Bug 319169 [UI] active parts in Detached windows prevent activating a part in the main window
Start with a fresh WS Detach the Outline view using DnD Now you can no longer activate any part in the main window (i.e. Package Explorer). The cause seems to be that the 'rootContainer' has become the DW's MTrimmedWindow rather than the DW's containing MPerspective. This causes the PartService's 'activate' to fail the 'isInContainer()' test...
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
public void testIsPartVisible_NotInStackTrueTrue() {
		testIsPartVisible_NotInStack(true, true);
	}
	public void testIsPartVisible_NotInStackTrueFalse() {
		testIsPartVisible_NotInStack(true, false);
	}
	public void testIsPartVisible_NotInStackFalseTrue() {
		testIsPartVisible_NotInStack(false, true);
	}
	public void testIsPartVisible_NotInStackFalseFalse() {
		testIsPartVisible_NotInStack(false, false);
	}
	public void testIsPartVisible_ViewVisible() {
		MApplication application = createApplication("partId");
		MWindow window = application.getChildren().get(0);
		MPartStack partStack = (MPartStack) window.getChildren().get(0);
		MPart part = (MPart) partStack.getChildren().get(0);
		partStack.setSelectedElement(part);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		assertTrue(partService.isPartVisible(part));
	}
	public void testIsPartVisible_ViewVisible_myService() {
		MApplication application = createApplication("partId");
		MWindow window = application.getChildren().get(0);
		MPartStack partStack = (MPartStack) window.getChildren().get(0);
		MPart part = (MPart) partStack.getChildren().get(0);
		partStack.setSelectedElement(part);
		getEngine().createGui(window);