Swing/TitledSeparator のバックアップ(No.8)

class TitledSeparator extends JLabel{
  private Color color;
  private final String title;
  private final Color target;
  private final int height;
  private final int titlePosition;
  public TitledSeparator(String title, int height, int titlePosition) {
    this(title, null, height, titlePosition);
  }
  public TitledSeparator(String _title, Color _target, int _height, int _titlePosition) {
    super();
    this.title = _title;
    this.target = _target;
    this.height = _height;
    this.titlePosition = _titlePosition;
    Icon icon = new Icon() {
      private int width = -1;
      private Paint painter1, painter2;
      @Override public void paintIcon(Component c, Graphics g, int x, int y) {
        int w = c.getWidth();
        if(w!=width || painter1==null || painter2==null || color==null) {
          width = w;
          Point2D start = new Point2D.Float(0f, 0f);
          Point2D end   = new Point2D.Float((float)width, 0f);
          float[] dist  = {0.0f, 1.0f};
          color = getBackground();
          color = color==null ? UIManager.getColor("Panel.background") : color;
          Color tc = target==null ? color : target;
          painter1 = new LinearGradientPaint(start, end, dist, new Color[] {tc.darker(),   color});
          painter2 = new LinearGradientPaint(start, end, dist, new Color[] {tc.brighter(), color});
        }
        int h = getIconHeight()/2;
        Graphics2D g2  = (Graphics2D)g.create();
        g2.setPaint(painter1);
        g2.fillRect(x, y,   width, getIconHeight());
        g2.setPaint(painter2);
        g2.fillRect(x, y+h, width, getIconHeight()-h);
        g2.dispose();
      }
      @Override public int getIconWidth()  { return 200; } //dummy width
      @Override public int getIconHeight() { return height; }
    };
    this.setBorder(BorderFactory.createTitledBorder(
      BorderFactory.createMatteBorder(height, 0, 0, 0, icon), title,
      TitledBorder.DEFAULT_JUSTIFICATION, titlePosition));
    //System.out.println(getInsets());
  }
  @Override public Dimension getMaximumSize() {
    Dimension d = super.getPreferredSize();
    d.width = Short.MAX_VALUE;
    return d;
  }
  @Override public void updateUI() {
    super.updateUI();
    color = null;
  }
}