Handle the case when application has no focus in ApplicationPartService

Currently when the application has no focus there is also no active
window child and in this case several actions still fail even though a
part is available for perform actions.

This now handles the case of an application without focus with an empty
optional to allow fall back to the part context. If that context has
still no suitable part service implementation as a last resort the
containing window context is used.

Author: laeubi

bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/ApplicationPartServiceImpl.java

@@ -27,6 +27,7 @@
 import org.eclipse.e4.ui.model.application.ui.advanced.MPerspective;
 import org.eclipse.e4.ui.model.application.ui.advanced.MPlaceholder;
 import org.eclipse.e4.ui.model.application.ui.basic.MPart;
+import org.eclipse.e4.ui.model.application.ui.basic.MWindow;
 import org.eclipse.e4.ui.workbench.UIEvents;
 import org.eclipse.e4.ui.workbench.modeling.EModelService;
 import org.eclipse.e4.ui.workbench.modeling.EPartService;
@@ -35,7 +36,7 @@
 public class ApplicationPartServiceImpl implements EPartService {
 
 	private static final Supplier<RuntimeException> NO_VALID_PARTSERVICE = () -> new IllegalStateException(
-			"No valid PartService can be aquired from the current context"); //$NON-NLS-1$
+			"No valid PartService can be acquired from the current context"); //$NON-NLS-1$
 
 	private MApplication application;
 
@@ -50,15 +51,17 @@ public class ApplicationPartServiceImpl implements EPartService {
 	private Optional<EPartService> getActiveWindowService() {
 		IEclipseContext activeWindowContext = application.getContext().getActiveChild();
 		if (activeWindowContext == null) {
-			throw new IllegalStateException("Application does not have an active window"); //$NON-NLS-1$
+			// in this case the application has no focus so we can't determine the active
+			// child.
+			return Optional.empty();
 		}
 		EPartService activeWindowPartService = activeWindowContext.get(EPartService.class);
 		if (activeWindowPartService == null) {
 			throw new IllegalStateException("Active window context is invalid"); //$NON-NLS-1$
 		}
 		if (activeWindowPartService == this) {
-			// in this cas we would run into an infinite recursion, so from the current
-			// active window we can't aquire another part service
+			// in this case we would run into an infinite recursion, so from the current
+			// active window we can't acquire another part service
 			return Optional.empty();
 		}
 		return Optional.of(activeWindowPartService);
@@ -68,10 +71,20 @@ private Optional<EPartService> getActiveWindowService(MPart part) {
 		return getActiveWindowService().or(() -> {
 			IEclipseContext context = part.getContext();
 			if (context != null) {
+				// First try the context of the part
 				EPartService partService = context.get(EPartService.class);
 				if (partService instanceof PartServiceImpl) {
 					return Optional.of(partService);
 				}
+				// Otherwise use the context of the contained window
+				MWindow window = modelService.getTopLevelWindowFor(part);
+				if (window != null) {
+					IEclipseContext windowContext = window.getContext();
+					EPartService windowPartService = windowContext.get(EPartService.class);
+					if (windowPartService instanceof PartServiceImpl) {
+						return Optional.of(windowPartService);
+					}
+				}
 			}
 			return Optional.empty();
 		});