Bug 304211 StackRenderer does not set eagerly created controls to the item
Right-clicking on a Java element and then using 'Open Declaration' opens an editor on the specified file but its content is not shown. Switching tabs or selecting items in the 'Outline' view does _not_ help. Seems to be calling IWorkbenchPage's APIs properly. No idea yet as to what's going on over here.
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/workbench/ui/renderers/swt/StackRenderer.java
ctf.setUnselectedCloseVisible(false);
		newWidget = ctf;
		final IEclipseContext folderContext = getContext(element);
		folderContext.set(FOLDER_DISPOSED, Boolean.FALSE);
		final IEclipseContext toplevelContext = getToplevelContext(element);
		final Trackable updateActiveTab = new Trackable(folderContext) {
			public boolean notify(ContextChangeEvent event) {
				if (event.getEventType() == ContextChangeEvent.DISPOSE)
					return false;
				if (!participating) {
					return true;
				}
				trackingContext.get(FOLDER_DISPOSED);
				IEclipseContext currentActive = toplevelContext;
				IEclipseContext child;
				while (currentActive != trackingContext
						&& (child = (IEclipseContext) currentActive
								.get("activeChild")) != null && child != currentActive) { 
					currentActive = child;
				}
				
				String cssClassName = (currentActive == trackingContext) ? "active" 
						: "inactive"; 
				stylingEngine.setClassname(ctf, cssClassName);
				
				
				if (ctf.getTopRight() != null)
					stylingEngine.setClassname(ctf.getTopRight(), cssClassName);