docs: def _get_value(self):
          """
          Return two delegating variables. Each variable should contain
          a value attribute with the real value.
          """
          x, y = self._point.x, self._point.y
          self._px, self._py = self._item_point.canvas.get_matrix_i2i(self._item_point,
                                                                      self._item_target).transform_point(x, y)
          return self._px, self._py