ScrollAnimationMSDPhysics.h

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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_layout_ScrollAnimationMSDPhysics_h_

#define mozilla_layout_ScrollAnimationMSDPhysics_h_

#include "ScrollAnimationPhysics.h"

#include "mozilla/layers/AxisPhysicsMSDModel.h"

namespace mozilla {

// This class implements a cubic MSD timing function and automatically

// adapts the animation duration based on the scrolling rate.

class ScrollAnimationMSDPhysics final : public ScrollAnimationPhysics {

 public:

  typedef mozilla::layers::AxisPhysicsMSDModel AxisPhysicsMSDModel;

  explicit ScrollAnimationMSDPhysics(const nsPoint& aStartPos);

  void Update(const TimeStamp& aTime, const nsPoint& aDestination,

              const nsSize& aCurrentVelocity) override;

  void ApplyContentShift(const CSSPoint& aShiftDelta) override;

  // Get the velocity at a point in time in nscoords/sec.

  nsSize VelocityAt(const TimeStamp& aTime) override;

  // Returns the expected scroll position at a given point in time, in app

  // units, relative to the scroll frame.

  nsPoint PositionAt(const TimeStamp& aTime) override;

  bool IsFinished(const TimeStamp& aTime) override {

    SimulateUntil(aTime);

    return mModelX.IsFinished(1) && mModelY.IsFinished(1);

 protected:

  // A wrapper around AxisPhysicsMSDModel which takes additional steps to avoid

  // oscillating motion.

  class NonOscillatingAxisPhysicsMSDModel : public AxisPhysicsMSDModel {

   public:

    NonOscillatingAxisPhysicsMSDModel(double aInitialPosition,

                                      double aInitialDestination,

                                      double aInitialVelocity,

                                      double aSpringConstant,

                                      double aDampingRatio);

};

  double ComputeSpringConstant(const TimeStamp& aTime);

  void SimulateUntil(const TimeStamp& aTime);

  TimeStamp mPreviousEventTime;

  TimeDuration mPreviousDelta;

  TimeStamp mStartTime;

  nsPoint mStartPos;

  nsPoint mDestination;

  TimeStamp mLastSimulatedTime;

  NonOscillatingAxisPhysicsMSDModel mModelX;

  NonOscillatingAxisPhysicsMSDModel mModelY;

  bool mIsFirstIteration;

};

}  // namespace mozilla

#endif  // mozilla_layout_ScrollAnimationMSDPhysics_h_