widget/SwipeTracker.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef SwipeTracker_h
   8 #define SwipeTracker_h
   9
  10 #include "EventForwards.h"
  11 #include "mozilla/layers/AxisPhysicsMSDModel.h"
  12 #include "mozilla/RefPtr.h"
  13 #include "mozilla/TimeStamp.h"
  14 #include "nsRefreshObservers.h"
  15 #include "Units.h"
  16
  17 class nsIWidget;
  18 class nsRefreshDriver;
  19
  20 namespace mozilla {
  21
  22 class PanGestureInput;
  23
  24 /**
  25  * SwipeTracker turns PanGestureInput events into swipe events
  26  * (WidgetSimpleGestureEvent) and dispatches them into Gecko.
  27  * The swiping behavior mirrors the behavior of the Cocoa API
  28  * -[NSEvent
  29  *     trackSwipeEventWithOptions:dampenAmountThresholdMin:max:usingHandler:].
  30  * The advantage of using this class over the Cocoa API is that this class
  31  * properly supports submitting queued up events to it, and that it hopefully
  32  * doesn't intermittently break scrolling the way the Cocoa API does (bug
  33  * 927702).
  34  *
  35  * The swipe direction is either left or right. It is determined before the
  36  * SwipeTracker is created and stays fixed during the swipe.
  37  * During the swipe, the swipe has a current "value" which is between 0 and the
  38  * target value. The target value is either 1 (swiping left) or -1 (swiping
  39  * right) - see SwipeSuccessTargetValue().
  40  * A swipe can either succeed or fail. If it succeeds, the swipe animation
  41  * animates towards the success target value; if it fails, it animates back to
  42  * a value of 0. A swipe can only succeed if the user is swiping in an allowed
  43  * direction. (Since both the allowed directions and the swipe direction are
  44  * known at swipe start time, it's clear from the beginning whether a swipe is
  45  * doomed to fail. In that case, the purpose of the SwipeTracker is to simulate
  46  * a bounce-back animation.)
  47  */
  48 class SwipeTracker final : public nsARefreshObserver {
  49  public:
  50   NS_INLINE_DECL_REFCOUNTING(SwipeTracker, override)
  51
  52   SwipeTracker(nsIWidget& aWidget, const PanGestureInput& aSwipeStartEvent,
  53                uint32_t aAllowedDirections, uint32_t aSwipeDirection);
  54
  55   void Destroy();
  56
  57   nsEventStatus ProcessEvent(const PanGestureInput& aEvent,
  58                              bool aProcessingFirstEvent = false);
  59   void CancelSwipe(const TimeStamp& aTimeStamp);
  60
  61   static WidgetSimpleGestureEvent CreateSwipeGestureEvent(
  62       EventMessage aMsg, nsIWidget* aWidget,
  63       const LayoutDeviceIntPoint& aPosition, const TimeStamp& aTimeStamp);
  64
  65   // nsARefreshObserver
  66   void WillRefresh(mozilla::TimeStamp aTime) override;
  67
  68   static bool CanTriggerSwipe(const PanGestureInput& aPanInput);
  69
  70  protected:
  71   ~SwipeTracker();
  72
  73   bool SwipingInAllowedDirection() const {
  74     return mAllowedDirections & mSwipeDirection;
  75   }
  76   double SwipeSuccessTargetValue() const;
  77   double ClampToAllowedRange(double aGestureAmount) const;
  78   bool ComputeSwipeSuccess() const;
  79   void StartAnimating(double aStartValue, double aTargetValue);
  80   void SwipeFinished(const TimeStamp& aTimeStamp);
  81   void UnregisterFromRefreshDriver();
  82   bool SendSwipeEvent(EventMessage aMsg, uint32_t aDirection, double aDelta,
  83                       const TimeStamp& aTimeStamp);
  84
  85   nsIWidget& mWidget;
  86   RefPtr<nsRefreshDriver> mRefreshDriver;
  87   layers::AxisPhysicsMSDModel mAxis;
  88   const LayoutDeviceIntPoint mEventPosition;
  89   TimeStamp mLastEventTimeStamp;
  90   TimeStamp mLastAnimationFrameTime;
  91   const uint32_t mAllowedDirections;
  92   const uint32_t mSwipeDirection;
  93   double mGestureAmount;
  94   double mCurrentVelocity;
  95   bool mEventsAreControllingSwipe;
  96   bool mEventsHaveStartedNewGesture;
  97   bool mRegisteredWithRefreshDriver;
  98 };
  99
 100 struct SwipeEventQueue {
 101   SwipeEventQueue(uint32_t aAllowedDirections, uint64_t aInputBlockId)
 102       : allowedDirections(aAllowedDirections), inputBlockId(aInputBlockId) {}
 103
 104   nsTArray<PanGestureInput> queuedEvents;
 105   uint32_t allowedDirections;
 106   uint64_t inputBlockId;
 107 };
 108
 109 }  // namespace mozilla
 110
 111 #endif  // SwipeTracker_h