anchor.diff:  
   (defmethod fully-redisplay-pane ((drei-pane drei-pane)
                                    (view point-mark-view))
  -  (reposition-pane drei-pane)
  -  (setf (full-redisplay-p view) nil))
  +  (reposition-pane drei-pane))
   
   (defmethod fully-redisplay-pane :after ((drei-pane drei-pane)
                                           (view drei-buffer-view))
  
positive.code:                                       (round (- cursor-x)))
                               0)))
            (when (> (+ cursor-y line-height) (+ y-position viewport-height))
              (next-line (top view))
              ;; We start all over!
              (display-drei-pane (pane-frame pane) pane)))))))
  
  
negative.code:   (setf (displayed-lines-count view) 0)
    (multiple-value-bind (cursor-x cursor-y) (stream-cursor-position pane)
      (with-output-recording-options (pane :record nil :draw t)
        (loop with start-offset = (offset (beginning-of-line (top view)))
           with pump-state = (pump-state-for-offset view start-offset)
           with pane-height = (bounding-rectangle-height (or (pane-viewport pane) pane))
           for line = (line-information view (displayed-lines-count view))
           do (multiple-value-bind (new-pump-state line-height)
                  (draw-line-strokes pane view pump-state start-offset cursor-x cursor-y)
  