XSetRegion(display, gc, r)
Display *display;
GC gc;
Region r;
XDestroyRegion(r)
Region r;
The XSetRegion function sets the clip-mask in the GC to the specified region. The region is specified relative to the drawable's origin. The resulting GC clip origin is implementation dependent. Once it is set in the GC, the region can be destroyed.
The XDestroyRegion function deallocates the storage associated with a specified region.