Activate content assist only when caret enters the viewer

Content assist is now activated only when the caret moves inside the
Detail Pane, preventing interference with Expressions View and Variables
Views and enhancing the overall user experience.

Fixes : #2151

Author: SougandhS

debug/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/views/variables/details/DefaultDetailPane.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- *  Copyright (c) 2006, 2019 IBM Corporation and others.
+ *  Copyright (c) 2006, 2026 IBM Corporation and others.
  *
  *  This program and the accompanying materials
  *  are made available under the terms of the Eclipse Public License 2.0
@@ -423,6 +423,10 @@ private boolean containsLineDelimiter(String str) {
 	private IPropertyChangeListener fPreferenceStorePropertyChangeListener;
 	private WhitespaceCharacterPainter fWhiteSpacePainter;
 
+	private TextViewerAction contentAssistAction;
+
+	private ActionHandler contentAssistActionHandler;
+
 	@Override
 	public Control createControl(Composite parent) {
 
@@ -542,6 +546,8 @@ public void focusGained(FocusEvent e) {
 
 				updateAction(DETAIL_FIND_REPLACE_TEXT_ACTION);
 				fHasFocus = true;
+				activateContentAssistHandler(contentAssistAction, contentAssistActionHandler);
+
 			}
 
 			@Override
@@ -556,6 +562,7 @@ public void focusLost(FocusEvent e) {
 
 				getViewSite().getActionBars().updateActionBars();
 				fHasFocus = false;
+				deactivateContentAssistHandler();
 			}
 		});
 
@@ -591,18 +598,29 @@ public void focusLost(FocusEvent e) {
 	 * Creates the actions to add to the context menu
 	 */
 	private void createActions() {
-		TextViewerAction textAction= new TextViewerAction(fSourceViewer, ISourceViewer.CONTENTASSIST_PROPOSALS);
-		textAction.setActionDefinitionId(ITextEditorActionDefinitionIds.CONTENT_ASSIST_PROPOSALS);
-		textAction.configureAction(DetailMessages.DefaultDetailPane_Co_ntent_Assist_3, IInternalDebugCoreConstants.EMPTY_STRING,IInternalDebugCoreConstants.EMPTY_STRING);
-		textAction.setImageDescriptor(DebugPluginImages.getImageDescriptor(IDebugUIConstants.IMG_ELCL_CONTENT_ASSIST));
-		textAction.setDisabledImageDescriptor(DebugPluginImages.getImageDescriptor(IDebugUIConstants.IMG_DLCL_CONTENT_ASSIST));
-		PlatformUI.getWorkbench().getHelpSystem().setHelp(textAction, IDebugHelpContextIds.DETAIL_PANE_CONTENT_ASSIST_ACTION);
-		ActionHandler actionHandler = new ActionHandler(textAction);
-		IHandlerService handlerService = getViewSite().getService(IHandlerService.class);
-		fContentAssistActivation = handlerService.activateHandler(textAction.getActionDefinitionId(), actionHandler);
-		setAction(DETAIL_CONTENT_ASSIST_ACTION, textAction);
-
-		textAction= new TextViewerAction(fSourceViewer, ITextOperationTarget.SELECT_ALL);
+		contentAssistAction = new TextViewerAction(fSourceViewer, ISourceViewer.CONTENTASSIST_PROPOSALS);
+
+		contentAssistAction.setActionDefinitionId(ITextEditorActionDefinitionIds.CONTENT_ASSIST_PROPOSALS);
+		contentAssistAction.configureAction(DetailMessages.DefaultDetailPane_Co_ntent_Assist_3,
+				IInternalDebugCoreConstants.EMPTY_STRING, IInternalDebugCoreConstants.EMPTY_STRING);
+		contentAssistAction
+				.setImageDescriptor(DebugPluginImages.getImageDescriptor(IDebugUIConstants.IMG_ELCL_CONTENT_ASSIST));
+		contentAssistAction.setDisabledImageDescriptor(
+				DebugPluginImages.getImageDescriptor(IDebugUIConstants.IMG_DLCL_CONTENT_ASSIST));
+		PlatformUI.getWorkbench().getHelpSystem().setHelp(contentAssistAction,
+				IDebugHelpContextIds.DETAIL_PANE_CONTENT_ASSIST_ACTION);
+		contentAssistActionHandler = new ActionHandler(contentAssistAction);
+		setAction(DETAIL_CONTENT_ASSIST_ACTION, contentAssistAction);
+
+		StyledText text = fSourceViewer.getTextWidget();
+
+		text.addCaretListener(event -> {
+			if (text.isFocusControl()) {
+				activateContentAssistHandler(contentAssistAction, contentAssistActionHandler);
+			}
+		});
+
+		TextViewerAction textAction = new TextViewerAction(fSourceViewer, ITextOperationTarget.SELECT_ALL);
 		textAction.configureAction(DetailMessages.DefaultDetailPane_Select__All_5, IInternalDebugCoreConstants.EMPTY_STRING,IInternalDebugCoreConstants.EMPTY_STRING);
 		textAction.setActionDefinitionId(IWorkbenchCommandConstants.EDIT_SELECT_ALL);
 		PlatformUI.getWorkbench().getHelpSystem().setHelp(textAction, IDebugHelpContextIds.DETAIL_PANE_SELECT_ALL_ACTION);
@@ -650,10 +668,37 @@ private void createActions() {
 	}
 
 	/**
-	 * Create the context menu particular to the detail pane.  Note that anyone
+	 * Activates the content assist handler for the specified viewer action.
+	 *
+	 * @param contAssistTextViewer the viewer action providing the action definition
+	 *                             ID
+	 * @param actionHandler        the handler to activate
+	 */
+	private void activateContentAssistHandler(TextViewerAction contAssistTextViewer, ActionHandler actionHandler) {
+		if (fContentAssistActivation == null) {
+			IHandlerService handlerService = getViewSite().getService(IHandlerService.class);
+			fContentAssistActivation = handlerService.activateHandler(contAssistTextViewer.getActionDefinitionId(),
+					actionHandler);
+		}
+	}
+
+	/**
+	 * Deactivates the content assist handler.
+	 */
+	private void deactivateContentAssistHandler() {
+		if (fContentAssistActivation != null) {
+			IHandlerService handlerService = getViewSite().getService(IHandlerService.class);
+			handlerService.deactivateHandler(fContentAssistActivation);
+			fContentAssistActivation = null;
+		}
+	}
+
+	/**
+	 * Create the context menu particular to the detail pane. Note that anyone
 	 * wishing to contribute an action to this menu must use
 	 * <code>IDebugUIConstants.VARIABLE_VIEW_DETAIL_ID</code> as the
 	 * <code>targetID</code> in the extension XML.
+	 *
 	 * @param menuControl the control to create the context menu on
 	 */
 	protected void createDetailContextMenu(Control menuControl) {