To: luther at dpt-info.u-strasbg.fr
Cc: lablgtk at kaba.or.jp
Subject: Re: resize event?
In-Reply-To: <20010109185300.A888 at lambda.u-strasbg.fr>
References: <4.3.2.7.2.20010105002151.00baf5c0 at shell16.ba.best.com>
	<20010109185300.A888@lambda.u-strasbg.fr>
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Message-Id: <20010110204647A.garrigue at kurims.kyoto-u.ac.jp>
Date: Wed, 10 Jan 2001 20:46:47 +0900
From: Jacques Garrigue <garrigue at kurims.kyoto-u.ac.jp>
Lines: 88

From: Sven LUTHER <luther at dpt-info.u-strasbg.fr>

> Now, i have also a question :
> 
> i am using a GlArea widget to do OpenGL drawing into, i create it with :
> 
>     let area = GlGtk.area [`DOUBLEBUFFER;`RGBA;`DEPTH_SIZE 1]
>       ~width:600 ~height:400 ()
> 
> and do some matrix stuff in it like it is done in the GL examples :
> 
>     ignore (area#event#connect#after#configure ~callback:
>       begin function _ ->
>         GlMat.mode `projection;
>         GlMat.load_identity ();
>         GlMat.ortho ~x:(-1.0,1.0) ~y:(-1.0,1.0) ~z:(-1.0,1.0);
>         false
>       end);

If you use GlGtk.area, then you should rather use #connect#display and
#connect#reshape than #event#connect#configure. Those two special
events do extra administrative work, so that they will work even you
have several Gl areas in you program.

> now, if i understood it well, (fst ~x, fst ~y) is the coordinate of the lower
> left corner of the glArea and (snd ~x, snd ~y) is the coordinate of the upper
> right corner of the GLArrea.

This should be correct.

> The problem with this is that :
> 
>   - the glarea being 600x400, this gives me an non-orthogonal view, which
>     don't have correct 90° angles.

Seems logical.

>   - when i use the button_press callback, i get coordinates in the -1,1 range.
>   - when i resize window, i get a larger window, but the button_press event
>     still seem to be providing me the older values, not sure though.

You should reconfigure when shape changes.

> if i do :
> 
>         GlMat.ortho ~x:(-1.5,1.5) ~y:(-1.0,1.0) ~z:(-1.0,1.0);
> 
> i think i will preserver the correct ratio, but nothing happens.

Very strange. It works for me.
There maybe some timing problems: everything should be done in the
right order.
 I just modified scene.ml in lablgl, to have it work with lablgtk, and
everything is OK.

<code>
open GMain

let main () =
  let w = GWindow.window ~title:"Scene" () in
  w#connect#destroy ~callback:(fun () -> Main.quit (); exit 0);
  let area = GlGtk.area [`RGBA;`DEPTH_SIZE 1]
      ~width:500 ~height:500 ~packing:w#add () in
  area#connect#realize ~callback:myinit;
  area#connect#reshape ~callback:my_reshape;
  area#connect#display ~callback:display;
  area#event#add [`BUTTON_PRESS];
  area#event#connect#button_press ~callback:
    begin fun ev ->
      let p = (GdkEvent.Button.x ev, GdkEvent.Button.y ev, 0.) in
      area#make_current ();
      let (x, y, z) = GluMat.unproject p in
      Printf.printf "x=%f, y=%f, z=%f\n" x y z;
      flush stdout;
      true
    end;
  w#show ();
  Main.main ()

let _ = Printexc.print main ()
</code>

Note that you should use GluMat.unproject, to get your coordinates
converted back.

Cheers,

        Jacques