+ /* First add new ones, then remove old ones.
+ * We cannot allow the group to become temporarily empty, because
+ * Session::route_removed_from_route_group() will delete empty groups.
+ */
+ for (RouteList::const_iterator i = routes.begin(); i != routes.end(); ++i) {
+ /* RouteGroup::add () ignores routes already present in the set */
+ _dragging->group->add (*i);
+ }
+ for (RouteList::const_iterator i = r->begin(); i != r->end(); ++i) {