Re: [gtk-list] Re: Callback function troubles

[Brandon Long <blong fiction net>]

On 09/25/98 Greg Kaup uttered the following other thing:
> Brent Briggs wrote:
> > 
> > I have been working on a robotics program and have never been able to
> > get my widgets to call my functions the way that I want them to.
> > I have a callback function that looks like this:
> > 
> > void init_arm_callback(GtkWidget *widget, GdkEvent *event,
> > command_struct *data)
> > {
> >   cout << "data in init_arm_callback :\n";
> >   cout << "data->fdesrcipter " << data->fdescripter << "\n";
> >   arm_initialize(data);
> > }
> > 
> ...
> > I am calling this callback with a button like so:
> > 
> >   /*setup the initialize button */
> >   button = gtk_button_new_with_label ("Re-Initialize");
> >   gtk_container_add (GTK_CONTAINER (control_vbox), button);
> >   gtk_widget_show (button);
> >   gtk_signal_connect (GTK_OBJECT (button), "clicked",
> >         GTK_SIGNAL_FUNC (init_arm_callback),
> >         &command_data);
> > 
> > The values in the structure seem to get changed when the data is passed
> > fron gtk_signal_connect (......) to init_arm_callback(........). For
> > instance, command_data.fdescripter has a value of 3 when checked from
> > main  but when the same value is checked from
> > init_arm_callback(........) I get a value of something like 607312 . Why
> > is this happening? This doesn't make sense to me but then again I am a
> > newbie to GTK developement. Can someone Please help me out?
> > 
> 
> I've been having the same type of problems...  PLEASE try your callback
> WITHOUT the GdkEvent *event arg... i.e.
>   void init_arm_callback(GtkWidget *widget, (gpointer)data)
>   {
>    command_struct *ptr = (command_struct*)data;
>    then... use the ptr! 
>   }
> 
> I've been getting the "data" in the second arg...  I'm still trying to
> figure out if it is g++ 2.7.2.3, the cvs version of gtk+ or some silly
> thing I'm doing wrong!  If you are having the same problem, maybe we
> can narrow it down.

You are using C++?

Left field guess, you might need to wrap your function header with:
#ifdef __cplusplus
extern "C" {
#pragma }
#endif /* __cplusplus */

#ifdef __cplusplus
}
#endif /* __cplusplus */

maybe.

Brandon
-- 
 Brandon Long                
 MD6 Crash Test Dummy           "Mithras -- the Reason for the Season"
 Intel Corporation       
          I'm too low on the totem pole to speak for Intel.
		  http://www.fiction.net/blong/