{  DEMO PROGRAM MADE BY MATTHIAS MOLSKI, October 2007
   VISIT: http://www.fp.sdl.de.vu/  }

PROGRAM chap4;
USES CRT, SDL;

VAR
screen:pSDL_SURFACE;
pixellocation:^LONGWORD;
pixelcolor,i:LONGWORD;

BEGIN

SDL_INIT(SDL_INIT_VIDEO);
screen:=SDL_SETVIDEOMODE(200,200,32,SDL_SWSURFACE);
IF screen=NIL THEN HALT;

NEW(pixellocation);
WRITE('Pitch value: ',screen^.pitch DIV screen^.format^.BytesPerPixel);

i:=0;
REPEAT
inc(i); IF i>39999 THEN i:=0;

pixellocation:=screen^.pixels+i;               //delete old pixel
pixelcolor:=SDL_MAPRGB(screen^.format,0,0,0);
pixellocation^:=pixelcolor;


pixellocation:=screen^.pixels+i+1;             //draw new pixel
pixelcolor:=SDL_MAPRGB(screen^.format,255,255,0);
pixellocation^:=pixelcolor;

SDL_FLIP(screen);
SDL_DELAY(5);
UNTIL keypressed;

DISPOSE(pixellocation);
SDL_FREESURFACE(screen);
SDL_QUIT;
END.