JSliderのトラック内部に目盛りを描画する

JSlider slider = new JSlider();
slider.setSnapToTicks(true);
slider.setMajorTickSpacing(10);
slider.addMouseMotionListener(new MouseAdapter() {
  @Override public void mouseDragged(MouseEvent e) {
    super.mouseDragged(e);
    e.getComponent().repaint();
  }
});

UIDefaults d = new UIDefaults();
d.put("Slider.thumbWidth", 24);
d.put("Slider.thumbHeight", 24);
Painter<JSlider> thumbPainter = (g, c, w, h) -> {
  g.setPaint(new Color(0x21_98_F6));
  g.fillOval(0, 0, w, h);
  NumberIcon icon = new NumberIcon(c.getValue());
  int xx = (w - icon.getIconWidth()) / 2;
  int yy = (h - icon.getIconHeight()) / 2;
  icon.paintIcon(c, g, xx, yy);
};
d.put("Slider:SliderThumb[Disabled].backgroundPainter", thumbPainter);
d.put("Slider:SliderThumb[Enabled].backgroundPainter", thumbPainter);
d.put("Slider:SliderThumb[Focused+MouseOver].backgroundPainter", thumbPainter);
d.put("Slider:SliderThumb[Focused+Pressed].backgroundPainter", thumbPainter);
d.put("Slider:SliderThumb[Focused].backgroundPainter", thumbPainter);
d.put("Slider:SliderThumb[MouseOver].backgroundPainter", thumbPainter);
d.put("Slider:SliderThumb[Pressed].backgroundPainter", thumbPainter);

d.put("Slider:SliderTrack[Enabled].backgroundPainter", new Painter<JSlider>() {
  @Override public void paint(Graphics2D g, JSlider c, int w, int h) {
    int arc = 10;
    int thumbSize = 24;
    int trackHeight = 8;
    int tickSize = 4;
    int trackWidth = w - thumbSize;
    int fillTop = (thumbSize - trackHeight) / 2;
    int fillLeft = thumbSize / 2;

    g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    g.setColor(new Color(0xC6_E4_FC));
    g.fillRoundRect(fillLeft, fillTop + 2, trackWidth, trackHeight - 4, arc, arc);

    // Paint track
    g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    g.setColor(new Color(0xC6_E4_FC));
    g.fillRoundRect(fillLeft, fillTop + 2, trackWidth, trackHeight - 4, arc, arc);

    int fillBottom = fillTop + trackHeight;
    Rectangle r = new Rectangle(fillLeft, fillTop, trackWidth, fillBottom - fillTop);

    // Paint the major tick marks on the track
    g.setColor(new Color(0x31_A8_F8));
    int value = c.getMinimum();
    while (value <= c.getMaximum()) {
      int xpt = getXPositionForValue(c, r, value);
      g.fillOval(xpt, (int) r.getCenterY() - tickSize / 2, tickSize, tickSize);
      // Overflow checking
      if (Integer.MAX_VALUE - c.getMajorTickSpacing() < value) {
        break;
      }
      value += c.getMajorTickSpacing();
    }

    // JSlider.isFilled
    int fillRight = getXPositionForValue(c, r, c.getValue());
    g.setColor(new Color(0x21_98_F6));
    g.fillRoundRect(fillLeft, fillTop, fillRight - fillLeft, fillBottom - fillTop, arc, arc);
  }

  // @see javax/swing/plaf/basic/BasicSliderUI#xPositionForValue(int value)
  private int getXPositionForValue(JSlider slider, Rectangle trackRect, float value) {
    float min = slider.getMinimum();
    float max = slider.getMaximum();
    float pixelsPerValue = trackRect.width / (max - min);
    int trackLeft = trackRect.x;
    int trackRight = trackRect.x + trackRect.width - 1;
    int pos = trackLeft + Math.round(pixelsPerValue * (value - min));
    return Math.max(trackLeft, Math.min(trackRight, pos));
  }
});
slider.putClientProperty("Nimbus.Overrides", d);