Bug 318363 [UI] Closing Perspectives changes others
If you open the Debug perspective and then close it the Package Explorer disappears. Root cause was that I opened the second perspective using the perspective switcher which performed the operation 'locally' rather than going through the WorkbenchPage#setPerspective code. This meant that the 'openPerspectives' list wasn't updated which meant that the 'closePerspective' call delegated to 'closeAllPerspectives' since it thought there was only one open.
bundles/org.eclipse.e4.ui.workbench.addons.swt/src/org/eclipse/e4/ui/workbench/addons/minmax/TrimStack.java
public void run() {
						updateTrimStackItems();
					}
				});
			}
		}
	};
	private MTrimBar bar;
	private int fixedSides;
	@PostConstruct
	void addListeners() {
		eventBroker.subscribe(UIEvents.buildTopic(UIEvents.ElementContainer.TOPIC,
				UIEvents.ElementContainer.CHILDREN), childrenHandler);
		eventBroker.subscribe(
				UIEvents.buildTopic(UIEvents.UIElement.TOPIC, UIEvents.UIElement.TOBERENDERED),
				toBeRenderedHandler);
		eventBroker.subscribe(UIEvents.buildTopic(UIEvents.ElementContainer.TOPIC,
				UIEvents.ElementContainer.SELECTEDELEMENT), selectionHandler);
		eventBroker.subscribe(
				UIEvents.buildTopic(UIEvents.UIElement.TOPIC, UIEvents.UIElement.WIDGET),
				widgetHandler);
	}
	@PreDestroy
	void removeListeners() {
		eventBroker.unsubscribe(toBeRenderedHandler);
		eventBroker.unsubscribe(childrenHandler);
		eventBroker.unsubscribe(selectionHandler);
		eventBroker.unsubscribe(widgetHandler);
	}
	@PostConstruct