JTabbedPaneの各タブにJButtonを右寄せで追加する

class CloseableTabbedPaneLayerUI extends LayerUI<JTabbedPane> {
  private final JComponent rubberStamp = new JPanel();
  private final Point pt = new Point(-100, -100);
  private final JButton button = new JButton(new CloseTabIcon());

  public CloseableTabbedPaneLayerUI() {
    super();
    button.setBorder(BorderFactory.createEmptyBorder());
    button.setFocusPainted(false);
    button.setBorderPainted(false);
    button.setContentAreaFilled(false);
    button.setRolloverEnabled(false);
  }

  @Override public void paint(Graphics g, JComponent c) {
    super.paint(g, c);
    if (c instanceof JLayer) {
      JLayer jlayer = (JLayer) c;
      JTabbedPane tabPane = (JTabbedPane) jlayer.getView();
      for (int i = 0; i < tabPane.getTabCount(); i++) {
        Rectangle rect = tabPane.getBoundsAt(i);
        Dimension d = button.getPreferredSize();
        int x = rect.x + rect.width - d.width - 2;
        int y = rect.y + (rect.height - d.height) / 2;
        Rectangle r = new Rectangle(x, y, d.width, d.height);
        button.getModel().setRollover(r.contains(pt));
        SwingUtilities.paintComponent(g, button, rubberStamp, r);
      }
    }
  }

  @Override public void installUI(JComponent c) {
    super.installUI(c);
    if (c instanceof JLayer) {
      ((JLayer) c).setLayerEventMask(
          AWTEvent.MOUSE_EVENT_MASK |AWTEvent.MOUSE_MOTION_EVENT_MASK);
    }
  }

  @Override public void uninstallUI(JComponent c) {
    if (c instanceof JLayer) {
      ((JLayer) c).setLayerEventMask(0);
    }
    super.uninstallUI(c);
  }

  @Override protected void processMouseEvent(
      MouseEvent e, JLayer<? extends JTabbedPane> l) {
    if (e.getID() == MouseEvent.MOUSE_CLICKED) {
      pt.setLocation(e.getPoint());
      JTabbedPane tabbedPane = (JTabbedPane) l.getView();
      int index = tabbedPane.indexAtLocation(pt.x, pt.y);
      if (index >= 0) {
        Rectangle rect = tabbedPane.getBoundsAt(index);
        Dimension d = button.getPreferredSize();
        int x = rect.x + rect.width - d.width - 2;
        int y = rect.y + (rect.height - d.height) / 2;
        Rectangle r = new Rectangle(x, y, d.width, d.height);
        if (r.contains(pt)) {
          tabbedPane.removeTabAt(index);
        }
      }
    }
  }

  @Override protected void processMouseMotionEvent(
      MouseEvent e, JLayer<? extends JTabbedPane> l) {
    pt.setLocation(e.getPoint());
    JTabbedPane tabbedPane = (JTabbedPane) l.getView();
    int index = tabbedPane.indexAtLocation(pt.x, pt.y);
    if (index >= 0) {
      Point loc = e.getPoint();
      loc.translate(-16, -16);
      l.repaint(new Rectangle(loc, new Dimension(32, 32)));
    }
  }
}