GameClock.cpp

Go to the documentation of this file.

/*
 * =====================================================================================
 *
 *       Filename:  GameClock.cpp
 *
 *    Description:
 *
 *        Created:  14/12/2014 13:42:26
 *
 *         Author:  Quentin Bazin, <quent42340@gmail.com>
 *
 * =====================================================================================
 */
#include "gk/core/SDLHeaders.hpp"
#include "gk/core/GameClock.hpp"

namespace gk {

u32 GameClock::ticks = 0;

u32 GameClock::getTicks(bool realTime) {
    if(realTime) {
        return SDL_GetTicks();
    } else {
        return ticks;
    }
}

void GameClock::measureLastFrameDuration() {
    u32 now = getTicks(true) - m_timeDropped;
    u32 lastFrameDuration = now - m_lastFrameDate;

    m_lastFrameDate = now;
    m_lag += lastFrameDuration;

    if(m_lag >= 200) {
        m_timeDropped += m_lag - m_timestep;
        m_lag = m_timestep;
        m_lastFrameDate = getTicks(true) - m_timeDropped;
    }
}

void GameClock::updateGame(std::function<void(void)> updateFunc) {
    m_numUpdates = 0;

    while(m_lag >= m_timestep && m_numUpdates < 10) {
        ticks += m_timestep;

        updateFunc();

        m_lag -= m_timestep;
        m_numUpdates++;
    }
}

void GameClock::drawGame(std::function<void(void)> drawFunc) {
    if(m_numUpdates > 0) {
        drawFunc();
    }

    waitForNextFrame();
}

void GameClock::waitForNextFrame() {
    u32 lastFrameDuration = getTicks(true) - m_timeDropped - m_lastFrameDate;

    if(lastFrameDuration < m_timestep) {
        SDL_Delay(m_timestep - lastFrameDuration);
    }

    measureLastFrameDuration();
}

} // namespace gk