Bug 328339 Part activation history seems to ignore detached windows
1. Detach a view. 2. Drag another view into said detached window. 3. Activate the two views alternatively. 4. Close one of them. 5. A part in the workbench window is activated instead of the other view in the detached window.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartActivationHistory.java
private MPart getActivationCandidate(MPart part) {
		
		Collection<MPart> candidates = part.getContext().get(EPartService.class).getParts();
		for (MPart candidate : candidates) {
			
			if (part != candidate && candidate.isToBeRendered() && candidate.isVisible()) {
				MPlaceholder placeholder = candidate.getCurSharedRef();
				if (placeholder != null) {
					
					if (!placeholder.isToBeRendered() || !placeholder.isVisible()) {
						continue;
					}
				}
				MElementContainer<MUIElement> parent = placeholder == null ? candidate.getParent()
						: placeholder.getParent();
				
				if (isValid(parent)) {
					
					
					if (parent instanceof MGenericStack<?>) {
						
						MUIElement element = parent.getSelectedElement();
						
						if (element instanceof MPlaceholder) {
							element = ((MPlaceholder) element).getRef();
						}
						
						if (element == part) {
							return candidate;
						}