Native IntersectionObserver

src/browser/browser.zig

@@ -828,8 +828,17 @@ const FlatRenderer = struct {
         };
     }
 
+    pub fn boundingRect(self: *const FlatRenderer) Element.DOMRect {
+        return .{
+            .x = 0.0,
+            .y = 0.0,
+            .width = @floatFromInt(self.width()),
+            .height = @floatFromInt(self.height()),
+        };
+    }
+
     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 +346,12 @@ 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) ![1]DOMRect {
+        return [_]DOMRect{try state.renderer.getRect(self)};
+    }
+
     pub fn get_clientWidth(_: *parser.Element, state: *SessionState) u32 {
         return state.renderer.width();
     }
@@ -498,7 +504,7 @@ test "Browser.DOM.Element" {
     }, .{});
 
     try runner.testCases(&.{
-        .{ "document.getElementById('para').clientWidth", "0" },
+        .{ "document.getElementById('para').clientWidth", "1" },
         .{ "document.getElementById('para').clientHeight", "1" },
 
         .{ "let r1 = document.getElementById('para').getBoundingClientRect()", "undefined" },
@@ -519,7 +525,7 @@ test "Browser.DOM.Element" {
         .{ "r3.width", "1" },
         .{ "r3.height", "1" },
 
-        .{ "document.getElementById('para').clientWidth", "2" },
+        .{ "document.getElementById('para').clientWidth", "3" },
         .{ "document.getElementById('para').clientHeight", "1" },
     }, .{});
 

src/browser/dom/intersection_observer.zig

@@ -0,0 +1,278 @@
+// 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 {
+        var options = IntersectionObserverOptions{
+            .root = parser.documentToNode(parser.documentHTMLToDocument(state.document.?)),
+            .rootMargin = "0px 0px 0px 0px",
+            .threshold = &.{0.0},
+        };
+        if (options_) |*o| {
+            if (o.root) |root| {
+                options.root = root;
+            } // Other properties are not used due to the way we render
+        }
+
+        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, 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.state.arena, .{
+            .state = self.state,
+            .target = target_element,
+            .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);
+    }
+
+    // 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 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.state.document.?)) {
+            return self.state.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 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;
+    }
+
+    // TODO: pub fn get_time(self: *const IntersectionObserverEntry)
+};
+
+const testing = @import("../../testing.zig");
+test "Browser.DOM.IntersectionObserver" {
+    var runner = try testing.jsRunner(testing.tracking_allocator, .{});
+    defer runner.deinit();
+
+    try runner.testCases(&.{
+        .{ "new IntersectionObserver(() => {}).observe(document.documentElement);", "undefined" },
+    }, .{});
+
+    try runner.testCases(&.{
+        .{ "let count_a = 0;", "undefined" },
+        .{ "const a1 = document.createElement('div');", "undefined" },
+        .{ "new IntersectionObserver(entries => {count_a += 1;}).observe(a1);", "undefined" },
+        .{ "count_a;", "1" },
+    }, .{});
+
+    // This test is documenting current behavior, not correct behavior.
+    // Currently every time observe is called, the callback is called with all entries.
+    try runner.testCases(&.{
+        .{ "let count_b = 0;", "undefined" },
+        .{ "let observer_b = new IntersectionObserver(entries => {count_b = entries.length;});", "undefined" },
+        .{ "const b1 = document.createElement('div');", "undefined" },
+        .{ "observer_b.observe(b1);", "undefined" },
+        .{ "count_b;", "1" },
+        .{ "const b2 = document.createElement('div');", "undefined" },
+        .{ "observer_b.observe(b2);", "undefined" },
+        .{ "count_b;", "2" },
+    }, .{});
+
+    // Re-observing is a no-op
+    try runner.testCases(&.{
+        .{ "let count_bb = 0;", "undefined" },
+        .{ "let observer_bb = new IntersectionObserver(entries => {count_bb = entries.length;});", "undefined" },
+        .{ "const bb1 = document.createElement('div');", "undefined" },
+        .{ "observer_bb.observe(bb1);", "undefined" },
+        .{ "count_bb;", "1" },
+        .{ "observer_bb.observe(bb1);", "undefined" },
+        .{ "count_bb;", "1" }, // Still 1, not 2
+    }, .{});
+
+    // Unobserve
+    try runner.testCases(&.{
+        .{ "let count_c = 0;", "undefined" },
+        .{ "let observer_c = new IntersectionObserver(entries => { count_c = entries.length;});", "undefined" },
+        .{ "const c1 = document.createElement('div');", "undefined" },
+        .{ "observer_c.observe(c1);", "undefined" },
+        .{ "count_c;", "1" },
+        .{ "observer_c.unobserve(c1);", "undefined" },
+        .{ "const c2 = document.createElement('div');", "undefined" },
+        .{ "observer_c.observe(c2);", "undefined" },
+        .{ "count_c;", "1" },
+    }, .{});
+
+    // Disconnect
+    try runner.testCases(&.{
+        .{ "let observer_d = new IntersectionObserver(entries => {});", "undefined" },
+        .{ "let d1 = document.createElement('div');", "undefined" },
+        .{ "observer_d.observe(d1);", "undefined" },
+        .{ "observer_d.disconnect();", "undefined" },
+        .{ "observer_d.takeRecords().length;", "0" },
+    }, .{});
+
+    // takeRecords
+    try runner.testCases(&.{
+        .{ "let observer_e = new IntersectionObserver(entries => {});", "undefined" },
+        .{ "let e1 = document.createElement('div');", "undefined" },
+        .{ "observer_e.observe(e1);", "undefined" },
+        .{ "const e2 = document.createElement('div');", "undefined" },
+        .{ "observer_e.observe(e2);", "undefined" },
+        .{ "observer_e.takeRecords().length;", "2" },
+    }, .{});
+
+    // Entry
+    try runner.testCases(&.{
+        .{ "let entry;", "undefined" },
+        .{ "new IntersectionObserver(entries => { entry = entries[0]; }).observe(document.createElement('div'));", "undefined" },
+        .{ "entry.boundingClientRect.x;", "1" },
+        .{ "entry.intersectionRatio;", "1" },
+        .{ "entry.intersectionRect.x;", "1" },
+        .{ "entry.intersectionRect.y;", "0" },
+        .{ "entry.intersectionRect.width;", "1" },
+        .{ "entry.intersectionRect.height;", "1" },
+        .{ "entry.isIntersecting;", "true" },
+        .{ "entry.rootBounds.x;", "0" },
+        .{ "entry.rootBounds.y;", "0" },
+        .{ "entry.rootBounds.width;", "2" },
+        .{ "entry.rootBounds.height;", "1" },
+        .{ "entry.target;", "[object HTMLDivElement]" },
+    }, .{});
+
+    // Options
+    try runner.testCases(&.{
+        .{ "const new_root = document.createElement('span');", "undefined" },
+        .{ "let new_entry;", "undefined" },
+        .{
+            \\ const new_observer = new IntersectionObserver(
+            \\ entries => { new_entry = entries[0]; },
+            \\ {root: new_root, rootMargin: '0px 0px 0px 0px', threshold: [0]});
+            ,
+            "undefined",
+        },
+        .{ "new_observer.observe(document.createElement('div'));", "undefined" },
+        .{ "new_entry.rootBounds.x;", "2" },
+    }, .{});
+}

src/browser/netsurf.zig

@@ -1278,6 +1278,11 @@ pub inline fn nodeToElement(node: *Node) *Element {
     return @as(*Element, @ptrCast(node));
 }
 
+// nodeToDocument is an helper to convert a node to an document.
+pub inline fn nodeToDocument(node: *Node) *Document {
+    return @as(*Document, @ptrCast(node));
+}
+
 // CharacterData
 pub const CharacterData = c.dom_characterdata;