Fixed the ability to scroll to the top on iOS 13

shell/platform/darwin/ios/framework/Headers/FlutterAppDelegate.h

@@ -29,15 +29,6 @@ FLUTTER_EXPORT
 
 @property(strong, nonatomic) UIWindow* window;
 
-/**
- * Handle StatusBar touches.
- *
- * Call this from your AppDelegate's `touchesBegan:withEvent:` to have Flutter respond to StatusBar
- * touches.  For example, to enable scroll-to-top behavior.  FlutterAppDelegate already calls it so
- * you only need to manually call it if you aren't using a FlutterAppDelegate.
- */
-+ (void)handleStatusBarTouches:(NSSet<UITouch*>*)touches withEvent:(UIEvent*)event;
-
 @end
 
 #endif  // FLUTTER_FLUTTERDARTPROJECT_H_

shell/platform/darwin/ios/framework/Headers/FlutterViewController.h

@@ -72,8 +72,6 @@ FLUTTER_EXPORT
                         nibName:(nullable NSString*)nibName
                          bundle:(nullable NSBundle*)nibBundle NS_DESIGNATED_INITIALIZER;
 
-- (void)handleStatusBarTouches:(UIEvent*)event;
-
 /**
  * Registers a callback that will be invoked when the Flutter view has been rendered.
  * The callback will be fired only once.

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

@@ -48,15 +48,6 @@ + (FlutterViewController*)rootFlutterViewController {
   return nil;
 }
 
-+ (void)handleStatusBarTouches:(NSSet<UITouch*>*)touches withEvent:(UIEvent*)event {
-  [self.rootFlutterViewController handleStatusBarTouches:event];
-}
-
-- (void)touchesBegan:(NSSet<UITouch*>*)touches withEvent:(UIEvent*)event {
-  [super touchesBegan:touches withEvent:event];
-  [[self class] handleStatusBarTouches:touches withEvent:event];
-}
-
 // Do not remove, some clients may be calling these via `super`.
 - (void)applicationDidEnterBackground:(UIApplication*)application {
 }

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

@@ -23,6 +23,8 @@
 #import "flutter/shell/platform/darwin/ios/framework/Source/platform_message_response_darwin.h"
 #import "flutter/shell/platform/darwin/ios/platform_view_ios.h"
 
+constexpr int kMicrosecondsPerSecond = 1000 * 1000;
+
 NSNotificationName const FlutterSemanticsUpdateNotification = @"FlutterSemanticsUpdate";
 
 NSNotificationName const FlutterViewControllerWillDealloc = @"FlutterViewControllerWillDealloc";
@@ -86,7 +88,7 @@ - (void)invalidate {
 // This is left a FlutterBinaryMessenger privately for now to give people a chance to notice the
 // change. Unfortunately unless you have Werror turned on, incompatible pointers as arguments are
 // just a warning.
-@interface FlutterViewController () <FlutterBinaryMessenger>
+@interface FlutterViewController () <FlutterBinaryMessenger, UIScrollViewDelegate>
 @property(nonatomic, readwrite, getter=isDisplayingFlutterUI) BOOL displayingFlutterUI;
 @end
 
@@ -123,6 +125,7 @@ @implementation FlutterViewController {
   // Coalescer that filters out superfluous keyboard notifications when the app
   // is being foregrounded.
   fml::scoped_nsobject<FlutterCoalescer> _updateViewportMetrics;
+  fml::scoped_nsobject<UIScrollView> _scrollView;
 }
 
 @synthesize displayingFlutterUI = _displayingFlutterUI;
@@ -329,6 +332,46 @@ - (void)loadView {
   self.view.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
 
   [self installSplashScreenViewIfNecessary];
+  // This is a workaround to accomodate iOS 13 and higher.  There isn't a way to get touches on the
+  // status bar to trigger scrolling to the top of a scroll view.  We place a UIScrollView offscreen
+  // with a content offset so we can get those events. See also:
+  // https://github.com/flutter/flutter/issues/35050
+  UIScrollView* scrollView = [[UIScrollView alloc] init];
+  scrollView.autoresizingMask = UIViewAutoresizingFlexibleWidth;
+  // The color shouldn't matter since it is offscreen.
+  scrollView.backgroundColor = UIColor.whiteColor;
+  scrollView.delegate = self;
+  // This is an arbitrary small size.
+  scrollView.contentSize = CGSizeMake(10, 10);
+  // This is an arbitrary offset that is not CGPointZero.
+  scrollView.contentOffset = CGPointMake(10, 10);
+  // This is some aribrary place offscreen.
+  scrollView.bounds = CGRectMake(0, -10, 0, 10);
+  [self.view addSubview:scrollView];
+  _scrollView.reset(scrollView);
+}
+
+static void sendFakeTouchEvent(FlutterEngine* engine,
+                               CGPoint location,
+                               flutter::PointerData::Change change) {
+  const CGFloat scale = [UIScreen mainScreen].scale;
+  flutter::PointerData pointer_data;
+  pointer_data.Clear();
+  pointer_data.physical_x = location.x * scale;
+  pointer_data.physical_y = location.y * scale;
+  pointer_data.kind = flutter::PointerData::DeviceKind::kTouch;
+  pointer_data.time_stamp = [[NSDate date] timeIntervalSince1970] * kMicrosecondsPerSecond;
+  auto packet = std::make_unique<flutter::PointerDataPacket>(/*count=*/1);
+  pointer_data.change = change;
+  packet->SetPointerData(0, pointer_data);
+  [engine dispatchPointerDataPacket:std::move(packet)];
+}
+
+- (BOOL)scrollViewShouldScrollToTop:(UIScrollView*)scrollView {
+  CGPoint statusBarPoint = CGPointZero;
+  sendFakeTouchEvent(_engine.get(), statusBarPoint, flutter::PointerData::Change::kDown);
+  sendFakeTouchEvent(_engine.get(), statusBarPoint, flutter::PointerData::Change::kUp);
+  return NO;
 }
 
 #pragma mark - Managing launch views
@@ -569,7 +612,6 @@ - (void)flushOngoingTouches {
       flutter::PointerData pointer_data;
       pointer_data.Clear();
 
-      constexpr int kMicrosecondsPerSecond = 1000 * 1000;
       // Use current time.
       pointer_data.time_stamp = [[NSDate date] timeIntervalSince1970] * kMicrosecondsPerSecond;
 
@@ -835,6 +877,9 @@ - (void)viewDidLayoutSubviews {
   CGSize viewSize = self.view.bounds.size;
   CGFloat scale = [UIScreen mainScreen].scale;
 
+  // Purposefully place this offscreen.
+  _scrollView.get().bounds = CGRectMake(0.0, -10.0, viewSize.width, 0);
+
   // First time since creation that the dimensions of its view is known.
   bool firstViewBoundsUpdate = !_viewportMetrics.physical_width;
   _viewportMetrics.device_pixel_ratio = scale;
@@ -1146,42 +1191,6 @@ - (NSString*)contrastMode {
   }
 }
 
-#pragma mark - Status Bar touch event handling
-
-// Standard iOS status bar height in points.
-constexpr CGFloat kStandardStatusBarHeight = 20.0;
-
-- (void)handleStatusBarTouches:(UIEvent*)event {
-  CGFloat standardStatusBarHeight = kStandardStatusBarHeight;
-  if (@available(iOS 11, *)) {
-    standardStatusBarHeight = self.view.safeAreaInsets.top;
-  }
-
-  // If the status bar is double-height, don't handle status bar taps. iOS
-  // should open the app associated with the status bar.
-  CGRect statusBarFrame = [UIApplication sharedApplication].statusBarFrame;
-  if (statusBarFrame.size.height != standardStatusBarHeight) {
-    return;
-  }
-
-  // If we detect a touch in the status bar, synthesize a fake touch begin/end.
-  for (UITouch* touch in event.allTouches) {
-    if (touch.phase == UITouchPhaseBegan && touch.tapCount > 0) {
-      CGPoint windowLoc = [touch locationInView:nil];
-      CGPoint screenLoc = [touch.window convertPoint:windowLoc toWindow:nil];
-      if (CGRectContainsPoint(statusBarFrame, screenLoc)) {
-        NSSet* statusbarTouches = [NSSet setWithObject:touch];
-
-        flutter::PointerData::Change change = flutter::PointerData::Change::kDown;
-        [self dispatchTouches:statusbarTouches pointerDataChangeOverride:&change];
-        change = flutter::PointerData::Change::kUp;
-        [self dispatchTouches:statusbarTouches pointerDataChangeOverride:&change];
-        return;
-      }
-    }
-  }
-}
-
 #pragma mark - Status bar style
 
 - (UIStatusBarStyle)preferredStatusBarStyle {