Refactor: Base tap gesture recognizer (#41329)

* Extracts the logic of TapGestureRecognizer into an abstract class BaseTapGestureRecognizer
* Fixes ModalBarrier unable to dismiss when competing

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

@@ -59,7 +59,7 @@ class _GestureArena {
   bool isHeld = false;
   bool hasPendingSweep = false;
 
-  /// If a gesture attempts to win while the arena is still open, it becomes the
+  /// If a member attempts to win while the arena is still open, it becomes the
   /// "eager winner". We look for an eager winner when closing the arena to new
   /// participants, and if there is one, we resolve the arena in its favor at
   /// that time.

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

@@ -68,10 +68,10 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
 
   /// Configure the behavior of offsets sent to [onStart].
   ///
-  /// If set to [DragStartBehavior.start], the [onStart] callback will be called at the time and
-  /// position when the gesture detector wins the arena. If [DragStartBehavior.down],
-  /// [onStart] will be called at the time and position when a down event was
-  /// first detected.
+  /// If set to [DragStartBehavior.start], the [onStart] callback will be called
+  /// at the time and position when this gesture recognizer wins the arena. If
+  /// [DragStartBehavior.down], [onStart] will be called at the time and
+  /// position when a down event was first detected.
   ///
   /// For more information about the gesture arena:
   /// https://flutter.dev/docs/development/ui/advanced/gestures#gesture-disambiguation
@@ -80,9 +80,9 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
   ///
   /// ## Example:
   ///
-  /// A finger presses down on the screen with offset (500.0, 500.0),
-  /// and then moves to position (510.0, 500.0) before winning the arena.
-  /// With [dragStartBehavior] set to [DragStartBehavior.down], the [onStart]
+  /// A finger presses down on the screen with offset (500.0, 500.0), and then
+  /// moves to position (510.0, 500.0) before winning the arena. With
+  /// [dragStartBehavior] set to [DragStartBehavior.down], the [onStart]
   /// callback will be called at the time corresponding to the touch's position
   /// at (500.0, 500.0). If it is instead set to [DragStartBehavior.start],
   /// [onStart] will be called at the time corresponding to the touch's position

packages/flutter/lib/src/widgets/modal_barrier.dart

@@ -191,99 +191,41 @@ class AnimatedModalBarrier extends AnimatedWidget {
 //
 // It is similar to [TapGestureRecognizer.onTapDown], but accepts any single
 // button, which means the gesture also takes parts in gesture arenas.
-class _AnyTapGestureRecognizer extends PrimaryPointerGestureRecognizer {
-  _AnyTapGestureRecognizer({
-    Object debugOwner,
-  }) : super(debugOwner: debugOwner);
+class _AnyTapGestureRecognizer extends BaseTapGestureRecognizer {
+  _AnyTapGestureRecognizer({ Object debugOwner })
+    : super(debugOwner: debugOwner);
 
   VoidCallback onAnyTapDown;
 
-  bool _sentTapDown = false;
-  bool _wonArenaForPrimaryPointer = false;
-  // The buttons sent by `PointerDownEvent`. If a `PointerMoveEvent` comes with a
-  // different set of buttons, the gesture is canceled.
-  int _initialButtons;
-
-  @override
-  void addAllowedPointer(PointerDownEvent event) {
-    super.addAllowedPointer(event);
-    // `_initialButtons` must be assigned here instead of `handlePrimaryPointer`,
-    // because `acceptGesture` might be called before `handlePrimaryPointer`,
-    // which relies on `_initialButtons` to create `TapDownDetails`.
-    _initialButtons = event.buttons;
-  }
-
+  @protected
   @override
-  void handlePrimaryPointer(PointerEvent event) {
-    if (event is PointerUpEvent || event is PointerCancelEvent) {
-      resolve(GestureDisposition.rejected);
-      _reset();
-    } else if (event.buttons != _initialButtons) {
-      resolve(GestureDisposition.rejected);
-      stopTrackingPointer(primaryPointer);
-    }
+  bool isPointerAllowed(PointerDownEvent event) {
+    if (onAnyTapDown == null)
+      return false;
+    return super.isPointerAllowed(event);
   }
 
+  @protected
   @override
-  void resolve(GestureDisposition disposition) {
-    if (_wonArenaForPrimaryPointer && disposition == GestureDisposition.rejected) {
-      // This can happen if the gesture has been canceled. For example, when
-      // the pointer has exceeded the touch slop, the buttons have been changed,
-      // or if the recognizer is disposed.
-      assert(_sentTapDown);
-      _reset();
-    }
-    super.resolve(disposition);
-  }
-
-  @override
-  void didExceedDeadlineWithEvent(PointerDownEvent event) {
-    _checkDown(event.pointer);
+  void handleTapDown({PointerDownEvent down}) {
+    if (onAnyTapDown != null)
+      onAnyTapDown();
   }
 
+  @protected
   @override
-  void acceptGesture(int pointer) {
-    super.acceptGesture(pointer);
-    if (pointer == primaryPointer) {
-      _checkDown(pointer);
-      _wonArenaForPrimaryPointer = true;
-      _reset();
-    }
+  void handleTapUp({PointerDownEvent down, PointerUpEvent up}) {
+    // Do nothing.
   }
 
+  @protected
   @override
-  void rejectGesture(int pointer) {
-    super.rejectGesture(pointer);
-    if (pointer == primaryPointer) {
-      // Another gesture won the arena.
-      assert(state != GestureRecognizerState.possible);
-      _reset();
-    }
-  }
-
-  void _checkDown(int pointer) {
-    if (_sentTapDown)
-      return;
-    if (onAnyTapDown != null)
-      onAnyTapDown();
-    _sentTapDown = true;
-  }
-
-  void _reset() {
-    _sentTapDown = false;
-    _wonArenaForPrimaryPointer = false;
-    _initialButtons = null;
+  void handleTapCancel({PointerDownEvent down, PointerCancelEvent cancel, String reason}) {
+    // Do nothing.
   }
 
   @override
   String get debugDescription => 'any tap';
-
-  @override
-  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
-    super.debugFillProperties(properties);
-    properties.add(FlagProperty('wonArenaForPrimaryPointer', value: _wonArenaForPrimaryPointer, ifTrue: 'won arena'));
-    properties.add(FlagProperty('sentTapDown', value: _sentTapDown, ifTrue: 'sent tap down'));
-  }
 }
 
 class _ModalBarrierSemanticsDelegate extends SemanticsGestureDelegate {

packages/flutter/test/gestures/debug_test.dart

@@ -25,7 +25,7 @@ void main() {
     tap.addPointer(event);
     expect(log, hasLength(2));
     expect(log[0], equalsIgnoringHashCodes('Gesture arena 1    ❙ ★ Opening new gesture arena.'));
-    expect(log[1], equalsIgnoringHashCodes('Gesture arena 1    ❙ Adding: TapGestureRecognizer#00000(state: ready)'));
+    expect(log[1], equalsIgnoringHashCodes('Gesture arena 1    ❙ Adding: TapGestureRecognizer#00000(state: ready, button: 1)'));
     log.clear();
 
     GestureBinding.instance.gestureArena.close(1);
@@ -43,7 +43,7 @@ void main() {
     GestureBinding.instance.gestureArena.sweep(1);
     expect(log, hasLength(2));
     expect(log[0], equalsIgnoringHashCodes('Gesture arena 1    ❙ Sweeping with 1 member.'));
-    expect(log[1], equalsIgnoringHashCodes('Gesture arena 1    ❙ Winner: TapGestureRecognizer#00000(state: ready, finalPosition: Offset(12.0, 8.0))'));
+    expect(log[1], equalsIgnoringHashCodes('Gesture arena 1    ❙ Winner: TapGestureRecognizer#00000(state: ready, finalPosition: Offset(12.0, 8.0), button: 1)'));
     log.clear();
 
     tap.dispose();
@@ -83,9 +83,9 @@ void main() {
 
     GestureBinding.instance.gestureArena.sweep(1);
     expect(log, hasLength(3));
-    expect(log[0], equalsIgnoringHashCodes('TapGestureRecognizer#00000(state: ready, finalPosition: Offset(12.0, 8.0)) calling onTapDown callback.'));
-    expect(log[1], equalsIgnoringHashCodes('TapGestureRecognizer#00000(state: ready, won arena, finalPosition: Offset(12.0, 8.0), sent tap down) calling onTapUp callback.'));
-    expect(log[2], equalsIgnoringHashCodes('TapGestureRecognizer#00000(state: ready, won arena, finalPosition: Offset(12.0, 8.0), sent tap down) calling onTap callback.'));
+    expect(log[0], equalsIgnoringHashCodes('TapGestureRecognizer#00000(state: ready, finalPosition: Offset(12.0, 8.0), button: 1) calling onTapDown callback.'));
+    expect(log[1], equalsIgnoringHashCodes('TapGestureRecognizer#00000(state: ready, won arena, finalPosition: Offset(12.0, 8.0), button: 1, sent tap down) calling onTapUp callback.'));
+    expect(log[2], equalsIgnoringHashCodes('TapGestureRecognizer#00000(state: ready, won arena, finalPosition: Offset(12.0, 8.0), button: 1, sent tap down) calling onTap callback.'));
     log.clear();
 
     tap.dispose();
@@ -114,7 +114,7 @@ void main() {
     tap.addPointer(event);
     expect(log, hasLength(2));
     expect(log[0], equalsIgnoringHashCodes('Gesture arena 1    ❙ ★ Opening new gesture arena.'));
-    expect(log[1], equalsIgnoringHashCodes('Gesture arena 1    ❙ Adding: TapGestureRecognizer#00000(state: ready)'));
+    expect(log[1], equalsIgnoringHashCodes('Gesture arena 1    ❙ Adding: TapGestureRecognizer#00000(state: ready, button: 1)'));
     log.clear();
 
     GestureBinding.instance.gestureArena.close(1);
@@ -132,10 +132,10 @@ void main() {
     GestureBinding.instance.gestureArena.sweep(1);
     expect(log, hasLength(5));
     expect(log[0], equalsIgnoringHashCodes('Gesture arena 1    ❙ Sweeping with 1 member.'));
-    expect(log[1], equalsIgnoringHashCodes('Gesture arena 1    ❙ Winner: TapGestureRecognizer#00000(state: ready, finalPosition: Offset(12.0, 8.0))'));
-    expect(log[2], equalsIgnoringHashCodes('                   ❙ TapGestureRecognizer#00000(state: ready, finalPosition: Offset(12.0, 8.0)) calling onTapDown callback.'));
-    expect(log[3], equalsIgnoringHashCodes('                   ❙ TapGestureRecognizer#00000(state: ready, won arena, finalPosition: Offset(12.0, 8.0), sent tap down) calling onTapUp callback.'));
-    expect(log[4], equalsIgnoringHashCodes('                   ❙ TapGestureRecognizer#00000(state: ready, won arena, finalPosition: Offset(12.0, 8.0), sent tap down) calling onTap callback.'));
+    expect(log[1], equalsIgnoringHashCodes('Gesture arena 1    ❙ Winner: TapGestureRecognizer#00000(state: ready, finalPosition: Offset(12.0, 8.0), button: 1)'));
+    expect(log[2], equalsIgnoringHashCodes('                   ❙ TapGestureRecognizer#00000(state: ready, finalPosition: Offset(12.0, 8.0), button: 1) calling onTapDown callback.'));
+    expect(log[3], equalsIgnoringHashCodes('                   ❙ TapGestureRecognizer#00000(state: ready, won arena, finalPosition: Offset(12.0, 8.0), button: 1, sent tap down) calling onTapUp callback.'));
+    expect(log[4], equalsIgnoringHashCodes('                   ❙ TapGestureRecognizer#00000(state: ready, won arena, finalPosition: Offset(12.0, 8.0), button: 1, sent tap down) calling onTap callback.'));
     log.clear();
 
     tap.dispose();
@@ -152,7 +152,7 @@ void main() {
     expect(tap.toString(), equalsIgnoringHashCodes('TapGestureRecognizer#00000(state: ready)'));
     const PointerEvent event = PointerDownEvent(pointer: 1, position: Offset(10.0, 10.0));
     tap.addPointer(event);
-    tap.didExceedDeadlineWithEvent(event);
-    expect(tap.toString(), equalsIgnoringHashCodes('TapGestureRecognizer#00000(state: possible, sent tap down)'));
+    tap.didExceedDeadline();
+    expect(tap.toString(), equalsIgnoringHashCodes('TapGestureRecognizer#00000(state: possible, button: 1, sent tap down)'));
   });
 }

packages/flutter/test/gestures/tap_test.dart

@@ -140,7 +140,7 @@ void main() {
     tap.dispose();
   });
 
-  testGesture('Should not recognize two overlapping taps', (GestureTester tester) {
+  testGesture('Should not recognize two overlapping taps (FIFO)', (GestureTester tester) {
     final TapGestureRecognizer tap = TapGestureRecognizer();
 
     int tapsRecognized = 0;
@@ -174,6 +174,40 @@ void main() {
     tap.dispose();
   });
 
+  testGesture('Should not recognize two overlapping taps (FILO)', (GestureTester tester) {
+    final TapGestureRecognizer tap = TapGestureRecognizer();
+
+    int tapsRecognized = 0;
+    tap.onTap = () {
+      tapsRecognized++;
+    };
+
+    tap.addPointer(down1);
+    tester.closeArena(1);
+    expect(tapsRecognized, 0);
+    tester.route(down1);
+    expect(tapsRecognized, 0);
+
+    tap.addPointer(down2);
+    tester.closeArena(2);
+    expect(tapsRecognized, 0);
+    tester.route(down1);
+    expect(tapsRecognized, 0);
+
+
+    tester.route(up2);
+    expect(tapsRecognized, 0);
+    GestureBinding.instance.gestureArena.sweep(2);
+    expect(tapsRecognized, 0);
+
+    tester.route(up1);
+    expect(tapsRecognized, 1);
+    GestureBinding.instance.gestureArena.sweep(1);
+    expect(tapsRecognized, 1);
+
+    tap.dispose();
+  });
+
   testGesture('Distance cancels tap', (GestureTester tester) {
     final TapGestureRecognizer tap = TapGestureRecognizer();
 

packages/flutter/test/widgets/modal_barrier_test.dart

@@ -130,7 +130,7 @@ void main() {
     await tester.pump(); // begin transition
     await tester.pump(const Duration(seconds: 1)); // end transition
 
-    // Tap on the barrier to dismiss it
+    // Press the barrier to dismiss it
     await tester.press(find.byKey(const ValueKey<String>('barrier')));
     await tester.pump(); // begin transition
     await tester.pump(const Duration(seconds: 1)); // end transition
@@ -155,7 +155,7 @@ void main() {
     await tester.pump(); // begin transition
     await tester.pump(const Duration(seconds: 1)); // end transition
 
-    // Tap on the barrier to dismiss it
+    // Press the barrier to dismiss it
     await tester.press(find.byKey(const ValueKey<String>('barrier')), buttons: kSecondaryButton);
     await tester.pump(); // begin transition
     await tester.pump(const Duration(seconds: 1)); // end transition
@@ -164,6 +164,31 @@ void main() {
       reason: 'The route should have been dismissed by tapping the barrier.');
   });
 
+  testWidgets('ModalBarrier may pop the Navigator when competing with other gestures', (WidgetTester tester) async {
+    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
+      '/': (BuildContext context) => FirstWidget(),
+      '/modal': (BuildContext context) => SecondWidgetWithCompetence (),
+    };
+
+    await tester.pumpWidget(MaterialApp(routes: routes));
+
+    // Initially the barrier is not visible
+    expect(find.byKey(const ValueKey<String>('barrier')), findsNothing);
+
+    // Tapping on X routes to the barrier
+    await tester.tap(find.text('X'));
+    await tester.pump(); // begin transition
+    await tester.pump(const Duration(seconds: 1)); // end transition
+
+    // Tap on the barrier to dismiss it
+    await tester.tap(find.byKey(const ValueKey<String>('barrier')));
+    await tester.pump(); // begin transition
+    await tester.pump(const Duration(seconds: 1)); // end transition
+
+    expect(find.byKey(const ValueKey<String>('barrier')), findsNothing,
+      reason: 'The route should have been dismissed by tapping the barrier.');
+  });
+
   testWidgets('ModalBarrier does not pop the Navigator with a WillPopScope that returns false', (WidgetTester tester) async {
     bool willPopCalled = false;
     final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
@@ -316,3 +341,22 @@ class SecondWidget extends StatelessWidget {
     );
   }
 }
+
+class SecondWidgetWithCompetence extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return Stack(
+      children: <Widget>[
+        const ModalBarrier(
+          key: ValueKey<String>('barrier'),
+          dismissible: true,
+        ),
+        GestureDetector(
+          onVerticalDragStart: (_) {},
+          behavior: HitTestBehavior.translucent,
+          child: Container(),
+        )
+      ],
+    );
+  }
+}