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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef SwipeTracker_h
+#define SwipeTracker_h
+
+#include "EventForwards.h"
+#include "mozilla/layers/AxisPhysicsMSDModel.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/TimeStamp.h"
+#include "nsRefreshObservers.h"
+#include "Units.h"
+
+class nsIWidget;
+class nsRefreshDriver;
+
+namespace mozilla {
+
+class PanGestureInput;
+
+/**
+ * SwipeTracker turns PanGestureInput events into swipe events
+ * (WidgetSimpleGestureEvent) and dispatches them into Gecko.
+ * The swiping behavior mirrors the behavior of the Cocoa API
+ * -[NSEvent
+ * trackSwipeEventWithOptions:dampenAmountThresholdMin:max:usingHandler:].
+ * The advantage of using this class over the Cocoa API is that this class
+ * properly supports submitting queued up events to it, and that it hopefully
+ * doesn't intermittently break scrolling the way the Cocoa API does (bug
+ * 927702).
+ *
+ * The swipe direction is either left or right. It is determined before the
+ * SwipeTracker is created and stays fixed during the swipe.
+ * During the swipe, the swipe has a current "value" which is between 0 and the
+ * target value. The target value is either 1 (swiping left) or -1 (swiping
+ * right) - see SwipeSuccessTargetValue().
+ * A swipe can either succeed or fail. If it succeeds, the swipe animation
+ * animates towards the success target value; if it fails, it animates back to
+ * a value of 0. A swipe can only succeed if the user is swiping in an allowed
+ * direction. (Since both the allowed directions and the swipe direction are
+ * known at swipe start time, it's clear from the beginning whether a swipe is
+ * doomed to fail. In that case, the purpose of the SwipeTracker is to simulate
+ * a bounce-back animation.)
+ */
+class SwipeTracker final : public nsARefreshObserver {
+ public:
+ NS_INLINE_DECL_REFCOUNTING(SwipeTracker, override)
+
+ SwipeTracker(nsIWidget& aWidget, const PanGestureInput& aSwipeStartEvent,
+ uint32_t aAllowedDirections, uint32_t aSwipeDirection);
+
+ void Destroy();
+
+ nsEventStatus ProcessEvent(const PanGestureInput& aEvent,
+ bool aProcessingFirstEvent = false);
+ void CancelSwipe(const TimeStamp& aTimeStamp);
+
+ static WidgetSimpleGestureEvent CreateSwipeGestureEvent(
+ EventMessage aMsg, nsIWidget* aWidget,
+ const LayoutDeviceIntPoint& aPosition, const TimeStamp& aTimeStamp);
+
+ // nsARefreshObserver
+ void WillRefresh(mozilla::TimeStamp aTime) override;
+
+ static bool CanTriggerSwipe(const PanGestureInput& aPanInput);
+
+ protected:
+ ~SwipeTracker();
+
+ bool SwipingInAllowedDirection() const {
+ return mAllowedDirections & mSwipeDirection;
+ }
+ double SwipeSuccessTargetValue() const;
+ double ClampToAllowedRange(double aGestureAmount) const;
+ bool ComputeSwipeSuccess() const;
+ void StartAnimating(double aStartValue, double aTargetValue);
+ void SwipeFinished(const TimeStamp& aTimeStamp);
+ void UnregisterFromRefreshDriver();
+ bool SendSwipeEvent(EventMessage aMsg, uint32_t aDirection, double aDelta,
+ const TimeStamp& aTimeStamp);
+
+ nsIWidget& mWidget;
+ RefPtr<nsRefreshDriver> mRefreshDriver;
+ layers::AxisPhysicsMSDModel mAxis;
+ const LayoutDeviceIntPoint mEventPosition;
+ TimeStamp mLastEventTimeStamp;
+ TimeStamp mLastAnimationFrameTime;
+ const uint32_t mAllowedDirections;
+ const uint32_t mSwipeDirection;
+ double mGestureAmount;
+ double mCurrentVelocity;
+ bool mEventsAreControllingSwipe;
+ bool mEventsHaveStartedNewGesture;
+ bool mRegisteredWithRefreshDriver;
+};
+
+struct SwipeEventQueue {
+ SwipeEventQueue(uint32_t aAllowedDirections, uint64_t aInputBlockId)
+ : allowedDirections(aAllowedDirections), inputBlockId(aInputBlockId) {}
+
+ nsTArray<PanGestureInput> queuedEvents;
+ uint32_t allowedDirections;
+ uint64_t inputBlockId;
+};
+
+} // namespace mozilla
+
+#endif // SwipeTracker_h