Bug 322403 Showing a shared part with PartState.VISIBLE may not work correctly due to incorrect parent comparisons
We check the parents of the active part against the part-to-be-shown to determine how to respond when PartState.VISIBLE is used but the check is always 'true' for shared parts because getParent() returns 'null' for both parts. This is obviously wrong. We need to update the code to consider placeholders.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartServiceImpl.java
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 showPart(partState, part, part);
	}
	public MPart showPart(MPart part, PartState partState) {
		Assert.isNotNull(part);
		Assert.isNotNull(partState);
		MPart localPart = findPart(part.getElementId());
		if (localPart != null) {
			return showPart(partState, part, localPart);
		}
		return showPart(partState, part, part);
	}
	public void hidePart(MPart part) {
		hidePart(part, false);
	}
	public void hidePart(MPart part, boolean force) {
		if (isInContainer(part)) {
			MPlaceholder sharedRef = part.getCurSharedRef();
			if (sharedRef != null)