Platform_views gesture: let flutter view controller be the media to pass the touches. (#8685)

This PR updated the forwarding gesture recognizer to pass the touch events directly to the FlutterViewContoller instead of FlutterView which ensures the touches events are passed to the framework.

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

@@ -22,6 +22,11 @@ void FlutterPlatformViewsController::SetFlutterView(UIView* flutter_view) {
   flutter_view_.reset([flutter_view retain]);
 }
 
+void FlutterPlatformViewsController::SetFlutterViewController(
+    UIViewController* flutter_view_controller) {
+  flutter_view_controller_.reset([flutter_view_controller retain]);
+}
+
 void FlutterPlatformViewsController::OnMethodCall(FlutterMethodCall* call, FlutterResult& result) {
   if ([[call method] isEqualToString:@"create"]) {
     OnCreate(call, result);
@@ -80,9 +85,9 @@ void FlutterPlatformViewsController::OnCreate(FlutterMethodCall* call, FlutterRe
                                                                 arguments:params];
   views_[viewId] = fml::scoped_nsobject<NSObject<FlutterPlatformView>>([embedded_view retain]);
 
-  FlutterTouchInterceptingView* touch_interceptor =
-      [[[FlutterTouchInterceptingView alloc] initWithEmbeddedView:embedded_view.view
-                                                      flutterView:flutter_view_] autorelease];
+  FlutterTouchInterceptingView* touch_interceptor = [[[FlutterTouchInterceptingView alloc]
+       initWithEmbeddedView:embedded_view.view
+      flutterViewController:flutter_view_controller_.get()] autorelease];
 
   touch_interceptors_[viewId] =
       fml::scoped_nsobject<FlutterTouchInterceptingView>([touch_interceptor retain]);
@@ -355,13 +360,15 @@ void FlutterPlatformViewsController::EnsureGLOverlayInitialized(
 // as well. So during this phase as well the ForwardingGestureRecognizer dispatched the events
 // directly to the FlutterView.
 @interface ForwardingGestureRecognizer : UIGestureRecognizer <UIGestureRecognizerDelegate>
-- (instancetype)initWithTarget:(id)target flutterView:(UIView*)flutterView;
+- (instancetype)initWithTarget:(id)target
+         flutterViewController:(UIViewController*)flutterViewController;
 @end
 
 @implementation FlutterTouchInterceptingView {
   fml::scoped_nsobject<DelayingGestureRecognizer> _delayingRecognizer;
 }
-- (instancetype)initWithEmbeddedView:(UIView*)embeddedView flutterView:(UIView*)flutterView {
+- (instancetype)initWithEmbeddedView:(UIView*)embeddedView
+               flutterViewController:(UIViewController*)flutterViewController {
   self = [super initWithFrame:embeddedView.frame];
   if (self) {
     self.multipleTouchEnabled = YES;
@@ -372,7 +379,7 @@ void FlutterPlatformViewsController::EnsureGLOverlayInitialized(
 
     ForwardingGestureRecognizer* forwardingRecognizer =
         [[[ForwardingGestureRecognizer alloc] initWithTarget:self
-                                                 flutterView:flutterView] autorelease];
+                                       flutterViewController:flutterViewController] autorelease];
 
     _delayingRecognizer.reset([[DelayingGestureRecognizer alloc]
               initWithTarget:self
@@ -446,35 +453,37 @@ void FlutterPlatformViewsController::EnsureGLOverlayInitialized(
 @implementation ForwardingGestureRecognizer {
   // We can't dispatch events to the framework without this back pointer.
   // This is a weak reference, the ForwardingGestureRecognizer is owned by the
-  // FlutterTouchInterceptingView which is strong referenced only by the FlutterView.
+  // FlutterTouchInterceptingView which is strong referenced only by the FlutterView,
+  // which is strongly referenced by the FlutterViewController.
   // So this is safe as when FlutterView is deallocated the reference to ForwardingGestureRecognizer
   // will go away.
-  UIView* _flutterView;
+  UIViewController* _flutterViewController;
   // Counting the pointers that has started in one touch sequence.
   NSInteger _currentTouchPointersCount;
 }
 
-- (instancetype)initWithTarget:(id)target flutterView:(UIView*)flutterView {
+- (instancetype)initWithTarget:(id)target
+         flutterViewController:(UIViewController*)flutterViewController {
   self = [super initWithTarget:target action:nil];
   if (self) {
     self.delegate = self;
-    _flutterView = flutterView;
+    _flutterViewController = flutterViewController;
     _currentTouchPointersCount = 0;
   }
   return self;
 }
 
 - (void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
-  [_flutterView touchesBegan:touches withEvent:event];
+  [_flutterViewController touchesBegan:touches withEvent:event];
   _currentTouchPointersCount += touches.count;
 }
 
 - (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event {
-  [_flutterView touchesMoved:touches withEvent:event];
+  [_flutterViewController touchesMoved:touches withEvent:event];
 }
 
 - (void)touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event {
-  [_flutterView touchesEnded:touches withEvent:event];
+  [_flutterViewController touchesEnded:touches withEvent:event];
   _currentTouchPointersCount -= touches.count;
   // Touches in one touch sequence are sent to the touchesEnded method separately if different
   // fingers stop touching the screen at different time. So one touchesEnded method triggering does
@@ -486,7 +495,7 @@ void FlutterPlatformViewsController::EnsureGLOverlayInitialized(
 }
 
 - (void)touchesCancelled:(NSSet*)touches withEvent:(UIEvent*)event {
-  [_flutterView touchesCancelled:touches withEvent:event];
+  [_flutterViewController touchesCancelled:touches withEvent:event];
   _currentTouchPointersCount = 0;
   self.state = UIGestureRecognizerStateFailed;
 }

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

@@ -18,7 +18,8 @@
 // 1. Delay or prevent touch events from arriving the embedded view.
 // 2. Dispatching all events that are hittested to the embedded view to the FlutterView.
 @interface FlutterTouchInterceptingView : UIView
-- (instancetype)initWithEmbeddedView:(UIView*)embeddedView flutterView:(UIView*)flutterView;
+- (instancetype)initWithEmbeddedView:(UIView*)embeddedView
+               flutterViewController:(UIViewController*)flutterViewController;
 
 // Stop delaying any active touch sequence (and let it arrive the embedded view).
 - (void)releaseGesture;
@@ -52,6 +53,8 @@ class FlutterPlatformViewsController {
 
   void SetFlutterView(UIView* flutter_view);
 
+  void SetFlutterViewController(UIViewController* flutter_view_controller);
+
   void RegisterViewFactory(NSObject<FlutterPlatformViewFactory>* factory, NSString* factoryId);
 
   void SetFrameSize(SkISize frame_size);
@@ -81,6 +84,7 @@ class FlutterPlatformViewsController {
  private:
   fml::scoped_nsobject<FlutterMethodChannel> channel_;
   fml::scoped_nsobject<UIView> flutter_view_;
+  fml::scoped_nsobject<UIViewController> flutter_view_controller_;
   std::map<std::string, fml::scoped_nsobject<NSObject<FlutterPlatformViewFactory>>> factories_;
   std::map<int64_t, fml::scoped_nsobject<NSObject<FlutterPlatformView>>> views_;
   std::map<int64_t, fml::scoped_nsobject<FlutterTouchInterceptingView>> touch_interceptors_;

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

@@ -382,10 +382,12 @@ NSNotificationName const FlutterSemanticsUpdateNotification = @"FlutterSemantics
   if (appeared) {
     [self installSplashScreenViewCallback];
     [_engine.get() platformViewsController] -> SetFlutterView(_flutterView.get());
+    [_engine.get() platformViewsController] -> SetFlutterViewController(self);
     [_engine.get() platformView] -> NotifyCreated();
   } else {
     [_engine.get() platformView] -> NotifyDestroyed();
     [_engine.get() platformViewsController] -> SetFlutterView(nullptr);
+    [_engine.get() platformViewsController] -> SetFlutterViewController(nullptr);
   }
 }