function insert_child_after(Frame $new_child, Frame $ref, $update_node = true)
 {
     while ($new_child instanceof Frame_Decorator) {
         $new_child = $new_child->_frame;
     }
     while ($ref instanceof Frame_Decorator) {
         $ref = $ref->_frame;
     }
     $this->_frame->insert_child_after($new_child, $ref, $update_node);
 }