Overriding iface implementations

[Federico Mena Quintero <federico ximian com>]

Hi,

Say I have an instantiated object which I know supports a certain
interface.  I'd like to override the object's implementation of one of
that interface's methods.  Is this possible?

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.

Any ideas on how to do this?

Thanks,

  Federico