Re: Replacing GTypeInterface instances.

[murrayc t-online de (Murray Cumming)]

On Thu, 2001-11-01 at 23:51, Murray Cumming wrote:
> On Thu, 2001-11-01 at 23:28, Havoc Pennington wrote:
> > 
> > murrayc t-online de (Murray Cumming) writes: 
> > > *** Similar stuff needed for Interfaces:
> > > 
> > > We need to be able to replace the GTypeInterface-derived struct (e.g.
> > > GtkTreeModelIFace) that was registered in the implementing type (e.g. in
> > > gtk_tree_store_get_type()) with a derived GTypeInterface instance, or at
> > > least a different instance of the GTypeInterface struct.
> > > 
> > > We will still need to have access to a copy of the original
> > > GTypeInterface so that we can call the original functions if our C++
> > > hooks have not been used to override them.
> > > 
> > > I'm hoping that you can tell me how this might be done.
> > 
> > It's going to suck. Owen and I discussed it extensively. Unfortunately
> > we didn't write any of it down. ;-)
> > 
> > IIRC the best solution that was reasonably transparent to C++ users
> > involved dynamically generating proxy classes for C++ classes based on
> > RTTI on the C++ class.
> 
> It would be nice to know why this might be necessary. I think that I can
> see a way to do it just by replacing the vfunc table (the
> GTypeInterface-derived struct instance) with our own.
> 
>  i.e. you keep a hash from list of interfaces
> > implemented to proxy class, and you yank the right proxy out of your
> > hash on object construction. Or something.
> 
> Which would also require replacement of the GTypeInterface instance.
> That's what I need to know how to do.

Maybe I can do this with g_type_interface_peek(), which is used to
implement, for instance, GTK_TREE_MODEL_GET_IFACE(). I should be able to
read and replace the function pointers in that.

>  I never actually tried to
> > implement it...
> > 
> > You might be better off just requiring C++ users to put in some funky
> > boilerplate, instead of trying to do it magically.
> 
> I don't think that it will be possible to make a C++ class implement a
> C++/Glib interface just by inheritance. C++ coders will also need to
> call
> implements_interface(TreeModel::get_sometypething());
> in the constructors of their C++ interface-implementing classes.

-- 
Murray Cumming
murrayc usa net
www.murrayc.com