From 950182986a2ba5f720d3ee1f9053e68561279e0e Mon Sep 17 00:00:00 2001
From: Karl Seguin <k@openmymind.io>
Date: Wed, 27 Aug 2025 09:04:21 +0800
Subject: [PATCH] Start working on HTMLSlotElement

---
 src/browser/dom/element.zig           |  11 +++
 src/browser/dom/node.zig              |  17 ++++-
 src/browser/html/elements.zig         | 102 ++++++++++++++++++++++++++
 src/browser/netsurf.zig               |   2 +
 src/tests/html/html_slot_element.html |  66 +++++++++++++++++
 vendor/netsurf/libdom                 |   2 +-
 6 files changed, 197 insertions(+), 3 deletions(-)
 create mode 100644 src/tests/html/html_slot_element.html

diff --git a/src/browser/dom/element.zig b/src/browser/dom/element.zig
index 5043c4cb..5482dc65 100644
--- a/src/browser/dom/element.zig
+++ b/src/browser/dom/element.zig
@@ -560,6 +560,17 @@ pub const Element = struct {
         state.shadow_root = sr;
         parser.documentFragmentSetHost(sr.proto, @ptrCast(@alignCast(self)));
 
+        // Storing the ShadowRoot on the element makes sense, it's the ShadowRoot's
+        // parent. When we render, we go top-down, so we'll have the element, get
+        // its shadowroot, and go on. that's what the above code does.
+        // But we sometimes need to go bottom-up, e.g when we have a slot element
+        // and want to find the containing parent. Unforatunately , we don't have
+        // that link, so we need to create it. In the DOM, the ShadowRoot is
+        // represented by this DocumentFragment (it's the ShadowRoot's base prototype)
+        // So we can also store the ShadowRoot in the DocumentFragment's state.
+        const fragment_state = try page.getOrCreateNodeState(@ptrCast(@alignCast(fragment)));
+        fragment_state.shadow_root = sr;
+
         return sr;
     }
 
diff --git a/src/browser/dom/node.zig b/src/browser/dom/node.zig
index aa3933d0..5dc171b4 100644
--- a/src/browser/dom/node.zig
+++ b/src/browser/dom/node.zig
@@ -37,6 +37,7 @@ const DocumentFragment = @import("document_fragment.zig").DocumentFragment;
 const HTMLCollection = @import("html_collection.zig").HTMLCollection;
 const HTMLAllCollection = @import("html_collection.zig").HTMLAllCollection;
 const HTMLCollectionIterator = @import("html_collection.zig").HTMLCollectionIterator;
+const ShadowRoot = @import("shadow_root.zig").ShadowRoot;
 const Walker = @import("walker.zig").WalkerDepthFirst;
 
 // HTML
@@ -354,11 +355,23 @@ pub const Node = struct {
     // - An Element inside a standard web page will return an HTMLDocument object representing the entire page (or <iframe>).
     // - An Element inside a shadow DOM will return the associated ShadowRoot.
     // - An Element that is not attached to a document or a shadow tree will return the root of the DOM tree it belongs to
-    pub fn _getRootNode(self: *parser.Node, options: ?struct { composed: bool = false }) !Union {
+    const GetRootNodeResult = union(enum) {
+        shadow_root: *ShadowRoot,
+        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" });
         };
-        return try Node.toInterface(try parser.nodeGetRootNode(self));
+
+        const root = try parser.nodeGetRootNode(self);
+        if (page.getNodeState(root)) |state| {
+            if (state.shadow_root) |sr| {
+                return .{ .shadow_root = sr };
+            }
+        }
+
+        return .{ .node = try Node.toInterface(root) };
     }
 
     pub fn _hasChildNodes(self: *parser.Node) !bool {
diff --git a/src/browser/html/elements.zig b/src/browser/html/elements.zig
index a3f667df..6acb818e 100644
--- a/src/browser/html/elements.zig
+++ b/src/browser/html/elements.zig
@@ -26,6 +26,7 @@ const Page = @import("../page.zig").Page;
 const urlStitch = @import("../../url.zig").URL.stitch;
 const URL = @import("../url/url.zig").URL;
 const Node = @import("../dom/node.zig").Node;
+const NodeUnion = @import("../dom/node.zig").Union;
 const Element = @import("../dom/element.zig").Element;
 const DataSet = @import("DataSet.zig");
 
@@ -85,6 +86,7 @@ pub const Interfaces = .{
     HTMLScriptElement,
     HTMLSourceElement,
     HTMLSpanElement,
+    HTMLSlotElement,
     HTMLStyleElement,
     HTMLTableElement,
     HTMLTableCaptionElement,
@@ -1008,6 +1010,101 @@ pub const HTMLSpanElement = struct {
     pub const subtype = .node;
 };
 
+pub const HTMLSlotElement = struct {
+    pub const Self = parser.Slot;
+    pub const prototype = *HTMLElement;
+    pub const subtype = .node;
+
+    pub fn get_name(self: *parser.Slot) !?[]const u8 {
+        return (try parser.elementGetAttribute(@ptrCast(@alignCast(self)), "name")) orelse "";
+    }
+
+    pub fn set_name(self: *parser.Slot, value: []const u8) !void {
+        return parser.elementSetAttribute(@ptrCast(@alignCast(self)), "name", value);
+    }
+
+    const AssignedNodesOpts = 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];
+    }
+
+    fn findAssignedSlotNodes(self: *parser.Slot, opts: AssignedNodesOpts, page: *Page) !?[]NodeUnion {
+        if (opts.flatten) {
+            log.warn(.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.?));
+                }
+                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;
+            }
+        }
+        return if (arr.items.len == 0) null else arr.items;
+    }
+
+    fn nullableStringsAreEqual(a: ?[]const u8, b: ?[]const u8) bool {
+        if (a == null and b == null) {
+            return true;
+        }
+        if (a) |aa| {
+            const bb = b orelse return false;
+            return std.mem.eql(u8, aa, bb);
+        }
+
+        // a is null, but b isn't (else the first guard clause would have hit)
+        return false;
+    }
+};
+
 pub const HTMLStyleElement = struct {
     pub const Self = parser.Style;
     pub const prototype = *HTMLElement;
@@ -1168,6 +1265,7 @@ pub fn toInterfaceFromTag(comptime T: type, e: *parser.Element, tag: parser.Tag)
         .select => .{ .HTMLSelectElement = @as(*parser.Select, @ptrCast(e)) },
         .source => .{ .HTMLSourceElement = @as(*parser.Source, @ptrCast(e)) },
         .span => .{ .HTMLSpanElement = @as(*parser.Span, @ptrCast(e)) },
+        .slot => .{ .HTMLSlotElement = @as(*parser.Slot, @ptrCast(e)) },
         .style => .{ .HTMLStyleElement = @as(*parser.Style, @ptrCast(e)) },
         .table => .{ .HTMLTableElement = @as(*parser.Table, @ptrCast(e)) },
         .caption => .{ .HTMLTableCaptionElement = @as(*parser.TableCaption, @ptrCast(e)) },
@@ -1484,6 +1582,10 @@ test "Browser: HTML.HTMLScriptElement" {
     try testing.htmlRunner("html/script/inline_defer.html");
 }
 
+test "Browser: HTML.HTMLSlotElement" {
+    try testing.htmlRunner("html/html_slot_element.html");
+}
+
 const Check = struct {
     input: []const u8,
     expected: ?[]const u8 = null, // Needed when input != expected
diff --git a/src/browser/netsurf.zig b/src/browser/netsurf.zig
index 57a13d65..079dfc0c 100644
--- a/src/browser/netsurf.zig
+++ b/src/browser/netsurf.zig
@@ -259,6 +259,7 @@ pub const Tag = enum(u8) {
     _var = c.DOM_HTML_ELEMENT_TYPE_VAR,
     video = c.DOM_HTML_ELEMENT_TYPE_VIDEO,
     wbr = c.DOM_HTML_ELEMENT_TYPE_WBR,
+    slot = c.DOM_HTML_ELEMENT_TYPE_SLOT,
     undef = c.DOM_HTML_ELEMENT_TYPE__UNKNOWN,
 
     pub fn all() []Tag {
@@ -1973,6 +1974,7 @@ pub const Script = c.dom_html_script_element;
 pub const Select = c.dom_html_select_element;
 pub const Source = struct { base: *c.dom_html_element };
 pub const Span = struct { base: *c.dom_html_element };
+pub const Slot = c.dom_html_slot_element;
 pub const Style = c.dom_html_style_element;
 pub const Table = c.dom_html_table_element;
 pub const TableCaption = c.dom_html_table_caption_element;
diff --git a/src/tests/html/html_slot_element.html b/src/tests/html/html_slot_element.html
new file mode 100644
index 00000000..058b6785
--- /dev/null
+++ b/src/tests/html/html_slot_element.html
@@ -0,0 +1,66 @@
+<script src="../testing.js"></script>
+<script>
+  class LightPanda extends HTMLElement {
+    constructor() {
+      super();
+    }
+
+    connectedCallback() {
+      const shadow = this.attachShadow({ mode: "open" });
+
+      const slot1 = document.createElement('slot');
+      slot1.name = 'slot-1';
+      shadow.appendChild(slot1);
+
+      switch (this.getAttribute('mode')) {
+        case '1':
+          slot1.innerHTML = 'hello';
+          break;
+        case '2':
+          const slot2 = document.createElement('slot');
+          shadow.appendChild(slot2);
+          break;
+      }
+    }
+  }
+  window.customElements.define("lp-test", LightPanda);
+</script>
+
+<lp-test id=lp1 mode=1></lp-test>
+<lp-test id=lp2 mode=0></lp-test>
+<lp-test id=lp3 mode=0>default</lp-test>
+<lp-test id=lp4 mode=1><p slot=other>default</p></lp-test>
+<lp-test id=lp5 mode=1><p slot=slot-1>default</p> xx <b slot=slot-1>other</b></lp-test>
+<lp-test id=lp6 mode=2>More <p slot=slot-1>default2</p> <span>!!</span></lp-test>
+
+<script id=HTMLSlotElement>
+  function assertNodes(expected, actual) {
+    actual = actual.map((n) => n.id || n.textContent)
+    testing.expectEqual(expected, actual);
+  }
+
+  for (let idx of [1, 2, 3, 4]) {
+    const lp = $(`#lp${idx}`);
+    const slot = lp.shadowRoot.querySelector('slot');
+
+    assertNodes([], slot.assignedNodes());
+    assertNodes([], slot.assignedNodes({}));
+    assertNodes([], slot.assignedNodes({flatten: false}));
+    if (lp.getAttribute('mode') === '1') {
+      assertNodes(['hello'], slot.assignedNodes({flatten: true}));
+    } else {
+      assertNodes([], slot.assignedNodes({flatten: true}));
+    }
+  }
+
+  const lp5 = $('#lp5');
+  const s5 = lp5.shadowRoot.querySelector('slot');
+  assertNodes(['default', 'other'], s5.assignedNodes());
+
+  const lp6 = $('#lp6');
+  const s6 = lp6.shadowRoot.querySelectorAll('slot');
+  assertNodes(['default2'], s6[0].assignedNodes({}));
+  assertNodes(['default2'], s6[0].assignedNodes({flatten: true}));
+  assertNodes(['More ', ' ', '!!'], s6[1].assignedNodes({}));
+  assertNodes(['More ', ' ', '!!'], s6[1].assignedNodes({flatten: true}));
+</script>
diff --git a/vendor/netsurf/libdom b/vendor/netsurf/libdom
index c0df4581..120717ba 160000
--- a/vendor/netsurf/libdom
+++ b/vendor/netsurf/libdom
@@ -1 +1 @@
-Subproject commit c0df458132162aba136d57ce1ba2179122a9e717
+Subproject commit 120717bad4e46c3fee559aff9728a5c0dbc9c8f2