#include "SDL.h"
#include <stdlib.h>

#define WIDTH 640
#define HEIGHT 480
#define BPP 4
#define DEPTH 32
 
void setpixel(SDL_Surface *screen, int x, int y, Uint8 r, Uint8 g, Uint8 b)
{
    Uint32 *pixmem32;
    Uint32 colour;  
 
    colour = SDL_MapRGB( screen->format, r, g, b );
 
    pixmem32 = (Uint32*) screen->pixels  + y + x;
    *pixmem32 = colour;
}
 
 
void DrawScreen(SDL_Surface* screen, int h)
{
    int x, y, ytimesw;
 
    if(SDL_MUSTLOCK(screen))
    {
        if(SDL_LockSurface(screen) < 0) return;
    }
 
    for(y = 0; y < screen->h; y++ )
    {
        ytimesw = y*screen->pitch/BPP;
        for( x = 0; x < screen->w; x++ )
        {
            setpixel(screen, x, ytimesw, (x*x)/256+3*y+h, (y*y)/256+x+h, h);
        }
    }
    if(SDL_MUSTLOCK(screen)) SDL_UnlockSurface(screen);
 
    SDL_Flip(screen);
}
 
 
int main(int argc, char* argv[])
{
    SDL_Surface *screen;
    SDL_Event event;
 
    int keypress = 0;
    int h=0;
 
    if (SDL_Init(SDL_INIT_VIDEO) < 0 ) return 1;
   
    if (!(screen = SDL_SetVideoMode(WIDTH, HEIGHT, DEPTH, SDL_FULLSCREEN|SDL_HWSURFACE)))
    {
        SDL_Quit();
        return 1;
    }
 
    while(!keypress)
    {
         DrawScreen(screen,h++);
         while(SDL_PollEvent(&event))
         {      
              switch (event.type)
              {
                  case SDL_QUIT:
                      keypress = 1;
                      break;
                  case SDL_KEYDOWN:
                       keypress = 1;
                       break;
              }
         }
    }
 
    SDL_Quit();
    return 0;
}
