Remove duplication in dispatch_pending_point_input_events (#37426)

Follow up to:
https://github.com/servo/servo/pull/37285#pullrequestreview-2916829212,
this PR removes duplicate code.
cc: @xiaochengh

---------

Signed-off-by: batu_hoang <longvatrong111@gmail.com>

components/compositing/compositor.rs

@@ -658,6 +658,7 @@ impl IOCompositor {
                 webview_renderer.dispatch_point_input_event(
                     InputEvent::MouseButton(MouseButtonEvent::new(action, button, point))
                         .with_webdriver_message_id(message_id),
+                    false,
                 );
             },
 
@@ -671,6 +672,7 @@ impl IOCompositor {
                 webview_renderer.dispatch_point_input_event(
                     InputEvent::MouseMove(MouseMoveEvent::new(point))
                         .with_webdriver_message_id(message_id),
+                    false,
                 );
             },
 
@@ -699,6 +701,7 @@ impl IOCompositor {
                 webview_renderer.dispatch_point_input_event(
                     InputEvent::Wheel(WheelEvent::new(delta, point))
                         .with_webdriver_message_id(message_id),
+                    false,
                 );
                 webview_renderer.on_webdriver_wheel_action(scroll_delta, point);
             },

components/compositing/webview_renderer.rs

@@ -315,7 +315,14 @@ impl WebViewRenderer {
         }
     }
 
-    pub(crate) fn dispatch_point_input_event(&mut self, mut event: InputEvent) -> bool {
+    /// This function performs hit testing for point input events
+    /// before dispatching them to the constellation.
+    /// Return `true` if the event was successfully dispatched.
+    ///
+    /// We may want to retry the event if the hit test failed due to
+    /// epoch mismatch. To avoid infinite loops, we only retry once.
+    /// The `retried` parameter indicates whether the event has already been retried.
+    pub(crate) fn dispatch_point_input_event(&self, mut event: InputEvent, retried: bool) -> bool {
         // Events that do not need to do hit testing are sent directly to the
         // constellation to filter down.
         let Some(point) = event.point() else {
@@ -324,7 +331,9 @@ impl WebViewRenderer {
 
         // Delay the event if the epoch is not synchronized yet (new frame is not ready),
         // or hit test result would fail and the event is rejected anyway.
-        if !self.webrender_frame_ready.get() || !self.pending_point_input_events.borrow().is_empty()
+        if !(self.webrender_frame_ready.get() &&
+            self.pending_point_input_events.borrow().is_empty() &&
+            retried)
         {
             self.pending_point_input_events
                 .borrow_mut()
@@ -341,9 +350,12 @@ impl WebViewRenderer {
         {
             Ok(hit_test_results) => hit_test_results,
             Err(HitTestError::EpochMismatch) => {
-                self.pending_point_input_events
+                if !retried {
-                    .borrow_mut()
+                    self.pending_point_input_events
-                    .push_back(event);
+                        .borrow_mut()
+                        .push_back(event);
+                }
+
                 return false;
             },
             _ => {
@@ -371,42 +383,21 @@ impl WebViewRenderer {
         }
     }
 
-    // TODO: This function duplicates a lot of `dispatch_point_input_event.
-    // Perhaps it should just be called here instead.
     pub(crate) fn dispatch_pending_point_input_events(&self) {
-        while let Some(mut event) = self.pending_point_input_events.borrow_mut().pop_front() {
+        loop {
-            // Events that do not need to do hit testing are sent directly to the
+            let event = {
-            // constellation to filter down.
+                let mut pending = self.pending_point_input_events.borrow_mut();
-            let Some(point) = event.point() else {
+                pending.pop_front()
-                continue;
             };
 
-            // If we can't find a pipeline to send this event to, we cannot continue.
+            let event = match event {
-            let get_pipeline_details = |pipeline_id| self.pipelines.get(&pipeline_id);
+                Some(ev) => ev,
-            let Ok(result) = self
+                None => break,
-                .global
+            };
-                .borrow()
+            // We don't need to process more if 1 event failed to dispatch.
-                .hit_test_at_point(point, get_pipeline_details)
+            // All events are point events
-            else {
+            if !self.dispatch_point_input_event(event, true) {
-                // Don't need to process pending input events in this frame any more.
-                // TODO: Add multiple retry later if needed.
                 return;
-            };
-
-            match event {
-                InputEvent::Touch(ref mut touch_event) => {
-                    touch_event.init_sequence_id(self.touch_handler.current_sequence_id);
-                },
-                InputEvent::MouseButton(_) | InputEvent::MouseMove(_) | InputEvent::Wheel(_) => {
-                    self.global.borrow_mut().update_cursor(point, &result);
-                },
-                _ => unreachable!("Unexpected input event type: {event:?}"),
-            }
-
-            if let Err(error) = self.global.borrow().constellation_sender.send(
-                EmbedderToConstellationMessage::ForwardInputEvent(self.id, event, Some(result)),
-            ) {
-                warn!("Sending event to constellation failed ({error:?}).");
             }
         }
     }
@@ -477,11 +468,11 @@ impl WebViewRenderer {
             }
         }
 
-        self.dispatch_point_input_event(event);
+        self.dispatch_point_input_event(event, false);
     }
 
     fn send_touch_event(&mut self, event: TouchEvent) -> bool {
-        self.dispatch_point_input_event(InputEvent::Touch(event))
+        self.dispatch_point_input_event(InputEvent::Touch(event), false)
     }
 
     pub(crate) fn on_touch_event(&mut self, event: TouchEvent) {
@@ -745,17 +736,19 @@ impl WebViewRenderer {
     /// <http://w3c.github.io/touch-events/#mouse-events>
     fn simulate_mouse_click(&mut self, point: DevicePoint) {
         let button = MouseButton::Left;
-        self.dispatch_point_input_event(InputEvent::MouseMove(MouseMoveEvent::new(point)));
+        self.dispatch_point_input_event(InputEvent::MouseMove(MouseMoveEvent::new(point)), false);
-        self.dispatch_point_input_event(InputEvent::MouseButton(MouseButtonEvent::new(
+        self.dispatch_point_input_event(
-            MouseButtonAction::Down,
+            InputEvent::MouseButton(MouseButtonEvent::new(
-            button,
+                MouseButtonAction::Down,
-            point,
+                button,
-        )));
+                point,
-        self.dispatch_point_input_event(InputEvent::MouseButton(MouseButtonEvent::new(
+            )),
-            MouseButtonAction::Up,
+            false,
-            button,
+        );
-            point,
+        self.dispatch_point_input_event(
-        )));
+            InputEvent::MouseButton(MouseButtonEvent::new(MouseButtonAction::Up, button, point)),
+            false,
+        );
     }
 
     pub(crate) fn notify_scroll_event(