anchor.diff:    (location pointer))
   
   (defmethod allocate-foreign ((region region) &key rectangle polygon fill-rule)
  -  (declare (ignore initargs))
     (cond
      ((and rectangle polygon) 
       (error "Only one of the keyword arguments :RECTANGLE and :POLYGON can be specified"))
  
positive.code:   (etypecase region 
      (region region)
      ((or rectangle vector) 
       (make-instance 'region :rectangle (ensure-rectangle region)))))
  
  (defbinding region-get-clipbox (region &optional (rectangle (make-instance 'rectangle))) nil
    (region region)
  
negative.code:   
    (defun window-input-shape-combine (window shape x y)
      (etypecase shape
        (null (%window-input-shape-combine-region window nil 0 0))
        (region (%window-input-shape-combine-region window shape x y))
        (bitmap (%window-input-shape-combine-mask window shape x y))))
  
    (defbinding window-set-child-input-shapes () nil
      (window window))
  