anchor.diff:  (defmethod replay-output-record ((record compound-output-record) stream
   				 &optional region (x-offset 0) (y-offset 0))
     (when (null region)
  -    (setq region +everywhere+))
  -  (map-over-output-records-overlapping-region
  -   #'replay-output-record record region x-offset y-offset
  -   stream region x-offset y-offset))
  +    (let ((viewport (pane-viewport stream)))
  +      (cond ((not (null viewport))
  +             (setf region (untransform-region (sheet-delta-transformation stream viewport)
  +                                            (pane-viewport-region stream))))
  +            (t
  +             (setq region +everywhere+)))))
  +  (with-drawing-options (stream :clipping-region region)
  +    (map-over-output-records-overlapping-region
  +     #'replay-output-record record region x-offset y-offset
  +     stream region x-offset y-offset)))
   
   (defmethod output-record-hit-detection-rectangle* ((record output-record))
     ;; XXX DC
  
positive.code: 				     clip-region))))))
  
  (defmethod set-medium-graphics-state :after ((state gs-clip-mixin) medium)
    (setf (medium-clipping-region medium) (graphics-state-clip state)))
  
  (defmethod match-output-records-1 and ((record gs-clip-mixin)
  
negative.code: 	(loop for i from 0 below (length coords) by 2
  	      do (progn
  		   (incf (aref coords i) dx)
  		   (incf (aref coords (1+ i)) dy)))))))
  
  (defmethod match-output-records-1 and ((record coord-seq-mixin)
  				       &key (coord-seq nil coord-seq-p))
  