Add buttons to gestures (#30339)

* Callbacks of tap, long press, drag, and double tap GR respond to only primary events.
* Add "secondary" callbacks to tap.
* Recognizers only compete on events if there are any related callbacks.
* Add "kSecondaryButton" constant.

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

@@ -8,22 +8,35 @@ import 'package:flutter/foundation.dart';
 
 export 'dart:ui' show Offset, PointerDeviceKind;
 
-/// The bit of [PointerEvent.buttons] that corresponds to the "primary
-/// action" on any device.
+/// The bit of [PointerEvent.buttons] that corresponds to a cross-device
+/// behavior of "primary operation".
 ///
-/// More specifially,
+/// More specifially, it includes:
 ///
-///  * For touch screen, it's when the pointer contacts the screen.
-///  * For stylus and inverted stylus, it's when the pen contacts the screen.
-///  * For mouse, it's when the primary button is pressed.
+///  * [kTouchContact]: The pointer contacts the touch screen.
+///  * [kStylusContact]: The stylus contacts the screen.
+///  * [kPrimaryMouseButton]: The primary mouse button.
 ///
 /// See also:
 ///
-///  * [kTouchContact]: an alias of this constant when used by touch screen.
-///  * [kStylusContact]: an alias of this constant when used by stylus.
-///  * [kPrimaryMouseButton]: an alias of this constant when used by mouse.
+///  * [kSecondaryButton], which describes a cross-device behavior of
+///    "secondary operation".
 const int kPrimaryButton = 0x01;
 
+/// The bit of [PointerEvent.buttons] that corresponds to a cross-device
+/// behavior of "secondary operation".
+///
+/// It is equivalent to:
+///
+///  * [kPrimaryStylusButton]: The stylus contacts the screen.
+///  * [kSecondaryMouseButton]: The primary mouse button.
+///
+/// See also:
+///
+///  * [kPrimaryButton], which describes a cross-device behavior of
+///    "primary operation".
+const int kSecondaryButton = 0x02;
+
 /// The bit of [PointerEvent.buttons] that corresponds to the primary mouse button.
 ///
 /// The primary mouse button is typically the left button on the top of the
@@ -31,28 +44,40 @@ const int kPrimaryButton = 0x01;
 ///
 /// See also:
 ///
-///  * [kTouchContact]: an alias of this constant when used by touch screen.
+///  * [kPrimaryButton], which has the same value but describes its cross-device
+///    concept.
 const int kPrimaryMouseButton = kPrimaryButton;
 
 /// The bit of [PointerEvent.buttons] that corresponds to the secondary mouse button.
 ///
 /// The secondary mouse button is typically the right button on the top of the
 /// mouse but can be reconfigured to be a different physical button.
-const int kSecondaryMouseButton = 0x02;
+///
+/// See also:
+///
+///  * [kSecondaryButton], which has the same value but describes its cross-device
+///    concept.
+const int kSecondaryMouseButton = kSecondaryButton;
 
 /// The bit of [PointerEvent.buttons] that corresponds to when a stylus
 /// contacting the screen.
 ///
 /// See also:
 ///
-///  * [kPrimaryButton]: an alias of this constant for any device.
+///  * [kPrimaryButton], which has the same value but describes its cross-device
+///    concept.
 const int kStylusContact = kPrimaryButton;
 
 /// The bit of [PointerEvent.buttons] that corresponds to the primary stylus button.
 ///
 /// The primary stylus button is typically the top of the stylus and near the
 /// tip but can be reconfigured to be a different physical button.
-const int kPrimaryStylusButton = 0x02;
+///
+/// See also:
+///
+///  * [kSecondaryButton], which has the same value but describes its cross-device
+///    concept.
+const int kPrimaryStylusButton = kSecondaryButton;
 
 /// The bit of [PointerEvent.buttons] that corresponds to the middle mouse button.
 ///
@@ -84,7 +109,8 @@ const int kForwardMouseButton = 0x10;
 ///
 /// See also:
 ///
-///  * [kPrimaryButton]: an alias of this constant for any device.
+///  * [kPrimaryButton], which has the same value but describes its cross-device
+///    concept.
 const int kTouchContact = kPrimaryButton;
 
 /// The bit of [PointerEvent.buttons] that corresponds to the nth mouse button.
@@ -104,6 +130,47 @@ int nthMouseButton(int number) => (kPrimaryMouseButton << (number - 1)) & kMaxUn
 /// for some stylus buttons.
 int nthStylusButton(int number) => (kPrimaryStylusButton << (number - 1)) & kMaxUnsignedSMI;
 
+/// Returns the button of `buttons` with the smallest integer.
+///
+/// The `buttons` parameter is a bitfield where each set bit represents a button.
+/// This function returns the set bit closest to the least significant bit.
+///
+/// It returns zero when `buttons` is zero.
+///
+/// Example:
+///
+/// ```dart
+///   assert(rightmostButton(0x1) == 0x1);
+///   assert(rightmostButton(0x11) == 0x1);
+///   assert(rightmostButton(0) == 0);
+/// ```
+///
+/// See also:
+///
+///   * [isSingleButton], which checks if a `buttons` contains exactly one button.
+int smallestButton(int buttons) => buttons & (-buttons);
+
+/// Returns whether `buttons` contains one and only one button.
+///
+/// The `buttons` parameter is a bitfield where each set bit represents a button.
+/// This function returns whether there is only one set bit in the given integer.
+///
+/// It returns false when `buttons` is zero.
+///
+/// Example:
+///
+/// ```dart
+///   assert(isSingleButton(0x1) == true);
+///   assert(isSingleButton(0x11) == false);
+///   assert(isSingleButton(0) == false);
+/// ```
+///
+/// See also:
+///
+///   * [smallestButton], which returns the button in a `buttons` bitfield with
+///     the smallest integer button.
+bool isSingleButton(int buttons) => buttons != 0 && (smallestButton(buttons) == buttons);
+
 /// Base class for touch, stylus, or mouse events.
 ///
 /// Pointer events operate in the coordinate space of the screen, scaled to

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

@@ -109,6 +109,10 @@ class LongPressEndDetails {
 /// until it's recognized. Once the gesture is accepted, the finger can be
 /// moved, triggering [onLongPressMoveUpdate] callbacks, unless the
 /// [postAcceptSlopTolerance] constructor argument is specified.
+///
+/// [LongPressGestureRecognizer] competes on pointer events of [kPrimaryButton]
+/// only when it has at least one non-null callback. If it has no callbacks, it
+/// is a no-op.
 class LongPressGestureRecognizer extends PrimaryPointerGestureRecognizer {
   /// Creates a long-press gesture recognizer.
   ///
@@ -133,89 +137,159 @@ class LongPressGestureRecognizer extends PrimaryPointerGestureRecognizer {
   );
 
   bool _longPressAccepted = false;
-
   Offset _longPressOrigin;
+  // The buttons sent by `PointerDownEvent`. If a `PointerMoveEvent` comes with a
+  // different set of buttons, the gesture is canceled.
+  int _initialButtons;
 
-  /// Called when a long press gesture has been recognized.
+  /// Called when a long press gesture by a primary button has been recognized.
   ///
   /// See also:
   ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   ///  * [onLongPressStart], which has the same timing but has data for the
   ///    press location.
   GestureLongPressCallback onLongPress;
 
-  /// Callback for long press start with gesture location.
+  /// Called when a long press gesture by a primary button has been recognized.
   ///
   /// See also:
   ///
-  ///  * [onLongPress], which has the same timing but without the location data.
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [onLongPress], which has the same timing but without details.
+  ///  * [LongPressStartDetails], which is passed as an argument to this callback.
   GestureLongPressStartCallback onLongPressStart;
 
-  /// Callback for moving the gesture after the lang press is recognized.
+  /// Called when moving after the long press by a primary button is recognized.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [LongPressMoveUpdateDetails], which is passed as an argument to this
+  ///    callback.
   GestureLongPressMoveUpdateCallback onLongPressMoveUpdate;
 
-  /// Called when the pointer stops contacting the screen after the long-press.
+  /// Called when the pointer stops contacting the screen after a long-press
+  /// by a primary button.
   ///
   /// See also:
   ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   ///  * [onLongPressEnd], which has the same timing but has data for the up
   ///    gesture location.
   GestureLongPressUpCallback onLongPressUp;
 
-  /// Callback for long press end with gesture location.
+  /// Called when the pointer stops contacting the screen after a long-press
+  /// by a primary button.
   ///
   /// See also:
   ///
-  ///  * [onLongPressUp], which has the same timing but without the location data.
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [onLongPressUp], which has the same timing, but without details.
+  ///  * [LongPressEndDetails], which is passed as an argument to this
+  ///    callback.
   GestureLongPressEndCallback onLongPressEnd;
 
+  @override
+  bool isPointerAllowed(PointerDownEvent event) {
+    switch (event.buttons) {
+      case kPrimaryButton:
+        if (onLongPressStart == null &&
+            onLongPress == null &&
+            onLongPressMoveUpdate == null &&
+            onLongPressEnd == null &&
+            onLongPressUp == null)
+          return false;
+        break;
+      default:
+        return false;
+    }
+    return super.isPointerAllowed(event);
+  }
+
   @override
   void didExceedDeadline() {
+    // Exceeding the deadline puts the gesture in the accepted state.
     resolve(GestureDisposition.accepted);
     _longPressAccepted = true;
     super.acceptGesture(primaryPointer);
-    if (onLongPress != null) {
-      invokeCallback<void>('onLongPress', onLongPress);
-    }
-    if (onLongPressStart != null) {
-      invokeCallback<void>('onLongPressStart', () {
-        onLongPressStart(LongPressStartDetails(
-          globalPosition: _longPressOrigin,
-        ));
-      });
-    }
+    _checkLongPressStart();
   }
 
   @override
   void handlePrimaryPointer(PointerEvent event) {
     if (event is PointerUpEvent) {
       if (_longPressAccepted == true) {
-        if (onLongPressUp != null) {
-          invokeCallback<void>('onLongPressUp', onLongPressUp);
-        }
-        if (onLongPressEnd != null) {
-          invokeCallback<void>('onLongPressEnd', () {
-            onLongPressEnd(LongPressEndDetails(
-              globalPosition: event.position,
-            ));
-          });
-        }
-        _longPressAccepted = false;
+        _checkLongPressEnd(event);
       } else {
+        // Pointer is lifted before timeout.
         resolve(GestureDisposition.rejected);
       }
-    } else if (event is PointerDownEvent || event is PointerCancelEvent) {
+      _reset();
+    } else if (event is PointerCancelEvent) {
+      _reset();
+    } else if (event is PointerDownEvent) {
       // The first touch.
-      _longPressAccepted = false;
       _longPressOrigin = event.position;
-    } else if (event is PointerMoveEvent && _longPressAccepted && onLongPressMoveUpdate != null) {
-      invokeCallback<void>('onLongPressMoveUpdate', () {
-        onLongPressMoveUpdate(LongPressMoveUpdateDetails(
-          globalPosition: event.position,
-          offsetFromOrigin: event.position - _longPressOrigin,
-        ));
-      });
+      _initialButtons = event.buttons;
+    } else if (event is PointerMoveEvent) {
+      if (event.buttons != _initialButtons) {
+        resolve(GestureDisposition.rejected);
+        stopTrackingPointer(primaryPointer);
+      } else if (_longPressAccepted) {
+        _checkLongPressMoveUpdate(event);
+      }
+    }
+  }
+
+  void _checkLongPressStart() {
+    assert(_initialButtons == kPrimaryButton);
+    final LongPressStartDetails details = LongPressStartDetails(
+      globalPosition: _longPressOrigin,
+    );
+    if (onLongPressStart != null)
+      invokeCallback<void>('onLongPressStart',
+        () => onLongPressStart(details));
+    if (onLongPress != null)
+      invokeCallback<void>('onLongPress', onLongPress);
+  }
+
+  void _checkLongPressMoveUpdate(PointerEvent event) {
+    assert(_initialButtons == kPrimaryButton);
+    final LongPressMoveUpdateDetails details = LongPressMoveUpdateDetails(
+      globalPosition: event.position,
+      offsetFromOrigin: event.position - _longPressOrigin,
+    );
+    if (onLongPressMoveUpdate != null)
+      invokeCallback<void>('onLongPressMoveUpdate',
+        () => onLongPressMoveUpdate(details));
+  }
+
+  void _checkLongPressEnd(PointerEvent event) {
+    assert(_initialButtons == kPrimaryButton);
+    final LongPressEndDetails details = LongPressEndDetails(
+      globalPosition: event.position,
+    );
+    if (onLongPressEnd != null)
+      invokeCallback<void>('onLongPressEnd', () => onLongPressEnd(details));
+    if (onLongPressUp != null)
+      invokeCallback<void>('onLongPressUp', onLongPressUp);
+  }
+
+  void _reset() {
+    _longPressAccepted = false;
+    _longPressOrigin = null;
+    _initialButtons = null;
+  }
+
+  @override
+  void resolve(GestureDisposition disposition) {
+    if (_longPressAccepted && disposition == GestureDisposition.rejected) {
+      // This can happen if the gesture has been canceled. For example when
+      // the buttons have changed.
+      _reset();
     }
+    super.resolve(disposition);
   }
 
   @override

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

@@ -43,6 +43,10 @@ typedef GestureDragCancelCallback = void Function();
 /// consider using one of its subclasses to recognize specific types for drag
 /// gestures.
 ///
+/// [DragGestureRecognizer] competes on pointer events of [kPrimaryButton]
+/// only when it has at least one non-null callback. If it has no callbacks, it
+/// is a no-op.
+///
 /// See also:
 ///
 ///  * [HorizontalDragGestureRecognizer], for left and right drags.
@@ -84,13 +88,20 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
   /// at (510.0, 500.0).
   DragStartBehavior dragStartBehavior;
 
-  /// A pointer has contacted the screen and might begin to move.
+  /// A pointer has contacted the screen with a primary button and might begin
+  /// to move.
   ///
   /// The position of the pointer is provided in the callback's `details`
   /// argument, which is a [DragDownDetails] object.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [DragDownDetails], which is passed as an argument to this callback.
   GestureDragDownCallback onDown;
 
-  /// A pointer has contacted the screen and has begun to move.
+  /// A pointer has contacted the screen with a primary button and has begun to
+  /// move.
   ///
   /// The position of the pointer is provided in the callback's `details`
   /// argument, which is a [DragStartDetails] object.
@@ -99,23 +110,43 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
   /// called on the initial touch down, if set to [DragStartBehavior.down] or
   /// when the drag gesture is first detected, if set to
   /// [DragStartBehavior.start].
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [DragStartDetails], which is passed as an argument to this callback.
   GestureDragStartCallback onStart;
 
-  /// A pointer that is in contact with the screen and moving has moved again.
+  /// A pointer that is in contact with the screen with a primary button and
+  /// moving has moved again.
   ///
   /// The distance travelled by the pointer since the last update is provided in
   /// the callback's `details` argument, which is a [DragUpdateDetails] object.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [DragUpdateDetails], which is passed as an argument to this callback.
   GestureDragUpdateCallback onUpdate;
 
-  /// A pointer that was previously in contact with the screen and moving is no
-  /// longer in contact with the screen and was moving at a specific velocity
-  /// when it stopped contacting the screen.
+  /// A pointer that was previously in contact with the screen with a primary
+  /// button and moving is no longer in contact with the screen and was moving
+  /// at a specific velocity when it stopped contacting the screen.
   ///
   /// The velocity is provided in the callback's `details` argument, which is a
   /// [DragEndDetails] object.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [DragEndDetails], which is passed as an argument to this callback.
   GestureDragEndCallback onEnd;
 
   /// The pointer that previously triggered [onDown] did not complete.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   GestureDragCancelCallback onCancel;
 
   /// The minimum distance an input pointer drag must have moved to
@@ -141,6 +172,9 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
   Offset _initialPosition;
   Offset _pendingDragOffset;
   Duration _lastPendingEventTimestamp;
+  // The buttons sent by `PointerDownEvent`. If a `PointerMoveEvent` comes with a
+  // different set of buttons, the gesture is canceled.
+  int _initialButtons;
 
   bool _isFlingGesture(VelocityEstimate estimate);
   Offset _getDeltaForDetails(Offset delta);
@@ -149,6 +183,30 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
 
   final Map<int, VelocityTracker> _velocityTrackers = <int, VelocityTracker>{};
 
+  @override
+  bool isPointerAllowed(PointerEvent event) {
+    if (_initialButtons == null) {
+      switch (event.buttons) {
+        case kPrimaryButton:
+          if (onDown == null &&
+              onStart == null &&
+              onUpdate == null &&
+              onEnd == null &&
+              onCancel == null)
+            return false;
+          break;
+        default:
+          return false;
+      }
+    } else {
+      // There can be multiple drags simultaneously. Their effects are combined.
+      if (event.buttons != _initialButtons) {
+        return false;
+      }
+    }
+    return super.isPointerAllowed(event);
+  }
+
   @override
   void addAllowedPointer(PointerEvent event) {
     startTrackingPointer(event.pointer);
@@ -156,10 +214,10 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
     if (_state == _DragState.ready) {
       _state = _DragState.possible;
       _initialPosition = event.position;
+      _initialButtons = event.buttons;
       _pendingDragOffset = Offset.zero;
       _lastPendingEventTimestamp = event.timeStamp;
-      if (onDown != null)
-        invokeCallback<void>('onDown', () => onDown(DragDownDetails(globalPosition: _initialPosition)));
+      _checkDown();
     } else if (_state == _DragState.accepted) {
       resolve(GestureDisposition.accepted);
     }
@@ -176,16 +234,19 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
     }
 
     if (event is PointerMoveEvent) {
+      if (event.buttons != _initialButtons) {
+        resolve(GestureDisposition.rejected);
+        stopTrackingPointer(event.pointer);
+        return;
+      }
       final Offset delta = event.delta;
       if (_state == _DragState.accepted) {
-        if (onUpdate != null) {
-          invokeCallback<void>('onUpdate', () => onUpdate(DragUpdateDetails(
-            sourceTimeStamp: event.timeStamp,
-            delta: _getDeltaForDetails(delta),
-            primaryDelta: _getPrimaryValueFromOffset(delta),
-            globalPosition: event.position,
-          )));
-        }
+        _checkUpdate(
+          sourceTimeStamp: event.timeStamp,
+          delta: _getDeltaForDetails(delta),
+          primaryDelta: _getPrimaryValueFromOffset(delta),
+          globalPosition: event.position,
+        );
       } else {
         _pendingDragOffset += delta;
         _lastPendingEventTimestamp = event.timeStamp;
@@ -214,19 +275,14 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
       }
       _pendingDragOffset = Offset.zero;
       _lastPendingEventTimestamp = null;
-      if (onStart != null) {
-        invokeCallback<void>('onStart', () => onStart(DragStartDetails(
-          sourceTimeStamp: timestamp,
-          globalPosition: _initialPosition,
-        )));
-      }
-      if (updateDelta != Offset.zero && onUpdate != null) {
-        invokeCallback<void>('onUpdate', () => onUpdate(DragUpdateDetails(
+      _checkStart(timestamp);
+      if (updateDelta != Offset.zero) {
+        _checkUpdate(
           sourceTimeStamp: timestamp,
           delta: updateDelta,
           primaryDelta: _getPrimaryValueFromOffset(updateDelta),
           globalPosition: _initialPosition + updateDelta, // Only adds delta for down behaviour
-        )));
+        );
       }
     }
   }
@@ -238,41 +294,101 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
 
   @override
   void didStopTrackingLastPointer(int pointer) {
-    if (_state == _DragState.possible) {
-      resolve(GestureDisposition.rejected);
-      _state = _DragState.ready;
-      if (onCancel != null)
-        invokeCallback<void>('onCancel', onCancel);
-      return;
+    assert(_state != _DragState.ready);
+    switch(_state) {
+      case _DragState.ready:
+        break;
+
+      case _DragState.possible:
+        resolve(GestureDisposition.rejected);
+        _checkCancel();
+        break;
+
+      case _DragState.accepted:
+        _checkEnd(pointer);
+        break;
     }
-    final bool wasAccepted = _state == _DragState.accepted;
+    _velocityTrackers.clear();
+    _initialButtons = null;
     _state = _DragState.ready;
-    if (wasAccepted && onEnd != null) {
-      final VelocityTracker tracker = _velocityTrackers[pointer];
-      assert(tracker != null);
+  }
 
-      final VelocityEstimate estimate = tracker.getVelocityEstimate();
-      if (estimate != null && _isFlingGesture(estimate)) {
-        final Velocity velocity = Velocity(pixelsPerSecond: estimate.pixelsPerSecond)
-          .clampMagnitude(minFlingVelocity ?? kMinFlingVelocity, maxFlingVelocity ?? kMaxFlingVelocity);
-        invokeCallback<void>('onEnd', () => onEnd(DragEndDetails(
-          velocity: velocity,
-          primaryVelocity: _getPrimaryValueFromOffset(velocity.pixelsPerSecond),
-        )), debugReport: () {
-          return '$estimate; fling at $velocity.';
-        });
-      } else {
-        invokeCallback<void>('onEnd', () => onEnd(DragEndDetails(
-          velocity: Velocity.zero,
-          primaryVelocity: 0.0,
-        )), debugReport: () {
-          if (estimate == null)
-            return 'Could not estimate velocity.';
-          return '$estimate; judged to not be a fling.';
-        });
-      }
+  void _checkDown() {
+    assert(_initialButtons == kPrimaryButton);
+    final DragDownDetails details = DragDownDetails(
+      globalPosition: _initialPosition,
+    );
+    if (onDown != null)
+      invokeCallback<void>('onDown', () => onDown(details));
+  }
+
+  void _checkStart(Duration timestamp) {
+    assert(_initialButtons == kPrimaryButton);
+    final DragStartDetails details = DragStartDetails(
+      sourceTimeStamp: timestamp,
+      globalPosition: _initialPosition,
+    );
+    if (onStart != null)
+      invokeCallback<void>('onStart', () => onStart(details));
+  }
+
+  void _checkUpdate({
+    Duration sourceTimeStamp,
+    Offset delta,
+    double primaryDelta,
+    Offset globalPosition,
+  }) {
+    assert(_initialButtons == kPrimaryButton);
+    final DragUpdateDetails details = DragUpdateDetails(
+      sourceTimeStamp: sourceTimeStamp,
+      delta: delta,
+      primaryDelta: primaryDelta,
+      globalPosition: globalPosition,
+    );
+    if (onUpdate != null)
+      invokeCallback<void>('onUpdate', () => onUpdate(details));
+  }
+
+  void _checkEnd(int pointer) {
+    assert(_initialButtons == kPrimaryButton);
+    if (onEnd == null)
+      return;
+
+    final VelocityTracker tracker = _velocityTrackers[pointer];
+    assert(tracker != null);
+
+    DragEndDetails details;
+    void Function() debugReport;
+
+    final VelocityEstimate estimate = tracker.getVelocityEstimate();
+    if (estimate != null && _isFlingGesture(estimate)) {
+      final Velocity velocity = Velocity(pixelsPerSecond: estimate.pixelsPerSecond)
+        .clampMagnitude(minFlingVelocity ?? kMinFlingVelocity, maxFlingVelocity ?? kMaxFlingVelocity);
+      details = DragEndDetails(
+        velocity: velocity,
+        primaryVelocity: _getPrimaryValueFromOffset(velocity.pixelsPerSecond),
+      );
+      debugReport = () {
+        return '$estimate; fling at $velocity.';
+      };
+    } else {
+      details = DragEndDetails(
+        velocity: Velocity.zero,
+        primaryVelocity: 0.0,
+      );
+      debugReport = () {
+        if (estimate == null)
+          return 'Could not estimate velocity.';
+        return '$estimate; judged to not be a fling.';
+      };
     }
-    _velocityTrackers.clear();
+    invokeCallback<void>('onEnd', () => onEnd(details), debugReport: debugReport);
+  }
+
+  void _checkCancel() {
+    assert(_initialButtons == kPrimaryButton);
+    if (onCancel != null)
+      invokeCallback<void>('onCancel', onCancel);
   }
 
   @override

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

@@ -16,6 +16,10 @@ import 'tap.dart';
 
 /// Signature for callback when the user has tapped the screen at the same
 /// location twice in quick succession.
+///
+/// See also:
+///
+///  * [GestureDetector.onDoubleTap], which matches this signature.
 typedef GestureDoubleTapCallback = void Function();
 
 /// Signature used by [MultiTapGestureRecognizer] for when a pointer that might
@@ -60,13 +64,16 @@ class _TapTracker {
     @required Duration doubleTapMinTime,
   }) : assert(doubleTapMinTime != null),
        assert(event != null),
+       assert(event.buttons != null),
        pointer = event.pointer,
        _initialPosition = event.position,
+       initialButtons = event.buttons,
        _doubleTapMinTimeCountdown = _CountdownZoned(duration: doubleTapMinTime);
 
   final int pointer;
   final GestureArenaEntry entry;
   final Offset _initialPosition;
+  final int initialButtons;
   final _CountdownZoned _doubleTapMinTimeCountdown;
 
   bool _isTrackingPointer = false;
@@ -93,10 +100,18 @@ class _TapTracker {
   bool hasElapsedMinTime() {
     return _doubleTapMinTimeCountdown.timeout;
   }
+
+  bool hasSameButton(PointerDownEvent event) {
+    return event.buttons == initialButtons;
+  }
 }
 
 /// Recognizes when the user has tapped the screen at the same location twice in
 /// quick succession.
+///
+/// [DoubleTapGestureRecognizer] competes on pointer events of [kPrimaryButton]
+/// only when it has a non-null callback. If it has no callbacks, it is a no-op.
+///
 class DoubleTapGestureRecognizer extends GestureRecognizer {
   /// Create a gesture recognizer for double taps.
   ///
@@ -126,26 +141,53 @@ class DoubleTapGestureRecognizer extends GestureRecognizer {
   // - The long timer between taps expires
   // - The gesture arena decides we have been rejected wholesale
 
-  /// Called when the user has tapped the screen at the same location twice in
-  /// quick succession.
+  /// Called when the user has tapped the screen with a primary button at the
+  /// same location twice in quick succession.
+  ///
+  /// This triggers when the pointer stops contacting the device after the 2nd tap,
+  /// immediately after [onDoubleTapUp].
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   GestureDoubleTapCallback onDoubleTap;
 
   Timer _doubleTapTimer;
   _TapTracker _firstTap;
   final Map<int, _TapTracker> _trackers = <int, _TapTracker>{};
 
+  @override
+  bool isPointerAllowed(PointerEvent event) {
+    if (_firstTap == null) {
+      switch (event.buttons) {
+        case kPrimaryButton:
+          if (onDoubleTap == null)
+            return false;
+          break;
+        default:
+          return false;
+      }
+    }
+    return super.isPointerAllowed(event);
+  }
+
   @override
   void addAllowedPointer(PointerEvent event) {
     if (_firstTap != null) {
       if (!_firstTap.isWithinTolerance(event, kDoubleTapSlop)) {
         // Ignore out-of-bounds second taps.
         return;
-      } else if (!_firstTap.hasElapsedMinTime()) {
-        // Restart when the second tap is too close to the first.
+      } else if (!_firstTap.hasElapsedMinTime() || !_firstTap.hasSameButton(event)) {
+        // Restart when the second tap is too close to the first, or when buttons
+        // mismatch.
         _reset();
-        return addAllowedPointer(event);
+        return _trackFirstTap(event);
       }
     }
+    _trackFirstTap(event);
+  }
+
+  void _trackFirstTap(PointerEvent event) {
     _stopDoubleTapTimer();
     final _TapTracker tracker = _TapTracker(
       event: event,
@@ -235,8 +277,7 @@ class DoubleTapGestureRecognizer extends GestureRecognizer {
     tracker.entry.resolve(GestureDisposition.accepted);
     _freezeTracker(tracker);
     _trackers.remove(tracker.pointer);
-    if (onDoubleTap != null)
-      invokeCallback<void>('onDoubleTap', onDoubleTap);
+    _checkUp(tracker.initialButtons);
     _reset();
   }
 
@@ -260,6 +301,12 @@ class DoubleTapGestureRecognizer extends GestureRecognizer {
     }
   }
 
+  void _checkUp(int buttons) {
+    assert(buttons == kPrimaryButton);
+    if (onDoubleTap != null)
+      invokeCallback<void>('onDoubleTap', onDoubleTap);
+  }
+
   @override
   String get debugDescription => 'double tap';
 }

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

@@ -9,7 +9,7 @@ import 'constants.dart';
 import 'events.dart';
 import 'recognizer.dart';
 
-/// Details for [GestureTapDownCallback], such as position.
+/// Details for [GestureTapDownCallback], such as position
 ///
 /// See also:
 ///
@@ -45,8 +45,6 @@ typedef GestureTapDownCallback = void Function(TapDownDetails details);
 ///  * [GestureDetector.onTapUp], which receives this information.
 ///  * [TapGestureRecognizer], which passes this information to one of its callbacks.
 class TapUpDetails {
-  /// Creates details for a [GestureTapUpCallback].
-  ///
   /// The [globalPosition] argument must not be null.
   TapUpDetails({ this.globalPosition = Offset.zero })
     : assert(globalPosition != null);
@@ -95,14 +93,10 @@ typedef GestureTapCancelCallback = void Function();
 /// pointer interactions during a tap sequence are not recognized as additional
 /// taps. For example, down-1, down-2, up-1, up-2 produces only one tap on up-1.
 ///
-/// The lifecycle of events for a tap gesture is as follows:
-///
-/// * [onTapDown], which triggers after a short timeout ([deadline]) even if the
-///   gesture has not won its arena yet.
-/// * [onTapUp] and [onTap], which trigger when the pointer is released if the
-///   gesture wins the arena.
-/// * [onTapCancel], which triggers instead of [onTapUp] and [onTap] in the case
-///   of the gesture not winning the arena.
+/// [TapGestureRecognizer] competes on pointer events of [kPrimaryButton] only
+/// when it has at least one non-null `onTap*` callback, and events of
+/// [kSecondaryButton] only when it has at least one non-null `onSecondaryTap*`
+/// callback. If it has no callbacks, it is a no-op.
 ///
 /// See also:
 ///
@@ -112,22 +106,25 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
   /// Creates a tap gesture recognizer.
   TapGestureRecognizer({ Object debugOwner }) : super(deadline: kPressTimeout, debugOwner: debugOwner);
 
-  /// A pointer that might cause a tap has contacted the screen at a particular
-  /// location.
+  /// A pointer that might cause a tap of a primary button has contacted the
+  /// screen at a particular location.
   ///
-  /// This triggers before the gesture has won the arena, after a short timeout
-  /// ([deadline]).
+  /// This triggers once a short timeout ([deadline]) has elapsed, or once
+  /// the gestures has won the arena, whichever comes first.
   ///
   /// If the gesture doesn't win the arena, [onTapCancel] is called next.
   /// Otherwise, [onTapUp] is called next.
   ///
   /// See also:
   ///
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [onSecondaryTapDown], a similar callback but for a secondary button.
+  ///  * [TapDownDetails], which is passed as an argument to this callback.
   ///  * [GestureDetector.onTapDown], which exposes this callback.
   GestureTapDownCallback onTapDown;
 
-  /// A pointer that will trigger a tap has stopped contacting the screen at a
-  /// particular location.
+  /// A pointer that will trigger a tap of a primary button has stopped
+  /// contacting the screen at a particular location.
   ///
   /// This triggers once the gesture has won the arena, immediately before
   /// [onTap].
@@ -136,11 +133,13 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
   ///
   /// See also:
   ///
-  ///  * [GestureDetector.onTapUp], which exposes this callback.
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [onSecondaryTapUp], a similar callback but for a secondary button.
   ///  * [TapUpDetails], which is passed as an argument to this callback.
+  ///  * [GestureDetector.onTapUp], which exposes this callback.
   GestureTapUpCallback onTapUp;
 
-  /// A tap has occurred.
+  /// A tap of a primary button has occurred.
   ///
   /// This triggers once the gesture has won the arena, immediately after
   /// [onTapUp].
@@ -149,6 +148,8 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
   ///
   /// See also:
   ///
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [onTapUp], which has the same timing but with details.
   ///  * [GestureDetector.onTap], which exposes this callback.
   GestureTapCallback onTap;
 
@@ -161,37 +162,121 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
   ///
   /// See also:
   ///
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [onSecondaryTapCancel], a similar callback but for a secondary button.
   ///  * [GestureDetector.onTapCancel], which exposes this callback.
   GestureTapCancelCallback onTapCancel;
 
+  /// A pointer that might cause a tap of a secondary button has contacted the
+  /// screen at a particular location.
+  ///
+  /// This triggers once a short timeout ([deadline]) has elapsed, or once
+  /// the gestures has won the arena, whichever comes first.
+  ///
+  /// If the gesture doesn't win the arena, [onSecondaryTapCancel] is called next.
+  /// Otherwise, [onSecondaryTapUp] is called next.
+  ///
+  /// See also:
+  ///
+  ///  * [kSecondaryButton], the button this callback responds to.
+  ///  * [onPrimaryTapDown], a similar callback but for a primary button.
+  ///  * [TapDownDetails], which is passed as an argument to this callback.
+  ///  * [GestureDetector.onSecondaryTapDown], which exposes this callback.
+  GestureTapDownCallback onSecondaryTapDown;
+
+  /// A pointer that will trigger a tap of a secondary button has stopped
+  /// contacting the screen at a particular location.
+  ///
+  /// This triggers once the gesture has won the arena.
+  ///
+  /// If the gesture doesn't win the arena, [onSecondaryTapCancel] is called
+  /// instead.
+  ///
+  /// See also:
+  ///
+  ///  * [kSecondaryButton], the button this callback responds to.
+  ///  * [onPrimaryTapUp], a similar callback but for a primary button.
+  ///  * [TapUpDetails], which is passed as an argument to this callback.
+  ///  * [GestureDetector.onSecondaryTapUp], which exposes this callback.
+  GestureTapUpCallback onSecondaryTapUp;
+
+  /// The pointer that previously triggered [onSecondaryTapDown] will not end up
+  /// causing a tap.
+  ///
+  /// This triggers if the gesture loses the arena.
+  ///
+  /// If the gesture wins the arena, [onSecondaryTapUp] is called instead.
+  ///
+  /// See also:
+  ///
+  ///  * [kSecondaryButton], the button this callback responds to.
+  ///  * [onPrimaryTapCancel], a similar callback but for a primary button.
+  ///  * [GestureDetector.onTapCancel], which exposes this callback.
+  GestureTapCancelCallback onSecondaryTapCancel;
+
   bool _sentTapDown = false;
   bool _wonArenaForPrimaryPointer = false;
   Offset _finalPosition;
+  // The buttons sent by `PointerDownEvent`. If a `PointerMoveEvent` comes with a
+  // different set of buttons, the gesture is canceled.
+  int _initialButtons;
+
+  @override
+  bool isPointerAllowed(PointerDownEvent event) {
+    switch (event.buttons) {
+      case kPrimaryButton:
+        if (onTapDown == null &&
+            onTap == null &&
+            onTapUp == null &&
+            onTapCancel == null)
+          return false;
+        break;
+      case kSecondaryButton:
+        if (onSecondaryTapDown == null &&
+            onSecondaryTapUp == null &&
+            onSecondaryTapCancel == null)
+          return false;
+        break;
+      default:
+        return false;
+    }
+    return super.isPointerAllowed(event);
+  }
+
+  @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;
+  }
 
   @override
   void handlePrimaryPointer(PointerEvent event) {
     if (event is PointerUpEvent) {
       _finalPosition = event.position;
-      if (_wonArenaForPrimaryPointer) {
-        resolve(GestureDisposition.accepted);
-        _checkUp();
-      }
+      _checkUp();
     } else if (event is PointerCancelEvent) {
-      if (_sentTapDown && onTapCancel != null) {
-        invokeCallback<void>('onTapCancel', onTapCancel);
+      resolve(GestureDisposition.rejected);
+      if (_sentTapDown) {
+        _checkCancel('');
       }
       _reset();
+    } else if (event.buttons != _initialButtons) {
+      resolve(GestureDisposition.rejected);
+      stopTrackingPointer(primaryPointer);
     }
   }
 
   @override
   void resolve(GestureDisposition disposition) {
     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.
+      // 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);
-      if (onTapCancel != null)
-        invokeCallback<void>('spontaneous onTapCancel', onTapCancel);
+      _checkCancel('spontaneous ');
       _reset();
     }
     super.resolve(disposition);
@@ -218,27 +303,70 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
     if (pointer == primaryPointer) {
       // Another gesture won the arena.
       assert(state != GestureRecognizerState.possible);
-      if (_sentTapDown && onTapCancel != null)
-        invokeCallback<void>('forced onTapCancel', onTapCancel);
+      if (_sentTapDown)
+        _checkCancel('forced ');
       _reset();
     }
   }
 
   void _checkDown() {
-    if (!_sentTapDown) {
-      if (onTapDown != null)
-        invokeCallback<void>('onTapDown', () { onTapDown(TapDownDetails(globalPosition: initialPosition)); });
-      _sentTapDown = true;
+    if (_sentTapDown) {
+      return;
+    }
+    final TapDownDetails details = TapDownDetails(
+      globalPosition: initialPosition,
+    );
+    switch (_initialButtons) {
+      case kPrimaryButton:
+        if (onTapDown != null)
+          invokeCallback<void>('onTapDown', () => onTapDown(details));
+        break;
+      case kSecondaryButton:
+        if (onSecondaryTapDown != null)
+          invokeCallback<void>('onSecondaryTapDown',
+            () => onSecondaryTapDown(details));
+        break;
+      default:
     }
+    _sentTapDown = true;
   }
 
   void _checkUp() {
-    if (_finalPosition != null) {
-      if (onTapUp != null)
-        invokeCallback<void>('onTapUp', () { onTapUp(TapUpDetails(globalPosition: _finalPosition)); });
-      if (onTap != null)
-        invokeCallback<void>('onTap', onTap);
-      _reset();
+    if (!_wonArenaForPrimaryPointer || _finalPosition == null) {
+      return;
+    }
+    final TapUpDetails details = TapUpDetails(
+      globalPosition: _finalPosition,
+    );
+    switch (_initialButtons) {
+      case kPrimaryButton:
+        if (onTapUp != null)
+          invokeCallback<void>('onTapUp', () => onTapUp(details));
+        if (onTap != null)
+          invokeCallback<void>('onTap', onTap);
+        break;
+      case kSecondaryButton:
+        if (onSecondaryTapUp != null)
+          invokeCallback<void>('onSecondaryTapUp',
+            () => onSecondaryTapUp(details));
+        break;
+      default:
+    }
+    _reset();
+  }
+
+  void _checkCancel(String note) {
+    switch (_initialButtons) {
+      case kPrimaryButton:
+        if (onTapCancel != null)
+          invokeCallback<void>('${note}onTapCancel', onTapCancel);
+        break;
+      case kSecondaryButton:
+        if (onSecondaryTapCancel != null)
+          invokeCallback<void>('${note}onSecondaryTapCancel',
+            onSecondaryTapCancel);
+        break;
+      default:
     }
   }
 
@@ -246,6 +374,7 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
     _sentTapDown = false;
     _wonArenaForPrimaryPointer = false;
     _finalPosition = null;
+    _initialButtons = null;
   }
 
   @override
@@ -257,5 +386,6 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
     properties.add(FlagProperty('wonArenaForPrimaryPointer', value: _wonArenaForPrimaryPointer, ifTrue: 'won arena'));
     properties.add(DiagnosticsProperty<Offset>('finalPosition', _finalPosition, defaultValue: null));
     properties.add(FlagProperty('sentTapDown', value: _sentTapDown, ifTrue: 'sent tap down'));
+    // TODO(tongmu): Add property _initialButtons and update related tests
   }
 }

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

@@ -166,6 +166,9 @@ class GestureDetector extends StatelessWidget {
     this.onTapUp,
     this.onTap,
     this.onTapCancel,
+    this.onSecondaryTapDown,
+    this.onSecondaryTapUp,
+    this.onSecondaryTapCancel,
     this.onDoubleTap,
     this.onLongPress,
     this.onLongPressStart,
@@ -229,28 +232,37 @@ class GestureDetector extends StatelessWidget {
   /// {@macro flutter.widgets.child}
   final Widget child;
 
-  /// A pointer that might cause a tap has contacted the screen at a particular
-  /// location.
+  /// A pointer that might cause a tap with a primary button has contacted the
+  /// screen at a particular location.
   ///
   /// This is called after a short timeout, even if the winning gesture has not
   /// yet been selected. If the tap gesture wins, [onTapUp] will be called,
   /// otherwise [onTapCancel] will be called.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureTapDownCallback onTapDown;
 
-  /// A pointer that will trigger a tap has stopped contacting the screen at a
-  /// particular location.
+  /// A pointer that will trigger a tap with a primary button has stopped
+  /// contacting the screen at a particular location.
   ///
   /// This triggers immediately before [onTap] in the case of the tap gesture
   /// winning. If the tap gesture did not win, [onTapCancel] is called instead.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureTapUpCallback onTapUp;
 
-  /// A tap has occurred.
+  /// A tap with a primary button has occurred.
   ///
   /// This triggers when the tap gesture wins. If the tap gesture did not win,
   /// [onTapCancel] is called instead.
   ///
   /// See also:
   ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   ///  * [onTapUp], which is called at the same time but includes details
   ///    regarding the pointer position.
   final GestureTapCallback onTap;
@@ -260,104 +272,222 @@ class GestureDetector extends StatelessWidget {
   ///
   /// This is called after [onTapDown], and instead of [onTapUp] and [onTap], if
   /// the tap gesture did not win.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureTapCancelCallback onTapCancel;
 
-  /// The user has tapped the screen at the same location twice in quick
-  /// succession.
+  /// A pointer that might cause a tap with a secondary button has contacted the
+  /// screen at a particular location.
+  ///
+  /// This is called after a short timeout, even if the winning gesture has not
+  /// yet been selected. If the tap gesture wins, [onSecondaryTapUp] will be
+  /// called, otherwise [onSecondaryTapCancel] will be called.
+  ///
+  /// See also:
+  ///
+  ///  * [kSecondaryButton], the button this callback responds to.
+  final GestureTapDownCallback onSecondaryTapDown;
+
+  /// A pointer that will trigger a tap with a secondary button has stopped
+  /// contacting the screen at a particular location.
+  ///
+  /// This triggers in the case of the tap gesture winning. If the tap gesture
+  /// did not win, [onSecondaryTapCancel] is called instead.
+  ///
+  /// See also:
+  ///
+  ///  * [kSecondaryButton], the button this callback responds to.
+  final GestureTapUpCallback onSecondaryTapUp;
+
+  /// The pointer that previously triggered [onSecondaryTapDown] will not end up
+  /// causing a tap.
+  ///
+  /// This is called after [onSecondaryTapDown], and instead of
+  /// [onSecondaryTapUp], if the tap gesture did not win.
+  ///
+  /// See also:
+  ///
+  ///  * [kSecondaryButton], the button this callback responds to.
+  final GestureTapCancelCallback onSecondaryTapCancel;
+
+  /// The user has tapped the screen with a primary button at the same location
+  /// twice in quick succession.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureTapCallback onDoubleTap;
 
-  /// Called when a long press gesture has been recognized.
+  /// Called when a long press gesture with a primary button has been recognized.
   ///
   /// Triggered when a pointer has remained in contact with the screen at the
   /// same location for a long period of time.
   ///
   /// See also:
   ///
-  ///  * [onLongPressStart], which has the same timing but has data for the
-  ///    press location.
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [onLongPressStart], which has the same timing but has gesture details.
   final GestureLongPressCallback onLongPress;
 
-  /// Callback for long press start with gesture location.
+  /// Called when a long press gesture with a primary button has been recognized.
   ///
   /// Triggered when a pointer has remained in contact with the screen at the
   /// same location for a long period of time.
   ///
   /// See also:
   ///
-  ///  * [onLongPress], which has the same timing but without the location data.
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [onLongPress], which has the same timing but without the gesture details.
   final GestureLongPressStartCallback onLongPressStart;
 
-  /// A pointer has been drag-moved after a long press.
+  /// A pointer has been drag-moved after a long press with a primary button.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureLongPressMoveUpdateCallback onLongPressMoveUpdate;
 
-  /// A pointer that has triggered a long-press has stopped contacting the screen.
+  /// A pointer that has triggered a long-press with a primary button has
+  /// stopped contacting the screen.
   ///
   /// See also:
   ///
-  ///  * [onLongPressEnd], which has the same timing but has data for the up
-  ///    gesture location.
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [onLongPressEnd], which has the same timing but has gesture details.
   final GestureLongPressUpCallback onLongPressUp;
 
-  /// A pointer that has triggered a long-press has stopped contacting the screen.
+  /// A pointer that has triggered a long-press with a primary button has
+  /// stopped contacting the screen.
   ///
   /// See also:
   ///
-  ///  * [onLongPressUp], which has the same timing but without the location data.
+  ///  * [kPrimaryButton], the button this callback responds to.
+  ///  * [onLongPressUp], which has the same timing but without the gesture
+  ///    details.
   final GestureLongPressEndCallback onLongPressEnd;
 
-  /// A pointer has contacted the screen and might begin to move vertically.
+  /// A pointer has contacted the screen with a primary button and might begin
+  /// to move vertically.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragDownCallback onVerticalDragDown;
 
-  /// A pointer has contacted the screen and has begun to move vertically.
+  /// A pointer has contacted the screen with a primary button and has begun to
+  /// move vertically.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragStartCallback onVerticalDragStart;
 
-  /// A pointer that is in contact with the screen and moving vertically has
-  /// moved in the vertical direction.
+  /// A pointer that is in contact with the screen with a primary button and
+  /// moving vertically has moved in the vertical direction.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragUpdateCallback onVerticalDragUpdate;
 
-  /// A pointer that was previously in contact with the screen and moving
-  /// vertically is no longer in contact with the screen and was moving at a
-  /// specific velocity when it stopped contacting the screen.
+  /// A pointer that was previously in contact with the screen with a primary
+  /// button and moving vertically is no longer in contact with the screen and
+  /// was moving at a specific velocity when it stopped contacting the screen.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragEndCallback onVerticalDragEnd;
 
   /// The pointer that previously triggered [onVerticalDragDown] did not
   /// complete.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragCancelCallback onVerticalDragCancel;
 
-  /// A pointer has contacted the screen and might begin to move horizontally.
+  /// A pointer has contacted the screen with a primary button and might begin
+  /// to move horizontally.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragDownCallback onHorizontalDragDown;
 
-  /// A pointer has contacted the screen and has begun to move horizontally.
+  /// A pointer has contacted the screen with a primary button and has begun to
+  /// move horizontally.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragStartCallback onHorizontalDragStart;
 
-  /// A pointer that is in contact with the screen and moving horizontally has
-  /// moved in the horizontal direction.
+  /// A pointer that is in contact with the screen with a primary button and
+  /// moving horizontally has moved in the horizontal direction.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragUpdateCallback onHorizontalDragUpdate;
 
-  /// A pointer that was previously in contact with the screen and moving
-  /// horizontally is no longer in contact with the screen and was moving at a
-  /// specific velocity when it stopped contacting the screen.
+  /// A pointer that was previously in contact with the screen with a primary
+  /// button and moving horizontally is no longer in contact with the screen and
+  /// was moving at a specific velocity when it stopped contacting the screen.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragEndCallback onHorizontalDragEnd;
 
   /// The pointer that previously triggered [onHorizontalDragDown] did not
   /// complete.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragCancelCallback onHorizontalDragCancel;
 
-  /// A pointer has contacted the screen and might begin to move.
+  /// A pointer has contacted the screen with a primary button and might begin
+  /// to move.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragDownCallback onPanDown;
 
-  /// A pointer has contacted the screen and has begun to move.
+  /// A pointer has contacted the screen with a primary button and has begun to
+  /// move.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragStartCallback onPanStart;
 
-  /// A pointer that is in contact with the screen and moving has moved again.
+  /// A pointer that is in contact with the screen with a primary button and
+  /// moving has moved again.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragUpdateCallback onPanUpdate;
 
-  /// A pointer that was previously in contact with the screen and moving
-  /// is no longer in contact with the screen and was moving at a specific
-  /// velocity when it stopped contacting the screen.
+  /// A pointer that was previously in contact with the screen with a primary
+  /// button and moving is no longer in contact with the screen and was moving
+  /// at a specific velocity when it stopped contacting the screen.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragEndCallback onPanEnd;
 
   /// The pointer that previously triggered [onPanDown] did not complete.
+  ///
+  /// See also:
+  ///
+  ///  * [kPrimaryButton], the button this callback responds to.
   final GestureDragCancelCallback onPanCancel;
 
   /// The pointers in contact with the screen have established a focal point and
@@ -440,7 +570,15 @@ class GestureDetector extends StatelessWidget {
   Widget build(BuildContext context) {
     final Map<Type, GestureRecognizerFactory> gestures = <Type, GestureRecognizerFactory>{};
 
-    if (onTapDown != null || onTapUp != null || onTap != null || onTapCancel != null) {
+    if (
+      onTapDown != null ||
+      onTapUp != null ||
+      onTap != null ||
+      onTapCancel != null ||
+      onSecondaryTapDown != null ||
+      onSecondaryTapUp != null ||
+      onSecondaryTapCancel != null
+    ) {
       gestures[TapGestureRecognizer] = GestureRecognizerFactoryWithHandlers<TapGestureRecognizer>(
         () => TapGestureRecognizer(debugOwner: this),
         (TapGestureRecognizer instance) {
@@ -448,7 +586,10 @@ class GestureDetector extends StatelessWidget {
             ..onTapDown = onTapDown
             ..onTapUp = onTapUp
             ..onTap = onTap
-            ..onTapCancel = onTapCancel;
+            ..onTapCancel = onTapCancel
+            ..onSecondaryTapDown = onSecondaryTapDown
+            ..onSecondaryTapUp = onSecondaryTapUp
+            ..onSecondaryTapCancel = onSecondaryTapCancel;
         },
       );
     }
@@ -797,8 +938,14 @@ class RawGestureDetectorState extends State<RawGestureDetector> {
   void _handleSemanticsLongPress() {
     final LongPressGestureRecognizer recognizer = _recognizers[LongPressGestureRecognizer];
     assert(recognizer != null);
+    if (recognizer.onLongPressStart != null)
+      recognizer.onLongPressStart(const LongPressStartDetails());
     if (recognizer.onLongPress != null)
       recognizer.onLongPress();
+    if (recognizer.onLongPressEnd != null)
+      recognizer.onLongPressEnd(const LongPressEndDetails());
+    if (recognizer.onLongPressUp != null)
+      recognizer.onLongPressUp();
   }
 
   void _handleSemanticsHorizontalDragUpdate(DragUpdateDetails updateDetails) {

packages/flutter/test/gestures/debug_test.dart

@@ -147,7 +147,8 @@ void main() {
   });
 
   test('TapGestureRecognizer _sentTapDown toString', () {
-    final TapGestureRecognizer tap = TapGestureRecognizer();
+    final TapGestureRecognizer tap = TapGestureRecognizer()
+      ..onTap = () {}; // Add a callback so that event can be added
     expect(tap.toString(), equalsIgnoringHashCodes('TapGestureRecognizer#00000(state: ready)'));
     const PointerEvent event = PointerDownEvent(pointer: 1, position: Offset(10.0, 10.0));
     tap.addPointer(event);

packages/flutter/test/gestures/double_tap_test.dart

@@ -75,7 +75,7 @@ void main() {
     position: Offset(25.0, 25.0),
   );
 
-  // Down/up pair 5: normal tap sequence identical to pair 1 with different pointer
+  // Down/up pair 5: normal tap sequence identical to pair 1
   const PointerDownEvent down5 = PointerDownEvent(
     pointer: 5,
     position: Offset(10.0, 10.0),
@@ -86,6 +86,18 @@ void main() {
     position: Offset(11.0, 9.0),
   );
 
+  // Down/up pair 6: normal tap sequence close to pair 1 but on secondary button
+  const PointerDownEvent down6 = PointerDownEvent(
+    pointer: 6,
+    position: Offset(10.0, 10.0),
+    buttons: kSecondaryMouseButton,
+  );
+
+  const PointerUpEvent up6 = PointerUpEvent(
+    pointer: 6,
+    position: Offset(11.0, 9.0),
+  );
+
   testGesture('Should recognize double tap', (GestureTester tester) {
     final DoubleTapGestureRecognizer tap = DoubleTapGestureRecognizer();
 
@@ -606,4 +618,183 @@ void main() {
 
     tap.dispose();
   });
+
+  group('Enforce consistent-button restriction:', () {
+    testGesture('Button change should interrupt existing sequence', (GestureTester tester) {
+      // Down1 -> down6 (different button from 1) -> down2 (same button as 1)
+      // Down1 and down2 could've been a double tap, but is interrupted by down 6.
+
+      const Duration interval = Duration(milliseconds: 100);
+      assert(interval * 2 < kDoubleTapTimeout);
+      assert(interval > kDoubleTapMinTime);
+
+      final DoubleTapGestureRecognizer tap = DoubleTapGestureRecognizer();
+
+      bool doubleTapRecognized = false;
+      tap.onDoubleTap = () {
+        doubleTapRecognized = true;
+      };
+
+      tap.addPointer(down1);
+      tester.closeArena(1);
+      tester.route(down1);
+      tester.route(up1);
+      GestureBinding.instance.gestureArena.sweep(1);
+
+      tester.async.elapse(interval);
+
+      tap.addPointer(down6);
+      tester.closeArena(6);
+      tester.route(down6);
+      tester.route(up6);
+      GestureBinding.instance.gestureArena.sweep(6);
+
+      tester.async.elapse(interval);
+      expect(doubleTapRecognized, isFalse);
+
+      tap.addPointer(down2);
+      tester.closeArena(2);
+      tester.route(down2);
+      tester.route(up2);
+      GestureBinding.instance.gestureArena.sweep(2);
+
+      expect(doubleTapRecognized, isFalse);
+
+      tap.dispose();
+    });
+
+    testGesture('Button change should start a valid sequence', (GestureTester tester) {
+      // Down6 -> down1 (different button from 6) -> down2 (same button as 1)
+
+      const Duration interval = Duration(milliseconds: 100);
+      assert(interval * 2 < kDoubleTapTimeout);
+      assert(interval > kDoubleTapMinTime);
+
+      final DoubleTapGestureRecognizer tap = DoubleTapGestureRecognizer();
+
+      bool doubleTapRecognized = false;
+      tap.onDoubleTap = () {
+        doubleTapRecognized = true;
+      };
+
+      tap.addPointer(down6);
+      tester.closeArena(6);
+      tester.route(down6);
+      tester.route(up6);
+      GestureBinding.instance.gestureArena.sweep(6);
+
+      tester.async.elapse(interval);
+
+      tap.addPointer(down1);
+      tester.closeArena(1);
+      tester.route(down1);
+      tester.route(up1);
+      GestureBinding.instance.gestureArena.sweep(1);
+
+      expect(doubleTapRecognized, isFalse);
+      tester.async.elapse(interval);
+
+      tap.addPointer(down2);
+      tester.closeArena(2);
+      tester.route(down2);
+      tester.route(up2);
+      GestureBinding.instance.gestureArena.sweep(2);
+
+      expect(doubleTapRecognized, isTrue);
+
+      tap.dispose();
+    });
+  });
+
+  group('Recognizers listening on different buttons do not form competition:', () {
+    // This test is assisted by tap recognizers. If a tap gesture has
+    // no competing recognizers, a pointer down event triggers its onTapDown
+    // immediately; if there are competitors, onTapDown is triggered after a
+    // timeout.
+    // The following tests make sure that double tap recognizers do not form
+    // competition with a tap gesture recognizer listening on a different button.
+
+    final List<String> recognized = <String>[];
+    TapGestureRecognizer tapPrimary;
+    TapGestureRecognizer tapSecondary;
+    DoubleTapGestureRecognizer doubleTap;
+    setUp(() {
+      tapPrimary = TapGestureRecognizer()
+        ..onTapDown = (TapDownDetails details) {
+          recognized.add('tapPrimary');
+        };
+      tapSecondary = TapGestureRecognizer()
+        ..onSecondaryTapDown = (TapDownDetails details) {
+          recognized.add('tapSecondary');
+        };
+      doubleTap = DoubleTapGestureRecognizer()
+        ..onDoubleTap = () {
+          recognized.add('doubleTap');
+        };
+    });
+
+    tearDown(() {
+      recognized.clear();
+      tapPrimary.dispose();
+      tapSecondary.dispose();
+      doubleTap.dispose();
+    });
+
+    testGesture('A primary double tap recognizer does not form competion with a secondary tap recognizer', (GestureTester tester) {
+      doubleTap.addPointer(down6);
+      tapSecondary.addPointer(down6);
+      tester.closeArena(down6.pointer);
+
+      tester.route(down6);
+      expect(recognized, <String>['tapSecondary']);
+    });
+
+    testGesture('A primary double tap recognizer forms competion with a primary tap recognizer', (GestureTester tester) {
+      doubleTap.addPointer(down1);
+      tapPrimary.addPointer(down1);
+      tester.closeArena(down1.pointer);
+
+      tester.route(down1);
+      expect(recognized, <String>[]);
+
+      tester.async.elapse(const Duration(milliseconds: 300));
+      expect(recognized, <String>['tapPrimary']);
+    });
+  });
+
+  testGesture('A secondary double tap should not trigger primary', (GestureTester tester) {
+    final List<String> recognized = <String>[];
+    final DoubleTapGestureRecognizer doubleTap = DoubleTapGestureRecognizer()
+      ..onDoubleTap = () {
+        recognized.add('primary');
+      };
+
+    // Down/up pair 7: normal tap sequence close to pair 6
+    const PointerDownEvent down7 = PointerDownEvent(
+      pointer: 7,
+      position: Offset(10.0, 10.0),
+      buttons: kSecondaryMouseButton,
+    );
+
+    const PointerUpEvent up7 = PointerUpEvent(
+      pointer: 7,
+      position: Offset(11.0, 9.0),
+    );
+
+    doubleTap.addPointer(down6);
+    tester.closeArena(6);
+    tester.route(down6);
+    tester.route(up6);
+    GestureBinding.instance.gestureArena.sweep(6);
+
+    tester.async.elapse(const Duration(milliseconds: 100));
+    doubleTap.addPointer(down7);
+    tester.closeArena(7);
+    tester.route(down7);
+    tester.route(up7);
+    expect(recognized, <String>[]);
+
+    recognized.clear();
+    doubleTap.dispose();
+  });
 }

packages/flutter/test/gestures/drag_test.dart

@@ -13,7 +13,7 @@ void main() {
 
   testGesture('Should recognize pan', (GestureTester tester) {
     final PanGestureRecognizer pan = PanGestureRecognizer();
-    final TapGestureRecognizer tap = TapGestureRecognizer();
+    final TapGestureRecognizer tap = TapGestureRecognizer()..onTap = () {};
 
     bool didStartPan = false;
     pan.onStart = (_) {
@@ -81,7 +81,8 @@ void main() {
 
   testGesture('Should report most recent point to onStart by default', (GestureTester tester) {
     final HorizontalDragGestureRecognizer drag = HorizontalDragGestureRecognizer();
-    final VerticalDragGestureRecognizer competingDrag = VerticalDragGestureRecognizer();
+    final VerticalDragGestureRecognizer competingDrag = VerticalDragGestureRecognizer()
+      ..onStart = (_) {};
 
     Offset positionAtOnStart;
     drag.onStart = (DragStartDetails details) {
@@ -103,9 +104,9 @@ void main() {
   });
 
   testGesture('Should report most recent point to onStart with a start configuration', (GestureTester tester) {
-    final HorizontalDragGestureRecognizer drag =
-    HorizontalDragGestureRecognizer();
-    final VerticalDragGestureRecognizer competingDrag = VerticalDragGestureRecognizer();
+    final HorizontalDragGestureRecognizer drag = HorizontalDragGestureRecognizer();
+    final VerticalDragGestureRecognizer competingDrag = VerticalDragGestureRecognizer()
+      ..onStart = (_) {};
 
     Offset positionAtOnStart;
     drag.onStart = (DragStartDetails details) {
@@ -218,9 +219,11 @@ void main() {
   // TODO(jslavitz): Revert these tests.
 
   testGesture('Should report initial down point to onStart with a down configuration', (GestureTester tester) {
-    final HorizontalDragGestureRecognizer drag =
-    HorizontalDragGestureRecognizer() ..dragStartBehavior = DragStartBehavior.down;
-    final VerticalDragGestureRecognizer competingDrag = VerticalDragGestureRecognizer() ..dragStartBehavior = DragStartBehavior.down;
+    final HorizontalDragGestureRecognizer drag = HorizontalDragGestureRecognizer()
+      ..dragStartBehavior = DragStartBehavior.down;
+    final VerticalDragGestureRecognizer competingDrag = VerticalDragGestureRecognizer()
+      ..dragStartBehavior = DragStartBehavior.down
+      ..onStart = (_) {};
 
     Offset positionAtOnStart;
     drag.onStart = (DragStartDetails details) {
@@ -596,4 +599,252 @@ void main() {
 
     drag.dispose();
   });
+
+  group('Enforce consistent-button restriction:', () {
+    PanGestureRecognizer pan;
+    TapGestureRecognizer tap;
+    final List<String> logs = <String>[];
+
+    setUp(() {
+      tap = TapGestureRecognizer()
+        ..onTap = () {}; // Need a callback to enable competition
+      pan = PanGestureRecognizer()
+        ..onStart = (DragStartDetails details) {
+          logs.add('start');
+        }
+        ..onDown = (DragDownDetails details) {
+          logs.add('down');
+        }
+        ..onUpdate = (DragUpdateDetails details) {
+          logs.add('update');
+        }
+        ..onCancel = () {
+          logs.add('cancel');
+        }
+        ..onEnd = (DragEndDetails details) {
+          logs.add('end');
+        };
+    });
+
+    tearDown(() {
+      pan.dispose();
+      tap.dispose();
+      logs.clear();
+    });
+
+    testGesture('Button change before acceptance should lead to immediate cancel', (GestureTester tester) {
+      final TestPointer pointer = TestPointer(5, PointerDeviceKind.mouse, kPrimaryButton);
+      final PointerDownEvent down = pointer.down(const Offset(10.0, 10.0));
+      pan.addPointer(down);
+      tap.addPointer(down);
+      tester.closeArena(5);
+
+      tester.route(down);
+      expect(logs, <String>['down']);
+      pointer.buttons = kSecondaryButton;
+      // Move out of slop so make sure button changes takes priority over slops
+      tester.route(pointer.move(const Offset(30.0, 30.0)));
+      expect(logs, <String>['down', 'cancel']);
+
+      tester.route(pointer.up());
+    });
+
+    testGesture('Button change before acceptance should not prevent the next drag', (GestureTester tester) {
+      { // First drag (which is canceled)
+        final TestPointer pointer = TestPointer(5, PointerDeviceKind.mouse, kPrimaryButton);
+        final PointerDownEvent down = pointer.down(const Offset(10.0, 10.0));
+        pan.addPointer(down);
+        tap.addPointer(down);
+        tester.closeArena(down.pointer);
+
+        tester.route(down);
+        pointer.buttons = kSecondaryButton;
+        tester.route(pointer.move(const Offset(10.0, 10.0)));
+        tester.route(pointer.up());
+        expect(logs, <String>['down', 'cancel']);
+      }
+      logs.clear();
+
+      final TestPointer pointer2 = TestPointer(6, PointerDeviceKind.mouse, kPrimaryButton);
+      final PointerDownEvent down2 = pointer2.down(const Offset(10.0, 10.0));
+      pan.addPointer(down2);
+      tap.addPointer(down2);
+      tester.closeArena(down2.pointer);
+      tester.route(down2);
+      expect(logs, <String>['down']);
+
+      tester.route(pointer2.move(const Offset(30.0, 30.0)));
+      expect(logs, <String>['down', 'start']);
+
+      tester.route(pointer2.up());
+      expect(logs, <String>['down', 'start', 'end']);
+    });
+
+    testGesture('Button change after acceptance should lead to immediate end', (GestureTester tester) {
+      final TestPointer pointer = TestPointer(5, PointerDeviceKind.mouse, kPrimaryButton);
+      final PointerDownEvent down = pointer.down(const Offset(10.0, 10.0));
+      pan.addPointer(down);
+      tap.addPointer(down);
+      tester.closeArena(down.pointer);
+
+      tester.route(down);
+      expect(logs, <String>['down']);
+      tester.route(pointer.move(const Offset(30.0, 30.0)));
+      expect(logs, <String>['down', 'start']);
+      pointer.buttons = kSecondaryButton;
+      tester.route(pointer.move(const Offset(30.0, 30.0)));
+      expect(logs, <String>['down', 'start', 'end']);
+
+      // Make sure no further updates are sent
+      tester.route(pointer.move(const Offset(50.0, 50.0)));
+      expect(logs, <String>['down', 'start', 'end']);
+
+      tester.route(pointer.up());
+    });
+
+    testGesture('Button change after acceptance should not prevent the next drag', (GestureTester tester) {
+      { // First drag (which is canceled)
+        final TestPointer pointer = TestPointer(5, PointerDeviceKind.mouse, kPrimaryButton);
+        final PointerDownEvent down = pointer.down(const Offset(10.0, 10.0));
+        pan.addPointer(down);
+        tap.addPointer(down);
+        tester.closeArena(down.pointer);
+
+        tester.route(down);
+
+        tester.route(pointer.move(const Offset(30.0, 30.0)));
+        pointer.buttons = kSecondaryButton;
+
+        tester.route(pointer.move(const Offset(30.0, 31.0)));
+        tester.route(pointer.up());
+        expect(logs, <String>['down', 'start', 'end']);
+      }
+      logs.clear();
+
+      final TestPointer pointer2 = TestPointer(6, PointerDeviceKind.mouse, kPrimaryButton);
+      final PointerDownEvent down2 = pointer2.down(const Offset(10.0, 10.0));
+      pan.addPointer(down2);
+      tap.addPointer(down2);
+      tester.closeArena(down2.pointer);
+      tester.route(down2);
+      expect(logs, <String>['down']);
+
+      tester.route(pointer2.move(const Offset(30.0, 30.0)));
+      expect(logs, <String>['down', 'start']);
+
+      tester.route(pointer2.up());
+      expect(logs, <String>['down', 'start', 'end']);
+    });
+  });
+
+  group('Recognizers listening on different buttons do not form competition:', () {
+    // This test is assisted by tap recognizers. If a tap gesture has
+    // no competing recognizers, a pointer down event triggers its onTapDown
+    // immediately; if there are competitors, onTapDown is triggered after a
+    // timeout.
+    // The following tests make sure that drag recognizers do not form
+    // competition with a tap gesture recognizer listening on a different button.
+
+    final List<String> recognized = <String>[];
+    TapGestureRecognizer tapPrimary;
+    TapGestureRecognizer tapSecondary;
+    PanGestureRecognizer pan;
+    setUp(() {
+      tapPrimary = TapGestureRecognizer()
+        ..onTapDown = (TapDownDetails details) {
+          recognized.add('tapPrimary');
+        };
+      tapSecondary = TapGestureRecognizer()
+        ..onSecondaryTapDown = (TapDownDetails details) {
+          recognized.add('tapSecondary');
+        };
+      pan = PanGestureRecognizer()
+        ..onStart = (_) {
+          recognized.add('drag');
+        };
+    });
+
+    tearDown(() {
+      recognized.clear();
+      tapPrimary.dispose();
+      tapSecondary.dispose();
+      pan.dispose();
+    });
+
+    testGesture('A primary pan recognizer does not form competion with a secondary tap recognizer', (GestureTester tester) {
+      final TestPointer pointer = TestPointer(
+        1,
+        PointerDeviceKind.touch,
+        kSecondaryButton,
+      );
+      final PointerDownEvent down = pointer.down(const Offset(10, 10));
+      pan.addPointer(down);
+      tapSecondary.addPointer(down);
+      tester.closeArena(down.pointer);
+
+      tester.route(down);
+      expect(recognized, <String>['tapSecondary']);
+    });
+
+    testGesture('A primary pan recognizer forms competion with a primary tap recognizer', (GestureTester tester) {
+      final TestPointer pointer = TestPointer(
+        1,
+        PointerDeviceKind.touch,
+        kPrimaryButton,
+      );
+      final PointerDownEvent down = pointer.down(const Offset(10, 10));
+      pan.addPointer(down);
+      tapPrimary.addPointer(down);
+      tester.closeArena(down.pointer);
+
+      tester.route(down);
+      expect(recognized, <String>[]);
+
+      tester.route(pointer.up());
+      expect(recognized, <String>['tapPrimary']);
+    });
+  });
+
+  testGesture('A secondary drag should not trigger primary', (GestureTester tester) {
+    final List<String> recognized = <String>[];
+    final TapGestureRecognizer tap = TapGestureRecognizer()
+      ..onTap = () {}; // Need a listener to enable competetion.
+    final PanGestureRecognizer pan = PanGestureRecognizer()
+      ..onDown = (DragDownDetails details) {
+        recognized.add('primaryDown');
+      }
+      ..onStart = (DragStartDetails details) {
+        recognized.add('primaryStart');
+      }
+      ..onUpdate = (DragUpdateDetails details) {
+        recognized.add('primaryUpdate');
+      }
+      ..onEnd = (DragEndDetails details) {
+        recognized.add('primaryEnd');
+      }
+      ..onCancel = () {
+        recognized.add('primaryCancel');
+      };
+
+    final TestPointer pointer = TestPointer(
+      5,
+      PointerDeviceKind.touch,
+      kSecondaryButton,
+    );
+
+    final PointerDownEvent down = pointer.down(const Offset(10.0, 10.0));
+    pan.addPointer(down);
+    tap.addPointer(down);
+    tester.closeArena(5);
+    tester.route(down);
+    tester.route(pointer.move(const Offset(20.0, 30.0)));
+    tester.route(pointer.move(const Offset(20.0, 25.0)));
+    tester.route(pointer.up());
+    expect(recognized, <String>[]);
+    recognized.clear();
+
+    pan.dispose();
+    tap.dispose();
+    recognized.clear();
+  });
 }

packages/flutter/test/gestures/events_test.dart

@@ -20,6 +20,20 @@ void main() {
     expect(nthStylusButton(2), kSecondaryStylusButton);
   });
 
+  testGesture('smallestButton tests', (GestureTester tester) {
+    expect(smallestButton(0x0), equals(0x0));
+    expect(smallestButton(0x1), equals(0x1));
+    expect(smallestButton(0x200), equals(0x200));
+    expect(smallestButton(0x220), equals(0x20));
+  });
+
+  testGesture('isSingleButton tests', (GestureTester tester) {
+    expect(isSingleButton(0x0), isFalse);
+    expect(isSingleButton(0x1), isTrue);
+    expect(isSingleButton(0x200), isTrue);
+    expect(isSingleButton(0x220), isFalse);
+  });
+
   group('Default values of PointerEvents:', () {
     // Some parameters are intentionally set to a non-trivial value.
 

packages/flutter/test/gestures/long_press_test.dart

@@ -7,6 +7,7 @@ import 'package:flutter/gestures.dart';
 import '../flutter_test_alternative.dart';
 import 'gesture_tester.dart';
 
+// Down/move/up pair 1: normal tap sequence
 const PointerDownEvent down = PointerDownEvent(
   pointer: 5,
   position: Offset(10, 10),
@@ -22,6 +23,29 @@ const PointerMoveEvent move = PointerMoveEvent(
   position: Offset(100, 200),
 );
 
+// Down/up pair 2: normal tap sequence far away from pair 1
+const PointerDownEvent down2 = PointerDownEvent(
+  pointer: 6,
+  position: Offset(10, 10),
+);
+
+const PointerUpEvent up2 = PointerUpEvent(
+  pointer: 6,
+  position: Offset(11, 9),
+);
+
+// Down/up pair 3: tap sequence with secondary button
+const PointerDownEvent down3 = PointerDownEvent(
+  pointer: 7,
+  position: Offset(30, 30),
+  buttons: kSecondaryButton,
+);
+
+const PointerUpEvent up3 = PointerUpEvent(
+  pointer: 7,
+  position: Offset(31, 29),
+);
+
 void main() {
   setUp(ensureGestureBinding);
 
@@ -187,6 +211,48 @@ void main() {
 
       longPress.dispose();
     });
+
+    testGesture('Should not recognize long press with more than one buttons', (GestureTester tester) {
+      longPress.addPointer(const PointerDownEvent(
+        pointer: 5,
+        kind: PointerDeviceKind.mouse,
+        buttons: kSecondaryMouseButton | kMiddleMouseButton,
+        position: Offset(10, 10),
+      ));
+      tester.closeArena(5);
+      expect(longPressDown, isFalse);
+      tester.route(down);
+      expect(longPressDown, isFalse);
+      tester.async.elapse(const Duration(milliseconds: 1000));
+      expect(longPressDown, isFalse);
+      tester.route(up);
+      expect(longPressUp, isFalse);
+
+      longPress.dispose();
+    });
+
+    testGesture('Should cancel long press when buttons change before acceptance', (GestureTester tester) {
+      longPress.addPointer(down);
+      tester.closeArena(5);
+      expect(longPressDown, isFalse);
+      tester.route(down);
+      expect(longPressDown, isFalse);
+      tester.async.elapse(const Duration(milliseconds: 300));
+      expect(longPressDown, isFalse);
+      tester.route(const PointerMoveEvent(
+        pointer: 5,
+        kind: PointerDeviceKind.mouse,
+        buttons: kMiddleMouseButton,
+        position: Offset(10, 10),
+      ));
+      expect(longPressDown, isFalse);
+      tester.async.elapse(const Duration(milliseconds: 700));
+      expect(longPressDown, isFalse);
+      tester.route(up);
+      expect(longPressUp, isFalse);
+
+      longPress.dispose();
+    });
   });
 
   group('long press drag', () {
@@ -279,6 +345,107 @@ void main() {
     });
   });
 
+  group('Enforce consistent-button restriction:', () {
+    // In sequence between `down` and `up` but with buttons changed
+    const PointerMoveEvent moveR = PointerMoveEvent(
+      pointer: 5,
+      buttons: kSecondaryButton,
+      position: Offset(10, 10),
+    );
+
+    final List<String> recognized = <String>[];
+
+    LongPressGestureRecognizer longPress;
+
+    setUp(() {
+      longPress = LongPressGestureRecognizer()
+        ..onLongPressStart = (LongPressStartDetails details) {
+          recognized.add('start');
+        }
+        ..onLongPressEnd = (LongPressEndDetails details) {
+          recognized.add('end');
+        };
+    });
+
+    tearDown(() {
+      longPress.dispose();
+      recognized.clear();
+    });
+
+    testGesture('Should cancel long press when buttons change before acceptance', (GestureTester tester) {
+      // First press
+      longPress.addPointer(down);
+      tester.closeArena(down.pointer);
+      tester.route(down);
+      tester.async.elapse(const Duration(milliseconds: 300));
+      tester.route(moveR);
+      expect(recognized, <String>[]);
+      tester.async.elapse(const Duration(milliseconds: 700));
+      tester.route(up);
+      expect(recognized, <String>[]);
+    });
+
+    testGesture('Buttons change before acceptance should not prevent the next long press', (GestureTester tester) {
+      // First press
+      longPress.addPointer(down);
+      tester.closeArena(down.pointer);
+      tester.route(down);
+      tester.async.elapse(const Duration(milliseconds: 300));
+      tester.route(moveR);
+      tester.async.elapse(const Duration(milliseconds: 700));
+      tester.route(up);
+      recognized.clear();
+
+      // Second press
+      longPress.addPointer(down2);
+      tester.closeArena(down2.pointer);
+      tester.route(down2);
+      tester.async.elapse(const Duration(milliseconds: 1000));
+      expect(recognized, <String>['start']);
+      recognized.clear();
+
+      tester.route(up2);
+      expect(recognized, <String>['end']);
+    });
+
+    testGesture('Should cancel long press when buttons change after acceptance', (GestureTester tester) {
+      // First press
+      longPress.addPointer(down);
+      tester.closeArena(down.pointer);
+      tester.route(down);
+      tester.async.elapse(const Duration(milliseconds: 1000));
+      expect(recognized, <String>['start']);
+      recognized.clear();
+
+      tester.route(moveR);
+      expect(recognized, <String>[]);
+      tester.route(up);
+      expect(recognized, <String>[]);
+    });
+
+    testGesture('Buttons change after acceptance should not prevent the next long press', (GestureTester tester) {
+      // First press
+      longPress.addPointer(down);
+      tester.closeArena(down.pointer);
+      tester.route(down);
+      tester.async.elapse(const Duration(milliseconds: 1000));
+      tester.route(moveR);
+      tester.route(up);
+      recognized.clear();
+
+      // Second press
+      longPress.addPointer(down2);
+      tester.closeArena(down2.pointer);
+      tester.route(down2);
+      tester.async.elapse(const Duration(milliseconds: 1000));
+      expect(recognized, <String>['start']);
+      recognized.clear();
+
+      tester.route(up2);
+      expect(recognized, <String>['end']);
+    });
+  });
+
   testGesture('Can filter long press based on device kind', (GestureTester tester) {
     final LongPressGestureRecognizer mouseLongPress = LongPressGestureRecognizer(kind: PointerDeviceKind.mouse);
 
@@ -318,4 +485,107 @@ void main() {
 
     mouseLongPress.dispose();
   });
+
+  group('Recognizers listening on different buttons do not form competition:', () {
+    // This test is assisted by tap recognizers. If a tap gesture has
+    // no competing recognizers, a pointer down event triggers its onTapDown
+    // immediately; if there are competitors, onTapDown is triggered after a
+    // timeout.
+    // The following tests make sure that long press recognizers do not form
+    // competition with a tap gesture recognizer listening on a different button.
+
+    final List<String> recognized = <String>[];
+    TapGestureRecognizer tapPrimary;
+    TapGestureRecognizer tapSecondary;
+    LongPressGestureRecognizer longPress;
+    setUp(() {
+      tapPrimary = TapGestureRecognizer()
+        ..onTapDown = (TapDownDetails details) {
+          recognized.add('tapPrimary');
+        };
+      tapSecondary = TapGestureRecognizer()
+        ..onSecondaryTapDown = (TapDownDetails details) {
+          recognized.add('tapSecondary');
+        };
+      longPress = LongPressGestureRecognizer()
+        ..onLongPressStart = (_) {
+          recognized.add('longPress');
+        };
+    });
+
+    tearDown(() {
+      recognized.clear();
+      tapPrimary.dispose();
+      tapSecondary.dispose();
+      longPress.dispose();
+    });
+
+    testGesture('A primary long press recognizer does not form competion with a secondary tap recognizer', (GestureTester tester) {
+      longPress.addPointer(down3);
+      tapSecondary.addPointer(down3);
+      tester.closeArena(down3.pointer);
+
+      tester.route(down3);
+      expect(recognized, <String>['tapSecondary']);
+    });
+
+    testGesture('A primary long press recognizer forms competion with a primary tap recognizer', (GestureTester tester) {
+      longPress.addPointer(down);
+      tapPrimary.addPointer(down);
+      tester.closeArena(down.pointer);
+
+      tester.route(down);
+      expect(recognized, <String>[]);
+
+      tester.route(up);
+      expect(recognized, <String>['tapPrimary']);
+    });
+  });
+
+  testGesture('A secondary long press should not trigger primary', (GestureTester tester) {
+    final List<String> recognized = <String>[];
+    final LongPressGestureRecognizer longPress = LongPressGestureRecognizer()
+      ..onLongPressStart = (LongPressStartDetails details) {
+        recognized.add('primaryStart');
+      }
+      ..onLongPress = () {
+        recognized.add('primary');
+      }
+      ..onLongPressMoveUpdate = (LongPressMoveUpdateDetails details) {
+        recognized.add('primaryUpdate');
+      }
+      ..onLongPressEnd = (LongPressEndDetails details) {
+        recognized.add('primaryEnd');
+      }
+      ..onLongPressUp = () {
+        recognized.add('primaryUp');
+      };
+
+    const PointerDownEvent down2 = PointerDownEvent(
+      pointer: 2,
+      buttons: kSecondaryButton,
+      position: Offset(30.0, 30.0),
+    );
+
+    const PointerMoveEvent move2 = PointerMoveEvent(
+      pointer: 2,
+      buttons: kSecondaryButton,
+      position: Offset(100, 200),
+    );
+
+    const PointerUpEvent up2 = PointerUpEvent(
+      pointer: 2,
+      position: Offset(100, 201),
+    );
+
+    longPress.addPointer(down2);
+    tester.closeArena(2);
+    tester.route(down2);
+    tester.async.elapse(const Duration(milliseconds: 700));
+    tester.route(move2);
+    tester.route(up2);
+    expect(recognized, <String>[]);
+    longPress.dispose();
+    recognized.clear();
+  });
 }

packages/flutter/test/gestures/tap_test.dart

@@ -73,6 +73,18 @@ void main() {
     position: Offset(22.0, 22.0),
   );
 
+  // Down/up sequence 5: tap sequence with secondary button
+  const PointerDownEvent down5 = PointerDownEvent(
+    pointer: 5,
+    position: Offset(20.0, 20.0),
+    buttons: kSecondaryButton,
+  );
+
+  const PointerUpEvent up5 = PointerUpEvent(
+    pointer: 5,
+    position: Offset(20.0, 20.0),
+  );
+
   testGesture('Should recognize tap', (GestureTester tester) {
     final TapGestureRecognizer tap = TapGestureRecognizer();
 
@@ -439,6 +451,48 @@ void main() {
     tap.dispose();
   });
 
+  testGesture('PointerCancelEvent after exceeding deadline 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 HorizontalDragGestureRecognizer drag = HorizontalDragGestureRecognizer()
+      ..onStart = (_) {}; // Need a callback to compete
+
+    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);
+    drag.addPointer(down);
+    tester.closeArena(5);
+    tester.route(down);
+    expect(recognized, <String>[]);
+    tester.async.elapse(const Duration(milliseconds: 1000));
+    expect(recognized, <String>['down']);
+    tester.route(cancel);
+    expect(recognized, <String>['down', 'cancel']);
+
+    tap.dispose();
+    drag.dispose();
+  });
+
   testGesture('losing tap gesture recognizer does not send onTapCancel', (GestureTester tester) {
     final TapGestureRecognizer tap = TapGestureRecognizer();
     final HorizontalDragGestureRecognizer drag = HorizontalDragGestureRecognizer();
@@ -467,4 +521,282 @@ void main() {
     tap.dispose();
     drag.dispose();
   });
+
+  group('Enforce consistent-button restriction:', () {
+    // Change buttons during down-up sequence 1
+    const PointerMoveEvent move1lr = PointerMoveEvent(
+      pointer: 1,
+      position: Offset(10.0, 10.0),
+      buttons: kPrimaryMouseButton | kSecondaryMouseButton,
+    );
+    const PointerMoveEvent move1r = PointerMoveEvent(
+      pointer: 1,
+      position: Offset(10.0, 10.0),
+      buttons: kSecondaryMouseButton,
+    );
+
+    final List<String> recognized = <String>[];
+    TapGestureRecognizer tap;
+    setUp(() {
+      tap = TapGestureRecognizer()
+        ..onTapDown = (TapDownDetails details) {
+          recognized.add('down');
+        }
+        ..onTapUp = (TapUpDetails details) {
+          recognized.add('up');
+        }
+        ..onTapCancel = () {
+          recognized.add('cancel');
+        };
+    });
+
+    tearDown(() {
+      tap.dispose();
+      recognized.clear();
+    });
+
+    testGesture('changing buttons before TapDown should cancel gesture without sending cancel', (GestureTester tester) {
+      tap.addPointer(down1);
+      tester.closeArena(1);
+      expect(recognized, <String>[]);
+
+      tester.route(move1lr);
+      expect(recognized, <String>[]);
+
+      tester.route(move1r);
+      expect(recognized, <String>[]);
+
+      tester.route(up1);
+      expect(recognized, <String>[]);
+
+      tap.dispose();
+    });
+
+    testGesture('changing buttons before TapDown should not prevent the next tap', (GestureTester tester) {
+      tap.addPointer(down1);
+      tester.closeArena(1);
+
+      tester.route(move1lr);
+      tester.route(move1r);
+      tester.route(up1);
+      expect(recognized, <String>[]);
+
+      tap.addPointer(down2);
+      tester.closeArena(2);
+      tester.async.elapse(const Duration(milliseconds: 1000));
+      tester.route(up2);
+      expect(recognized, <String>['down', 'up']);
+
+      tap.dispose();
+    });
+
+    testGesture('changing buttons after TapDown should cancel gesture and send cancel', (GestureTester tester) {
+      tap.addPointer(down1);
+      tester.closeArena(1);
+      expect(recognized, <String>[]);
+      tester.async.elapse(const Duration(milliseconds: 1000));
+      expect(recognized, <String>['down']);
+
+      tester.route(move1lr);
+      expect(recognized, <String>['down', 'cancel']);
+
+      tester.route(move1r);
+      expect(recognized, <String>['down', 'cancel']);
+
+      tester.route(up1);
+      expect(recognized, <String>['down', 'cancel']);
+
+      tap.dispose();
+    });
+
+    testGesture('changing buttons after TapDown should not prevent the next tap', (GestureTester tester) {
+      tap.addPointer(down1);
+      tester.closeArena(1);
+      tester.async.elapse(const Duration(milliseconds: 1000));
+
+      tester.route(move1lr);
+      tester.route(move1r);
+      tester.route(up1);
+      GestureBinding.instance.gestureArena.sweep(1);
+      expect(recognized, <String>['down', 'cancel']);
+
+      tap.addPointer(down2);
+      tester.closeArena(2);
+      tester.async.elapse(const Duration(milliseconds: 1000));
+      tester.route(up2);
+      GestureBinding.instance.gestureArena.sweep(2);
+      expect(recognized, <String>['down', 'cancel', 'down', 'up']);
+
+      tap.dispose();
+    });
+  });
+
+  group('Recognizers listening on different buttons do not form competition:', () {
+    // If a tap gesture has no competitors, a pointer down event triggers
+    // onTapDown immediately; if there are competitors, onTapDown is triggered
+    // after a timeout. The following tests make sure that tap recognizers
+    // listening on different buttons do not form competition.
+
+    final List<String> recognized = <String>[];
+    TapGestureRecognizer primary;
+    TapGestureRecognizer primary2;
+    TapGestureRecognizer secondary;
+    setUp(() {
+      primary = TapGestureRecognizer()
+        ..onTapDown = (TapDownDetails details) {
+          recognized.add('primaryDown');
+        }
+        ..onTapUp = (TapUpDetails details) {
+          recognized.add('primaryUp');
+        }
+        ..onTapCancel = () {
+          recognized.add('primaryCancel');
+        };
+      primary2 = TapGestureRecognizer()
+        ..onTapDown = (TapDownDetails details) {
+          recognized.add('primary2Down');
+        }
+        ..onTapUp = (TapUpDetails details) {
+          recognized.add('primary2Up');
+        }
+        ..onTapCancel = () {
+          recognized.add('primary2Cancel');
+        };
+      secondary = TapGestureRecognizer()
+        ..onSecondaryTapDown = (TapDownDetails details) {
+          recognized.add('secondaryDown');
+        }
+        ..onSecondaryTapUp = (TapUpDetails details) {
+          recognized.add('secondaryUp');
+        }
+        ..onSecondaryTapCancel = () {
+          recognized.add('secondaryCancel');
+        };
+    });
+
+    tearDown(() {
+      recognized.clear();
+      primary.dispose();
+      primary2.dispose();
+      secondary.dispose();
+    });
+
+    testGesture('A primary tap recognizer does not form competion with a secondary tap recognizer', (GestureTester tester) {
+      primary.addPointer(down1);
+      secondary.addPointer(down1);
+      tester.closeArena(1);
+
+      tester.route(down1);
+      expect(recognized, <String>['primaryDown']);
+      recognized.clear();
+
+      tester.route(up1);
+      expect(recognized, <String>['primaryUp']);
+    });
+
+    testGesture('A primary tap recognizer forms competion with another primary tap recognizer', (GestureTester tester) {
+      primary.addPointer(down1);
+      primary2.addPointer(down1);
+      tester.closeArena(1);
+
+      tester.route(down1);
+      expect(recognized, <String>[]);
+
+      tester.async.elapse(const Duration(milliseconds: 500));
+      expect(recognized, <String>['primaryDown', 'primary2Down']);
+    });
+  });
+
+  group('Gestures of different buttons trigger correct callbacks:', () {
+    final List<String> recognized = <String>[];
+    TapGestureRecognizer tap;
+    const PointerCancelEvent cancel1 = PointerCancelEvent(
+      pointer: 1,
+    );
+    const PointerCancelEvent cancel5 = PointerCancelEvent(
+      pointer: 5,
+    );
+
+    setUp(() {
+      tap = TapGestureRecognizer()
+        ..onTapDown = (TapDownDetails details) {
+          recognized.add('primaryDown');
+        }
+        ..onTap = () {
+          recognized.add('primary');
+        }
+        ..onTapUp = (TapUpDetails details) {
+          recognized.add('primaryUp');
+        }
+        ..onTapCancel = () {
+          recognized.add('primaryCancel');
+        }
+        ..onSecondaryTapDown = (TapDownDetails details) {
+          recognized.add('secondaryDown');
+        }
+        ..onSecondaryTapUp = (TapUpDetails details) {
+          recognized.add('secondaryUp');
+        }
+        ..onSecondaryTapCancel = () {
+          recognized.add('secondaryCancel');
+        };
+    });
+
+    tearDown(() {
+      recognized.clear();
+      tap.dispose();
+    });
+
+    testGesture('A primary tap should trigger primary callbacks', (GestureTester tester) {
+      tap.addPointer(down1);
+      tester.closeArena(down1.pointer);
+      expect(recognized, <String>[]);
+      tester.async.elapse(const Duration(milliseconds: 500));
+      expect(recognized, <String>['primaryDown']);
+      recognized.clear();
+
+      tester.route(up1);
+      expect(recognized, <String>['primaryUp', 'primary']);
+      GestureBinding.instance.gestureArena.sweep(down1.pointer);
+    });
+
+    testGesture('A primary tap cancel trigger primary callbacks', (GestureTester tester) {
+      tap.addPointer(down1);
+      tester.closeArena(down1.pointer);
+      expect(recognized, <String>[]);
+      tester.async.elapse(const Duration(milliseconds: 500));
+      expect(recognized, <String>['primaryDown']);
+      recognized.clear();
+
+      tester.route(cancel1);
+      expect(recognized, <String>['primaryCancel']);
+      GestureBinding.instance.gestureArena.sweep(down1.pointer);
+    });
+
+    testGesture('A secondary tap should trigger secondary callbacks', (GestureTester tester) {
+      tap.addPointer(down5);
+      tester.closeArena(down5.pointer);
+      expect(recognized, <String>[]);
+      tester.async.elapse(const Duration(milliseconds: 500));
+      expect(recognized, <String>['secondaryDown']);
+      recognized.clear();
+
+      tester.route(up5);
+      GestureBinding.instance.gestureArena.sweep(down5.pointer);
+      expect(recognized, <String>['secondaryUp']);
+    });
+
+    testGesture('A secondary tap cancel should trigger secondary callbacks', (GestureTester tester) {
+      tap.addPointer(down5);
+      tester.closeArena(down5.pointer);
+      expect(recognized, <String>[]);
+      tester.async.elapse(const Duration(milliseconds: 500));
+      expect(recognized, <String>['secondaryDown']);
+      recognized.clear();
+
+      tester.route(cancel5);
+      GestureBinding.instance.gestureArena.sweep(down5.pointer);
+      expect(recognized, <String>['secondaryCancel']);
+    });
+  });
 }

packages/flutter/test/widgets/platform_view_test.dart

@@ -592,7 +592,10 @@ void main() {
                 viewType: 'webview',
                 gestureRecognizers: <Factory<OneSequenceGestureRecognizer>>{
                   Factory<VerticalDragGestureRecognizer>(
-                        () => VerticalDragGestureRecognizer(),
+                    () {
+                      return VerticalDragGestureRecognizer()
+                        ..onStart = (_) {}; // Add callback to enable recognizer
+                    },
                   ),
                 },
                 layoutDirection: TextDirection.ltr,
@@ -1263,7 +1266,10 @@ void main() {
                 viewType: 'webview',
                 gestureRecognizers: <Factory<OneSequenceGestureRecognizer>>{
                   Factory<VerticalDragGestureRecognizer>(
-                        () => VerticalDragGestureRecognizer(),
+                    () {
+                      return VerticalDragGestureRecognizer()
+                        ..onStart = (_) {}; // Add callback to enable recognizer
+                    },
                   ),
                 },
                 layoutDirection: TextDirection.ltr,

packages/flutter_test/lib/src/test_pointer.dart

@@ -22,9 +22,14 @@ class TestPointer {
   ///
   /// Multiple [TestPointer]s created with the same pointer identifier will
   /// interfere with each other if they are used in parallel.
-  TestPointer([this.pointer = 1, this.kind = PointerDeviceKind.touch])
+  TestPointer([
+    this.pointer = 1,
+    this.kind = PointerDeviceKind.touch,
+    this.buttons = kPrimaryButton,
+  ])
       : assert(kind != null),
-        assert(pointer != null);
+        assert(pointer != null),
+        assert(buttons != null);
 
   /// The pointer identifier used for events generated by this object.
   ///
@@ -35,6 +40,10 @@ class TestPointer {
   /// [PointerDeviceKind.touch].
   final PointerDeviceKind kind;
 
+  /// The kind of buttons to simulate on Down and Move events. Defaults to
+  /// [kPrimaryButton].
+  int buttons;
+
   /// Whether the pointer simulated by this object is currently down.
   ///
   /// A pointer is released (goes up) by calling [up] or [cancel].
@@ -81,6 +90,7 @@ class TestPointer {
       kind: kind,
       pointer: pointer,
       position: location,
+      buttons: buttons,
     );
   }
 
@@ -105,6 +115,7 @@ class TestPointer {
       pointer: pointer,
       position: newLocation,
       delta: delta,
+      buttons: buttons,
     );
   }