Re: Ada OpenGL question

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

On Sep 15, 7:18 pm, Olivier Scalbert <olivier.scalb...@algosyn.com>
wrote:
> Hi all,
>
> I have found some OpenGL code there:http://adaopengl.sourceforge.net/downloads.php
>
> I manage to get it compiled on my linux box but when I run it, I have:
>
> raised SYSTEM.ASSERTIONS.ASSERT_FAILURE : Handlers for "expose_event" on
> a GtkGLArea should be functions
>
> So it looks I have problem with callbacks somewhere around:
> Destroy_CB.Connect(MyGL, "destroy", Destroy_CB.To_Marshaller( Quit'Access));
>
> Expose_CB.Connect(MyGL, "expose_event", Expose_CB.To_Marshaller(
> Expose'Access));
>
> Resize_CB.Connect(MyGL, "configure_event", Resize_CB.To_Marshaller(
> Reshape'Access));
>
> All the files are located there:http://scalbert.dyndns.org/ada/adagtkgl/
>
> If somebody can help me, I would appreciate !
>
> Thanks,
>
> Olivier

In your example, Expose'Access presumably designates a procedure.
This is wrong.  Expose should be a function returning Boolean.  The
return value means:

False: pass the signal to any other signal handlers attached to it
True: abort processing of the signal.

The same holds for delete_event and a few other signals as documented
in the GTK+ reference at http://www.gtk.org.

The GtkAda signal handler infrastructure makes it impossible to detect
the type mismatch at compile time, so it has run-time checks instead.
This is the source of the error message.

HTH

--
Ludovic Brenta.