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 boolean isPartVisible(MPart part) {
		if (isInContainer(part)) {
			MUIElement element = part;
			MElementContainer<?> parent = part.getParent();
			if (parent == null) {
				
				element = part.getCurSharedRef();
				if (element == null) {
					return false;
				}
				
				parent = element.getParent();
				if (parent == null) {
					return false;
				}
			}
			if (parent instanceof MPartStack) {
				return parent.getSelectedElement() == element;
			}
			return element.isVisible();
		}
		return false;
	}
	private boolean isInContainer(MPart part) {
		return isInContainer(rootContainer, part);
	}
	private boolean isInContainer(MElementContainer<?> container, MPart part) {
		for (Object object : container.getChildren()) {
			if (object == part) {