@Override
  public void writeExternal(Element element) {
    JdomKt.addOptionTag(element, ATTR_SHOW_DEFAULT, Boolean.toString(isShowDefault()), "setting");
    JdomKt.addOptionTag(element, ATTR_CELL_SIZE, Integer.toString(cellSize), "setting");
    JDOMExternalizerEx.write(element, ATTR_WHITE_COLOR, whiteColor);
    JDOMExternalizerEx.write(element, ATTR_BLACK_COLOR, blackColor);
  }
@Override
  public void writeExternal(Element element)