Remove last_accesskit_update and add on_accesskit_update hook

crates/egui_kittest/src/lib.rs

@@ -89,7 +89,6 @@ pub struct Harness<'a, State: 'static = ()> {
     plugins: Vec<Box<dyn Plugin<State>>>,
     entry_location: Option<&'static std::panic::Location<'static>>,
     consumed_event_locations: Vec<&'static std::panic::Location<'static>>,
-    last_accesskit_update: Option<egui::accesskit::TreeUpdate>,
 
     #[cfg(feature = "snapshot")]
     default_snapshot_options: SnapshotOptions,
@@ -168,7 +167,7 @@ impl<'a, State: 'static> Harness<'a, State> {
             app,
             ctx,
             input,
-            kittest: kittest::State::new(initial_accesskit.clone()),
+            kittest: kittest::State::new(initial_accesskit),
             output,
             response,
             state,
@@ -181,7 +180,6 @@ impl<'a, State: 'static> Harness<'a, State> {
             plugins,
             entry_location: None,
             consumed_event_locations: Vec::new(),
-            last_accesskit_update: Some(initial_accesskit),
 
             #[cfg(feature = "snapshot")]
             default_snapshot_options,
@@ -247,12 +245,6 @@ impl<'a, State: 'static> Harness<'a, State> {
         self._step_inner(false);
     }
 
-    /// The most recent AccessKit tree update, if any. Useful for plugins that mirror
-    /// the accessibility tree to an external debugger.
-    pub fn accesskit_tree_update(&self) -> Option<&egui::accesskit::TreeUpdate> {
-        self.last_accesskit_update.as_ref()
-    }
-
     /// [`std::panic::Location`] of the most recent public `#[track_caller]` entry point
     /// (e.g. the caller of `step()` / `run()`), or `None` if no such call has been made yet.
     pub fn entry_location(&self) -> Option<&'static std::panic::Location<'static>> {
@@ -378,7 +370,7 @@ impl<'a, State: 'static> Harness<'a, State> {
             .accesskit_update
             .take()
             .expect("AccessKit was disabled");
-        self.last_accesskit_update = Some(accesskit_update.clone());
+        self.dispatch(|p, h| p.on_accesskit_update(h, &accesskit_update));
         self.kittest.update(accesskit_update);
         self.renderer.handle_delta(&output.textures_delta);
         self.output = output;

crates/egui_kittest/src/plugin.rs

@@ -36,7 +36,7 @@ use crate::{ExceededMaxStepsError, Harness};
 /// Plugin hooks receive `&mut Harness`. Calling [`Harness::step`] / [`Harness::run`] /
 /// etc. from inside a hook will recurse infinitely through your own `after_step`. If
 /// a plugin needs to advance the harness from inside a hook — e.g. an inspector that
-/// blocks on user input — use [`Harness::advance_frame`] instead.
+/// blocks on user input — use [`Harness::step_no_side_effects`] instead.
 #[expect(unused_variables, reason = "default no-op impls")]
 pub trait Plugin<State = ()>: Send + Any {
     /// Called once at the start of every `run()` / `try_run()` / `try_run_realtime()` /
@@ -58,6 +58,18 @@ pub trait Plugin<State = ()>: Send + Any {
     /// Called immediately after each single-frame step.
     fn after_step(&mut self, harness: &mut Harness<'_, State>) {}
 
+    /// Called after each single-frame step with the AccessKit tree update egui produced
+    /// for that frame, before it's applied to the internal kittest state.
+    ///
+    /// Plugins that need the tree (e.g. to stream it to an external debugger) should
+    /// clone it here — the harness no longer retains it after this hook returns.
+    fn on_accesskit_update(
+        &mut self,
+        harness: &mut Harness<'_, State>,
+        tree: &egui::accesskit::TreeUpdate,
+    ) {
+    }
+
     /// Called after a queued event has been pushed into the harness input, before the
     /// frame runs that consumes it.
     fn on_event(&mut self, harness: &mut Harness<'_, State>, event: &egui::Event) {}

crates/egui_kittest/tests/plugin.rs

@@ -119,20 +119,20 @@ fn on_event_fires_per_event() {
     assert_eq!(events, 2, "expected 2 on_event calls, got log: {log:?}");
 }
 
-/// `advance_frame` does NOT fire `before_step`/`after_step`.
+/// `step_no_side_effects` does NOT fire `before_step`/`after_step`.
 #[test]
-fn advance_frame_skips_hooks() {
+fn step_no_side_effects_skips_hooks() {
     struct DrivingPlugin {
         log: Log,
         drove: bool,
     }
-    impl<S> Plugin<S> for DrivingPlugin {
+    impl<S: 'static> Plugin<S> for DrivingPlugin {
         fn after_step(&mut self, h: &mut Harness<'_, S>) {
             self.log.lock().unwrap().push("after_step".into());
             if !self.drove {
                 self.drove = true;
-                // Call advance_frame from inside a hook — must not recurse.
-                h.advance_frame();
+                // Call step_no_side_effects from inside a hook — must not recurse.
+                h.step_no_side_effects();
             }
         }
     }
@@ -152,7 +152,7 @@ fn advance_frame_skips_hooks() {
 
     let log = log.lock().unwrap();
     // Exactly one after_step from the user's step(), plus any from construction-time run_ok
-    // (cleared above). advance_frame must NOT have produced another after_step.
+    // (cleared above). step_no_side_effects must NOT have produced another after_step.
     assert_eq!(log.iter().filter(|s| s == &"after_step").count(), 1);
 }