Sporadic "Widget is disposed" exception in ToolBarManagerRenderer

In case the toolbar item is contributed via an extension point, it
might happen that the corresponding widget is disposed, immediately
after creation. To avoid any errors further down the invocation chain,
the call to createWidget() must then return null, rather than the
invalid widget.

One use-case where this might happen is if the handler bound to this
toolbar item tries to access the workbench window. If the window hasn't
been created yet, this can force a recreation of the toolbar, disposing
the current widget in the process.

See the following commits for similar problems:
- 228b669
- e4d8434

Author: ptziegler

bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/ToolBarManagerRenderer.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2009, 2020 IBM Corporation and others.
+ * Copyright (c) 2009, 2025 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -429,13 +429,17 @@ public Object createWidget(final MUIElement element, Object parent) {
 			IEclipseContext parentContext = getContextForParent(element);
 
 			CSSRenderingUtils cssUtils = parentContext.get(CSSRenderingUtils.class);
-			if (cssUtils != null) {
+			if (cssUtils != null && !newTB.isDisposed()) {
 				MUIElement modelElement = (MUIElement) newTB.getData(AbstractPartRenderer.OWNING_ME);
 				boolean draggable = ((modelElement != null) && (modelElement.getTags().contains(IPresentationEngine.DRAGGABLE)));
 				renderedCtrl = cssUtils.frameMeIfPossible(newTB, null, vertical, draggable);
 			}
 		}
 
+		if (renderedCtrl.isDisposed()) {
+			return null;
+		}
+
 		return renderedCtrl;
 	}
 

tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/workbench/renderers/swt/ToolBarManagerRendererTest.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2019, 2020 Rolf Theunissen and others.
+ * Copyright (c) 2019, 2025 Rolf Theunissen and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -21,15 +21,21 @@
 import static org.junit.Assert.assertTrue;
 
 import jakarta.inject.Inject;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import org.eclipse.core.runtime.ILogListener;
+import org.eclipse.core.runtime.Platform;
+import org.eclipse.e4.core.services.events.IEventBroker;
 import org.eclipse.e4.ui.model.application.MApplication;
 import org.eclipse.e4.ui.model.application.ui.basic.MTrimBar;
 import org.eclipse.e4.ui.model.application.ui.basic.MTrimmedWindow;
 import org.eclipse.e4.ui.model.application.ui.menu.MDirectToolItem;
 import org.eclipse.e4.ui.model.application.ui.menu.MToolBar;
+import org.eclipse.e4.ui.model.application.ui.menu.MToolBarContribution;
 import org.eclipse.e4.ui.model.application.ui.menu.MToolItem;
 import org.eclipse.e4.ui.tests.rules.WorkbenchContextRule;
+import org.eclipse.e4.ui.workbench.UIEvents;
 import org.eclipse.e4.ui.workbench.modeling.EModelService;
 import org.eclipse.emf.common.util.ECollections;
 import org.eclipse.jface.action.Action;
@@ -38,6 +44,7 @@
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
+import org.osgi.service.event.EventHandler;
 
 public class ToolBarManagerRendererTest {
 
@@ -50,6 +57,10 @@ public class ToolBarManagerRendererTest {
 	@Inject
 	private MApplication application;
 
+	@Inject
+	private IEventBroker eventBroker;
+
+	private String toolBarId;
 	private MToolBar toolBar;
 	private MTrimmedWindow window;
 
@@ -61,7 +72,9 @@ public void setUp() throws Exception {
 		MTrimBar trimBar = ems.createModelElement(MTrimBar.class);
 		window.getTrimBars().add(trimBar);
 
+		toolBarId = "ToolBarManagerRendererTest.toolBar";
 		toolBar = ems.createModelElement(MToolBar.class);
+		toolBar.setElementId(toolBarId);
 		trimBar.getChildren().add(toolBar);
 	}
 
@@ -119,6 +132,38 @@ public void testMToolItem_toBeRendered() {
 		assertTrue(tbm.getItems()[0].isVisible());
 	}
 
+	@Test
+	public void testMToolBarContribution_toBeRendered() {
+		List<String> errors = new ArrayList<>();
+
+		EventHandler eventHandler = event -> {
+			if (UIEvents.isADD(event)) {
+				MToolBar toolbar = (MToolBar) event.getProperty(UIEvents.EventTags.ELEMENT);
+				toolbar.setToBeRendered(false);
+			}
+		};
+
+		ILogListener logListener = (status, plugin) -> errors.add(plugin + ":" + status);
+
+		try {
+			Platform.addLogListener(logListener);
+			eventBroker.subscribe(UIEvents.ElementContainer.TOPIC_CHILDREN, eventHandler);
+
+			MToolBarContribution toolContribution = ems.createModelElement(MToolBarContribution.class);
+			toolContribution.setParentId(toolBarId);
+			toolContribution.getChildren().add(ems.createModelElement(MDirectToolItem.class));
+			application.getToolBarContributions().add(toolContribution);
+
+			contextRule.createAndRunWorkbench(window);
+
+			assertNull(toolBar.getRenderer());
+			assertTrue("Error(s) occurred while rendering toolbar: " + errors, errors.isEmpty());
+		} finally {
+			eventBroker.unsubscribe(eventHandler);
+			Platform.removeLogListener(logListener);
+		}
+	}
+
 	@Test
 	public void testDynamicItem_AddOne() {
 		contextRule.createAndRunWorkbench(window);