'Corners of rectangle from lower left, moving clockwise.'

@property
def corners(self):

    (x0, y0, width, height) = self._rect_bbox
    xc = (x0, (x0 + width), (x0 + width), x0)
    yc = (y0, y0, (y0 + height), (y0 + height))
    return (xc, yc)
