Ensure active part receives focus on perspective switch

When switching a perspective, if a view exists in both the old and the
new perspective, it doesn't gain focus after the perspective switch.
This is contrary to the case in which a view is open only in the new
perspective. Since editors are shared between perspectives, the same bug
always occurs for editors - the editor will lose focus on a perspective
switch.

This change adds part focusing code on the code branch, on which the
active part already exists in the new perspective. This ensures the
active part gains focus.

Note that this change doesn't preserve focus of the active part in each
perspective. I.e. if View A is active in perspective X and View B was
active in perspective Y, upon switching to perspective Y, View A will
become active if it exists. The change only ensures that focus is not
lost altogether.

Fixes: #2839
Signed-off-by: Simeon Andreev <[email protected]>

Author: trancexpress

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

@@ -192,6 +192,10 @@ private MPart toPart(MStackElement stackElement) {
 
 	private boolean constructed = false;
 
+	private boolean switchingPerspective = false;
+
+	private boolean focusingActivePart = false;
+
 	@Inject
 	public PartServiceImpl(MApplication application, @Optional MWindow window) {
 		// no need to track changes:
@@ -604,6 +608,15 @@ public boolean isPartOrPlaceholderInPerspective(String elementId, MPerspective p
 
 	@Override
 	public void switchPerspective(MPerspective perspective) {
+		try {
+			switchingPerspective = true;
+			switchPerspectiveInternal(perspective);
+		} finally {
+			switchingPerspective = false;
+		}
+	}
+
+	private void switchPerspectiveInternal(MPerspective perspective) {
 		Assert.isNotNull(perspective);
 		MWindow window = getWindow();
 		if (window != null && isInContainer(window, perspective)) {
@@ -687,6 +700,11 @@ public void activate(MPart part, boolean requiresFocus) {
 	}
 
 	private void activate(MPart part, boolean requiresFocus, boolean activateBranch) {
+		if (focusingActivePart) {
+			Activator.trace(Policy.DEBUG_FOCUS_FLAG,
+					"Active part is being focused on perspective switch: " + activePart, null);//$NON-NLS-1$
+			return;
+		}
 		if (part == null) {
 			if (constructed && activePart != null) {
 				if (Policy.DEBUG_FOCUS) {
@@ -727,12 +745,23 @@ private void activate(MPart part, boolean requiresFocus, boolean activateBranch)
 		IEclipseContext windowContext = window.getContext();
 		// check if the active part has changed or if we are no longer the active window
 		if (windowContext.getParent().getActiveChild() == windowContext && part == activePart) {
-			// insert it in the beginning of the activation history, it may not have been inserted
-			// pending when this service was instantiated
-			partActivationHistory.prepend(part);
-			UIEvents.publishEvent(UIEvents.UILifeCycle.ACTIVATE, part);
-			if (Policy.DEBUG_FOCUS) {
-				Activator.trace(Policy.DEBUG_FOCUS_FLAG, "Trying to activate already active part: " + part, null);//$NON-NLS-1$
+			if (!focusingActivePart) {
+				// insert it in the beginning of the activation history, it may not have been
+				// inserted
+				// pending when this service was instantiated
+				partActivationHistory.prepend(part);
+				if (switchingPerspective && requiresFocus) {
+					focusingActivePart = true;
+					try {
+						focusPart(part);
+					} finally {
+						focusingActivePart = false;
+					}
+				}
+				UIEvents.publishEvent(UIEvents.UILifeCycle.ACTIVATE, part);
+				if (Policy.DEBUG_FOCUS) {
+					Activator.trace(Policy.DEBUG_FOCUS_FLAG, "Trying to activate already active part: " + part, null);//$NON-NLS-1$
+				}
 			}
 			return;
 		}
@@ -1510,7 +1539,7 @@ private MElementContainer<? extends MUIElement> getContainer() {
 		return outerContainer;
 	}
 
-	private static void focusPart(MPart part) {
+	private void focusPart(MPart part) {
 		IEclipseContext context = part.getContext();
 		if (context != null) {
 			IPresentationEngine pe = context.get(IPresentationEngine.class);