forked from mirrors/gecko-dev
a41405e106
This is a prerequisite change to keep momentum scrolls happening on the other axis where no overscroll animation is running. Differential Revision: https://phabricator.services.mozilla.com/D110793
83 lines
2.3 KiB
C++
83 lines
2.3 KiB
C++
/* -*- 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_AxisPhysicsMSDModel_h
|
|
#define mozilla_layers_AxisPhysicsMSDModel_h
|
|
|
|
#include "AxisPhysicsModel.h"
|
|
|
|
namespace mozilla {
|
|
namespace layers {
|
|
|
|
/**
|
|
* AxisPhysicsMSDModel encapsulates a 1-dimensional MSD (Mass-Spring-Damper)
|
|
* model. A unit mass is assumed.
|
|
*/
|
|
class AxisPhysicsMSDModel : public AxisPhysicsModel {
|
|
public:
|
|
AxisPhysicsMSDModel(double aInitialPosition, double aInitialDestination,
|
|
double aInitialVelocity, double aSpringConstant,
|
|
double aDampingRatio);
|
|
|
|
virtual ~AxisPhysicsMSDModel();
|
|
|
|
/**
|
|
* Gets the raw destination of this axis at this moment.
|
|
*/
|
|
double GetDestination() const;
|
|
|
|
/**
|
|
* Sets the raw destination of this axis at this moment.
|
|
*/
|
|
void SetDestination(double aDestination);
|
|
|
|
/**
|
|
* Returns true when the position is close to the destination and the
|
|
* velocity is low.
|
|
*/
|
|
bool IsFinished(double aSmallestVisibleIncrement) const;
|
|
|
|
protected:
|
|
double Acceleration(const State& aState) override;
|
|
|
|
private:
|
|
/**
|
|
* mDestination represents the target position and the resting position of
|
|
* the simulated spring.
|
|
*/
|
|
double mDestination;
|
|
|
|
/**
|
|
* Greater values of mSpringConstant result in a stiffer / stronger spring.
|
|
*/
|
|
double mSpringConstant;
|
|
|
|
/**
|
|
* mSpringConstantSqrtTimesTwo is calculated from mSpringConstant to reduce
|
|
* calculations performed in the inner loop.
|
|
*/
|
|
double mSpringConstantSqrtXTwo;
|
|
|
|
/**
|
|
* Damping Ratio: http://en.wikipedia.org/wiki/Damping_ratio
|
|
*
|
|
* When mDampingRatio < 1.0, this is an under damped system.
|
|
* - Overshoots destination and oscillates with the amplitude gradually
|
|
* decreasing to zero.
|
|
*
|
|
* When mDampingRatio == 1.0, this is a critically damped system.
|
|
* - Reaches destination as quickly as possible without oscillating.
|
|
*
|
|
* When mDampingRatio > 1.0, this is an over damped system.
|
|
* - Reaches destination (exponentially decays) without oscillating.
|
|
*/
|
|
double mDampingRatio;
|
|
};
|
|
|
|
} // namespace layers
|
|
} // namespace mozilla
|
|
|
|
#endif
|