docs: protected JTree createTree() {
      JTree tree = new JTree(model);
      tree.setName("TreePopup.tree");
      tree.setFont(getFont());
      tree.setForeground(getForeground());
      tree.setBackground(getBackground());
      tree.setBorder(null);
      tree.setFocusable(true);
      tree.addMouseListener(handler);
      tree.addKeyListener(handler);
      tree.setCellRenderer(new Renderer());
      return tree;
    }