framelimiter.h

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#ifndef GFX_FRAMELIMITER_H
#define GFX_FRAMELIMITER_H

#include "common/system.h"

namespace Graphics {

class FrameLimiter {
public:
    FrameLimiter(OSystem *system, const uint framerate, const bool deferToVsync = true);
    void initialize();
    void initialize(const uint framerate);

    uint startFrame();

    bool delayBeforeSwap();
    void pause(bool pause);
    uint getLastFrameDuration() const {
        return _frameDuration;
    }
    uint getLastDrawDuration() const {
        return _drawDuration;
    }
    uint getLastLoopDuration() const {
        return _loopDuration;
    }
    bool isEnabled() const {
        return _enabled;
    }

private:
    OSystem *_system;

    bool _enabled;
    bool _deferToVsync;
    uint _frameStart = 0;  // Time at which screen update completed and startFrame() was called; start of next cycle of game logic
    uint _frameLimit = 0;  // Target frame duration to achieve specified FPS
    uint _frameDuration = 0; // Duration of previous frame between successive startFrame() calls; total game logic, delay (if any) and screen update time
    uint _drawStart = 0;  // Time at which delayBeforeSwap() returns
    uint _drawDuration = 0;  // Measured screen update time
    uint _loopDuration = 0;  // Duration of last game logic cycle, from when startFrame() was called to when delayBeforeSwap() was called
    int _delay = 0; // Time to delay before returning from delayBeforeSwap()
    uint _now = 0; // Current time
};

} // End of namespace Graphics

#endif // GFX_FRAMELIMITER_H