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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 mozilla_layers_VelocityTracker_h
#define mozilla_layers_VelocityTracker_h
#include <utility>
#include <cstdint>
#include "Axis.h"
#include "mozilla/Attributes.h"
#include "nsTArray.h"
namespace mozilla {
namespace layers {
class SimpleVelocityTracker : public VelocityTracker {
public:
explicit SimpleVelocityTracker(Axis* aAxis);
void StartTracking(ParentLayerCoord aPos, TimeStamp aTimestamp) override;
Maybe<float> AddPosition(ParentLayerCoord aPos,
TimeStamp aTimestamp) override;
Maybe<float> ComputeVelocity(TimeStamp aTimestamp) override;
void Clear() override;
private:
void AddVelocityToQueue(TimeStamp aTimestamp, float aVelocity);
float ApplyFlingCurveToVelocity(float aVelocity) const;
// The Axis that uses this velocity tracker.
// This is a raw pointer because the Axis owns the velocity tracker
// by UniquePtr, so the velocity tracker cannot outlive the Axis.
Axis* MOZ_NON_OWNING_REF mAxis;
// A queue of (timestamp, velocity) pairs; these are the historical
// velocities at the given timestamps. Velocities are in screen pixels per ms.
// This member can only be accessed on the controller/UI thread.
nsTArray<std::pair<TimeStamp, float>> mVelocityQueue;
// mVelocitySampleTime and mVelocitySamplePos are the time and position
// used in the last velocity sampling. They get updated when a new sample is
// taken (which may not happen on every input event, if the time delta is too
// small).
TimeStamp mVelocitySampleTime;
ParentLayerCoord mVelocitySamplePos;
};
} // namespace layers
} // namespace mozilla
#endif
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