
-            } // Other properties are not used due to the way we render
-        }
-
-        return .{
-            .page = page,
-            .callback = callback,
-            .options = options,
-            .observed_entries = .{},
-        };
-    }
-
-    pub fn _disconnect(self: *IntersectionObserver) !void {
-        self.observed_entries = .{}; // We don't free as it is on an arena
-    }
-
-    pub fn _observe(self: *IntersectionObserver, target_element: *parser.Element) !void {
-        for (self.observed_entries.items) |*observer| {
-            if (observer.target == target_element) {
-                return; // Already observed
-            }
-        }
-
-        try self.observed_entries.append(self.page.arena, .{
-            .page = self.page,
-            .target = target_element,
-            .options = &self.options,
-        });
-
-        var result: Env.Function.Result = undefined;
-        self.callback.tryCall(void, .{self.observed_entries.items}, &result) catch {
-            log.debug(.user_script, "callback error", .{
-                .err = result.exception,
-                .stack = result.stack,
-                .source = "intersection observer",
-            });
-        };
-    }
-
-    pub fn _unobserve(self: *IntersectionObserver, target: *parser.Element) !void {
-        for (self.observed_entries.items, 0..) |*observer, index| {
-            if (observer.target == target) {
-                _ = self.observed_entries.swapRemove(index);
-                break;
-            }
-        }
-    }
-
-    pub fn _takeRecords(self: *IntersectionObserver) []IntersectionObserverEntry {
-        return self.observed_entries.items;
-    }
-};
-
-const IntersectionObserverOptions = struct {
-    root: ?*parser.Node, // Element or Document
-    rootMargin: ?[]const u8,
-    threshold: ?Threshold,
-
-    const Threshold = union(enum) {
-        single: f32,
-        list: []const f32,
-    };
-};
-
-// https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserverEntry
-// https://w3c.github.io/IntersectionObserver/#intersection-observer-entry
-pub const IntersectionObserverEntry = struct {
-    page: *Page,
-    target: *parser.Element,
-    options: *IntersectionObserverOptions,
-
-    // Returns the bounds rectangle of the target element as a DOMRectReadOnly. The bounds are computed as described in the documentation for Element.getBoundingClientRect().
-    pub fn get_boundingClientRect(self: *const IntersectionObserverEntry) !Element.DOMRect {
-        return Element._getBoundingClientRect(self.target, self.page);
-    }
-
-    // Returns the ratio of the intersectionRect to the boundingClientRect.
-    pub fn get_intersectionRatio(_: *const IntersectionObserverEntry) f32 {
-        return 1.0;
-    }
-
-    // Returns a DOMRectReadOnly representing the target's visible area.
-    pub fn get_intersectionRect(self: *const IntersectionObserverEntry) !Element.DOMRect {
-        return Element._getBoundingClientRect(self.target, self.page);
-    }
-
-    // A Boolean value which is true if the target element intersects with the
-    // intersection observer's root. If this is true, then, the
-    // IntersectionObserverEntry describes a transition into a state of
-    // intersection; if it's false, then you know the transition is from
-    // intersecting to not-intersecting.
-    pub fn get_isIntersecting(_: *const IntersectionObserverEntry) bool {
-        return true;
-    }
-
-    // Returns a DOMRectReadOnly for the intersection observer's root.
-    pub fn get_rootBounds(self: *const IntersectionObserverEntry) !Element.DOMRect {
-        const root = self.options.root.?;
-        if (@intFromPtr(root) == @intFromPtr(self.page.window.document)) {
-            return self.page.renderer.boundingRect();
-        }
-
-        const root_type = try parser.nodeType(root);
-
-        var element: *parser.Element = undefined;
-        switch (root_type) {
-            .element => element = parser.nodeToElement(root),
-            .document => {
-                const doc = parser.nodeToDocument(root);
-                element = (try parser.documentGetDocumentElement(doc)).?;
-            },
-            else => return error.InvalidState,
-        }
-
-        return Element._getBoundingClientRect(element, self.page);
-    }
-
-    // The Element whose intersection with the root changed.
-    pub fn get_target(self: *const IntersectionObserverEntry) *parser.Element {
-        return self.target;
-    }
-
-    // TODO: pub fn get_time(self: *const IntersectionObserverEntry)
-};
-
-const testing = @import("../../testing.zig");
-test "Browser: DOM.IntersectionObserver" {
-    try testing.htmlRunner("dom/intersection_observer.html");
-}

src/browser/dom/mutation_observer.zig

@@ -17,13 +17,12 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
-const Allocator = std.mem.Allocator;
 
+const js = @import("../js/js.zig");
 const log = @import("../../log.zig");
 const parser = @import("../netsurf.zig");
 const Page = @import("../page.zig").Page;
 
-const Env = @import("../env.zig").Env;
 const NodeList = @import("nodelist.zig").NodeList;
 
 pub const Interfaces = .{
@@ -36,21 +35,21 @@ const Walker = @import("../dom/walker.zig").WalkerChildren;
 // WEB IDL https://dom.spec.whatwg.org/#interface-mutationobserver
 pub const MutationObserver = struct {
     page: *Page,
-    cbk: Env.Function,
-    connected: bool,
+    cbk: js.Function,
     scheduled: bool,
+    observers: std.ArrayListUnmanaged(*Observer),
 
     // List of records which were observed. When the call scope ends, we need to
     // execute our callback with it.
     observed: std.ArrayListUnmanaged(MutationRecord),
 
-    pub fn constructor(cbk: Env.Function, page: *Page) !MutationObserver {
+    pub fn constructor(cbk: js.Function, page: *Page) !MutationObserver {
         return .{
             .cbk = cbk,
             .page = page,
             .observed = .{},
-            .connected = true,
             .scheduled = false,
+            .observers = .empty,
         };
     }
 
@@ -69,15 +68,17 @@ pub const MutationObserver = struct {
             .event_node = .{ .id = self.cbk.id, .func = Observer.handle },
         };
 
+        try self.observers.append(arena, observer);
+
         // register node's events
         if (options.childList or options.subtree) {
-            _ = try parser.eventTargetAddEventListener(
+            observer.dom_node_inserted_listener = try parser.eventTargetAddEventListener(
                 parser.toEventTarget(parser.Node, node),
                 "DOMNodeInserted",
                 &observer.event_node,
                 false,
             );
-            _ = try parser.eventTargetAddEventListener(
+            observer.dom_node_removed_listener = try parser.eventTargetAddEventListener(
                 parser.toEventTarget(parser.Node, node),
                 "DOMNodeRemoved",
                 &observer.event_node,
@@ -85,7 +86,7 @@ pub const MutationObserver = struct {
             );
         }
         if (options.attr()) {
-            _ = try parser.eventTargetAddEventListener(
+            observer.dom_node_attribute_modified_listener = try parser.eventTargetAddEventListener(
                 parser.toEventTarget(parser.Node, node),
                 "DOMAttrModified",
                 &observer.event_node,
@@ -93,7 +94,7 @@ pub const MutationObserver = struct {
             );
         }
         if (options.cdata()) {
-            _ = try parser.eventTargetAddEventListener(
+            observer.dom_cdata_modified_listener = try parser.eventTargetAddEventListener(
                 parser.toEventTarget(parser.Node, node),
                 "DOMCharacterDataModified",
                 &observer.event_node,
@@ -101,7 +102,7 @@ pub const MutationObserver = struct {
             );
         }
         if (options.subtree) {
-            _ = try parser.eventTargetAddEventListener(
+            observer.dom_subtree_modified_listener = try parser.eventTargetAddEventListener(
                 parser.toEventTarget(parser.Node, node),
                 "DOMSubtreeModified",
                 &observer.event_node,
@@ -112,10 +113,6 @@ pub const MutationObserver = struct {
 
     fn callback(ctx: *anyopaque) ?u32 {
         const self: *MutationObserver = @ptrCast(@alignCast(ctx));
-        if (self.connected == false) {
-            self.scheduled = true;
-            return null;
-        }
         self.scheduled = false;
 
         const records = self.observed.items;
@@ -125,8 +122,8 @@ pub const MutationObserver = struct {
 
         defer self.observed.clearRetainingCapacity();
 
-        var result: Env.Function.Result = undefined;
-        self.cbk.tryCall(void, .{records}, &result) catch {
+        var result: js.Function.Result = undefined;
+        self.cbk.tryCallWithThis(void, self, .{records}, &result) catch {
             log.debug(.user_script, "callback error", .{
                 .err = result.exception,
                 .stack = result.stack,
@@ -136,9 +133,55 @@ pub const MutationObserver = struct {
         return null;
     }
 
-    // TODO
     pub fn _disconnect(self: *MutationObserver) !void {
-        self.connected = false;
+        for (self.observers.items) |observer| {
+            const event_target = parser.toEventTarget(parser.Node, observer.node);
+            if (observer.dom_node_inserted_listener) |listener| {
+                try parser.eventTargetRemoveEventListener(
+                    event_target,
+                    "DOMNodeInserted",
+                    listener,
+                    false,
+                );
+            }
+
+            if (observer.dom_node_removed_listener) |listener| {
+                try parser.eventTargetRemoveEventListener(
+                    event_target,
+                    "DOMNodeRemoved",
+                    listener,
+                    false,
+                );
+            }
+
+            if (observer.dom_node_attribute_modified_listener) |listener| {
+                try parser.eventTargetRemoveEventListener(
+                    event_target,
+                    "DOMAttrModified",
+                    listener,
+                    false,
+                );
+            }
+
+            if (observer.dom_cdata_modified_listener) |listener| {
+                try parser.eventTargetRemoveEventListener(
+                    event_target,
+                    "DOMCharacterDataModified",
+                    listener,
+                    false,
+                );
+            }
+
+            if (observer.dom_subtree_modified_listener) |listener| {
+                try parser.eventTargetRemoveEventListener(
+                    event_target,
+                    "DOMSubtreeModified",
+                    listener,
+                    false,
+                );
+            }
+        }
+        self.observers.clearRetainingCapacity();
     }
 
     // TODO
@@ -223,6 +266,12 @@ const Observer = struct {
 
     event_node: parser.EventNode,
 
+    dom_node_inserted_listener: ?*parser.EventListener = null,
+    dom_node_removed_listener: ?*parser.EventListener = null,
+    dom_node_attribute_modified_listener: ?*parser.EventListener = null,
+    dom_cdata_modified_listener: ?*parser.EventListener = null,
+    dom_subtree_modified_listener: ?*parser.EventListener = null,
+
     fn appliesTo(
         self: *const Observer,
         target: *parser.Node,
@@ -284,7 +333,7 @@ const Observer = struct {
 
         const mutation_event = parser.eventToMutationEvent(event);
         const event_type = blk: {
-            const t = try parser.eventType(event);
+            const t = parser.eventType(event);
             break :blk std.meta.stringToEnum(MutationEventType, t) orelse return;
         };
 
@@ -302,12 +351,12 @@ const Observer = struct {
             .DOMAttrModified => {
                 record.attribute_name = parser.mutationEventAttributeName(mutation_event) catch null;
                 if (self.options.attributeOldValue) {
-                    record.old_value = parser.mutationEventPrevValue(mutation_event) catch null;
+                    record.old_value = parser.mutationEventPrevValue(mutation_event);
                 }
             },
             .DOMCharacterDataModified => {
                 if (self.options.characterDataOldValue) {
-                    record.old_value = parser.mutationEventPrevValue(mutation_event) catch null;
+                    record.old_value = parser.mutationEventPrevValue(mutation_event);
                 }
             },
             .DOMNodeInserted => {

src/browser/dom/node.zig

@@ -20,7 +20,7 @@ const std = @import("std");
 
 const log = @import("../../log.zig");
 const parser = @import("../netsurf.zig");
-const generate = @import("../../runtime/generate.zig");
+const generate = @import("../js/generate.zig");
 
 const Page = @import("../page.zig").Page;
 const EventTarget = @import("event_target.zig").EventTarget;
@@ -67,7 +67,7 @@ pub const Node = struct {
     pub const subtype = .node;
 
     pub fn toInterface(node: *parser.Node) !Union {
-        return switch (try parser.nodeType(node)) {
+        return switch (parser.nodeType(node)) {
             .element => try Element.toInterfaceT(
                 Union,
                 @as(*parser.Element, @ptrCast(node)),
@@ -124,7 +124,7 @@ pub const Node = struct {
     }
 
     pub fn get_firstChild(self: *parser.Node) !?Union {
-        const res = try parser.nodeFirstChild(self);
+        const res = parser.nodeFirstChild(self);
         if (res == null) {
             return null;
         }
@@ -132,7 +132,7 @@ pub const Node = struct {
     }
 
     pub fn get_lastChild(self: *parser.Node) !?Union {
-        const res = try parser.nodeLastChild(self);
+        const res = parser.nodeLastChild(self);
         if (res == null) {
             return null;
         }
@@ -140,7 +140,7 @@ pub const Node = struct {
     }
 
     pub fn get_nextSibling(self: *parser.Node) !?Union {
-        const res = try parser.nodeNextSibling(self);
+        const res = parser.nodeNextSibling(self);
         if (res == null) {
             return null;
         }
@@ -148,7 +148,7 @@ pub const Node = struct {
     }
 
     pub fn get_previousSibling(self: *parser.Node) !?Union {
-        const res = try parser.nodePreviousSibling(self);
+        const res = parser.nodePreviousSibling(self);
         if (res == null) {
             return null;
         }
@@ -156,7 +156,7 @@ pub const Node = struct {
     }
 
     pub fn get_parentNode(self: *parser.Node) !?Union {
-        const res = try parser.nodeParentNode(self);
+        const res = parser.nodeParentNode(self);
         if (res == null) {
             return null;
         }
@@ -164,7 +164,7 @@ pub const Node = struct {
     }
 
     pub fn get_parentElement(self: *parser.Node) !?ElementUnion {
-        const res = try parser.nodeParentElement(self);
+        const res = parser.nodeParentElement(self);
         if (res == null) {
             return null;
         }
@@ -176,11 +176,11 @@ pub const Node = struct {
     }
 
     pub fn get_nodeType(self: *parser.Node) !u8 {
-        return @intFromEnum(try parser.nodeType(self));
+        return @intFromEnum(parser.nodeType(self));
     }
 
     pub fn get_ownerDocument(self: *parser.Node) !?*parser.DocumentHTML {
-        const res = try parser.nodeOwnerDocument(self);
+        const res = parser.nodeOwnerDocument(self);
         if (res == null) {
             return null;
         }
@@ -190,12 +190,12 @@ pub const Node = struct {
     pub fn get_isConnected(self: *parser.Node) !bool {
         var node = self;
         while (true) {
-            const node_type = try parser.nodeType(node);
+            const node_type = parser.nodeType(node);
             if (node_type == .document) {
                 return true;
             }
 
-            if (try parser.nodeParentNode(node)) |parent| {
+            if (parser.nodeParentNode(node)) |parent| {
                 // didn't find a document, but node has a parent, let's see
                 // if it's connected;
                 node = parent;
@@ -222,15 +222,15 @@ pub const Node = struct {
     // Read/Write attributes
 
     pub fn get_nodeValue(self: *parser.Node) !?[]const u8 {
-        return try parser.nodeValue(self);
+        return parser.nodeValue(self);
     }
 
     pub fn set_nodeValue(self: *parser.Node, data: []u8) !void {
         try parser.nodeSetValue(self, data);
     }
 
-    pub fn get_textContent(self: *parser.Node) !?[]const u8 {
-        return try parser.nodeTextContent(self);
+    pub fn get_textContent(self: *parser.Node) ?[]const u8 {
+        return parser.nodeTextContent(self);
     }
 
     pub fn set_textContent(self: *parser.Node, data: []u8) !void {
@@ -240,8 +240,8 @@ pub const Node = struct {
     // Methods
 
     pub fn _appendChild(self: *parser.Node, child: *parser.Node) !Union {
-        const self_owner = try parser.nodeOwnerDocument(self);
-        const child_owner = try parser.nodeOwnerDocument(child);
+        const self_owner = parser.nodeOwnerDocument(self);
+        const child_owner = parser.nodeOwnerDocument(child);
 
         // If the node to be inserted has a different ownerDocument than the parent node,
         // modern browsers automatically adopt the node and its descendants into
@@ -272,14 +272,14 @@ pub const Node = struct {
             return 0;
         }
 
-        const docself = try parser.nodeOwnerDocument(self) orelse blk: {
-            if (try parser.nodeType(self) == .document) {
+        const docself = parser.nodeOwnerDocument(self) orelse blk: {
+            if (parser.nodeType(self) == .document) {
                 break :blk @as(*parser.Document, @ptrCast(self));
             }
             break :blk null;
         };
-        const docother = try parser.nodeOwnerDocument(other) orelse blk: {
-            if (try parser.nodeType(other) == .document) {
+        const docother = parser.nodeOwnerDocument(other) orelse blk: {
+            if (parser.nodeType(other) == .document) {
                 break :blk @as(*parser.Document, @ptrCast(other));
             }
             break :blk null;
@@ -299,8 +299,8 @@ pub const Node = struct {
                 @intFromEnum(parser.DocumentPosition.contained_by);
         }
 
-        const rootself = try parser.nodeGetRootNode(self);
-        const rootother = try parser.nodeGetRootNode(other);
+        const rootself = parser.nodeGetRootNode(self);
+        const rootother = parser.nodeGetRootNode(other);
         if (rootself != rootother) {
             return @intFromEnum(parser.DocumentPosition.disconnected) +
                 @intFromEnum(parser.DocumentPosition.implementation_specific) +
@@ -347,8 +347,8 @@ pub const Node = struct {
         return 0;
     }
 
-    pub fn _contains(self: *parser.Node, other: *parser.Node) !bool {
-        return try parser.nodeContains(self, other);
+    pub fn _contains(self: *parser.Node, other: *parser.Node) bool {
+        return parser.nodeContains(self, other);
     }
 
     // Returns itself or ancestor object inheriting from Node.
@@ -360,32 +360,60 @@ pub const Node = struct {
         node: Union,
     };
     pub fn _getRootNode(self: *parser.Node, options: ?struct { composed: bool = false }, page: *Page) !GetRootNodeResult {
-        if (options) |options_| if (options_.composed) {
-            log.warn(.web_api, "not implemented", .{ .feature = "getRootNode composed" });
-        };
+        const composed = if (options) |opts| opts.composed else false;
 
-        const root = try parser.nodeGetRootNode(self);
-        if (page.getNodeState(root)) |state| {
-            if (state.shadow_root) |sr| {
-                return .{ .shadow_root = sr };
+        var current_root = parser.nodeGetRootNode(self);
+
+        while (true) {
+            const node_type = parser.nodeType(current_root);
+
+            if (node_type == .document_fragment) {
+                if (parser.documentFragmentGetHost(@ptrCast(current_root))) |host| {
+                    if (page.getNodeState(host)) |state| {
+                        if (state.shadow_root) |sr| {
+                            if (!composed) {
+                                return .{ .shadow_root = sr };
+                            }
+                            current_root = parser.nodeGetRootNode(@ptrCast(sr.host));
+                            continue;
+                        }
+                    }
+                }
             }
+            break;
         }
 
-        return .{ .node = try Node.toInterface(root) };
+        return .{ .node = try Node.toInterface(current_root) };
     }
 
-    pub fn _hasChildNodes(self: *parser.Node) !bool {
-        return try parser.nodeHasChildNodes(self);
+    pub fn _hasChildNodes(self: *parser.Node) bool {
+        return parser.nodeHasChildNodes(self);
+    }
+
+    fn is_template(self: *parser.Node) !bool {
+        if (parser.nodeType(self) != .element) {
+            return false;
+        }
+
+        const e = parser.nodeToElement(self);
+        return try parser.elementTag(e) == .template;
     }
 
     pub fn get_childNodes(self: *parser.Node, page: *Page) !NodeList {
+        // special case for template:
+        // > The Node.childNodes property of the <template> element is always empty
+        // https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/template#usage_notes
+        if (try is_template(self)) {
+            return .{};
+        }
+
         const allocator = page.arena;
         var list: NodeList = .{};
 
-        var n = try parser.nodeFirstChild(self) orelse return list;
+        var n = parser.nodeFirstChild(self) orelse return list;
         while (true) {
             try list.append(allocator, n);
-            n = try parser.nodeNextSibling(n) orelse return list;
+            n = parser.nodeNextSibling(n) orelse return list;
         }
     }
 
@@ -394,8 +422,8 @@ pub const Node = struct {
             return _appendChild(self, new_node);
         }
 
-        const self_owner = try parser.nodeOwnerDocument(self);
-        const new_node_owner = try parser.nodeOwnerDocument(new_node);
+        const self_owner = parser.nodeOwnerDocument(self);
+        const new_node_owner = parser.nodeOwnerDocument(new_node);
 
         // If the node to be inserted has a different ownerDocument than the parent node,
         // modern browsers automatically adopt the node and its descendants into
@@ -415,7 +443,7 @@ pub const Node = struct {
     }
 
     pub fn _isDefaultNamespace(self: *parser.Node, namespace: ?[]const u8) !bool {
-        return try parser.nodeIsDefaultNamespace(self, namespace);
+        return parser.nodeIsDefaultNamespace(self, namespace);
     }
 
     pub fn _isEqualNode(self: *parser.Node, other: *parser.Node) !bool {
@@ -423,10 +451,10 @@ pub const Node = struct {
         return try parser.nodeIsEqualNode(self, other);
     }
 
-    pub fn _isSameNode(self: *parser.Node, other: *parser.Node) !bool {
+    pub fn _isSameNode(self: *parser.Node, other: *parser.Node) bool {
         // TODO: other is not an optional parameter, but can be null.
         // NOTE: there is no need to use isSameNode(); instead use the === strict equality operator
-        return try parser.nodeIsSameNode(self, other);
+        return parser.nodeIsSameNode(self, other);
     }
 
     pub fn _lookupPrefix(self: *parser.Node, namespace: ?[]const u8) !?[]const u8 {
@@ -461,7 +489,7 @@ pub const Node = struct {
 
     // Check if the hierarchy node tree constraints are respected.
     // For now, it checks only if new nodes are not self.
-    // TODO implements the others contraints.
+    // TODO implements the others constraints.
     // see https://dom.spec.whatwg.org/#concept-node-tree
     pub fn hierarchy(self: *parser.Node, nodes: []const NodeOrText) bool {
         for (nodes) |n| {
@@ -482,9 +510,9 @@ pub const Node = struct {
             return parser.DOMError.HierarchyRequest;
         }
 
-        const doc = (try parser.nodeOwnerDocument(self)) orelse return;
+        const doc = (parser.nodeOwnerDocument(self)) orelse return;
 
-        if (try parser.nodeFirstChild(self)) |first| {
+        if (parser.nodeFirstChild(self)) |first| {
             for (nodes) |node| {
                 _ = try parser.nodeInsertBefore(self, try node.toNode(doc), first);
             }
@@ -506,7 +534,7 @@ pub const Node = struct {
             return parser.DOMError.HierarchyRequest;
         }
 
-        const doc = (try parser.nodeOwnerDocument(self)) orelse return;
+        const doc = (parser.nodeOwnerDocument(self)) orelse return;
         for (nodes) |node| {
             _ = try parser.nodeAppendChild(self, try node.toNode(doc));
         }
@@ -525,7 +553,7 @@ pub const Node = struct {
         // remove existing children
         try removeChildren(self);
 
-        const doc = (try parser.nodeOwnerDocument(self)) orelse return;
+        const doc = (parser.nodeOwnerDocument(self)) orelse return;
         // add new children
         for (nodes) |node| {
             _ = try parser.nodeAppendChild(self, try node.toNode(doc));
@@ -533,30 +561,30 @@ pub const Node = struct {
     }
 
     pub fn removeChildren(self: *parser.Node) !void {
-        if (!try parser.nodeHasChildNodes(self)) return;
+        if (!parser.nodeHasChildNodes(self)) return;
 
         const children = try parser.nodeGetChildNodes(self);
-        const ln = try parser.nodeListLength(children);
+        const ln = parser.nodeListLength(children);
         var i: u32 = 0;
         while (i < ln) {
             defer i += 1;
             // we always retrieve the 0 index child on purpose: libdom nodelist
             // are dynamic. So the next child to remove is always as pos 0.
-            const child = try parser.nodeListItem(children, 0) orelse continue;
+            const child = parser.nodeListItem(children, 0) orelse continue;
             _ = try parser.nodeRemoveChild(self, child);
         }
     }
 
     pub fn before(self: *parser.Node, nodes: []const NodeOrText) !void {
-        const parent = try parser.nodeParentNode(self) orelse return;
-        const doc = (try parser.nodeOwnerDocument(parent)) orelse return;
+        const parent = parser.nodeParentNode(self) orelse return;
+        const doc = (parser.nodeOwnerDocument(parent)) orelse return;
 
         var sibling: ?*parser.Node = self;
         // have to find the first sibling that isn't in nodes
         CHECK: while (sibling) |s| {
             for (nodes) |n| {
                 if (n.is(s)) {
-                    sibling = try parser.nodePreviousSibling(s);
+                    sibling = parser.nodePreviousSibling(s);
                     continue :CHECK;
                 }
             }
@@ -564,7 +592,7 @@ pub const Node = struct {
         }
 
         if (sibling == null) {
-            sibling = try parser.nodeFirstChild(parent);
+            sibling = parser.nodeFirstChild(parent);
         }
 
         if (sibling) |ref_node| {
@@ -578,15 +606,15 @@ pub const Node = struct {
     }
 
     pub fn after(self: *parser.Node, nodes: []const NodeOrText) !void {
-        const parent = try parser.nodeParentNode(self) orelse return;
-        const doc = (try parser.nodeOwnerDocument(parent)) orelse return;
+        const parent = parser.nodeParentNode(self) orelse return;
+        const doc = (parser.nodeOwnerDocument(parent)) orelse return;
 
         // have to find the first sibling that isn't in nodes
-        var sibling = try parser.nodeNextSibling(self);
+        var sibling = parser.nodeNextSibling(self);
         CHECK: while (sibling) |s| {
             for (nodes) |n| {
                 if (n.is(s)) {
-                    sibling = try parser.nodeNextSibling(s);
+                    sibling = parser.nodeNextSibling(s);
                     continue :CHECK;
                 }
             }

src/browser/dom/node_filter.zig

@@ -17,8 +17,8 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
+const js = @import("../js/js.zig");
 const parser = @import("../netsurf.zig");
-const Env = @import("../env.zig").Env;
 const Node = @import("node.zig").Node;
 
 pub const NodeFilter = struct {
@@ -43,10 +43,13 @@ pub const NodeFilter = struct {
 
 const VerifyResult = enum { accept, skip, reject };
 
-pub fn verify(what_to_show: u32, filter: ?Env.Function, node: *parser.Node) !VerifyResult {
-    const node_type = try parser.nodeType(node);
+pub fn verify(what_to_show: u32, filter: ?js.Function, node: *parser.Node) !VerifyResult {
+    const node_type = parser.nodeType(node);
 
     // Verify that we can show this node type.
+    // Per the DOM spec, what_to_show filters which nodes to return, but should
+    // still traverse children. So we return .skip (not .reject) when the node
+    // type doesn't match.
     if (!switch (node_type) {
         .attribute => what_to_show & NodeFilter._SHOW_ATTRIBUTE != 0,
         .cdata_section => what_to_show & NodeFilter._SHOW_CDATA_SECTION != 0,
@@ -60,7 +63,7 @@ pub fn verify(what_to_show: u32, filter: ?Env.Function, node: *parser.Node) !Ver
         .notation => what_to_show & NodeFilter._SHOW_NOTATION != 0,
         .processing_instruction => what_to_show & NodeFilter._SHOW_PROCESSING_INSTRUCTION != 0,
         .text => what_to_show & NodeFilter._SHOW_TEXT != 0,
-    }) return .reject;
+    }) return .skip;
 
     // Verify that we aren't filtering it out.
     if (filter) |f| {

src/browser/dom/node_iterator.zig

@@ -18,8 +18,8 @@
 
 const std = @import("std");
 
+const js = @import("../js/js.zig");
 const parser = @import("../netsurf.zig");
-const Env = @import("../env.zig").Env;
 const NodeFilter = @import("node_filter.zig");
 const Node = @import("node.zig").Node;
 const NodeUnion = @import("node.zig").Union;
@@ -37,7 +37,7 @@ pub const NodeIterator = struct {
     reference_node: *parser.Node,
     what_to_show: u32,
     filter: ?NodeIteratorOpts,
-    filter_func: ?Env.Function,
+    filter_func: ?js.Function,
     pointer_before_current: bool = true,
     // used to track / block recursive filters
     is_in_callback: bool = false,
@@ -45,15 +45,15 @@ pub const NodeIterator = struct {
     // One of the few cases where null and undefined resolve to different default.
     // We need the raw JsObject so that we can probe the tri state:
     // null, undefined or i32.
-    pub const WhatToShow = Env.JsObject;
+    pub const WhatToShow = js.Object;
 
     pub const NodeIteratorOpts = union(enum) {
-        function: Env.Function,
-        object: struct { acceptNode: Env.Function },
+        function: js.Function,
+        object: struct { acceptNode: js.Function },
     };
 
     pub fn init(node: *parser.Node, what_to_show_: ?WhatToShow, filter: ?NodeIteratorOpts) !NodeIterator {
-        var filter_func: ?Env.Function = null;
+        var filter_func: ?js.Function = null;
         if (filter) |f| {
             filter_func = switch (f) {
                 .function => |func| func,
@@ -74,10 +74,10 @@ pub const NodeIterator = struct {
 
         return .{
             .root = node,
-            .reference_node = node,
-            .what_to_show = what_to_show,
             .filter = filter,
+            .reference_node = node,
             .filter_func = filter_func,
+            .what_to_show = what_to_show,
         };
     }
 
@@ -115,17 +115,30 @@ pub const NodeIterator = struct {
 
         if (try self.firstChild(self.reference_node)) |child| {
             self.reference_node = child;
+            self.pointer_before_current = false;
             return try Node.toInterface(child);
         }
 
         var current = self.reference_node;
         while (current != self.root) {
-            if (try self.nextSibling(current)) |sibling| {
-                self.reference_node = sibling;
-                return try Node.toInterface(sibling);
+            // Try to get next sibling (including .skip/.reject nodes we need to descend into)
+            if (try self.nextSiblingOrSkipReject(current)) |result| {
+                if (result.should_descend) {
+                    // This is a .skip/.reject node - try to find acceptable children within it
+                    if (try self.firstChild(result.node)) |child| {
+                        self.reference_node = child;
+                        return try Node.toInterface(child);
+                    }
+                    // No acceptable children, continue looking at this node's siblings
+                    current = result.node;
+                    continue;
+                }
+                // This is an .accept node - return it
+                self.reference_node = result.node;
+                return try Node.toInterface(result.node);
             }
 
-            current = (try parser.nodeParentNode(current)) orelse break;
+            current = (parser.nodeParentNode(current)) orelse break;
         }
 
         return null;
@@ -147,7 +160,7 @@ pub const NodeIterator = struct {
         }
 
         var current = self.reference_node;
-        while (try parser.nodePreviousSibling(current)) |previous| {
+        while (parser.nodePreviousSibling(current)) |previous| {
             current = previous;
 
             switch (try NodeFilter.verify(self.what_to_show, self.filter_func, current)) {
@@ -189,11 +202,11 @@ pub const NodeIterator = struct {
 
     fn firstChild(self: *const NodeIterator, node: *parser.Node) !?*parser.Node {
         const children = try parser.nodeGetChildNodes(node);
-        const child_count = try parser.nodeListLength(children);
+        const child_count = parser.nodeListLength(children);
 
         for (0..child_count) |i| {
             const index: u32 = @intCast(i);
-            const child = (try parser.nodeListItem(children, index)) orelse return null;
+            const child = (parser.nodeListItem(children, index)) orelse return null;
 
             switch (try NodeFilter.verify(self.what_to_show, self.filter_func, child)) {
                 .accept => return child, // NOTE: Skip and reject are equivalent for NodeIterator, this is different from TreeWalker
@@ -206,12 +219,12 @@ pub const NodeIterator = struct {
 
     fn lastChild(self: *const NodeIterator, node: *parser.Node) !?*parser.Node {
         const children = try parser.nodeGetChildNodes(node);
-        const child_count = try parser.nodeListLength(children);
+        const child_count = parser.nodeListLength(children);
 
         var index: u32 = child_count;
         while (index > 0) {
             index -= 1;
-            const child = (try parser.nodeListItem(children, index)) orelse return null;
+            const child = (parser.nodeListItem(children, index)) orelse return null;
 
             switch (try NodeFilter.verify(self.what_to_show, self.filter_func, child)) {
                 .accept => return child, // NOTE: Skip and reject are equivalent for NodeIterator, this is different from TreeWalker
@@ -229,7 +242,7 @@ pub const NodeIterator = struct {
         var current = node;
         while (true) {
             if (current == self.root) return null;
-            current = (try parser.nodeParentNode(current)) orelse return null;
+            current = (parser.nodeParentNode(current)) orelse return null;
 
             switch (try NodeFilter.verify(self.what_to_show, self.filter_func, current)) {
                 .accept => return current,
@@ -243,7 +256,7 @@ pub const NodeIterator = struct {
         var current = node;
 
         while (true) {
-            current = (try parser.nodeNextSibling(current)) orelse return null;
+            current = (parser.nodeNextSibling(current)) orelse return null;
 
             switch (try NodeFilter.verify(self.what_to_show, self.filter_func, current)) {
                 .accept => return current,
@@ -254,6 +267,22 @@ pub const NodeIterator = struct {
         return null;
     }
 
+    // Get the next sibling that is either acceptable or should be descended into (skip/reject)
+    fn nextSiblingOrSkipReject(self: *const NodeIterator, node: *parser.Node) !?struct { node: *parser.Node, should_descend: bool } {
+        var current = node;
+
+        while (true) {
+            current = (parser.nodeNextSibling(current)) orelse return null;
+
+            switch (try NodeFilter.verify(self.what_to_show, self.filter_func, current)) {
+                .accept => return .{ .node = current, .should_descend = false },
+                .skip, .reject => return .{ .node = current, .should_descend = true },
+            }
+        }
+
+        return null;
+    }
+
     fn callbackStart(self: *NodeIterator) !void {
         if (self.is_in_callback) {
             // this is the correct DOMExeption

src/browser/dom/nodelist.zig

@@ -17,13 +17,12 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
+const Allocator = std.mem.Allocator;
 
+const js = @import("../js/js.zig");
 const log = @import("../../log.zig");
 const parser = @import("../netsurf.zig");
 
-const JsThis = @import("../env.zig").JsThis;
-const Function = @import("../env.zig").Function;
-
 const NodeUnion = @import("node.zig").Union;
 const Node = @import("node.zig").Node;
 
@@ -101,13 +100,20 @@ pub const NodeList = struct {
 
     nodes: NodesArrayList = .{},
 
-    pub fn deinit(self: *NodeList, alloc: std.mem.Allocator) void {
-        // TODO unref all nodes
-        self.nodes.deinit(alloc);
+    pub fn deinit(self: *NodeList, allocator: Allocator) void {
+        self.nodes.deinit(allocator);
     }
 
-    pub fn append(self: *NodeList, alloc: std.mem.Allocator, node: *parser.Node) !void {
-        try self.nodes.append(alloc, node);
+    pub fn ensureTotalCapacity(self: *NodeList, allocator: Allocator, n: usize) !void {
+        return self.nodes.ensureTotalCapacity(allocator, n);
+    }
+
+    pub fn append(self: *NodeList, allocator: Allocator, node: *parser.Node) !void {
+        try self.nodes.append(allocator, node);
+    }
+
+    pub fn appendAssumeCapacity(self: *NodeList, node: *parser.Node) void {
+        self.nodes.appendAssumeCapacity(node);
     }
 
     pub fn get_length(self: *const NodeList) u32 {
@@ -140,10 +146,10 @@ pub const NodeList = struct {
     //     };
     // }
 
-    pub fn _forEach(self: *NodeList, cbk: Function) !void { // TODO handle thisArg
+    pub fn _forEach(self: *NodeList, cbk: js.Function) !void { // TODO handle thisArg
         for (self.nodes.items, 0..) |n, i| {
             const ii: u32 = @intCast(i);
-            var result: Function.Result = undefined;
+            var result: js.Function.Result = undefined;
             cbk.tryCall(void, .{ n, ii, self }, &result) catch {
                 log.debug(.user_script, "forEach callback", .{ .err = result.exception, .stack = result.stack });
             };
@@ -167,7 +173,7 @@ pub const NodeList = struct {
     }
 
     // TODO entries() https://developer.mozilla.org/en-US/docs/Web/API/NodeList/entries
-    pub fn postAttach(self: *NodeList, js_this: JsThis) !void {
+    pub fn postAttach(self: *NodeList, js_this: js.This) !void {
         const len = self.get_length();
         for (0..len) |i| {
             const node = try self._item(@intCast(i)) orelse unreachable;

src/browser/dom/performance.zig

@@ -18,9 +18,9 @@
 
 const std = @import("std");
 
+const js = @import("../js/js.zig");
 const parser = @import("../netsurf.zig");
 const EventTarget = @import("../dom/event_target.zig").EventTarget;
-const Env = @import("../env.zig").Env;
 const Page = @import("../page.zig").Page;
 
 const milliTimestamp = @import("../../datetime.zig").milliTimestamp;
@@ -61,7 +61,7 @@ pub const Performance = struct {
         return milliTimestamp() - self.time_origin;
     }
 
-    pub fn _mark(_: *Performance, name: []const u8, _options: ?PerformanceMark.Options, page: *Page) !PerformanceMark {
+    pub fn _mark(_: *Performance, name: js.String, _options: ?PerformanceMark.Options, page: *Page) !PerformanceMark {
         const mark: PerformanceMark = try .constructor(name, _options, page);
         // TODO: Should store this in an entries list
         return mark;
@@ -148,14 +148,14 @@ pub const PerformanceMark = struct {
     pub const prototype = *PerformanceEntry;
 
     proto: PerformanceEntry,
-    detail: ?Env.JsObject,
+    detail: ?js.Object,
 
     const Options = struct {
-        detail: ?Env.JsObject = null,
+        detail: ?js.Object = null,
         startTime: ?f64 = null,
     };
 
-    pub fn constructor(name: []const u8, _options: ?Options, page: *Page) !PerformanceMark {
+    pub fn constructor(name: js.String, _options: ?Options, page: *Page) !PerformanceMark {
         const perf = &page.window.performance;
 
         const options = _options orelse Options{};
@@ -166,14 +166,12 @@ pub const PerformanceMark = struct {
         }
 
         const detail = if (options.detail) |d| try d.persist() else null;
-
-        const duped_name = try page.arena.dupe(u8, name);
-        const proto = PerformanceEntry{ .name = duped_name, .entry_type = .mark, .start_time = start_time };
+        const proto = PerformanceEntry{ .name = name.string, .entry_type = .mark, .start_time = start_time };
 
         return .{ .proto = proto, .detail = detail };
     }
 
-    pub fn get_detail(self: *const PerformanceMark) ?Env.JsObject {
+    pub fn get_detail(self: *const PerformanceMark) ?js.Object {
         return self.detail;
     }
 };
@@ -197,7 +195,7 @@ test "Performance: now" {
     }
 
     var after = perf._now();
-    while (after <= now) { // Loop untill after > now
+    while (after <= now) { // Loop until after > now
         try testing.expectEqual(after, now);
         after = perf._now();
     }

src/browser/dom/performance_observer.zig

@@ -17,7 +17,7 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
-const Env = @import("../env.zig").Env;
+const js = @import("../js/js.zig");
 
 const PerformanceEntry = @import("performance.zig").PerformanceEntry;
 
@@ -25,7 +25,7 @@ const PerformanceEntry = @import("performance.zig").PerformanceEntry;
 pub const PerformanceObserver = struct {
     pub const _supportedEntryTypes = [0][]const u8{};
 
-    pub fn constructor(cbk: Env.Function) PerformanceObserver {
+    pub fn constructor(cbk: js.Function) PerformanceObserver {
         _ = cbk;
         return .{};
     }

src/browser/dom/processing_instruction.zig

@@ -48,7 +48,7 @@ pub const ProcessingInstruction = struct {
     }
 
     pub fn get_data(self: *parser.ProcessingInstruction) !?[]const u8 {
-        return try parser.nodeValue(parser.processingInstructionToNode(self));
+        return parser.nodeValue(parser.processingInstructionToNode(self));
     }
 
     pub fn set_data(self: *parser.ProcessingInstruction, data: []u8) !void {
@@ -58,7 +58,7 @@ pub const ProcessingInstruction = struct {
     // netsurf's ProcessInstruction doesn't implement the dom_node_get_attributes
     // and thus will crash if we try to call nodeIsEqualNode.
     pub fn _isEqualNode(self: *parser.ProcessingInstruction, other_node: *parser.Node) !bool {
-        if (try parser.nodeType(other_node) != .processing_instruction) {
+        if (parser.nodeType(other_node) != .processing_instruction) {
             return false;
         }
 

src/browser/dom/range.zig

@@ -92,7 +92,7 @@ pub const Range = struct {
     pub fn _setStart(self: *Range, node: *parser.Node, offset_: i32) !void {
         try ensureValidOffset(node, offset_);
         const offset: u32 = @intCast(offset_);
-        const position = compare(node, offset, self.proto.start_node, self.proto.start_offset) catch |err| switch (err) {
+        const position = compare(node, offset, self.proto.end_node, self.proto.end_offset) catch |err| switch (err) {
             error.WrongDocument => blk: {
                 // allow a node with a different root than the current, or
                 // a disconnected one. Treat it as if it's "after", so that
@@ -103,7 +103,7 @@ pub const Range = struct {
         };
 
         if (position == 1) {
-            // if we're setting the node after the current start, the end must
+            // if we're setting the node after the current end, the end must
             // be set too.
             self.proto.end_offset = offset;
             self.proto.end_node = node;
@@ -176,10 +176,10 @@ pub const Range = struct {
         self.proto.end_node = node;
 
         // Set end_offset
-        switch (try parser.nodeType(node)) {
+        switch (parser.nodeType(node)) {
             .text, .cdata_section, .comment, .processing_instruction => {
                 // For text-like nodes, end_offset should be the length of the text data
-                if (try parser.nodeValue(node)) |text_data| {
+                if (parser.nodeValue(node)) |text_data| {
                     self.proto.end_offset = @intCast(text_data.len);
                 } else {
                     self.proto.end_offset = 0;
@@ -188,7 +188,7 @@ pub const Range = struct {
             else => {
                 // For element and other nodes, end_offset is the number of children
                 const child_nodes = try parser.nodeGetChildNodes(node);
-                const child_count = try parser.nodeListLength(child_nodes);
+                const child_count = parser.nodeListLength(child_nodes);
                 self.proto.end_offset = @intCast(child_count);
             },
         }
@@ -211,7 +211,7 @@ pub const Range = struct {
 
     pub fn _comparePoint(self: *const Range, node: *parser.Node, offset_: i32) !i32 {
         const start = self.proto.start_node;
-        if (try parser.nodeGetRootNode(start) != try parser.nodeGetRootNode(node)) {
+        if (parser.nodeGetRootNode(start) != parser.nodeGetRootNode(node)) {
             // WPT really wants this error to be first. Later, when we check
             // if the relative position is 'disconnected', it'll also catch this
             // case, but WPT will complain because it sometimes also sends
@@ -219,7 +219,7 @@ pub const Range = struct {
             return error.WrongDocument;
         }
 
-        if (try parser.nodeType(node) == .document_type) {
+        if (parser.nodeType(node) == .document_type) {
             return error.InvalidNodeType;
         }
 
@@ -245,8 +245,8 @@ pub const Range = struct {
     }
 
     pub fn _intersectsNode(self: *const Range, node: *parser.Node) !bool {
-        const start_root = try parser.nodeGetRootNode(self.proto.start_node);
-        const node_root = try parser.nodeGetRootNode(node);
+        const start_root = parser.nodeGetRootNode(self.proto.start_node);
+        const node_root = parser.nodeGetRootNode(node);
         if (start_root != node_root) {
             return false;
         }
@@ -299,29 +299,29 @@ fn ensureValidOffset(node: *parser.Node, offset: i32) !void {
 
 fn nodeLength(node: *parser.Node) !usize {
     switch (try isTextual(node)) {
-        true => return ((try parser.nodeTextContent(node)) orelse "").len,
+        true => return ((parser.nodeTextContent(node)) orelse "").len,
         false => {
             const children = try parser.nodeGetChildNodes(node);
-            return @intCast(try parser.nodeListLength(children));
+            return @intCast(parser.nodeListLength(children));
         },
     }
 }
 
 fn isTextual(node: *parser.Node) !bool {
-    return switch (try parser.nodeType(node)) {
+    return switch (parser.nodeType(node)) {
         .text, .comment, .cdata_section => true,
         else => false,
     };
 }
 
 fn getParentAndIndex(child: *parser.Node) !struct { *parser.Node, u32 } {
-    const parent = (try parser.nodeParentNode(child)) orelse return error.InvalidNodeType;
+    const parent = (parser.nodeParentNode(child)) orelse return error.InvalidNodeType;
     const children = try parser.nodeGetChildNodes(parent);
-    const ln = try parser.nodeListLength(children);
+    const ln = parser.nodeListLength(children);
     var i: u32 = 0;
     while (i < ln) {
         defer i += 1;
-        const c = try parser.nodeListItem(children, i) orelse continue;
+        const c = parser.nodeListItem(children, i) orelse continue;
         if (c == child) {
             return .{ parent, i };
         }
@@ -363,7 +363,7 @@ fn compare(node_a: *parser.Node, offset_a: u32, node_b: *parser.Node, offset_b:
     if (position & @intFromEnum(parser.DocumentPosition.contains) == @intFromEnum(parser.DocumentPosition.contains)) {
         // node_a contains node_b
         var child = node_b;
-        while (try parser.nodeParentNode(child)) |parent| {
+        while (parser.nodeParentNode(child)) |parent| {
             if (parent == node_a) {
                 // child.parentNode == node_a
                 break;
@@ -378,7 +378,7 @@ fn compare(node_a: *parser.Node, offset_a: u32, node_b: *parser.Node, offset_b:
 
         const child_parent, const child_index = try getParentAndIndex(child);
         std.debug.assert(node_a == child_parent);
-        return if (child_index < offset_a) -1 else 1;
+        return if (offset_a <= child_index) -1 else 1;
     }
 
     return -1;

src/browser/dom/resize_observer.zig

@@ -16,7 +16,7 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-const Env = @import("../env.zig").Env;
+const js = @import("../js/js.zig");
 const parser = @import("../netsurf.zig");
 
 pub const Interfaces = .{
@@ -25,7 +25,7 @@ pub const Interfaces = .{
 
 // WEB IDL https://drafts.csswg.org/resize-observer/#resize-observer-interface
 pub const ResizeObserver = struct {
-    pub fn constructor(cbk: Env.Function) ResizeObserver {
+    pub fn constructor(cbk: js.Function) ResizeObserver {
         _ = cbk;
         return .{};
     }

src/browser/dom/shadow_root.zig

@@ -20,7 +20,7 @@ const std = @import("std");
 const dump = @import("../dump.zig");
 const parser = @import("../netsurf.zig");
 
-const Env = @import("../env.zig").Env;
+const js = @import(".././js/js.zig");
 const Page = @import("../page.zig").Page;
 const Node = @import("node.zig").Node;
 const Element = @import("element.zig").Element;
@@ -34,7 +34,7 @@ pub const ShadowRoot = struct {
     mode: Mode,
     host: *parser.Element,
     proto: *parser.DocumentFragment,
-    adopted_style_sheets: ?Env.JsObject = null,
+    adopted_style_sheets: ?js.Object = null,
 
     pub const Mode = enum {
         open,
@@ -45,17 +45,17 @@ pub const ShadowRoot = struct {
         return Element.toInterface(self.host);
     }
 
-    pub fn get_adoptedStyleSheets(self: *ShadowRoot, page: *Page) !Env.JsObject {
+    pub fn get_adoptedStyleSheets(self: *ShadowRoot, page: *Page) !js.Object {
         if (self.adopted_style_sheets) |obj| {
             return obj;
         }
 
-        const obj = try page.main_context.newArray(0).persist();
+        const obj = try page.js.createArray(0).persist();
         self.adopted_style_sheets = obj;
         return obj;
     }
 
-    pub fn set_adoptedStyleSheets(self: *ShadowRoot, sheets: Env.JsObject) !void {
+    pub fn set_adoptedStyleSheets(self: *ShadowRoot, sheets: js.Object) !void {
         self.adopted_style_sheets = try sheets.persist();
     }
 
@@ -67,7 +67,7 @@ pub const ShadowRoot = struct {
 
     pub fn set_innerHTML(self: *ShadowRoot, str_: ?[]const u8) !void {
         const sr_doc = parser.documentFragmentToNode(self.proto);
-        const doc = try parser.nodeOwnerDocument(sr_doc) orelse return parser.DOMError.WrongDocument;
+        const doc = parser.nodeOwnerDocument(sr_doc) orelse return parser.DOMError.WrongDocument;
         try Node.removeChildren(sr_doc);
         const str = str_ orelse return;
 
@@ -80,16 +80,16 @@ pub const ShadowRoot = struct {
         // element.
         // For ShadowRoot, it appears the only the children within the body should
         // be set.
-        const html = try parser.nodeFirstChild(fragment_node) orelse return;
-        const head = try parser.nodeFirstChild(html) orelse return;
-        const body = try parser.nodeNextSibling(head) orelse return;
+        const html = parser.nodeFirstChild(fragment_node) orelse return;
+        const head = parser.nodeFirstChild(html) orelse return;
+        const body = parser.nodeNextSibling(head) orelse return;
 
         const children = try parser.nodeGetChildNodes(body);
-        const ln = try parser.nodeListLength(children);
+        const ln = parser.nodeListLength(children);
         for (0..ln) |_| {
             // always index 0, because nodeAppendChild moves the node out of
             // the nodeList and into the new tree
-            const child = try parser.nodeListItem(children, 0) orelse continue;
+            const child = parser.nodeListItem(children, 0) orelse continue;
             _ = try parser.nodeAppendChild(sr_doc, child);
         }
     }

src/browser/dom/token_list.zig

@@ -18,12 +18,11 @@
 
 const std = @import("std");
 
+const js = @import("../js/js.zig");
 const log = @import("../../log.zig");
 const parser = @import("../netsurf.zig");
 const iterator = @import("../iterator/iterator.zig");
 
-const Function = @import("../env.zig").Function;
-const JsObject = @import("../env.zig").JsObject;
 const DOMException = @import("exceptions.zig").DOMException;
 
 pub const Interfaces = .{
@@ -137,10 +136,10 @@ pub const DOMTokenList = struct {
     }
 
     // TODO handle thisArg
-    pub fn _forEach(self: *parser.TokenList, cbk: Function, this_arg: JsObject) !void {
+    pub fn _forEach(self: *parser.TokenList, cbk: js.Function, this_arg: js.Object) !void {
         var entries = _entries(self);
         while (try entries._next()) |entry| {
-            var result: Function.Result = undefined;
+            var result: js.Function.Result = undefined;
             cbk.tryCallWithThis(void, this_arg, .{ entry.@"1", entry.@"0", self }, &result) catch {
                 log.debug(.user_script, "callback error", .{
                     .err = result.exception,

src/browser/dom/tree_walker.zig

@@ -17,11 +17,10 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
+const js = @import("../js/js.zig");
 const parser = @import("../netsurf.zig");
 
 const NodeFilter = @import("node_filter.zig");
-const Env = @import("../env.zig").Env;
-const Page = @import("../page.zig").Page;
 const Node = @import("node.zig").Node;
 const NodeUnion = @import("node.zig").Union;
 
@@ -31,20 +30,20 @@ pub const TreeWalker = struct {
     current_node: *parser.Node,
     what_to_show: u32,
     filter: ?TreeWalkerOpts,
-    filter_func: ?Env.Function,
+    filter_func: ?js.Function,
 
     // One of the few cases where null and undefined resolve to different default.
     // We need the raw JsObject so that we can probe the tri state:
     // null, undefined or i32.
-    pub const WhatToShow = Env.JsObject;
+    pub const WhatToShow = js.Object;
 
     pub const TreeWalkerOpts = union(enum) {
-        function: Env.Function,
-        object: struct { acceptNode: Env.Function },
+        function: js.Function,
+        object: struct { acceptNode: js.Function },
     };
 
     pub fn init(node: *parser.Node, what_to_show_: ?WhatToShow, filter: ?TreeWalkerOpts) !TreeWalker {
-        var filter_func: ?Env.Function = null;
+        var filter_func: ?js.Function = null;
 
         if (filter) |f| {
             filter_func = switch (f) {
@@ -95,11 +94,11 @@ pub const TreeWalker = struct {
 
     fn firstChild(self: *const TreeWalker, node: *parser.Node) !?*parser.Node {
         const children = try parser.nodeGetChildNodes(node);
-        const child_count = try parser.nodeListLength(children);
+        const child_count = parser.nodeListLength(children);
 
         for (0..child_count) |i| {
             const index: u32 = @intCast(i);
-            const child = (try parser.nodeListItem(children, index)) orelse return null;
+            const child = (parser.nodeListItem(children, index)) orelse return null;
 
             switch (try NodeFilter.verify(self.what_to_show, self.filter_func, child)) {
                 .accept => return child,
@@ -113,12 +112,12 @@ pub const TreeWalker = struct {
 
     fn lastChild(self: *const TreeWalker, node: *parser.Node) !?*parser.Node {
         const children = try parser.nodeGetChildNodes(node);
-        const child_count = try parser.nodeListLength(children);
+        const child_count = parser.nodeListLength(children);
 
         var index: u32 = child_count;
         while (index > 0) {
             index -= 1;
-            const child = (try parser.nodeListItem(children, index)) orelse return null;
+            const child = (parser.nodeListItem(children, index)) orelse return null;
 
             switch (try NodeFilter.verify(self.what_to_show, self.filter_func, child)) {
                 .accept => return child,
@@ -134,7 +133,7 @@ pub const TreeWalker = struct {
         var current = node;
 
         while (true) {
-            current = (try parser.nodeNextSibling(current)) orelse return null;
+            current = (parser.nodeNextSibling(current)) orelse return null;
 
             switch (try NodeFilter.verify(self.what_to_show, self.filter_func, current)) {
                 .accept => return current,
@@ -145,11 +144,28 @@ pub const TreeWalker = struct {
         return null;
     }
 
+    // Get the next sibling that is either acceptable or should be descended into (skip)
+    fn nextSiblingOrSkip(self: *const TreeWalker, node: *parser.Node) !?struct { node: *parser.Node, should_descend: bool } {
+        var current = node;
+
+        while (true) {
+            current = (parser.nodeNextSibling(current)) orelse return null;
+
+            switch (try NodeFilter.verify(self.what_to_show, self.filter_func, current)) {
+                .accept => return .{ .node = current, .should_descend = false },
+                .skip => return .{ .node = current, .should_descend = true },
+                .reject => continue,
+            }
+        }
+
+        return null;
+    }
+
     fn previousSibling(self: *const TreeWalker, node: *parser.Node) !?*parser.Node {
         var current = node;
 
         while (true) {
-            current = (try parser.nodePreviousSibling(current)) orelse return null;
+            current = (parser.nodePreviousSibling(current)) orelse return null;
 
             switch (try NodeFilter.verify(self.what_to_show, self.filter_func, current)) {
                 .accept => return current,
@@ -166,7 +182,7 @@ pub const TreeWalker = struct {
         var current = node;
         while (true) {
             if (current == self.root) return null;
-            current = (try parser.nodeParentNode(current)) orelse return null;
+            current = (parser.nodeParentNode(current)) orelse return null;
 
             switch (try NodeFilter.verify(self.what_to_show, self.filter_func, current)) {
                 .accept => return current,
@@ -194,19 +210,36 @@ pub const TreeWalker = struct {
     }
 
     pub fn _nextNode(self: *TreeWalker) !?NodeUnion {
-        if (try self.firstChild(self.current_node)) |child| {
+        var current = self.current_node;
+
+        // First, try to go to first child of current node
+        if (try self.firstChild(current)) |child| {
             self.current_node = child;
             return try Node.toInterface(child);
         }
 
-        var current = self.current_node;
+        // No acceptable children, move to next node in tree
         while (current != self.root) {
-            if (try self.nextSibling(current)) |sibling| {
-                self.current_node = sibling;
-                return try Node.toInterface(sibling);
+            const result = try self.nextSiblingOrSkip(current) orelse {
+                // No next sibling, go up to parent and continue
+                // or, if there is no parent, we're done
+                current = (parser.nodeParentNode(current)) orelse break;
+                continue;
+            };
+
+            if (!result.should_descend) {
+                // This is an .accept node - return it
+                self.current_node = result.node;
+                return try Node.toInterface(result.node);
             }
 
-            current = (try parser.nodeParentNode(current)) orelse break;
+            // This is a .skip node - try to find acceptable children within it
+            if (try self.firstChild(result.node)) |child| {
+                self.current_node = child;
+                return try Node.toInterface(child);
+            }
+            // No acceptable children, continue looking at this node's siblings
+            current = result.node;
         }
 
         return null;
@@ -234,7 +267,7 @@ pub const TreeWalker = struct {
         if (self.current_node == self.root) return null;
 
         var current = self.current_node;
-        while (try parser.nodePreviousSibling(current)) |previous| {
+        while (parser.nodePreviousSibling(current)) |previous| {
             current = previous;
 
             switch (try NodeFilter.verify(self.what_to_show, self.filter_func, current)) {

src/browser/dom/walker.zig

@@ -44,39 +44,39 @@ pub const WalkerDepthFirst = struct {
         var n = cur orelse root;
 
         // TODO deinit next
-        if (try parser.nodeFirstChild(n)) |next| {
+        if (parser.nodeFirstChild(n)) |next| {
             return next;
         }
 
         // TODO deinit next
-        if (try parser.nodeNextSibling(n)) |next| {
+        if (parser.nodeNextSibling(n)) |next| {
             return next;
         }
 
         // TODO deinit parent
         // Back to the parent of cur.
         // If cur has no parent, then the iteration is over.
-        var parent = try parser.nodeParentNode(n) orelse return null;
+        var parent = parser.nodeParentNode(n) orelse return null;
 
         // TODO deinit lastchild
-        var lastchild = try parser.nodeLastChild(parent);
+        var lastchild = parser.nodeLastChild(parent);
         while (n != root and n == lastchild) {
             n = parent;
 
             // TODO deinit parent
             // Back to the prev's parent.
             // If prev has no parent, then the loop must stop.
-            parent = try parser.nodeParentNode(n) orelse break;
+            parent = parser.nodeParentNode(n) orelse break;
 
             // TODO deinit lastchild
-            lastchild = try parser.nodeLastChild(parent);
+            lastchild = parser.nodeLastChild(parent);
         }
 
         if (n == root) {
             return null;
         }
 
-        return try parser.nodeNextSibling(n);
+        return parser.nodeNextSibling(n);
     }
 };
 
@@ -84,14 +84,14 @@ pub const WalkerDepthFirst = struct {
 pub const WalkerChildren = struct {
     pub fn get_next(_: WalkerChildren, root: *parser.Node, cur: ?*parser.Node) !?*parser.Node {
         // On walk start, we return the first root's child.
-        if (cur == null) return try parser.nodeFirstChild(root);
+        if (cur == null) return parser.nodeFirstChild(root);
 
         // If cur is root, then return null.
         // This is a special case, if the root is included in the walk, we
         // don't want to go further to find children.
         if (root == cur.?) return null;
 
-        return try parser.nodeNextSibling(cur.?);
+        return parser.nodeNextSibling(cur.?);
     }
 };
 

src/browser/dump.zig

@@ -26,7 +26,13 @@ pub const Opts = struct {
     // set to include element shadowroots in the dump
     page: ?*const Page = null,
 
-    exclude_scripts: bool = false,
+    strip_mode: StripMode = .{},
+
+    pub const StripMode = struct {
+        js: bool = false,
+        ui: bool = false,
+        css: bool = false,
+    };
 };
 
 // writer must be a std.io.Writer
@@ -41,8 +47,8 @@ pub fn writeDocType(doc_type: *parser.DocumentType, writer: *std.Io.Writer) !voi
     try writer.writeAll("<!DOCTYPE ");
     try writer.writeAll(try parser.documentTypeGetName(doc_type));
 
-    const public_id = try parser.documentTypeGetPublicId(doc_type);
-    const system_id = try parser.documentTypeGetSystemId(doc_type);
+    const public_id = parser.documentTypeGetPublicId(doc_type);
+    const system_id = parser.documentTypeGetSystemId(doc_type);
     if (public_id.len != 0 and system_id.len != 0) {
         try writer.writeAll(" PUBLIC \"");
         try writeEscapedAttributeValue(writer, public_id);
@@ -63,11 +69,11 @@ pub fn writeDocType(doc_type: *parser.DocumentType, writer: *std.Io.Writer) !voi
 }
 
 pub fn writeNode(node: *parser.Node, opts: Opts, writer: *std.Io.Writer) anyerror!void {
-    switch (try parser.nodeType(node)) {
+    switch (parser.nodeType(node)) {
         .element => {
             // open the tag
             const tag_type = try parser.nodeHTMLGetTagType(node) orelse .undef;
-            if (opts.exclude_scripts and try isScriptOrRelated(tag_type, node)) {
+            if (try isStripped(tag_type, node, opts.strip_mode)) {
                 return;
             }
 
@@ -104,7 +110,7 @@ pub fn writeNode(node: *parser.Node, opts: Opts, writer: *std.Io.Writer) anyerro
             if (try isVoid(parser.nodeToElement(node))) return;
 
             if (tag_type == .script) {
-                try writer.writeAll(try parser.nodeTextContent(node) orelse "");
+                try writer.writeAll(parser.nodeTextContent(node) orelse "");
             } else {
                 // write the children
                 // TODO avoid recursion
@@ -117,17 +123,17 @@ pub fn writeNode(node: *parser.Node, opts: Opts, writer: *std.Io.Writer) anyerro
             try writer.writeAll(">");
         },
         .text => {
-            const v = try parser.nodeValue(node) orelse return;
+            const v = parser.nodeValue(node) orelse return;
             try writeEscapedTextNode(writer, v);
         },
         .cdata_section => {
-            const v = try parser.nodeValue(node) orelse return;
+            const v = parser.nodeValue(node) orelse return;
             try writer.writeAll("<![CDATA[");
             try writer.writeAll(v);
             try writer.writeAll("]]>");
         },
         .comment => {
-            const v = try parser.nodeValue(node) orelse return;
+            const v = parser.nodeValue(node) orelse return;
             try writer.writeAll("<!--");
             try writer.writeAll(v);
             try writer.writeAll("-->");
@@ -159,9 +165,22 @@ pub fn writeChildren(root: *parser.Node, opts: Opts, writer: *std.Io.Writer) !vo
     }
 }
 
-// When `exclude_scripts` is passed to dump, we don't include <script> tags.
-// We also want to omit <link rel=preload as=ascript>
-fn isScriptOrRelated(tag_type: parser.Tag, node: *parser.Node) !bool {
+fn isStripped(tag_type: parser.Tag, node: *parser.Node, strip_mode: Opts.StripMode) !bool {
+    if (strip_mode.js and try isJsRelated(tag_type, node)) {
+        return true;
+    }
+
+    if (strip_mode.css and try isCssRelated(tag_type, node)) {
+        return true;
+    }
+
+    if (strip_mode.ui and try isUIRelated(tag_type, node)) {
+        return true;
+    }
+    return false;
+}
+
+fn isJsRelated(tag_type: parser.Tag, node: *parser.Node) !bool {
     if (tag_type == .script) {
         return true;
     }
@@ -178,6 +197,34 @@ fn isScriptOrRelated(tag_type: parser.Tag, node: *parser.Node) !bool {
     return false;
 }
 
+fn isCssRelated(tag_type: parser.Tag, node: *parser.Node) !bool {
+    if (tag_type == .style) {
+        return true;
+    }
+    if (tag_type == .link) {
+        const el = parser.nodeToElement(node);
+        const rel = try parser.elementGetAttribute(el, "rel") orelse return false;
+        return std.ascii.eqlIgnoreCase(rel, "stylesheet");
+    }
+    return false;
+}
+
+fn isUIRelated(tag_type: parser.Tag, node: *parser.Node) !bool {
+    if (try isCssRelated(tag_type, node)) {
+        return true;
+    }
+    if (tag_type == .img or tag_type == .picture or tag_type == .video) {
+        return true;
+    }
+    if (tag_type == .undef) {
+        const name = try parser.nodeLocalName(node);
+        if (std.mem.eql(u8, name, "svg")) {
+            return true;
+        }
+    }
+    return false;
+}
+
 // area, base, br, col, embed, hr, img, input, link, meta, source, track, wbr
 // https://html.spec.whatwg.org/#void-elements
 fn isVoid(elem: *parser.Element) !bool {
@@ -189,10 +236,10 @@ fn isVoid(elem: *parser.Element) !bool {
     };
 }
 
-fn writeEscapedTextNode(writer: anytype, value: []const u8) !void {
+fn writeEscapedTextNode(writer: *std.Io.Writer, value: []const u8) !void {
     var v = value;
     while (v.len > 0) {
-        const index = std.mem.indexOfAnyPos(u8, v, 0, &.{ '&', '<', '>' }) orelse {
+        const index = std.mem.indexOfAnyPos(u8, v, 0, &.{ '&', '<', '>', 194 }) orelse {
             return writer.writeAll(v);
         };
         try writer.writeAll(v[0..index]);
@@ -200,13 +247,22 @@ fn writeEscapedTextNode(writer: anytype, value: []const u8) !void {
             '&' => try writer.writeAll("&amp;"),
             '<' => try writer.writeAll("&lt;"),
             '>' => try writer.writeAll("&gt;"),
+            194 => {
+                // non breaking space
+                if (v.len > index + 1 and v[index + 1] == 160) {
+                    try writer.writeAll("&nbsp;");
+                    v = v[index + 2 ..];
+                    continue;
+                }
+                try writer.writeByte(194);
+            },
             else => unreachable,
         }
         v = v[index + 1 ..];
     }
 }
 
-fn writeEscapedAttributeValue(writer: anytype, value: []const u8) !void {
+fn writeEscapedAttributeValue(writer: *std.Io.Writer, value: []const u8) !void {
     var v = value;
     while (v.len > 0) {
         const index = std.mem.indexOfAnyPos(u8, v, 0, &.{ '&', '<', '>', '"' }) orelse {
@@ -226,7 +282,7 @@ fn writeEscapedAttributeValue(writer: anytype, value: []const u8) !void {
 
 const testing = std.testing;
 test "dump.writeHTML" {
-    try parser.init();
+    parser.init();
     defer parser.deinit();
 
     try testWriteHTML(

src/browser/encoding/TextDecoder.zig

@@ -19,7 +19,6 @@
 const std = @import("std");
 const log = @import("../../log.zig");
 
-const Env = @import("../env.zig").Env;
 const Page = @import("../page.zig").Page;
 
 // https://encoding.spec.whatwg.org/#interface-textdecoder
@@ -70,8 +69,8 @@ pub fn get_fatal(self: *const TextDecoder) bool {
 const DecodeOptions = struct {
     stream: bool = false,
 };
-pub fn _decode(self: *TextDecoder, input_: ?[]const u8, opts_: ?DecodeOptions, page: *Page) ![]const u8 {
-    var str = input_ orelse return "";
+pub fn _decode(self: *TextDecoder, str_: ?[]const u8, opts_: ?DecodeOptions, page: *Page) ![]const u8 {
+    var str = str_ orelse return "";
     const opts: DecodeOptions = opts_ orelse .{};
 
     if (self.stream.items.len > 0) {

src/browser/encoding/TextEncoder.zig

@@ -18,7 +18,7 @@
 
 const std = @import("std");
 
-const Env = @import("../env.zig").Env;
+const js = @import("../js/js.zig");
 
 // https://encoding.spec.whatwg.org/#interface-textencoder
 const TextEncoder = @This();
@@ -31,7 +31,7 @@ pub fn get_encoding(_: *const TextEncoder) []const u8 {
     return "utf-8";
 }
 
-pub fn _encode(_: *const TextEncoder, v: []const u8) !Env.TypedArray(u8) {
+pub fn _encode(_: *const TextEncoder, v: []const u8) !js.TypedArray(u8) {
     // Ensure the input is a valid utf-8
     // It seems chrome accepts invalid utf-8 sequence.
     //

src/browser/env.zig

@@ -1,51 +0,0 @@
-const std = @import("std");
-
-const Page = @import("page.zig").Page;
-const js = @import("../runtime/js.zig");
-const generate = @import("../runtime/generate.zig");
-
-const WebApis = struct {
-    // Wrapped like this for debug ergonomics.
-    // When we create our Env, a few lines down, we define it as:
-    //   pub const Env = js.Env(*Page, WebApis);
-    //
-    // If there's a compile time error witht he Env, it's type will be readable,
-    // i.e.: runtime.js.Env(*browser.env.Page, browser.env.WebApis)
-    //
-    // But if we didn't wrap it in the struct, like we once didn't, and defined
-    // env as:
-    //   pub const Env = js.Env(*Page, Interfaces);
-    //
-    // Because Interfaces is an anynoumous type, it doesn't have a friendly name
-    // and errors would be something like:
-    //   runtime.js.Env(*browser.Page, .{...A HUNDRED TYPES...})
-    pub const Interfaces = generate.Tuple(.{
-        @import("crypto/crypto.zig").Crypto,
-        @import("console/console.zig").Console,
-        @import("css/css.zig").Interfaces,
-        @import("cssom/cssom.zig").Interfaces,
-        @import("dom/dom.zig").Interfaces,
-        @import("dom/shadow_root.zig").ShadowRoot,
-        @import("encoding/encoding.zig").Interfaces,
-        @import("events/event.zig").Interfaces,
-        @import("html/html.zig").Interfaces,
-        @import("iterator/iterator.zig").Interfaces,
-        @import("storage/storage.zig").Interfaces,
-        @import("url/url.zig").Interfaces,
-        @import("xhr/xhr.zig").Interfaces,
-        @import("xhr/form_data.zig").Interfaces,
-        @import("xhr/File.zig"),
-        @import("xmlserializer/xmlserializer.zig").Interfaces,
-        @import("fetch/fetch.zig").Interfaces,
-        @import("streams/streams.zig").Interfaces,
-    });
-};
-
-pub const JsThis = Env.JsThis;
-pub const JsObject = Env.JsObject;
-pub const Function = Env.Function;
-pub const Promise = Env.Promise;
-pub const PromiseResolver = Env.PromiseResolver;
-
-pub const Env = js.Env(*Page, WebApis);
-pub const Global = @import("html/window.zig").Window;

src/browser/events/PageTransitionEvent.zig

@@ -0,0 +1,84 @@
+// Copyright (C) 2023-2024  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const log = @import("../../log.zig");
+const Window = @import("../html/window.zig").Window;
+
+const parser = @import("../netsurf.zig");
+const Event = @import("../events/event.zig").Event;
+
+// https://developer.mozilla.org/en-US/docs/Web/API/PageTransitionEvent
+const PageTransitionEvent = @This();
+
+pub const prototype = *Event;
+pub const union_make_copy = true;
+
+pub const EventInit = struct {
+    persisted: ?bool,
+};
+
+proto: parser.Event,
+persisted: bool,
+
+pub fn constructor(event_type: []const u8, opts: EventInit) !PageTransitionEvent {
+    const event = try parser.eventCreate();
+    defer parser.eventDestroy(event);
+
+    try parser.eventInit(event, event_type, .{});
+    parser.eventSetInternalType(event, .page_transition_event);
+
+    return .{
+        .proto = event.*,
+        .persisted = opts.persisted orelse false,
+    };
+}
+
+const PageTransitionKind = enum { show, hide };
+
+pub fn dispatch(window: *Window, kind: PageTransitionKind, persisted: bool) void {
+    const evt_type = switch (kind) {
+        .show => "pageshow",
+        .hide => "pagehide",
+    };
+
+    log.debug(.script_event, "dispatch event", .{
+        .type = evt_type,
+        .source = "navigation",
+    });
+
+    var evt = PageTransitionEvent.constructor(evt_type, .{ .persisted = persisted }) catch |err| {
+        log.err(.app, "event constructor error", .{
+            .err = err,
+            .type = evt_type,
+            .source = "navigation",
+        });
+
+        return;
+    };
+
+    _ = parser.eventTargetDispatchEvent(
+        @as(*parser.EventTarget, @ptrCast(window)),
+        &evt.proto,
+    ) catch |err| {
+        log.err(.app, "dispatch event error", .{
+            .err = err,
+            .type = evt_type,
+            .source = "navigation",
+        });
+    };
+}

src/browser/events/composition_event.zig

@@ -0,0 +1,57 @@
+// Copyright (C) 2023-2025  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+
+const parser = @import("../netsurf.zig");
+
+// https://developer.mozilla.org/en-US/docs/Web/API/CompositionEvent
+pub const CompositionEvent = struct {
+    data: []const u8,
+    proto: parser.Event,
+
+    pub const union_make_copy = true;
+    pub const prototype = *parser.Event;
+
+    pub const ConstructorOptions = struct {
+        data: []const u8 = "",
+    };
+
+    pub fn constructor(event_type: []const u8, options_: ?ConstructorOptions) !CompositionEvent {
+        const options: ConstructorOptions = options_ orelse .{};
+
+        const event = try parser.eventCreate();
+        defer parser.eventDestroy(event);
+        try parser.eventInit(event, event_type, .{});
+        parser.eventSetInternalType(event, .composition_event);
+
+        return .{
+            .proto = event.*,
+            .data = options.data,
+        };
+    }
+
+    pub fn get_data(self: *const CompositionEvent) []const u8 {
+        return self.data;
+    }
+};
+
+const testing = @import("../../testing.zig");
+test "Browser: Events.Composition" {
+    try testing.htmlRunner("events/composition.html");
+}

src/browser/events/custom_event.zig

@@ -16,9 +16,10 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+const js = @import("../js/js.zig");
 const parser = @import("../netsurf.zig");
 const Event = @import("event.zig").Event;
-const JsObject = @import("../env.zig").JsObject;
+
 const netsurf = @import("../netsurf.zig");
 
 // https://dom.spec.whatwg.org/#interface-customevent
@@ -27,13 +28,13 @@ pub const CustomEvent = struct {
     pub const union_make_copy = true;
 
     proto: parser.Event,
-    detail: ?JsObject,
+    detail: ?js.Object,
 
     const CustomEventInit = struct {
         bubbles: bool = false,
         cancelable: bool = false,
         composed: bool = false,
-        detail: ?JsObject = null,
+        detail: ?js.Object = null,
     };
 
     pub fn constructor(event_type: []const u8, opts_: ?CustomEventInit) !CustomEvent {
@@ -53,7 +54,7 @@ pub const CustomEvent = struct {
         };
     }
 
-    pub fn get_detail(self: *CustomEvent) ?JsObject {
+    pub fn get_detail(self: *CustomEvent) ?js.Object {
         return self.detail;
     }
 
@@ -64,7 +65,7 @@ pub const CustomEvent = struct {
         event_type: []const u8,
         can_bubble: bool,
         cancelable: bool,
-        maybe_detail: ?JsObject,
+        maybe_detail: ?js.Object,
     ) !void {
         // This function can only be called after the constructor has called.
         // So we assume proto is initialized already by constructor.

src/browser/events/event.zig

@@ -17,11 +17,12 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
+const js = @import("../js/js.zig");
 const Allocator = std.mem.Allocator;
 
 const log = @import("../../log.zig");
 const parser = @import("../netsurf.zig");
-const generate = @import("../../runtime/generate.zig");
+const generate = @import("../js/generate.zig");
 
 const Page = @import("../page.zig").Page;
 const Node = @import("../dom/node.zig").Node;
@@ -36,6 +37,10 @@ const MouseEvent = @import("mouse_event.zig").MouseEvent;
 const KeyboardEvent = @import("keyboard_event.zig").KeyboardEvent;
 const ErrorEvent = @import("../html/error_event.zig").ErrorEvent;
 const MessageEvent = @import("../dom/MessageChannel.zig").MessageEvent;
+const PopStateEvent = @import("../html/History.zig").PopStateEvent;
+const CompositionEvent = @import("composition_event.zig").CompositionEvent;
+const NavigationCurrentEntryChangeEvent = @import("../navigation/root.zig").NavigationCurrentEntryChangeEvent;
+const PageTransitionEvent = @import("../events/PageTransitionEvent.zig");
 
 // Event interfaces
 pub const Interfaces = .{
@@ -46,6 +51,10 @@ pub const Interfaces = .{
     KeyboardEvent,
     ErrorEvent,
     MessageEvent,
+    PopStateEvent,
+    CompositionEvent,
+    NavigationCurrentEntryChangeEvent,
+    PageTransitionEvent,
 };
 
 pub const Union = generate.Union(Interfaces);
@@ -70,9 +79,15 @@ pub const Event = struct {
             .custom_event => .{ .CustomEvent = @as(*CustomEvent, @ptrCast(evt)).* },
             .progress_event => .{ .ProgressEvent = @as(*ProgressEvent, @ptrCast(evt)).* },
             .mouse_event => .{ .MouseEvent = @as(*parser.MouseEvent, @ptrCast(evt)) },
-            .error_event => .{ .ErrorEvent = @as(*ErrorEvent, @ptrCast(evt)).* },
+            .error_event => .{ .ErrorEvent = (@as(*ErrorEvent, @fieldParentPtr("proto", evt))).* },
             .message_event => .{ .MessageEvent = @as(*MessageEvent, @ptrCast(evt)).* },
             .keyboard_event => .{ .KeyboardEvent = @as(*parser.KeyboardEvent, @ptrCast(evt)) },
+            .pop_state => .{ .PopStateEvent = @as(*PopStateEvent, @ptrCast(evt)).* },
+            .composition_event => .{ .CompositionEvent = (@as(*CompositionEvent, @fieldParentPtr("proto", evt))).* },
+            .navigation_current_entry_change_event => .{
+                .NavigationCurrentEntryChangeEvent = @as(*NavigationCurrentEntryChangeEvent, @ptrCast(evt)).*,
+            },
+            .page_transition_event => .{ .PageTransitionEvent = @as(*PageTransitionEvent, @ptrCast(evt)).* },
         };
     }
 
@@ -84,8 +99,8 @@ pub const Event = struct {
 
     // Getters
 
-    pub fn get_type(self: *parser.Event) ![]const u8 {
-        return try parser.eventType(self);
+    pub fn get_type(self: *parser.Event) []const u8 {
+        return parser.eventType(self);
     }
 
     pub fn get_target(self: *parser.Event, page: *Page) !?EventTargetUnion {
@@ -158,7 +173,7 @@ pub const Event = struct {
         const et_ = parser.eventTarget(self);
         const et = et_ orelse return &.{};
 
-        var node: ?*parser.Node = switch (try parser.eventTargetInternalType(et)) {
+        var node: ?*parser.Node = switch (parser.eventTargetInternalType(et)) {
             .libdom_node => @as(*parser.Node, @ptrCast(et)),
             .plain => parser.eventTargetToNode(et),
             else => {
@@ -174,8 +189,8 @@ pub const Event = struct {
                 .node = try Node.toInterface(n),
             });
 
-            node = try parser.nodeParentNode(n);
-            if (node == null and try parser.nodeType(n) == .document_fragment) {
+            node = parser.nodeParentNode(n);
+            if (node == null and parser.nodeType(n) == .document_fragment) {
                 // we have a non-continuous hook from a shadowroot to its host (
                 // it's parent element). libdom doesn't really support ShdowRoots
                 // and, for the most part, that works out well since it naturally
@@ -216,18 +231,15 @@ pub const Event = struct {
 pub const EventHandler = struct {
     once: bool,
     capture: bool,
-    callback: Function,
+    callback: js.Function,
     node: parser.EventNode,
     listener: *parser.EventListener,
 
-    const Env = @import("../env.zig").Env;
-    const Function = Env.Function;
-
     pub const Listener = union(enum) {
-        function: Function,
-        object: Env.JsObject,
+        function: js.Function,
+        object: js.Object,
 
-        pub fn callback(self: Listener, target: *parser.EventTarget) !?Function {
+        pub fn callback(self: Listener, target: *parser.EventTarget) !?js.Function {
             return switch (self) {
                 .function => |func| try func.withThis(target),
                 .object => |obj| blk: {
@@ -328,7 +340,7 @@ pub const EventHandler = struct {
     fn handle(node: *parser.EventNode, event: *parser.Event) void {
         const ievent = Event.toInterface(event);
         const self: *EventHandler = @fieldParentPtr("node", node);
-        var result: Function.Result = undefined;
+        var result: js.Function.Result = undefined;
         self.callback.tryCall(void, .{ievent}, &result) catch {
             log.debug(.user_script, "callback error", .{
                 .err = result.exception,
@@ -339,7 +351,7 @@ pub const EventHandler = struct {
 
         if (self.once) {
             const target = parser.eventTarget(event).?;
-            const typ = parser.eventType(event) catch return;
+            const typ = parser.eventType(event);
             parser.eventTargetRemoveEventListener(
                 target,
                 typ,
@@ -394,6 +406,40 @@ const SignalCallback = struct {
     }
 };
 
+pub fn DirectEventHandler(
+    comptime TargetT: type,
+    target: *TargetT,
+    event_type: []const u8,
+    maybe_listener: ?EventHandler.Listener,
+    cb: *?js.Function,
+    page_arena: std.mem.Allocator,
+) !void {
+    const event_target = parser.toEventTarget(TargetT, target);
+
+    // Check if we have a listener set.
+    if (cb.*) |callback| {
+        const listener = try parser.eventTargetHasListener(event_target, event_type, false, callback.id);
+        std.debug.assert(listener != null);
+        try parser.eventTargetRemoveEventListener(event_target, event_type, listener.?, false);
+    }
+
+    if (maybe_listener) |listener| {
+        switch (listener) {
+            // If an object is given as listener, do nothing.
+            .object => {},
+            .function => |callback| {
+                _ = try EventHandler.register(page_arena, event_target, event_type, listener, null) orelse unreachable;
+                cb.* = callback;
+
+                return;
+            },
+        }
+    }
+
+    // Just unset the listener.
+    cb.* = null;
+}
+
 const testing = @import("../../testing.zig");
 test "Browser: Event" {
     try testing.htmlRunner("events/event.html");

src/browser/events/keyboard_event.zig

@@ -22,7 +22,6 @@ const builtin = @import("builtin");
 
 const parser = @import("../netsurf.zig");
 const Event = @import("event.zig").Event;
-const JsObject = @import("../env.zig").JsObject;
 
 // TODO: We currently don't have a UIEvent interface so we skip it in the prototype chain.
 // https://developer.mozilla.org/en-US/docs/Web/API/UIEvent
@@ -54,8 +53,8 @@ pub const KeyboardEvent = struct {
     pub fn constructor(event_type: []const u8, maybe_options: ?ConstructorOptions) !*parser.KeyboardEvent {
         const options: ConstructorOptions = maybe_options orelse .{};
 
-        var event = try parser.keyboardEventCreate();
-        parser.eventSetInternalType(@ptrCast(&event), .keyboard_event);
+        const event = try parser.keyboardEventCreate();
+        parser.eventSetInternalType(@ptrCast(event), .keyboard_event);
 
         try parser.keyboardEventInit(
             event,

src/browser/events/mouse_event.zig

@@ -21,7 +21,6 @@ const log = @import("../../log.zig");
 
 const parser = @import("../netsurf.zig");
 const Event = @import("event.zig").Event;
-const JsObject = @import("../env.zig").JsObject;
 
 // TODO: We currently don't have a UIEvent interface so we skip it in the prototype chain.
 // https://developer.mozilla.org/en-US/docs/Web/API/UIEvent
@@ -55,8 +54,8 @@ pub const MouseEvent = struct {
     pub fn constructor(event_type: []const u8, opts_: ?MouseEventInit) !*parser.MouseEvent {
         const opts = opts_ orelse MouseEventInit{};
 
-        var mouse_event = try parser.mouseEventCreate();
-        parser.eventSetInternalType(@ptrCast(&mouse_event), .mouse_event);
+        const mouse_event = try parser.mouseEventCreate();
+        parser.eventSetInternalType(@ptrCast(mouse_event), .mouse_event);
 
         try parser.mouseEventInit(mouse_event, event_type, .{
             .x = opts.clientX,
@@ -69,7 +68,7 @@ pub const MouseEvent = struct {
         });
 
         if (!std.mem.eql(u8, event_type, "click")) {
-            log.warn(.mouse_event, "unsupported mouse event", .{ .event = event_type });
+            log.warn(.browser, "unsupported mouse event", .{ .event = event_type });
         }
 
         return mouse_event;

src/browser/fetch/Headers.zig

@@ -17,15 +17,13 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
+const js = @import("../js/js.zig");
 const log = @import("../../log.zig");
 const URL = @import("../../url.zig").URL;
 const Page = @import("../page.zig").Page;
 
 const iterator = @import("../iterator/iterator.zig");
 
-const v8 = @import("v8");
-const Env = @import("../env.zig").Env;
-
 // https://developer.mozilla.org/en-US/docs/Web/API/Headers
 const Headers = @This();
 
@@ -69,7 +67,7 @@ pub const HeadersInit = union(enum) {
     // Headers
     headers: *Headers,
     // Mappings
-    object: Env.JsObject,
+    object: js.Object,
 };
 
 pub fn constructor(_init: ?HeadersInit, page: *Page) !Headers {
@@ -159,7 +157,7 @@ pub fn _entries(self: *const Headers) HeadersEntryIterable {
     };
 }
 
-pub fn _forEach(self: *Headers, callback_fn: Env.Function, this_arg: ?Env.JsObject) !void {
+pub fn _forEach(self: *Headers, callback_fn: js.Function, this_arg: ?js.Object) !void {
     var iter = self.headers.iterator();
 
     const cb = if (this_arg) |this| try callback_fn.withThis(this) else callback_fn;

src/browser/fetch/Request.zig

@@ -17,6 +17,7 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
+const js = @import("../js/js.zig");
 const log = @import("../../log.zig");
 
 const URL = @import("../../url.zig").URL;
@@ -26,9 +27,6 @@ const Response = @import("./Response.zig");
 const Http = @import("../../http/Http.zig");
 const ReadableStream = @import("../streams/ReadableStream.zig");
 
-const v8 = @import("v8");
-const Env = @import("../env.zig").Env;
-
 const Headers = @import("Headers.zig");
 const HeadersInit = @import("Headers.zig").HeadersInit;
 
@@ -80,6 +78,27 @@ pub const RequestCredentials = enum {
     }
 };
 
+pub const RequestMode = enum {
+    cors,
+    @"no-cors",
+    @"same-origin",
+    navigate,
+
+    pub fn fromString(str: []const u8) ?RequestMode {
+        for (std.enums.values(RequestMode)) |cache| {
+            if (std.ascii.eqlIgnoreCase(str, @tagName(cache))) {
+                return cache;
+            }
+        } else {
+            return null;
+        }
+    }
+
+    pub fn toString(self: RequestMode) []const u8 {
+        return @tagName(self);
+    }
+};
+
 // https://developer.mozilla.org/en-US/docs/Web/API/RequestInit
 pub const RequestInit = struct {
     body: ?[]const u8 = null,
@@ -88,6 +107,7 @@ pub const RequestInit = struct {
     headers: ?HeadersInit = null,
     integrity: ?[]const u8 = null,
     method: ?[]const u8 = null,
+    mode: ?[]const u8 = null,
 };
 
 // https://developer.mozilla.org/en-US/docs/Web/API/Request/Request
@@ -97,6 +117,8 @@ method: Http.Method,
 url: [:0]const u8,
 cache: RequestCache,
 credentials: RequestCredentials,
+// no-cors is default is not built with constructor.
+mode: RequestMode = .@"no-cors",
 headers: Headers,
 body: ?[]const u8,
 body_used: bool = false,
@@ -115,11 +137,11 @@ pub fn constructor(input: RequestInput, _options: ?RequestInit, page: *Page) !Re
         },
     };
 
-    const body = if (options.body) |body| try arena.dupe(u8, body) else null;
     const cache = (if (options.cache) |cache| RequestCache.fromString(cache) else null) orelse RequestCache.default;
     const credentials = (if (options.credentials) |creds| RequestCredentials.fromString(creds) else null) orelse RequestCredentials.@"same-origin";
     const integrity = if (options.integrity) |integ| try arena.dupe(u8, integ) else "";
     const headers: Headers = if (options.headers) |hdrs| try Headers.constructor(hdrs, page) else .{};
+    const mode = (if (options.mode) |mode| RequestMode.fromString(mode) else null) orelse RequestMode.cors;
 
     const method: Http.Method = blk: {
         if (options.method) |given_method| {
@@ -135,11 +157,19 @@ pub fn constructor(input: RequestInput, _options: ?RequestInit, page: *Page) !Re
         }
     };
 
+    // Can't have a body on .GET or .HEAD.
+    const body: ?[]const u8 = blk: {
+        if (method == .GET or method == .HEAD) {
+            break :blk null;
+        } else break :blk if (options.body) |body| try arena.dupe(u8, body) else null;
+    };
+
     return .{
         .method = method,
         .url = url,
         .cache = cache,
         .credentials = credentials,
+        .mode = mode,
         .headers = headers,
         .body = body,
         .integrity = integrity,
@@ -149,7 +179,7 @@ pub fn constructor(input: RequestInput, _options: ?RequestInit, page: *Page) !Re
 pub fn get_body(self: *const Request, page: *Page) !?*ReadableStream {
     if (self.body) |body| {
         const stream = try ReadableStream.constructor(null, null, page);
-        try stream.queue.append(page.arena, body);
+        try stream.queue.append(page.arena, .{ .string = body });
         return stream;
     } else return null;
 }
@@ -181,6 +211,10 @@ pub fn get_method(self: *const Request) []const u8 {
     return @tagName(self.method);
 }
 
+pub fn get_mode(self: *const Request) RequestMode {
+    return self.mode;
+}
+
 pub fn get_url(self: *const Request) []const u8 {
     return self.url;
 }
@@ -205,59 +239,38 @@ pub fn _clone(self: *Request) !Request {
     };
 }
 
-pub fn _bytes(self: *Response, page: *Page) !Env.Promise {
+pub fn _bytes(self: *Response, page: *Page) !js.Promise {
     if (self.body_used) {
         return error.TypeError;
     }
-
-    const resolver = Env.PromiseResolver{
-        .js_context = page.main_context,
-        .resolver = v8.PromiseResolver.init(page.main_context.v8_context),
-    };
-
-    try resolver.resolve(self.body);
     self.body_used = true;
-    return resolver.promise();
+    return page.js.resolvePromise(self.body);
 }
 
-pub fn _json(self: *Response, page: *Page) !Env.Promise {
+pub fn _json(self: *Response, page: *Page) !js.Promise {
     if (self.body_used) {
         return error.TypeError;
     }
-
-    const resolver = Env.PromiseResolver{
-        .js_context = page.main_context,
-        .resolver = v8.PromiseResolver.init(page.main_context.v8_context),
-    };
-
-    const p = std.json.parseFromSliceLeaky(
-        std.json.Value,
-        page.call_arena,
-        self.body,
-        .{},
-    ) catch |e| {
-        log.info(.browser, "invalid json", .{ .err = e, .source = "Request" });
-        return error.SyntaxError;
-    };
-
-    try resolver.resolve(p);
     self.body_used = true;
-    return resolver.promise();
+
+    if (self.body) |body| {
+        const value = js.Value.fromJson(page.js, body) catch |e| {
+            log.info(.browser, "invalid json", .{ .err = e, .source = "Request" });
+            return error.SyntaxError;
+        };
+        const pvalue = try value.persist(page.js);
+
+        return page.js.resolvePromise(pvalue);
+    }
+    return page.js.resolvePromise(null);
 }
 
-pub fn _text(self: *Response, page: *Page) !Env.Promise {
+pub fn _text(self: *Response, page: *Page) !js.Promise {
     if (self.body_used) {
         return error.TypeError;
     }
-
-    const resolver = Env.PromiseResolver{
-        .js_context = page.main_context,
-        .resolver = v8.PromiseResolver.init(page.main_context.v8_context),
-    };
-
-    try resolver.resolve(self.body);
     self.body_used = true;
-    return resolver.promise();
+    return page.js.resolvePromise(self.body);
 }
 
 const testing = @import("../../testing.zig");

src/browser/fetch/Response.zig

@@ -17,10 +17,9 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
+const js = @import("../js/js.zig");
 const log = @import("../../log.zig");
 
-const v8 = @import("v8");
-
 const HttpClient = @import("../../http/Client.zig");
 const Http = @import("../../http/Http.zig");
 const URL = @import("../../url.zig").URL;
@@ -29,7 +28,6 @@ const ReadableStream = @import("../streams/ReadableStream.zig");
 const Headers = @import("Headers.zig");
 const HeadersInit = @import("Headers.zig").HeadersInit;
 
-const Env = @import("../env.zig").Env;
 const Mime = @import("../mime.zig").Mime;
 const Page = @import("../page.zig").Page;
 
@@ -41,9 +39,10 @@ status_text: []const u8 = "",
 headers: Headers,
 mime: ?Mime = null,
 url: []const u8 = "",
-body: []const u8 = "",
+body: ?[]const u8 = null,
 body_used: bool = false,
 redirected: bool = false,
+type: ResponseType = .basic,
 
 const ResponseBody = union(enum) {
     string: []const u8,
@@ -55,6 +54,28 @@ const ResponseOptions = struct {
     headers: ?HeadersInit = null,
 };
 
+pub const ResponseType = enum {
+    basic,
+    cors,
+    @"error",
+    @"opaque",
+    opaqueredirect,
+
+    pub fn fromString(str: []const u8) ?ResponseType {
+        for (std.enums.values(ResponseType)) |cache| {
+            if (std.ascii.eqlIgnoreCase(str, @tagName(cache))) {
+                return cache;
+            }
+        } else {
+            return null;
+        }
+    }
+
+    pub fn toString(self: ResponseType) []const u8 {
+        return @tagName(self);
+    }
+};
+
 pub fn constructor(_input: ?ResponseBody, _options: ?ResponseOptions, page: *Page) !Response {
     const arena = page.arena;
 
@@ -68,7 +89,7 @@ pub fn constructor(_input: ?ResponseBody, _options: ?ResponseOptions, page: *Pag
                 },
             }
         } else {
-            break :blk "";
+            break :blk null;
         }
     };
 
@@ -85,7 +106,9 @@ pub fn constructor(_input: ?ResponseBody, _options: ?ResponseOptions, page: *Pag
 
 pub fn get_body(self: *const Response, page: *Page) !*ReadableStream {
     const stream = try ReadableStream.constructor(null, null, page);
-    try stream.queue.append(page.arena, self.body);
+    if (self.body) |body| {
+        try stream.queue.append(page.arena, .{ .string = body });
+    }
     return stream;
 }
 
@@ -113,6 +136,10 @@ pub fn get_statusText(self: *const Response) []const u8 {
     return self.status_text;
 }
 
+pub fn get_type(self: *const Response) ResponseType {
+    return self.type;
+}
+
 pub fn get_url(self: *const Response) []const u8 {
     return self.url;
 }
@@ -132,62 +159,44 @@ pub fn _clone(self: *const Response) !Response {
         .redirected = self.redirected,
         .status = self.status,
         .url = self.url,
+        .type = self.type,
     };
 }
 
-pub fn _bytes(self: *Response, page: *Page) !Env.Promise {
+pub fn _bytes(self: *Response, page: *Page) !js.Promise {
     if (self.body_used) {
         return error.TypeError;
     }
 
-    const resolver = Env.PromiseResolver{
-        .js_context = page.main_context,
-        .resolver = v8.PromiseResolver.init(page.main_context.v8_context),
-    };
-
-    try resolver.resolve(self.body);
     self.body_used = true;
-    return resolver.promise();
+    return page.js.resolvePromise(self.body);
 }
 
-pub fn _json(self: *Response, page: *Page) !Env.Promise {
+pub fn _json(self: *Response, page: *Page) !js.Promise {
     if (self.body_used) {
         return error.TypeError;
     }
 
-    const resolver = Env.PromiseResolver{
-        .js_context = page.main_context,
-        .resolver = v8.PromiseResolver.init(page.main_context.v8_context),
-    };
+    if (self.body) |body| {
+        self.body_used = true;
+        const value = js.Value.fromJson(page.js, body) catch |e| {
+            log.info(.browser, "invalid json", .{ .err = e, .source = "Response" });
+            return error.SyntaxError;
+        };
+        const pvalue = try value.persist(page.js);
 
-    const p = std.json.parseFromSliceLeaky(
-        std.json.Value,
-        page.call_arena,
-        self.body,
-        .{},
-    ) catch |e| {
-        log.info(.browser, "invalid json", .{ .err = e, .source = "Response" });
-        return error.SyntaxError;
-    };
-
-    try resolver.resolve(p);
-    self.body_used = true;
-    return resolver.promise();
+        return page.js.resolvePromise(pvalue);
+    }
+    return page.js.resolvePromise(null);
 }
 
-pub fn _text(self: *Response, page: *Page) !Env.Promise {
+pub fn _text(self: *Response, page: *Page) !js.Promise {
     if (self.body_used) {
         return error.TypeError;
     }
-
-    const resolver = Env.PromiseResolver{
-        .js_context = page.main_context,
-        .resolver = v8.PromiseResolver.init(page.main_context.v8_context),
-    };
-
-    try resolver.resolve(self.body);
     self.body_used = true;
-    return resolver.promise();
+
+    return page.js.resolvePromise(self.body);
 }
 
 const testing = @import("../../testing.zig");

src/browser/fetch/fetch.zig

@@ -19,7 +19,7 @@
 const std = @import("std");
 const log = @import("../../log.zig");
 
-const Env = @import("../env.zig").Env;
+const js = @import("../js/js.zig");
 const Page = @import("../page.zig").Page;
 
 const Http = @import("../../http/Http.zig");
@@ -43,9 +43,9 @@ pub const Interfaces = .{
 };
 
 pub const FetchContext = struct {
+    page: *Page,
     arena: std.mem.Allocator,
-    js_ctx: *Env.JsContext,
-    promise_resolver: Env.PersistentPromiseResolver,
+    promise_resolver: js.PersistentPromiseResolver,
 
     method: Http.Method,
     url: []const u8,
@@ -53,6 +53,7 @@ pub const FetchContext = struct {
     headers: std.ArrayListUnmanaged([]const u8) = .empty,
     status: u16 = 0,
     mime: ?Mime = null,
+    mode: Request.RequestMode,
     transfer: ?*HttpClient.Transfer = null,
 
     /// This effectively takes ownership of the FetchContext.
@@ -62,6 +63,22 @@ pub const FetchContext = struct {
     pub fn toResponse(self: *const FetchContext) !Response {
         var headers: Headers = .{};
 
+        // seems to be the highest priority
+        const same_origin = try self.page.isSameOrigin(self.url);
+
+        // If the mode is "no-cors", we need to return this opaque/stripped Response.
+        // https://developer.mozilla.org/en-US/docs/Web/API/Response/type
+        if (!same_origin and self.mode == .@"no-cors") {
+            return Response{
+                .status = 0,
+                .headers = headers,
+                .mime = self.mime,
+                .body = null,
+                .url = self.url,
+                .type = .@"opaque",
+            };
+        }
+
         // convert into Headers
         for (self.headers.items) |hdr| {
             var iter = std.mem.splitScalar(u8, hdr, ':');
@@ -70,22 +87,35 @@ pub const FetchContext = struct {
             try headers.append(name, value, self.arena);
         }
 
+        const resp_type: Response.ResponseType = blk: {
+            if (same_origin or std.mem.startsWith(u8, self.url, "data:")) {
+                break :blk .basic;
+            }
+
+            break :blk switch (self.mode) {
+                .cors => .cors,
+                .@"same-origin", .navigate => .basic,
+                .@"no-cors" => unreachable,
+            };
+        };
+
         return Response{
             .status = self.status,
             .headers = headers,
             .mime = self.mime,
             .body = self.body.items,
             .url = self.url,
+            .type = resp_type,
         };
     }
 };
 
 // https://developer.mozilla.org/en-US/docs/Web/API/Window/fetch
-pub fn fetch(input: RequestInput, options: ?RequestInit, page: *Page) !Env.Promise {
+pub fn fetch(input: RequestInput, options: ?RequestInit, page: *Page) !js.Promise {
     const arena = page.arena;
 
     const req = try Request.constructor(input, options, page);
-    var headers = try Http.Headers.init();
+    var headers = try page.http_client.newHeaders();
 
     // Copy our headers into the HTTP headers.
     var header_iter = req.headers.headers.iterator();
@@ -101,15 +131,16 @@ pub fn fetch(input: RequestInput, options: ?RequestInit, page: *Page) !Env.Promi
 
     try page.requestCookie(.{}).headersForRequest(arena, req.url, &headers);
 
-    const resolver = try page.main_context.createPersistentPromiseResolver();
+    const resolver = try page.js.createPromiseResolver(.page);
 
     const fetch_ctx = try arena.create(FetchContext);
     fetch_ctx.* = .{
+        .page = page,
         .arena = arena,
-        .js_ctx = page.main_context,
         .promise_resolver = resolver,
         .method = req.method,
         .url = req.url,
+        .mode = req.mode,
     };
 
     try page.http_client.request(.{

src/browser/file/Blob.zig

@@ -0,0 +1,284 @@
+// Copyright (C) 2023-2025  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+const Writer = std.Io.Writer;
+
+const Page = @import("../page.zig").Page;
+const js = @import("../js/js.zig");
+
+const ReadableStream = @import("../streams/ReadableStream.zig");
+
+/// https://w3c.github.io/FileAPI/#blob-section
+/// https://developer.mozilla.org/en-US/docs/Web/API/Blob
+const Blob = @This();
+
+/// Immutable slice of blob.
+/// Note that another blob may hold a pointer/slice to this,
+/// so its better to leave the deallocation of it to arena allocator.
+slice: []const u8,
+/// MIME attached to blob. Can be an empty string.
+mime: []const u8,
+
+const ConstructorOptions = struct {
+    /// MIME type.
+    type: []const u8 = "",
+    /// How to handle line endings (CR and LF).
+    /// `transparent` means do nothing, `native` expects CRLF (\r\n) on Windows.
+    endings: []const u8 = "transparent",
+};
+
+/// Creates a new Blob.
+pub fn constructor(
+    maybe_blob_parts: ?[]const []const u8,
+    maybe_options: ?ConstructorOptions,
+    page: *Page,
+) !Blob {
+    const options: ConstructorOptions = maybe_options orelse .{};
+    // Setup MIME; This can be any string according to my observations.
+    const mime: []const u8 = blk: {
+        const t = options.type;
+        if (t.len == 0) {
+            break :blk "";
+        }
+
+        break :blk try page.arena.dupe(u8, t);
+    };
+
+    if (maybe_blob_parts) |blob_parts| {
+        var w: Writer.Allocating = .init(page.arena);
+        const use_native_endings = std.mem.eql(u8, options.endings, "native");
+        try writeBlobParts(&w.writer, blob_parts, use_native_endings);
+
+        return .{ .slice = w.written(), .mime = mime };
+    }
+
+    // We don't have `blob_parts`, why would you want a Blob anyway then?
+    return .{ .slice = "", .mime = mime };
+}
+
+const largest_vector = @max(std.simd.suggestVectorLength(u8) orelse 1, 8);
+/// Array of possible vector sizes for the current arch in decrementing order.
+/// We may move this to some file for SIMD helpers in the future.
+const vector_sizes = blk: {
+    // Required for length calculation.
+    var n: usize = largest_vector;
+    var total: usize = 0;
+    while (n != 2) : (n /= 2) total += 1;
+    // Populate an array with vector sizes.
+    n = largest_vector;
+    var i: usize = 0;
+    var items: [total]usize = undefined;
+    while (n != 2) : (n /= 2) {
+        defer i += 1;
+        items[i] = n;
+    }
+
+    break :blk items;
+};
+
+/// Writes blob parts to given `Writer` with desired endings.
+fn writeBlobParts(
+    writer: *Writer,
+    blob_parts: []const []const u8,
+    use_native_endings: bool,
+) !void {
+    // Transparent.
+    if (!use_native_endings) {
+        for (blob_parts) |part| {
+            try writer.writeAll(part);
+        }
+
+        return;
+    }
+
+    // TODO: Windows support.
+
+    // Linux & Unix.
+    // Both Firefox and Chrome implement it as such:
+    // CRLF => LF
+    // CR   => LF
+    // So even though CR is not followed by LF, it gets replaced.
+    //
+    // I believe this is because such scenario is possible:
+    // ```
+    // let parts = [ "the quick\r", "\nbrown fox" ];
+    // ```
+    // In the example, one should have to check the part before in order to
+    // understand that CRLF is being presented in the final buffer.
+    // So they took a simpler approach, here's what given blob parts produce:
+    // ```
+    // "the quick\n\nbrown fox"
+    // ```
+    scan_parts: for (blob_parts) |part| {
+        var end: usize = 0;
+
+        inline for (vector_sizes) |vector_len| {
+            const Vec = @Vector(vector_len, u8);
+
+            while (end + vector_len <= part.len) : (end += vector_len) {
+                const cr: Vec = @splat('\r');
+                // Load chunk as vectors.
+                const slice = part[end..][0..vector_len];
+                const chunk: Vec = slice.*;
+                // Look for CR.
+                const match = chunk == cr;
+
+                // Create a bitset out of match vector.
+                const bitset = std.bit_set.IntegerBitSet(vector_len){
+                    .mask = @bitCast(@intFromBool(match)),
+                };
+
+                var iter = bitset.iterator(.{});
+                var relative_start: usize = 0;
+                while (iter.next()) |index| {
+                    _ = try writer.writeVec(&.{ slice[relative_start..index], "\n" });
+
+                    if (index + 1 != slice.len and slice[index + 1] == '\n') {
+                        relative_start = index + 2;
+                    } else {
+                        relative_start = index + 1;
+                    }
+                }
+
+                _ = try writer.writeVec(&.{slice[relative_start..]});
+            }
+        }
+
+        // Scalar scan fallback.
+        var relative_start: usize = end;
+        while (end < part.len) {
+            if (part[end] == '\r') {
+                _ = try writer.writeVec(&.{ part[relative_start..end], "\n" });
+
+                // Part ends with CR. We can continue to next part.
+                if (end + 1 == part.len) {
+                    continue :scan_parts;
+                }
+
+                // If next char is LF, skip it too.
+                if (part[end + 1] == '\n') {
+                    relative_start = end + 2;
+                } else {
+                    relative_start = end + 1;
+                }
+            }
+
+            end += 1;
+        }
+
+        // Write the remaining. We get this in such situations:
+        // `the quick brown\rfox`
+        // `the quick brown\r\nfox`
+        try writer.writeAll(part[relative_start..end]);
+    }
+}
+
+/// Returns a Promise that resolves with the contents of the blob
+/// as binary data contained in an ArrayBuffer.
+pub fn _arrayBuffer(self: *const Blob, page: *Page) !js.Promise {
+    return page.js.resolvePromise(js.ArrayBuffer{ .values = self.slice });
+}
+
+/// Returns a ReadableStream which upon reading returns the data
+/// contained within the Blob.
+pub fn _stream(self: *const Blob, page: *Page) !*ReadableStream {
+    const stream = try ReadableStream.constructor(null, null, page);
+    try stream.queue.append(page.arena, .{
+        .uint8array = .{ .values = self.slice },
+    });
+    return stream;
+}
+
+/// Returns a Promise that resolves with a string containing
+/// the contents of the blob, interpreted as UTF-8.
+pub fn _text(self: *const Blob, page: *Page) !js.Promise {
+    return page.js.resolvePromise(self.slice);
+}
+
+/// Extension to Blob; works on Firefox and Safari.
+/// https://developer.mozilla.org/en-US/docs/Web/API/Blob/bytes
+/// Returns a Promise that resolves with a Uint8Array containing
+/// the contents of the blob as an array of bytes.
+pub fn _bytes(self: *const Blob, page: *Page) !js.Promise {
+    return page.js.resolvePromise(js.TypedArray(u8){ .values = self.slice });
+}
+
+/// Returns a new Blob object which contains data
+/// from a subset of the blob on which it's called.
+pub fn _slice(
+    self: *const Blob,
+    maybe_start: ?i32,
+    maybe_end: ?i32,
+    maybe_content_type: ?[]const u8,
+    page: *Page,
+) !Blob {
+    const mime: []const u8 = blk: {
+        if (maybe_content_type) |content_type| {
+            if (content_type.len == 0) {
+                break :blk "";
+            }
+
+            break :blk try page.arena.dupe(u8, content_type);
+        }
+
+        break :blk "";
+    };
+
+    const slice = self.slice;
+    if (maybe_start) |_start| {
+        const start = blk: {
+            if (_start < 0) {
+                break :blk slice.len -| @abs(_start);
+            }
+
+            break :blk @min(slice.len, @as(u31, @intCast(_start)));
+        };
+
+        const end: usize = blk: {
+            if (maybe_end) |_end| {
+                if (_end < 0) {
+                    break :blk @max(start, slice.len -| @abs(_end));
+                }
+
+                break :blk @min(slice.len, @max(start, @as(u31, @intCast(_end))));
+            }
+
+            break :blk slice.len;
+        };
+
+        return .{ .slice = slice[start..end], .mime = mime };
+    }
+
+    return .{ .slice = slice, .mime = mime };
+}
+
+/// Returns the size of the Blob in bytes.
+pub fn get_size(self: *const Blob) usize {
+    return self.slice.len;
+}
+
+/// Returns the type of Blob; likely a MIME type, yet anything can be given.
+pub fn get_type(self: *const Blob) []const u8 {
+    return self.mime;
+}
+
+const testing = @import("../../testing.zig");
+test "Browser: File.Blob" {
+    try testing.htmlRunner("file/blob.html");
+}

src/browser/file/File.zig

@@ -21,14 +21,12 @@ const std = @import("std");
 // https://w3c.github.io/FileAPI/#file-section
 const File = @This();
 
-// Very incomplete. The prototype for this is Blob, which we don't have.
-// This minimum "implementation" is added because some JavaScript code just
-// checks: if (x instanceof File) throw Error(...)
+/// TODO: Implement File API.
 pub fn constructor() File {
     return .{};
 }
 
 const testing = @import("../../testing.zig");
-test "Browser: File" {
-    try testing.htmlRunner("xhr/file.html");
+test "Browser: File.File" {
+    try testing.htmlRunner("file/file.html");
 }

src/browser/file/root.zig

@@ -0,0 +1,7 @@
+//! File API.
+//! https://developer.mozilla.org/en-US/docs/Web/API/File_API
+
+pub const Interfaces = .{
+    @import("./Blob.zig"),
+    @import("./File.zig"),
+};

src/browser/html/AbortController.zig

@@ -17,9 +17,9 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
+const js = @import("../js/js.zig");
 const log = @import("../../log.zig");
 const parser = @import("../netsurf.zig");
-const Env = @import("../env.zig").Env;
 const Page = @import("../page.zig").Page;
 const EventTarget = @import("../dom/event_target.zig").EventTarget;
 
@@ -113,12 +113,12 @@ pub const AbortSignal = struct {
     }
 
     const ThrowIfAborted = union(enum) {
-        exception: Env.Exception,
+        exception: js.Exception,
         undefined: void,
     };
     pub fn _throwIfAborted(self: *const AbortSignal, page: *Page) ThrowIfAborted {
         if (self.aborted) {
-            const ex = page.main_context.throw(self.reason orelse DEFAULT_REASON);
+            const ex = page.js.throw(self.reason orelse DEFAULT_REASON);
             return .{ .exception = ex };
         }
         return .{ .undefined = {} };

src/browser/html/DataSet.zig

@@ -17,7 +17,8 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 const std = @import("std");
 const parser = @import("../netsurf.zig");
-const Env = @import("../env.zig").Env;
+const js = @import("../js/js.zig");
+
 const Page = @import("../page.zig").Page;
 
 const Allocator = std.mem.Allocator;
@@ -26,7 +27,7 @@ const DataSet = @This();
 
 element: *parser.Element,
 
-pub fn named_get(self: *const DataSet, name: []const u8, _: *bool, page: *Page) !Env.UndefinedOr([]const u8) {
+pub fn named_get(self: *const DataSet, name: []const u8, _: *bool, page: *Page) !js.UndefinedOr([]const u8) {
     const normalized_name = try normalize(page.call_arena, name);
     if (try parser.elementGetAttribute(self.element, normalized_name)) |value| {
         return .{ .value = value };

src/browser/html/History.zig

@@ -0,0 +1,180 @@
+// Copyright (C) 2023-2024  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+const log = @import("../../log.zig");
+
+const js = @import("../js/js.zig");
+const Page = @import("../page.zig").Page;
+const Window = @import("window.zig").Window;
+
+// https://html.spec.whatwg.org/multipage/nav-history-apis.html#the-history-interface
+const History = @This();
+
+const ScrollRestorationMode = enum {
+    pub const ENUM_JS_USE_TAG = true;
+
+    auto,
+    manual,
+};
+
+scroll_restoration: ScrollRestorationMode = .auto,
+
+pub fn get_length(_: *History, page: *Page) u32 {
+    return @intCast(page.session.navigation.entries.items.len);
+}
+
+pub fn get_scrollRestoration(self: *History) ScrollRestorationMode {
+    return self.scroll_restoration;
+}
+
+pub fn set_scrollRestoration(self: *History, mode: ScrollRestorationMode) void {
+    self.scroll_restoration = mode;
+}
+
+pub fn get_state(_: *History, page: *Page) !?js.Value {
+    if (page.session.navigation.currentEntry().state.value) |state| {
+        const value = try js.Value.fromJson(page.js, state);
+        return value;
+    } else {
+        return null;
+    }
+}
+
+pub fn _pushState(_: *const History, state: js.Object, _: ?[]const u8, _url: ?[]const u8, page: *Page) !void {
+    const arena = page.session.arena;
+    const url = if (_url) |u| try arena.dupe(u8, u) else try arena.dupe(u8, page.url.raw);
+
+    const json = state.toJson(arena) catch return error.DataClone;
+    _ = try page.session.navigation.pushEntry(url, .{ .source = .history, .value = json }, page, true);
+}
+
+pub fn _replaceState(_: *const History, state: js.Object, _: ?[]const u8, _url: ?[]const u8, page: *Page) !void {
+    const arena = page.session.arena;
+    const url = if (_url) |u| try arena.dupe(u8, u) else try arena.dupe(u8, page.url.raw);
+
+    const json = try state.toJson(arena);
+    _ = try page.session.navigation.replaceEntry(url, .{ .source = .history, .value = json }, page, true);
+}
+
+pub fn go(_: *const History, delta: i32, page: *Page) !void {
+    // 0 behaves the same as no argument, both reloading the page.
+
+    const current = page.session.navigation.index;
+    const index_s: i64 = @intCast(@as(i64, @intCast(current)) + @as(i64, @intCast(delta)));
+    if (index_s < 0 or index_s > page.session.navigation.entries.items.len - 1) {
+        return;
+    }
+
+    const index = @as(usize, @intCast(index_s));
+    const entry = page.session.navigation.entries.items[index];
+
+    if (entry.url) |url| {
+        if (try page.isSameOrigin(url)) {
+            PopStateEvent.dispatch(entry.state.value, page);
+        }
+    }
+
+    _ = try page.session.navigation.navigate(entry.url, .{ .traverse = index }, page);
+}
+
+pub fn _go(self: *History, _delta: ?i32, page: *Page) !void {
+    try self.go(_delta orelse 0, page);
+}
+
+pub fn _back(self: *History, page: *Page) !void {
+    try self.go(-1, page);
+}
+
+pub fn _forward(self: *History, page: *Page) !void {
+    try self.go(1, page);
+}
+
+const parser = @import("../netsurf.zig");
+const Event = @import("../events/event.zig").Event;
+
+pub const PopStateEvent = struct {
+    pub const prototype = *Event;
+    pub const union_make_copy = true;
+
+    pub const EventInit = struct {
+        state: ?[]const u8 = null,
+    };
+
+    proto: parser.Event,
+    state: ?[]const u8,
+
+    pub fn constructor(event_type: []const u8, opts: ?EventInit) !PopStateEvent {
+        const event = try parser.eventCreate();
+        defer parser.eventDestroy(event);
+        try parser.eventInit(event, event_type, .{});
+        parser.eventSetInternalType(event, .pop_state);
+
+        const o = opts orelse EventInit{};
+
+        return .{
+            .proto = event.*,
+            .state = o.state,
+        };
+    }
+
+    // `hasUAVisualTransition` is not implemented. It isn't baseline so this is okay.
+
+    pub fn get_state(self: *const PopStateEvent, page: *Page) !?js.Value {
+        if (self.state) |state| {
+            const value = try js.Value.fromJson(page.js, state);
+            return value;
+        } else {
+            return null;
+        }
+    }
+
+    pub fn dispatch(state: ?[]const u8, page: *Page) void {
+        log.debug(.script_event, "dispatch popstate event", .{
+            .type = "popstate",
+            .source = "history",
+        });
+
+        var evt = PopStateEvent.constructor("popstate", .{ .state = state }) catch |err| {
+            log.err(.app, "event constructor error", .{
+                .err = err,
+                .type = "popstate",
+                .source = "history",
+            });
+
+            return;
+        };
+
+        _ = parser.eventTargetDispatchEvent(
+            parser.toEventTarget(Window, &page.window),
+            &evt.proto,
+        ) catch |err| {
+            log.err(.app, "dispatch popstate event error", .{
+                .err = err,
+                .type = "popstate",
+                .source = "history",
+            });
+        };
+    }
+};
+
+const testing = @import("../../testing.zig");
+test "Browser: HTML.History" {
+    try testing.htmlRunner("html/history/history.html");
+    try testing.htmlRunner("html/history/history2.html");
+}

src/browser/html/document.zig

@@ -42,12 +42,12 @@ pub const HTMLDocument = struct {
     // JS funcs
     // --------
 
-    pub fn get_domain(self: *parser.DocumentHTML, page: *Page) ![]const u8 {
+    pub fn get_domain(self: *parser.DocumentHTML) ![]const u8 {
         // libdom's document_html get_domain always returns null, this is
         // the way MDN recommends getting the domain anyways, since document.domain
         // is deprecated.
         const location = try parser.documentHTMLGetLocation(Location, self) orelse return "";
-        return location.get_host(page);
+        return location.get_host();
     }
 
     pub fn set_domain(_: *parser.DocumentHTML, _: []const u8) ![]const u8 {
@@ -115,67 +115,69 @@ pub const HTMLDocument = struct {
     }
 
     pub fn _getElementsByName(self: *parser.DocumentHTML, name: []const u8, page: *Page) !NodeList {
-        const arena = page.arena;
         var list: NodeList = .{};
 
-        if (name.len == 0) return list;
+        if (name.len == 0) {
+            return list;
+        }
 
         const root = parser.documentHTMLToNode(self);
-        var c = try collection.HTMLCollectionByName(arena, root, name, .{
+        var c = try collection.HTMLCollectionByName(root, name, .{
             .include_root = false,
         });
 
         const ln = try c.get_length();
+        try list.ensureTotalCapacity(page.arena, ln);
+
         var i: u32 = 0;
-        while (i < ln) {
+        while (i < ln) : (i += 1) {
             const n = try c.item(i) orelse break;
-            try list.append(arena, n);
-            i += 1;
+            list.appendAssumeCapacity(n);
         }
 
         return list;
     }
 
-    pub fn get_images(self: *parser.DocumentHTML, page: *Page) !collection.HTMLCollection {
-        return try collection.HTMLCollectionByTagName(page.arena, parser.documentHTMLToNode(self), "img", .{
+    pub fn get_images(self: *parser.DocumentHTML) collection.HTMLCollection {
+        return collection.HTMLCollectionByTagName(parser.documentHTMLToNode(self), "img", .{
             .include_root = false,
         });
     }
 
-    pub fn get_embeds(self: *parser.DocumentHTML, page: *Page) !collection.HTMLCollection {
-        return try collection.HTMLCollectionByTagName(page.arena, parser.documentHTMLToNode(self), "embed", .{
+    pub fn get_embeds(self: *parser.DocumentHTML) collection.HTMLCollection {
+        return collection.HTMLCollectionByTagName(parser.documentHTMLToNode(self), "embed", .{
             .include_root = false,
         });
     }
 
-    pub fn get_plugins(self: *parser.DocumentHTML, page: *Page) !collection.HTMLCollection {
-        return get_embeds(self, page);
+    pub fn get_plugins(self: *parser.DocumentHTML) collection.HTMLCollection {
+        return get_embeds(self);
     }
 
-    pub fn get_forms(self: *parser.DocumentHTML, page: *Page) !collection.HTMLCollection {
-        return try collection.HTMLCollectionByTagName(page.arena, parser.documentHTMLToNode(self), "form", .{
+    pub fn get_forms(self: *parser.DocumentHTML) collection.HTMLCollection {
+        return collection.HTMLCollectionByTagName(parser.documentHTMLToNode(self), "form", .{
             .include_root = false,
         });
     }
 
-    pub fn get_scripts(self: *parser.DocumentHTML, page: *Page) !collection.HTMLCollection {
-        return try collection.HTMLCollectionByTagName(page.arena, parser.documentHTMLToNode(self), "script", .{
+    pub fn get_scripts(self: *parser.DocumentHTML) collection.HTMLCollection {
+        return collection.HTMLCollectionByTagName(parser.documentHTMLToNode(self), "script", .{
             .include_root = false,
         });
     }
 
-    pub fn get_applets(_: *parser.DocumentHTML) !collection.HTMLCollection {
-        return try collection.HTMLCollectionEmpty();
+    pub fn get_applets(_: *parser.DocumentHTML) collection.HTMLCollection {
+        return collection.HTMLCollectionEmpty();
     }
 
-    pub fn get_links(self: *parser.DocumentHTML) !collection.HTMLCollection {
-        return try collection.HTMLCollectionByLinks(parser.documentHTMLToNode(self), .{
+    pub fn get_links(self: *parser.DocumentHTML) collection.HTMLCollection {
+        return collection.HTMLCollectionByLinks(parser.documentHTMLToNode(self), .{
             .include_root = false,
         });
     }
 
-    pub fn get_anchors(self: *parser.DocumentHTML) !collection.HTMLCollection {
-        return try collection.HTMLCollectionByAnchors(parser.documentHTMLToNode(self), .{
+    pub fn get_anchors(self: *parser.DocumentHTML) collection.HTMLCollection {
+        return collection.HTMLCollectionByAnchors(parser.documentHTMLToNode(self), .{
             .include_root = false,
         });
     }
@@ -193,7 +195,7 @@ pub const HTMLDocument = struct {
     }
 
     pub fn set_location(_: *const parser.DocumentHTML, url: []const u8, page: *Page) !void {
-        return page.navigateFromWebAPI(url, .{ .reason = .script });
+        return page.navigateFromWebAPI(url, .{ .reason = .script }, .{ .push = null });
     }
 
     pub fn get_designMode(_: *parser.DocumentHTML) []const u8 {

src/browser/html/elements.zig

@@ -18,9 +18,9 @@
 const std = @import("std");
 const log = @import("../../log.zig");
 
+const js = @import("../js/js.zig");
 const parser = @import("../netsurf.zig");
-const generate = @import("../../runtime/generate.zig");
-const Env = @import("../env.zig").Env;
+const generate = @import("../js/generate.zig");
 const Page = @import("../page.zig").Page;
 
 const urlStitch = @import("../../url.zig").URL.stitch;
@@ -32,6 +32,10 @@ const DataSet = @import("DataSet.zig");
 
 const StyleSheet = @import("../cssom/StyleSheet.zig");
 const CSSStyleDeclaration = @import("../cssom/CSSStyleDeclaration.zig");
+const CanvasRenderingContext2D = @import("../canvas/CanvasRenderingContext2D.zig");
+const WebGLRenderingContext = @import("../canvas/WebGLRenderingContext.zig");
+
+const WalkerChildren = @import("../dom/walker.zig").WalkerChildren;
 
 // HTMLElement interfaces
 pub const Interfaces = .{
@@ -133,14 +137,14 @@ pub const HTMLElement = struct {
 
     pub fn get_innerText(e: *parser.ElementHTML) ![]const u8 {
         const n = @as(*parser.Node, @ptrCast(e));
-        return try parser.nodeTextContent(n) orelse "";
+        return parser.nodeTextContent(n) orelse "";
     }
 
     pub fn set_innerText(e: *parser.ElementHTML, s: []const u8) !void {
         const n = @as(*parser.Node, @ptrCast(e));
 
         // create text node.
-        const doc = try parser.nodeOwnerDocument(n) orelse return error.NoDocument;
+        const doc = parser.nodeOwnerDocument(n) orelse return error.NoDocument;
         const t = try parser.documentCreateTextNode(doc, s);
 
         // remove existing children.
@@ -167,12 +171,12 @@ pub const HTMLElement = struct {
         focusVisible: bool,
     };
     pub fn _focus(e: *parser.ElementHTML, _: ?FocusOpts, page: *Page) !void {
-        if (!try page.isNodeAttached(@ptrCast(e))) {
+        if (!page.isNodeAttached(@ptrCast(e))) {
             return;
         }
 
         const Document = @import("../dom/document.zig").Document;
-        const root_node = try parser.nodeGetRootNode(@ptrCast(e));
+        const root_node = parser.nodeGetRootNode(@ptrCast(e));
         try Document.setFocus(@ptrCast(root_node), e, page);
     }
 };
@@ -218,40 +222,40 @@ pub const HTMLAnchorElement = struct {
     }
 
     pub fn get_href(self: *parser.Anchor) ![]const u8 {
-        return try parser.anchorGetHref(self);
+        return parser.anchorGetHref(self);
     }
 
     pub fn set_href(self: *parser.Anchor, href: []const u8, page: *const Page) !void {
         const full = try urlStitch(page.call_arena, href, page.url.raw, .{});
-        return try parser.anchorSetHref(self, full);
+        return parser.anchorSetHref(self, full);
     }
 
     pub fn get_hreflang(self: *parser.Anchor) ![]const u8 {
-        return try parser.anchorGetHrefLang(self);
+        return parser.anchorGetHrefLang(self);
     }
 
     pub fn set_hreflang(self: *parser.Anchor, href: []const u8) !void {
-        return try parser.anchorSetHrefLang(self, href);
+        return parser.anchorSetHrefLang(self, href);
     }
 
     pub fn get_type(self: *parser.Anchor) ![]const u8 {
-        return try parser.anchorGetType(self);
+        return parser.anchorGetType(self);
     }
 
     pub fn set_type(self: *parser.Anchor, t: []const u8) !void {
-        return try parser.anchorSetType(self, t);
+        return parser.anchorSetType(self, t);
     }
 
     pub fn get_rel(self: *parser.Anchor) ![]const u8 {
-        return try parser.anchorGetRel(self);
+        return parser.anchorGetRel(self);
     }
 
     pub fn set_rel(self: *parser.Anchor, t: []const u8) !void {
-        return try parser.anchorSetRel(self, t);
+        return parser.anchorSetRel(self, t);
     }
 
     pub fn get_text(self: *parser.Anchor) !?[]const u8 {
-        return try parser.nodeTextContent(parser.anchorToNode(self));
+        return parser.nodeTextContent(parser.anchorToNode(self));
     }
 
     pub fn set_text(self: *parser.Anchor, v: []const u8) !void {
@@ -269,182 +273,175 @@ pub const HTMLAnchorElement = struct {
         if (try parser.elementGetAttribute(@ptrCast(@alignCast(self)), "href")) |href| {
             return URL.constructor(.{ .string = href }, null, page); // TODO inject base url
         }
-        return .empty;
+        return error.NotProvided;
     }
 
-    // TODO return a disposable string
     pub fn get_origin(self: *parser.Anchor, page: *Page) ![]const u8 {
-        var u = try url(self, page);
-        return try u.get_origin(page);
+        var u = url(self, page) catch return "";
+        defer u.destructor();
+        return u.get_origin(page);
     }
 
-    // TODO return a disposable string
     pub fn get_protocol(self: *parser.Anchor, page: *Page) ![]const u8 {
-        var u = try url(self, page);
-        return u.get_protocol(page);
+        var u = url(self, page) catch return "";
+        defer u.destructor();
+
+        return page.call_arena.dupe(u8, u.get_protocol());
     }
 
-    pub fn set_protocol(self: *parser.Anchor, v: []const u8, page: *Page) !void {
-        const arena = page.arena;
+    pub fn set_protocol(self: *parser.Anchor, protocol: []const u8, page: *Page) !void {
         var u = try url(self, page);
+        defer u.destructor();
+        try u.set_protocol(protocol);
 
-        u.uri.scheme = v;
-        const href = try u.toString(arena);
-        try parser.anchorSetHref(self, href);
+        const href = try u._toString(page);
+        return parser.anchorSetHref(self, href);
     }
 
-    // TODO return a disposable string
     pub fn get_host(self: *parser.Anchor, page: *Page) ![]const u8 {
-        var u = try url(self, page);
-        return try u.get_host(page);
+        var u = url(self, page) catch return "";
+        defer u.destructor();
+
+        return page.call_arena.dupe(u8, u.get_host());
     }
 
-    pub fn set_host(self: *parser.Anchor, v: []const u8, page: *Page) !void {
-        // search : separator
-        var p: ?u16 = null;
-        var h: []const u8 = undefined;
-        for (v, 0..) |c, i| {
-            if (c == ':') {
-                h = v[0..i];
-                p = try std.fmt.parseInt(u16, v[i + 1 ..], 10);
-                break;
-            }
-        }
-
-        const arena = page.arena;
+    pub fn set_host(self: *parser.Anchor, host: []const u8, page: *Page) !void {
         var u = try url(self, page);
+        defer u.destructor();
+        try u.set_host(host);
 
-        if (p) |pp| {
-            u.uri.host = .{ .raw = h };
-            u.uri.port = pp;
-        } else {
-            u.uri.host = .{ .raw = v };
-            u.uri.port = null;
-        }
-
-        const href = try u.toString(arena);
-        try parser.anchorSetHref(self, href);
+        const href = try u._toString(page);
+        return parser.anchorSetHref(self, href);
     }
 
     pub fn get_hostname(self: *parser.Anchor, page: *Page) ![]const u8 {
-        var u = try url(self, page);
-        return u.get_hostname();
+        var u = url(self, page) catch return "";
+        defer u.destructor();
+        return page.call_arena.dupe(u8, u.get_hostname());
     }
 
-    pub fn set_hostname(self: *parser.Anchor, v: []const u8, page: *Page) !void {
-        const arena = page.arena;
+    pub fn set_hostname(self: *parser.Anchor, hostname: []const u8, page: *Page) !void {
         var u = try url(self, page);
-        u.uri.host = .{ .raw = v };
-        const href = try u.toString(arena);
-        try parser.anchorSetHref(self, href);
+        defer u.destructor();
+        try u.set_hostname(hostname);
+
+        const href = try u._toString(page);
+        return parser.anchorSetHref(self, href);
     }
 
-    // TODO return a disposable string
     pub fn get_port(self: *parser.Anchor, page: *Page) ![]const u8 {
-        var u = try url(self, page);
-        return try u.get_port(page);
+        var u = url(self, page) catch return "";
+        defer u.destructor();
+        return page.call_arena.dupe(u8, u.get_port());
     }
 
-    pub fn set_port(self: *parser.Anchor, v: ?[]const u8, page: *Page) !void {
-        const arena = page.arena;
+    pub fn set_port(self: *parser.Anchor, maybe_port: ?[]const u8, page: *Page) !void {
         var u = try url(self, page);
+        defer u.destructor();
 
-        if (v != null and v.?.len > 0) {
-            u.uri.port = try std.fmt.parseInt(u16, v.?, 10);
+        if (maybe_port) |port| {
+            try u.set_port(port);
         } else {
-            u.uri.port = null;
+            u.clearPort();
         }
 
-        const href = try u.toString(arena);
-        try parser.anchorSetHref(self, href);
+        const href = try u._toString(page);
+        return parser.anchorSetHref(self, href);
     }
 
-    // TODO return a disposable string
     pub fn get_username(self: *parser.Anchor, page: *Page) ![]const u8 {
-        var u = try url(self, page);
-        return u.get_username();
-    }
+        var u = url(self, page) catch return "";
+        defer u.destructor();
 
-    pub fn set_username(self: *parser.Anchor, v: ?[]const u8, page: *Page) !void {
-        const arena = page.arena;
-        var u = try url(self, page);
-
-        if (v) |vv| {
-            u.uri.user = .{ .raw = vv };
-        } else {
-            u.uri.user = null;
+        const username = u.get_username();
+        if (username.len == 0) {
+            return "";
         }
-        const href = try u.toString(arena);
 
-        try parser.anchorSetHref(self, href);
+        return page.call_arena.dupe(u8, username);
+    }
+
+    pub fn set_username(self: *parser.Anchor, maybe_username: ?[]const u8, page: *Page) !void {
+        var u = try url(self, page);
+        defer u.destructor();
+
+        const username = if (maybe_username) |username| username else "";
+        try u.set_username(username);
+
+        const href = try u._toString(page);
+        return parser.anchorSetHref(self, href);
     }
 
-    // TODO return a disposable string
     pub fn get_password(self: *parser.Anchor, page: *Page) ![]const u8 {
-        var u = try url(self, page);
-        return try page.arena.dupe(u8, u.get_password());
+        var u = url(self, page) catch return "";
+        defer u.destructor();
+
+        return page.call_arena.dupe(u8, u.get_password());
     }
 
-    pub fn set_password(self: *parser.Anchor, v: ?[]const u8, page: *Page) !void {
-        const arena = page.arena;
+    pub fn set_password(self: *parser.Anchor, maybe_password: ?[]const u8, page: *Page) !void {
         var u = try url(self, page);
+        defer u.destructor();
 
-        if (v) |vv| {
-            u.uri.password = .{ .raw = vv };
-        } else {
-            u.uri.password = null;
-        }
-        const href = try u.toString(arena);
+        const password = if (maybe_password) |password| password else "";
+        try u.set_password(password);
 
-        try parser.anchorSetHref(self, href);
+        const href = try u._toString(page);
+        return parser.anchorSetHref(self, href);
     }
 
-    // TODO return a disposable string
     pub fn get_pathname(self: *parser.Anchor, page: *Page) ![]const u8 {
-        var u = try url(self, page);
-        return u.get_pathname();
+        var u = url(self, page) catch return "";
+        defer u.destructor();
+
+        return page.call_arena.dupe(u8, u.get_pathname());
     }
 
-    pub fn set_pathname(self: *parser.Anchor, v: []const u8, page: *Page) !void {
-        const arena = page.arena;
+    pub fn set_pathname(self: *parser.Anchor, pathname: []const u8, page: *Page) !void {
         var u = try url(self, page);
-        u.uri.path = .{ .raw = v };
-        const href = try u.toString(arena);
+        defer u.destructor();
 
-        try parser.anchorSetHref(self, href);
+        try u.set_pathname(pathname);
+
+        const href = try u._toString(page);
+        return parser.anchorSetHref(self, href);
     }
 
     pub fn get_search(self: *parser.Anchor, page: *Page) ![]const u8 {
-        var u = try url(self, page);
-        return try u.get_search(page);
+        var u = url(self, page) catch return "";
+        defer u.destructor();
+        // This allocates in page arena so no need to dupe.
+        return u.get_search(page);
     }
 
     pub fn set_search(self: *parser.Anchor, v: ?[]const u8, page: *Page) !void {
         var u = try url(self, page);
+        defer u.destructor();
         try u.set_search(v, page);
 
-        const href = try u.toString(page.call_arena);
-        try parser.anchorSetHref(self, href);
+        const href = try u._toString(page);
+        return parser.anchorSetHref(self, href);
     }
 
-    // TODO return a disposable string
     pub fn get_hash(self: *parser.Anchor, page: *Page) ![]const u8 {
-        var u = try url(self, page);
-        return try u.get_hash(page);
+        var u = url(self, page) catch return "";
+        defer u.destructor();
+
+        return page.call_arena.dupe(u8, u.get_hash());
     }
 
-    pub fn set_hash(self: *parser.Anchor, v: ?[]const u8, page: *Page) !void {
-        const arena = page.arena;
+    pub fn set_hash(self: *parser.Anchor, maybe_hash: ?[]const u8, page: *Page) !void {
         var u = try url(self, page);
+        defer u.destructor();
 
-        if (v) |vv| {
-            u.uri.fragment = .{ .raw = vv };
+        if (maybe_hash) |hash| {
+            try u.set_hash(hash);
         } else {
-            u.uri.fragment = null;
+            u.clearHash();
         }
-        const href = try u.toString(arena);
 
-        try parser.anchorSetHref(self, href);
+        const href = try u._toString(page);
+        return parser.anchorSetHref(self, href);
     }
 };
 
@@ -494,6 +491,29 @@ pub const HTMLCanvasElement = struct {
     pub const Self = parser.Canvas;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    /// This should be a union once we support other context types.
+    const ContextAttributes = struct {
+        alpha: bool,
+        color_space: []const u8 = "srgb",
+    };
+
+    /// Returns a drawing context on the canvas, or null if the context identifier
+    /// is not supported, or the canvas has already been set to a different context mode.
+    pub fn _getContext(
+        ctx_type: []const u8,
+        _: ?ContextAttributes,
+    ) ?union(enum) { @"2d": CanvasRenderingContext2D, webgl: WebGLRenderingContext } {
+        if (std.mem.eql(u8, ctx_type, "2d")) {
+            return .{ .@"2d" = .{} };
+        }
+
+        if (std.mem.eql(u8, ctx_type, "webgl") or std.mem.eql(u8, ctx_type, "experimental-webgl")) {
+            return .{ .webgl = .{} };
+        }
+
+        return null;
+    }
 };
 
 pub const HTMLDListElement = struct {
@@ -732,6 +752,9 @@ pub const HTMLInputElement = struct {
     pub fn set_value(self: *parser.Input, value: []const u8) !void {
         try parser.inputSetValue(self, value);
     }
+    pub fn _select(_: *parser.Input) void {
+        log.debug(.web_api, "not implemented", .{ .feature = "HTMLInputElement select" });
+    }
 };
 
 pub const HTMLLIElement = struct {
@@ -757,13 +780,21 @@ pub const HTMLLinkElement = struct {
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
 
+    pub fn get_rel(self: *parser.Link) ![]const u8 {
+        return parser.linkGetRel(self);
+    }
+
+    pub fn set_rel(self: *parser.Link, rel: []const u8) !void {
+        return parser.linkSetRel(self, rel);
+    }
+
     pub fn get_href(self: *parser.Link) ![]const u8 {
-        return try parser.linkGetHref(self);
+        return parser.linkGetHref(self);
     }
 
     pub fn set_href(self: *parser.Link, href: []const u8, page: *const Page) !void {
         const full = try urlStitch(page.call_arena, href, page.url.raw, .{});
-        return try parser.linkSetHref(self, full);
+        return parser.linkSetHref(self, full);
     }
 };
 
@@ -879,7 +910,7 @@ pub const HTMLScriptElement = struct {
             //    s.src = '...';
             // This should load the script.
             // addFromElement protects against double execution.
-            try page.script_manager.addFromElement(@ptrCast(@alignCast(self)));
+            try page.script_manager.addFromElement(@ptrCast(@alignCast(self)), "dynamic");
         }
     }
 
@@ -992,22 +1023,22 @@ pub const HTMLScriptElement = struct {
         );
     }
 
-    pub fn get_onload(self: *parser.Script, page: *Page) !?Env.Function {
+    pub fn get_onload(self: *parser.Script, page: *Page) !?js.Function {
         const state = page.getNodeState(@ptrCast(@alignCast(self))) orelse return null;
         return state.onload;
     }
 
-    pub fn set_onload(self: *parser.Script, function: ?Env.Function, page: *Page) !void {
+    pub fn set_onload(self: *parser.Script, function: ?js.Function, page: *Page) !void {
         const state = try page.getOrCreateNodeState(@ptrCast(@alignCast(self)));
         state.onload = function;
     }
 
-    pub fn get_onerror(self: *parser.Script, page: *Page) !?Env.Function {
+    pub fn get_onerror(self: *parser.Script, page: *Page) !?js.Function {
         const state = page.getNodeState(@ptrCast(@alignCast(self))) orelse return null;
         return state.onerror;
     }
 
-    pub fn set_onerror(self: *parser.Script, function: ?Env.Function, page: *Page) !void {
+    pub fn set_onerror(self: *parser.Script, function: ?js.Function, page: *Page) !void {
         const state = try page.getOrCreateNodeState(@ptrCast(@alignCast(self)));
         state.onerror = function;
     }
@@ -1042,68 +1073,84 @@ pub const HTMLSlotElement = struct {
         flatten: bool = false,
     };
     pub fn _assignedNodes(self: *parser.Slot, opts_: ?AssignedNodesOpts, page: *Page) ![]NodeUnion {
-        const opts = opts_ orelse AssignedNodesOpts{ .flatten = false };
-
-        if (try findAssignedSlotNodes(self, opts, page)) |nodes| {
-            return nodes;
-        }
-
-        if (!opts.flatten) {
-            return &.{};
-        }
-
-        const node: *parser.Node = @ptrCast(@alignCast(self));
-        const nl = try parser.nodeGetChildNodes(node);
-        const len = try parser.nodeListLength(nl);
-        if (len == 0) {
-            return &.{};
-        }
-
-        var assigned = try page.call_arena.alloc(NodeUnion, len);
-        var i: usize = 0;
-        while (true) : (i += 1) {
-            const child = try parser.nodeListItem(nl, @intCast(i)) orelse break;
-            assigned[i] = try Node.toInterface(child);
-        }
-        return assigned[0..i];
+        return findAssignedSlotNodes(self, opts_, false, page);
     }
 
-    fn findAssignedSlotNodes(self: *parser.Slot, opts: AssignedNodesOpts, page: *Page) !?[]NodeUnion {
+    // This should return Union, instead of NodeUnion, but we want to re-use
+    // findAssignedSlotNodes. Returning NodeUnion is fine, as long as every element
+    // within is an Element. This could be more efficient
+    pub fn _assignedElements(self: *parser.Slot, opts_: ?AssignedNodesOpts, page: *Page) ![]NodeUnion {
+        return findAssignedSlotNodes(self, opts_, true, page);
+    }
+
+    fn findAssignedSlotNodes(self: *parser.Slot, opts_: ?AssignedNodesOpts, element_only: bool, page: *Page) ![]NodeUnion {
+        const opts = opts_ orelse AssignedNodesOpts{ .flatten = false };
+
         if (opts.flatten) {
-            log.warn(.web_api, "not implemented", .{ .feature = "HTMLSlotElement flatten assignedNodes" });
+            log.debug(.web_api, "not implemented", .{ .feature = "HTMLSlotElement flatten assignedNodes" });
         }
 
-        const slot_name = try parser.elementGetAttribute(@ptrCast(@alignCast(self)), "name");
         const node: *parser.Node = @ptrCast(@alignCast(self));
-        var root = try parser.nodeGetRootNode(node);
-        if (page.getNodeState(root)) |state| {
-            if (state.shadow_root) |sr| {
-                root = @ptrCast(@alignCast(sr.host));
-            }
-        }
 
-        var arr: std.ArrayList(NodeUnion) = .empty;
-        const w = @import("../dom/walker.zig").WalkerChildren{};
-        var next: ?*parser.Node = null;
-        while (true) {
-            next = try w.get_next(root, next) orelse break;
-            if (try parser.nodeType(next.?) != .element) {
-                if (slot_name == null) {
-                    // default slot (with no name), takes everything
-                    try arr.append(page.call_arena, try Node.toInterface(next.?));
+        // First we look for any explicitly assigned nodes (via the slot attribute)
+        {
+            const slot_name = try parser.elementGetAttribute(@ptrCast(@alignCast(self)), "name");
+            var root = parser.nodeGetRootNode(node);
+            if (page.getNodeState(root)) |state| {
+                if (state.shadow_root) |sr| {
+                    root = @ptrCast(@alignCast(sr.host));
                 }
-                continue;
             }
-            const el: *parser.Element = @ptrCast(@alignCast(next.?));
-            const element_slot = try parser.elementGetAttribute(el, "slot");
 
-            if (nullableStringsAreEqual(slot_name, element_slot)) {
-                // either they're the same string or they are both null
-                try arr.append(page.call_arena, try Node.toInterface(next.?));
-                continue;
+            var arr: std.ArrayList(NodeUnion) = .empty;
+            const w = @import("../dom/walker.zig").WalkerChildren{};
+            var next: ?*parser.Node = null;
+            while (true) {
+                next = try w.get_next(root, next) orelse break;
+                if (parser.nodeType(next.?) != .element) {
+                    if (slot_name == null and !element_only) {
+                        // default slot (with no name), takes everything
+                        try arr.append(page.call_arena, try Node.toInterface(next.?));
+                    }
+                    continue;
+                }
+                const el: *parser.Element = @ptrCast(@alignCast(next.?));
+                const element_slot = try parser.elementGetAttribute(el, "slot");
+
+                if (nullableStringsAreEqual(slot_name, element_slot)) {
+                    // either they're the same string or they are both null
+                    try arr.append(page.call_arena, try Node.toInterface(next.?));
+                    continue;
+                }
+            }
+            if (arr.items.len > 0) {
+                return arr.items;
+            }
+
+            if (!opts.flatten) {
+                return &.{};
             }
         }
-        return if (arr.items.len == 0) null else arr.items;
+
+        // Since, we have no explicitly assigned nodes and flatten == false,
+        // we'll collect the children of the slot - the defaults.
+        {
+            const nl = try parser.nodeGetChildNodes(node);
+            const len = parser.nodeListLength(nl);
+            if (len == 0) {
+                return &.{};
+            }
+
+            var assigned = try page.call_arena.alloc(NodeUnion, len);
+            var i: usize = 0;
+            while (true) : (i += 1) {
+                const child = parser.nodeListItem(nl, @intCast(i)) orelse break;
+                if (!element_only or parser.nodeType(child) == .element) {
+                    assigned[i] = try Node.toInterface(child);
+                }
+            }
+            return assigned[0..i];
+        }
     }
 
     fn nullableStringsAreEqual(a: ?[]const u8, b: ?[]const u8) bool {
@@ -1180,11 +1227,22 @@ pub const HTMLTemplateElement = struct {
     pub const subtype = .node;
 
     pub fn get_content(self: *parser.Template, page: *Page) !*parser.DocumentFragment {
-        const state = try page.getOrCreateNodeState(@ptrCast(@alignCast(self)));
+        const n: *parser.Node = @ptrCast(@alignCast(self));
+        const state = try page.getOrCreateNodeState(n);
         if (state.template_content) |tc| {
             return tc;
         }
         const tc = try parser.documentCreateDocumentFragment(@ptrCast(page.window.document));
+        const ntc: *parser.Node = @ptrCast(@alignCast(tc));
+
+        // move existing template's childnodes to the fragment.
+        const walker = WalkerChildren{};
+        var next: ?*parser.Node = null;
+        while (true) {
+            next = try walker.get_next(n, next) orelse break;
+            _ = try parser.nodeAppendChild(ntc, next.?);
+        }
+
         state.template_content = tc;
         return tc;
     }
@@ -1327,41 +1385,16 @@ test "Browser: HTML.HtmlStyleElement" {
 test "Browser: HTML.HtmlScriptElement" {
     try testing.htmlRunner("html/script/script.html");
     try testing.htmlRunner("html/script/inline_defer.html");
+    try testing.htmlRunner("html/script/import.html");
+    try testing.htmlRunner("html/script/dynamic_import.html");
+    try testing.htmlRunner("html/script/importmap.html");
+    try testing.htmlRunner("html/script/order.html");
 }
 
-test "Browser: HTML.HTMLSlotElement" {
-    try testing.htmlRunner("html/html_slot_element.html");
+test "Browser: HTML.HtmlSlotElement" {
+    try testing.htmlRunner("html/slot.html");
 }
 
-const Check = struct {
-    input: []const u8,
-    expected: ?[]const u8 = null, // Needed when input != expected
-};
-const bool_valids = [_]Check{
-    .{ .input = "true" },
-    .{ .input = "''", .expected = "false" },
-    .{ .input = "13.5", .expected = "true" },
-};
-const str_valids = [_]Check{
-    .{ .input = "'foo'", .expected = "foo" },
-    .{ .input = "5", .expected = "5" },
-    .{ .input = "''", .expected = "" },
-    .{ .input = "document", .expected = "[object HTMLDocument]" },
-};
-
-// .{ "elem.type = '5'", "5" },
-// .{ "elem.type", "text" },
-fn testProperty(
-    arena: std.mem.Allocator,
-    runner: *testing.JsRunner,
-    elem_dot_prop: []const u8,
-    always: ?[]const u8, // Ignores checks' expected if set
-    checks: []const Check,
-) !void {
-    for (checks) |check| {
-        try runner.testCases(&.{
-            .{ try std.mem.concat(arena, u8, &.{ elem_dot_prop, " = ", check.input }), null },
-            .{ elem_dot_prop, always orelse check.expected orelse check.input },
-        }, .{});
-    }
+test "Browser: HTML.HTMLCanvasElement" {
+    try testing.htmlRunner("html/canvas.html");
 }

src/browser/html/error_event.zig

@@ -15,7 +15,7 @@
 //
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
-const Env = @import("../env.zig").Env;
+const js = @import("../js/js.zig");
 const parser = @import("../netsurf.zig");
 
 // https://developer.mozilla.org/en-US/docs/Web/API/ErrorEvent
@@ -28,21 +28,21 @@ pub const ErrorEvent = struct {
     filename: []const u8,
     lineno: i32,
     colno: i32,
-    @"error": ?Env.JsObject,
+    @"error": ?js.Object,
 
     const ErrorEventInit = struct {
         message: []const u8 = "",
         filename: []const u8 = "",
         lineno: i32 = 0,
         colno: i32 = 0,
-        @"error": ?Env.JsObject = null,
+        @"error": ?js.Object = null,
     };
 
     pub fn constructor(event_type: []const u8, opts: ?ErrorEventInit) !ErrorEvent {
         const event = try parser.eventCreate();
         defer parser.eventDestroy(event);
         try parser.eventInit(event, event_type, .{});
-        parser.eventSetInternalType(event, .event);
+        parser.eventSetInternalType(event, .error_event);
 
         const o = opts orelse ErrorEventInit{};
 
@@ -72,7 +72,7 @@ pub const ErrorEvent = struct {
         return self.colno;
     }
 
-    pub fn get_error(self: *const ErrorEvent) Env.UndefinedOr(Env.JsObject) {
+    pub fn get_error(self: *const ErrorEvent) js.UndefinedOr(js.Object) {
         if (self.@"error") |e| {
             return .{ .value = e };
         }

src/browser/html/form.zig

@@ -21,7 +21,6 @@ const Allocator = std.mem.Allocator;
 const parser = @import("../netsurf.zig");
 const Page = @import("../page.zig").Page;
 const HTMLElement = @import("elements.zig").HTMLElement;
-const FormData = @import("../xhr/form_data.zig").FormData;
 
 pub const HTMLFormElement = struct {
     pub const Self = parser.Form;

src/browser/html/history.zig

@@ -1,93 +0,0 @@
-// Copyright (C) 2023-2024  Lightpanda (Selecy SAS)
-//
-// Francis Bouvier <francis@lightpanda.io>
-// Pierre Tachoire <pierre@lightpanda.io>
-//
-// This program is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Affero General Public License as
-// published by the Free Software Foundation, either version 3 of the
-// License, or (at your option) any later version.
-//
-// This program is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU Affero General Public License for more details.
-//
-// You should have received a copy of the GNU Affero General Public License
-// along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-const std = @import("std");
-
-// https://html.spec.whatwg.org/multipage/nav-history-apis.html#the-history-interface
-pub const History = struct {
-    const ScrollRestorationMode = enum {
-        auto,
-        manual,
-    };
-
-    scrollRestoration: ScrollRestorationMode = .auto,
-    state: std.json.Value = .null,
-
-    // count tracks the history length until we implement correctly pushstate.
-    count: u32 = 0,
-
-    pub fn get_length(self: *History) u32 {
-        // TODO return the real history length value.
-        return self.count;
-    }
-
-    pub fn get_scrollRestoration(self: *History) []const u8 {
-        return switch (self.scrollRestoration) {
-            .auto => "auto",
-            .manual => "manual",
-        };
-    }
-
-    pub fn set_scrollRestoration(self: *History, mode: []const u8) void {
-        if (std.mem.eql(u8, "manual", mode)) self.scrollRestoration = .manual;
-        if (std.mem.eql(u8, "auto", mode)) self.scrollRestoration = .auto;
-    }
-
-    pub fn get_state(self: *History) std.json.Value {
-        return self.state;
-    }
-
-    // TODO implement the function
-    // data must handle any argument. We could expect a std.json.Value but
-    // https://github.com/lightpanda-io/zig-js-runtime/issues/267 is missing.
-    pub fn _pushState(self: *History, data: []const u8, _: ?[]const u8, url: ?[]const u8) void {
-        self.count += 1;
-        _ = url;
-        _ = data;
-    }
-
-    // TODO implement the function
-    // data must handle any argument. We could expect a std.json.Value but
-    // https://github.com/lightpanda-io/zig-js-runtime/issues/267 is missing.
-    pub fn _replaceState(self: *History, data: []const u8, _: ?[]const u8, url: ?[]const u8) void {
-        _ = self;
-        _ = url;
-        _ = data;
-    }
-
-    // TODO implement the function
-    pub fn _go(self: *History, delta: ?i32) void {
-        _ = self;
-        _ = delta;
-    }
-
-    // TODO implement the function
-    pub fn _back(self: *History) void {
-        _ = self;
-    }
-
-    // TODO implement the function
-    pub fn _forward(self: *History) void {
-        _ = self;
-    }
-};
-
-const testing = @import("../../testing.zig");
-test "Browser: HTML.History" {
-    try testing.htmlRunner("html/history.html");
-}

src/browser/html/html.zig

@@ -21,7 +21,7 @@ const HTMLElem = @import("elements.zig");
 const SVGElem = @import("svg_elements.zig");
 const Window = @import("window.zig").Window;
 const Navigator = @import("navigator.zig").Navigator;
-const History = @import("history.zig").History;
+const History = @import("History.zig");
 const Location = @import("location.zig").Location;
 const MediaQueryList = @import("media_query_list.zig").MediaQueryList;
 

src/browser/html/iframe.zig

@@ -16,10 +16,8 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 const std = @import("std");
-const Allocator = std.mem.Allocator;
 
 const parser = @import("../netsurf.zig");
-const Page = @import("../page.zig").Page;
 const HTMLElement = @import("elements.zig").HTMLElement;
 
 // https://html.spec.whatwg.org/multipage/iframe-embed-object.html#htmliframeelement

src/browser/html/location.zig

@@ -16,73 +16,95 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+const std = @import("std");
 const Page = @import("../page.zig").Page;
-
 const URL = @import("../url/url.zig").URL;
 
 // https://html.spec.whatwg.org/multipage/nav-history-apis.html#the-location-interface
 pub const Location = struct {
-    url: ?URL = null,
+    url: URL,
+
+    /// Initializes the `Location` to be used in `Window`.
+    /// Browsers give such initial values when user not navigated yet:
+    /// Chrome  -> chrome://new-tab-page/
+    /// Firefox -> about:newtab
+    /// Safari  -> favorites://
+    pub fn init(url: []const u8) !Location {
+        return .{ .url = try .initForLocation(url) };
+    }
 
     pub fn get_href(self: *Location, page: *Page) ![]const u8 {
-        if (self.url) |*u| return u.get_href(page);
-        return "";
+        return self.url.get_href(page);
     }
 
-    pub fn get_protocol(self: *Location, page: *Page) ![]const u8 {
-        if (self.url) |*u| return u.get_protocol(page);
-        return "";
+    pub fn set_href(_: *const Location, href: []const u8, page: *Page) !void {
+        return page.navigateFromWebAPI(href, .{ .reason = .script }, .{ .push = null });
     }
 
-    pub fn get_host(self: *Location, page: *Page) ![]const u8 {
-        if (self.url) |*u| return u.get_host(page);
-        return "";
+    pub fn set_hash(_: *const Location, hash: []const u8, page: *Page) !void {
+        const normalized_hash = blk: {
+            if (hash.len == 0) {
+                const old_url = page.url.raw;
+
+                break :blk if (std.mem.indexOfScalar(u8, old_url, '#')) |index|
+                    old_url[0..index]
+                else
+                    old_url;
+            } else if (hash[0] == '#')
+                break :blk hash
+            else
+                break :blk try std.fmt.allocPrint(page.arena, "#{s}", .{hash});
+        };
+
+        return page.navigateFromWebAPI(normalized_hash, .{ .reason = .script }, .{ .replace = null });
+    }
+
+    pub fn get_protocol(self: *Location) []const u8 {
+        return self.url.get_protocol();
+    }
+
+    pub fn get_host(self: *Location) []const u8 {
+        return self.url.get_host();
     }
 
     pub fn get_hostname(self: *Location) []const u8 {
-        if (self.url) |*u| return u.get_hostname();
-        return "";
+        return self.url.get_hostname();
     }
 
-    pub fn get_port(self: *Location, page: *Page) ![]const u8 {
-        if (self.url) |*u| return u.get_port(page);
-        return "";
+    pub fn get_port(self: *Location) []const u8 {
+        return self.url.get_port();
     }
 
     pub fn get_pathname(self: *Location) []const u8 {
-        if (self.url) |*u| return u.get_pathname();
-        return "";
+        return self.url.get_pathname();
     }
 
     pub fn get_search(self: *Location, page: *Page) ![]const u8 {
-        if (self.url) |*u| return u.get_search(page);
-        return "";
+        return self.url.get_search(page);
     }
 
-    pub fn get_hash(self: *Location, page: *Page) ![]const u8 {
-        if (self.url) |*u| return u.get_hash(page);
-        return "";
+    pub fn get_hash(self: *Location) []const u8 {
+        return self.url.get_hash();
     }
 
     pub fn get_origin(self: *Location, page: *Page) ![]const u8 {
-        if (self.url) |*u| return u.get_origin(page);
-        return "";
+        return self.url.get_origin(page);
     }
 
     pub fn _assign(_: *const Location, url: []const u8, page: *Page) !void {
-        return page.navigateFromWebAPI(url, .{ .reason = .script });
+        return page.navigateFromWebAPI(url, .{ .reason = .script }, .{ .push = null });
     }
 
     pub fn _replace(_: *const Location, url: []const u8, page: *Page) !void {
-        return page.navigateFromWebAPI(url, .{ .reason = .script });
+        return page.navigateFromWebAPI(url, .{ .reason = .script }, .{ .replace = null });
     }
 
     pub fn _reload(_: *const Location, page: *Page) !void {
-        return page.navigateFromWebAPI(page.url.raw, .{ .reason = .script });
+        return page.navigateFromWebAPI(page.url.raw, .{ .reason = .script }, .reload);
     }
 
     pub fn _toString(self: *Location, page: *Page) ![]const u8 {
-        return try self.get_href(page);
+        return self.get_href(page);
     }
 };
 

src/browser/html/media_query_list.zig

@@ -16,8 +16,8 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+const js = @import("../js/js.zig");
 const parser = @import("../netsurf.zig");
-const Function = @import("../env.zig").Function;
 const EventTarget = @import("../dom/event_target.zig").EventTarget;
 
 // https://drafts.csswg.org/cssom-view/#the-mediaquerylist-interface
@@ -39,7 +39,7 @@ pub const MediaQueryList = struct {
         return self.media;
     }
 
-    pub fn _addListener(_: *const MediaQueryList, _: Function) void {}
+    pub fn _addListener(_: *const MediaQueryList, _: js.Function) void {}
 
-    pub fn _removeListener(_: *const MediaQueryList, _: Function) void {}
+    pub fn _removeListener(_: *const MediaQueryList, _: js.Function) void {}
 };

src/browser/html/svg_elements.zig

@@ -25,7 +25,7 @@ pub const SVGElement = struct {
     // Currently the prototype chain is not implemented (will not be returned by toInterface())
     // For that we need parser.SvgElement and the derived types with tags in the v-table.
     pub const prototype = *Element;
-    // While this is a Node, could consider not exposing the subtype untill we have
+    // While this is a Node, could consider not exposing the subtype until we have
     // a Self type to cast to.
     pub const subtype = .node;
 };

src/browser/html/window.zig

@@ -18,13 +18,14 @@
 
 const std = @import("std");
 
+const js = @import("../js/js.zig");
 const log = @import("../../log.zig");
 const parser = @import("../netsurf.zig");
-const Env = @import("../env.zig").Env;
 const Page = @import("../page.zig").Page;
 
 const Navigator = @import("navigator.zig").Navigator;
-const History = @import("history.zig").History;
+const History = @import("History.zig");
+const Navigation = @import("../navigation/Navigation.zig");
 const Location = @import("location.zig").Location;
 const Crypto = @import("../crypto/crypto.zig").Crypto;
 const Console = @import("../console/console.zig").Console;
@@ -35,15 +36,15 @@ const CSSStyleDeclaration = @import("../cssom/CSSStyleDeclaration.zig");
 const Screen = @import("screen.zig").Screen;
 const domcss = @import("../dom/css.zig");
 const Css = @import("../css/css.zig").Css;
+const EventHandler = @import("../events/event.zig").EventHandler;
 
-const Function = Env.Function;
-const JsObject = Env.JsObject;
-
-const v8 = @import("v8");
 const Request = @import("../fetch/Request.zig");
 const fetchFn = @import("../fetch/fetch.zig").fetch;
 
 const storage = @import("../storage/storage.zig");
+const ErrorEvent = @import("error_event.zig").ErrorEvent;
+
+const DirectEventHandler = @import("../events/event.zig").DirectEventHandler;
 
 // https://dom.spec.whatwg.org/#interface-window-extensions
 // https://html.spec.whatwg.org/multipage/nav-history-apis.html#window
@@ -55,8 +56,7 @@ pub const Window = struct {
 
     document: *parser.DocumentHTML,
     target: []const u8 = "",
-    history: History = .{},
-    location: Location = .{},
+    location: Location,
     storage_shelf: ?*storage.Shelf = null,
 
     // counter for having unique timer ids
@@ -69,6 +69,10 @@ pub const Window = struct {
     performance: Performance,
     screen: Screen = .{},
     css: Css = .{},
+    scroll_x: u32 = 0,
+    scroll_y: u32 = 0,
+    onload_callback: ?js.Function = null,
+    onpopstate_callback: ?js.Function = null,
 
     pub fn create(target: ?[]const u8, navigator: ?Navigator) !Window {
         var fbs = std.io.fixedBufferStream("");
@@ -79,6 +83,7 @@ pub const Window = struct {
         return .{
             .document = html_doc,
             .target = target orelse "",
+            .location = try .init("about:blank"),
             .navigator = navigator orelse .{},
             .performance = Performance.init(),
         };
@@ -89,6 +94,10 @@ pub const Window = struct {
         try parser.documentHTMLSetLocation(Location, self.document, &self.location);
     }
 
+    pub fn changeLocation(self: *Window, new_url: []const u8, page: *Page) !void {
+        return self.location.url.reinit(new_url, page);
+    }
+
     pub fn replaceDocument(self: *Window, doc: *parser.DocumentHTML) !void {
         self.performance.reset(); // When to reset see: https://developer.mozilla.org/en-US/docs/Web/API/Performance/timeOrigin
         self.document = doc;
@@ -99,16 +108,28 @@ pub const Window = struct {
         self.storage_shelf = shelf;
     }
 
-    pub fn _fetch(_: *Window, input: Request.RequestInput, options: ?Request.RequestInit, page: *Page) !Env.Promise {
+    pub fn _fetch(_: *Window, input: Request.RequestInput, options: ?Request.RequestInit, page: *Page) !js.Promise {
         return fetchFn(input, options, page);
     }
 
-    pub fn get_window(self: *Window) *Window {
-        return self;
+    /// Returns `onload_callback`.
+    pub fn get_onload(self: *const Window) ?js.Function {
+        return self.onload_callback;
     }
 
-    pub fn get_navigator(self: *Window) *Navigator {
-        return &self.navigator;
+    /// Sets `onload_callback`.
+    pub fn set_onload(self: *Window, maybe_listener: ?EventHandler.Listener, page: *Page) !void {
+        try DirectEventHandler(Window, self, "load", maybe_listener, &self.onload_callback, page.arena);
+    }
+
+    /// Returns `onpopstate_callback`.
+    pub fn get_onpopstate(self: *const Window) ?js.Function {
+        return self.onpopstate_callback;
+    }
+
+    /// Sets `onpopstate_callback`.
+    pub fn set_onpopstate(self: *Window, maybe_listener: ?EventHandler.Listener, page: *Page) !void {
+        try DirectEventHandler(Window, self, "popstate", maybe_listener, &self.onpopstate_callback, page.arena);
     }
 
     pub fn get_location(self: *Window) *Location {
@@ -116,23 +137,7 @@ pub const Window = struct {
     }
 
     pub fn set_location(_: *const Window, url: []const u8, page: *Page) !void {
-        return page.navigateFromWebAPI(url, .{ .reason = .script });
-    }
-
-    pub fn get_console(self: *Window) *Console {
-        return &self.console;
-    }
-
-    pub fn get_crypto(self: *Window) *Crypto {
-        return &self.crypto;
-    }
-
-    pub fn get_self(self: *Window) *Window {
-        return self;
-    }
-
-    pub fn get_parent(self: *Window) *Window {
-        return self;
+        return page.navigateFromWebAPI(url, .{ .reason = .script }, .{ .push = null });
     }
 
     // frames return the window itself, but accessing it via a pseudo
@@ -172,16 +177,16 @@ pub const Window = struct {
         return frames.get_length();
     }
 
-    pub fn get_top(self: *Window) *Window {
-        return self;
-    }
-
     pub fn get_document(self: *Window) ?*parser.DocumentHTML {
         return self.document;
     }
 
-    pub fn get_history(self: *Window) *History {
-        return &self.history;
+    pub fn get_history(_: *Window, page: *Page) *History {
+        return &page.session.history;
+    }
+
+    pub fn get_navigation(_: *Window, page: *Page) *Navigation {
+        return &page.session.navigation;
     }
 
     //  The interior height of the window in pixels, including the height of the horizontal scroll bar, if present.
@@ -210,19 +215,11 @@ pub const Window = struct {
         return &self.storage_shelf.?.bucket.session;
     }
 
-    pub fn get_performance(self: *Window) *Performance {
-        return &self.performance;
-    }
-
-    pub fn get_screen(self: *Window) *Screen {
-        return &self.screen;
-    }
-
     pub fn get_CSS(self: *Window) *Css {
         return &self.css;
     }
 
-    pub fn _requestAnimationFrame(self: *Window, cbk: Function, page: *Page) !u32 {
+    pub fn _requestAnimationFrame(self: *Window, cbk: js.Function, page: *Page) !u32 {
         return self.createTimeout(cbk, 5, page, .{
             .animation_frame = true,
             .name = "animationFrame",
@@ -234,11 +231,11 @@ pub const Window = struct {
         _ = self.timers.remove(id);
     }
 
-    pub fn _setTimeout(self: *Window, cbk: Function, delay: ?u32, params: []Env.JsObject, page: *Page) !u32 {
+    pub fn _setTimeout(self: *Window, cbk: js.Function, delay: ?u32, params: []js.Object, page: *Page) !u32 {
         return self.createTimeout(cbk, delay, page, .{ .args = params, .name = "setTimeout" });
     }
 
-    pub fn _setInterval(self: *Window, cbk: Function, delay: ?u32, params: []Env.JsObject, page: *Page) !u32 {
+    pub fn _setInterval(self: *Window, cbk: js.Function, delay: ?u32, params: []js.Object, page: *Page) !u32 {
         return self.createTimeout(cbk, delay, page, .{ .repeat = true, .args = params, .name = "setInterval" });
     }
 
@@ -250,14 +247,22 @@ pub const Window = struct {
         _ = self.timers.remove(id);
     }
 
-    pub fn _queueMicrotask(self: *Window, cbk: Function, page: *Page) !u32 {
-        return self.createTimeout(cbk, 0, page, .{ .name = "queueMicrotask" });
+    pub fn _queueMicrotask(self: *Window, cbk: js.Function, page: *Page) !void {
+        _ = try self.createTimeout(cbk, 0, page, .{ .name = "queueMicrotask" });
     }
 
-    pub fn _matchMedia(_: *const Window, media: []const u8, page: *Page) !MediaQueryList {
+    pub fn _setImmediate(self: *Window, cbk: js.Function, page: *Page) !u32 {
+        return self.createTimeout(cbk, 0, page, .{ .name = "setImmediate" });
+    }
+
+    pub fn _clearImmediate(self: *Window, id: u32) void {
+        _ = self.timers.remove(id);
+    }
+
+    pub fn _matchMedia(_: *const Window, media: js.String) !MediaQueryList {
         return .{
             .matches = false, // TODO?
-            .media = try page.arena.dupe(u8, media),
+            .media = media.string,
         };
     }
 
@@ -276,14 +281,33 @@ pub const Window = struct {
         return out;
     }
 
+    pub fn _reportError(self: *Window, err: js.Object, page: *Page) !void {
+        var error_event = try ErrorEvent.constructor("error", .{
+            .@"error" = err,
+        });
+        _ = try parser.eventTargetDispatchEvent(
+            parser.toEventTarget(Window, self),
+            @as(*parser.Event, &error_event.proto),
+        );
+
+        if (parser.eventDefaultPrevented(&error_event.proto) == false) {
+            const err_string = err.toString() catch "Unknown error";
+            log.info(.user_script, "error", .{
+                .err = err_string,
+                .stack = page.stackTrace() catch "???",
+                .source = "window.reportError",
+            });
+        }
+    }
+
     const CreateTimeoutOpts = struct {
         name: []const u8,
-        args: []Env.JsObject = &.{},
+        args: []js.Object = &.{},
         repeat: bool = false,
         animation_frame: bool = false,
         low_priority: bool = false,
     };
-    fn createTimeout(self: *Window, cbk: Function, delay_: ?u32, page: *Page, opts: CreateTimeoutOpts) !u32 {
+    fn createTimeout(self: *Window, cbk: js.Function, delay_: ?u32, page: *Page, opts: CreateTimeoutOpts) !u32 {
         const delay = delay_ orelse 0;
         if (self.timers.count() > 512) {
             return error.TooManyTimeout;
@@ -303,9 +327,9 @@ pub const Window = struct {
         errdefer _ = self.timers.remove(timer_id);
 
         const args = opts.args;
-        var persisted_args: []Env.JsObject = &.{};
+        var persisted_args: []js.Object = &.{};
         if (args.len > 0) {
-            persisted_args = try page.arena.alloc(Env.JsObject, args.len);
+            persisted_args = try page.arena.alloc(js.Object, args.len);
             for (args, persisted_args) |a, *ca| {
                 ca.* = try a.persist();
             }
@@ -346,12 +370,20 @@ pub const Window = struct {
         const Opts = struct {
             top: i32,
             left: i32,
-            behavior: []const u8,
+            behavior: []const u8 = "",
         };
     };
-    pub fn _scrollTo(self: *Window, opts: ScrollToOpts, y: ?u32) !void {
-        _ = opts;
-        _ = y;
+    pub fn _scrollTo(self: *Window, opts: ScrollToOpts, y: ?i32) !void {
+        switch (opts) {
+            .x => |x| {
+                self.scroll_x = @intCast(@max(x, 0));
+                self.scroll_y = @intCast(@max(0, y orelse 0));
+            },
+            .opts => |o| {
+                self.scroll_y = @intCast(@max(0, o.top));
+                self.scroll_x = @intCast(@max(0, o.left));
+            },
+        }
 
         {
             const scroll_event = try parser.eventCreate();
@@ -375,6 +407,28 @@ pub const Window = struct {
             );
         }
     }
+    pub fn _scroll(self: *Window, opts: ScrollToOpts, y: ?i32) !void {
+        // just an alias for scrollTo
+        return self._scrollTo(opts, y);
+    }
+
+    pub fn get_scrollX(self: *const Window) u32 {
+        return self.scroll_x;
+    }
+
+    pub fn get_scrollY(self: *const Window) u32 {
+        return self.scroll_y;
+    }
+
+    pub fn get_pageXOffset(self: *const Window) u32 {
+        // just an alias for scrollX
+        return self.get_scrollX();
+    }
+
+    pub fn get_pageYOffset(self: *const Window) u32 {
+        // just an alias for scrollY
+        return self.get_scrollY();
+    }
 
     // libdom's document doesn't have a parent, which is correct, but
     // breaks the event bubbling that happens for many events from
@@ -392,6 +446,18 @@ pub const Window = struct {
         // and thus the target has already been set to the document.
         return self.base.redispatchEvent(evt);
     }
+
+    pub fn postAttach(self: *Window, js_this: js.This) !void {
+        try js_this.set("top", self, .{});
+        try js_this.set("self", self, .{});
+        try js_this.set("parent", self, .{});
+        try js_this.set("window", self, .{});
+        try js_this.set("crypto", &self.crypto, .{});
+        try js_this.set("screen", &self.screen, .{});
+        try js_this.set("console", &self.console, .{});
+        try js_this.set("navigator", &self.navigator, .{});
+        try js_this.set("performance", &self.performance, .{});
+    }
 };
 
 const TimerCallback = struct {
@@ -402,13 +468,13 @@ const TimerCallback = struct {
     repeat: ?u32,
 
     // The JavaScript callback to execute
-    cbk: Function,
+    cbk: js.Function,
 
     animation_frame: bool = false,
 
     window: *Window,
 
-    args: []Env.JsObject = &.{},
+    args: []js.Object = &.{},
 
     fn run(ctx: *anyopaque) ?u32 {
         const self: *TimerCallback = @ptrCast(@alignCast(ctx));
@@ -422,7 +488,7 @@ const TimerCallback = struct {
             return null;
         }
 
-        var result: Function.Result = undefined;
+        var result: js.Function.Result = undefined;
 
         var call: anyerror!void = undefined;
         if (self.animation_frame) {

src/browser/js/Caller.zig

@@ -0,0 +1,561 @@
+const std = @import("std");
+const js = @import("js.zig");
+const v8 = js.v8;
+
+const log = @import("../../log.zig");
+const Page = @import("../page.zig").Page;
+
+const types = @import("types.zig");
+const Context = @import("Context.zig");
+
+const Allocator = std.mem.Allocator;
+const ArenaAllocator = std.heap.ArenaAllocator;
+
+const CALL_ARENA_RETAIN = 1024 * 16;
+
+// Responsible for calling Zig functions from JS invocations. This could
+// probably just contained in ExecutionWorld, but having this specific logic, which
+// is somewhat repetitive between constructors, functions, getters, etc contained
+// here does feel like it makes it cleaner.
+const Caller = @This();
+context: *Context,
+v8_context: v8.Context,
+isolate: v8.Isolate,
+call_arena: Allocator,
+
+// info is a v8.PropertyCallbackInfo or a v8.FunctionCallback
+// All we really want from it is the isolate.
+// executor = Isolate -> getCurrentContext -> getEmbedderData()
+pub fn init(info: anytype) Caller {
+    const isolate = info.getIsolate();
+    const v8_context = isolate.getCurrentContext();
+    const context: *Context = @ptrFromInt(v8_context.getEmbedderData(1).castTo(v8.BigInt).getUint64());
+
+    context.call_depth += 1;
+    return .{
+        .context = context,
+        .isolate = isolate,
+        .v8_context = v8_context,
+        .call_arena = context.call_arena,
+    };
+}
+
+pub fn deinit(self: *Caller) void {
+    const context = self.context;
+    const call_depth = context.call_depth - 1;
+
+    // Because of callbacks, calls can be nested. Because of this, we
+    // can't clear the call_arena after _every_ call. Imagine we have
+    //    arr.forEach((i) => { console.log(i); }
+    //
+    // First we call forEach. Inside of our forEach call,
+    // we call console.log. If we reset the call_arena after this call,
+    // it'll reset it for the `forEach` call after, which might still
+    // need the data.
+    //
+    // Therefore, we keep a call_depth, and only reset the call_arena
+    // when a top-level (call_depth == 0) function ends.
+    if (call_depth == 0) {
+        const arena: *ArenaAllocator = @ptrCast(@alignCast(context.call_arena.ptr));
+        _ = arena.reset(.{ .retain_with_limit = CALL_ARENA_RETAIN });
+    }
+
+    // Set this _after_ we've executed the above code, so that if the
+    // above code executes any callbacks, they aren't being executed
+    // at scope 0, which would be wrong.
+    context.call_depth = call_depth;
+}
+
+pub fn constructor(self: *Caller, comptime Struct: type, comptime named_function: NamedFunction, info: v8.FunctionCallbackInfo) !void {
+    const args = try self.getArgs(Struct, named_function, 0, info);
+    const res = @call(.auto, Struct.constructor, args);
+
+    const ReturnType = @typeInfo(@TypeOf(Struct.constructor)).@"fn".return_type orelse {
+        @compileError(@typeName(Struct) ++ " has a constructor without a return type");
+    };
+
+    const this = info.getThis();
+    if (@typeInfo(ReturnType) == .error_union) {
+        const non_error_res = res catch |err| return err;
+        _ = try self.context.mapZigInstanceToJs(this, non_error_res);
+    } else {
+        _ = try self.context.mapZigInstanceToJs(this, res);
+    }
+    info.getReturnValue().set(this);
+}
+
+pub fn method(self: *Caller, comptime Struct: type, comptime named_function: NamedFunction, info: v8.FunctionCallbackInfo) !void {
+    if (comptime isSelfReceiver(Struct, named_function) == false) {
+        return self.function(Struct, named_function, info);
+    }
+
+    const context = self.context;
+    const func = @field(Struct, named_function.name);
+    var args = try self.getArgs(Struct, named_function, 1, info);
+    const zig_instance = try context.typeTaggedAnyOpaque(named_function, *types.Receiver(Struct), info.getThis());
+
+    // inject 'self' as the first parameter
+    @field(args, "0") = zig_instance;
+
+    const res = @call(.auto, func, args);
+    info.getReturnValue().set(try context.zigValueToJs(res));
+}
+
+pub fn function(self: *Caller, comptime Struct: type, comptime named_function: NamedFunction, info: v8.FunctionCallbackInfo) !void {
+    const context = self.context;
+    const func = @field(Struct, named_function.name);
+    const args = try self.getArgs(Struct, named_function, 0, info);
+    const res = @call(.auto, func, args);
+    info.getReturnValue().set(try context.zigValueToJs(res));
+}
+
+pub fn getIndex(self: *Caller, comptime Struct: type, comptime named_function: NamedFunction, idx: u32, info: v8.PropertyCallbackInfo) !u8 {
+    const context = self.context;
+    const func = @field(Struct, named_function.name);
+    const IndexedGet = @TypeOf(func);
+    if (@typeInfo(IndexedGet).@"fn".return_type == null) {
+        @compileError(named_function.full_name ++ " must have a return type");
+    }
+
+    var has_value = true;
+
+    var args: ParamterTypes(IndexedGet) = undefined;
+    const arg_fields = @typeInfo(@TypeOf(args)).@"struct".fields;
+    switch (arg_fields.len) {
+        0, 1, 2 => @compileError(named_function.full_name ++ " must take at least a u32 and *bool parameter"),
+        3, 4 => {
+            const zig_instance = try context.typeTaggedAnyOpaque(named_function, *types.Receiver(Struct), info.getThis());
+            comptime assertSelfReceiver(Struct, named_function);
+            @field(args, "0") = zig_instance;
+            @field(args, "1") = idx;
+            @field(args, "2") = &has_value;
+            if (comptime arg_fields.len == 4) {
+                comptime assertIsPageArg(Struct, named_function, 3);
+                @field(args, "3") = context.page;
+            }
+        },
+        else => @compileError(named_function.full_name ++ " has too many parmaters"),
+    }
+
+    const res = @call(.auto, func, args);
+    if (has_value == false) {
+        return v8.Intercepted.No;
+    }
+    info.getReturnValue().set(try context.zigValueToJs(res));
+    return v8.Intercepted.Yes;
+}
+
+pub fn getNamedIndex(self: *Caller, comptime Struct: type, comptime named_function: NamedFunction, name: v8.Name, info: v8.PropertyCallbackInfo) !u8 {
+    const context = self.context;
+    const func = @field(Struct, named_function.name);
+    comptime assertSelfReceiver(Struct, named_function);
+
+    var has_value = true;
+    var args = try self.getArgs(Struct, named_function, 3, info);
+    const zig_instance = try context.typeTaggedAnyOpaque(named_function, *types.Receiver(Struct), info.getThis());
+    @field(args, "0") = zig_instance;
+    @field(args, "1") = try self.nameToString(name);
+    @field(args, "2") = &has_value;
+
+    const res = @call(.auto, func, args);
+    if (has_value == false) {
+        return v8.Intercepted.No;
+    }
+    info.getReturnValue().set(try self.context.zigValueToJs(res));
+    return v8.Intercepted.Yes;
+}
+
+pub fn setNamedIndex(self: *Caller, comptime Struct: type, comptime named_function: NamedFunction, name: v8.Name, js_value: v8.Value, info: v8.PropertyCallbackInfo) !u8 {
+    const context = self.context;
+    const func = @field(Struct, named_function.name);
+    comptime assertSelfReceiver(Struct, named_function);
+
+    var has_value = true;
+    var args = try self.getArgs(Struct, named_function, 4, info);
+    const zig_instance = try context.typeTaggedAnyOpaque(named_function, *types.Receiver(Struct), info.getThis());
+    @field(args, "0") = zig_instance;
+    @field(args, "1") = try self.nameToString(name);
+    @field(args, "2") = try context.jsValueToZig(named_function, @TypeOf(@field(args, "2")), js_value);
+    @field(args, "3") = &has_value;
+
+    const res = @call(.auto, func, args);
+    return namedSetOrDeleteCall(res, has_value);
+}
+
+pub fn deleteNamedIndex(self: *Caller, comptime Struct: type, comptime named_function: NamedFunction, name: v8.Name, info: v8.PropertyCallbackInfo) !u8 {
+    const context = self.context;
+    const func = @field(Struct, named_function.name);
+    comptime assertSelfReceiver(Struct, named_function);
+
+    var has_value = true;
+    var args = try self.getArgs(Struct, named_function, 3, info);
+    const zig_instance = try context.typeTaggedAnyOpaque(named_function, *types.Receiver(Struct), info.getThis());
+    @field(args, "0") = zig_instance;
+    @field(args, "1") = try self.nameToString(name);
+    @field(args, "2") = &has_value;
+
+    const res = @call(.auto, func, args);
+    return namedSetOrDeleteCall(res, has_value);
+}
+
+fn namedSetOrDeleteCall(res: anytype, has_value: bool) !u8 {
+    if (@typeInfo(@TypeOf(res)) == .error_union) {
+        _ = try res;
+    }
+    if (has_value == false) {
+        return v8.Intercepted.No;
+    }
+    return v8.Intercepted.Yes;
+}
+
+fn nameToString(self: *Caller, name: v8.Name) ![]const u8 {
+    return self.context.valueToString(.{ .handle = name.handle }, .{});
+}
+
+fn isSelfReceiver(comptime Struct: type, comptime named_function: NamedFunction) bool {
+    return checkSelfReceiver(Struct, named_function, false);
+}
+fn assertSelfReceiver(comptime Struct: type, comptime named_function: NamedFunction) void {
+    _ = checkSelfReceiver(Struct, named_function, true);
+}
+fn checkSelfReceiver(comptime Struct: type, comptime named_function: NamedFunction, comptime fail: bool) bool {
+    const func = @field(Struct, named_function.name);
+    const params = @typeInfo(@TypeOf(func)).@"fn".params;
+    if (params.len == 0) {
+        if (fail) {
+            @compileError(named_function.full_name ++ " must have a self parameter");
+        }
+        return false;
+    }
+
+    const R = types.Receiver(Struct);
+    const first_param = params[0].type.?;
+    if (first_param != *R and first_param != *const R) {
+        if (fail) {
+            @compileError(std.fmt.comptimePrint("The first parameter to {s} must be a *{s} or *const {s}. Got: {s}", .{
+                named_function.full_name,
+                @typeName(R),
+                @typeName(R),
+                @typeName(first_param),
+            }));
+        }
+        return false;
+    }
+    return true;
+}
+
+fn assertIsPageArg(comptime Struct: type, comptime named_function: NamedFunction, index: comptime_int) void {
+    const F = @TypeOf(@field(Struct, named_function.name));
+    const param = @typeInfo(F).@"fn".params[index].type.?;
+    if (isPage(param)) {
+        return;
+    }
+    @compileError(std.fmt.comptimePrint("The {d} parameter to {s} must be a *Page or *const Page. Got: {s}", .{ index, named_function.full_name, @typeName(param) }));
+}
+
+pub fn handleError(self: *Caller, comptime Struct: type, comptime named_function: NamedFunction, err: anyerror, info: anytype) void {
+    const isolate = self.isolate;
+
+    if (comptime @import("builtin").mode == .Debug and @hasDecl(@TypeOf(info), "length")) {
+        if (log.enabled(.js, .warn)) {
+            self.logFunctionCallError(err, named_function.full_name, info);
+        }
+    }
+
+    var js_err: ?v8.Value = switch (err) {
+        error.InvalidArgument => createTypeException(isolate, "invalid argument"),
+        error.OutOfMemory => js._createException(isolate, "out of memory"),
+        error.IllegalConstructor => js._createException(isolate, "Illegal Contructor"),
+        else => blk: {
+            const func = @field(Struct, named_function.name);
+            const return_type = @typeInfo(@TypeOf(func)).@"fn".return_type orelse {
+                // void return type;
+                break :blk null;
+            };
+
+            if (@typeInfo(return_type) != .error_union) {
+                // type defines a custom exception, but this function should
+                // not fail. We failed somewhere inside of js.zig and
+                // should return the error as-is, since it isn't related
+                // to our Struct
+                break :blk null;
+            }
+
+            const function_error_set = @typeInfo(return_type).error_union.error_set;
+
+            const E = comptime getCustomException(Struct) orelse break :blk null;
+            if (function_error_set == E or isErrorSetException(E, err)) {
+                const custom_exception = E.init(self.call_arena, err, named_function.js_name) catch |init_err| {
+                    switch (init_err) {
+                        // if a custom exceptions' init wants to return a
+                        // different error, we need to think about how to
+                        // handle that failure.
+                        error.OutOfMemory => break :blk js._createException(isolate, "out of memory"),
+                    }
+                };
+                // ughh..how to handle an error here?
+                break :blk self.context.zigValueToJs(custom_exception) catch js._createException(isolate, "internal error");
+            }
+            // this error isn't part of a custom exception
+            break :blk null;
+        },
+    };
+
+    if (js_err == null) {
+        js_err = js._createException(isolate, @errorName(err));
+    }
+    const js_exception = isolate.throwException(js_err.?);
+    info.getReturnValue().setValueHandle(js_exception.handle);
+}
+
+// walk the prototype chain to see if a type declares a custom Exception
+fn getCustomException(comptime Struct: type) ?type {
+    var S = Struct;
+    while (true) {
+        if (@hasDecl(S, "Exception")) {
+            return S.Exception;
+        }
+        if (@hasDecl(S, "prototype") == false) {
+            return null;
+        }
+        // long ago, we validated that every prototype declaration
+        // is a pointer.
+        S = @typeInfo(S.prototype).pointer.child;
+    }
+}
+
+// Does the error we want to return belong to the custom exeception's ErrorSet
+fn isErrorSetException(comptime E: type, err: anytype) bool {
+    const Entry = std.meta.Tuple(&.{ []const u8, void });
+
+    const error_set = @typeInfo(E.ErrorSet).error_set.?;
+    const entries = comptime blk: {
+        var kv: [error_set.len]Entry = undefined;
+        for (error_set, 0..) |e, i| {
+            kv[i] = .{ e.name, {} };
+        }
+        break :blk kv;
+    };
+    const lookup = std.StaticStringMap(void).initComptime(entries);
+    return lookup.has(@errorName(err));
+}
+
+// If we call a method in javascript: cat.lives('nine');
+//
+// Then we'd expect a Zig function with 2 parameters: a self and the string.
+// In this case, offset == 1. Offset is always 1 for setters or methods.
+//
+// Offset is always 0 for constructors.
+//
+// For constructors, setters and methods, we can further increase offset + 1
+// if the first parameter is an instance of Page.
+//
+// Finally, if the JS function is called with _more_ parameters and
+// the last parameter in Zig is an array, we'll try to slurp the additional
+// parameters into the array.
+fn getArgs(self: *const Caller, comptime Struct: type, comptime named_function: NamedFunction, comptime offset: usize, info: anytype) !ParamterTypes(@TypeOf(@field(Struct, named_function.name))) {
+    const context = self.context;
+    const F = @TypeOf(@field(Struct, named_function.name));
+    var args: ParamterTypes(F) = undefined;
+
+    const params = @typeInfo(F).@"fn".params[offset..];
+    // Except for the constructor, the first parameter is always `self`
+    // This isn't something we'll bind from JS, so skip it.
+    const params_to_map = blk: {
+        if (params.len == 0) {
+            return args;
+        }
+
+        // If the last parameter is the Page, set it, and exclude it
+        // from our params slice, because we don't want to bind it to
+        // a JS argument
+        if (comptime isPage(params[params.len - 1].type.?)) {
+            @field(args, tupleFieldName(params.len - 1 + offset)) = self.context.page;
+            break :blk params[0 .. params.len - 1];
+        }
+
+        // If the last parameter is a special JsThis, set it, and exclude it
+        // from our params slice, because we don't want to bind it to
+        // a JS argument
+        if (comptime params[params.len - 1].type.? == js.This) {
+            @field(args, tupleFieldName(params.len - 1 + offset)) = .{ .obj = .{
+                .context = context,
+                .js_obj = info.getThis(),
+            } };
+
+            // AND the 2nd last parameter is state
+            if (params.len > 1 and comptime isPage(params[params.len - 2].type.?)) {
+                @field(args, tupleFieldName(params.len - 2 + offset)) = self.context.page;
+                break :blk params[0 .. params.len - 2];
+            }
+
+            break :blk params[0 .. params.len - 1];
+        }
+
+        // we have neither a Page nor a JsObject. All params must be
+        // bound to a JavaScript value.
+        break :blk params;
+    };
+
+    if (params_to_map.len == 0) {
+        return args;
+    }
+
+    const js_parameter_count = info.length();
+    const last_js_parameter = params_to_map.len - 1;
+    var is_variadic = false;
+
+    {
+        // This is going to get complicated. If the last Zig parameter
+        // is a slice AND the corresponding javascript parameter is
+        // NOT an an array, then we'll treat it as a variadic.
+
+        const last_parameter_type = params_to_map[params_to_map.len - 1].type.?;
+        const last_parameter_type_info = @typeInfo(last_parameter_type);
+        if (last_parameter_type_info == .pointer and last_parameter_type_info.pointer.size == .slice) {
+            const slice_type = last_parameter_type_info.pointer.child;
+            const corresponding_js_value = info.getArg(@as(u32, @intCast(last_js_parameter)));
+            if (corresponding_js_value.isArray() == false and corresponding_js_value.isTypedArray() == false and slice_type != u8) {
+                is_variadic = true;
+                if (js_parameter_count == 0) {
+                    @field(args, tupleFieldName(params_to_map.len + offset - 1)) = &.{};
+                } else if (js_parameter_count >= params_to_map.len) {
+                    const arr = try self.call_arena.alloc(last_parameter_type_info.pointer.child, js_parameter_count - params_to_map.len + 1);
+                    for (arr, last_js_parameter..) |*a, i| {
+                        const js_value = info.getArg(@as(u32, @intCast(i)));
+                        a.* = try context.jsValueToZig(named_function, slice_type, js_value);
+                    }
+                    @field(args, tupleFieldName(params_to_map.len + offset - 1)) = arr;
+                } else {
+                    @field(args, tupleFieldName(params_to_map.len + offset - 1)) = &.{};
+                }
+            }
+        }
+    }
+
+    inline for (params_to_map, 0..) |param, i| {
+        const field_index = comptime i + offset;
+        if (comptime i == params_to_map.len - 1) {
+            if (is_variadic) {
+                break;
+            }
+        }
+
+        if (comptime isPage(param.type.?)) {
+            @compileError("Page must be the last parameter (or 2nd last if there's a JsThis): " ++ named_function.full_name);
+        } else if (comptime param.type.? == js.This) {
+            @compileError("JsThis must be the last parameter: " ++ named_function.full_name);
+        } else if (i >= js_parameter_count) {
+            if (@typeInfo(param.type.?) != .optional) {
+                return error.InvalidArgument;
+            }
+            @field(args, tupleFieldName(field_index)) = null;
+        } else {
+            const js_value = info.getArg(@as(u32, @intCast(i)));
+            @field(args, tupleFieldName(field_index)) = context.jsValueToZig(named_function, param.type.?, js_value) catch {
+                return error.InvalidArgument;
+            };
+        }
+    }
+
+    return args;
+}
+
+// This is extracted to speed up compilation. When left inlined in handleError,
+// this can add as much as 10 seconds of compilation time.
+fn logFunctionCallError(self: *Caller, err: anyerror, function_name: []const u8, info: v8.FunctionCallbackInfo) void {
+    const args_dump = self.serializeFunctionArgs(info) catch "failed to serialize args";
+    log.info(.js, "function call error", .{
+        .name = function_name,
+        .err = err,
+        .args = args_dump,
+        .stack = self.context.stackTrace() catch |err1| @errorName(err1),
+    });
+}
+
+fn serializeFunctionArgs(self: *Caller, info: v8.FunctionCallbackInfo) ![]const u8 {
+    const separator = log.separator();
+    const js_parameter_count = info.length();
+
+    const context = self.context;
+    var arr: std.ArrayListUnmanaged(u8) = .{};
+    for (0..js_parameter_count) |i| {
+        const js_value = info.getArg(@intCast(i));
+        const value_string = try context.valueToDetailString(js_value);
+        const value_type = try context.jsStringToZig(try js_value.typeOf(self.isolate), .{});
+        try std.fmt.format(arr.writer(context.call_arena), "{s}{d}: {s} ({s})", .{
+            separator,
+            i + 1,
+            value_string,
+            value_type,
+        });
+    }
+    return arr.items;
+}
+
+// We want the function name, or more precisely, the "Struct.function" for
+// displaying helpful @compileError.
+// However, there's no way to get the name from a std.Builtin.Fn, so we create
+// a NamedFunction as part of our binding, and pass it around incase we need
+// to display an error
+pub const NamedFunction = struct {
+    name: []const u8,
+    js_name: []const u8,
+    full_name: []const u8,
+
+    pub fn init(comptime Struct: type, comptime name: []const u8) NamedFunction {
+        return .{
+            .name = name,
+            .js_name = if (name[0] == '_') name[1..] else name,
+            .full_name = @typeName(Struct) ++ "." ++ name,
+        };
+    }
+};
+
+// Takes a function, and returns a tuple for its argument. Used when we
+// @call a function
+fn ParamterTypes(comptime F: type) type {
+    const params = @typeInfo(F).@"fn".params;
+    var fields: [params.len]std.builtin.Type.StructField = undefined;
+
+    inline for (params, 0..) |param, i| {
+        fields[i] = .{
+            .name = tupleFieldName(i),
+            .type = param.type.?,
+            .default_value_ptr = null,
+            .is_comptime = false,
+            .alignment = @alignOf(param.type.?),
+        };
+    }
+
+    return @Type(.{ .@"struct" = .{
+        .layout = .auto,
+        .decls = &.{},
+        .fields = &fields,
+        .is_tuple = true,
+    } });
+}
+
+fn tupleFieldName(comptime i: usize) [:0]const u8 {
+    return switch (i) {
+        0 => "0",
+        1 => "1",
+        2 => "2",
+        3 => "3",
+        4 => "4",
+        5 => "5",
+        6 => "6",
+        7 => "7",
+        8 => "8",
+        9 => "9",
+        else => std.fmt.comptimePrint("{d}", .{i}),
+    };
+}
+
+fn isPage(comptime T: type) bool {
+    return T == *Page or T == *const Page;
+}
+
+fn createTypeException(isolate: v8.Isolate, msg: []const u8) v8.Value {
+    return v8.Exception.initTypeError(v8.String.initUtf8(isolate, msg));
+}

src/browser/js/Env.zig

@@ -0,0 +1,537 @@
+const std = @import("std");
+const js = @import("js.zig");
+const v8 = js.v8;
+
+const log = @import("../../log.zig");
+
+const types = @import("types.zig");
+const Types = types.Types;
+const Caller = @import("Caller.zig");
+const Context = @import("Context.zig");
+const Platform = @import("Platform.zig");
+const Inspector = @import("Inspector.zig");
+const ExecutionWorld = @import("ExecutionWorld.zig");
+const NamedFunction = Caller.NamedFunction;
+
+const Allocator = std.mem.Allocator;
+const ArenaAllocator = std.heap.ArenaAllocator;
+
+// The Env maps to a V8 isolate, which represents a isolated sandbox for
+// executing JavaScript. The Env is where we'll define our V8 <-> Zig bindings,
+// and it's where we'll start ExecutionWorlds, which actually execute JavaScript.
+// The `S` parameter is arbitrary state. When we start an ExecutionWorld, an instance
+// of S must be given. This instance is available to any Zig binding.
+// The `types` parameter is a tuple of Zig structures we want to bind to V8.
+const Env = @This();
+
+allocator: Allocator,
+
+platform: *const Platform,
+
+// the global isolate
+isolate: v8.Isolate,
+
+// just kept around because we need to free it on deinit
+isolate_params: *v8.CreateParams,
+
+// Given a type, we can lookup its index in TYPE_LOOKUP and then have
+// access to its TunctionTemplate (the thing we need to create an instance
+// of it)
+// I.e.:
+// const index = @field(TYPE_LOOKUP, @typeName(type_name))
+// const template = templates[index];
+templates: [Types.len]v8.FunctionTemplate,
+
+// Given a type index (retrieved via the TYPE_LOOKUP), we can retrieve
+// the index of its prototype. Types without a prototype have their own
+// index.
+prototype_lookup: [Types.len]u16,
+
+meta_lookup: [Types.len]types.Meta,
+
+context_id: usize,
+
+const Opts = struct {};
+
+pub fn init(allocator: Allocator, platform: *const Platform, _: Opts) !*Env {
+    // var params = v8.initCreateParams();
+    var params = try allocator.create(v8.CreateParams);
+    errdefer allocator.destroy(params);
+
+    v8.c.v8__Isolate__CreateParams__CONSTRUCT(params);
+
+    params.array_buffer_allocator = v8.createDefaultArrayBufferAllocator();
+    errdefer v8.destroyArrayBufferAllocator(params.array_buffer_allocator.?);
+
+    var isolate = v8.Isolate.init(params);
+    errdefer isolate.deinit();
+
+    // This is the callback that runs whenever a module is dynamically imported.
+    isolate.setHostImportModuleDynamicallyCallback(Context.dynamicModuleCallback);
+    isolate.setPromiseRejectCallback(promiseRejectCallback);
+    isolate.setMicrotasksPolicy(v8.c.kExplicit);
+
+    isolate.enter();
+    errdefer isolate.exit();
+
+    isolate.setHostInitializeImportMetaObjectCallback(Context.metaObjectCallback);
+
+    var temp_scope: v8.HandleScope = undefined;
+    v8.HandleScope.init(&temp_scope, isolate);
+    defer temp_scope.deinit();
+
+    const env = try allocator.create(Env);
+    errdefer allocator.destroy(env);
+
+    env.* = .{
+        .context_id = 0,
+        .platform = platform,
+        .isolate = isolate,
+        .templates = undefined,
+        .allocator = allocator,
+        .isolate_params = params,
+        .meta_lookup = undefined,
+        .prototype_lookup = undefined,
+    };
+
+    // Populate our templates lookup. generateClass creates the
+    // v8.FunctionTemplate, which we store in our env.templates.
+    // The ordering doesn't matter. What matters is that, given a type
+    // we can get its index via: @field(types.LOOKUP, type_name)
+    const templates = &env.templates;
+    inline for (Types, 0..) |s, i| {
+        @setEvalBranchQuota(10_000);
+        templates[i] = v8.Persistent(v8.FunctionTemplate).init(isolate, generateClass(s.defaultValue().?, isolate)).castToFunctionTemplate();
+    }
+
+    // Above, we've created all our our FunctionTemplates. Now that we
+    // have them all, we can hook up the prototypes.
+    const meta_lookup = &env.meta_lookup;
+    inline for (Types, 0..) |s, i| {
+        const Struct = s.defaultValue().?;
+        if (@hasDecl(Struct, "prototype")) {
+            const TI = @typeInfo(Struct.prototype);
+            const ProtoType = types.Receiver(TI.pointer.child);
+            if (!types.has(ProtoType)) {
+                @compileError(std.fmt.comptimePrint("Prototype '{s}' for '{s}' is undefined", .{ @typeName(ProtoType), @typeName(Struct) }));
+            }
+            // Hey, look! This is our first real usage of the `types.Index`.
+            // Just like we said above, given a type, we can get its
+            // template index.
+            templates[i].inherit(templates[types.getId(ProtoType)]);
+        }
+
+        // while we're here, let's populate our meta lookup
+        const subtype: ?types.Sub = if (@hasDecl(Struct, "subtype")) Struct.subtype else null;
+
+        const proto_offset = comptime blk: {
+            if (!@hasField(Struct, "proto")) {
+                break :blk 0;
+            }
+            const proto_info = std.meta.fieldInfo(Struct, .proto);
+            if (@typeInfo(proto_info.type) == .pointer) {
+                // we store the offset as a negative, to so that,
+                // when we reverse this, we know that it's
+                // behind a pointer that we need to resolve.
+                break :blk -@offsetOf(Struct, "proto");
+            }
+            break :blk @offsetOf(Struct, "proto");
+        };
+
+        meta_lookup[i] = .{
+            .index = i,
+            .subtype = subtype,
+            .proto_offset = proto_offset,
+        };
+    }
+
+    return env;
+}
+
+pub fn deinit(self: *Env) void {
+    self.isolate.exit();
+    self.isolate.deinit();
+    v8.destroyArrayBufferAllocator(self.isolate_params.array_buffer_allocator.?);
+    self.allocator.destroy(self.isolate_params);
+    self.allocator.destroy(self);
+}
+
+pub fn newInspector(self: *Env, arena: Allocator, ctx: anytype) !Inspector {
+    return Inspector.init(arena, self.isolate, ctx);
+}
+
+pub fn runMicrotasks(self: *const Env) void {
+    self.isolate.performMicrotasksCheckpoint();
+}
+
+pub fn pumpMessageLoop(self: *const Env) bool {
+    return self.platform.inner.pumpMessageLoop(self.isolate, false);
+}
+
+pub fn runIdleTasks(self: *const Env) void {
+    return self.platform.inner.runIdleTasks(self.isolate, 1);
+}
+
+pub fn newExecutionWorld(self: *Env) !ExecutionWorld {
+    return .{
+        .env = self,
+        .context = null,
+        .context_arena = ArenaAllocator.init(self.allocator),
+    };
+}
+
+// V8 doesn't immediately free memory associated with
+// a Context, it's managed by the garbage collector. We use the
+// `lowMemoryNotification` call on the isolate to encourage v8 to free
+// any contexts which have been freed.
+pub fn lowMemoryNotification(self: *Env) void {
+    var handle_scope: v8.HandleScope = undefined;
+    v8.HandleScope.init(&handle_scope, self.isolate);
+    defer handle_scope.deinit();
+    self.isolate.lowMemoryNotification();
+}
+
+pub fn dumpMemoryStats(self: *Env) void {
+    const stats = self.isolate.getHeapStatistics();
+    std.debug.print(
+        \\ Total Heap Size: {d}
+        \\ Total Heap Size Executable: {d}
+        \\ Total Physical Size: {d}
+        \\ Total Available Size: {d}
+        \\ Used Heap Size: {d}
+        \\ Heap Size Limit: {d}
+        \\ Malloced Memory: {d}
+        \\ External Memory: {d}
+        \\ Peak Malloced Memory: {d}
+        \\ Number Of Native Contexts: {d}
+        \\ Number Of Detached Contexts: {d}
+        \\ Total Global Handles Size: {d}
+        \\ Used Global Handles Size: {d}
+        \\ Zap Garbage: {any}
+        \\
+    , .{ stats.total_heap_size, stats.total_heap_size_executable, stats.total_physical_size, stats.total_available_size, stats.used_heap_size, stats.heap_size_limit, stats.malloced_memory, stats.external_memory, stats.peak_malloced_memory, stats.number_of_native_contexts, stats.number_of_detached_contexts, stats.total_global_handles_size, stats.used_global_handles_size, stats.does_zap_garbage });
+}
+
+fn promiseRejectCallback(v8_msg: v8.C_PromiseRejectMessage) callconv(.c) void {
+    const msg = v8.PromiseRejectMessage.initFromC(v8_msg);
+    const isolate = msg.getPromise().toObject().getIsolate();
+    const context = Context.fromIsolate(isolate);
+
+    const value =
+        if (msg.getValue()) |v8_value| context.valueToString(v8_value, .{}) catch |err| @errorName(err) else "no value";
+
+    log.debug(.js, "unhandled rejection", .{ .value = value });
+}
+
+// Give it a Zig struct, get back a v8.FunctionTemplate.
+// The FunctionTemplate is a bit like a struct container - it's where
+// we'll attach functions/getters/setters and where we'll "inherit" a
+// prototype type (if there is any)
+fn generateClass(comptime Struct: type, isolate: v8.Isolate) v8.FunctionTemplate {
+    const template = generateConstructor(Struct, isolate);
+    attachClass(Struct, isolate, template);
+    return template;
+}
+
+// Normally this is called from generateClass. Where generateClass creates
+// the constructor (hence, the FunctionTemplate), attachClass adds all
+// of its functions, getters, setters, ...
+// But it's extracted from generateClass because we also have 1 global
+// object (i.e. the Window), which gets attached not only to the Window
+// constructor/FunctionTemplate as normal, but also through the default
+// FunctionTemplate of the isolate (in createContext)
+pub fn attachClass(comptime Struct: type, isolate: v8.Isolate, template: v8.FunctionTemplate) void {
+    const template_proto = template.getPrototypeTemplate();
+    inline for (@typeInfo(Struct).@"struct".decls) |declaration| {
+        const name = declaration.name;
+        if (comptime name[0] == '_') {
+            switch (@typeInfo(@TypeOf(@field(Struct, name)))) {
+                .@"fn" => generateMethod(Struct, name, isolate, template_proto),
+                else => |ti| if (!comptime js.isComplexAttributeType(ti)) {
+                    generateAttribute(Struct, name, isolate, template, template_proto);
+                },
+            }
+        } else if (comptime std.mem.startsWith(u8, name, "get_")) {
+            generateProperty(Struct, name[4..], isolate, template_proto);
+        } else if (comptime std.mem.startsWith(u8, name, "static_")) {
+            generateFunction(Struct, name[7..], isolate, template);
+        }
+    }
+
+    if (@hasDecl(Struct, "get_symbol_toStringTag") == false) {
+        // If this WAS defined, then we would have created it in generateProperty.
+        // But if it isn't, we create a default one
+        const string_tag_callback = v8.FunctionTemplate.initCallback(isolate, struct {
+            fn stringTag(raw_info: ?*const v8.C_FunctionCallbackInfo) callconv(.c) void {
+                const info = v8.FunctionCallbackInfo.initFromV8(raw_info);
+                const class_name = v8.String.initUtf8(info.getIsolate(), comptime js.classNameForStruct(Struct));
+                info.getReturnValue().set(class_name);
+            }
+        }.stringTag);
+        const key = v8.Symbol.getToStringTag(isolate).toName();
+        template_proto.setAccessorGetter(key, string_tag_callback);
+    }
+
+    generateIndexer(Struct, template_proto);
+    generateNamedIndexer(Struct, template.getInstanceTemplate());
+    generateUndetectable(Struct, template.getInstanceTemplate());
+}
+
+// Even if a struct doesn't have a `constructor` function, we still
+// `generateConstructor`, because this is how we create our
+// FunctionTemplate. Such classes exist, but they can't be instantiated
+// via `new ClassName()` - but they could, for example, be created in
+// Zig and returned from a function call, which is why we need the
+// FunctionTemplate.
+fn generateConstructor(comptime Struct: type, isolate: v8.Isolate) v8.FunctionTemplate {
+    const template = v8.FunctionTemplate.initCallback(isolate, struct {
+        fn callback(raw_info: ?*const v8.C_FunctionCallbackInfo) callconv(.c) void {
+            const info = v8.FunctionCallbackInfo.initFromV8(raw_info);
+            var caller = Caller.init(info);
+            defer caller.deinit();
+            // See comment above. We generateConstructor on all types
+            // in order to create the FunctionTemplate, but there might
+            // not be an actual "constructor" function. So if someone
+            // does `new ClassName()` where ClassName doesn't have
+            // a constructor function, we'll return an error.
+            if (@hasDecl(Struct, "constructor") == false) {
+                const iso = caller.isolate;
+                log.warn(.js, "Illegal constructor call", .{ .name = @typeName(Struct) });
+                const js_exception = iso.throwException(js._createException(iso, "Illegal Constructor"));
+                info.getReturnValue().set(js_exception);
+                return;
+            }
+
+            // Safe to call now, because if Struct.constructor didn't
+            // exist, the above if block would have returned.
+            const named_function = comptime NamedFunction.init(Struct, "constructor");
+            caller.constructor(Struct, named_function, info) catch |err| {
+                caller.handleError(Struct, named_function, err, info);
+            };
+        }
+    }.callback);
+
+    if (comptime types.isEmpty(types.Receiver(Struct)) == false) {
+        // If the struct is empty, we won't store a Zig reference inside
+        // the JS object, so we don't need to set the internal field count
+        template.getInstanceTemplate().setInternalFieldCount(1);
+    }
+
+    const class_name = v8.String.initUtf8(isolate, comptime js.classNameForStruct(Struct));
+    template.setClassName(class_name);
+    return template;
+}
+
+fn generateMethod(comptime Struct: type, comptime name: []const u8, isolate: v8.Isolate, template_proto: v8.ObjectTemplate) void {
+    var js_name: v8.Name = undefined;
+    if (comptime std.mem.eql(u8, name, "_symbol_iterator")) {
+        js_name = v8.Symbol.getIterator(isolate).toName();
+    } else {
+        js_name = v8.String.initUtf8(isolate, name[1..]).toName();
+    }
+    const function_template = v8.FunctionTemplate.initCallback(isolate, struct {
+        fn callback(raw_info: ?*const v8.C_FunctionCallbackInfo) callconv(.c) void {
+            const info = v8.FunctionCallbackInfo.initFromV8(raw_info);
+            var caller = Caller.init(info);
+            defer caller.deinit();
+
+            const named_function = comptime NamedFunction.init(Struct, name);
+            caller.method(Struct, named_function, info) catch |err| {
+                caller.handleError(Struct, named_function, err, info);
+            };
+        }
+    }.callback);
+    template_proto.set(js_name, function_template, v8.PropertyAttribute.None);
+}
+
+fn generateFunction(comptime Struct: type, comptime name: []const u8, isolate: v8.Isolate, template: v8.FunctionTemplate) void {
+    const js_name = v8.String.initUtf8(isolate, name).toName();
+    const function_template = v8.FunctionTemplate.initCallback(isolate, struct {
+        fn callback(raw_info: ?*const v8.C_FunctionCallbackInfo) callconv(.c) void {
+            const info = v8.FunctionCallbackInfo.initFromV8(raw_info);
+            var caller = Caller.init(info);
+            defer caller.deinit();
+
+            const named_function = comptime NamedFunction.init(Struct, "static_" ++ name);
+            caller.function(Struct, named_function, info) catch |err| {
+                caller.handleError(Struct, named_function, err, info);
+            };
+        }
+    }.callback);
+    template.set(js_name, function_template, v8.PropertyAttribute.None);
+}
+
+fn generateAttribute(comptime Struct: type, comptime name: []const u8, isolate: v8.Isolate, template: v8.FunctionTemplate, template_proto: v8.ObjectTemplate) void {
+    const zig_value = @field(Struct, name);
+    const js_value = js.simpleZigValueToJs(isolate, zig_value, true);
+
+    const js_name = v8.String.initUtf8(isolate, name[1..]).toName();
+
+    // apply it both to the type itself
+    template.set(js_name, js_value, v8.PropertyAttribute.ReadOnly + v8.PropertyAttribute.DontDelete);
+
+    // and to instances of the type
+    template_proto.set(js_name, js_value, v8.PropertyAttribute.ReadOnly + v8.PropertyAttribute.DontDelete);
+}
+
+fn generateProperty(comptime Struct: type, comptime name: []const u8, isolate: v8.Isolate, template_proto: v8.ObjectTemplate) void {
+    var js_name: v8.Name = undefined;
+    if (comptime std.mem.eql(u8, name, "symbol_toStringTag")) {
+        js_name = v8.Symbol.getToStringTag(isolate).toName();
+    } else {
+        js_name = v8.String.initUtf8(isolate, name).toName();
+    }
+
+    const getter_callback = v8.FunctionTemplate.initCallback(isolate, struct {
+        fn callback(raw_info: ?*const v8.C_FunctionCallbackInfo) callconv(.c) void {
+            const info = v8.FunctionCallbackInfo.initFromV8(raw_info);
+            var caller = Caller.init(info);
+            defer caller.deinit();
+
+            const named_function = comptime NamedFunction.init(Struct, "get_" ++ name);
+            caller.method(Struct, named_function, info) catch |err| {
+                caller.handleError(Struct, named_function, err, info);
+            };
+        }
+    }.callback);
+
+    const setter_name = "set_" ++ name;
+    if (@hasDecl(Struct, setter_name) == false) {
+        template_proto.setAccessorGetter(js_name, getter_callback);
+        return;
+    }
+
+    const setter_callback = v8.FunctionTemplate.initCallback(isolate, struct {
+        fn callback(raw_info: ?*const v8.C_FunctionCallbackInfo) callconv(.c) void {
+            const info = v8.FunctionCallbackInfo.initFromV8(raw_info);
+            std.debug.assert(info.length() == 1);
+
+            var caller = Caller.init(info);
+            defer caller.deinit();
+
+            const named_function = comptime NamedFunction.init(Struct, "set_" ++ name);
+            caller.method(Struct, named_function, info) catch |err| {
+                caller.handleError(Struct, named_function, err, info);
+            };
+        }
+    }.callback);
+
+    template_proto.setAccessorGetterAndSetter(js_name, getter_callback, setter_callback);
+}
+
+fn generateIndexer(comptime Struct: type, template_proto: v8.ObjectTemplate) void {
+    if (@hasDecl(Struct, "indexed_get") == false) {
+        return;
+    }
+    const configuration = v8.IndexedPropertyHandlerConfiguration{
+        .getter = struct {
+            fn callback(idx: u32, raw_info: ?*const v8.C_PropertyCallbackInfo) callconv(.c) u8 {
+                const info = v8.PropertyCallbackInfo.initFromV8(raw_info);
+                var caller = Caller.init(info);
+                defer caller.deinit();
+
+                const named_function = comptime NamedFunction.init(Struct, "indexed_get");
+                return caller.getIndex(Struct, named_function, idx, info) catch |err| blk: {
+                    caller.handleError(Struct, named_function, err, info);
+                    break :blk v8.Intercepted.No;
+                };
+            }
+        }.callback,
+    };
+
+    // If you're trying to implement setter, read:
+    // https://groups.google.com/g/v8-users/c/8tahYBsHpgY/m/IteS7Wn2AAAJ
+    // The issue I had was
+    // (a) where to attache it: does it go on the instance_template
+    //     instead of the prototype?
+    // (b) defining the getter or query to respond with the
+    //     PropertyAttribute to indicate if the property can be set
+    template_proto.setIndexedProperty(configuration, null);
+}
+
+fn generateNamedIndexer(comptime Struct: type, template_proto: v8.ObjectTemplate) void {
+    if (@hasDecl(Struct, "named_get") == false) {
+        return;
+    }
+
+    var configuration = v8.NamedPropertyHandlerConfiguration{
+        .getter = struct {
+            fn callback(c_name: ?*const v8.C_Name, raw_info: ?*const v8.C_PropertyCallbackInfo) callconv(.c) u8 {
+                const info = v8.PropertyCallbackInfo.initFromV8(raw_info);
+                var caller = Caller.init(info);
+                defer caller.deinit();
+
+                const named_function = comptime NamedFunction.init(Struct, "named_get");
+                return caller.getNamedIndex(Struct, named_function, .{ .handle = c_name.? }, info) catch |err| blk: {
+                    caller.handleError(Struct, named_function, err, info);
+                    break :blk v8.Intercepted.No;
+                };
+            }
+        }.callback,
+
+        // This is really cool. Without this, we'd intercept _all_ properties
+        // even those explicitly set. So, node.length for example would get routed
+        // to our `named_get`, rather than a `get_length`. This might be
+        // useful if we run into a type that we can't model properly in Zig.
+        .flags = v8.PropertyHandlerFlags.OnlyInterceptStrings | v8.PropertyHandlerFlags.NonMasking,
+    };
+
+    if (@hasDecl(Struct, "named_set")) {
+        configuration.setter = struct {
+            fn callback(c_name: ?*const v8.C_Name, c_value: ?*const v8.C_Value, raw_info: ?*const v8.C_PropertyCallbackInfo) callconv(.c) u8 {
+                const info = v8.PropertyCallbackInfo.initFromV8(raw_info);
+                var caller = Caller.init(info);
+                defer caller.deinit();
+
+                const named_function = comptime NamedFunction.init(Struct, "named_set");
+                return caller.setNamedIndex(Struct, named_function, .{ .handle = c_name.? }, .{ .handle = c_value.? }, info) catch |err| blk: {
+                    caller.handleError(Struct, named_function, err, info);
+                    break :blk v8.Intercepted.No;
+                };
+            }
+        }.callback;
+    }
+
+    if (@hasDecl(Struct, "named_delete")) {
+        configuration.deleter = struct {
+            fn callback(c_name: ?*const v8.C_Name, raw_info: ?*const v8.C_PropertyCallbackInfo) callconv(.c) u8 {
+                const info = v8.PropertyCallbackInfo.initFromV8(raw_info);
+                var caller = Caller.init(info);
+                defer caller.deinit();
+
+                const named_function = comptime NamedFunction.init(Struct, "named_delete");
+                return caller.deleteNamedIndex(Struct, named_function, .{ .handle = c_name.? }, info) catch |err| blk: {
+                    caller.handleError(Struct, named_function, err, info);
+                    break :blk v8.Intercepted.No;
+                };
+            }
+        }.callback;
+    }
+    template_proto.setNamedProperty(configuration, null);
+}
+
+fn generateUndetectable(comptime Struct: type, template: v8.ObjectTemplate) void {
+    const has_js_call_as_function = @hasDecl(Struct, "jsCallAsFunction");
+
+    if (has_js_call_as_function) {
+        template.setCallAsFunctionHandler(struct {
+            fn callback(raw_info: ?*const v8.C_FunctionCallbackInfo) callconv(.c) void {
+                const info = v8.FunctionCallbackInfo.initFromV8(raw_info);
+                var caller = Caller.init(info);
+                defer caller.deinit();
+
+                const named_function = comptime NamedFunction.init(Struct, "jsCallAsFunction");
+                caller.method(Struct, named_function, info) catch |err| {
+                    caller.handleError(Struct, named_function, err, info);
+                };
+            }
+        }.callback);
+    }
+
+    if (@hasDecl(Struct, "mark_as_undetectable") and Struct.mark_as_undetectable) {
+        if (!has_js_call_as_function) {
+            @compileError(@typeName(Struct) ++ ": mark_as_undetectable required jsCallAsFunction to be defined. This is a hard-coded requirement in V8, because mark_as_undetectable only exists for HTMLAllCollection which is also callable.");
+        }
+        template.markAsUndetectable();
+    }
+}

src/browser/js/ExecutionWorld.zig

@@ -0,0 +1,247 @@
+const std = @import("std");
+const js = @import("js.zig");
+const v8 = js.v8;
+
+const log = @import("../../log.zig");
+const Page = @import("../page.zig").Page;
+const ScriptManager = @import("../ScriptManager.zig");
+
+const types = @import("types.zig");
+const Types = types.Types;
+const Env = @import("Env.zig");
+const Context = @import("Context.zig");
+
+const ArenaAllocator = std.heap.ArenaAllocator;
+
+const CONTEXT_ARENA_RETAIN = 1024 * 64;
+
+// ExecutionWorld closely models a JS World.
+// https://chromium.googlesource.com/chromium/src/+/master/third_party/blink/renderer/bindings/core/v8/V8BindingDesign.md#World
+// https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/scripting/ExecutionWorld
+const ExecutionWorld = @This();
+env: *Env,
+
+// Arena whose lifetime is for a single page load. Where
+// the call_arena lives for a single function call, the context_arena
+// lives for the lifetime of the entire page. The allocator will be
+// owned by the Context, but the arena itself is owned by the ExecutionWorld
+// so that we can re-use it from context to context.
+context_arena: ArenaAllocator,
+
+// Currently a context maps to a Browser's Page. Here though, it's only a
+// mechanism to organization page-specific memory. The ExecutionWorld
+// does all the work, but having all page-specific data structures
+// grouped together helps keep things clean.
+context: ?Context = null,
+
+// no init, must be initialized via env.newExecutionWorld()
+
+pub fn deinit(self: *ExecutionWorld) void {
+    if (self.context != null) {
+        self.removeContext();
+    }
+
+    self.context_arena.deinit();
+}
+
+// Only the top Context in the Main ExecutionWorld should hold a handle_scope.
+// A v8.HandleScope is like an arena. Once created, any "Local" that
+// v8 creates will be released (or at least, releasable by the v8 GC)
+// when the handle_scope is freed.
+// We also maintain our own "context_arena" which allows us to have
+// all page related memory easily managed.
+pub fn createContext(self: *ExecutionWorld, page: *Page, enter: bool, global_callback: ?js.GlobalMissingCallback) !*Context {
+    std.debug.assert(self.context == null);
+
+    const env = self.env;
+    const isolate = env.isolate;
+    const Global = @TypeOf(page.window);
+    const templates = &self.env.templates;
+
+    var v8_context: v8.Context = blk: {
+        var temp_scope: v8.HandleScope = undefined;
+        v8.HandleScope.init(&temp_scope, isolate);
+        defer temp_scope.deinit();
+
+        const js_global = v8.FunctionTemplate.initDefault(isolate);
+        Env.attachClass(Global, isolate, js_global);
+
+        const global_template = js_global.getInstanceTemplate();
+        global_template.setInternalFieldCount(1);
+
+        // Configure the missing property callback on the global
+        // object.
+        if (global_callback != null) {
+            const configuration = v8.NamedPropertyHandlerConfiguration{
+                .getter = struct {
+                    fn callback(c_name: ?*const v8.C_Name, raw_info: ?*const v8.C_PropertyCallbackInfo) callconv(.c) u8 {
+                        const info = v8.PropertyCallbackInfo.initFromV8(raw_info);
+                        const context = Context.fromIsolate(info.getIsolate());
+
+                        const property = context.valueToString(.{ .handle = c_name.? }, .{}) catch "???";
+                        if (context.global_callback.?.missing(property, context)) {
+                            return v8.Intercepted.Yes;
+                        }
+                        return v8.Intercepted.No;
+                    }
+                }.callback,
+                .flags = v8.PropertyHandlerFlags.NonMasking | v8.PropertyHandlerFlags.OnlyInterceptStrings,
+            };
+            global_template.setNamedProperty(configuration, null);
+        }
+
+        // All the FunctionTemplates that we created and setup in Env.init
+        // are now going to get associated with our global instance.
+        inline for (Types, 0..) |s, i| {
+            const Struct = s.defaultValue().?;
+            const class_name = v8.String.initUtf8(isolate, comptime js.classNameForStruct(Struct));
+            global_template.set(class_name.toName(), templates[i], v8.PropertyAttribute.None);
+        }
+
+        // The global object (Window) has already been hooked into the v8
+        // engine when the Env was initialized - like every other type.
+        // But the V8 global is its own FunctionTemplate instance so even
+        // though it's also a Window, we need to set the prototype for this
+        // specific instance of the the Window.
+        if (@hasDecl(Global, "prototype")) {
+            const ProtoType = types.Receiver(@typeInfo(Global.prototype).pointer.child);
+            js_global.inherit(templates[types.getId(ProtoType)]);
+        }
+
+        const context_local = v8.Context.init(isolate, global_template, null);
+        const v8_context = v8.Persistent(v8.Context).init(isolate, context_local).castToContext();
+        v8_context.enter();
+        errdefer if (enter) v8_context.exit();
+        defer if (!enter) v8_context.exit();
+
+        // This shouldn't be necessary, but it is:
+        // https://groups.google.com/g/v8-users/c/qAQQBmbi--8
+        // TODO: see if newer V8 engines have a way around this.
+        inline for (Types, 0..) |s, i| {
+            const Struct = s.defaultValue().?;
+
+            if (@hasDecl(Struct, "prototype")) {
+                const ProtoType = types.Receiver(@typeInfo(Struct.prototype).pointer.child);
+                if (!types.has(ProtoType)) {
+                    @compileError("Type '" ++ @typeName(Struct) ++ "' defines an unknown prototype: " ++ @typeName(ProtoType));
+                }
+
+                const proto_obj = templates[types.getId(ProtoType)].getFunction(v8_context).toObject();
+
+                const self_obj = templates[i].getFunction(v8_context).toObject();
+                _ = self_obj.setPrototype(v8_context, proto_obj);
+            }
+        }
+        break :blk v8_context;
+    };
+
+    // For a Page we only create one HandleScope, it is stored in the main World (enter==true). A page can have multple contexts, 1 for each World.
+    // The main Context that enters and holds the HandleScope should therefore always be created first. Following other worlds for this page
+    // like isolated Worlds, will thereby place their objects on the main page's HandleScope. Note: In the furure the number of context will multiply multiple frames support
+    var handle_scope: ?v8.HandleScope = null;
+    if (enter) {
+        handle_scope = @as(v8.HandleScope, undefined);
+        v8.HandleScope.init(&handle_scope.?, isolate);
+    }
+    errdefer if (enter) handle_scope.?.deinit();
+
+    {
+        // If we want to overwrite the built-in console, we have to
+        // delete the built-in one.
+        const js_obj = v8_context.getGlobal();
+        const console_key = v8.String.initUtf8(isolate, "console");
+        if (js_obj.deleteValue(v8_context, console_key) == false) {
+            return error.ConsoleDeleteError;
+        }
+    }
+    const context_id = env.context_id;
+    env.context_id = context_id + 1;
+
+    self.context = Context{
+        .page = page,
+        .id = context_id,
+        .isolate = isolate,
+        .v8_context = v8_context,
+        .templates = &env.templates,
+        .meta_lookup = &env.meta_lookup,
+        .handle_scope = handle_scope,
+        .script_manager = &page.script_manager,
+        .call_arena = page.call_arena,
+        .arena = self.context_arena.allocator(),
+        .global_callback = global_callback,
+    };
+
+    var context = &self.context.?;
+    {
+        // Store a pointer to our context inside the v8 context so that, given
+        // a v8 context, we can get our context out
+        const data = isolate.initBigIntU64(@intCast(@intFromPtr(context)));
+        v8_context.setEmbedderData(1, data);
+    }
+
+    // Custom exception
+    // NOTE: there is no way in v8 to subclass the Error built-in type
+    // TODO: this is an horrible hack
+    inline for (Types) |s| {
+        const Struct = s.defaultValue().?;
+        if (@hasDecl(Struct, "ErrorSet")) {
+            const script = comptime js.classNameForStruct(Struct) ++ ".prototype.__proto__ = Error.prototype";
+            _ = try context.exec(script, "errorSubclass");
+        }
+    }
+
+    // Primitive attributes are set directly on the FunctionTemplate
+    // when we setup the environment. But we cannot set more complex
+    // types (v8 will crash).
+    //
+    // Plus, just to create more complex types, we always need a
+    // context, i.e. an Array has to have a Context to exist.
+    //
+    // As far as I can tell, getting the FunctionTemplate's object
+    // and setting values directly on it, for each context, is the
+    // way to do this.
+    inline for (Types, 0..) |s, i| {
+        const Struct = s.defaultValue().?;
+        inline for (@typeInfo(Struct).@"struct".decls) |declaration| {
+            const name = declaration.name;
+            if (comptime name[0] == '_') {
+                const value = @field(Struct, name);
+
+                if (comptime js.isComplexAttributeType(@typeInfo(@TypeOf(value)))) {
+                    const js_obj = templates[i].getFunction(v8_context).toObject();
+                    const js_name = v8.String.initUtf8(isolate, name[1..]).toName();
+                    const js_val = try context.zigValueToJs(value);
+                    if (!js_obj.setValue(v8_context, js_name, js_val)) {
+                        log.fatal(.app, "set class attribute", .{
+                            .@"struct" = @typeName(Struct),
+                            .name = name,
+                        });
+                    }
+                }
+            }
+        }
+    }
+
+    try context.setupGlobal();
+    return context;
+}
+
+pub fn removeContext(self: *ExecutionWorld) void {
+    // Force running the micro task to drain the queue before reseting the
+    // context arena.
+    // Tasks in the queue are relying to the arena memory could be present in
+    // the queue. Running them later could lead to invalid memory accesses.
+    self.env.runMicrotasks();
+
+    self.context.?.deinit();
+    self.context = null;
+    _ = self.context_arena.reset(.{ .retain_with_limit = CONTEXT_ARENA_RETAIN });
+}
+
+pub fn terminateExecution(self: *const ExecutionWorld) void {
+    self.env.isolate.terminateExecution();
+}
+
+pub fn resumeExecution(self: *const ExecutionWorld) void {
+    self.env.isolate.cancelTerminateExecution();
+}

src/browser/js/Function.zig

@@ -0,0 +1,144 @@
+const std = @import("std");
+const js = @import("js.zig");
+const v8 = js.v8;
+
+const Caller = @import("Caller.zig");
+const Context = @import("Context.zig");
+const PersistentFunction = v8.Persistent(v8.Function);
+
+const Allocator = std.mem.Allocator;
+
+const Function = @This();
+
+id: usize,
+context: *js.Context,
+this: ?v8.Object = null,
+func: PersistentFunction,
+
+pub const Result = struct {
+    stack: ?[]const u8,
+    exception: []const u8,
+};
+
+pub fn getName(self: *const Function, allocator: Allocator) ![]const u8 {
+    const name = self.func.castToFunction().getName();
+    return self.context.valueToString(name, .{ .allocator = allocator });
+}
+
+pub fn setName(self: *const Function, name: []const u8) void {
+    const v8_name = v8.String.initUtf8(self.context.isolate, name);
+    self.func.castToFunction().setName(v8_name);
+}
+
+pub fn withThis(self: *const Function, value: anytype) !Function {
+    const this_obj = if (@TypeOf(value) == js.Object)
+        value.js_obj
+    else
+        (try self.context.zigValueToJs(value)).castTo(v8.Object);
+
+    return .{
+        .id = self.id,
+        .this = this_obj,
+        .func = self.func,
+        .context = self.context,
+    };
+}
+
+pub fn newInstance(self: *const Function, result: *Result) !js.Object {
+    const context = self.context;
+
+    var try_catch: js.TryCatch = undefined;
+    try_catch.init(context);
+    defer try_catch.deinit();
+
+    // This creates a new instance using this Function as a constructor.
+    // This returns a generic Object
+    const js_obj = self.func.castToFunction().initInstance(context.v8_context, &.{}) orelse {
+        if (try_catch.hasCaught()) {
+            const allocator = context.call_arena;
+            result.stack = try_catch.stack(allocator) catch null;
+            result.exception = (try_catch.exception(allocator) catch "???") orelse "???";
+        } else {
+            result.stack = null;
+            result.exception = "???";
+        }
+        return error.JsConstructorFailed;
+    };
+
+    return .{
+        .context = context,
+        .js_obj = js_obj,
+    };
+}
+
+pub fn call(self: *const Function, comptime T: type, args: anytype) !T {
+    return self.callWithThis(T, self.getThis(), args);
+}
+
+pub fn tryCall(self: *const Function, comptime T: type, args: anytype, result: *Result) !T {
+    return self.tryCallWithThis(T, self.getThis(), args, result);
+}
+
+pub fn tryCallWithThis(self: *const Function, comptime T: type, this: anytype, args: anytype, result: *Result) !T {
+    var try_catch: js.TryCatch = undefined;
+    try_catch.init(self.context);
+    defer try_catch.deinit();
+
+    return self.callWithThis(T, this, args) catch |err| {
+        if (try_catch.hasCaught()) {
+            const allocator = self.context.call_arena;
+            result.stack = try_catch.stack(allocator) catch null;
+            result.exception = (try_catch.exception(allocator) catch @errorName(err)) orelse @errorName(err);
+        } else {
+            result.stack = null;
+            result.exception = @errorName(err);
+        }
+        return err;
+    };
+}
+
+pub fn callWithThis(self: *const Function, comptime T: type, this: anytype, args: anytype) !T {
+    const context = self.context;
+
+    const js_this = try context.valueToExistingObject(this);
+
+    const aargs = if (comptime @typeInfo(@TypeOf(args)) == .null) struct {}{} else args;
+
+    const js_args: []const v8.Value = switch (@typeInfo(@TypeOf(aargs))) {
+        .@"struct" => |s| blk: {
+            const fields = s.fields;
+            var js_args: [fields.len]v8.Value = undefined;
+            inline for (fields, 0..) |f, i| {
+                js_args[i] = try context.zigValueToJs(@field(aargs, f.name));
+            }
+            const cargs: [fields.len]v8.Value = js_args;
+            break :blk &cargs;
+        },
+        .pointer => blk: {
+            var values = try context.call_arena.alloc(v8.Value, args.len);
+            for (args, 0..) |a, i| {
+                values[i] = try context.zigValueToJs(a);
+            }
+            break :blk values;
+        },
+        else => @compileError("JS Function called with invalid paremter type"),
+    };
+
+    const result = self.func.castToFunction().call(context.v8_context, js_this, js_args);
+    if (result == null) {
+        return error.JSExecCallback;
+    }
+
+    if (@typeInfo(T) == .void) return {};
+    const named_function = comptime Caller.NamedFunction.init(T, "callResult");
+    return context.jsValueToZig(named_function, T, result.?);
+}
+
+fn getThis(self: *const Function) v8.Object {
+    return self.this orelse self.context.v8_context.getGlobal();
+}
+
+pub fn src(self: *const Function) ![]const u8 {
+    const value = self.func.castToFunction().toValue();
+    return self.context.valueToString(value, .{});
+}