#include <SDL/SDL.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

void
Lock(SDL_Surface *screen)
{
	if (SDL_MUSTLOCK(screen))
		if (SDL_LockSurface(screen) < 0) {
			printf ("Couldn't lock surface: %s\n",
				SDL_GetError());
			return;
		}
}

void
Unlock(SDL_Surface *screen)
{
	if (SDL_MUSTLOCK(screen))
		SDL_UnlockSurface(screen);
}

Uint32
GetColor(SDL_Surface *screen,
                        Uint8 R, Uint8 G, Uint8 B)
{
	return SDL_MapRGB(screen->format, R, G, B);
}

void
DrawPixel(SDL_Surface *screen, int x, int y,
                       Uint8 R, Uint8 G, Uint8 B)
{
	Lock(screen);
	switch (screen->format->BytesPerPixel) {
	case 1:
	{
		Uint8 *bufp;
		bufp = screen->pixels + y * screen->pitch + x;
		*bufp = GetColor(screen, R, G, B);
	}
	break;
	case 2:
	{
		Uint16 *bufp;
		bufp = screen->pixels + y * screen->pitch / 2 + x;
		*bufp = GetColor(screen, R, G, B);
	}
	break;
	case 3:
	{
		printf("24 bit mode is not supported\n");
		exit(1);
	}
	break;
	case 4:
	{
		Uint32 *bufp;
		bufp = screen->pixels + y * screen->pitch / 4 + x;
		*bufp = GetColor(screen, R, G, B);
	}
	break;
	default:
		printf("Unknown Depth\n");
	break;
	}
	Unlock(screen);
	SDL_UpdateRect(screen, x, y, 1, 1);
}

int
main()
{
	SDL_Surface *screen;
	int i, points = 50000;

	if(SDL_Init (SDL_INIT_VIDEO) != 0) {
		printf("Couldn't initialize SDL: %s\n", SDL_GetError());
		return 1;
	}

	atexit(SDL_Quit);

	if ((screen = SDL_SetVideoMode(320, 200, 8, SDL_SWSURFACE)) == NULL) {
		printf("Couldn't set Video Mode: %s\n", SDL_GetError());
		return 1;
	}

/*
	for (i = 0; i < points; i++) {
		DrawPixel(screen, rand () % 320, rand () % 200, 0, 0, 255);
		DrawPixel(screen, rand () % 320, rand () % 200, 0, 255, 0);
		DrawPixel(screen, rand () % 320, rand () % 200, 255, 0, 0);
		DrawPixel(screen, rand () % 320, rand () % 200, 255,255,0);
	}
*/
	for (i = 0; i < 320; i++) {
		int j;
		for (j = 0; j < 200; j++)
			DrawPixel(screen, i, j, 255, 255, 255);
	}

	SDL_Delay (1000);
	return 0;
}