Better handling of touch events

Author: gmacmaster

vnext/Microsoft.ReactNative/Fabric/Composition/CompositionEventHandler.cpp

@@ -1189,7 +1189,7 @@ void CompositionEventHandler::onPointerPressed(
     // A previous pointer with this ID was never properly released (e.g., app lost focus,
     // pointer left window). Cancel the stale touch and clean it up so the new press can proceed.
     if (staleTouch->second.eventEmitter) {
-      DispatchTouchEvent(TouchEventType::Cancel, pointerId, pointerPoint, keyModifiers);
+      DispatchSynthesizedTouchCancelForActiveTouch(staleTouch->second, pointerPoint, keyModifiers);
     }
     m_activeTouches.erase(staleTouch);
   }
@@ -1295,7 +1295,7 @@ void CompositionEventHandler::onPointerReleased(
 
     if (tag == -1) {
       if (activeTouch->second.eventEmitter) {
-        DispatchTouchEvent(TouchEventType::Cancel, pointerId, pointerPoint, keyModifiers);
+        DispatchSynthesizedTouchCancelForActiveTouch(activeTouch->second, pointerPoint, keyModifiers);
       }
       m_activeTouches.erase(pointerId);
       return;
@@ -1471,6 +1471,47 @@ facebook::react::PointerEvent CompositionEventHandler::CreatePointerEventFromAct
   return event;
 }
 
+void CompositionEventHandler::DispatchSynthesizedTouchCancelForActiveTouch(
+    const ActiveTouch &cancelledTouch,
+    const winrt::Microsoft::ReactNative::Composition::Input::PointerPoint &pointerPoint,
+    winrt::Windows::System::VirtualKeyModifiers keyModifiers) {
+  if (!cancelledTouch.eventEmitter) {
+    return;
+  }
+
+  facebook::react::PointerEvent pointerEvent =
+      CreatePointerEventFromActiveTouch(cancelledTouch, TouchEventType::Cancel);
+  winrt::Microsoft::ReactNative::ComponentView targetView{nullptr};
+  facebook::react::SharedTouchEventEmitter emitter = cancelledTouch.eventEmitter;
+  auto pointerHandler = [emitter, pointerEvent](std::vector<winrt::Microsoft::ReactNative::ComponentView> &) {
+    emitter->onPointerCancel(pointerEvent);
+  };
+  HandleIncomingPointerEvent(pointerEvent, targetView, pointerPoint, keyModifiers, pointerHandler);
+
+  facebook::react::TouchEvent touchEvent;
+  touchEvent.changedTouches.insert(cancelledTouch.touch);
+
+  for (const auto &pair : m_activeTouches) {
+    if (!pair.second.eventEmitter || pair.second.eventEmitter != cancelledTouch.eventEmitter) {
+      continue;
+    }
+
+    if (touchEvent.changedTouches.find(pair.second.touch) != touchEvent.changedTouches.end()) {
+      continue;
+    }
+
+    touchEvent.touches.insert(pair.second.touch);
+  }
+
+  for (const auto &pair : m_activeTouches) {
+    if (pair.second.eventEmitter == cancelledTouch.eventEmitter) {
+      touchEvent.targetTouches.insert(pair.second.touch);
+    }
+  }
+
+  cancelledTouch.eventEmitter->onTouchCancel(touchEvent);
+}
+
 // If we have events that include multiple pointer updates, we should change arg from pointerId to vector<pointerId>
 void CompositionEventHandler::DispatchTouchEvent(
     TouchEventType eventType,

vnext/Microsoft.ReactNative/Fabric/Composition/CompositionEventHandler.h

@@ -149,6 +149,11 @@ class CompositionEventHandler : public std::enable_shared_from_this<CompositionE
   static void
   UpdateActiveTouch(ActiveTouch &activeTouch, facebook::react::Point ptScaled, facebook::react::Point ptLocal) noexcept;
 
+  void DispatchSynthesizedTouchCancelForActiveTouch(
+      const ActiveTouch &cancelledTouch,
+      const winrt::Microsoft::ReactNative::Composition::Input::PointerPoint &pointerPoint,
+      winrt::Windows::System::VirtualKeyModifiers keyModifiers);
+
   void UpdateCursor() noexcept;
   void SetCursor(facebook::react::Cursor cursor, HCURSOR hcur) noexcept;