cairo:surface-mark-dirty-rectangle (surface x y width height)

surface -- a cairo:surface-t instance
x -- an integerfor the x coordinate of dirty rectangle
y -- an integer for the y coordinate of dirty rectangle
width -- an integer for the width of dirty rectangle
height -- an integer for the height of dirty rectangle

Like the cairo:surface-mark-dirty function, but drawing has been done only to the specified rectangle, so that Cairo can retain cached contents for other parts of the surface. Any cached clip set on the surface will be reset by this function, to make sure that future Cairo calls have the clip set that they expect.