anchor.diff:  (defun make-merged-medium (sheet ink clip transform line-style text-style)
     (let ((medium (make-medium (port sheet) sheet)))
       (setf (medium-ink medium) ink)
  +    ;; First set transformation, then clipping region!
  +    (setf (medium-transformation medium) transform)
       (setf (medium-clipping-region medium) clip)
  -    (setf (medium-transformation medium) transform)
       (setf (medium-line-style medium) line-style)
       (setf (medium-text-style medium) text-style)
       medium))
  
positive.code: 	       (setf (sheet-medium stream) ,old-medium))))))))
  
  (def-grecording draw-point (point-x point-y)
    (values point-x point-y point-x point-y))
  
  (def-grecording draw-points (coord-seq)
    (loop for (x y) on coord-seq by #'cddr
  	minimize x into min-x
  	minimize y into min-y
  	maximize x into max-x
  	maximize y into max-y
  	finally (return (values min-x min-y max-x max-y))))
  
  (def-grecording draw-line (point-x1 point-y1 point-x2 point-y2)
    (values (min point-x1 point-x2) (min point-y1 point-y2)
            (max point-x1 point-x2) (max point-y1 point-y2)))
  
  (def-grecording draw-lines (coord-seq)
    (loop for (x y) on coord-seq by #'cddr
  	minimize x into min-x
  	minimize y into min-y
  	maximize x into max-x
  	maximize y into max-y
  	finally (return (values min-x min-y max-x max-y))))
  
  (def-grecording draw-polygon (coord-seq closed filled)
    (loop for (x y) on coord-seq by #'cddr
  	minimize x into min-x
  	minimize y into min-y
  	maximize x into max-x
  	maximize y into max-y
  	finally (return (values min-x min-y max-x max-y))))
  
  (def-grecording draw-rectangle (left top right bottom filled)
    (values (min left right) (min top bottom) (max left right) (max top bottom)))
  
  (def-grecording draw-ellipse (center-x center-y
  			      radius-1-dx radius-1-dy radius-2-dx radius-2-dy
  			      start-angle end-angle filled)
    (let ((radius-dx (abs (+ radius-1-dx radius-2-dx)))
          (radius-dy (abs (+ radius-1-dy radius-2-dy))))
      (values (- center-x radius-dx) (- center-y radius-dy)
  
negative.code: 
  (def-grecording draw-text (string point-x point-y start end
  			   align-x align-y toward-x toward-y transform-glyphs)
    ;; XXX transformation!!!
   (let* ((width (stream-string-width stream string
                                      :start start :end end
                                      :text-style text-style))
  