A graphics port.
invalidate-rectangle-from-points invalidates a rectangle (by calling invalidate-rectangle) specified by two points. The coordinates of one point are (
) and the other (
) The points do not have to be ordered.
The keyword arguments specify extending the rectangle: extend-x extends the rectangle in the x dimension in both directions, and extend-y extends the rectangle in the y dimension in both directions. Both extend-x and extend-y default to extend , which itself defaults to 0 (that is, no extension).
CAPI User Guide and Reference Manual (Unix version) - 25 Feb 2015