Ada OpenGL question

Ada OpenGL question

[Olivier Scalbert]

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

Re: Ada OpenGL question

[Ludovic Brenta]

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.

Re: Ada OpenGL question

[Olivier Scalbert]

Ludovic Brenta wrote:

> 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.

Thanks for your help Ludovic!

I do not know how to solve it.
I have tried to change the Expose procedure into a function returning a 
Boolean, but then it does not compile anymore:

gtkgl.adb:89:66: no candidate interpretations match the actuals:
gtkgl.adb:89:87: expected type "Handler" defined at 
gtk-marshallers.ads:355, instance at gtk-handlers.ads:915, instance at 
line 68
gtkgl.adb:89:87: found type access to function "Expose" defined at line 89
gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at 
gtk-handlers.ads:939, instance at line 68
gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at 
gtk-handlers.ads:934, instance at line 68
gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at 
gtk-handlers.ads:930, instance at line 68
gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at 
gtk-handlers.ads:926, instance at line 68
gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at 
gtk-handlers.ads:922, instance at line 68
gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at 
gtk-handlers.ads:918, instance at line 68

Olivier

Re: Ada OpenGL question

[Ludovic Brenta]

Olivier Scalbert wrote:
> Ludovic Brenta wrote:
>> 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 athttp://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
>
> Thanks for your help Ludovic!
>
> I do not know how to solve it.
> I have tried to change the Expose procedure into a function returning a
> Boolean, but then it does not compile anymore:
>
> gtkgl.adb:89:66: no candidate interpretations match the actuals:
> gtkgl.adb:89:87: expected type "Handler" defined at
> gtk-marshallers.ads:355, instance at gtk-handlers.ads:915, instance at
> line 68
> gtkgl.adb:89:87: found type access to function "Expose" defined at line 89
> gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at
> gtk-handlers.ads:939, instance at line 68
> gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at
> gtk-handlers.ads:934, instance at line 68
> gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at
> gtk-handlers.ads:930, instance at line 68
> gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at
> gtk-handlers.ads:926, instance at line 68
> gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at
> gtk-handlers.ads:922, instance at line 68
> gtkgl.adb:89:87:   ==> in call to "To_Marshaller" at
> gtk-handlers.ads:918, instance at line 68

You must call GtkAda.Handlers.Return_Callback.Connect as opposed to
GtkAda.Handlers.Widget_Callback.Connect. (If you use some other
instances of Gtk.Handlers, the same holds: Return_Callback instead of
Callback).

--
Ludovic Brenta.

Re: Ada OpenGL question

[Olivier Scalbert]

Ludovic Brenta wrote:
> You must call GtkAda.Handlers.Return_Callback.Connect as opposed to
> GtkAda.Handlers.Widget_Callback.Connect. (If you use some other
> instances of Gtk.Handlers, the same holds: Return_Callback instead of
> Callback).
> 
> --
> Ludovic Brenta.

Thanks Ludovic, it works now !

Olivier