Bug 318498 Many toolbars on top of one another
I don't know how to reproduce this. I'll attach a screenshot.
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/LazyStackRenderer.java
public void init(IEventBroker eventBroker) {
		
		
		eventBroker.unsubscribe(lazyLoader);
		eventBroker.subscribe(UIEvents.buildTopic(
				UIEvents.ElementContainer.TOPIC,
				UIEvents.ElementContainer.SELECTEDELEMENT), lazyLoader);
	}
	/**
	 * @param eventBroker
	 */
	public void contextDisposed(IEventBroker eventBroker) {
		eventBroker.unsubscribe(lazyLoader);
	}
	public void postProcess(MUIElement element) {
		if (!(element instanceof MGenericStack<?>))
			return;
		MGenericStack<MUIElement> stack = (MGenericStack<MUIElement>) element;
		MUIElement selPart = stack.getSelectedElement();
		if (selPart != null) {
			showTab(selPart);
		} else if (stack.getChildren().size() > 0) {
			
			for (MUIElement kid : stack.getChildren()) {
				if (kid.isToBeRendered() && kid.isVisible()) {
					stack.setSelectedElement(kid);
					break;
				}
			}
		}