anchor.diff:                                                  (/ (+ x1 x2) 2) from
                                                   (/ (+ u1 u2) 2) to
                                                   arc-drawing-options))))))))
  -                            (map nil continuation children)))))
  +                            (map nil continuation children))))))
   
   (defmethod layout-graph-edges :around ((graph-output-record tree-graph-output-record)
                                          stream arc-drawer arc-drawing-options)
  
positive.code:                                 (let ((v (+ v0 (/ (min 0 d) -2))))
                                    (setf (output-record-position node)
                                          (if (eq orientation :vertical)
                                              (values v u0)
                                              (values u0 v)))
                                    (add-output-record node graph-output-record))
                                  ;;
                                  (let ((u (+ u0 (car majors)))
  
negative.code: (defmethod layout-graph-edges ((graph standard-graph-output-record)
                                 stream arc-drawer arc-drawing-options)
    (with-slots (orientation) graph
     ;; We tranformed the position of the nodes when we inserted them into
     ;; output history, so the bounding rectangles queried below will be
     ;; transformed. Therefore, disable the transformation now, otherwise
     ;; the transformation is effectively applied twice to the edges.
     (with-identity-transformation (stream)
      (traverse-graph-nodes graph
                            (lambda (node children continuation)
                              (unless (eq node graph)
  