The following generic functions comprise the region predicate protocol. All classes that are subclasses of region must either inherit or implement methods for these generic functions.
The methods for region-equal , region-contains-region-p , and region-intersects-region-p will typically specialize both the region1 and region2 arguments.
region-equal [Generic Function]
Summary: Returns t if the two regions region1 and region2 contain exactly the same set of points; otherwise, it returns nil .
region-contains-region-p [Generic Function]
Summary: Returns t if all points in the region region2 are members of the region region1 ; otherwise, it returns nil .
region-contains-position-p [Generic Function]
Summary: Returns t if the point at ( x, y ) is contained in the region region ; otherwise, it returns nil . Since regions in CLIM are closed, this must return t if the point at (x, y) is on the region's boundary.
region-contains-position-p is a special case of region-contains-region-p in which the region is the point ( x, y ).
region-intersects-region-p [Generic Function]
Summary: Returns nil if region-intersection of the two regions region1 and region2 would be +nowhere+ ; otherwise, it returns t .
Common Lisp Interface Manager 2.0 User's Guide - 7 Aug 2017