DocumentTabPage(TabHost _host, IDockContainer _container) : super(_host, _container)
{
  // If the container is a panel, extract the content element and set it as the tab's content
  if (container.containerType == "panel") {
    panel = container;
    containerElement = panel.elementContent;
    
    // detach the container element from the panel's frame.  
    // It will be reattached when this tab page is destroyed
    // This enables the panel's frame (title bar etc) to be hidden
    // inside the tab page
    containerElement.remove();
  }
}

void destroy() {
  super.destroy();

  // Restore the panel content element back into the panel frame
  panel.elementContentHost.nodes.add(containerElement);
}