Add "Find Class" action to the layout spy

ui/org.eclipse.tools.layout.spy/src/org/eclipse/tools/layout/spy/internal/dialogs/LayoutSpyDialog.java

@@ -82,6 +82,8 @@ public class LayoutSpyDialog {
 	private TreeViewer widgetTree;
 	private Text details;
 	private Button selectWidgetButton;
+	private Button findClassButton;
+	private Text modelInfo;
 	private Shell overlay;
 
 	// Model
@@ -219,19 +221,29 @@ private void createContents(Composite container) {
 		{
 			selectWidgetButton = new Button(buttonBar, SWT.PUSH);
 			selectWidgetButton.setText(Messages.LayoutSpyDialog_button_select_control);
+			findClassButton = new Button(buttonBar, SWT.PUSH);
+			findClassButton.setText(Messages.LayoutSpyDialog_button_find_class);
 			Button refreshButton = new Button(buttonBar, SWT.PUSH);
 			refreshButton.setText(Messages.LayoutSpyDialog_button_refresh);
 			refreshButton.addListener(SWT.Selection, event -> refreshTree());
 
-			GridLayoutFactory.fillDefaults().numColumns(2).generateLayout(buttonBar);
+			GridLayoutFactory.fillDefaults().numColumns(3).generateLayout(buttonBar);
 		}
 		GridDataFactory.fillDefaults().align(SWT.CENTER, SWT.CENTER).applyTo(buttonBar);
 
+		// Result of "Find Class": model element and implementing class of a clicked control.
+		Label modelLabel = new Label(container, SWT.NONE);
+		modelLabel.setText(Messages.LayoutSpyDialog_label_model_element);
+		modelInfo = new Text(container, SWT.READ_ONLY | SWT.MULTI | SWT.BORDER | SWT.V_SCROLL | SWT.H_SCROLL);
+		modelInfo.setText(Messages.LayoutSpyDialog_model_prompt);
+		GridDataFactory.fillDefaults().hint(300, 90).grab(true, false).applyTo(modelInfo);
+
 		GridLayoutFactory.fillDefaults().margins(LayoutConstants.getMargins()).generateLayout(container);
 
 		// Attach listeners
 		container.addDisposeListener(event -> disposed());
 		selectWidgetButton.addListener(SWT.Selection, event -> selectControl());
+		findClassButton.addListener(SWT.Selection, event -> findClass());
 
 		// Set up the model
 		widgetTree.setContentProvider(new WidgetTreeContentProvider());
@@ -487,6 +499,28 @@ private void selectControl() {
 		});
 	}
 
+	/**
+	 * Hides the spy, lets the user click a control and then shows the owning
+	 * application-model element and its implementing class.
+	 */
+	private void findClass() {
+		this.controlSelectorOpen.setValue(true);
+		// Only hide our own dialog; as a part this shell is the workbench window.
+		boolean ownsShell = shell != null;
+		if (ownsShell) {
+			shell.setVisible(false);
+		}
+		new ControlSelector((@Nullable Control control) -> {
+			if (control != null && !modelInfo.isDisposed()) {
+				modelInfo.setText(ModelElementResolver.describe(control));
+			}
+			this.controlSelectorOpen.setValue(false);
+			if (ownsShell) {
+				shell.setVisible(true);
+			}
+		});
+	}
+
 	/**
 	 * Copies the diagnostic information of the selected control and all of its
 	 * descendants to the clipboard as text, for pasting into bug reports.

ui/org.eclipse.tools.layout.spy/src/org/eclipse/tools/layout/spy/internal/dialogs/Messages.java

@@ -21,10 +21,13 @@ public class Messages extends NLS {
 	public static String LayoutSpyDialog_shell_text;
 	public static String LayoutSpyDialog_button_refresh;
 	public static String LayoutSpyDialog_button_select_control;
+	public static String LayoutSpyDialog_button_find_class;
 	public static String LayoutSpyDialog_button_show_overlay;
 	public static String LayoutSpyDialog_button_show_coloring;
 	public static String LayoutSpyDialog_label_widget_tree;
 	public static String LayoutSpyDialog_label_layout;
+	public static String LayoutSpyDialog_label_model_element;
+	public static String LayoutSpyDialog_model_prompt;
 	public static String LayoutSpyDialog_menu_copy_widget_info;
 	public static String LayoutSpyDialog_label_no_control_selected;
 	public static String LayoutSpyDialog_label_not_a_composite;

ui/org.eclipse.tools.layout.spy/src/org/eclipse/tools/layout/spy/internal/dialogs/ModelElementResolver.java

@@ -0,0 +1,145 @@
+/*******************************************************************************
+ * Copyright (c) 2026 Vogella GmbH and others.
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Lars Vogel <Lars.Vogel@vogella.com> - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.tools.layout.spy.internal.dialogs;
+
+import java.lang.reflect.Method;
+
+import org.eclipse.e4.ui.model.application.MContribution;
+import org.eclipse.e4.ui.model.application.ui.MUIElement;
+import org.eclipse.jdt.annotation.Nullable;
+import org.eclipse.swt.widgets.Control;
+import org.eclipse.swt.widgets.Shell;
+import org.osgi.framework.Bundle;
+import org.osgi.framework.FrameworkUtil;
+
+/**
+ * Resolves an SWT {@link Control} to the owning e4 application-model element and
+ * describes its implementing Java class.
+ * <p>
+ * The e4 SWT renderer tags each widget with its owning {@link MUIElement} under
+ * the data key {@code "modelElement"} ({@code AbstractPartRenderer.OWNING_ME}).
+ * That constant is in an {@code x-friends} package, so the literal is used here.
+ */
+public final class ModelElementResolver {
+
+	/** Widget data key set by the e4 SWT renderer, == AbstractPartRenderer.OWNING_ME. */
+	private static final String OWNING_MODEL_ELEMENT_KEY = "modelElement"; //$NON-NLS-1$
+
+	/** Wrapper for 3.x parts; unwrapped to reveal the real view/editor class. */
+	private static final String COMPATIBILITY_PART_CLASS = "org.eclipse.ui.internal.e4.compatibility.CompatibilityPart"; //$NON-NLS-1$
+
+	private static final String MODEL_PACKAGE_PREFIX = "org.eclipse.e4.ui.model."; //$NON-NLS-1$
+
+	private ModelElementResolver() {
+	}
+
+	/**
+	 * Returns the closest model element owning the control, walking up its
+	 * parents, or {@code null} if none (for example a plain JFace dialog).
+	 */
+	public static @Nullable MUIElement findModelElement(Control control) {
+		for (Control current = control; current != null; current = current.getParent()) {
+			if (current.getData(OWNING_MODEL_ELEMENT_KEY) instanceof MUIElement element) {
+				return element;
+			}
+		}
+		return null;
+	}
+
+	/** Builds a copyable description of the model element and implementing class. */
+	public static String describe(Control control) {
+		StringBuilder builder = new StringBuilder();
+		builder.append("Control class: ").append(control.getClass().getName()).append('\n'); //$NON-NLS-1$
+
+		MUIElement element = findModelElement(control);
+		if (element == null) {
+			describeWithoutModel(control, builder);
+			return builder.toString();
+		}
+
+		builder.append('\n');
+		builder.append("Model element: ").append(modelTypeName(element)); //$NON-NLS-1$
+		String id = element.getElementId();
+		if (id != null && !id.isEmpty()) {
+			builder.append(" (id=").append(id).append(')'); //$NON-NLS-1$
+		}
+		builder.append('\n');
+
+		if (element instanceof MContribution contribution) {
+			describeContribution(contribution, builder);
+		}
+		return builder.toString();
+	}
+
+	private static void describeWithoutModel(Control control, StringBuilder builder) {
+		builder.append('\n');
+		builder.append("No application model element is associated with this control.").append('\n'); //$NON-NLS-1$
+		Shell shell = control.getShell();
+		builder.append("Shell class: ").append(shell.getClass().getName()).append('\n'); //$NON-NLS-1$
+		Object shellData = shell.getData();
+		if (shellData != null) {
+			builder.append("Shell data class: ").append(shellData.getClass().getName()).append('\n'); //$NON-NLS-1$
+		}
+	}
+
+	private static void describeContribution(MContribution contribution, StringBuilder builder) {
+		String uri = contribution.getContributionURI();
+		if (uri != null && !uri.isEmpty()) {
+			builder.append("Contribution URI: ").append(uri).append('\n'); //$NON-NLS-1$
+		}
+		Object object = contribution.getObject();
+		if (object == null) {
+			return;
+		}
+		Object implementation = unwrapCompatibilityPart(object);
+		Class<?> implementationClass = implementation.getClass();
+		builder.append("Implementing class: ").append(implementationClass.getName()).append('\n'); //$NON-NLS-1$
+		if (implementation != object) {
+			builder.append("Wrapped by: ").append(object.getClass().getName()).append('\n'); //$NON-NLS-1$
+		}
+		Bundle bundle = FrameworkUtil.getBundle(implementationClass);
+		if (bundle != null) {
+			builder.append("Contributing bundle: ").append(bundle.getSymbolicName()).append('\n'); //$NON-NLS-1$
+		}
+	}
+
+	/** Most specific model interface name (e.g. {@code MPart}) of the element. */
+	private static String modelTypeName(MUIElement element) {
+		for (Class<?> iface : element.getClass().getInterfaces()) {
+			if (iface.getName().startsWith(MODEL_PACKAGE_PREFIX)) {
+				return iface.getSimpleName();
+			}
+		}
+		return element.getClass().getSimpleName();
+	}
+
+	/** Unwraps a 3.x compatibility part to its real {@code IWorkbenchPart}; else returns the object. */
+	private static Object unwrapCompatibilityPart(Object object) {
+		for (Class<?> type = object.getClass(); type != null; type = type.getSuperclass()) {
+			if (COMPATIBILITY_PART_CLASS.equals(type.getName())) {
+				try {
+					Method getPart = object.getClass().getMethod("getPart"); //$NON-NLS-1$
+					Object part = getPart.invoke(object);
+					if (part != null) {
+						return part;
+					}
+				} catch (ReflectiveOperationException e) {
+					// Best effort only; fall back to the wrapper class.
+				}
+				break;
+			}
+		}
+		return object;
+	}
+}

ui/org.eclipse.tools.layout.spy/src/org/eclipse/tools/layout/spy/internal/dialogs/messages.properties

@@ -1,10 +1,13 @@
 LayoutSpyDialog_shell_text=Layout Spy
 LayoutSpyDialog_button_refresh=&Refresh
 LayoutSpyDialog_button_select_control=Select &Control
+LayoutSpyDialog_button_find_class=Find &Class
 LayoutSpyDialog_button_show_overlay=Show &overlay
 LayoutSpyDialog_button_show_coloring=Color controls and add tooltip with layout info (requires resize)
 LayoutSpyDialog_label_widget_tree=Widget tree:
 LayoutSpyDialog_label_layout=Layout:
+LayoutSpyDialog_label_model_element=Selected model element:
+LayoutSpyDialog_model_prompt=Press "Find Class" and then click a view, editor or dialog to see its application model element and implementing class.
 LayoutSpyDialog_menu_copy_widget_info=Copy &Widget Info
 LayoutSpyDialog_label_no_control_selected=No control selected
 LayoutSpyDialog_label_not_a_composite=Selected control is not a Composite, so it has no layout.