Synthesize a mouse moved event in the previous position after painting a scene

This ensures that we correctly update the hover state of elements whose position has changed relative to the mouse cursor even though the mouse hasn't actually moved.

Co-Authored-By: Antonio Scandurra <me@as-cii.com>
Co-Authored-By: Max Brunsfeld <maxbrunsfeld@gmail.com>

gpui/src/app.rs

@@ -584,6 +584,11 @@ impl MutableAppContext {
         );
     }
 
+    pub(crate) fn notify_view(&mut self, window_id: usize, view_id: usize) {
+        self.pending_effects
+            .push_back(Effect::ViewNotification { window_id, view_id });
+    }
+
     pub fn dispatch_action<T: 'static + Any>(
         &mut self,
         window_id: usize,
@@ -594,7 +599,7 @@ impl MutableAppContext {
         self.dispatch_action_any(window_id, &responder_chain, name, Box::new(arg).as_ref());
     }
 
-    fn dispatch_action_any(
+    pub(crate) fn dispatch_action_any(
         &mut self,
         window_id: usize,
         path: &[usize],
@@ -787,23 +792,7 @@ impl MutableAppContext {
                         }
                     }
 
-                    let (actions, invalidated_views) =
-                        presenter.borrow_mut().dispatch_event(event, ctx.as_ref());
-
-                    ctx.window_invalidations
-                        .entry(window_id)
-                        .or_default()
-                        .updated
-                        .extend(invalidated_views.into_iter());
-
-                    for action in actions {
-                        ctx.dispatch_action_any(
-                            window_id,
-                            &action.path,
-                            action.name,
-                            action.arg.as_ref(),
-                        );
-                    }
+                    presenter.borrow_mut().dispatch_event(event, ctx);
                 })
             }));
         }
@@ -924,11 +913,14 @@ impl MutableAppContext {
                         self.focus(window_id, view_id);
                     }
                 }
+
+                if self.pending_effects.is_empty() {
+                    self.remove_dropped_entities();
+                    self.update_windows();
+                }
             }
 
             self.flushing_effects = false;
-            self.remove_dropped_entities();
-            self.update_windows();
         }
     }
 
@@ -1850,12 +1842,7 @@ impl<'a, T: View> ViewContext<'a, T> {
     }
 
     pub fn notify(&mut self) {
-        self.app
-            .pending_effects
-            .push_back(Effect::ViewNotification {
-                window_id: self.window_id,
-                view_id: self.view_id,
-            });
+        self.app.notify_view(self.window_id, self.view_id);
     }
 
     pub fn propagate_action(&mut self) {

gpui/src/platform/event.rs

@@ -1,6 +1,6 @@
 use crate::{geometry::vector::Vector2F, keymap::Keystroke};
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub enum Event {
     KeyDown {
         keystroke: Keystroke,

gpui/src/presenter.rs

@@ -22,6 +22,7 @@ pub struct Presenter {
     font_cache: Arc<FontCache>,
     text_layout_cache: TextLayoutCache,
     asset_cache: Arc<AssetCache>,
+    last_mouse_moved_event: Option<Event>,
 }
 
 impl Presenter {
@@ -39,6 +40,7 @@ impl Presenter {
             font_cache,
             text_layout_cache,
             asset_cache,
+            last_mouse_moved_event: None,
         }
     }
 
@@ -84,6 +86,10 @@ impl Presenter {
             };
             ctx.paint(root_view_id, Vector2F::zero());
             self.text_layout_cache.finish_frame();
+
+            if let Some(event) = self.last_mouse_moved_event.clone() {
+                self.dispatch_event(event, app)
+            }
         } else {
             log::error!("could not find root_view_id for window {}", self.window_id);
         }
@@ -118,12 +124,12 @@ impl Presenter {
         }
     }
 
-    pub fn dispatch_event(
-        &mut self,
-        event: Event,
-        app: &AppContext,
-    ) -> (Vec<ActionToDispatch>, HashSet<usize>) {
+    pub fn dispatch_event(&mut self, event: Event, app: &mut MutableAppContext) {
         if let Some(root_view_id) = app.root_view_id(self.window_id) {
+            if matches!(event, Event::MouseMoved { .. }) {
+                self.last_mouse_moved_event = Some(event.clone());
+            }
+
             let mut ctx = EventContext {
                 rendered_views: &mut self.rendered_views,
                 actions: Default::default(),
@@ -131,12 +137,24 @@ impl Presenter {
                 text_layout_cache: &self.text_layout_cache,
                 view_stack: Default::default(),
                 invalidated_views: Default::default(),
-                app,
+                app: app.as_ref(),
             };
             ctx.dispatch_event(root_view_id, &event);
-            (ctx.actions, ctx.invalidated_views)
-        } else {
-            Default::default()
+
+            let invalidated_views = ctx.invalidated_views;
+            let actions = ctx.actions;
+
+            for view_id in invalidated_views {
+                app.notify_view(self.window_id, view_id);
+            }
+            for action in actions {
+                app.dispatch_action_any(
+                    self.window_id,
+                    &action.path,
+                    action.name,
+                    action.arg.as_ref(),
+                );
+            }
         }
     }