anchor.diff:            (y2 dimensions) (+ y1 line-height))))
   
   (defun end-line-cleaning-up (stream line line-x1 line-y1
  -                             line-width old-line-width
  -                             line-height old-line-height)
  +                             line-width line-height)
     "End the addition of strokes to `line' for now, and update the
   dimensions of `line'. Update all undisplayed lines to have no
   associated dimensions. Also clear from the bottom of strokes to
   the bottom of the line, and from the end of the line to the end
   of the sheet."
  -  (declare (ignore old-line-width))
     (end-line line line-x1 line-y1 line-width line-height)
     (with-accessors ((line-x1 x1) (line-y1 y1)
                      (line-x2 x2) (line-y2 y2)) (line-dimensions line)
  
positive.code: buffer offset `start-offset', and will be drawn starting
  at (`cursor-x', `cursor-y')."
    (let* ((line (line-information view (displayed-lines-count view)))
           (old-line-height (dimensions-height (line-dimensions line)))
           (old-line-width (dimensions-width (line-dimensions line)))
           (orig-x-offset cursor-x)
           (offset-change (- start-offset (line-start-offset line)))
           (line-spacing (stream-vertical-spacing pane)))
  
negative.code:          for stroke-dimensions = (stroke-dimensions stroke)
           do (draw-stroke pane view stroke (x1 stroke-dimensions) baseline)
           finally (progn (end-line-cleaning-up pane line orig-x-offset cursor-y
                                                line-width line-height)
                          (incf (displayed-lines-count view))
                          (return (values pump-state line-height)))))))
  
  