game_loop.h

// © Joseph Cameron - All Rights Reserved
 
#ifndef GDK_GAME_LOOP_H
#define GDK_GAME_LOOP_H
 
#include <chrono>
#include <functional>
#include <thread>
 
namespace gdk {
    void game_loop(const float aMaxFramesPerSecond, 
        std::function<bool /*shouldClose*/(const double /*time*/, const double /*delta time*/)> aLoopBehavior) {
        bool shouldClose(false);
        double time(0);
        double deltaTime(0);
        double frameTime(1.0 / aMaxFramesPerSecond);
 
        while (!shouldClose) {
            using namespace std::chrono;
 
            steady_clock::time_point currentFrameStartTimePoint(steady_clock::now());
 
            shouldClose = aLoopBehavior(time, deltaTime);
 
            time += deltaTime;
 
            while (true) {
                steady_clock::time_point currentTimePoint(steady_clock::now());
 
                duration<double> timeSpentOnCurrentFrame = duration_cast<duration<double>>(currentTimePoint - currentFrameStartTimePoint);
 
                if (deltaTime = timeSpentOnCurrentFrame.count(); deltaTime >= frameTime) break;
                
                std::this_thread::sleep_for(1s * (frameTime - deltaTime) / 10.0);
            }
        }
    }
}
 
#endif