/**
     * Paint a background for all groups and a round blue border and background when a cell is
     * selected.
     *
     * @param g the <tt>Graphics</tt> object
     */
    private void internalPaintComponent(Graphics g) {
      AntialiasingManager.activateAntialiasing(g);

      Graphics2D g2 = (Graphics2D) g;

      if (isSelected) {
        g2.setColor(selectedColor);
        g2.fillRect(0, 0, this.getWidth(), this.getHeight());
      }
    }
  /**
   * Paints a custom gradient background for selected cells.
   *
   * @param g the <tt>Graphics</tt> object used for painting
   */
  private void internalPaintComponent(Graphics g) {
    AntialiasingManager.activateAntialiasing(g);

    Graphics2D g2 = (Graphics2D) g;
    int width = getWidth();
    int height = getHeight();

    if (this.isSelected) {
      GradientPaint p =
          new GradientPaint(
              width / 2, 0, SELECTED_START_COLOR, width / 2, height, SELECTED_END_COLOR);

      g2.setPaint(p);
      g2.fillRoundRect(1, 1, width, height - 1, 7, 7);
    }

    g2.setColor(SELECTED_START_COLOR);
    g2.drawLine(0, height - 1, width, height - 1);
  }