update thread setup with a good cap

[physics.git] / src / main.cpp

/*
 *  Copyright (C) 2008 Patrik Gornicz, Gornicz_P (at) hotmail (dot) com.
 *
 *  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/>.
 */

#include <GL/gl.h>
#include <GL/glu.h>
#include <SDL/SDL.h>

#include "debug.h"
#include "handleSignal.h"

#include "game.h"
#include "ticks.h"

#include "graphics/graphics.h"
#include "input/inputManager.h"
#include "config/config.h"

/// ***** Private Method Headers *****

void init();

void sighandler( int sig );

void run();
void clean();

void updateFPSCounters();

void handleInput();
void update(float);
void draw();

/// ***** Private Variables *****

// variable used to determine if it is time to shutdown
bool is_Running;

/* Values for the main game loop
 * target_UPS := the amount of updates that is wanted in one second
 *
 * ups := updates per second for the last second
 * fps := frames per second for the last second
 * update_Count := counts this seconds updates
 * draw_Count  := counts this seconds draws
 * last_Second := stores the time of the last second, used for ups and fps
 */
int target_UPS = 100;
float update_Wait = 0;

int ups, fps;
int update_Count, draw_Count;
MICRO last_Second;

const int min_wait_milli = 20;
const int min_wait_micro = min_wait_milli * 1000;
const float game_step    = 10;

int startUpdateThread(void*);
int startDrawThread(void*);

/// ***** MAIN Method *****
int main(int argc, char** args)
{
    init();
    run();
    clean();
    return 0;
}

/// ***** Initializers/Cleaners *****

void init()
{
    installSignal();

    graphics::init();
    DPF(0, "Graphics initialized");

    game::init();
    DPF(0, "Game initialized");

    input::init();
    DPF(0, "Input initialized");

    cfg::init();
    DPF(0, "Configs initialized");

    DPF(0, "Initialization Complete");
}

void clean()
{
    DPF(0, "Cleaning up");

    cfg::clean();

    input::clean();

    game::clean();

    graphics::clean();
}

/// ***** Private Methods *****

void run()
{
    is_Running = true;

    SDL_Thread* updates = SDL_CreateThread(startUpdateThread, NULL);

    // for some reason this needs to be on the main thread ...?
    startDrawThread(NULL);

    SDL_WaitThread(updates, NULL);
}

void updateFPSCounters()
{
    // Check if a second has passed to recalculate UPS and FPS
    if (tickCountMicro() - last_Second >= 1000000)
    {
        ups = update_Count;
        fps = draw_Count;

        // NOT thread safe, but they're estimates anyways
        update_Count -= ups;
        draw_Count -= fps;

        last_Second = tickCountMicro();

#ifdef FPSUPS
        cout << "ups:\t" << ups << endl;
        cout << "fps:\t" << fps << endl;
#endif
    }
}

void handleInput()
{
    input::update();

    game::handleInput();

    if(cfg::endGame())
        is_Running = false;
}

void update(float time_step)
{
    game::update(time_step);
    update_Count++;
}

void draw()
{
    game::draw();

    SDL_GL_SwapBuffers();

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    draw_Count++;
}

int startUpdateThread(void*)
{
    last_Second = tickCountMicro();

    while(is_Running)
    {
        MICRO time = tickCountMicro();
            handleInput();
            update(game_step);

            updateFPSCounters();
        time = tickCountMicro() - time;

        float wait = (1000000.0 / target_UPS - time);
        update_Wait += 0 < wait ? wait : 0;

        while(min_wait_micro < update_Wait)
        {
            update_Wait -= min_wait_micro;
            SDL_Delay(min_wait_milli);
        }
    }

    return 0;
}

int startDrawThread(void*)
{
    while(is_Running)
    {
        draw();
    }

    return 0;
}