[macOS] FlutterView should not override platform view cursor

Author: knopp

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

@@ -46,6 +46,7 @@ - (FlutterCursorCoordinator*)initWithFlutterView:(FlutterView*)flutterView {
 - (void)frameCleanup {
   _cleanupScheduled = NO;
   _mouseMoveHandled = NO;
+  _flutterView.disableCursorUpdate = NO;
 }
 
 - (BOOL)cleanupScheduled {
@@ -85,6 +86,9 @@ - (void)processMouseMoveEvent:(NSEvent*)event
   // cursor rect. Unfocused NSTextField uses legacy cursor rects for changing
   // its cursor.
   [platformView.window invalidateCursorRectsForView:platformView];
+  // Prevent tracking area in FlutterViewController from updating the cursor.
+  // This will be reset in [self frameCleanup].
+  _flutterView.disableCursorUpdate = YES;
   _mouseMoveHandled = YES;
 }
 @end

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

@@ -655,6 +655,7 @@ - (void)testCoordinatorEventOutsideFlutterContent {
     OCMStub([platformViewWindow invalidateCursorRectsForView:platformView]);
     OCMStub([platformView window]).andReturn(platformViewWindow);
     OCMStub([flutterView cursorUpdate:[OCMArg any]]);
+    OCMStub([flutterView setDisableCursorUpdate:YES]);
     id mutatorView = OCMStrictClassMock([FlutterMutatorView class]);
     OCMStub([mutatorView platformView]).andReturn(platformView);
     CGPoint location = NSMakePoint(150, 150);
@@ -671,10 +672,13 @@ - (void)testCoordinatorEventOutsideFlutterContent {
     [coordinator processMouseMoveEvent:event
                         forMutatorView:mutatorView
                          overlayRegion:{CGRectMake(0, 0, 100, 100)}];
+    // Prevent trackign area from FlutterView controller from updating the cursor.
+    OCMVerify([flutterView setDisableCursorUpdate:YES]);
   }
   EXPECT_TRUE(coordinator.cleanupScheduled);
   [[NSRunLoop mainRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:0.1]];
   EXPECT_FALSE(coordinator.cleanupScheduled);
+  OCMVerify([flutterView setDisableCursorUpdate:NO]);
 
   // Check that invalidateCursorRectsForView is called again
   platformViewWindow = OCMClassMock([NSWindow class]);

shell/platform/darwin/macos/framework/Source/FlutterView.h

@@ -68,6 +68,15 @@ constexpr FlutterViewId kFlutterImplicitViewId = 0ll;
  */
 @property(readonly, nonatomic, nonnull) FlutterSurfaceManager* surfaceManager;
 
+/**
+ * Prevent FlutterView from updating the cursor inside [cursorUpdate:].
+ * It is necessary to disable cursor update when cursor is over platform view
+ * and the tracking area in FlutterViewController is created with
+ * NSTrackingActiveAlways option. Otherwise the tracking area forces the cursor
+ * update *after* the platform view has already updated the cursor.
+ */
+@property(readwrite, nonatomic) BOOL disableCursorUpdate;
+
 /**
  * By default, the `FlutterSurfaceManager` creates two layers to manage Flutter
  * content, the content layer and containing layer. To set the native background

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

@@ -21,6 +21,8 @@ @interface FlutterView () <FlutterSurfaceManagerDelegate> {
 
 @implementation FlutterView
 
+@synthesize disableCursorUpdate;
+
 - (instancetype)initWithMTLDevice:(id<MTLDevice>)device
                      commandQueue:(id<MTLCommandQueue>)commandQueue
                          delegate:(id<FlutterViewDelegate>)delegate
@@ -106,6 +108,10 @@ - (void)didUpdateMouseCursor:(NSCursor*)cursor {
 // - When context menu above FlutterView is closed. Context menu will change current cursor to arrow
 // and will not restore it back.
 - (void)cursorUpdate:(NSEvent*)event {
+  if (disableCursorUpdate) {
+    // Cursor is over a platform view, do not update cursor.
+    return;
+  }
   [_lastCursor set];
   // It is possible that there is a platform view with NSTrackingArea below flutter content.
   // This could override the mouse cursor as a result of mouse move event. There is no good way