From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Thread: a07f3367d7,efe941d6d79d0fa7
X-Google-Attributes: gida07f3367d7,public,usenet
X-Google-NewGroupId: yes
X-Google-Language: ENGLISH,ASCII
Path: 
 g2news2.google.com!postnews.google.com!k26g2000vbp.googlegroups.com!not-for-mail
From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: Ada OpenGL question
Date: Tue, 15 Sep 2009 11:19:42 -0700 (PDT)
Organization: http://groups.google.com
Message-ID: 
 <e6fcfe04-9ccb-4f37-be5a-ecf64bc2a35a@k26g2000vbp.googlegroups.com>
References: <4aafcc54$0$2860$ba620e4c@news.skynet.be>
NNTP-Posting-Host: 94.108.228.143
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
X-Trace: posting.google.com 1253038782 1403 127.0.0.1 (15 Sep 2009 18:19:42
 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Tue, 15 Sep 2009 18:19:42 +0000 (UTC)
Complaints-To: groups-abuse@google.com
Injection-Info: k26g2000vbp.googlegroups.com; posting-host=94.108.228.143;
	posting-account=pcLQNgkAAAD9TrXkhkIgiY6-MDtJjIlC
User-Agent: G2/1.0
X-HTTP-UserAgent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.0.11)
	Gecko/2009061208 Iceweasel/3.0.12 (Debian-3.0.12-1),gzip(gfe),gzip(gfe)
Xref: g2news2.google.com comp.lang.ada:8331
Date: 2009-09-15T11:19:42-07:00
List-Id: <comp.lang.ada>

On Sep 15, 7:18=A0pm, Olivier Scalbert <olivier.scalb...@algosyn.com>
wrote:
> Hi all,
>
> I have found some OpenGL code there:http://adaopengl.sourceforge.net/down=
loads.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.