Fix a gesture failure problem on iOS

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

@@ -21,8 +21,13 @@
 #include "flutter/shell/platform/darwin/ios/framework/Source/platform_message_response_darwin.h"
 #include "flutter/shell/platform/darwin/ios/platform_view_ios.h"
 
+static double kTouchTrackerCheckInterval = 1.f;
+
 @interface FlutterViewController () <FlutterTextInputDelegate>
 @property(nonatomic, readonly) NSMutableDictionary* pluginPublications;
+@property(nonatomic, retain) NSMutableSet* touchTrackerSet;
+@property(nonatomic, retain) NSMutableDictionary<NSValue*, NSNumber*>* touchTrackerDict;
+
 @end
 
 @interface FlutterViewControllerRegistrar : NSObject <FlutterPluginRegistrar>
@@ -70,6 +75,9 @@ - (instancetype)initWithProject:(FlutterDartProject*)projectOrNil
     else
       _dartProject.reset([projectOrNil retain]);
 
+    _touchTrackerSet = [[NSMutableSet set] retain];
+    _touchTrackerDict = [[NSMutableDictionary dictionary] retain];
+
     [self performCommonViewControllerInitialization];
   }
 
@@ -476,6 +484,9 @@ - (void)viewDidDisappear:(BOOL)animated {
 - (void)dealloc {
   [[NSNotificationCenter defaultCenter] removeObserver:self];
   [_pluginPublications release];
+  [_touchTrackerSet release];
+  [_touchTrackerDict release];
+
   [super dealloc];
 }
 
@@ -547,30 +558,51 @@ static inline PointerChangeMapperPhase PointerChangePhaseFromUITouchPhase(UITouc
   return blink::PointerData::DeviceKind::kTouch;
 }
 
-- (void)dispatchTouches:(NSSet*)touches phase:(UITouchPhase)phase {
+- (void)dispatchTouches:(NSSet*)touches phase:(UITouchPhase)phase trackTouches:(BOOL)bTrack {
   // Note: we cannot rely on touch.phase, since in some cases, e.g.,
   // handleStatusBarTouches, we synthesize touches from existing events.
   //
   // TODO(cbracken) consider creating out own class with the touch fields we
   // need.
+  NSTimeInterval tsNow = [[NSDate date] timeIntervalSinceReferenceDate];
   auto eventTypePhase = PointerChangePhaseFromUITouchPhase(phase);
   const CGFloat scale = [UIScreen mainScreen].scale;
   auto packet = std::make_unique<blink::PointerDataPacket>(touches.count);
 
   int i = 0;
   for (UITouch* touch in touches) {
     int device_id = 0;
+    NSValue* key = [NSValue valueWithPointer:(void*)touch];
 
     switch (eventTypePhase.second) {
-      case Accessed:
+      case Accessed: {
         device_id = _touchMapper.identifierOf(touch);
+        if (bTrack) {
+          [self.touchTrackerSet addObject:touch];
+          self.touchTrackerDict[key] = @(tsNow + kTouchTrackerCheckInterval);
+        }
         break;
-      case Added:
+      }
+      case Added: {
         device_id = _touchMapper.registerTouch(touch);
+        if (bTrack) {
+          [self.touchTrackerSet addObject:touch];
+          self.touchTrackerDict[key] = @(tsNow + kTouchTrackerCheckInterval);
+        }
         break;
-      case Removed:
+      }
+      case Removed: {
         device_id = _touchMapper.unregisterTouch(touch);
+        if (bTrack) {
+          [self.touchTrackerDict removeObjectForKey:key];
+          [self.touchTrackerSet removeObject:touch];
+        }
         break;
+      }
+    }
+
+    if (device_id == 0) {
+      continue;
     }
 
     FML_DCHECK(device_id != 0);
@@ -656,19 +688,44 @@ - (void)dispatchTouches:(NSSet*)touches phase:(UITouchPhase)phase {
 }
 
 - (void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
-  [self dispatchTouches:touches phase:UITouchPhaseBegan];
+  [self dispatchTouches:touches phase:UITouchPhaseBegan trackTouches:TRUE];
+  [self checkIfCompleteTouches];
 }
 
 - (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event {
-  [self dispatchTouches:touches phase:UITouchPhaseMoved];
+  [self dispatchTouches:touches phase:UITouchPhaseMoved trackTouches:TRUE];
 }
 
 - (void)touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event {
-  [self dispatchTouches:touches phase:UITouchPhaseEnded];
+  [self dispatchTouches:touches phase:UITouchPhaseEnded trackTouches:TRUE];
 }
 
 - (void)touchesCancelled:(NSSet*)touches withEvent:(UIEvent*)event {
-  [self dispatchTouches:touches phase:UITouchPhaseCancelled];
+  [self dispatchTouches:touches phase:UITouchPhaseCancelled trackTouches:TRUE];
+}
+
+- (BOOL)checkIfCompleteTouches {
+  NSInteger cnt = self.touchTrackerSet.count;
+  if (cnt <= 0)
+    return FALSE;
+  NSTimeInterval tsNow = [[NSDate date] timeIntervalSinceReferenceDate];
+  NSSet* tmpTrackingTouches = [self.touchTrackerSet copy];
+  NSMutableSet* set = [NSMutableSet set];
+  for (UITouch* touch in tmpTrackingTouches) {
+    NSValue* key = [NSValue valueWithPointer:(void*)touch];
+    NSNumber* expiredTime = [self.touchTrackerDict objectForKey:key];
+    if (expiredTime.doubleValue <= tsNow) {
+      [set addObject:touch];
+      [self.touchTrackerDict removeObjectForKey:key];
+      [self.touchTrackerSet removeObject:touch];
+    }
+  }
+  if (set.count > 0) {
+    [self dispatchTouches:set phase:UITouchPhaseBegan trackTouches:FALSE];
+    [self dispatchTouches:set phase:UITouchPhaseCancelled trackTouches:FALSE];
+    return TRUE;
+  }
+  return FALSE;
 }
 
 #pragma mark - Handle view resizing
@@ -973,8 +1030,8 @@ - (void)handleStatusBarTouches:(UIEvent*)event {
       CGPoint screenLoc = [touch.window convertPoint:windowLoc toWindow:nil];
       if (CGRectContainsPoint(statusBarFrame, screenLoc)) {
         NSSet* statusbarTouches = [NSSet setWithObject:touch];
-        [self dispatchTouches:statusbarTouches phase:UITouchPhaseBegan];
-        [self dispatchTouches:statusbarTouches phase:UITouchPhaseEnded];
+        [self dispatchTouches:statusbarTouches phase:UITouchPhaseBegan trackTouches:TRUE];
+        [self dispatchTouches:statusbarTouches phase:UITouchPhaseEnded trackTouches:TRUE];
         return;
       }
     }

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

@@ -11,20 +11,29 @@
 TouchMapper::~TouchMapper() = default;
 
 int TouchMapper::registerTouch(UITouch* touch) {
+  if (touch_map_.find(touch) != touch_map_.end()) {
+    return 0;
+  }
   int freeSpot = ffsll(free_spots_);
   touch_map_[touch] = freeSpot;
   free_spots_ &= ~(1 << (freeSpot - 1));
   return freeSpot;
 }
 
 int TouchMapper::unregisterTouch(UITouch* touch) {
+  if (touch_map_.find(touch) == touch_map_.end()) {
+    return 0;
+  }
   auto index = touch_map_[touch];
   free_spots_ |= 1 << (index - 1);
   touch_map_.erase(touch);
   return index;
 }
 
 int TouchMapper::identifierOf(UITouch* touch) const {
+  if (touch_map_.find(touch) == touch_map_.end()) {
+    return 0;
+  }
   return touch_map_.at(touch);
 }