Bug 307747 EPartService doesn't render new parts
1. Have a part in a stack, it is the selected part. 2. Show another part in that stack using PartState.CREATE or PartState.VISIBLE. 3. The part should've been rendered. It is not.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/workbench/ui/internal/PartServiceImpl.java
MPart activePart = getActivePart();
		if (activePart == null) {
			activate(part);
			return part;
		}
		switch (partState) {
		case ACTIVATE:
			activate(part);
			return part;
		case VISIBLE:
			if (activePart.getParent() != part.getParent()) {
				bringToTop(part);
			}
		}
		return part;
	}
	public MPart showPart(String id, PartState partState) {
		Assert.isNotNull(id);
		Assert.isNotNull(partState);
		MPart part = findPart(id);
		if (part != null) {
			return showPart(part, partState);
		}
		MPartDescriptor descriptor = findDescriptor(id);
		part = createPart(descriptor);
		if (part == null) {
			return null;
		}
		return showNewPart(part, partState);
	}