Components not visible

I am learning CSS and Vaadin at the same time… but I am slowly going crazy with this one.

I took the Dashboard example from Vaadin and I am trying to alter it to create a header bar at the top containing a logo icon, logoff menu, etc. I think the code is pretty straightforward:

private HorizontalLayout buildHeaderBar() {
		HorizontalLayout header = new HorizontalLayout();
//		header.setStyleName("sidebar");
//		header.addStyleName("branding");
		// Logo
		Label logo = new Label("Dashboard", ContentMode.HTML);
		logo.setIcon(new ThemeResource("img/logo.png"));
		// Feedback Button
		Button feedback = new Button ("Feedback");
		Button settings = new Button("Settings");
		Button logout = new Button("Logout");
		return header;

This HorizontalLayout is then added to a VerticalLayout which is added to the original CssLayout. Everything else i mn the dashboard appears to be rendered correctly, but my labels and buttons are hidden. I can see from Chrome’s inspector that they are indeed there in the code (attached), but I can’t figure out why they are hidden. There is no css property telling them to be hidden that I can see.

I’d be very grateful if someone could point me in the right direction and let me know why these are not rendered.

ahhh - I think it was a z-order thing