Refactor node mutation (again)

crates/egui/src/context.rs

@@ -158,19 +158,8 @@ impl ContextImpl {
     }
 
     #[cfg(feature = "accesskit")]
-    fn mutate_accesskit_node(
+    fn accesskit_node(&mut self, id: Id, parent_id: Option<Id>) -> &mut accesskit::Node {
-        &mut self,
+        let update = self.output.accesskit_update.as_mut().unwrap();
-        id: Id,
-        parent_id: Option<Id>,
-        f: impl FnOnce(&mut accesskit::Node),
-    ) {
-        let update = match &mut self.output.accesskit_update {
-            Some(update) => update,
-            None => {
-                return;
-            }
-        };
-
         let nodes = &mut update.nodes;
         let node_map = &mut self.frame_state.accesskit_nodes;
         let index = node_map.get(&id).copied().unwrap_or_else(|| {
@@ -184,7 +173,7 @@ impl ContextImpl {
             parent.children.push(accesskit_id);
             index
         });
-        f(Arc::get_mut(&mut nodes[index].1).unwrap());
+        Arc::get_mut(&mut nodes[index].1).unwrap()
     }
 }
 
@@ -495,9 +484,9 @@ 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.
-            self.mutate_accesskit_node(id, None, |node| {
+            if let Some(mut node) = self.accesskit_node(id, None) {
-                response.fill_accesskit_node_common(node);
+                response.fill_accesskit_node_common(&mut node);
-            });
+            }
         }
 
         let clicked_elsewhere = response.clicked_elsewhere();
@@ -1586,19 +1575,20 @@ impl Context {
 
 /// ## Accessibility
 impl Context {
-    /// Create an AccessKit node with the specified ID if one doesn't already
+    /// If AccessKit support is active for the current frame, get or create
-    /// exist, then call the provided function with a mutable reference
+    /// a node with the specified ID and return a mutable reference to it.
-    /// to the node. Node that the `parent_id` parameter is ignored if the node
+    /// `parent_id is ignored if the node already exists.
-    /// already exists. If AccessKit isn't active for this frame, this method
-    /// does nothing.
     #[cfg(feature = "accesskit")]
-    pub fn mutate_accesskit_node(
+    pub fn accesskit_node(
         &self,
         id: Id,
         parent_id: Option<Id>,
-        f: impl FnOnce(&mut accesskit::Node),
+    ) -> Option<RwLockWriteGuard<'_, accesskit::Node>> {
-    ) {
+        let ctx = self.write();
-        self.write().mutate_accesskit_node(id, parent_id, f);
+        ctx.output
+            .accesskit_update
+            .is_some()
+            .then(move || RwLockWriteGuard::map(ctx, |c| c.accesskit_node(id, parent_id)))
     }
 
     /// Returns whether AccessKit is active for the current frame.

crates/egui/src/response.rs

@@ -529,17 +529,17 @@ impl Response {
             self.output_event(event);
         } else {
             #[cfg(feature = "accesskit")]
-            self.ctx.mutate_accesskit_node(self.id, None, |node| {
+            if let Some(mut node) = self.ctx.accesskit_node(self.id, None) {
-                self.fill_accesskit_node_from_widget_info(node, make_info());
+                self.fill_accesskit_node_from_widget_info(&mut node, make_info());
-            });
+            }
         }
     }
 
     pub fn output_event(&self, event: crate::output::OutputEvent) {
         #[cfg(feature = "accesskit")]
-        self.ctx.mutate_accesskit_node(self.id, None, |node| {
+        if let Some(mut node) = self.ctx.accesskit_node(self.id, None) {
-            self.fill_accesskit_node_from_widget_info(node, event.widget_info().clone());
+            self.fill_accesskit_node_from_widget_info(&mut node, event.widget_info().clone());
-        });
+        }
         self.ctx.output().events.push(event);
     }
 
@@ -606,9 +606,9 @@ impl Response {
     /// Associate a label with a control for accessibility.
     pub fn labelled_by(self, id: Id) -> Self {
         #[cfg(feature = "accesskit")]
-        self.ctx.mutate_accesskit_node(self.id, None, |node| {
+        if let Some(mut node) = self.ctx.accesskit_node(self.id, None) {
             node.labelled_by.push(id.accesskit_id());
-        });
+        }
         #[cfg(not(feature = "accesskit"))]
         {
             let _ = id;

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")]
-        ui.ctx().mutate_accesskit_node(response.id, None, |node| {
+        if let Some(mut node) = ui.ctx().accesskit_node(response.id, None) {
             use accesskit::Action;
             // If either end of the range is unbounded, it's better
             // to leave the corresponding AccessKit field set to None,
@@ -585,7 +585,7 @@ impl<'a> Widget for DragValue<'a> {
                 let value_text = format!("{}{}{}", prefix, value_text, suffix);
                 node.value = Some(value_text.into());
             }
-        });
+        }
 
         response
     }

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")]
-        ui.ctx().mutate_accesskit_node(response.id, None, |node| {
+        if let Some(mut node) = ui.ctx().accesskit_node(response.id, None) {
             use accesskit::Action;
             node.min_numeric_value = Some(*self.range.start());
             node.max_numeric_value = Some(*self.range.end());
@@ -753,7 +753,7 @@ impl<'a> Slider<'a> {
             if value > *clamp_range.start() {
                 node.actions |= Action::Decrement;
             }
-        });
+        }
 
         let slider_response = response.clone();
 

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

@@ -665,7 +665,7 @@ impl<'t> TextEdit<'t> {
             let parent_id = response.id;
             for (i, row) in galley.rows.iter().enumerate() {
                 let id = parent_id.with(i);
-                ui.ctx().mutate_accesskit_node(id, Some(parent_id), |node| {
+                if let Some(mut node) = ui.ctx().accesskit_node(id, Some(parent_id)) {
                     node.role = Role::InlineTextBox;
                     let rect = row.rect.translate(text_draw_pos.to_vec2());
                     node.bounds = Some(accesskit::kurbo::Rect {
@@ -717,10 +717,10 @@ impl<'t> TextEdit<'t> {
                     node.character_positions = Some(character_positions.into());
                     node.character_widths = Some(character_widths.into());
                     node.word_lengths = word_lengths.into();
-                });
+                }
             }
 
-            ui.ctx().mutate_accesskit_node(parent_id, None, |node| {
+            if let Some(mut node) = ui.ctx().accesskit_node(parent_id, None) {
                 if let Some(cursor_range) = &cursor_range {
                     let anchor = &cursor_range.secondary.rcursor;
                     let focus = &cursor_range.primary.rcursor;
@@ -737,7 +737,7 @@ impl<'t> TextEdit<'t> {
                 }
 
                 node.default_action_verb = Some(accesskit::DefaultActionVerb::Focus);
-            });
+            }
         }
 
         TextEditOutput {