gboolean row_drop_possible ( GtkTreeDragDest* drag_dest, GtkTreePath* dest_path, const GValue* value )
Determines whether a drop is possible before the given
at the same depth as
dest_path. i.e., can we drop the data in
value at that location.
dest_path does not have to
exist; the return value will almost certainly be
FALSE if the
dest_path doesn’t exist, though.