Re: [gtkmm] Glib critical messages on Property<>

["Andrew E. Makeev" <andrew solvo ru>]

Daniel Elstner wrote:

> On Don, 2003-03-27 at 17:58, Murray Cumming Comneon com wrote:
>  
>
> > Glib::Property<> wraps existing properties. It doesn't add properties. You
> > would need to use the Glib API for that. If you want to be able to add
> > properties from C++ code then please submit a gtkmm 2.4 bug.
> >    
>
> Sorry, but that's not true :-)  The whole purpose of Glib::Property<> is
> to be able to install custom properties via C++ code.
>
>  
>
> > > (main.exe:10701): GLib-GObject-CRITICAL **: file gvalue.c: line 103
> > > (g_value_copy): assertion `g_value_type_compatible (G_VALUE_TYPE
> > > (src_value), G_VALUE_TYPE (dest_value))' failed
> > >
> > > Do I something wrong here? I searched in the docu and the 
> > > FAQs but I found
> > > nothing about my problem. Are there any restrictions for 
> > > Glib::Value<T*>?
> > >      
>
> I reckon the problem might be an add_attribute() call with incompatible
> types, and not directly caused by Glib::Property<> itself.  IIRC
> Glib::Property<> has been used with success for custom types before; try
> checking the list archives.
>  
Yes, problem caused by Glib::Value<T*> (GValue, actualy).

1. T* should be a pointer to class derived from GLib::Object.
2. You should ensure you did proper initialization of your class propery 
member in constructor.
3. And as Daniel said you have to watch you are using same T* pointers 
when handling property value (using add_attribute or directly).

I think, it is better to use Glib::Property<void *> to store a pointer 
to any custom class, casting functions gonna do dirk work for ya later. 
At least, in my "FAST" text cellrenderer I have no troubles with such 
things.

Regards,
-andrew