anchor.diff:                                           0
                                            (round x1))
                                   0)))
  -          (when (> y2 (+ y-position viewport-height))
  +          (when (and (> y2 (+ y-position viewport-height))
  +                     (not (end-of-buffer-p (bot view))))
               (full-redisplay pane)
               ;; We start all over!
               (display-drei-pane (pane-frame pane) pane)))))))
  
positive.code: anything. Will use the function specified in the drawing-options
  of `stroke' to carry out the actual calculations."
    (unless (and (= cursor-x (x1 (stroke-dimensions stroke)))
                 (not (stroke-dirty stroke)))
      (invalidate-stroke stroke :modified t))
    (when (stroke-dirty stroke)
      (funcall (drawing-options-function (stroke-drawing-options stroke)) stream view stroke
  
negative.code:          for stroke = (aref (line-strokes line) stroke-index)
           for stroke-dimensions = (stroke-dimensions stroke)
           do (draw-stroke pane view stroke (x1 stroke-dimensions) baseline)
           finally (progn (end-line-cleaning-up view line orig-x-offset cursor-y
                                                line-width line-height)
                          (incf (displayed-lines-count view))
                          (return (values pump-state line-height)))))))
  