Print action requests from our subtree

Co-authored-by: Delan Azabani <dazabani@igalia.com>
Signed-off-by: Luke Warlow <lwarlow@igalia.com>

Cargo.lock

@@ -18,45 +18,60 @@ version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "366ffbaa4442f4684d91e2cd7c5ea7c4ed8add41959a31447066e279e432b618"
 
+[[package]]
+name = "accessibility_traits"
+version = "0.0.1"
+dependencies = [
+ "accesskit",
+ "base",
+ "crossbeam-channel",
+ "ipc-channel",
+ "malloc_size_of_derive",
+ "rustc-hash 2.1.1",
+ "serde",
+ "servo_malloc_size_of",
+ "strum",
+]
+
 [[package]]
 name = "accesskit"
 version = "0.21.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cf203f9d3bd8f29f98833d1fbef628df18f759248a547e7e01cfbf63cda36a99"
+source = "git+https://github.com/AccessKit/accesskit.git?rev=783c1e8fea164f337a0cd62739fb6e59f159d77c#783c1e8fea164f337a0cd62739fb6e59f159d77c"
+dependencies = [
+ "enumn",
+ "serde",
+ "uuid",
+]
 
 [[package]]
 name = "accesskit_atspi_common"
 version = "0.14.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "890d241cf51fc784f0ac5ac34dfc847421f8d39da6c7c91a0fcc987db62a8267"
+source = "git+https://github.com/AccessKit/accesskit.git?rev=783c1e8fea164f337a0cd62739fb6e59f159d77c#783c1e8fea164f337a0cd62739fb6e59f159d77c"
 dependencies = [
  "accesskit",
  "accesskit_consumer",
  "atspi-common",
  "serde",
- "thiserror 1.0.69",
  "zvariant",
 ]
 
 [[package]]
 name = "accesskit_consumer"
 version = "0.31.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "db81010a6895d8707f9072e6ce98070579b43b717193d2614014abd5cb17dd43"
+source = "git+https://github.com/AccessKit/accesskit.git?rev=783c1e8fea164f337a0cd62739fb6e59f159d77c#783c1e8fea164f337a0cd62739fb6e59f159d77c"
 dependencies = [
  "accesskit",
- "hashbrown 0.15.5",
+ "hashbrown 0.16.0",
 ]
 
 [[package]]
 name = "accesskit_macos"
 version = "0.22.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a0089e5c0ac0ca281e13ea374773898d9354cc28d15af9f0f7394d44a495b575"
+source = "git+https://github.com/AccessKit/accesskit.git?rev=783c1e8fea164f337a0cd62739fb6e59f159d77c#783c1e8fea164f337a0cd62739fb6e59f159d77c"
 dependencies = [
  "accesskit",
  "accesskit_consumer",
- "hashbrown 0.15.5",
+ "hashbrown 0.16.0",
  "objc2 0.5.2",
  "objc2-app-kit 0.2.2",
  "objc2-foundation 0.2.2",
@@ -65,8 +80,7 @@ dependencies = [
 [[package]]
 name = "accesskit_unix"
 version = "0.17.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "301e55b39cfc15d9c48943ce5f572204a551646700d0e8efa424585f94fec528"
+source = "git+https://github.com/AccessKit/accesskit.git?rev=783c1e8fea164f337a0cd62739fb6e59f159d77c#783c1e8fea164f337a0cd62739fb6e59f159d77c"
 dependencies = [
  "accesskit",
  "accesskit_atspi_common",
@@ -83,12 +97,11 @@ dependencies = [
 [[package]]
 name = "accesskit_windows"
 version = "0.29.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d2d63dd5041e49c363d83f5419a896ecb074d309c414036f616dc0b04faca971"
+source = "git+https://github.com/AccessKit/accesskit.git?rev=783c1e8fea164f337a0cd62739fb6e59f159d77c#783c1e8fea164f337a0cd62739fb6e59f159d77c"
 dependencies = [
  "accesskit",
  "accesskit_consumer",
- "hashbrown 0.15.5",
+ "hashbrown 0.16.0",
  "static_assertions",
  "windows 0.61.3",
  "windows-core 0.61.2",
@@ -631,20 +644,19 @@ checksum = "41e67cd8309bbd06cd603a9e693a784ac2e5d1e955f11286e355089fcab3047c"
 
 [[package]]
 name = "atspi"
-version = "0.25.0"
+version = "0.29.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c83247582e7508838caf5f316c00791eee0e15c0bf743e6880585b867e16815c"
+checksum = "c77886257be21c9cd89a4ae7e64860c6f0eefca799bb79127913052bd0eefb3d"
 dependencies = [
  "atspi-common",
- "atspi-connection",
  "atspi-proxies",
 ]
 
 [[package]]
 name = "atspi-common"
-version = "0.9.0"
+version = "0.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "33dfc05e7cdf90988a197803bf24f5788f94f7c94a69efa95683e8ffe76cfdfb"
+checksum = "20c5617155740c98003016429ad13fe43ce7a77b007479350a9f8bf95a29f63d"
 dependencies = [
  "enumflags2",
  "serde",
@@ -656,23 +668,11 @@ dependencies = [
  "zvariant",
 ]
 
-[[package]]
-name = "atspi-connection"
-version = "0.9.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4193d51303d8332304056ae0004714256b46b6635a5c556109b319c0d3784938"
-dependencies = [
- "atspi-common",
- "atspi-proxies",
- "futures-lite",
- "zbus",
-]
-
 [[package]]
 name = "atspi-proxies"
-version = "0.9.0"
+version = "0.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d2eebcb9e7e76f26d0bcfd6f0295e1cd1e6f33bedbc5698a971db8dc43d7751c"
+checksum = "2230e48787ed3eb4088996eab66a32ca20c0b67bbd4fd6cdfe79f04f1f04c9fc"
 dependencies = [
  "atspi-common",
  "serde",
@@ -2353,8 +2353,7 @@ dependencies = [
 [[package]]
 name = "ecolor"
 version = "0.33.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "71ddb8ac7643d1dba1bb02110e804406dd459a838efcb14011ced10556711a8e"
+source = "git+https://github.com/emilk/egui.git?rev=82199c1c449ec58aca3e8f0252e2d68f2ea5f5da#82199c1c449ec58aca3e8f0252e2d68f2ea5f5da"
 dependencies = [
  "bytemuck",
  "emath",
@@ -2363,8 +2362,7 @@ dependencies = [
 [[package]]
 name = "egui"
 version = "0.33.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a9b567d356674e9a5121ed3fedfb0a7c31e059fe71f6972b691bcd0bfc284e3"
+source = "git+https://github.com/emilk/egui.git?rev=82199c1c449ec58aca3e8f0252e2d68f2ea5f5da#82199c1c449ec58aca3e8f0252e2d68f2ea5f5da"
 dependencies = [
  "accesskit",
  "ahash",
@@ -2394,8 +2392,7 @@ dependencies = [
 [[package]]
 name = "egui-winit"
 version = "0.33.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ec6687e5bb551702f4ad10ac428bab12acf9d53047ebb1082d4a0ed8c6251a29"
+source = "git+https://github.com/emilk/egui.git?rev=82199c1c449ec58aca3e8f0252e2d68f2ea5f5da#82199c1c449ec58aca3e8f0252e2d68f2ea5f5da"
 dependencies = [
  "accesskit_winit",
  "arboard",
@@ -2460,8 +2457,7 @@ dependencies = [
 [[package]]
 name = "emath"
 version = "0.33.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "491bdf728bf25ddd9ad60d4cf1c48588fa82c013a2440b91aa7fc43e34a07c32"
+source = "git+https://github.com/emilk/egui.git?rev=82199c1c449ec58aca3e8f0252e2d68f2ea5f5da#82199c1c449ec58aca3e8f0252e2d68f2ea5f5da"
 dependencies = [
  "bytemuck",
 ]
@@ -2470,6 +2466,7 @@ dependencies = [
 name = "embedder_traits"
 version = "0.0.1"
 dependencies = [
+ "accessibility_traits",
  "base",
  "bitflags 2.10.0",
  "cookie 0.18.1",
@@ -2552,6 +2549,17 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "enumn"
+version = "0.1.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f9ed6b3789237c8a0c1c505af1c7eb2c560df6186f01b098c3a1064ea532f38"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "env_filter"
 version = "0.1.4"
@@ -2588,8 +2596,7 @@ dependencies = [
 [[package]]
 name = "epaint"
 version = "0.33.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "009d0dd3c2163823a0abdb899451ecbc78798dec545ee91b43aff1fa790bab62"
+source = "git+https://github.com/emilk/egui.git?rev=82199c1c449ec58aca3e8f0252e2d68f2ea5f5da#82199c1c449ec58aca3e8f0252e2d68f2ea5f5da"
 dependencies = [
  "ab_glyph",
  "ahash",
@@ -2606,8 +2613,7 @@ dependencies = [
 [[package]]
 name = "epaint_default_fonts"
 version = "0.33.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5c4fbe202b6578d3d56428fa185cdf114a05e49da05f477b3c7f0fbb221f1862"
+source = "git+https://github.com/emilk/egui.git?rev=82199c1c449ec58aca3e8f0252e2d68f2ea5f5da#82199c1c449ec58aca3e8f0252e2d68f2ea5f5da"
 
 [[package]]
 name = "equator"
@@ -2808,6 +2814,12 @@ version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"
 
+[[package]]
+name = "foldhash"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77ce24cb58228fbb8aa041425bb1050850ac19177686ea6e0f41a70416f56fdb"
+
 [[package]]
 name = "font-types"
 version = "0.10.1"
@@ -3804,7 +3816,7 @@ checksum = "9229cfe53dfd69f0609a49f65461bd93001ea1ef889cd5529dd176593f5338a1"
 dependencies = [
  "allocator-api2",
  "equivalent",
- "foldhash",
+ "foldhash 0.1.5",
  "serde",
 ]
 
@@ -3813,6 +3825,9 @@ name = "hashbrown"
 version = "0.16.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5419bdc4f6a9207fbeba6d11b604d481addf78ecd10c11ad51e76c2f6482748d"
+dependencies = [
+ "foldhash 0.2.0",
+]
 
 [[package]]
 name = "hashlink"
@@ -4973,6 +4988,8 @@ dependencies = [
 name = "layout"
 version = "0.0.1"
 dependencies = [
+ "accessibility_traits",
+ "accesskit",
  "app_units",
  "atomic_refcell",
  "base",
@@ -5133,6 +5150,7 @@ dependencies = [
 name = "libservo"
 version = "0.0.1"
 dependencies = [
+ "accessibility_traits",
  "arboard",
  "background_hang_monitor",
  "base",
@@ -7876,6 +7894,7 @@ dependencies = [
 name = "script_traits"
 version = "0.0.1"
 dependencies = [
+ "accessibility_traits",
  "background_hang_monitor_api",
  "base",
  "bluetooth_traits",
@@ -8399,6 +8418,7 @@ dependencies = [
 name = "servoshell"
 version = "0.0.4"
 dependencies = [
+ "accessibility_traits",
  "android_logger",
  "backtrace",
  "base",

Cargo.toml

@@ -1,6 +1,7 @@
 [workspace]
 resolver = "2"
 members = [
+    "components/shared/accessibility",
     "components/xpath",
     "ports/servoshell",
     "tests/unit/*",
@@ -23,6 +24,8 @@ publish = false
 rust-version = "1.86.0"
 
 [workspace.dependencies]
+accessibility_traits = { path = "components/shared/accessibility" }
+accesskit = "0.21.1"
 accountable-refcell = "0.2.2"
 aes = "0.8.4"
 aes-gcm = "0.10.3"
@@ -277,6 +280,14 @@ lto = "thin"
 codegen-units = 1
 
 [patch.crates-io]
+accesskit = { git = "https://github.com/AccessKit/accesskit.git", rev = "783c1e8fea164f337a0cd62739fb6e59f159d77c" }
+accesskit_atspi_common = { git = "https://github.com/AccessKit/accesskit.git", rev = "783c1e8fea164f337a0cd62739fb6e59f159d77c" }
+accesskit_consumer = { git = "https://github.com/AccessKit/accesskit.git", rev = "783c1e8fea164f337a0cd62739fb6e59f159d77c" }
+accesskit_unix = { git = "https://github.com/AccessKit/accesskit.git", rev = "783c1e8fea164f337a0cd62739fb6e59f159d77c" }
+accesskit_macos = { git = "https://github.com/AccessKit/accesskit.git", rev = "783c1e8fea164f337a0cd62739fb6e59f159d77c" }
+accesskit_windows = { git = "https://github.com/AccessKit/accesskit.git", rev = "783c1e8fea164f337a0cd62739fb6e59f159d77c" }
+egui = { git = "https://github.com/emilk/egui.git", rev = "82199c1c449ec58aca3e8f0252e2d68f2ea5f5da" }
+egui-winit = { git = "https://github.com/emilk/egui.git", rev = "82199c1c449ec58aca3e8f0252e2d68f2ea5f5da" }
 # If you need to temporarily test Servo with a local fork of some upstream
 # crate, add that here. Use the form:
 #

components/layout/Cargo.toml

@@ -17,6 +17,8 @@ doctest = false
 tracing = ["dep:tracing"]
 
 [dependencies]
+accessibility_traits = { workspace = true }
+accesskit = { workspace = true }
 app_units = { workspace = true }
 atomic_refcell = { workspace = true }
 base = { workspace = true }

components/layout/accessibility_tree.rs

@@ -0,0 +1,200 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use std::rc::Rc;
+use std::sync::LazyLock;
+
+pub(crate) use accessibility_traits::AccessibilityTree;
+use accesskit::{Action, Node as AxNode, NodeId as AxNodeId, Role, Tree as AxTree};
+use html5ever::{LocalName, local_name};
+use layout_api::wrapper_traits::{LayoutNode, ThreadSafeLayoutNode};
+use log::trace;
+use rustc_hash::FxHashMap;
+use script::layout_dom::ServoLayoutDocument;
+use style::dom::{NodeInfo, TDocument, TElement, TNode};
+
+use crate::FragmentTree;
+
+// #[derive(MallocSizeOf)]
+pub(crate) struct AccessibilityTreeCalculator {}
+
+impl AccessibilityTreeCalculator {
+    pub(crate) fn construct(
+        document: ServoLayoutDocument<'_>,
+        fragment_tree: Rc<FragmentTree>,
+    ) -> AccessibilityTree {
+        let mut ax_nodes: FxHashMap<AxNodeId, AxNode> = FxHashMap::default();
+        let ax_document_id = AxNodeId(document.as_node().opaque().0 as u64);
+        let ax_document = AxNode::new(Role::Document);
+        ax_nodes.insert(ax_document_id, ax_document);
+        let dom_root = document.root_element().unwrap().as_node();
+        let mut dom_queue = vec![dom_root];
+        'outer: loop {
+            // find the next node in the queue that is not ‘display: none’.
+            let dom_next = loop {
+                let Some(next) = dom_queue.pop() else {
+                    break 'outer;
+                };
+                if next
+                    .style_data()
+                    .is_none_or(|style| !style.element_data.borrow().styles.is_display_none())
+                {
+                    break next;
+                }
+            };
+            // push its children for later traversal.
+            // reverse order ensures that the first child will get popped first.
+            for child in RevDomChildren::of(dom_next) {
+                dom_queue.push(child);
+            }
+            // now process the node.
+            trace!("DOM node: {dom_next:?}");
+            let dom_parent = dom_next
+                .parent_node()
+                .expect("Even the root element must have a parent");
+            let ax_parent_id = AxNodeId(dom_parent.opaque().0 as u64);
+            let ax_next_id = AxNodeId(dom_next.opaque().0 as u64);
+            let ax_parent = ax_nodes.get_mut(&ax_parent_id).expect("Guaranteed by us");
+            ax_parent.push_child(ax_next_id);
+            let mut ax_next = AxNode::default();
+            if dom_next.is_text_node() {
+                let text_content = dom_next.to_threadsafe().text_content();
+                trace!("node text content = {:?}", text_content);
+                ax_next.set_value(&*text_content);
+                // FIXME: this should take into account editing selection units (grapheme clusters?)
+                ax_next.set_character_lengths(
+                    text_content
+                        .chars()
+                        .map(|c| c.len_utf8() as u8)
+                        .collect::<Box<[u8]>>(),
+                );
+                ax_next.set_role(Role::TextRun);
+            } else if let Some(element) = dom_next.as_element() {
+                if element.is_html_element() {
+                    if let Some(role) = HTML_ELEMENT_ROLE_MAPPINGS.get(element.local_name()) {
+                        ax_next.set_role(*role);
+                    }
+                }
+            }
+            ax_next.add_action(Action::Click);
+            ax_nodes.insert(ax_next_id, ax_next);
+        }
+        AccessibilityTree {
+            ax_nodes,
+            ax_tree: AxTree {
+                root: ax_document_id,
+                toolkit_name: None,
+                toolkit_version: None,
+            },
+        }
+    }
+}
+
+/// Like [`style::dom::DomChildren`], but reversed.
+///
+/// Do not use the tuple constructor; use [`Self::of`].
+pub(crate) struct RevDomChildren<N>(Option<N>);
+impl<N: TNode> RevDomChildren<N> {
+    fn of(node: N) -> Self {
+        Self(node.last_child())
+    }
+}
+impl<N: TNode> Iterator for RevDomChildren<N> {
+    type Item = N;
+    fn next(&mut self) -> Option<N> {
+        let n = self.0.take()?;
+        self.0 = n.prev_sibling();
+        Some(n)
+    }
+}
+
+/// <https://www.w3.org/TR/html-aam-1.0/#html-element-role-mappings>
+///
+/// FIXME: converted mechanically for now, so this will have many errors
+static HTML_ELEMENT_ROLE_MAPPINGS: LazyLock<FxHashMap<LocalName, Role>> = LazyLock::new(|| {
+    [
+        (local_name!("a"), Role::Link),
+        (local_name!("address"), Role::Group),
+        (local_name!("area"), Role::Link),
+        (local_name!("area"), Role::GenericContainer),
+        (local_name!("article"), Role::Article),
+        (local_name!("aside"), Role::Complementary),
+        (local_name!("b"), Role::GenericContainer),
+        (local_name!("bdi"), Role::GenericContainer),
+        (local_name!("bdo"), Role::GenericContainer),
+        (local_name!("blockquote"), Role::Blockquote),
+        (local_name!("body"), Role::GenericContainer),
+        (local_name!("button"), Role::Button),
+        (local_name!("caption"), Role::Caption),
+        (local_name!("code"), Role::Code),
+        (local_name!("data"), Role::GenericContainer),
+        (local_name!("datalist"), Role::ListBox),
+        (local_name!("dd"), Role::Definition),
+        (local_name!("del"), Role::ContentDeletion),
+        (local_name!("details"), Role::Group),
+        (local_name!("dfn"), Role::Term),
+        (local_name!("dialog"), Role::Dialog),
+        (local_name!("dir"), Role::List),
+        (local_name!("div"), Role::GenericContainer),
+        (local_name!("dl"), Role::List),
+        (local_name!("dt"), Role::Term),
+        (local_name!("em"), Role::Emphasis),
+        (local_name!("fieldset"), Role::Group),
+        (local_name!("figcaption"), Role::Caption),
+        (local_name!("figure"), Role::Figure),
+        (local_name!("footer"), Role::ContentInfo),
+        (local_name!("form"), Role::Form),
+        (local_name!("h1"), Role::Heading),
+        (local_name!("h2"), Role::Heading),
+        (local_name!("h3"), Role::Heading),
+        (local_name!("h4"), Role::Heading),
+        (local_name!("h5"), Role::Heading),
+        (local_name!("h6"), Role::Heading),
+        (local_name!("header"), Role::Banner),
+        (local_name!("hgroup"), Role::Group),
+        (local_name!("hr"), Role::Splitter),
+        (local_name!("html"), Role::GenericContainer),
+        (local_name!("i"), Role::GenericContainer),
+        (local_name!("img"), Role::Image),
+        (local_name!("ins"), Role::ContentInsertion),
+        (local_name!("li"), Role::ListItem),
+        (local_name!("main"), Role::Main),
+        (local_name!("mark"), Role::Mark),
+        (local_name!("menu"), Role::List),
+        (local_name!("meter"), Role::Meter),
+        (local_name!("nav"), Role::Navigation),
+        (local_name!("ol"), Role::List),
+        (local_name!("optgroup"), Role::Group),
+        (local_name!("option"), Role::ListBoxOption),
+        (local_name!("output"), Role::Status),
+        (local_name!("p"), Role::Paragraph),
+        (local_name!("pre"), Role::GenericContainer),
+        (local_name!("progress"), Role::ProgressIndicator),
+        (local_name!("q"), Role::GenericContainer),
+        (local_name!("s"), Role::ContentDeletion),
+        (local_name!("samp"), Role::GenericContainer),
+        (local_name!("search"), Role::Search),
+        (local_name!("section"), Role::Region),
+        (local_name!("select"), Role::ListBox),
+        (local_name!("select"), Role::ComboBox),
+        (local_name!("small"), Role::GenericContainer),
+        (local_name!("span"), Role::GenericContainer),
+        (local_name!("strong"), Role::Strong),
+        (local_name!("table"), Role::Table),
+        (local_name!("tbody"), Role::RowGroup),
+        (local_name!("td"), Role::Cell),
+        (local_name!("textarea"), Role::TextInput),
+        (local_name!("tfoot"), Role::RowGroup),
+        (local_name!("th"), Role::Cell),
+        (local_name!("th"), Role::ColumnHeader),
+        (local_name!("th"), Role::RowHeader),
+        (local_name!("thead"), Role::RowGroup),
+        (local_name!("time"), Role::Time),
+        (local_name!("tr"), Role::Row),
+        (local_name!("u"), Role::GenericContainer),
+        (local_name!("ul"), Role::List),
+    ]
+    .into_iter()
+    .collect()
+});

components/layout/layout_impl.rs

@@ -86,6 +86,7 @@ use url::Url;
 use webrender_api::ExternalScrollId;
 use webrender_api::units::{DevicePixel, LayoutVector2D};
 
+use crate::accessibility_tree::{AccessibilityTree, AccessibilityTreeCalculator};
 use crate::context::{CachedImageOrError, ImageResolver, LayoutContext};
 use crate::display_list::{
     DisplayListBuilder, HitTest, LargestContentfulPaintCandidateCollector, StackingContextTree,
@@ -180,6 +181,7 @@ pub struct LayoutThread {
 
     /// The fragment tree.
     fragment_tree: RefCell<Option<Rc<FragmentTree>>>,
+    accessibility_tree: RefCell<Option<AccessibilityTree>>,
 
     /// The [`StackingContextTree`] cached from previous layouts.
     stacking_context_tree: RefCell<Option<StackingContextTree>>,
@@ -749,6 +751,7 @@ impl LayoutThread {
             need_new_stacking_context_tree: Cell::new(false),
             box_tree: Default::default(),
             fragment_tree: Default::default(),
+            accessibility_tree: Default::default(),
             stacking_context_tree: Default::default(),
             paint_api: config.paint_api,
             stylist: Stylist::new(device, QuirksMode::NoQuirks),
@@ -1150,6 +1153,15 @@ impl LayoutThread {
             run_layout()
         });
 
+        let accessibility_tree =
+            AccessibilityTreeCalculator::construct(document, fragment_tree.clone());
+        self.script_chan
+            .send(ScriptThreadMessage::HackySendAccessibilityTree(
+                self.webview_id,
+                accessibility_tree,
+            ))
+            .expect("TODO: panic message");
+
         *self.fragment_tree.borrow_mut() = Some(fragment_tree);
 
         if self.debug.style_tree {

components/layout/lib.rs

@@ -7,6 +7,7 @@
 //! Layout. Performs layout on the DOM, builds display lists and sends them to be
 //! painted.
 
+mod accessibility_tree;
 mod cell;
 mod context;
 mod display_list;

components/script/messaging.rs

@@ -104,6 +104,7 @@ impl MixedMessage {
                 ScriptThreadMessage::EmbedderControlResponse(id, _) => Some(id.pipeline_id),
                 ScriptThreadMessage::SetUserContents(..) => None,
                 ScriptThreadMessage::DestroyUserContentManager(..) => None,
+                ScriptThreadMessage::HackySendAccessibilityTree(..) => None,
             },
             MixedMessage::FromScript(inner_msg) => match inner_msg {
                 MainThreadScriptMsg::Common(CommonScriptMsg::Task(_, _, pipeline_id, _)) => {

components/script/script_thread.rs

@@ -1923,6 +1923,15 @@ impl ScriptThread {
                     .borrow_mut()
                     .remove(&user_content_manager_id);
             },
+            ScriptThreadMessage::HackySendAccessibilityTree(webview_id, accessibility_tree) => {
+                self.senders
+                    .pipeline_to_embedder_sender
+                    .send(EmbedderMsg::HackyAccessibilityTreeUpdate(
+                        webview_id,
+                        accessibility_tree,
+                    ))
+                    .expect("TODO: panic message");
+            },
         }
     }
 

components/servo/Cargo.toml

@@ -73,6 +73,7 @@ webxr = [
 ]
 
 [dependencies]
+accessibility_traits = { workspace = true }
 background_hang_monitor = { path = "../background_hang_monitor" }
 base = { workspace = true }
 bitflags = { workspace = true }

components/servo/servo.rs

@@ -638,6 +638,13 @@ impl ServoInner {
                     warn!("Failed to respond to GetScreenMetrics: {error}");
                 }
             },
+            EmbedderMsg::HackyAccessibilityTreeUpdate(webview_id, accessibility_tree) => {
+                if let Some(webview) = self.get_webview_handle(webview_id) {
+                    webview
+                        .delegate()
+                        .hacky_accessibility_tree_update(webview, accessibility_tree);
+                }
+            },
         }
     }
 }

components/servo/webview_delegate.rs

@@ -5,6 +5,7 @@
 use std::path::PathBuf;
 use std::rc::Rc;
 
+use accessibility_traits::AccessibilityTree;
 use base::generic_channel::GenericSender;
 use base::id::PipelineId;
 use compositing_traits::rendering_context::RenderingContext;
@@ -974,6 +975,13 @@ pub trait WebViewDelegate {
     /// A console message was logged by content in this [`WebView`].
     /// <https://developer.mozilla.org/en-US/docs/Web/API/Console_API>
     fn show_console_message(&self, _webview: WebView, _level: ConsoleLogLevel, _message: String) {}
+
+    fn hacky_accessibility_tree_update(
+        &self,
+        _webview: WebView,
+        _accessibility_tree: AccessibilityTree,
+    ) {
+    }
 }
 
 pub(crate) struct DefaultWebViewDelegate;

components/shared/accessibility/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "accessibility_traits"
+version.workspace = true
+authors.workspace = true
+license.workspace = true
+edition.workspace = true
+publish.workspace = true
+rust-version.workspace = true
+
+[lib]
+name = "accessibility_traits"
+path = "lib.rs"
+
+[dependencies]
+accesskit = { workspace = true, features = ["serde"] }
+rustc-hash = { workspace = true }
+base = { workspace = true }
+crossbeam-channel = { workspace = true }
+ipc-channel = { workspace = true }
+malloc_size_of = { workspace = true }
+malloc_size_of_derive = { workspace = true }
+serde = { workspace = true }
+strum = { workspace = true }

components/shared/accessibility/lib.rs

@@ -0,0 +1,34 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use accesskit::{Node as AxNode, NodeId as AxNodeId, Tree as AxTree};
+use rustc_hash::FxHashMap;
+use serde::{Deserialize, Serialize};
+
+#[derive(Deserialize, Serialize, Debug)]
+pub struct AccessibilityTree {
+    pub ax_nodes: FxHashMap<AxNodeId, AxNode>,
+    pub ax_tree: AxTree,
+}
+
+impl AccessibilityTree {
+    pub fn descendants(&self) -> AxDescendants<'_> {
+        AxDescendants(self, vec![self.ax_tree.root])
+    }
+}
+
+pub struct AxDescendants<'tree>(&'tree AccessibilityTree, Vec<AxNodeId>);
+impl<'tree> Iterator for AxDescendants<'tree> {
+    type Item = (AxNodeId, &'tree AxNode);
+    fn next(&mut self) -> Option<Self::Item> {
+        let Some(result_id) = self.1.pop() else {
+            return None;
+        };
+        let result_node = self.0.ax_nodes.get(&result_id).unwrap();
+        for child_id in result_node.children().iter().rev() {
+            self.1.push(*child_id);
+        }
+        Some((result_id, result_node))
+    }
+}

components/shared/embedder/Cargo.toml

@@ -18,6 +18,7 @@ baked-default-resources = []
 gamepad = []
 
 [dependencies]
+accessibility_traits = { workspace = true }
 base = { workspace = true }
 bitflags = { workspace = true }
 cookie = { workspace = true }

components/shared/embedder/lib.rs

@@ -22,6 +22,7 @@ use std::ops::Range;
 use std::path::PathBuf;
 use std::sync::Arc;
 
+use accessibility_traits::AccessibilityTree;
 use base::generic_channel::{GenericCallback, GenericSender, GenericSharedMemory, SendResult};
 use base::id::{PipelineId, WebViewId};
 use crossbeam_channel::Sender;
@@ -530,6 +531,8 @@ pub enum EmbedderMsg {
     /// Inform the embedding layer that a particular `InputEvent` was handled by Servo
     /// and the embedder can continue processing it, if necessary.
     InputEventHandled(WebViewId, InputEventId, InputEventResult),
+    /// Placeholder
+    HackyAccessibilityTreeUpdate(WebViewId, AccessibilityTree),
 }
 
 impl Debug for EmbedderMsg {

components/shared/script/Cargo.toml

@@ -16,6 +16,7 @@ bluetooth = ["bluetooth_traits"]
 webgpu = ["webgpu_traits"]
 
 [dependencies]
+accessibility_traits = { workspace = true }
 background_hang_monitor_api = { workspace = true }
 base = { workspace = true }
 bluetooth_traits = { workspace = true, optional = true }

components/shared/script/lib.rs

@@ -11,6 +11,7 @@
 
 use std::fmt;
 
+use accessibility_traits::AccessibilityTree;
 use base::cross_process_instant::CrossProcessInstant;
 use base::generic_channel::{GenericCallback, GenericReceiver, GenericSender};
 use base::id::{
@@ -305,6 +306,8 @@ pub enum ScriptThreadMessage {
     /// Release all data for the given `UserContentManagerId` from the `ScriptThread`'s
     /// `user_contents_for_manager_id` map.
     DestroyUserContentManager(UserContentManagerId),
+    /// Placeholder
+    HackySendAccessibilityTree(WebViewId, AccessibilityTree),
 }
 
 impl fmt::Debug for ScriptThreadMessage {

ports/servoshell/Cargo.toml

@@ -56,6 +56,7 @@ webgpu = ["libservo/webgpu"]
 webxr = ["libservo/webxr"]
 
 [dependencies]
+accessibility_traits = { workspace = true }
 bpaf = { version = "0.9.20", features = ["derive"] }
 cfg-if = { workspace = true }
 crossbeam-channel = { workspace = true }

ports/servoshell/desktop/app.rs

@@ -213,7 +213,7 @@ impl ApplicationHandler<AppEvent> for App {
             .and_then(|window_id| state.window(ServoShellWindowId::from(u64::from(window_id))))
         {
             if let Some(headed_window) = window.platform_window().as_headed_window() {
-                headed_window.handle_winit_app_event(app_event);
+                headed_window.handle_winit_app_event(&window, app_event);
             }
         }
 

ports/servoshell/desktop/gui.rs

@@ -7,11 +7,12 @@ use std::rc::Rc;
 use std::sync::Arc;
 
 use dpi::PhysicalSize;
+use egui::accesskit::{Role, TreeId, TreeUpdate, Uuid};
 use egui::text::{CCursor, CCursorRange};
 use egui::text_edit::TextEditState;
 use egui::{
     Button, Key, Label, LayerId, Modifiers, PaintCallback, TopBottomPanel, Vec2, WidgetInfo,
-    WidgetType, pos2,
+    WidgetType, accesskit, pos2,
 };
 use egui_glow::{CallbackFn, EguiGlow};
 use egui_winit::EventResponse;
@@ -464,6 +465,18 @@ impl Gui {
             // If the top parts of the GUI changed size, then update the size of the WebView and also
             // the size of its RenderingContext.
             let rect = ctx.available_rect();
+            let tree_id = TreeId(Uuid::from_bytes([1; 16]));
+            let id = egui::Id::new("webview");
+            ctx.accesskit_node_builder(id, |node| {
+                node.set_role(Role::Group);
+                node.set_tree_id(tree_id);
+                node.set_bounds(accesskit::Rect {
+                    x0: rect.left() as f64,
+                    y0: rect.top() as f64,
+                    x1: rect.right() as f64,
+                    y1: rect.bottom() as f64,
+                });
+            });
             let size = Size2D::new(rect.width(), rect.height()) * scale;
             if let Some(webview) = window.active_webview() &&
                 size != webview.size()
@@ -608,6 +621,12 @@ impl Gui {
     pub(crate) fn set_zoom_factor(&self, factor: f32) {
         self.context.egui_ctx.set_zoom_factor(factor);
     }
+
+    pub(crate) fn hacky_accessibility_tree_update(&mut self, updater: impl FnOnce() -> TreeUpdate) {
+        if let Some(adapter) = self.context.egui_winit.accesskit.as_mut() {
+            adapter.update_if_active(updater);
+        }
+    }
 }
 
 fn embedder_image_to_egui_image(image: &Image) -> egui::ColorImage {

ports/servoshell/desktop/headed_window.rs

@@ -13,6 +13,8 @@ use std::env;
 use std::rc::Rc;
 use std::time::Duration;
 
+use accessibility_traits::AccessibilityTree;
+use egui::accesskit::{Node, NodeId, TreeId, TreeUpdate, Uuid};
 use euclid::{Angle, Length, Point2D, Rect, Rotation3D, Scale, Size2D, UnknownUnit, Vector3D};
 use keyboard_types::ShortcutMatcher;
 use log::{debug, info};
@@ -756,8 +758,21 @@ impl HeadedWindow {
         }
     }
 
-    pub(crate) fn handle_winit_app_event(&self, app_event: AppEvent) {
+    pub(crate) fn handle_winit_app_event(&self, _window: &ServoShellWindow, app_event: AppEvent) {
         if let AppEvent::Accessibility(ref event) = app_event {
+            match &event.window_event {
+                egui_winit::accesskit_winit::WindowEvent::InitialTreeRequested => {
+                    // TODO get the initial tree from servo
+                },
+                egui_winit::accesskit_winit::WindowEvent::ActionRequested(req) => {
+                    // TODO use window to get active webview, then do something with action request.
+                    if req.target_tree != TreeId::ROOT {
+                        println!("{:?}", req);
+                    }
+                },
+                _ => {},
+            }
+
             if self
                 .gui
                 .borrow_mut()
@@ -1131,6 +1146,26 @@ impl PlatformWindow for HeadedWindow {
         println!("{message}");
         log::log!(level.into(), "{message}");
     }
+
+    fn hacky_accessibility_tree_update(
+        &self,
+        _webview: WebView,
+        accessibility_tree: AccessibilityTree,
+    ) {
+        let nodes: Vec<(NodeId, Node)> = accessibility_tree
+            .ax_nodes
+            .iter()
+            .map(|(k, v)| (*k, v.clone()))
+            .collect();
+        self.gui
+            .borrow_mut()
+            .hacky_accessibility_tree_update(|| TreeUpdate {
+                nodes,
+                tree: Some(accessibility_tree.ax_tree),
+                tree_id: TreeId(Uuid::from_bytes([1; 16])),
+                focus: NodeId(1),
+            });
+    }
 }
 
 fn winit_phase_to_touch_event_type(phase: TouchPhase) -> TouchEventType {

ports/servoshell/egl/app.rs

@@ -4,11 +4,12 @@
 use std::cell::{Cell, RefCell};
 use std::rc::Rc;
 
+use accessibility_traits::AccessibilityTree;
 use base::generic_channel::GenericCallback;
 use dpi::PhysicalSize;
 use euclid::{Rect, Scale};
 use keyboard_types::{CompositionEvent, CompositionState, Key, KeyState, NamedKey};
-use log::{info, warn};
+use log::{info, trace, warn};
 use raw_window_handle::{RawWindowHandle, WindowHandle};
 use servo::{
     DeviceIndependentIntRect, DeviceIndependentPixel, DeviceIntSize, DevicePixel, DevicePoint,

ports/servoshell/running_app_state.rs

@@ -9,6 +9,7 @@ use std::collections::HashMap;
 use std::collections::hash_map::Entry;
 use std::rc::Rc;
 
+use accessibility_traits::AccessibilityTree;
 use crossbeam_channel::{Receiver, Sender, unbounded};
 use euclid::Rect;
 use image::{DynamicImage, ImageFormat, RgbaImage};
@@ -819,6 +820,15 @@ impl WebViewDelegate for RunningAppState {
         self.platform_window_for_webview_id(webview.id())
             .show_console_message(level, &message);
     }
+
+    fn hacky_accessibility_tree_update(
+        &self,
+        webview: WebView,
+        accessibility_tree: AccessibilityTree,
+    ) {
+        self.platform_window_for_webview_id(webview.id())
+            .hacky_accessibility_tree_update(webview, accessibility_tree);
+    }
 }
 
 struct ServoShellServoDelegate;

ports/servoshell/window.rs

@@ -5,6 +5,7 @@
 use std::cell::{Cell, RefCell};
 use std::rc::Rc;
 
+use accessibility_traits::AccessibilityTree;
 use euclid::Scale;
 use log::warn;
 use servo::{
@@ -433,4 +434,6 @@ pub(crate) trait PlatformWindow {
     fn as_headed_window(&self) -> Option<&crate::egl::app::EmbeddedPlatformWindow> {
         None
     }
+
+    fn hacky_accessibility_tree_update(&self, _: WebView, _: AccessibilityTree) {}
 }