springmotion.h

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/*
    SPDX-FileCopyrightText: 2022 Vlad Zahorodnii <vlad.zahorodnii@kde.org>
 
    SPDX-License-Identifier: GPL-2.0-or-later
*/
 
#pragma once
 
#include <QtGlobal>
 
#include <chrono>
 
namespace KWin
{
 
class SpringMotion
{
public:
    SpringMotion();
    SpringMotion(qreal springConstant, qreal dampingRatio);
 
    void advance(std::chrono::milliseconds delta);
    bool isMoving() const;
 
    qreal velocity() const;
    void setVelocity(qreal velocity);
 
    qreal position() const;
    void setPosition(qreal position);
 
    qreal anchor() const;
    void setAnchor(qreal anchor);
 
    qreal springConstant() const;
 
    qreal dampingRatio() const;
 
    qreal epsilon() const;
    void setEpsilon(qreal epsilon);
 
private:
    struct State
    {
        qreal position;
        qreal velocity;
    };
 
    struct Slope
    {
        qreal dp;
        qreal dv;
    };
 
    State integrate(const State &state, qreal dt);
    Slope evaluate(const State &state, qreal dt, const Slope &slope);
 
    State m_prev;
    State m_next;
    qreal m_t;
    qreal m_timestep;
 
    qreal m_anchor;
    qreal m_springConstant;
    qreal m_dampingRatio;
    qreal m_dampingCoefficient;
    qreal m_epsilon;
};
 
} // namespace KWin