Re: Overriding iface implementations

On Wed, 25 Feb 2004, Federico Mena Quintero wrote:

> On Wed, 2004-02-25 at 09:03, Owen Taylor wrote:
> > > Namely, the file chooser uses a GtkListStore for the shortcuts list.  I
> > > want to make just the bookmarks part reorderable, so I need to override
> > > ::row_draggable on the source side, and ::row_drop_possible on the
> > > destination side.
> > You just add the interface again and set the functions you want
> > and don't set the others. g_type_interface_peek_parent() can
> > be used to chain up.
> That means deriving from GtkListStore and re-adding the interfaces,
> right?
> My question is more along the following lines.  Can I override interface
> methods for a particular instance of a class?

no, not generically, i.e. we don't type per-instance and allow per instance
method changes. that would have made the type+object system too complicated.
there're other OO languages out there if you need that ;)

>  E.g.
> 	GtkTreeDragSourceIface my_methods = {
> 	  my_row_draggable_func,
> 	  NULL,
> 	  NULL
> 	};
> 	list = gtk_list_store_new ();
> 	override_interface (list, GTK_TYPE_TREE_DRAG_SOURCE, my_methods);

well, this example looks more like an ordinary signal connection (despite
override vs. connect). in general, you can only customize per-instance methods
if they are signals. if you need to do something like tweak a specific objects
behaviour and can't connect, that usually indicates there's a signal missing
(in the object/interface type providing the method).

>   Federico


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