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

#define WIDTH   800
#define HEIGHT  600

GLuint vs, fs;

void init(int width, int height)
{
    glClearColor (0.0, 0.0, 0.0, 0.0);
    glEnable(GL_DEPTH_TEST);
    glViewport(0, 0, WIDTH, HEIGHT);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho((float)-width/(float)height, (float)width/(float)height,
            -1, 1, -1, 1);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    SDL_GL_SwapBuffers();
}

int main(int argc, char *argv[])
{
    if (SDL_Init(SDL_INIT_VIDEO))
    {
        printf("Failed to initialize SDL!\n");
        return 1;
    }

    atexit(SDL_Quit);

    SDL_Surface *screen;
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    if (!(screen = SDL_SetVideoMode(WIDTH, HEIGHT, 16, SDL_OPENGL)))
    {
        printf("Failed to set video mode!\n");
        SDL_Quit();
        return 2;
    }
    SDL_WM_SetCaption(argv[0], argv[0]);

    init(WIDTH, HEIGHT);
    display();
    SDL_Event event;
    while (SDL_WaitEvent(&event))
    {
        if (event.type == SDL_QUIT)
            break;
        else if (event.type == SDL_KEYDOWN)
        {
            if (event.key.keysym.sym == SDLK_ESCAPE)
                break;
        }
    }
}