Refactor lazy activation

crates/eframe/src/native/epi_integration.rs

@@ -272,8 +272,17 @@ impl EpiIntegration {
         window: &winit::window::Window,
         event_loop_proxy: winit::event_loop::EventLoopProxy<E>,
     ) {
+        let egui_ctx = self.egui_ctx.clone();
         self.egui_winit
-            .init_accesskit(window, event_loop_proxy, self.egui_ctx.clone());
+            .init_accesskit(window, event_loop_proxy, move || {
+                // This function is called when an accessibility client
+                // (e.g. screen reader) makes its first request. If we got here,
+                // we know that an accessibility tree is actually wanted.
+                egui_ctx.enable_accesskit();
+                // Enqueue a repaint so we'll receive a full tree update soon.
+                egui_ctx.request_repaint();
+                egui::accesskit_placeholder_tree_update()
+            });
     }
 
     pub fn warm_up(&mut self, app: &mut dyn epi::App, window: &winit::window::Window) {

crates/egui-winit/src/lib.rs

@@ -132,21 +132,11 @@ impl State {
         &mut self,
         window: &winit::window::Window,
         event_loop_proxy: winit::event_loop::EventLoopProxy<T>,
-        egui_ctx: egui::Context,
+        initial_tree_update_factory: impl 'static + FnOnce() -> accesskit::TreeUpdate + Send,
     ) {
         self.accesskit = Some(accesskit_winit::Adapter::new(
             window,
-            move || {
-                // This function is called when an accessibility client
-                // (e.g. screen reader) makes its first request. If we got here,
-                // we know that an accessibility tree is actually wanted.
-                // Tell egui that AccessKit is active, and return a placeholder
-                // tree for now. `egui::Context::accesskit_activated`
-                // will request a repaint, and that will provide the first
-                // real accessibility tree.
-                egui_ctx.accesskit_activated();
-                egui::accesskit_placeholder_tree_update()
-            },
+            initial_tree_update_factory,
             event_loop_proxy,
         ));
     }

crates/egui/src/context.rs

@@ -69,7 +69,7 @@ struct ContextImpl {
     layer_rects_prev_frame: ahash::HashMap<LayerId, Vec<(Id, Rect)>>,
 
     #[cfg(feature = "accesskit")]
-    was_accesskit_activated: bool,
+    is_accesskit_enabled: bool,
 }
 
 impl ContextImpl {
@@ -110,7 +110,7 @@ impl ContextImpl {
         );
 
         #[cfg(feature = "accesskit")]
-        if self.was_accesskit_activated {
+        if self.is_accesskit_enabled {
             assert!(self.output.accesskit_update.is_none());
             let id = crate::accesskit_root_id();
             let accesskit_id = id.accesskit_id();
@@ -1607,20 +1607,18 @@ impl Context {
         self.output().accesskit_update.is_some()
     }
 
-    /// Indicates that AccessKit has been activated and egui should generate
-    /// AccessKit tree updates for all subsequent frames. Also requests a repaint
-    /// so a full AccessKit tree will be available as soon as the repaint
-    /// is done. As soon as the egui integration knows that accessibility support
-    /// is desired, it must call this method and provide a placeholder tree
-    /// to AccessKit through the [`crate::accesskit_placeholder_tree_update`] method.
+    /// Enable generation of AccessKit tree updates in all future frames.
+    ///
+    /// If it's practical for the egui integration to immediately run the egui
+    /// application when it is either initializing the AccessKit adapter or
+    /// being called by the AccessKit adapter to provide the initial tree update,
+    /// then it should do so, to provide a complete AccessKit tree to the adapter
+    /// immediately. Otherwise, it should enqueue a repaint and use the
+    /// placeholder tree update from [`crate::accesskit_placeholder_tree_update`]
+    /// in the meantime.
     #[cfg(feature = "accesskit")]
-    pub fn accesskit_activated(&self) {
-        let mut ctx = self.write();
-        if !ctx.was_accesskit_activated {
-            ctx.was_accesskit_activated = true;
-            drop(ctx);
-            self.request_repaint();
-        }
+    pub fn enable_accesskit(&self) {
+        self.write().is_accesskit_enabled = true;
     }
 }
 

crates/egui/src/lib.rs

@@ -559,8 +559,8 @@ pub fn accesskit_root_id() -> Id {
 }
 
 /// Return a tree update that the egui integration should provide to the
-/// AccessKit adapter before a real tree update is available. See also
-/// [`crate::Context::accesskit_activated`].
+/// AccessKit adapter if it cannot immediately run the egui application
+/// to get a full tree update after running [`Context::enable_accesskit`].
 #[cfg(feature = "accesskit")]
 pub fn accesskit_placeholder_tree_update() -> accesskit::TreeUpdate {
     use accesskit::{Node, Role, Tree, TreeUpdate};