Fixed the ability to scroll to the top on iOS 13 (#16820)

Author: gaaclarke

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 +23,9 @@
 #import "flutter/shell/platform/darwin/ios/framework/Source/platform_message_response_darwin.h"
 #import "flutter/shell/platform/darwin/ios/platform_view_ios.h"
 
+static constexpr int kMicrosecondsPerSecond = 1000 * 1000;
+static constexpr CGFloat kScrollViewContentSize = 2.0;
+
 NSNotificationName const FlutterSemanticsUpdateNotification = @"FlutterSemanticsUpdate";
 
 NSNotificationName const FlutterViewControllerWillDealloc = @"FlutterViewControllerWillDealloc";
@@ -86,7 +89,7 @@ - (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 +126,11 @@ @implementation FlutterViewController {
   // Coalescer that filters out superfluous keyboard notifications when the app
   // is being foregrounded.
   fml::scoped_nsobject<FlutterCoalescer> _updateViewportMetrics;
+  // This scroll view 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 with height zero and a content offset so we can get those events. See also:
+  // https://github.com/flutter/flutter/issues/35050
+  fml::scoped_nsobject<UIScrollView> _scrollView;
 }
 
 @synthesize displayingFlutterUI = _displayingFlutterUI;
@@ -329,6 +337,40 @@ - (void)loadView {
   self.view.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
 
   [self installSplashScreenViewIfNecessary];
+  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(kScrollViewContentSize, kScrollViewContentSize);
+  // This is an arbitrary offset that is not CGPointZero.
+  scrollView.contentOffset = CGPointMake(kScrollViewContentSize, kScrollViewContentSize);
+  [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 +611,6 @@ - (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 +876,10 @@ - (void)viewDidLayoutSubviews {
   CGSize viewSize = self.view.bounds.size;
   CGFloat scale = [UIScreen mainScreen].scale;
 
+  // Purposefully place this not visible.
+  _scrollView.get().frame = CGRectMake(0.0, 0.0, viewSize.width, 0.0);
+  _scrollView.get().contentOffset = CGPointMake(kScrollViewContentSize, kScrollViewContentSize);
+
   // 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 {

testing/scenario_app/ios/Scenarios/Scenarios.xcodeproj/project.pbxproj

@@ -11,6 +11,7 @@
 		0A57B3BF2323C74200DD9521 /* FlutterEngine+ScenariosTest.m in Sources */ = {isa = PBXBuildFile; fileRef = 0A57B3BE2323C74200DD9521 /* FlutterEngine+ScenariosTest.m */; };
 		0A57B3C22323D2D700DD9521 /* AppLifecycleTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 0A57B3C12323D2D700DD9521 /* AppLifecycleTests.m */; };
 		0D14A3FE239743190013D873 /* golden_platform_view_rotate_iPhone SE_simulator.png in Resources */ = {isa = PBXBuildFile; fileRef = 0D14A3FD239743190013D873 /* golden_platform_view_rotate_iPhone SE_simulator.png */; };
+		0D8470A4240F0B1F0030B565 /* StatusBarTest.m in Sources */ = {isa = PBXBuildFile; fileRef = 0D8470A3240F0B1F0030B565 /* StatusBarTest.m */; };
 		0DB781EF22E931BE00E9B371 /* Flutter.framework in CopyFiles */ = {isa = PBXBuildFile; fileRef = 246B4E4522E3B61000073EBF /* Flutter.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
 		0DB781F122E933E800E9B371 /* Flutter.framework in CopyFiles */ = {isa = PBXBuildFile; fileRef = 246B4E4522E3B61000073EBF /* Flutter.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
 		0DB781FE22EA2C6D00E9B371 /* Flutter.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 246B4E4522E3B61000073EBF /* Flutter.framework */; };
@@ -114,6 +115,8 @@
 		0A57B3C02323C74D00DD9521 /* FlutterEngine+ScenariosTest.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "FlutterEngine+ScenariosTest.h"; sourceTree = "<group>"; };
 		0A57B3C12323D2D700DD9521 /* AppLifecycleTests.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = AppLifecycleTests.m; sourceTree = "<group>"; };
 		0D14A3FD239743190013D873 /* golden_platform_view_rotate_iPhone SE_simulator.png */ = {isa = PBXFileReference; lastKnownFileType = image.png; path = "golden_platform_view_rotate_iPhone SE_simulator.png"; sourceTree = "<group>"; };
+		0D8470A2240F0B1F0030B565 /* StatusBarTest.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = StatusBarTest.h; sourceTree = "<group>"; };
+		0D8470A3240F0B1F0030B565 /* StatusBarTest.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = StatusBarTest.m; sourceTree = "<group>"; };
 		0DB781FC22EA2C0300E9B371 /* FlutterViewControllerTest.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = FlutterViewControllerTest.m; sourceTree = "<group>"; };
 		244EA6CF230DBE8900B2D26E /* golden_platform_view_D21AP.png */ = {isa = PBXFileReference; lastKnownFileType = image.png; path = golden_platform_view_D21AP.png; sourceTree = "<group>"; };
 		246B4E4122E3B5F700073EBF /* App.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; path = App.framework; sourceTree = "<group>"; };
@@ -272,6 +275,8 @@
 				6816DBA22318358200A51400 /* PlatformViewGoldenTestManager.h */,
 				6816DBA32318358200A51400 /* PlatformViewGoldenTestManager.m */,
 				68A5B63323EB71D300BDBCDB /* PlatformViewGestureRecognizerTests.m */,
+				0D8470A2240F0B1F0030B565 /* StatusBarTest.h */,
+				0D8470A3240F0B1F0030B565 /* StatusBarTest.m */,
 			);
 			path = ScenariosUITests;
 			sourceTree = "<group>";
@@ -466,6 +471,7 @@
 				6816DB9E231750ED00A51400 /* GoldenPlatformViewTests.m in Sources */,
 				6816DBA42318358200A51400 /* PlatformViewGoldenTestManager.m in Sources */,
 				248D76EF22E388380012F0C1 /* PlatformViewUITests.m in Sources */,
+				0D8470A4240F0B1F0030B565 /* StatusBarTest.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

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

@@ -41,6 +41,7 @@ - (BOOL)application:(UIApplication*)application
     @"--gesture-reject-after-touches-ended" : @"platform_view_gesture_reject_after_touches_ended",
     @"--gesture-reject-eager" : @"platform_view_gesture_reject_eager",
     @"--gesture-accept" : @"platform_view_gesture_accept",
+    @"--tap-status-bar" : @"tap_status_bar",
   };
   __block NSString* platformViewTestName = nil;
   [launchArgsMap
@@ -67,15 +68,33 @@ - (void)readyContextForPlatformViewTests:(NSString*)scenarioIdentifier {
   FlutterEngine* engine = [[FlutterEngine alloc] initWithName:@"PlatformViewTest" project:nil];
   [engine runWithEntrypoint:nil];
 
-  FlutterViewController* flutterViewController =
-      [[NoStatusBarFlutterViewController alloc] initWithEngine:engine nibName:nil bundle:nil];
+  FlutterViewController* flutterViewController;
+  if ([scenarioIdentifier isEqualToString:@"tap_status_bar"]) {
+    flutterViewController = [[FlutterViewController alloc] initWithEngine:engine
+                                                                  nibName:nil
+                                                                   bundle:nil];
+  } else {
+    flutterViewController = [[NoStatusBarFlutterViewController alloc] initWithEngine:engine
+                                                                             nibName:nil
+                                                                              bundle:nil];
+  }
   [engine.binaryMessenger
       setMessageHandlerOnChannel:@"scenario_status"
             binaryMessageHandler:^(NSData* _Nullable message, FlutterBinaryReply _Nonnull reply) {
               [engine.binaryMessenger
                   sendOnChannel:@"set_scenario"
                         message:[scenarioIdentifier dataUsingEncoding:NSUTF8StringEncoding]];
             }];
+  [engine.binaryMessenger
+      setMessageHandlerOnChannel:@"touches_scenario"
+            binaryMessageHandler:^(NSData* _Nullable message, FlutterBinaryReply _Nonnull reply) {
+              NSDictionary* dict = [NSJSONSerialization JSONObjectWithData:message
+                                                                   options:0
+                                                                     error:nil];
+              UITextField* text = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, 300, 100)];
+              text.text = dict[@"change"];
+              [flutterViewController.view addSubview:text];
+            }];
   TextPlatformViewFactory* textPlatformViewFactory =
       [[TextPlatformViewFactory alloc] initWithMessenger:flutterViewController.binaryMessenger];
   NSObject<FlutterPluginRegistrar>* registrar =

testing/scenario_app/ios/Scenarios/ScenariosUITests/StatusBarTest.h

@@ -0,0 +1,13 @@
+// Copyright 2020 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import <XCTest/XCTest.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface StatusBarTest : XCTestCase
+@property(nonatomic, strong) XCUIApplication* application;
+@end
+
+NS_ASSUME_NONNULL_END

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

@@ -0,0 +1,41 @@
+// Copyright 2020 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "StatusBarTest.h"
+
+@implementation StatusBarTest
+
+- (void)setUp {
+  [super setUp];
+  self.continueAfterFailure = NO;
+
+  self.application = [[XCUIApplication alloc] init];
+  self.application.launchArguments = @[ @"--tap-status-bar" ];
+  [self.application launch];
+}
+
+- (void)testTapStatusBar {
+  if (@available(iOS 13, *)) {
+    XCUIApplication* systemApp =
+        [[XCUIApplication alloc] initWithBundleIdentifier:@"com.apple.springboard"];
+    XCUIElement* statusBar = [systemApp.statusBars firstMatch];
+    if (statusBar.isHittable) {
+      [statusBar tap];
+    } else {
+      XCUICoordinate* coordinates = [statusBar coordinateWithNormalizedOffset:CGVectorMake(0, 0)];
+      [coordinates tap];
+    }
+  } else {
+    [[self.application.statusBars firstMatch] tap];
+  }
+
+  XCUIElement* addTextField = self.application.textFields[@"PointerChange.add"];
+  BOOL exists = [addTextField waitForExistenceWithTimeout:1];
+  XCTAssertTrue(exists, @"");
+  XCUIElement* upTextField = self.application.textFields[@"PointerChange.up"];
+  exists = [upTextField waitForExistenceWithTimeout:1];
+  XCTAssertTrue(exists, @"");
+}
+
+@end

testing/scenario_app/lib/main.dart

@@ -14,6 +14,7 @@ import 'src/animated_color_square.dart';
 import 'src/platform_view.dart';
 import 'src/poppable_screen.dart';
 import 'src/scenario.dart';
+import 'src/touches_scenario.dart';
 
 Map<String, Scenario> _scenarios = <String, Scenario>{
   'animated_color_square': AnimatedColorSquareScenario(window),
@@ -30,6 +31,7 @@ Map<String, Scenario> _scenarios = <String, Scenario>{
   'platform_view_gesture_reject_eager': PlatformViewForTouchIOSScenario(window, 'platform view touch', id: 11, accept: false),
   'platform_view_gesture_accept': PlatformViewForTouchIOSScenario(window, 'platform view touch', id: 11, accept: true),
   'platform_view_gesture_reject_after_touches_ended': PlatformViewForTouchIOSScenario(window, 'platform view touch', id: 11, accept: false, rejectUntilTouchesEnded: true),
+  'tap_status_bar' : TouchesScenario(window),
 };
 
 Scenario _currentScenario = _scenarios['animated_color_square'];

testing/scenario_app/lib/src/touches_scenario.dart

@@ -0,0 +1,31 @@
+// Copyright 2020 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:convert';
+import 'dart:ui';
+
+import 'scenario.dart';
+
+/// A scenario that sends back messages when touches are received.
+class TouchesScenario extends Scenario {
+  /// Constructor for `TouchesScenario`.
+  TouchesScenario(Window window) : super(window);
+
+  @override
+  void onBeginFrame(Duration duration) {}
+
+  @override
+  void onPointerDataPacket(PointerDataPacket packet) {
+    window.sendPlatformMessage(
+      'touches_scenario',
+      utf8.encoder
+          .convert(const JsonCodec().encode(<String, dynamic>{
+            'change': packet.data[0].change.toString(),
+          }))
+          .buffer
+          .asByteData(),
+      null,
+    );
+  }
+}