def fire_row_changed ix
      return if ix >= @list.length
      clear_row @pad, ix
      # allow documents to reparse that line
      fire_handler :ROW_CHANGED, ix
      _arr = _getarray
      render @pad, ix, _arr[ix]

    end
def fire_row_changed ix
      return if ix >= @list.length
      clear_row @pad, ix
      # allow documents to reparse that line
      fire_handler :ROW_CHANGED, ix
      _arr = _getarray
      render @pad, ix, _arr[ix]

    end
repaint only one row since content of that row has changed.
 No recreate of pad is done.