[ios][platform_view]force reset forwarding recognizer state when its stuck

Author: hellohuanlin

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

@@ -2782,6 +2782,111 @@ - (void)testFlutterPlatformViewTouchesCancelledEventAreForcedToBeCancelled {
   flutterPlatformViewsController->Reset();
 }
 
+- (void)testFlutterPlatformViewTouchesEndedOrTouchesCancelledEventDoesNotFailTheGestureRecognizer {
+  flutter::FlutterPlatformViewsTestMockPlatformViewDelegate mock_delegate;
+
+  flutter::TaskRunners runners(/*label=*/self.name.UTF8String,
+                               /*platform=*/GetDefaultTaskRunner(),
+                               /*raster=*/GetDefaultTaskRunner(),
+                               /*ui=*/GetDefaultTaskRunner(),
+                               /*io=*/GetDefaultTaskRunner());
+  auto flutterPlatformViewsController = std::make_shared<flutter::PlatformViewsController>();
+  flutterPlatformViewsController->SetTaskRunner(GetDefaultTaskRunner());
+  auto platform_view = std::make_unique<flutter::PlatformViewIOS>(
+      /*delegate=*/mock_delegate,
+      /*rendering_api=*/mock_delegate.settings_.enable_impeller
+          ? flutter::IOSRenderingAPI::kMetal
+          : flutter::IOSRenderingAPI::kSoftware,
+      /*platform_views_controller=*/flutterPlatformViewsController,
+      /*task_runners=*/runners,
+      /*worker_task_runner=*/nil,
+      /*is_gpu_disabled_jsync_switch=*/std::make_shared<fml::SyncSwitch>());
+
+  FlutterPlatformViewsTestMockFlutterPlatformFactory* factory =
+      [[FlutterPlatformViewsTestMockFlutterPlatformFactory alloc] init];
+  flutterPlatformViewsController->RegisterViewFactory(
+      factory, @"MockFlutterPlatformView",
+      FlutterPlatformViewGestureRecognizersBlockingPolicyEager);
+  FlutterResult result = ^(id result) {
+  };
+  flutterPlatformViewsController->OnMethodCall(
+      [FlutterMethodCall
+          methodCallWithMethodName:@"create"
+                         arguments:@{@"id" : @2, @"viewType" : @"MockFlutterPlatformView"}],
+      result);
+
+  XCTAssertNotNil(gMockPlatformView);
+
+  // Find touch inteceptor view
+  UIView* touchInteceptorView = gMockPlatformView;
+  while (touchInteceptorView != nil &&
+         ![touchInteceptorView isKindOfClass:[FlutterTouchInterceptingView class]]) {
+    touchInteceptorView = touchInteceptorView.superview;
+  }
+  XCTAssertNotNil(touchInteceptorView);
+
+  // Find ForwardGestureRecognizer
+  __block UIGestureRecognizer* forwardGestureRecognizer = nil;
+  for (UIGestureRecognizer* gestureRecognizer in touchInteceptorView.gestureRecognizers) {
+    if ([gestureRecognizer isKindOfClass:NSClassFromString(@"ForwardingGestureRecognizer")]) {
+      forwardGestureRecognizer = gestureRecognizer;
+      break;
+    }
+  }
+  id flutterViewContoller = OCMClassMock([FlutterViewController class]);
+
+  flutterPlatformViewsController->SetFlutterViewController(flutterViewContoller);
+
+  NSSet* touches1 = [NSSet setWithObject:@1];
+  id event1 = OCMClassMock([UIEvent class]);
+  XCTAssert(forwardGestureRecognizer.state == UIGestureRecognizerStatePossible,
+            @"Forwarding gesture recognizer must start with possible state.");
+  [forwardGestureRecognizer touchesBegan:touches1 withEvent:event1];
+  [forwardGestureRecognizer touchesEnded:touches1 withEvent:event1];
+  XCTAssert(forwardGestureRecognizer.state == UIGestureRecognizerStateFailed,
+            @"Forwarding gesture recognizer must end with failed state.");
+
+  XCTestExpectation* touchEndedExpectation =
+      [self expectationWithDescription:@"Wait for gesture recognizer's state change."];
+  dispatch_async(dispatch_get_main_queue(), ^{
+    // Re-query forward gesture recognizer since it's recreated.
+    for (UIGestureRecognizer* gestureRecognizer in touchInteceptorView.gestureRecognizers) {
+      if ([gestureRecognizer isKindOfClass:NSClassFromString(@"ForwardingGestureRecognizer")]) {
+        forwardGestureRecognizer = gestureRecognizer;
+        break;
+      }
+    }
+    XCTAssert(forwardGestureRecognizer.state == UIGestureRecognizerStatePossible,
+              @"Forwarding gesture recognizer must be reset to possible state.");
+    [touchEndedExpectation fulfill];
+  });
+  [self waitForExpectationsWithTimeout:30 handler:nil];
+
+  XCTAssert(forwardGestureRecognizer.state == UIGestureRecognizerStatePossible,
+            @"Forwarding gesture recognizer must start with possible state.");
+  [forwardGestureRecognizer touchesBegan:touches1 withEvent:event1];
+  [forwardGestureRecognizer touchesCancelled:touches1 withEvent:event1];
+  XCTAssert(forwardGestureRecognizer.state == UIGestureRecognizerStateFailed,
+            @"Forwarding gesture recognizer must end with failed state.");
+  XCTestExpectation* touchCancelledExpectation =
+      [self expectationWithDescription:@"Wait for gesture recognizer's state change."];
+  dispatch_async(dispatch_get_main_queue(), ^{
+    // Re-query forward gesture recognizer since it's recreated.
+    for (UIGestureRecognizer* gestureRecognizer in touchInteceptorView.gestureRecognizers) {
+      if ([gestureRecognizer isKindOfClass:NSClassFromString(@"ForwardingGestureRecognizer")]) {
+        forwardGestureRecognizer = gestureRecognizer;
+        break;
+      }
+    }
+    XCTAssert(forwardGestureRecognizer.state == UIGestureRecognizerStatePossible,
+              @"Forwarding gesture recognizer must be reset to possible state.");
+    [touchCancelledExpectation fulfill];
+  });
+  [self waitForExpectationsWithTimeout:30 handler:nil];
+
+  flutterPlatformViewsController->Reset();
+}
+
 - (void)testFlutterPlatformViewControllerSubmitFrameWithoutFlutterViewNotCrashing {
   flutter::FlutterPlatformViewsTestMockPlatformViewDelegate mock_delegate;
 

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

@@ -526,7 +526,7 @@ @interface FlutterDelayingGestureRecognizer : UIGestureRecognizer <UIGestureReco
 // setting the state to `UIGestureRecognizerStateEnded`.
 @property(nonatomic) BOOL touchedEndedWithoutBlocking;
 
-@property(nonatomic, readonly) UIGestureRecognizer* forwardingRecognizer;
+@property(nonatomic) UIGestureRecognizer* forwardingRecognizer;
 
 - (instancetype)initWithTarget:(id)target
                         action:(SEL)action
@@ -547,6 +547,7 @@ @interface ForwardingGestureRecognizer : UIGestureRecognizer <UIGestureRecognize
 - (instancetype)initWithTarget:(id)target
        platformViewsController:
            (fml::WeakPtr<flutter::PlatformViewsController>)platformViewsController;
+- (ForwardingGestureRecognizer*)recreateRecognizerWithTarget:(id)target;
 @end
 
 @interface FlutterTouchInterceptingView ()
@@ -586,6 +587,20 @@ - (instancetype)initWithEmbeddedView:(UIView*)embeddedView
   return self;
 }
 
+- (void)forceResetForwardingGestureRecognizerState {
+  // When iPad pencil is involved in a finger touch gesture, the gesture is not reset to "possible"
+  // state, which causes subsequent touches to be blocked. As a workaround, we force reset the state
+  // by recreating the forwarding gesture recognizer. See:
+  // https://github.com/flutter/flutter/issues/136244
+  ForwardingGestureRecognizer* oldForwardingRecognizer =
+      (ForwardingGestureRecognizer*)self.delayingRecognizer.forwardingRecognizer;
+  ForwardingGestureRecognizer* newForwardingRecognizer =
+      [oldForwardingRecognizer recreateRecognizerWithTarget:self];
+  [self removeGestureRecognizer:oldForwardingRecognizer];
+  self.delayingRecognizer.forwardingRecognizer = newForwardingRecognizer;
+  [self addGestureRecognizer:newForwardingRecognizer];
+}
+
 - (void)releaseGesture {
   self.delayingRecognizer.state = UIGestureRecognizerStateFailed;
 }
@@ -715,6 +730,11 @@ - (instancetype)initWithTarget:(id)target
   return self;
 }
 
+- (ForwardingGestureRecognizer*)recreateRecognizerWithTarget:(id)target {
+  return [[ForwardingGestureRecognizer alloc] initWithTarget:target
+                                     platformViewsController:std::move(_platformViewsController)];
+}
+
 - (void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
   FML_DCHECK(_currentTouchPointersCount >= 0);
   if (_currentTouchPointersCount == 0) {
@@ -741,6 +761,16 @@ - (void)touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event {
   if (_currentTouchPointersCount == 0) {
     self.state = UIGestureRecognizerStateFailed;
     _flutterViewController.reset(nil);
+    __weak __typeof(self) weakSelf = self;
+    dispatch_async(dispatch_get_main_queue(), ^{
+      __strong __typeof(weakSelf) strongSelf = weakSelf;
+      if (!strongSelf) {
+        return;
+      }
+      if (strongSelf.state != UIGestureRecognizerStatePossible) {
+        [(FlutterTouchInterceptingView*)strongSelf.view forceResetForwardingGestureRecognizerState];
+      }
+    });
   }
 }
 
@@ -755,6 +785,16 @@ - (void)touchesCancelled:(NSSet*)touches withEvent:(UIEvent*)event {
   if (_currentTouchPointersCount == 0) {
     self.state = UIGestureRecognizerStateFailed;
     _flutterViewController.reset(nil);
+    __weak __typeof(self) weakSelf = self;
+    dispatch_async(dispatch_get_main_queue(), ^{
+      __strong __typeof(weakSelf) strongSelf = weakSelf;
+      if (!strongSelf) {
+        return;
+      }
+      if (strongSelf.state != UIGestureRecognizerStatePossible) {
+        [(FlutterTouchInterceptingView*)strongSelf.view forceResetForwardingGestureRecognizerState];
+      }
+    });
   }
 }