Re: Gtk widgets in gtkmm (Previously no subject)

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

Chris Vine wrote:

> On Thursday 21 July 2005 16:22, Andrew Krause wrote:
>  
>
> > (Sorry about the no subject topic... in any case...)
> >
> > I have a c++ class that contains Gtk+ widgets. They work perfectly
> > fine except for one thing. When I try to connect a signal to them,
> > they throw an error saying that the function that it is connected
> > to should be formatted: "void (*) ()" instead of: "void (MyClass) ()".
> >
> > How can I get around this? Is there a way without requiring all
> > of my functions to receive the class data and not be a part of
> > the class?
> >    
>
> g_signal_connect has its callback (slot) function passed as a C function 
> pointer (cast with G_CALLBACK()).
>
> The cludge (which will work with most but not all compilers) is to make your 
> callback a static member function of the class.  The correct (standards 
> complying) approach is to make the callback a function outside the class with 
> C linkage (ie declare it extern "C") and make it a friend of the class if it 
> needs access to the class's private or protected members.
>
> You will need to pass the class instance to the callback if the callback needs 
> to access non-static data of the class.  If so pass the "this" pointer as the 
> last (data) argument to g_signal_connect(), and then cast it back to the 
> correct type in the callback.
>  
I only would add one note:

you may wish to use "static" class method as callback for that signal, 
then you could save c++ style and avoid friend declarations.

Regards,
-andrew