Restore previous tap behaviors: no timeout, one pointer

Don't use a timeout to cancel tap tracking. Track only one primary pointer
and ignore non-primary pointers. Update tests to reflect desired behaviors.

Fixes #1779, #1780, #1781.

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

@@ -6,7 +6,7 @@
 // https://github.com/android/platform_frameworks_base/blob/master/core/java/android/view/ViewConfiguration.java
 
 const Duration kLongPressTimeout = const Duration(milliseconds: 500);
-const Duration kTapTimeout = const Duration(milliseconds: 100);
+const Duration kPressTimeout = const Duration(milliseconds: 100);
 const Duration kJumpTapTimeout = const Duration(milliseconds: 500);
 const Duration kDoubleTapTimeout = const Duration(milliseconds: 300);
 const Duration kDoubleTapMinTime = const Duration(milliseconds: 40);

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

@@ -52,7 +52,6 @@ class DoubleTapGestureRecognizer extends DisposableArenaMember {
       entry: GestureArena.instance.add(event.pointer, this)
     );
     _trackers[event.pointer] = tracker;
-    tracker.startTimer(() => _reject(tracker));
     tracker.startTrackingPointer(router, handleEvent);
   }
 
@@ -145,7 +144,6 @@ class DoubleTapGestureRecognizer extends DisposableArenaMember {
   }
 
   void _freezeTracker(TapTracker tracker) {
-    tracker.stopTimer();
     tracker.stopTrackingPointer(router, handleEvent);
   }
 

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

@@ -12,7 +12,7 @@ typedef void GestureLongPressCallback();
 
 class LongPressGestureRecognizer extends PrimaryPointerGestureRecognizer {
   LongPressGestureRecognizer({ PointerRouter router, this.onLongPress })
-    : super(router: router, deadline: kTapTimeout + kLongPressTimeout);
+    : super(router: router, deadline: kLongPressTimeout);
 
   GestureLongPressCallback onLongPress;
 

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

@@ -11,7 +11,7 @@ typedef void GestureShowPressCallback();
 
 class ShowPressGestureRecognizer extends PrimaryPointerGestureRecognizer {
   ShowPressGestureRecognizer({ PointerRouter router, this.onShowPress })
-    : super(router: router, deadline: kTapTimeout);
+    : super(router: router, deadline: kPressTimeout);
 
   GestureShowPressCallback onShowPress;
 

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

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:async';
 import 'dart:ui' as ui;
 
 import 'arena.dart';
@@ -13,9 +12,56 @@ import 'recognizer.dart';
 
 typedef void GestureTapCallback();
 
-enum TapResolution {
-  tap,
-  cancel
+/// TapGestureRecognizer is a tap recognizer that tracks only one primary
+/// pointer per gesture. That is, during tap recognition, extra pointer events
+/// are ignored: down-1, down-2, up-1, up-2 produces only one tap on up-1.
+class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
+  TapGestureRecognizer({ PointerRouter router, this.onTap })
+    : super(router: router);
+
+  GestureTapCallback onTap;
+  GestureTapCallback onTapDown;
+  GestureTapCallback onTapCancel;
+
+  bool _wonArena = false;
+  bool _didTap = false;
+
+  void handlePrimaryPointer(PointerInputEvent event) {
+    if (event.type == 'pointerdown') {
+      if (onTapDown != null)
+        onTapDown();
+    } else if (event.type == 'pointerup') {
+      _didTap = true;
+      _check();
+    }
+  }
+
+  void acceptGesture(int pointer) {
+    super.acceptGesture(pointer);
+    if (pointer == primaryPointer) {
+      _wonArena = true;
+      _check();
+    }
+  }
+
+  void rejectGesture(int pointer) {
+    super.rejectGesture(pointer);
+    if (pointer == primaryPointer) {
+      assert(state == GestureRecognizerState.defunct);
+      _wonArena = false;
+      _didTap = false;
+      if (onTapCancel != null)
+        onTapCancel();
+    }
+  }
+
+  void _check() {
+    if (_wonArena && _didTap) {
+      resolve(GestureDisposition.accepted);
+      if (onTap != null)
+        onTap();
+    }
+  }
 }
 
 /// TapTracker helps track individual tap sequences as part of a
@@ -33,18 +79,6 @@ class TapTracker {
   GestureArenaEntry entry;
   ui.Point _initialPosition;
   bool _isTrackingPointer;
-  Timer _timer;
-
-  void startTimer(void callback()) {
-    _timer ??= new Timer(kTapTimeout, callback);
-  }
-
-  void stopTimer() {
-    if (_timer != null) {
-      _timer.cancel();
-      _timer = null;
-    }
-  }
 
   void startTrackingPointer(PointerRouter router, PointerRoute route) {
     if (!_isTrackingPointer) {
@@ -67,6 +101,11 @@ class TapTracker {
 
 }
 
+enum TapResolution {
+  tap,
+  cancel
+}
+
 /// TapGesture represents a full gesture resulting from a single tap
 /// sequence. Tap gestures are passive, meaning that they will not
 /// pre-empt any other arena member in play.
@@ -77,11 +116,10 @@ class TapGesture extends TapTracker {
     entry = GestureArena.instance.add(event.pointer, gestureRecognizer);
     _wonArena = false;
     _didTap = false;
-    startTimer(cancel);
     startTrackingPointer(gestureRecognizer.router, handleEvent);
   }
 
-  TapGestureRecognizer gestureRecognizer;
+  MultiTapGestureRecognizer gestureRecognizer;
 
   bool _wonArena;
   bool _didTap;
@@ -93,7 +131,6 @@ class TapGesture extends TapTracker {
     } else if (event.type == 'pointercancel') {
       cancel();
     } else if (event.type == 'pointerup') {
-      stopTimer();
       stopTrackingPointer(gestureRecognizer.router, handleEvent);
       _didTap = true;
       _check();
@@ -106,7 +143,6 @@ class TapGesture extends TapTracker {
   }
 
   void reject() {
-    stopTimer();
     stopTrackingPointer(gestureRecognizer.router, handleEvent);
     gestureRecognizer._resolveTap(pointer, TapResolution.cancel);
   }
@@ -127,8 +163,12 @@ class TapGesture extends TapTracker {
 
 }
 
-class TapGestureRecognizer extends DisposableArenaMember {
-  TapGestureRecognizer({ this.router, this.onTap, this.onTapDown, this.onTapCancel });
+/// MultiTapGestureRecognizer is a tap recognizer that treats taps
+/// independently. That is, each pointer sequence that could resolve to a tap
+/// does so independently of others: down-1, down-2, up-1, up-2 produces two
+/// taps, on up-1 and up-2.
+class MultiTapGestureRecognizer extends DisposableArenaMember {
+  MultiTapGestureRecognizer({ this.router, this.onTap, this.onTapDown, this.onTapCancel });
 
   PointerRouter router;
   GestureTapCallback onTap;

packages/flutter/lib/src/material/ink_well.dart

@@ -35,8 +35,8 @@ class _InkSplash {
       duration: new Duration(milliseconds: (_targetRadius / _kSplashUnconfirmedVelocity).floor())
     )..addListener(_handleRadiusChange);
 
-    // Wait kTapTimeout to avoid creating tiny splashes during scrolls.
-    _startTimer = new Timer(kTapTimeout, _play);
+    // Wait kPressTimeout to avoid creating tiny splashes during scrolls.
+    _startTimer = new Timer(kPressTimeout, _play);
   }
 
   final Point position;

packages/unit/test/gestures/double_tap_test.dart

@@ -223,7 +223,7 @@ void main() {
     tap.dispose();
   });
 
-  test('Intra-tap delay cancels double tap', () {
+  test('Intra-tap delay does not cancel double tap', () {
     PointerRouter router = new PointerRouter();
     DoubleTapGestureRecognizer tap = new DoubleTapGestureRecognizer(router: router);
 
@@ -252,9 +252,9 @@ void main() {
       expect(doubleTapRecognized, isFalse);
 
       router.route(up2);
-      expect(doubleTapRecognized, isFalse);
+      expect(doubleTapRecognized, isTrue);
       GestureArena.instance.sweep(2);
-      expect(doubleTapRecognized, isFalse);
+      expect(doubleTapRecognized, isTrue);
     });
 
     tap.dispose();

packages/unit/test/gestures/tap_test.dart

@@ -84,7 +84,7 @@ void main() {
     tap.dispose();
   });
 
-  test('Should recognize two overlapping taps', () {
+  test('Should not recognize two overlapping taps', () {
     PointerRouter router = new PointerRouter();
     TapGestureRecognizer tap = new TapGestureRecognizer(router: router);
 
@@ -112,9 +112,9 @@ void main() {
     expect(tapsRecognized, 1);
 
     router.route(up2);
-    expect(tapsRecognized, 2);
+    expect(tapsRecognized, 1);
     GestureArena.instance.sweep(2);
-    expect(tapsRecognized, 2);
+    expect(tapsRecognized, 1);
 
     tap.dispose();
   });
@@ -144,7 +144,7 @@ void main() {
     tap.dispose();
   });
 
-  test('Timeout cancels tap', () {
+  test('Timeout does not cancel tap', () {
     PointerRouter router = new PointerRouter();
     TapGestureRecognizer tap = new TapGestureRecognizer(router: router);
 
@@ -163,9 +163,9 @@ void main() {
       async.elapse(new Duration(milliseconds: 500));
       expect(tapRecognized, isFalse);
       router.route(up1);
-      expect(tapRecognized, isFalse);
+      expect(tapRecognized, isTrue);
       GestureArena.instance.sweep(1);
-      expect(tapRecognized, isFalse);
+      expect(tapRecognized, isTrue);
     });
 
     tap.dispose();