Swing/IconScrollBar のバックアップ(No.7)

scrollPane.getVerticalScrollBar().setUI(new WindowsScrollBarUI() {
  @Override protected void paintThumb(Graphics g,
                            JComponent c, Rectangle thumbBounds) {
    super.paintThumb(g,c,thumbBounds);
    Graphics2D g2 = (Graphics2D) g;
    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
    Color oc = null;
    Color ic = null;
    JScrollBar sb = (JScrollBar)c;
    if (!sb.isEnabled() || thumbBounds.width>thumbBounds.height) {
      return;
    }else if(isDragging) {
      oc = SystemColor.activeCaption.darker();
      ic = SystemColor.inactiveCaptionText.darker();
    }else if(isThumbRollover()) {
      oc = SystemColor.activeCaption.brighter();
      ic = SystemColor.inactiveCaptionText.brighter();
    }else{
      oc = SystemColor.activeCaption;
      ic = SystemColor.inactiveCaptionText;
    }
    paintCircle(g2,thumbBounds,6,oc);
    paintCircle(g2,thumbBounds,10,ic);
  }
  private void paintCircle(Graphics2D g2, Rectangle thumbBounds,
                           int w, Color color) {
    g2.setPaint(color);
    int ww = thumbBounds.width-w;
    g2.fillOval(thumbBounds.x+w/2,
                thumbBounds.y+(thumbBounds.height-ww)/2,
                ww,ww);
  }
});