Consistent behavior across platforms

Pin iOS pan/zoom origin
Set iOS pan/zoom to seperate device ID
Use seperate device ID for mac pointer and pan/zoom
Fix missing comment in fl_engine.cc

Author: moffatman

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -1749,8 +1749,13 @@ - (void)panEvent:(UIPanGestureRecognizer*)recognizer API_AVAILABLE(ios(13.4)) {
   translation.x *= scale;
   translation.y *= scale;
 
+  CGPoint location = [recognizer locationInView:self.view];
+
   flutter::PointerData pointer_data = [self generatePointerDataForMouse];
   pointer_data.kind = flutter::PointerData::DeviceKind::kTouch;
+  pointer_data.physical_x = location.x * scale;
+  pointer_data.physical_y = location.y * scale;
+  pointer_data.device = reinterpret_cast<int64_t>(recognizer);
   if (recognizer.state == UIGestureRecognizerStateBegan) {
     pointer_data.change = flutter::PointerData::Change::kPanZoomStart;
   } else if (recognizer.state == UIGestureRecognizerStateChanged) {

shell/platform/darwin/macos/framework/Source/FlutterViewController.mm

@@ -32,6 +32,11 @@
     @"NSApplicationDidChangeAccessibilityEnhancedUserInterfaceNotification";
 static NSString* const EnhancedUserInterfaceKey = @"AXEnhancedUserInterface";
 
+// Use different device ID for mouse and pan/zoom events, since we can't differentiate the actual
+// device (mouse v.s. trackpad)
+static constexpr int32_t kMousePointerDeviceId = 0;
+static constexpr int32_t kPointerPanZoomDeviceId = 1;
+
 /**
  * State tracking for mouse events, to adapt between the events coming from the system and the
  * events that the embedding API expects.
@@ -612,15 +617,18 @@ - (void)dispatchMouseEvent:(NSEvent*)event phase:(FlutterPointerPhase)phase {
       .timestamp = static_cast<size_t>(event.timestamp * USEC_PER_SEC),
       .x = locationInBackingCoordinates.x,
       .y = -locationInBackingCoordinates.y,  // convertPointToBacking makes this negative.
+      .device = kMousePointerDeviceId,
       .device_kind = kFlutterPointerDeviceKindMouse,
       // If a click triggered a synthesized kAdd, don't pass the buttons in that event.
       .buttons = phase == kAdd ? 0 : _mouseState.buttons,
   };
 
   if (phase == kPanZoomStart) {
     flutterEvent.device_kind = kFlutterPointerDeviceKindTouch;
+    flutterEvent.device = kPointerPanZoomDeviceId;
   } else if (phase == kPanZoomUpdate) {
     flutterEvent.device_kind = kFlutterPointerDeviceKindTouch;
+    flutterEvent.device = kPointerPanZoomDeviceId;
     if (event.type == NSEventTypeScrollWheel) {
       _mouseState.deltaX += event.scrollingDeltaX * self.flutterView.layer.contentsScale;
       _mouseState.deltaY += event.scrollingDeltaY * self.flutterView.layer.contentsScale;
@@ -636,6 +644,7 @@ - (void)dispatchMouseEvent:(NSEvent*)event phase:(FlutterPointerPhase)phase {
     flutterEvent.rotation = _mouseState.rotation;
   } else if (phase == kPanZoomEnd) {
     flutterEvent.device_kind = kFlutterPointerDeviceKindTouch;
+    flutterEvent.device = kPointerPanZoomDeviceId;
     _mouseState.GestureReset();
   } else if (event.type == NSEventTypeScrollWheel) {
     flutterEvent.signal_kind = kFlutterPointerSignalKindScroll;

shell/platform/linux/fl_engine.cc

@@ -24,7 +24,8 @@
 // Unique number associated with platform tasks.
 static constexpr size_t kPlatformTaskRunnerIdentifier = 1;
 
-//
+// Use different device ID for mouse and pan/zoom events, since we can't
+// differentiate the actual device (mouse v.s. trackpad)
 static constexpr int32_t kMousePointerDeviceId = 0;
 static constexpr int32_t kPointerPanZoomDeviceId = 1;