'Return the cluster height at the point in widget local coordinates.'

def height_at(self, point):

    if (not self._root):
        return 0
    (tinv, ok) = self._transform.inverted()
    if (not ok):
        return 0
    tpoint = tinv.map(point)
    if (self.orientation in [self.Left, self.Right]):
        height = tpoint.x()
    else:
        height = tpoint.y()
    if (self.orientation in [self.Left, self.Bottom]):
        base = self._root.value.height
        height = (base - height)
    return height
