Native IntersectionObserver

src/browser/browser.zig

@@ -829,7 +829,7 @@ const FlatRenderer = struct {
     }
 
     pub fn width(self: *const FlatRenderer) u32 {
-        return @intCast(self.elements.items.len);
+        return @intCast(self.elements.items.len + 1); // +1 since x starts at 1 (use len after append)
     }
 
     pub fn height(_: *const FlatRenderer) u32 {

src/browser/dom/dom.zig

@@ -24,6 +24,7 @@ const DOMTokenList = @import("token_list.zig");
 const NodeList = @import("nodelist.zig");
 const Node = @import("node.zig");
 const MutationObserver = @import("mutation_observer.zig");
+const IntersectionObserver = @import("intersection_observer.zig");
 
 pub const Interfaces = .{
     DOMException,
@@ -35,4 +36,5 @@ pub const Interfaces = .{
     Node.Node,
     Node.Interfaces,
     MutationObserver.Interfaces,
+    IntersectionObserver.Interfaces,
 };

src/browser/dom/element.zig

@@ -346,6 +346,14 @@ pub const Element = struct {
         return state.renderer.getRect(self);
     }
 
+    // returns a collection of DOMRect objects that indicate the bounding rectangles for each CSS border box in a client.
+    // We do not render so just always return the element's rect.
+    pub fn _getClientRects(self: *parser.Element, state: *SessionState) ![]DOMRect {
+        var heap = try state.arena.create(DOMRect);
+        heap.* = try state.renderer.getRect(self);
+        return heap[0..1];
+    }
+
     pub fn get_clientWidth(_: *parser.Element, state: *SessionState) u32 {
         return state.renderer.width();
     }

src/browser/dom/intersection_observer.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 Allocator = std.mem.Allocator;
+
+const parser = @import("../netsurf.zig");
+const SessionState = @import("../env.zig").SessionState;
+
+const Env = @import("../env.zig").Env;
+const Element = @import("element.zig").Element;
+const Document = @import("document.zig").Document;
+
+pub const Interfaces = .{
+    IntersectionObserver,
+    IntersectionObserverEntry,
+};
+
+const log = std.log.scoped(.events);
+
+// 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 {
+    callback: Env.Callback,
+    options: IntersectionObserverOptions,
+    state: *SessionState,
+
+    observed_entries: std.ArrayListUnmanaged(IntersectionObserverEntry),
+
+    // new IntersectionObserver(callback)
+    // new IntersectionObserver(callback, options) [not supported yet]
+    pub fn constructor(callback: Env.Callback, options_: ?IntersectionObserverOptions, state: *SessionState) !IntersectionObserver {
+        if (options_ != null) return error.IntersectionObserverOptionsNotYetSupported;
+        const options = IntersectionObserverOptions{
+            .root = parser.documentToNode(parser.documentHTMLToDocument(state.document.?)),
+            .rootMargin = "0px 0px 0px 0px",
+            .threshold = &[_]f32{0.0},
+        };
+
+        return .{
+            .callback = callback,
+            .options = options,
+            .state = state,
+            .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, targetElement: *parser.Element) !void {
+        try self.observed_entries.append(self.state.arena, .{
+            .state = self.state,
+            .target = targetElement,
+            .options = &self.options,
+        });
+
+        var result: Env.Callback.Result = undefined;
+        self.callback.tryCall(.{self.observed_entries.items}, &result) catch {
+            log.err("intersection observer callback error: {s}", .{result.exception});
+            log.debug("stack:\n{s}", .{result.stack orelse "???"});
+        };
+    }
+
+    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: ?[]const f32,
+};
+
+// https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserverEntry
+// https://w3c.github.io/IntersectionObserver/#intersection-observer-entry
+pub const IntersectionObserverEntry = struct {
+    state: *SessionState,
+    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 self.state.renderer.getRect(self.target); // Does this ever change?
+    }
+
+    // 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 self.state.renderer.getRect(self.target);
+    }
+
+    // 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 isIntersecting(_: *const IntersectionObserverEntry) bool {
+        return true;
+    }
+
+    // Returns a DOMRectReadOnly for the intersection observer's root.
+    pub fn get_rootBounds(self: *const IntersectionObserverEntry) !Element.DOMRect {
+        // TODO self.options.root can be an Element or a Document when Options are supported
+        const element = (try parser.documentGetDocumentElement(parser.documentHTMLToDocument(self.state.document.?))).?;
+        return try self.state.renderer.getRect(element);
+    }
+
+    // The Element whose intersection with the root changed.
+    pub fn get_target(self: *const IntersectionObserverEntry) *parser.Element {
+        return self.target;
+    }
+};