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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 */
#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 {
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);
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