[Caml-list] f#/mono vs ocaml runtime system - open gl animation screen tearing.

[Peter Ronnquist <peter.ronnquist@gmail.com>]

While making the simple examples for SDL+opengl for the C language I
realized that even the C version showed "stuttering" but the fsharp
version is completely smooth and synced to the vblank.
Appearantly the fsharp version somehow manages to sync to the vblank
probably thanks to  the openTK api:

  do base.VSync <- VSyncMode.On

I had to configure the nvidia driver with
X Server XVideo Settings:
Video Texture Adaptor -> Sync to VBlank
Video Blitter Adaptor Settings -> Sync to VBlank

OpenGL Settings
Performance -> Sync to VBlank
                   -> Allow Flipping

then both the C sdl opengl version and ocaml sdl openg version worked smoothly.

So to sum it up, I had the wrong setting of the nvidia driver and was
fooled sinced the fsharp version still synced with the vblank.

I am posting the ocaml sdl openg test program here in case someone
would like to try it on debian 6 squeeze:

Sorry for the "false alarm", it was not ocamls fault,  and thank you
for the good advice.

(*

 Using opengl, sdl and revised syntax.

 Compile with:

 camlopt -pp camlp4r -I . -I +sdl -I +lablgl bigarray.cmxa sdl.cmxa
lablgl.cmxa unix.cmxa  str.cmxa simple2.ml -o simple2

*)

open Sdlevent;
open Sdlkey;
open Sdlgl;

(* Window size in pixels *)
value x_size_window = 512;
value y_size_window = 512;

(* Space coordinates *)
value upper_size = 1.5;
value lower_size = -1.5;
value left_size = -1.5;
value right_size = 1.5;

value init_gl width height = do {
  GlDraw.viewport ~x:0 ~y:0 ~w:width ~h:height;
  GlClear.color (0.0, 0.0, 0.0) ~alpha:0.0;
  GlClear.clear [`color; `depth];
  GlDraw.shade_model `smooth;
  GlMat.load_identity ();

  GlClear.color (0.1, 0.3, 0.1);
  GlDraw.shade_model `smooth;
};

value time =
  let start = Unix.gettimeofday () in fun () -> Unix.gettimeofday () -. start
;

value key_left_is_down = ref False;
value key_right_is_down = ref False;


(* Start of program *)
value () =

    do {

    Sdl.init [`VIDEO];
    at_exit Sdl.quit;


    set_attr [DOUBLEBUFFER True];
    ignore (Sdlvideo.set_video_mode x_size_window y_size_window
[`OPENGL ; `DOUBLEBUF ; `RESIZABLE ; `HWSURFACE]);
    init_gl x_size_window y_size_window;

    let render () =
      do {

    GlMat.mode `projection;
    GlMat.load_identity ();
    GluMat.ortho2d ~x:(-1.5, 1.5) ~y:(-1.5, 1.5);
    GlMat.mode `modelview;
    GlMat.load_identity ();
    GlClear.clear [ `color ; `depth];

    GlMat.translate ~x:(sin (time ()*.2.0) *. 1.) ~z:1. ();
    GlDraw.begins `quads;
      List.iter GlDraw.vertex2 [
        ( -0.2, -0.5);
	  (0.2, -0.5);
	    (0.2, 0.5);
	      (-0.2, 0.5)];

    GlDraw.ends ();
    Gl.flush ();
    Sdlgl.swap_buffers ();

    }
    in
      let quit_loop = ref False in
      while not quit_loop.val  do {
	(* Calculate elapsed time since last rendering *)
	  render ();
	

        match Sdlevent.poll () with
        [ Some( KEYDOWN {keysym = KEY_ESCAPE} ) -> do {
          print_endline "You pressed escape! The fun is over now.";
          quit_loop.val := True
        }
        | Some( KEYDOWN {keysym = KEY_LEFT} ) -> do {
          key_left_is_down.val := True;
        }
        | Some( KEYDOWN {keysym = KEY_RIGHT} ) -> do {
          key_right_is_down.val := True;
        }
        | Some( KEYUP {keysym = KEY_LEFT} ) -> do {
          key_left_is_down.val := False;
        }
        | Some( KEYUP {keysym = KEY_RIGHT} ) -> do {
          key_right_is_down.val := False;
        }
        | Some event -> do {
          print_endline (string_of_event event);
        }
        | None -> ()
        ]

      };

};