[gtkmm] d'n'd source widget discovery

[Dariusz Marcinkiewicz <D Marcinkiewicz elka pw edu pl>]

	The documentation states:
(http://gtkmm.sourceforge.net/gtkmm2/docs/tutorial/html/ch15s04.html)
"The drag and drop signals provide a DragContext, which contains some
information about the drag and drop operation and can be used
to influence the process. For instance, you can discover the source
widget, or change the drag and drop icon, by using the set_icon()
methods."
So how I can do that?
There is nothing like: Gtk::Widget* Gdk::DragContext::source_discover()
(which I expected), gtk documentation says anything about it neither.


TIA

DM