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.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
public int getActivated() {
			return activated;
		}
		public int getDeactivated() {
			return deactivated;
		}
		public int getHidden() {
			return hidden;
		}
		public int getVisible() {
			return visible;
		}
		public boolean isValid() {
			return valid;
		}
		public List<MPart> getActivatedParts() {
			return activatedParts;
		}
		public List<MPart> getDeactivatedParts() {
			return deactivatedParts;
		}
		public List<MPart> getHiddenParts() {
			return hiddenParts;
		}
		public List<MPart> getVisibleParts() {
			return visibleParts;
		}
		public void partActivated(MPart part) {
			if (valid && part == null) {
				valid = false;