JProgressBarの進捗状況を円形で表示する

class ProgressCircleUI extends BasicProgressBarUI {
  @Override public Dimension getPreferredSize(JComponent c) {
    Dimension d = super.getPreferredSize(c);
    int v = Math.max(d.width, d.height);
    d.setSize(v, v);
    return d;
  }

  @Override public void paint(Graphics g, JComponent c) {
    Rectangle rect = SwingUtilities.calculateInnerArea(progressBar, null);
    if (rect.isEmpty()) {
      return;
    }

    Graphics2D g2 = (Graphics2D) g.create();
    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                        RenderingHints.VALUE_ANTIALIAS_ON);

    Object o = progressBar.getClientProperty("Slider.clockwise");
    int dir = Objects.equals(o, Boolean.TRUE) ? -1 : 1;
    double start = 90d;
    double degree = dir * 360d * progressBar.getPercentComplete();
    double sz = Math.min(rect.width, rect.height);
    double cx = rect.getCenterX();
    double cy = rect.getCenterY();
    double or = sz * .5;
    double ir = or * .5; // .8;
    Shape inner = new Ellipse2D.Double(cx - ir, cy - ir, ir * 2d, ir * 2d);
    Shape outer = new Ellipse2D.Double(cx - or, cy - or, sz, sz);
    Shape sector = new Arc2D.Double(cx - or, cy - or, sz, sz, start, degree, Arc2D.PIE);

    Area foreground = new Area(sector);
    Area background = new Area(outer);
    Area hole = new Area(inner);

    foreground.subtract(hole);
    background.subtract(hole);

    // Draw the track
    g2.setPaint(new Color(0xDD_DD_DD));
    g2.fill(background);

    // Draw the circular sector
    g2.setPaint(progressBar.getForeground());
    g2.fill(foreground);
    g2.dispose();

    // Deal with possible text painting
    if (progressBar.isStringPainted()) {
      Insets ins = progressBar.getInsets();
      paintString(g, rect.x, rect.y, rect.width, rect.height, 0, ins);
    }
  }
}