#include <stdio.h>
#include <SDL.h>

#define WIDTH 640
#define HEIGHT 480
#define BPP 4
#define DEPTH 16

void setpixel8(SDL_Surface *screen, int x, int y, Uint8 r, Uint8 g, Uint8 b)
{
  Uint8 *pixmem8;
  Uint32 colour;  
 
   colour = SDL_MapRGB( screen->format, r, g, b );
  
   pixmem8 = (Uint8*) screen->pixels  + y + x;
   *pixmem8 = colour;
}

void setpixel16(SDL_Surface *screen, int x, int y, Uint8 r, Uint8 g, Uint8 b)
{
  Uint16 *pixmem16;
  Uint32 colour;  
 
   colour = SDL_MapRGB( screen->format, r, g, b );
  
   pixmem16 = (Uint16*) screen->pixels  + y + x;
   *pixmem16 = colour;
}

void setpixel32(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 bytesPerPix) {
 
 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/bytesPerPix;
  switch (bytesPerPix)
  {
      case 1:
      {
          for( x = 0; x < screen->w; x++ ) {
             setpixel8(screen, x, ytimesw, (x*x)/256+3*y+h, (y*y)/256+x+h, h);
          }
          break;
      }
      case 2:
      {
          for( x = 0; x < screen->w; x++ ) {
             setpixel16(screen, x, ytimesw, (x*x)/256+3*y+h, (y*y)/256+x+h, h);
          }
          break;
      }
      case 4:
      {
          for( x = 0; x < screen->w; x++ ) {
             setpixel32(screen, x, ytimesw, (x*x)/256+3*y+h, (y*y)/256+x+h, h);
          }
          break;
      }
   }
 }

 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++,screen->format->BytesPerPixel);
    while(SDL_PollEvent(&event)) {
      switch( event.type ) 
	{
	case SDL_QUIT:
	  keypress = 1;
	  break;
	case SDL_KEYDOWN:
	  keypress = 1;
	  break;
	}
    }
  }

 SDL_Quit();
  
  return 0;
}