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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 mozilla_layers_FlingAccelerator_h
#define mozilla_layers_FlingAccelerator_h
#include "mozilla/layers/SampleTime.h"
#include "Units.h"
namespace mozilla {
namespace layers {
struct FlingHandoffState;
* This class is used to track state that is used when determining whether a
* fling should be accelerated.
class FlingAccelerator final {
FlingAccelerator() {}
// Resets state so that the next fling will not be accelerated.
void Reset();
// Returns false after a reset or before the first fling.
bool IsTracking() const { return mIsTracking; }
// Starts a new fling, and returns the (potentially accelerated) velocity that
// should be used for that fling.
ParentLayerPoint GetFlingStartingVelocity(
const SampleTime& aNow, const ParentLayerPoint& aVelocity,
const FlingHandoffState& aHandoffState);
void ObserveFlingCanceled(const ParentLayerPoint& aVelocity) {
mPreviousFlingCancelVelocity = aVelocity;
bool ShouldAccelerate(const SampleTime& aNow,
const ParentLayerPoint& aVelocity,
const FlingHandoffState& aHandoffState) const;
// The initial velocity of the most recent fling.
ParentLayerPoint mPreviousFlingStartingVelocity;
// The velocity that the previous fling animation had at the point it was
// interrupted.
ParentLayerPoint mPreviousFlingCancelVelocity;
// Whether the upcoming fling is eligible for acceleration.
bool mIsTracking = false;
} // namespace layers
} // namespace mozilla
#endif // mozilla_layers_FlingAccelerator_h