Image noise/OCaml/Alleg

This content is a Work In Progress. Please help to fix it and remove this message.

<lang ocaml>(* modified/adapted from the sample program exdbuf.c by Shawn Hargreaves,

  from the Allegro library, which is provided under the giftware licence. *)

open Allegro

let () =

 allegro_init();
 install_timer();
 install_keyboard();

 begin
   try set_gfx_mode GFX_AUTODETECT_WINDOWED 320 240 0 0;
   with _ ->
     try set_gfx_mode GFX_SAFE 320 240 0 0
     with _ ->
       set_gfx_mode GFX_TEXT 0 0 0 0;
       allegro_message ("Unable to set any graphic mode\n" ^
                        (get_allegro_error()) ^ "\n");
       exit 1
 end;

 set_palette(get_desktop_palette());

 let screen, font = get_screen(), get_font() in
 let screen_w, screen_h = get_screen_width(), get_screen_height() in

 (* allocate the memory buffer *)
 let buffer = create_bitmap screen_w screen_h in

 let black = (makecol 0 0 0)
 and white = (makecol 255 255 255) in

 (* we choose the double buffering method *)
 clear_keybuf();
 let c = 32 + (retrace_count()) in
 let rec main_loop n =
   clear_to_color buffer white;
   for x = 0 to screen_w do
     for y = 0 to screen_h do
       if Random.bool() then
         putpixel buffer x y black; 
     done;
   done;
   blit buffer screen 0 0 0 0 screen_w screen_h;

   if not(keypressed())
   && ((retrace_count()) - c) <= (320 + 32)
   then main_loop (succ n)
   else (n)
 in
 let n = main_loop 0 in

 (* just print the number of frames displayed *)
 print_int n;
 print_newline();

 (* release the memory buffer *)
 destroy_bitmap buffer</lang>

Run that as a script with the command:

ocaml -I $(ocamlfind query allegro) allegro.cma noise_fps_alleg.ml

This is a work in progress version, it only prints the number of frames displayed, but we could still use the command time and make the calculus with the ocaml top-level.

TODO: use the Allegro timer system.