File indexing completed on 2024-11-10 04:57:09

 /*
     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
 {
 
 /**
  * The SpringMotion class simulates the motion of a spring along one dimension using the
  * mass-spring-damper model. The sping constant parameter controls the acceleration of the
  * spring. The damping ratio controls the oscillation of the spring.
  */
 class SpringMotion
 {
 public:
     SpringMotion();
     SpringMotion(qreal springConstant, qreal dampingRatio);
 
     /**
      * Advance the simulation by the given @a delta milliseconds.
      */
     void advance(std::chrono::milliseconds delta);
     bool isMoving() const;
 
     /**
      * Returns the current velocity.
      */
     qreal velocity() const;
     void setVelocity(qreal velocity);
 
     /**
      * Returns the current position.
      */
     qreal position() const;
     void setPosition(qreal position);
 
     /**
      * Returns the anchor position. It's the position that the spring is pulled towards.
      */
     qreal anchor() const;
     void setAnchor(qreal anchor);
 
     /**
      * Returns the spring constant. It controls the acceleration of the spring.
      */
     qreal springConstant() const;
 
     /**
      * Returns the damping ratio. It controls the oscillation of the spring. Potential values:
      *
      * - 0 or undamped: the spring will oscillate indefinitely
      * - less than 1 or underdamped: the mass tends to overshoot its starting position, but with
      *   every oscillation some energy is dissipated and the oscillation dies away
      * - 1 or critically damped: the mass will fail to overshoot and make a single oscillation
      * - greater than 1 or overdamped: the mass slowly returns to the anchor position without
      *   overshooting
      */
     qreal dampingRatio() const;
 
     /**
      * If the distance of the mass between two consecutive simulations is smaller than the epsilon
      * value, consider that the mass has stopped moving.
      */
     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