Re: [gtk-list] Re: C++ and Gtk

[Brian Stempel <stempel oneimage com>]

> > only real minus (which IMHO isn't really that big of a deal) is the small
> > amount of casting to get from a generic callback pointer to, say, your
> > object instance.  To be honest, I haven't done that much with gtk, but I
> > have done
> Could you give an example of how you might actually go about doing this?
> I've got a lot of C++ code that I want to keep and I'd also like to keep
> using the straight gtk+ API.

So, for instance, the code might look like:

class MyObject
{

     // Class declarations...

     void myMethod      ();
     void myOtherMethod ();

     static void signalHandler(GtkWidget *widget, MyObject *data);

}

void MyObject::myMethod()
{

     gtk_signal_connect(GTK_OBJECT(someWidget), "someSignal",
                        GTK_SIGNAL_FUNC(signalHandler), this);

}

void MyObject::signalHandler(GtkWidget *, MyObject *data)
{

     MyObject &myObject = *data;

     myObject.myOtherMethod();

}

The idea is that you receive the signal data as a pointer-to-instance,
and then make a reference from that.  You could just as easily receive
the data as a pointer-to-instance, and then just use the -> operator,
rather than the . operator, but I prefer the above syntax, and I *believe*
it's slightly more efficient that way.

BTW, the code above is derived from the method using Motif, and not tested,
so hopefully I didn't make any silly mistakes.

						Brian