cairo:region-contains-rectangle (region x y width height)

region -- a cairo:region-t instance
x -- an integer for the x coordinate of the left side of the rectangle
y -- an integer for the y coordinate of the top side of the rectangle
width -- an integer for the width of the rectangle
height -- an integer for the height of the rectangle

The cairo:region-overlap-t value.

Checks whether the given rectangle is inside, outside or partially contained in region. Returns the :in value if rectangle is entirely inside region, the :out value if rectangle is entirely outside region, or the :part value if rectangle is partially inside and partially outside region.