Added dynamic tab alignment support in MultiPageEditorPart

- Added a new preference for multi-page editor tab alignment.
- Added a preference change listener to MultiPageEditorPart.
- Updated tab style based on the user's preference.

Author: praveen-skp

bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/IDEEditorsPreferencePage.java

@@ -62,6 +62,7 @@ protected Control createContents(Composite parent) {
 		createUseIPersistablePref(composite);
 		createPromptWhenStillOpenPref(composite);
 		createEditorReuseGroup(composite);
+		createAlignMultiPageEditorTabsOnTop(composite);
 
 		applyDialogFont(composite);
 

bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/IWorkbenchPreferenceConstants.java

@@ -624,6 +624,21 @@ public interface IWorkbenchPreferenceConstants {
 	 */
 	String DISABLE_OPEN_EDITOR_IN_PLACE = "DISABLE_OPEN_EDITOR_IN_PLACE"; //$NON-NLS-1$
 
+	/**
+	 * Workbench preference id for whether the tabs in the multi-page editor is
+	 * displayed on top. Note that tabs will be shown in the top only if this
+	 * preference is <code>true</code>.
+	 *
+	 * Boolean-valued: <code>true</code> show the tabs on the top, and
+	 * <code>false</code> if shown at the bottom.
+	 * <p>
+	 * The default value for this preference is: <code>false</code>
+	 * </p>
+	 *
+	 * @since 3.133
+	 */
+	String ALIGN_MULTI_PAGE_EDITOR_TABS_ON_TOP = "ALIGN_MULTI_PAGE_EDITOR_TABS_ON_TOP"; //$NON-NLS-1$
+
 	/**
 	 * Workbench preference id for indicating the size of the list of most recently
 	 * used working sets.

bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/WorkbenchMessages.java

@@ -452,6 +452,7 @@ public class WorkbenchMessages extends NLS {
 	public static String WorkbenchPreference_stickyCycleButton;
 	public static String WorkbenchPreference_RunInBackgroundButton;
 	public static String WorkbenchPreference_RunInBackgroundToolTip;
+	public static String WorkbenchPreference_AlignMultiPageEditorTabsOnTopButton;
 
 	// --- Appearance ---
 	public static String ViewsPreferencePage_Theme;

bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/dialogs/EditorsPreferencePage.java

@@ -74,6 +74,8 @@ public class EditorsPreferencePage extends PreferencePage implements IWorkbenchP
 
 	private Button allowInplaceEditor;
 
+	private Button alignMultiPageEditorTabsOnTop;
+
 	@Override
 	protected Control createContents(Composite parent) {
 		Composite composite = createComposite(parent);
@@ -132,6 +134,15 @@ protected void createPromptWhenStillOpenPref(Composite composite) {
 		setButtonLayoutData(promptWhenStillOpenEditor);
 	}
 
+	protected void createAlignMultiPageEditorTabsOnTop(Composite composite) {
+		alignMultiPageEditorTabsOnTop = new Button(composite, SWT.CHECK);
+		alignMultiPageEditorTabsOnTop
+				.setText(WorkbenchMessages.WorkbenchPreference_AlignMultiPageEditorTabsOnTopButton);
+		alignMultiPageEditorTabsOnTop.setSelection(
+				getAPIPreferenceStore().getBoolean(IWorkbenchPreferenceConstants.ALIGN_MULTI_PAGE_EDITOR_TABS_ON_TOP));
+		setButtonLayoutData(alignMultiPageEditorTabsOnTop);
+	}
+
 	protected Composite createComposite(Composite parent) {
 		Composite composite = new Composite(parent, SWT.NULL);
 		GridLayout layout = new GridLayout();
@@ -152,6 +163,8 @@ protected void performDefaults() {
 		IPreferenceStore store = getPreferenceStore();
 		allowInplaceEditor.setSelection(
 				!getAPIPreferenceStore().getDefaultBoolean(IWorkbenchPreferenceConstants.DISABLE_OPEN_EDITOR_IN_PLACE));
+		alignMultiPageEditorTabsOnTop.setSelection(getAPIPreferenceStore()
+				.getDefaultBoolean(IWorkbenchPreferenceConstants.ALIGN_MULTI_PAGE_EDITOR_TABS_ON_TOP));
 		useIPersistableEditor.setSelection(store.getDefaultBoolean(IPreferenceConstants.USE_IPERSISTABLE_EDITORS));
 		promptWhenStillOpenEditor.setSelection(getAPIPreferenceStore()
 				.getDefaultBoolean(IWorkbenchPreferenceConstants.PROMPT_WHEN_SAVEABLE_STILL_OPEN));
@@ -165,6 +178,8 @@ protected void performDefaults() {
 	@Override
 	public boolean performOk() {
 		IPreferenceStore store = getPreferenceStore();
+		getAPIPreferenceStore().setValue(IWorkbenchPreferenceConstants.ALIGN_MULTI_PAGE_EDITOR_TABS_ON_TOP,
+				alignMultiPageEditorTabsOnTop.getSelection());
 		getAPIPreferenceStore().setValue(IWorkbenchPreferenceConstants.DISABLE_OPEN_EDITOR_IN_PLACE,
 				!allowInplaceEditor.getSelection());
 		store.setValue(IPreferenceConstants.USE_IPERSISTABLE_EDITORS, useIPersistableEditor.getSelection());

bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/messages.properties

@@ -419,6 +419,7 @@ WorkbenchPreference_RunInBackgroundButton=Always r&un in background
 WorkbenchPreference_RunInBackgroundToolTip=Run long operations in the background where possible
 WorkbenchPreference_HeapStatusButton = Sho&w heap status
 WorkbenchPreference_HeapStatusButtonToolTip = Show the heap status area on the bottom of the window
+WorkbenchPreference_AlignMultiPageEditorTabsOnTopButton= &Align multi-page editor tabs on top
 
 
 # --- Appearance ---
@@ -493,7 +494,7 @@ OpenPerspectiveDialogAction_tooltip=Open Perspective
 
 #---- General Preferences----
 PreferencePage_noDescription = (No description available)
-PreferencePageParameterValues_pageLabelSeparator = \ >\ 
+PreferencePageParameterValues_pageLabelSeparator = \ >\
 ThemingEnabled = E&nable theming
 ThemeChangeWarningText = Restart for the theme changes to take full effect
 ThemeChangeWarningTitle = Theme Changed

bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/part/MultiPageEditorPart.java

@@ -17,6 +17,7 @@
 
 import static org.eclipse.swt.events.SelectionListener.widgetSelectedAdapter;
 
+import java.beans.PropertyChangeListener;
 import java.util.ArrayList;
 import java.util.List;
 import org.eclipse.core.commands.AbstractHandler;
@@ -32,7 +33,9 @@
 import org.eclipse.jface.dialogs.IPageChangeProvider;
 import org.eclipse.jface.dialogs.IPageChangedListener;
 import org.eclipse.jface.dialogs.PageChangedEvent;
+import org.eclipse.jface.preference.IPreferenceStore;
 import org.eclipse.jface.resource.ImageDescriptor;
+import org.eclipse.jface.util.PropertyChangeEvent;
 import org.eclipse.jface.util.SafeRunnable;
 import org.eclipse.jface.viewers.ISelectionProvider;
 import org.eclipse.jface.viewers.SelectionChangedEvent;
@@ -56,13 +59,15 @@
 import org.eclipse.ui.IPartService;
 import org.eclipse.ui.IWorkbenchPart;
 import org.eclipse.ui.IWorkbenchPartSite;
+import org.eclipse.ui.IWorkbenchPreferenceConstants;
 import org.eclipse.ui.PartInitException;
 import org.eclipse.ui.handlers.IHandlerService;
 import org.eclipse.ui.internal.PartSite;
 import org.eclipse.ui.internal.WorkbenchPlugin;
 import org.eclipse.ui.internal.misc.Policy;
 import org.eclipse.ui.internal.services.INestable;
 import org.eclipse.ui.internal.services.IServiceLocatorCreator;
+import org.eclipse.ui.internal.util.PrefUtil;
 import org.eclipse.ui.services.IDisposable;
 import org.eclipse.ui.services.IServiceLocator;
 
@@ -149,10 +154,31 @@ public abstract class MultiPageEditorPart extends EditorPart implements IPageCha
 	private ListenerList<IPageChangedListener> pageChangeListeners = new ListenerList<>(ListenerList.IDENTITY);
 
 	/**
-	 * Creates an empty multi-page editor with no pages.
+	 * Creates an empty multi-page editor with no pages and registers a
+	 * {@link PropertyChangeListener} to listen for changes to the editor's
+	 * preference..
 	 */
 	protected MultiPageEditorPart() {
 		super();
+		getAPIPreferenceStore().addPropertyChangeListener(event -> {
+			handlePropertyChange(event);
+		});
+	}
+
+	/**
+	 * Handles property change events related to editor preferences.
+	 *
+	 * <p>
+	 * This method is invoked when a property change occurs in the preference store.
+	 * </p>
+	 *
+	 * @param event the {@link PropertyChangeEvent} triggered by a change in the
+	 *              preference store
+	 */
+	private void handlePropertyChange(PropertyChangeEvent event) {
+		if (event.getProperty().equals(IWorkbenchPreferenceConstants.ALIGN_MULTI_PAGE_EDITOR_TABS_ON_TOP)) {
+			updateContainer();
+		}
 	}
 
 	/**
@@ -264,7 +290,7 @@ protected CTabFolder createContainer(Composite parent) {
 		// use SWT.FLAT style so that an extra 1 pixel border is not reserved
 		// inside the folder
 		parent.setLayout(new FillLayout());
-		final CTabFolder newContainer = new CTabFolder(parent, SWT.BOTTOM | SWT.FLAT);
+		final CTabFolder newContainer = new CTabFolder(parent, getPreferredTabStyle());
 		newContainer.addSelectionListener(widgetSelectedAdapter(e -> {
 			int newPageIndex = newContainer.indexOf((CTabItem) e.item);
 			pageChange(newPageIndex);
@@ -291,6 +317,31 @@ protected CTabFolder createContainer(Composite parent) {
 		return newContainer;
 	}
 
+	/**
+	 * Determines the preferred tab style based on user preferences.
+	 * <p>
+	 * This method retrieves the user preference for aligning multi-page editor tabs
+	 * on top or bottom, and returns the corresponding SWT style constant.
+	 * </p>
+	 *
+	 * @return {@code SWT.TOP} if the user prefers tabs to be aligned on top,
+	 *         {@code SWT.BOTTOM} if the user prefers tabs to be aligned on the
+	 *         bottom.
+	 */
+	private int getPreferredTabStyle() {
+		boolean alignTabsOnTop = getAPIPreferenceStore()
+				.getBoolean(IWorkbenchPreferenceConstants.ALIGN_MULTI_PAGE_EDITOR_TABS_ON_TOP);
+		int style = alignTabsOnTop ? SWT.TOP : SWT.BOTTOM;
+		return style;
+	}
+
+	/**
+	 * @since 3.133
+	 */
+	protected IPreferenceStore getAPIPreferenceStore() {
+		return PrefUtil.getAPIPreferenceStore();
+	}
+
 	/**
 	 * Creates a tab item at the given index and places the given control in the new
 	 * item. The item is a CTabItem with no style bits set.
@@ -1230,4 +1281,13 @@ public void run() {
 			});
 		}
 	}
+
+	private void updateContainer() {
+		Composite container = getContainer();
+		if (container instanceof CTabFolder tabFolder) {
+			tabFolder.setTabPosition(getPreferredTabStyle());
+			tabFolder.requestLayout();
+		}
+	}
+
 }