JTableのセル選択背景描画をラウンド矩形に変更する

class RoundedCellSelectionTable extends JTable {
  protected RoundedCellSelectionTable(TableModel model) {
    super(model);
  }

  @Override public void updateUI() {
    super.updateUI();
    setOpaque(false);
    setFocusable(false);
    setCellSelectionEnabled(true);
    setShowGrid(false);
    setIntercellSpacing(new Dimension());
    setAutoCreateRowSorter(true);
    setBackground(new Color(0x0, true));
    setRowHeight(20);
    if (getUI() instanceof SynthTableUI) {
      setDefaultRenderer(
          Boolean.class, new SynthBooleanTableCellRenderer2());
    }
  }

  @Override public Component prepareRenderer(
        TableCellRenderer renderer, int row, int column) {
    Component c = super.prepareRenderer(renderer, row, column);
    if (c instanceof JComponent) {
      ((JComponent) c).setOpaque(false);
    }
    return c;
  }

  @Override public Component prepareEditor(
        TableCellEditor editor, int row, int column) {
    Component c = super.prepareEditor(editor, row, column);
    if (c instanceof JComponent) {
      ((JComponent) c).setOpaque(false);
    }
    return c;
  }

  @Override public void changeSelection(
        int rowIndex, int columnIndex,
        boolean toggle, boolean extend) {
    super.changeSelection(rowIndex, columnIndex, toggle, extend);
    repaint();
  }

  @Override protected void paintComponent(Graphics g) {
    if (getSelectedColumnCount() != 0 && getSelectedRowCount() != 0) {
      Graphics2D g2 = (Graphics2D) g.create();
      g2.setRenderingHint(
          RenderingHints.KEY_ANTIALIASING,
          RenderingHints.VALUE_ANTIALIAS_ON);
      g2.setPaint(getSelectionBackground());
      Area area = new Area();
      for (int row : getSelectedRows()) {
        for (int col : getSelectedColumns()) {
          addArea(area, row, col);
        }
      }
      // Arrays.stream(getSelectedRows())
      //     .boxed()
      //     .flatMap(row -> Arrays.stream(getSelectedColumns())
      //         .filter(col -> isCellSelected(row, col))
      //         .mapToObj(col -> getCellRect(row, col, true))
      //         .map(Area::new))
      //     .forEach(area::add);
      // if (!area.isEmpty()) {
      int arc = 8;
      for (Area a : GeomUtils.singularization(area)) {
        // List<Point2D> lst = GeomUtils.convertAreaToPoint2DList(a);
        // g2.fill(GeomUtils.convertRoundedPath(lst, arc / 2d));
        Rectangle r = a.getBounds();
        g2.fillRoundRect(r.x, r.y, r.width - 1, r.height - 1, arc, arc);
      }
      g2.dispose();
    }
    super.paintComponent(g);
  }

  private void addArea(Area area, int row, int col) {
    if (isCellSelected(row, col)) {
      area.add(new Area(getCellRect(row, col, true)));
    }
  }
}