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
if (parent instanceof MGenericStack) {
						if (parent.getSelectedElement() == placeholder) {
							return candidate;
						}
					} else {
						return candidate;
					}
				}
			}
		}
		return null;
	}
	MPart getNextActivationCandidate(MPart part) {
		MArea area = isInArea(part);
		if (area != null) {
			
			MPart candidate = getSiblingActivationCandidate(part);
			if (candidate != null) {
				return candidate;
			}
			
			candidate = findActivationCandidate(
					modelService.findElements(area, null, MPart.class, null), part);
			if (candidate != null) {
				return candidate;
			}
		}
		
		MPart candidate = findActivationCandidate(generalActivationHistory, part);