Swing/HoverCloseButton のバックアップ(No.4)

public MyJTabbedPane() {
  super();
  setTabLayoutPolicy(JTabbedPane.SCROLL_TAB_LAYOUT);
  addMouseMotionListener(new MouseMotionAdapter() {
    private int prev = -1;
    @Override public void mouseMoved(MouseEvent e) {
      JTabbedPane source = (JTabbedPane) e.getSource();
      int focussed = source.indexAtLocation(e.getX(), e.getY());
      if(focussed == prev) return;
      for(int i = 0; i < source.getTabCount(); i++) {
        TabPanel tab = (TabPanel) source.getTabComponentAt(i);
        tab.setButtonVisible(i == focussed);
      }
      prev = focussed;
    }
  });
}