Call onTapCancel when down pointer gets cancelled (#28546)

packages/flutter/lib/src/gestures/tap.dart

@@ -174,6 +174,9 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
       _finalPosition = event.position;
       _checkUp();
     } else if (event is PointerCancelEvent) {
+      if (_sentTapDown && onTapCancel != null) {
+        invokeCallback<void>('onTapCancel', onTapCancel);
+      }
       _reset();
     }
   }
@@ -183,6 +186,7 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
     if (_wonArenaForPrimaryPointer && disposition == GestureDisposition.rejected) {
       // This can happen if the superclass decides the primary pointer
       // exceeded the touch slop, or if the recognizer is disposed.
+      assert(_sentTapDown);
       if (onTapCancel != null)
         invokeCallback<void>('spontaneous onTapCancel', onTapCancel);
       _reset();
@@ -211,7 +215,7 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
     if (pointer == primaryPointer) {
       // Another gesture won the arena.
       assert(state != GestureRecognizerState.possible);
-      if (onTapCancel != null)
+      if (_sentTapDown && onTapCancel != null)
         invokeCallback<void>('forced onTapCancel', onTapCancel);
       _reset();
     }

packages/flutter/test/gestures/tap_test.dart

@@ -388,7 +388,6 @@ void main() {
       'tapA onTapDown',
       'tapA onTapUp',
       'tapA onTap',
-      'tapB onTapCancel',
       'swept 1',
       'down 2 to A',
       'down 2 to B',
@@ -398,10 +397,74 @@ void main() {
       'tapA onTapDown',
       'tapA onTapUp',
       'tapA onTap',
-      'tapB onTapCancel',
       'swept 2',
       'disposed A',
       'disposed B',
     ]);
   });
+
+  testGesture('PointerCancelEvent cancels tap', (GestureTester tester) {
+    const PointerDownEvent down = PointerDownEvent(
+        pointer: 5,
+        position: Offset(10.0, 10.0)
+    );
+    const PointerCancelEvent cancel = PointerCancelEvent(
+        pointer: 5,
+        position: Offset(10.0, 10.0)
+    );
+
+    final TapGestureRecognizer tap = TapGestureRecognizer();
+
+    final List<String> recognized = <String>[];
+    tap.onTapDown = (_) {
+      recognized.add('down');
+    };
+    tap.onTapUp = (_) {
+      recognized.add('up');
+    };
+    tap.onTap = () {
+      recognized.add('tap');
+    };
+    tap.onTapCancel = () {
+      recognized.add('cancel');
+    };
+
+    tap.addPointer(down);
+    tester.closeArena(5);
+    tester.async.elapse(const Duration(milliseconds: 5000));
+    expect(recognized, <String>['down']);
+    tester.route(cancel);
+    expect(recognized, <String>['down', 'cancel']);
+
+    tap.dispose();
+  });
+
+  testGesture('losing tap gesture recognizer does not send onTapCancel', (GestureTester tester) {
+    final TapGestureRecognizer tap = TapGestureRecognizer();
+    final HorizontalDragGestureRecognizer drag = HorizontalDragGestureRecognizer();
+
+    final List<String> recognized = <String>[];
+    tap.onTapDown = (_) {
+      recognized.add('down');
+    };
+    tap.onTapUp = (_) {
+      recognized.add('up');
+    };
+    tap.onTap = () {
+      recognized.add('tap');
+    };
+    tap.onTapCancel = () {
+      recognized.add('cancel');
+    };
+
+    tap.addPointer(down3);
+    drag.addPointer(down3);
+    tester.closeArena(3);
+    tester.route(move3);
+    GestureBinding.instance.gestureArena.sweep(3);
+    expect(recognized, isEmpty);
+
+    tap.dispose();
+    drag.dispose();
+  });
 }

packages/flutter/test/material/ink_well_test.dart

@@ -54,7 +54,7 @@ void main() {
     await tester.tap(find.byType(InkWell), pointer: 2);
     await tester.tap(find.byType(InkWell), pointer: 3);
 
-    expect(log, equals(<String>['tap-cancel', 'double-tap']));
+    expect(log, equals(<String>['double-tap']));
     log.clear();
 
     await tester.longPress(find.byType(InkWell), pointer: 4);

packages/flutter/test/widgets/gesture_detector_test.dart

@@ -287,33 +287,32 @@ void main() {
     );
 
     // Pointer is dragged from the center of the 800x100 gesture detector
-    // to a point (400,300) below it. This always causes onTapCancel to be
-    // called; onTap should never be called.
+    // to a point (400,300) below it. This should never call onTap.
     Future<void> dragOut(Duration timeout) async {
       final TestGesture gesture = await tester.startGesture(const Offset(400.0, 50.0));
-      // If the timeout is less than kPressTimeout the recognizer will just trigger
-      // the onTapCancel callback. If the timeout is greater than kLongPressTimeout
+      // If the timeout is less than kPressTimeout the recognizer will not
+      // trigger any callbacks. If the timeout is greater than kLongPressTimeout
       // then onTapDown, onLongPress, and onCancel will be called.
       await tester.pump(timeout);
       await gesture.moveTo(const Offset(400.0, 300.0));
       await gesture.up();
     }
 
-    await dragOut(kPressTimeout * 0.5); // generates tapCancel
+    await dragOut(kPressTimeout * 0.5); // generates nothing
     expect(tapDown, 0);
-    expect(tapCancel, 1);
+    expect(tapCancel, 0);
     expect(tap, 0);
     expect(longPress, 0);
 
     await dragOut(kPressTimeout); // generates tapDown, tapCancel
     expect(tapDown, 1);
-    expect(tapCancel, 2);
+    expect(tapCancel, 1);
     expect(tap, 0);
     expect(longPress, 0);
 
     await dragOut(kLongPressTimeout); // generates tapDown, longPress, tapCancel
     expect(tapDown, 2);
-    expect(tapCancel, 3);
+    expect(tapCancel, 2);
     expect(tap, 0);
     expect(longPress, 1);
   });

packages/flutter/test/widgets/text_selection_test.dart

@@ -119,7 +119,7 @@ void main() {
     expect(singleLongTapStartCount, 0);
   });
 
-  testWidgets('a very quick swipe is just a canceled tap', (WidgetTester tester) async {
+  testWidgets('a very quick swipe is ignored', (WidgetTester tester) async {
     await pumpGestureDetector(tester);
     final TestGesture gesture = await tester.startGesture(const Offset(200, 200));
     await tester.pump(const Duration(milliseconds: 20));
@@ -127,7 +127,7 @@ void main() {
     await tester.pump();
     expect(singleTapUpCount, 0);
     expect(tapCount, 0);
-    expect(singleTapCancelCount, 1);
+    expect(singleTapCancelCount, 0);
     expect(doubleTapDownCount, 0);
     expect(singleLongTapStartCount, 0);
 
@@ -135,7 +135,7 @@ void main() {
     // Nothing else happens on up.
     expect(singleTapUpCount, 0);
     expect(tapCount, 0);
-    expect(singleTapCancelCount, 1);
+    expect(singleTapCancelCount, 0);
     expect(doubleTapDownCount, 0);
     expect(singleLongTapStartCount, 0);
   });