/**
   * Paint a background for all groups and a round blue border and background when a cell is
   * selected.
   *
   * @param g2 the <tt>Graphics2D</tt> object through which we paint
   */
  private void internalPaintComponent(Graphics2D g2) {
    Color borderColor = Color.GRAY;

    if (isSelected) {
      g2.setPaint(
          new GradientPaint(
              0, 0, Constants.SELECTED_COLOR, 0, getHeight(), Constants.SELECTED_GRADIENT_COLOR));

      borderColor = Constants.SELECTED_COLOR;
    } else if (treeNode instanceof GroupNode) {
      g2.setPaint(
          new GradientPaint(
              0,
              0,
              Constants.CONTACT_LIST_GROUP_BG_GRADIENT_COLOR,
              0,
              getHeight(),
              Constants.CONTACT_LIST_GROUP_BG_COLOR));

      borderColor = Constants.CONTACT_LIST_GROUP_BG_COLOR;
    }

    g2.fillRect(0, 0, getWidth(), getHeight());
    g2.setColor(borderColor);
    g2.drawLine(0, 0, getWidth(), 0);
    g2.drawLine(0, getHeight() - 1, getWidth(), getHeight() - 1);
  }
  /**
   * Draw the icon at the specified location. Paints this component as an icon.
   *
   * @param c the component which can be used as observer
   * @param g the <tt>Graphics</tt> object used for painting
   * @param x the position on the X coordinate
   * @param y the position on the Y coordinate
   */
  public void paintIcon(Component c, Graphics g, int x, int y) {
    g = g.create();
    try {
      Graphics2D g2 = (Graphics2D) g;
      AntialiasingManager.activateAntialiasing(g2);

      g2.setColor(Color.WHITE);
      g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.8f));
      g2.fillRoundRect(x, y, getIconWidth() - 1, getIconHeight() - 1, 10, 10);
      g2.setColor(Color.DARK_GRAY);
      g2.drawRoundRect(x, y, getIconWidth() - 1, getIconHeight() - 1, 10, 10);

      // Indent component content from the border.
      g2.translate(x + 5, y + 5);

      super.paint(g2);

      g2.translate(x, y);
    } finally {
      g.dispose();
    }
  }