Final planned refactor: a more flexible approach to hierarchy

crates/egui/src/context.rs

@@ -111,6 +111,7 @@ impl ContextImpl {
 
         #[cfg(feature = "accesskit")]
         if self.is_accesskit_enabled {
+            use crate::frame_state::AccessKitFrameState;
             let id = crate::accesskit_root_id();
             let node = Box::new(accesskit::Node {
                 role: accesskit::Role::Window,
@@ -121,7 +122,10 @@ impl ContextImpl {
             });
             let mut nodes = IdMap::default();
             nodes.insert(id, node);
-            self.frame_state.accesskit_nodes = Some(nodes);
+            self.frame_state.accesskit_state = Some(AccessKitFrameState {
+                nodes,
+                parent_stack: vec![id],
+            });
         }
     }
 
@@ -152,8 +156,9 @@ impl ContextImpl {
     }
 
     #[cfg(feature = "accesskit")]
-    fn accesskit_node(&mut self, id: Id, parent_id: Option<Id>) -> &mut accesskit::Node {
+    fn accesskit_node(&mut self, id: Id) -> &mut accesskit::Node {
-        let nodes = self.frame_state.accesskit_nodes.as_mut().unwrap();
+        let state = self.frame_state.accesskit_state.as_mut().unwrap();
+        let nodes = &mut state.nodes;
         // We have to override clippy's map_entry lint here, because the
         // insertion path also modifies another entry, to establish
         // the parent/child relationship. Using `HashMap::entry` here
@@ -161,8 +166,8 @@ impl ContextImpl {
         #[allow(clippy::map_entry)]
         if !nodes.contains_key(&id) {
             nodes.insert(id, Default::default());
-            let parent_id = parent_id.unwrap_or_else(crate::accesskit_root_id);
+            let parent_id = state.parent_stack.last().unwrap();
-            let parent = nodes.get_mut(&parent_id).unwrap();
+            let parent = nodes.get_mut(parent_id).unwrap();
             parent.children.push(id.accesskit_id());
         }
         nodes.get_mut(&id).unwrap()
@@ -476,7 +481,7 @@ impl Context {
             // Make sure anything that can receive focus has an AccessKit node.
             // TODO(mwcampbell): For nodes that are filled from widget info,
             // some information is written to the node twice.
-            if let Some(mut node) = self.accesskit_node(id, None) {
+            if let Some(mut node) = self.accesskit_node(id) {
                 response.fill_accesskit_node_common(&mut node);
             }
         }
@@ -1038,12 +1043,13 @@ impl Context {
 
         #[cfg(feature = "accesskit")]
         {
-            let nodes = self.frame_state().accesskit_nodes.take();
+            let state = self.frame_state().accesskit_state.take();
-            if let Some(nodes) = nodes {
+            if let Some(state) = state {
                 let has_focus = self.input().raw.has_focus;
                 let root_id = crate::accesskit_root_id().accesskit_id();
                 platform_output.accesskit_update = Some(accesskit::TreeUpdate {
-                    nodes: nodes
+                    nodes: state
+                        .nodes
                         .into_iter()
                         .map(|(id, node)| (id.accesskit_id(), Arc::from(node)))
                         .collect(),
@@ -1575,20 +1581,43 @@ impl Context {
 
 /// ## Accessibility
 impl Context {
+    /// Call the provided function with the given ID pushed on the stack of
+    /// parent IDs for accessibility purposes. If the `accesskit` feature
+    /// is disabled or if AccessKit support is not active for this frame,
+    /// the function is still called, but with no other effect.
+    pub fn with_accessibility_parent(&self, id: Id, f: impl FnOnce()) {
+        #[cfg(feature = "accesskit")]
+        {
+            let mut frame_state = self.frame_state();
+            if let Some(state) = frame_state.accesskit_state.as_mut() {
+                state.parent_stack.push(id);
+            }
+        }
+        #[cfg(not(feature = "accesskit"))]
+        {
+            let _ = id;
+        }
+        f();
+        #[cfg(feature = "accesskit")]
+        {
+            let mut frame_state = self.frame_state();
+            if let Some(state) = frame_state.accesskit_state.as_mut() {
+                assert_eq!(state.parent_stack.pop(), Some(id));
+            }
+        }
+    }
+
     /// If AccessKit support is active for the current frame, get or create
     /// a node with the specified ID and return a mutable reference to it.
-    /// `parent_id` is ignored if the node already exists.
+    /// For newly crated nodes, the parent is the node with the ID at the top
+    /// of the stack managed by [`Context::with_accessibility_parent`].
     #[cfg(feature = "accesskit")]
-    pub fn accesskit_node(
+    pub fn accesskit_node(&self, id: Id) -> Option<RwLockWriteGuard<'_, accesskit::Node>> {
-        &self,
-        id: Id,
-        parent_id: Option<Id>,
-    ) -> Option<RwLockWriteGuard<'_, accesskit::Node>> {
         let ctx = self.write();
         ctx.frame_state
-            .accesskit_nodes
+            .accesskit_state
             .is_some()
-            .then(move || RwLockWriteGuard::map(ctx, |c| c.accesskit_node(id, parent_id)))
+            .then(move || RwLockWriteGuard::map(ctx, |c| c.accesskit_node(id)))
     }
 
     /// Enable generation of AccessKit tree updates in all future frames.

crates/egui/src/frame_state.rs

@@ -9,6 +9,13 @@ pub(crate) struct TooltipFrameState {
     pub count: usize,
 }
 
+#[cfg(feature = "accesskit")]
+#[derive(Clone)]
+pub(crate) struct AccessKitFrameState {
+    pub(crate) nodes: IdMap<Box<accesskit::Node>>,
+    pub(crate) parent_stack: Vec<Id>,
+}
+
 /// State that is collected during a frame and then cleared.
 /// Short-term (single frame) memory.
 #[derive(Clone)]
@@ -43,7 +50,7 @@ pub(crate) struct FrameState {
     pub(crate) scroll_target: [Option<(RangeInclusive<f32>, Option<Align>)>; 2],
 
     #[cfg(feature = "accesskit")]
-    pub(crate) accesskit_nodes: Option<IdMap<Box<accesskit::Node>>>,
+    pub(crate) accesskit_state: Option<AccessKitFrameState>,
 }
 
 impl Default for FrameState {
@@ -57,7 +64,7 @@ impl Default for FrameState {
             scroll_delta: Vec2::ZERO,
             scroll_target: [None, None],
             #[cfg(feature = "accesskit")]
-            accesskit_nodes: None,
+            accesskit_state: None,
         }
     }
 }
@@ -73,7 +80,7 @@ impl FrameState {
             scroll_delta,
             scroll_target,
             #[cfg(feature = "accesskit")]
-            accesskit_nodes,
+            accesskit_state,
         } = self;
 
         used_ids.clear();
@@ -85,7 +92,7 @@ impl FrameState {
         *scroll_target = [None, None];
         #[cfg(feature = "accesskit")]
         {
-            *accesskit_nodes = None;
+            *accesskit_state = None;
         }
     }
 

crates/egui/src/response.rs

@@ -529,7 +529,7 @@ impl Response {
             self.output_event(event);
         } else {
             #[cfg(feature = "accesskit")]
-            if let Some(mut node) = self.ctx.accesskit_node(self.id, None) {
+            if let Some(mut node) = self.ctx.accesskit_node(self.id) {
                 self.fill_accesskit_node_from_widget_info(&mut node, make_info());
             }
         }
@@ -537,7 +537,7 @@ impl Response {
 
     pub fn output_event(&self, event: crate::output::OutputEvent) {
         #[cfg(feature = "accesskit")]
-        if let Some(mut node) = self.ctx.accesskit_node(self.id, None) {
+        if let Some(mut node) = self.ctx.accesskit_node(self.id) {
             self.fill_accesskit_node_from_widget_info(&mut node, event.widget_info().clone());
         }
         self.ctx.output().events.push(event);
@@ -606,7 +606,7 @@ impl Response {
     /// Associate a label with a control for accessibility.
     pub fn labelled_by(self, id: Id) -> Self {
         #[cfg(feature = "accesskit")]
-        if let Some(mut node) = self.ctx.accesskit_node(self.id, None) {
+        if let Some(mut node) = self.ctx.accesskit_node(self.id) {
             node.labelled_by.push(id.accesskit_id());
         }
         #[cfg(not(feature = "accesskit"))]

crates/egui/src/widgets/drag_value.rs

@@ -541,7 +541,7 @@ impl<'a> Widget for DragValue<'a> {
         response.widget_info(|| WidgetInfo::drag_value(value));
 
         #[cfg(feature = "accesskit")]
-        if let Some(mut node) = ui.ctx().accesskit_node(response.id, None) {
+        if let Some(mut node) = ui.ctx().accesskit_node(response.id) {
             use accesskit::Action;
             // If either end of the range is unbounded, it's better
             // to leave the corresponding AccessKit field set to None,

crates/egui/src/widgets/slider.rs

@@ -740,7 +740,7 @@ impl<'a> Slider<'a> {
         response.widget_info(|| WidgetInfo::slider(value, self.text.text()));
 
         #[cfg(feature = "accesskit")]
-        if let Some(mut node) = ui.ctx().accesskit_node(response.id, None) {
+        if let Some(mut node) = ui.ctx().accesskit_node(response.id) {
             use accesskit::Action;
             node.min_numeric_value = Some(*self.range.start());
             node.max_numeric_value = Some(*self.range.end());

crates/egui/src/widgets/text_edit/builder.rs

@@ -659,7 +659,7 @@ impl<'t> TextEdit<'t> {
         }
 
         #[cfg(feature = "accesskit")]
-        if let Some(mut node) = ui.ctx().accesskit_node(response.id, None) {
+        if let Some(mut node) = ui.ctx().accesskit_node(response.id) {
             use accesskit::{Role, TextDirection, TextPosition, TextSelection};
 
             let parent_id = response.id;
@@ -683,9 +683,10 @@ impl<'t> TextEdit<'t> {
 
             drop(node);
 
+            ui.ctx().with_accessibility_parent(parent_id, || {
                 for (i, row) in galley.rows.iter().enumerate() {
                     let id = parent_id.with(i);
-                let mut node = ui.ctx().accesskit_node(id, Some(parent_id)).unwrap();
+                    let mut node = ui.ctx().accesskit_node(id).unwrap();
                     node.role = Role::InlineTextBox;
                     let rect = row.rect.translate(text_draw_pos.to_vec2());
                     node.bounds = Some(accesskit::kurbo::Rect {
@@ -738,6 +739,7 @@ impl<'t> TextEdit<'t> {
                     node.character_widths = Some(character_widths.into());
                     node.word_lengths = word_lengths.into();
                 }
+            });
         }
 
         TextEditOutput {