From: Maurizio Colucci <seguso.forever at tin.it>
To: lablgtk at kaba.or.jp
Subject: What's wrong with this code? [GlGtk.area]
Date: Sat, 14 Aug 2004 15:19:27 +0200
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Message-Id: <200408141519.27667.seguso.forever at tin.it>

Hello there! 

I am trying to write a hello-world program with lablgtk2 and GlGtk.area, but 
something is going wrong. The following program should display a GtkGlArea 
with a triangle inside:


let _ =
    
  let delete_event ev =
    print_endline "Delete event occurred";
    flush stdout;
    false (* false = quit *)  in
  let destroy () = print_endline "destroy"; GMain.Main.quit () in
  let locale = GtkMain.Main.init () in
  let window = GWindow.window  () in
  let _ = window#event#connect#delete ~callback:delete_event in
  let _ = window#connect#destroy ~callback:destroy in
  let ar = GlGtk.area [ `RGBA; `DOUBLEBUFFER] ~packing:window#add
        ~show:true () in 
  let my_opengl_reshape ~width ~height = 
    print_endline "my_opengl_reshape called";
    ar#make_current ();
    GlDraw.viewport 0 0 width height;
    GlMat.mode `projection;
    GlMat.load_identity ();
    GlMat.ortho (0.0, float_of_int width)
      (float_of_int height, 0.0) (-1.0, 0.0)  in
  let my_opengl_init () = 
    print_endline "my_opengl_init called";
    ar#make_current ();
    GlDraw.shade_model `smooth;
    GlClear.color (0.1, 0.02, 0.0);
    Gl.disable `depth_test;
    Gl.enable `blend;
    GlFunc.blend_func `src_alpha `one_minus_src_alpha;
    Gl.enable `alpha_test;
    Gl.enable `line_smooth;
    Gl.enable `point_smooth;
    GlFunc.alpha_func `greater 0.0 in
  let my_opengl_display () = 
    ar#make_current ();
    GlClear.clear [`color];
    GlDraw.color (1.0, 1.0, 1.0);
    GlDraw.begins `triangle_strip;
    GlDraw.vertex2 (10.0, 10.0);
    GlDraw.vertex2 (10.0, 90.0);
    GlDraw.vertex2 (90.0, 90.0);
    GlDraw.ends ();
    Gl.flush () ;
    ar#swap_buffers () in
  let _ = ar#connect#reshape ~callback:my_opengl_reshape in
  let _ = ar#connect#realize ~callback: my_opengl_init in
  let _ = ar#connect#display ~callback: my_opengl_display in
  window#show ();
  GMain.Main.main ()

But this only displays an empty window. The gl area is not visible.

The output is:

debian:/dat/pub/src/by-mau/adventure/src/ocaml# ./test.exe
GlGtk-WARNING **: could not make current
GlGtk-WARNING **: could not make current
GlGtk-WARNING **: could not make current
Delete event occurred
destroy


Apparently the callbacks are not being called. Furthermore, there are problems 
with make_current. The output stays the same if I omit the call to 
   
   ar#make_current()

I am really stuck. 

Does the program work on your machine?
(I am using debian sid with the nvidia driver)

What can the problem be?

Thanks for any help.
Maurizio