anchor.diff:    vtop-linum
     vtop-charpos
     point-marker
  -  wrap-ylist
     redraw-flag
     delete-hook
     parameters)
  
positive.code:         (cury (window-cursor-y-not-wrapping window))
          (refresh-line
           (get-window-refresh-line-function window)))
      (setf (window-wrap-ylist window) nil)
      (loop
        :with y := 0
        :for str :across (buffer-display-lines
  
negative.code:             (t
               (return)))
        (incf y))
      (charms/ll:wmove (window-win window)
                       cury
                       curx)))
  