Fix iOS platform view's mask view blocking touch events. (flutter#21286)

Author: Chris Yang

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

@@ -90,6 +90,15 @@ - (instancetype)initWithFrame:(CGRect)frame {
   return self;
 }
 
+// In some scenarios, when we add this view as a maskView of the ChildClippingView, iOS added
+// this view as a subview of the ChildClippingView.
+// This results this view blocking touch events on the ChildClippingView.
+// So we should always ignore any touch events sent to this view.
+// See https://github.com/flutter/flutter/issues/66044
+- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent*)event {
+  return NO;
+}
+
 - (void)drawRect:(CGRect)rect {
   CGContextRef context = UIGraphicsGetCurrentContext();
   CGContextSaveGState(context);

testing/scenario_app/ios/Scenarios/Scenarios/AppDelegate.m

@@ -23,7 +23,9 @@ @implementation AppDelegate
 - (BOOL)application:(UIApplication*)application
     didFinishLaunchingWithOptions:(NSDictionary*)launchOptions {
   self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
-
+  if ([[[NSProcessInfo processInfo] arguments] containsObject:@"--maskview-blocking"]) {
+    self.window.tintColor = UIColor.systemPinkColor;
+  }
   NSDictionary<NSString*, NSString*>* launchArgsMap = @{
     // The Platform view golden test args should match `PlatformViewGoldenTestManager`.
     @"--locale-initialization" : @"locale_initialization",
@@ -58,7 +60,6 @@ - (BOOL)application:(UIApplication*)application
           *stop = YES;
         }
       }];
-
   if (flutterViewControllerTestName) {
     [self setupFlutterViewControllerTest:flutterViewControllerTestName];
   } else if ([[[NSProcessInfo processInfo] arguments] containsObject:@"--screen-before-flutter"]) {

testing/scenario_app/ios/Scenarios/ScenariosUITests/PlatformViewGestureRecognizerTests.m

@@ -110,9 +110,54 @@ - (void)testAccept {
       [[XCTNSPredicateExpectation alloc] initWithPredicate:predicate object:platformView];
 
   [platformView tap];
+
+  [self waitForExpectations:@[ expection ] timeout:kSecondsToWaitForPlatformView];
+  XCTAssertEqualObjects(platformView.label,
+                        @"-gestureTouchesBegan-gestureTouchesEnded-platformViewTapped");
+}
+
+- (void)testGestureWithMaskViewBlockingPlatformView {
+  XCUIApplication* app = [[XCUIApplication alloc] init];
+  app.launchArguments = @[ @"--gesture-accept", @"--maskview-blocking" ];
+  [app launch];
+
+  NSPredicate* predicateToFindPlatformView =
+      [NSPredicate predicateWithBlock:^BOOL(id _Nullable evaluatedObject,
+                                            NSDictionary<NSString*, id>* _Nullable bindings) {
+        XCUIElement* element = evaluatedObject;
+        return [element.identifier hasPrefix:@"platform_view"];
+      }];
+  XCUIElement* platformView = [app.textViews elementMatchingPredicate:predicateToFindPlatformView];
+  if (![platformView waitForExistenceWithTimeout:kSecondsToWaitForPlatformView]) {
+    NSLog(@"%@", app.debugDescription);
+    XCTFail(@"Failed due to not able to find any platformView with %@ seconds",
+            @(kSecondsToWaitForPlatformView));
+  }
+
+  XCTAssertNotNil(platformView);
+  XCTAssertEqualObjects(platformView.label, @"");
+
+  NSPredicate* predicate = [NSPredicate
+      predicateWithFormat:@"label == %@",
+                          @"-gestureTouchesBegan-gestureTouchesEnded-platformViewTapped"];
+  XCTNSPredicateExpectation* expection =
+      [[XCTNSPredicateExpectation alloc] initWithPredicate:predicate object:platformView];
+
+  XCUICoordinate* coordinate =
+      [self getNormalizedCoordinate:app
+                              point:CGVectorMake(platformView.frame.origin.x + 10,
+                                                 platformView.frame.origin.y + 10)];
+  [coordinate tap];
+
   [self waitForExpectations:@[ expection ] timeout:kSecondsToWaitForPlatformView];
   XCTAssertEqualObjects(platformView.label,
                         @"-gestureTouchesBegan-gestureTouchesEnded-platformViewTapped");
 }
 
+- (XCUICoordinate*)getNormalizedCoordinate:(XCUIApplication*)app point:(CGVector)vector {
+  XCUICoordinate* appZero = [app coordinateWithNormalizedOffset:CGVectorMake(0, 0)];
+  XCUICoordinate* coordinate = [appZero coordinateWithOffset:vector];
+  return coordinate;
+}
+
 @end

testing/scenario_app/lib/src/platform_view.dart

@@ -336,9 +336,9 @@ class MultiPlatformViewBackgroundForegroundScenario extends Scenario with _BaseP
   MultiPlatformViewBackgroundForegroundScenario(Window window, {this.firstId, this.secondId})
       : assert(window != null),
         super(window) {
+    _nextFrame = _firstFrame;
     createPlatformView(window, 'platform view 1', firstId);
     createPlatformView(window, 'platform view 2', secondId);
-    _nextFrame = _firstFrame;
   }
 
   /// The platform view identifier to use for the first platform view.
@@ -532,6 +532,8 @@ class PlatformViewForTouchIOSScenario extends Scenario
 
   int _viewId;
   bool _accept;
+
+  VoidCallback _nextFrame;
   /// Creates the PlatformView scenario.
   ///
   /// The [window] parameter must not be null.
@@ -545,14 +547,24 @@ class PlatformViewForTouchIOSScenario extends Scenario
     } else {
       createPlatformView(window, text, id);
     }
+    _nextFrame = _firstFrame;
   }
 
   @override
   void onBeginFrame(Duration duration) {
-    final SceneBuilder builder = SceneBuilder();
+    _nextFrame();
+  }
 
-    builder.pushOffset(0, 0);
-    finishBuilderByAddingPlatformViewAndPicture(builder, _viewId);
+  @override
+  void onDrawFrame() {
+    // Some iOS gesture recognizers bugs are introduced in the second frame (with a different platform view rect) after laying out the platform view.
+    // So in this test, we load 2 frames to ensure that we cover those cases.
+    // See https://github.com/flutter/flutter/issues/66044
+    if (_nextFrame == _firstFrame) {
+      _nextFrame = _secondFrame;
+      window.scheduleFrame();
+    }
+    super.onDrawFrame();
   }
 
   @override
@@ -585,6 +597,20 @@ class PlatformViewForTouchIOSScenario extends Scenario
     }
 
   }
+
+  void _firstFrame() {
+    final SceneBuilder builder = SceneBuilder();
+
+    builder.pushOffset(0, 0);
+    finishBuilderByAddingPlatformViewAndPicture(builder, _viewId);
+  }
+
+  void _secondFrame() {
+    final SceneBuilder builder = SceneBuilder();
+
+    builder.pushOffset(5, 5);
+    finishBuilderByAddingPlatformViewAndPicture(builder, _viewId);
+  }
 }
 
 mixin _BasePlatformViewScenarioMixin on Scenario {