Getting local offset of GnomeCanvasItem to GnomeCanvasGroup

[Kang Jeong-Hee <Keizi mail co kr>]

All the GnomeCanvasItems are owned by a GnomeCanvasGroup.
When reparenting such item among groups, the local coord
preserved to be same offset to new parent.

GtkContainer that is similar to GnomeCanvasGroup provide
an API gtk_container_child_get() for getting x and y offset
of a child to the container.

An API of gnome_canvas_item_get_offset() or such a name
will be useful if done. Or is there already done with
another name?

Regard,
kz.