JTableの行選択背景描画をラウンド矩形に変更する

class RoundSelectionRenderer extends DefaultTableCellRenderer {
  private static final double ARC = 6d;
  private Position pos;

  @Override public void paintComponent(Graphics g) {
    Graphics2D g2 = (Graphics2D) g.create();
    g2.setRenderingHint(
        RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    g2.setColor(getBackground().brighter());
    double w = getWidth() - 1d;
    double h = getHeight() - 1d;
    Area area = pos.getArea(w, h, ARC);
    g2.fill(area);
    if (isFocusable()) {
      g2.setColor(getBackground());
      g2.draw(area);
    }
    super.paintComponent(g);
    g2.dispose();
  }

  @Override public Component getTableCellRendererComponent(
      JTable table, Object value,
      boolean isSelected, boolean hasFocus,
      int row, int column) {
    Component c = super.getTableCellRendererComponent(
        table, value, isSelected, false, row, column);
    if (c instanceof JLabel) {
      JLabel l = (JLabel) c;
      l.setBorder(BorderFactory.createEmptyBorder(0, 5, 0, 5));
      l.setOpaque(false);
      pos = getPosition(table, column);
      boolean b = value instanceof Number;
      l.setHorizontalAlignment(b ? RIGHT : LEFT);
    }
    c.setFocusable(hasFocus
        || table.getSelectionModel().getLeadSelectionIndex() == row);
    return c;
  }

  private static Position getPosition(JTable table, int column) {
    boolean isFirst = column == 0;
    boolean isLast = column == table.getColumnCount() - 1;
    Position p;
    if (isFirst) {
      p = Position.FIRST;
    } else if (isLast) {
      p = Position.LAST;
    } else {
      p = Position.MIDDLE;
    }
    return p;
  }

  private enum Position {
    FIRST, MIDDLE, LAST;

    public Area getArea(double w, double h, double arc) {
      Area area = new Area();
      if (this == FIRST) {
        area.add(new Area(new Rectangle2D.Double(w - arc, 0d, arc + arc, h)));
        area.add(new Area(new RoundRectangle2D.Double(0d, 0d, w, h, arc, arc)));
      } else if (this == LAST) {
        area.add(new Area(new Rectangle2D.Double(-arc, 0d, arc + arc, h)));
        area.add(new Area(new RoundRectangle2D.Double(0d, 0d, w, h, arc, arc)));
      } else {
        area.add(new Area(new Rectangle2D.Double(-arc, 0d, w + arc + arc, h)));
      }
      return area;
    }
  }
}