Bug 566317 - Replace Helper with JFace Util.isValid in content assistsI20200922-1800I20200921-1800I20200920-1800I20200919-1800I20200918-1800I20200917-1800I20200916-1800I20200916-0410I20200915-1800

Change-Id: Iede1dcb37b946485cd981a80dd796e5b14d4027e
Signed-off-by: Lars Vogel <Lars.Vogel@vogella.com>

12 files changed, 133 insertions, 181 deletions

diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/CompletionProposalPopup2.java b/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/CompletionProposalPopup2.java
index 292c04a6f8a..d48f4bcfe11 100644
--- a/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/CompletionProposalPopup2.java
+++ b/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/CompletionProposalPopup2.java
@@ -14,6 +14,8 @@
  *******************************************************************************/
 package org.eclipse.jface.internal.text.link.contentassist;
 
+import static org.eclipse.jface.util.Util.isValid;
+
 import java.util.ArrayList;
 import java.util.List;
 
@@ -126,8 +128,8 @@ class CompletionProposalPopup2 implements IContentAssistListener2 {
 
 		@Override
 		public boolean ownsFocusShell() {
-			return Helper2.okToUse(fProposalShell) && fProposalShell.isFocusControl()
-					|| Helper2.okToUse(fProposalTable) && fProposalTable.isFocusControl();
+			return isValid(fProposalShell) && fProposalShell.isFocusControl()
+					|| isValid(fProposalTable) && fProposalTable.isFocusControl();
 		}
 
 	};
@@ -177,7 +179,7 @@ class CompletionProposalPopup2 implements IContentAssistListener2 {
 			fKeyListener= new KeyListener() {
 				@Override
 				public void keyPressed(KeyEvent e) {
-					if (!Helper2.okToUse(fProposalShell))
+					if (!isValid(fProposalShell))
 						return;
 
 					if (e.character == 0 && e.keyCode == SWT.CTRL) {
@@ -190,7 +192,7 @@ class CompletionProposalPopup2 implements IContentAssistListener2 {
 
 				@Override
 				public void keyReleased(KeyEvent e) {
-					if (!Helper2.okToUse(fProposalShell))
+					if (!isValid(fProposalShell))
 						return;
 
 					if (e.character == 0 && e.keyCode == SWT.CTRL) {
@@ -268,7 +270,7 @@ class CompletionProposalPopup2 implements IContentAssistListener2 {
 	 * Creates the proposal selector.
 	 */
 	private void createProposalSelector() {
-		if (Helper2.okToUse(fProposalShell))
+		if (isValid(fProposalShell))
 			return;
 
 		Control control= fViewer.getTextWidget();
@@ -468,7 +470,7 @@ class CompletionProposalPopup2 implements IContentAssistListener2 {
 	 * @return <code>true</code> if the popup has the focus
 	 */
 	public boolean hasFocus() {
-		if (Helper2.okToUse(fProposalShell))
+		if (isValid(fProposalShell))
 			return (fProposalShell.isFocusControl() || fProposalTable.isFocusControl());
 
 		return false;
@@ -486,7 +488,7 @@ class CompletionProposalPopup2 implements IContentAssistListener2 {
 			registry.unregister(fFocusEditingSupport);
 		}
 
-		if (Helper2.okToUse(fProposalShell)) {
+		if (isValid(fProposalShell)) {
 			fContentAssistant.removeContentAssistListener(this, ContentAssistant2.PROPOSAL_SELECTOR);
 
 			fPopupCloser.uninstall();
@@ -543,7 +545,7 @@ class CompletionProposalPopup2 implements IContentAssistListener2 {
 	 * @param proposals the proposals
 	 */
 	private void setProposals(ICompletionProposal[] proposals) {
-		if (Helper2.okToUse(fProposalTable)) {
+		if (isValid(fProposalTable)) {
 
 			ICompletionProposal oldProposal= getSelectedProposal();
 			if (oldProposal instanceof ICompletionProposalExtension2)
@@ -704,7 +706,7 @@ class CompletionProposalPopup2 implements IContentAssistListener2 {
 			// see bug 47511: setVisible may run the event loop on GTK
 			// and trigger a rentrant call - have to check whether we are still
 			// visible
-			if (!Helper2.okToUse(fProposalShell))
+			if (!isValid(fProposalShell))
 				return;
 
 
@@ -717,7 +719,7 @@ class CompletionProposalPopup2 implements IContentAssistListener2 {
 
 		@Override
 		public boolean verifyKey(VerifyEvent e) {
-			if (!Helper2.okToUse(fProposalShell))
+			if (!isValid(fProposalShell))
 				return true;
 
 			char key= e.character;
@@ -977,7 +979,7 @@ class CompletionProposalPopup2 implements IContentAssistListener2 {
 	 * @since 3.0
 	 */
 	public void setFocus() {
-		if (Helper2.okToUse(fProposalShell))
+		if (isValid(fProposalShell))
 			fProposalShell.setFocus();
 	}
 }
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/ContentAssistant2.java b/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/ContentAssistant2.java
index e41f75837ce..452455d9b22 100644
--- a/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/ContentAssistant2.java
+++ b/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/ContentAssistant2.java
@@ -13,6 +13,8 @@
  *******************************************************************************/
 package org.eclipse.jface.internal.text.link.contentassist;
 
+import static org.eclipse.jface.util.Util.isValid;
+
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -92,7 +94,7 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 		 */
 		protected void install() {
 			Control w= fViewer.getTextWidget();
-			if (Helper2.okToUse(w)) {
+			if (isValid(w)) {
 
 				Shell shell= w.getShell();
 				fShell= shell;
@@ -117,11 +119,11 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 		protected void uninstall() {
 			Shell shell= fShell;
 			fShell= null;
-			if (Helper2.okToUse(shell))
+			if (isValid(shell))
 				shell.removeControlListener(this);
 
 			Control w= fViewer.getTextWidget();
-			if (Helper2.okToUse(w)) {
+			if (isValid(w)) {
 
 				w.removeMouseListener(this);
 				w.removeFocusListener(this);
@@ -375,14 +377,14 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 			switch (type) {
 				case LAYOUT_PROPOSAL_SELECTOR:
 					if (fContextType == LAYOUT_CONTEXT_SELECTOR &&
-							Helper2.okToUse(fShells[LAYOUT_CONTEXT_SELECTOR])) {
+							isValid(fShells[LAYOUT_CONTEXT_SELECTOR])) {
 						// Restore event notification to the tip popup.
 						addContentAssistListener((IContentAssistListener2) fPopups[LAYOUT_CONTEXT_SELECTOR], CONTEXT_SELECTOR);
 					}
 					break;
 
 				case LAYOUT_CONTEXT_SELECTOR:
-					if (Helper2.okToUse(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
+					if (isValid(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
 						if (fProposalPopupOrientation == PROPOSAL_STACKED)
 							layout(LAYOUT_PROPOSAL_SELECTOR, getSelectionOffset());
 						// Restore event notification to the proposal popup.
@@ -392,7 +394,7 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 					break;
 
 				case LAYOUT_CONTEXT_INFO_POPUP:
-					if (Helper2.okToUse(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
+					if (isValid(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
 						if (fContextInfoPopupOrientation == CONTEXT_INFO_BELOW)
 							layout(LAYOUT_PROPOSAL_SELECTOR, getSelectionOffset());
 					}
@@ -426,13 +428,13 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 		protected void layoutProposalSelector(int offset) {
 			if (fContextType == LAYOUT_CONTEXT_INFO_POPUP &&
 					fContextInfoPopupOrientation == CONTEXT_INFO_BELOW &&
-					Helper2.okToUse(fShells[LAYOUT_CONTEXT_INFO_POPUP])) {
+					isValid(fShells[LAYOUT_CONTEXT_INFO_POPUP])) {
 				// Stack proposal selector beneath the tip box.
 				Shell shell= fShells[LAYOUT_PROPOSAL_SELECTOR];
 				Shell parent= fShells[LAYOUT_CONTEXT_INFO_POPUP];
 				shell.setLocation(getStackedLocation(shell, parent));
 			} else if (fContextType != LAYOUT_CONTEXT_SELECTOR ||
-						!Helper2.okToUse(fShells[LAYOUT_CONTEXT_SELECTOR])) {
+					!isValid(fShells[LAYOUT_CONTEXT_SELECTOR])) {
 				// There are no other presentations to be concerned with,
 				// so place the proposal selector beneath the cursor line.
 				Shell shell= fShells[LAYOUT_PROPOSAL_SELECTOR];
@@ -469,7 +471,7 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 			Shell shell= fShells[LAYOUT_CONTEXT_SELECTOR];
 			shell.setLocation(getBelowLocation(shell, offset));
 
-			if (Helper2.okToUse(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
+			if (isValid(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
 				switch (fProposalPopupOrientation) {
 					case PROPOSAL_REMOVE:
 						// Remove the proposal selector.
@@ -503,7 +505,7 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 					// Place the popup beneath the cursor line.
 					Shell parent= fShells[LAYOUT_CONTEXT_INFO_POPUP];
 					parent.setLocation(getBelowLocation(parent, offset));
-					if (Helper2.okToUse(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
+					if (isValid(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
 						// Stack the proposal selector beneath the context info popup.
 						Shell shell= fShells[LAYOUT_PROPOSAL_SELECTOR];
 						shell.setLocation(getStackedLocation(shell, parent));
@@ -582,12 +584,12 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 			switch (type) {
 				case LAYOUT_PROPOSAL_SELECTOR:
 					if (fContextType == LAYOUT_CONTEXT_SELECTOR &&
-							Helper2.okToUse(fShells[LAYOUT_CONTEXT_SELECTOR]))
+							isValid(fShells[LAYOUT_CONTEXT_SELECTOR]))
 						// Disable event notification to the tip selector.
 						removeContentAssistListener((IContentAssistListener2) fPopups[LAYOUT_CONTEXT_SELECTOR], CONTEXT_SELECTOR);
 					break;
 				case LAYOUT_CONTEXT_SELECTOR:
-					if (Helper2.okToUse(fShells[LAYOUT_PROPOSAL_SELECTOR]))
+					if (isValid(fShells[LAYOUT_PROPOSAL_SELECTOR]))
 						// Disable event notification to the proposal selector.
 						removeContentAssistListener((IContentAssistListener2) fPopups[LAYOUT_PROPOSAL_SELECTOR], PROPOSAL_SELECTOR);
 					break;
@@ -826,7 +828,7 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 					extension.appendVerifyKeyListener(fAutoAssistListener);
 				} else {
 					StyledText textWidget= fViewer.getTextWidget();
-					if (Helper2.okToUse(textWidget))
+					if (isValid(textWidget))
 						textWidget.addVerifyKeyListener(fAutoAssistListener);
 				}
 			}
@@ -838,7 +840,7 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 				extension.removeVerifyKeyListener(fAutoAssistListener);
 			} else {
 				StyledText textWidget= fViewer.getTextWidget();
-				if (Helper2.okToUse(textWidget))
+				if (isValid(textWidget))
 					textWidget.removeVerifyKeyListener(fAutoAssistListener);
 			}
 
@@ -1146,7 +1148,7 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 	private void installKeyListener() {
 		if (!fKeyListenerHooked) {
 			StyledText text= fViewer.getTextWidget();
-			if (Helper2.okToUse(text)) {
+			if (isValid(text)) {
 
 				if (fViewer instanceof ITextViewerExtension) {
 					ITextViewerExtension e= (ITextViewerExtension) fViewer;
@@ -1214,7 +1216,7 @@ public class ContentAssistant2 implements IContentAssistant, IContentAssistantEx
 	private void uninstallKeyListener() {
 		if (fKeyListenerHooked) {
 			StyledText text= fViewer.getTextWidget();
-			if (Helper2.okToUse(text)) {
+			if (isValid(text)) {
 
 				if (fViewer instanceof ITextViewerExtension) {
 					ITextViewerExtension e= (ITextViewerExtension) fViewer;
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/ContextInformationPopup2.java b/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/ContextInformationPopup2.java
index 2d2b8a52a29..3582d784ec7 100644
--- a/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/ContextInformationPopup2.java
+++ b/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/ContextInformationPopup2.java
@@ -15,6 +15,8 @@
 package org.eclipse.jface.internal.text.link.contentassist;
 
 
+import static org.eclipse.jface.util.Util.isValid;
+
 import java.util.Stack;
 
 import org.eclipse.swt.SWT;
@@ -238,7 +240,7 @@ class ContextInformationPopup2 implements IContentAssistListener2 {
 	 * Creates the context information popup. This is the tooltip like overlay window.
 	 */
 	private void createContextInfoPopup() {
-		if (Helper2.okToUse(fContextInfoPopup))
+		if (isValid(fContextInfoPopup))
 			return;
 
 		Control control= fViewer.getTextWidget();
@@ -279,7 +281,7 @@ class ContextInformationPopup2 implements IContentAssistListener2 {
 	 */
 	private void hideContextInfoPopup() {
 
-		if (Helper2.okToUse(fContextInfoPopup)) {
+		if (isValid(fContextInfoPopup)) {
 
 			int size= fContextFrameStack.size();
 			if (size > 0) {
@@ -314,7 +316,7 @@ class ContextInformationPopup2 implements IContentAssistListener2 {
 	 * at a given offset.
 	 */
 	private void createContextSelector() {
-		if (Helper2.okToUse(fContextSelectorShell))
+		if (isValid(fContextSelectorShell))
 			return;
 
 		Control control= fViewer.getTextWidget();
@@ -383,7 +385,7 @@ class ContextInformationPopup2 implements IContentAssistListener2 {
 	 * @param contexts the possible contexts
 	 */
 	private void setContexts(IContextInformation[] contexts) {
-		if (Helper2.okToUse(fContextSelectorTable)) {
+		if (isValid(fContextSelectorTable)) {
 
 			fContextSelectorInput= contexts;
 
@@ -417,7 +419,7 @@ class ContextInformationPopup2 implements IContentAssistListener2 {
 	 * Hodes the context selector.
 	 */
 	private void hideContextSelector() {
-		if (Helper2.okToUse(fContextSelectorShell)) {
+		if (isValid(fContextSelectorShell)) {
 			fContentAssistant.removeContentAssistListener(this, ContentAssistant2.CONTEXT_SELECTOR);
 
 			fPopupCloser.uninstall();
@@ -426,7 +428,7 @@ class ContextInformationPopup2 implements IContentAssistListener2 {
 			fContextSelectorShell= null;
 		}
 
-		if (!Helper2.okToUse(fContextInfoPopup))
+		if (!isValid(fContextInfoPopup))
 			fContentAssistant.contextInformationClosed();
 	}
 
@@ -436,7 +438,7 @@ class ContextInformationPopup2 implements IContentAssistListener2 {
 	 * @return <code>true</code> if teh context selector has the focus
 	 */
 	public boolean hasFocus() {
-		if (Helper2.okToUse(fContextSelectorShell))
+		if (isValid(fContextSelectorShell))
 			return (fContextSelectorShell.isFocusControl() || fContextSelectorTable.isFocusControl());
 
 		return false;
@@ -457,14 +459,14 @@ class ContextInformationPopup2 implements IContentAssistListener2 {
 	 * @return <code>true</code> if the context selector is active
 	 */
 	public boolean isActive() {
-		return (Helper2.okToUse(fContextInfoPopup) || Helper2.okToUse(fContextSelectorShell));
+		return (isValid(fContextInfoPopup) || isValid(fContextSelectorShell));
 	}
 
 	@Override
 	public boolean verifyKey(VerifyEvent e) {
-		if (Helper2.okToUse(fContextSelectorShell))
+		if (isValid(fContextSelectorShell))
 			return contextSelectorKeyPressed(e);
-		if (Helper2.okToUse(fContextInfoPopup))
+		if (isValid(fContextInfoPopup))
 			return contextInfoPopupKeyPressed(e);
 		return true;
 	}
@@ -573,9 +575,9 @@ class ContextInformationPopup2 implements IContentAssistListener2 {
 
 	@Override
 	public void processEvent(VerifyEvent event) {
-		if (Helper2.okToUse(fContextSelectorShell))
+		if (isValid(fContextSelectorShell))
 			contextSelectorProcessEvent(event);
-		if (Helper2.okToUse(fContextInfoPopup))
+		if (isValid(fContextInfoPopup))
 			contextInfoPopupProcessEvent(event);
 	}
 
@@ -620,7 +622,7 @@ class ContextInformationPopup2 implements IContentAssistListener2 {
 
 			@Override
 			public void run() {
-				if (Helper2.okToUse(fContextInfoPopup) && fFrame == fContextFrameStack.peek()) {
+				if (isValid(fContextInfoPopup) && fFrame == fContextFrameStack.peek()) {
 					int offset= fViewer.getSelectedRange().x;
 					if (fFrame.fValidator == null || !fFrame.fValidator.isContextInformationValid(offset)) {
 						hideContextInfoPopup();
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/Helper2.java b/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/Helper2.java
deleted file mode 100644
index 9b9d89cb1d2..00000000000
--- a/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/Helper2.java
+++ /dev/null
@@ -1,35 +0,0 @@
-/*******************************************************************************
- * Copyright (c) 2000, 2005 IBM Corporation 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:
- *     IBM Corporation - initial API and implementation
- *******************************************************************************/
-package org.eclipse.jface.internal.text.link.contentassist;
-
-
-
-import org.eclipse.swt.widgets.Widget;
-
-
-/**
- * Helper class for testing widget state.
- */
-class Helper2 {
-
-	/**
-	 * Returns whether the widget is <code>null</code> or disposed.
-	 *
-	 * @param widget the widget to check
-	 * @return <code>true</code> if the widget is neither <code>null</code> nor disposed
-	 */
-	public static boolean okToUse(Widget widget) {
-		return (widget != null && !widget.isDisposed());
-	}
-}
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/PopupCloser2.java b/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/PopupCloser2.java
index 1afef85422d..f3e9794cbbc 100644
--- a/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/PopupCloser2.java
+++ b/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/link/contentassist/PopupCloser2.java
@@ -14,6 +14,8 @@
 package org.eclipse.jface.internal.text.link.contentassist;
 
 
+import static org.eclipse.jface.util.Util.isValid;
+
 import org.eclipse.swt.events.FocusEvent;
 import org.eclipse.swt.events.FocusListener;
 import org.eclipse.swt.events.SelectionEvent;
@@ -55,9 +57,9 @@ class PopupCloser2 extends ShellAdapter implements FocusListener, SelectionListe
 	public void install(ContentAssistant2 contentAssistant, Table table) {
 		fContentAssistant= contentAssistant;
 		fTable= table;
-		if (Helper2.okToUse(fTable)) {
+		if (isValid(fTable)) {
 			Shell shell= fTable.getShell();
-			if (Helper2.okToUse(shell)) {
+			if (isValid(shell)) {
 				fShell= shell;
 				fShell.addShellListener(this);
 			}
@@ -73,12 +75,12 @@ class PopupCloser2 extends ShellAdapter implements FocusListener, SelectionListe
 	 */
 	public void uninstall() {
 		fContentAssistant= null;
-		if (Helper2.okToUse(fShell))
+		if (isValid(fShell))
 			fShell.removeShellListener(this);
 		fShell= null;
-		if (Helper2.okToUse(fScrollbar))
+		if (isValid(fScrollbar))
 			fScrollbar.removeSelectionListener(this);
-		if (Helper2.okToUse(fTable))
+		if (isValid(fTable))
 			fTable.removeFocusListener(this);
 	}
 
@@ -101,7 +103,7 @@ class PopupCloser2 extends ShellAdapter implements FocusListener, SelectionListe
 		fScrollbarClicked= false;
 		Display d= fTable.getDisplay();
 		d.asyncExec(() -> {
-			if (Helper2.okToUse(fTable) && !fTable.isFocusControl() && !fScrollbarClicked && fContentAssistant != null)
+			if (isValid(fTable) && !fTable.isFocusControl() && !fScrollbarClicked && fContentAssistant != null)
 				fContentAssistant.popupFocusLost(e);
 		});
 	}
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/AsyncCompletionProposalPopup.java b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/AsyncCompletionProposalPopup.java
index b29c6b2bc06..3383c9fa67e 100644
--- a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/AsyncCompletionProposalPopup.java
+++ b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/AsyncCompletionProposalPopup.java
@@ -13,6 +13,8 @@
  *******************************************************************************/
 package org.eclipse.jface.text.contentassist;
 
+import static org.eclipse.jface.util.Util.isValid;
+
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -154,7 +156,7 @@ class AsyncCompletionProposalPopup extends CompletionProposalPopup {
 
 		final Control control= fContentAssistSubjectControlAdapter.getControl();
 
-		if (!Helper.okToUse(fProposalShell) && control != null && !control.isDisposed()) {
+		if (!isValid(fProposalShell) && control != null && !control.isDisposed()) {
 			// add the listener before computing the proposals so we don't move the caret
 			// when the user types fast.
 			fContentAssistSubjectControlAdapter.addKeyListener(fKeyListener);
@@ -243,7 +245,7 @@ class AsyncCompletionProposalPopup extends CompletionProposalPopup {
 								&& fComputedProposals.size() == 1
 								&& remaining.get() == 0
 								&& canAutoInsert(fComputedProposals.get(0))) {
-							if (Helper.okToUse(fProposalShell)) {
+							if (isValid(fProposalShell)) {
 								insertProposal(fComputedProposals.get(0), (char) 0, 0, offset);
 								hide();
 							}
@@ -268,7 +270,7 @@ class AsyncCompletionProposalPopup extends CompletionProposalPopup {
 	@Override
 	public String incrementalComplete() {
 		cancelFutures();
-		if (Helper.okToUse(fProposalShell) && fFilteredProposals != null) {
+		if (isValid(fProposalShell) && fFilteredProposals != null) {
 			return super.incrementalComplete();
 		}
 		final Control control= fContentAssistSubjectControlAdapter.getControl();
@@ -276,7 +278,7 @@ class AsyncCompletionProposalPopup extends CompletionProposalPopup {
 		if (fKeyListener == null)
 			fKeyListener= new ProposalSelectionListener();
 
-		if (!Helper.okToUse(fProposalShell) && !control.isDisposed())
+		if (!isValid(fProposalShell) && !control.isDisposed())
 			fContentAssistSubjectControlAdapter.addKeyListener(fKeyListener);
 
 		fInvocationOffset= fContentAssistSubjectControlAdapter.getSelectedRange().x;
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/CompletionProposalPopup.java b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/CompletionProposalPopup.java
index 0c128250a3d..128c97ae5d6 100644
--- a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/CompletionProposalPopup.java
+++ b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/CompletionProposalPopup.java
@@ -18,6 +18,8 @@
  *******************************************************************************/
 package org.eclipse.jface.text.contentassist;
 
+import static org.eclipse.jface.util.Util.isValid;
+
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -226,7 +228,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 	final class ProposalSelectionListener implements KeyListener {
 		@Override
 		public void keyPressed(KeyEvent e) {
-			if (!Helper.okToUse(fProposalShell))
+			if (!isValid(fProposalShell))
 				return;
 
 			if (e.character == 0 && e.keyCode == SWT.CTRL) {
@@ -239,7 +241,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 
 		@Override
 		public void keyReleased(KeyEvent e) {
-			if (!Helper.okToUse(fProposalShell))
+			if (!isValid(fProposalShell))
 				return;
 
 			if (e.character == 0 && e.keyCode == SWT.CTRL) {
@@ -260,7 +262,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 
 		@Override
 		public void keyPressed(KeyEvent e) {
-			if (!Helper.okToUse(fProposalShell))
+			if (!isValid(fProposalShell))
 				return;
 
 			int accelerator= SWTKeySupport.convertEventToUnmodifiedAccelerator(e);
@@ -351,7 +353,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 			if (!fIsFilterPending.compareAndSet(true, false))
 				return;
 
-			if (!Helper.okToUse(fContentAssistSubjectControlAdapter.getControl()))
+			if (!isValid(fContentAssistSubjectControlAdapter.getControl()))
 				return;
 
 			int offset= fContentAssistSubjectControlAdapter.getSelectedRange().x;
@@ -490,7 +492,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 
 		final Control control= fContentAssistSubjectControlAdapter.getControl();
 
-		if (!Helper.okToUse(fProposalShell) && control != null && !control.isDisposed()) {
+		if (!isValid(fProposalShell) && control != null && !control.isDisposed()) {
 			// add the listener before computing the proposals so we don't move the caret
 			// when the user types fast.
 			fContentAssistSubjectControlAdapter.addKeyListener(fKeyListener);
@@ -596,7 +598,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 	 * Creates the proposal selector.
 	 */
 	void createProposalSelector() {
-		if (Helper.okToUse(fProposalShell))
+		if (isValid(fProposalShell))
 			return;
 
 		Control control= fContentAssistSubjectControlAdapter.getControl();
@@ -712,12 +714,12 @@ class CompletionProposalPopup implements IContentAssistListener {
 	 */
 	int getMinimalHeight() {
 		int height= 0;
-		if (Helper.okToUse(fProposalTable)) {
+		if (isValid(fProposalTable)) {
 			int items= fProposalTable.getItemHeight() * 10;
 			Rectangle trim= fProposalTable.computeTrim(0, 0, SWT.DEFAULT, items);
 			height= trim.height;
 		}
-		if (Helper.okToUse(fMessageText))
+		if (isValid(fMessageText))
 			height+= fMessageText.getSize().y + 1;
 		return height;
 	}
@@ -735,7 +737,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 				private CommandKeyListener fCommandKeyListener;
 				@Override
 				public void focusGained(FocusEvent e) {
-					if (Helper.okToUse(control)) {
+					if (isValid(control)) {
 						if (fCommandKeyListener == null) {
 							fCommandKeyListener= new CommandKeyListener(commandSequence);
 							fProposalTable.addKeyListener(fCommandKeyListener);
@@ -756,7 +758,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 				private TraverseListener fTraverseListener;
 				@Override
 				public void focusGained(FocusEvent e) {
-					if (Helper.okToUse(control)) {
+					if (isValid(control)) {
 						if (fTraverseListener == null) {
 							fTraverseListener= event -> {
 								if (event.detail == SWT.TRAVERSE_TAB_NEXT) {
@@ -865,7 +867,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 			StyleRange[] styleRanges= null;
 			Image image= null;
 			try {
-				if (fIsColoredLabelsSupportEnabled && current instanceof ICompletionProposalExtension7 && Helper.okToUse(fProposalShell)) {
+				if (fIsColoredLabelsSupportEnabled && current instanceof ICompletionProposalExtension7 && isValid(fProposalShell)) {
 					BoldStylerProvider boldStylerProvider= fContentAssistant.getBoldStylerProvider();
 					if (boldStylerProvider == null) {
 						boldStylerProvider= new BoldStylerProvider(fProposalShell.getFont());
@@ -922,7 +924,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 			fFilterRunnable.run();
 
 		// filter runnable may have hidden the proposals
-		if (!Helper.okToUse(fProposalTable))
+		if (!isValid(fProposalTable))
 			return null;
 
 		int i= fProposalTable.getSelectionIndex();
@@ -1043,7 +1045,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 	 * @return <code>true</code> if the popup has the focus
 	 */
 	public boolean hasFocus() {
-		if (Helper.okToUse(fProposalShell)) {
+		if (isValid(fProposalShell)) {
 			if ((fProposalShell.getDisplay().getActiveShell() == fProposalShell))
 				return true;
 			/*
@@ -1080,7 +1082,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 			registry.unregister(fFocusHelper);
 		}
 
-		if (Helper.okToUse(fProposalShell)) {
+		if (isValid(fProposalShell)) {
 
 			fContentAssistant.removeContentAssistListener(this, ContentAssistant.PROPOSAL_SELECTOR);
 
@@ -1163,7 +1165,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 		if (oldProposals != fFilteredProposals) // reentrant call was first - abort
 			return;
 
-		if (Helper.okToUse(fProposalTable)) {
+		if (isValid(fProposalTable)) {
 			if (oldProposal instanceof ICompletionProposalExtension2 && fViewer != null)
 				((ICompletionProposalExtension2) oldProposal).unselected(fViewer);
 
@@ -1220,7 +1222,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 	 */
 	void displayProposals() {
 
-		if (!Helper.okToUse(fProposalShell) ||  !Helper.okToUse(fProposalTable))
+		if (!isValid(fProposalShell) || !isValid(fProposalTable))
 			return;
 
 		if (fContentAssistant.addContentAssistListener(this, ContentAssistant.PROPOSAL_SELECTOR)) {
@@ -1257,10 +1259,10 @@ class CompletionProposalPopup implements IContentAssistListener {
 			 */
 			fProposalShell.setVisible(true); // may run event loop on GTK
 			// transfer focus since no verify key listener can be attached
-			if (!fContentAssistSubjectControlAdapter.supportsVerifyKeyListener() && Helper.okToUse(fProposalShell))
+			if (!fContentAssistSubjectControlAdapter.supportsVerifyKeyListener() && isValid(fProposalShell))
 				fProposalShell.setFocus(); // may run event loop on GTK ??
 
-			if (fAdditionalInfoController != null && Helper.okToUse(fProposalTable)) {
+			if (fAdditionalInfoController != null && isValid(fProposalTable)) {
 				fAdditionalInfoController.install(fProposalTable);
 				fAdditionalInfoController.handleTableSelectionChanged();
 			}
@@ -1296,7 +1298,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 
 	@Override
 	public boolean verifyKey(VerifyEvent e) {
-		if (!Helper.okToUse(fProposalShell))
+		if (!isValid(fProposalShell))
 			return true;
 
 		char key= e.character;
@@ -1563,7 +1565,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 	 * @since 3.0
 	 */
 	public void setFocus() {
-		if (Helper.okToUse(fProposalShell)) {
+		if (isValid(fProposalShell)) {
 			fProposalShell.setFocus();
 		}
 	}
@@ -1596,7 +1598,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 	 * @since 3.0
 	 */
 	public String incrementalComplete() {
-		if (Helper.okToUse(fProposalShell) && fFilteredProposals != null) {
+		if (isValid(fProposalShell) && fFilteredProposals != null) {
 			if (fLastCompletionOffset == fFilterOffset) {
 				handleRepeatedInvocation();
 			} else {
@@ -1609,7 +1611,7 @@ class CompletionProposalPopup implements IContentAssistListener {
 			if (fKeyListener == null)
 				fKeyListener= new ProposalSelectionListener();
 
-			if (!Helper.okToUse(fProposalShell) && !control.isDisposed())
+			if (!isValid(fProposalShell) && !control.isDisposed())
 				fContentAssistSubjectControlAdapter.addKeyListener(fKeyListener);
 
 			BusyIndicator.showWhile(control.getDisplay(), () -> {
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistSubjectControlAdapter.java b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistSubjectControlAdapter.java
index 56d7e1de8d4..e1f6e72de5a 100644
--- a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistSubjectControlAdapter.java
+++ b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistSubjectControlAdapter.java
@@ -15,6 +15,8 @@
  *******************************************************************************/
 package org.eclipse.jface.text.contentassist;
 
+import static org.eclipse.jface.util.Util.isValid;
+
 import org.eclipse.swt.custom.StyledText;
 import org.eclipse.swt.custom.VerifyKeyListener;
 import org.eclipse.swt.events.KeyListener;
@@ -166,7 +168,7 @@ class ContentAssistSubjectControlAdapter implements IContentAssistSubjectControl
 		} else {
 
 			StyledText textWidget= fViewer.getTextWidget();
-			if (Helper.okToUse(textWidget)) {
+			if (isValid(textWidget)) {
 				textWidget.addVerifyKeyListener(verifyKeyListener);
 				return true;
 			}
@@ -184,7 +186,7 @@ class ContentAssistSubjectControlAdapter implements IContentAssistSubjectControl
 			return true;
 		} else {
 			StyledText textWidget= fViewer.getTextWidget();
-			if (Helper.okToUse(textWidget)) {
+			if (isValid(textWidget)) {
 				textWidget.addVerifyKeyListener(verifyKeyListener);
 				return true;
 			}
@@ -201,7 +203,7 @@ class ContentAssistSubjectControlAdapter implements IContentAssistSubjectControl
 			extension.removeVerifyKeyListener(verifyKeyListener);
 		} else {
 			StyledText textWidget= fViewer.getTextWidget();
-			if (Helper.okToUse(textWidget))
+			if (isValid(textWidget))
 				textWidget.removeVerifyKeyListener(verifyKeyListener);
 		}
 	}
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistant.java b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistant.java
index 4da58e27542..e88c8f03422 100644
--- a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistant.java
+++ b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContentAssistant.java
@@ -18,6 +18,8 @@
  *******************************************************************************/
 package org.eclipse.jface.text.contentassist;
 
+import static org.eclipse.jface.util.Util.isValid;
+
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -133,7 +135,7 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 		protected void install() {
 			Control control= fContentAssistSubjectControlAdapter.getControl();
 			fControl= control;
-			if (Helper.okToUse(control)) {
+			if (isValid(control)) {
 
 				Shell shell= control.getShell();
 				fShell= shell;
@@ -158,12 +160,12 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 		protected void uninstall() {
 			Control shell= fShell;
 			fShell= null;
-			if (Helper.okToUse(shell))
+			if (isValid(shell))
 				shell.removeControlListener(this);
 
 			Control control= fControl;
 			fControl= null;
-			if (Helper.okToUse(control)) {
+			if (isValid(control)) {
 
 				control.removeMouseListener(this);
 				control.removeFocusListener(this);
@@ -210,7 +212,7 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 		@Override
 		public void focusLost(FocusEvent e) {
 			Control control= fControl;
-			if (Helper.okToUse(control)) {
+			if (isValid(control)) {
 				Display d= control.getDisplay();
 				if (d != null) {
 					d.asyncExec(() -> {
@@ -444,14 +446,14 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 			switch (type) {
 				case LAYOUT_PROPOSAL_SELECTOR:
 					if (fContextType == LAYOUT_CONTEXT_SELECTOR &&
-							Helper.okToUse(fShells[LAYOUT_CONTEXT_SELECTOR])) {
+							isValid(fShells[LAYOUT_CONTEXT_SELECTOR])) {
 						// Restore event notification to the tip popup.
 						addContentAssistListener((IContentAssistListener) fPopups[LAYOUT_CONTEXT_SELECTOR], CONTEXT_SELECTOR);
 					}
 					break;
 
 				case LAYOUT_CONTEXT_SELECTOR:
-					if (Helper.okToUse(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
+					if (isValid(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
 						if (fProposalPopupOrientation == PROPOSAL_STACKED)
 							layout(LAYOUT_PROPOSAL_SELECTOR, getSelectionOffset());
 						// Restore event notification to the proposal popup.
@@ -461,7 +463,7 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 					break;
 
 				case LAYOUT_CONTEXT_INFO_POPUP:
-					if (Helper.okToUse(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
+					if (isValid(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
 						if (fContextInfoPopupOrientation == CONTEXT_INFO_BELOW)
 							layout(LAYOUT_PROPOSAL_SELECTOR, getSelectionOffset());
 					}
@@ -501,13 +503,13 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 		protected void layoutProposalSelector(int offset) {
 			if (fContextType == LAYOUT_CONTEXT_INFO_POPUP &&
 					fContextInfoPopupOrientation == CONTEXT_INFO_BELOW &&
-					Helper.okToUse(fShells[LAYOUT_CONTEXT_INFO_POPUP])) {
+					isValid(fShells[LAYOUT_CONTEXT_INFO_POPUP])) {
 				// Stack proposal selector beneath the tip box.
 				Shell shell= fShells[LAYOUT_PROPOSAL_SELECTOR];
 				Shell parent= fShells[LAYOUT_CONTEXT_INFO_POPUP];
 				shell.setLocation(getStackedLocation(shell, parent));
 			} else if (fContextType != LAYOUT_CONTEXT_SELECTOR ||
-						!Helper.okToUse(fShells[LAYOUT_CONTEXT_SELECTOR])) {
+					!isValid(fShells[LAYOUT_CONTEXT_SELECTOR])) {
 				// There are no other presentations to be concerned with,
 				// so place the proposal selector beneath the cursor line.
 				Shell shell= fShells[LAYOUT_PROPOSAL_SELECTOR];
@@ -546,7 +548,7 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 			Shell shell= fShells[LAYOUT_CONTEXT_SELECTOR];
 			shell.setBounds(computeBoundsBelowAbove(shell, shell.getSize(), offset, null));
 
-			if (Helper.okToUse(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
+			if (isValid(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
 				switch (fProposalPopupOrientation) {
 					case PROPOSAL_REMOVE:
 						// Remove the proposal selector.
@@ -580,7 +582,7 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 					// Place the popup beneath the cursor line.
 					Shell parent= fShells[LAYOUT_CONTEXT_INFO_POPUP];
 					parent.setBounds(computeBoundsBelowAbove(parent, parent.getSize(), offset, null));
-					if (Helper.okToUse(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
+					if (isValid(fShells[LAYOUT_PROPOSAL_SELECTOR])) {
 						// Stack the proposal selector beneath the context info popup.
 						Shell shell= fShells[LAYOUT_PROPOSAL_SELECTOR];
 						shell.setLocation(getStackedLocation(shell, parent));
@@ -739,12 +741,12 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 			switch (type) {
 				case LAYOUT_PROPOSAL_SELECTOR:
 					if (fContextType == LAYOUT_CONTEXT_SELECTOR &&
-							Helper.okToUse(fShells[LAYOUT_CONTEXT_SELECTOR]))
+							isValid(fShells[LAYOUT_CONTEXT_SELECTOR]))
 						// Disable event notification to the tip selector.
 						removeContentAssistListener((IContentAssistListener) fPopups[LAYOUT_CONTEXT_SELECTOR], CONTEXT_SELECTOR);
 					break;
 				case LAYOUT_CONTEXT_SELECTOR:
-					if (Helper.okToUse(fShells[LAYOUT_PROPOSAL_SELECTOR]))
+					if (isValid(fShells[LAYOUT_PROPOSAL_SELECTOR]))
 						// Disable event notification to the proposal selector.
 						removeContentAssistListener((IContentAssistListener) fPopups[LAYOUT_PROPOSAL_SELECTOR], PROPOSAL_SELECTOR);
 					break;
@@ -1541,7 +1543,7 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 		registerHandler(SELECT_NEXT_PROPOSAL_COMMAND_ID, fProposalPopup.createProposalSelectionHandler(CompletionProposalPopup.ProposalSelectionHandler.SELECT_NEXT));
 		registerHandler(SELECT_PREVIOUS_PROPOSAL_COMMAND_ID, fProposalPopup.createProposalSelectionHandler(CompletionProposalPopup.ProposalSelectionHandler.SELECT_PREVIOUS));
 
-		if (Helper.okToUse(fContentAssistSubjectControlAdapter.getControl())) {
+		if (isValid(fContentAssistSubjectControlAdapter.getControl())) {
 			fContentAssistSubjectControlShell= fContentAssistSubjectControlAdapter.getControl().getShell();
 			fCASCSTraverseListener= e -> {
 				if (e.detail == SWT.TRAVERSE_ESCAPE && isProposalPopupActive())
@@ -1577,7 +1579,7 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 			fCloser= null;
 		}
 
-		if (Helper.okToUse(fContentAssistSubjectControlShell))
+		if (isValid(fContentAssistSubjectControlShell))
 			fContentAssistSubjectControlShell.removeTraverseListener(fCASCSTraverseListener);
 		fCASCSTraverseListener= null;
 		fContentAssistSubjectControlShell= null;
@@ -1730,7 +1732,7 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 	 */
 	private void installKeyListener() {
 		if (!fVerifyKeyListenerHooked) {
-			if (Helper.okToUse(fContentAssistSubjectControlAdapter.getControl())) {
+			if (isValid(fContentAssistSubjectControlAdapter.getControl())) {
 				fVerifyKeyListenerHooked= fContentAssistSubjectControlAdapter.prependVerifyKeyListener(fInternalListener);
 			}
 		}
@@ -1792,7 +1794,7 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 	 */
 	private void uninstallVerifyKeyListener() {
 		if (fVerifyKeyListenerHooked) {
-			if (Helper.okToUse(fContentAssistSubjectControlAdapter.getControl()))
+			if (isValid(fContentAssistSubjectControlAdapter.getControl()))
 				fContentAssistSubjectControlAdapter.removeVerifyKeyListener(fInternalListener);
 			fVerifyKeyListenerHooked= false;
 		}
@@ -2396,7 +2398,7 @@ public class ContentAssistant implements IContentAssistant, IContentAssistantExt
 			return null;
 
 		Rectangle maxBounds= null;
-		if (fContentAssistSubjectControl != null && Helper.okToUse(fContentAssistSubjectControl.getControl()))
+		if (fContentAssistSubjectControl != null && isValid(fContentAssistSubjectControl.getControl()))
 			maxBounds= fContentAssistSubjectControl.getControl().getDisplay().getBounds();
 		else {
 			// fallback
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContextInformationPopup.java b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContextInformationPopup.java
index 7bf6d32af33..e9d90400718 100644
--- a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContextInformationPopup.java
+++ b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/ContextInformationPopup.java
@@ -15,6 +15,8 @@
  *******************************************************************************/
 package org.eclipse.jface.text.contentassist;
 
+import static org.eclipse.jface.util.Util.isValid;
+
 import java.util.Stack;
 
 import org.eclipse.swt.SWT;
@@ -412,7 +414,7 @@ class ContextInformationPopup implements IContentAssistListener {
 	 * Creates the context information popup. This is the tool tip like overlay window.
 	 */
 	private void createContextInfoPopup() {
-		if (Helper.okToUse(fContextInfoPopup))
+		if (isValid(fContextInfoPopup))
 			return;
 
 		Control control= fContentAssistSubjectControlAdapter.getControl();
@@ -467,7 +469,7 @@ class ContextInformationPopup implements IContentAssistListener {
 	 */
 	private void hideContextInfoPopup(boolean all) {
 
-		if (Helper.okToUse(fContextInfoPopup)) {
+		if (isValid(fContextInfoPopup)) {
 
 			int size= fContextFrameStack.size();
 			while (size > 0) {
@@ -508,7 +510,7 @@ class ContextInformationPopup implements IContentAssistListener {
 	 * at a given offset.
 	 */
 	private void createContextSelector() {
-		if (Helper.okToUse(fContextSelectorShell))
+		if (isValid(fContextSelectorShell))
 			return;
 
 		Control control= fContentAssistSubjectControlAdapter.getControl();
@@ -599,7 +601,7 @@ class ContextInformationPopup implements IContentAssistListener {
 	 */
 	int getMinimalHeight() {
 		int height= 0;
-		if (Helper.okToUse(fContextSelectorTable)) {
+		if (isValid(fContextSelectorTable)) {
 			int items= fContextSelectorTable.getItemHeight() * 10;
 			Rectangle trim= fContextSelectorTable.computeTrim(0, 0, SWT.DEFAULT, items);
 			height= trim.height;
@@ -638,7 +640,7 @@ class ContextInformationPopup implements IContentAssistListener {
 	 * @param selectionIndex the index of the proposal to select
 	 */
 	private void setContexts(IContextInformation[] contexts, int selectionIndex) {
-		if (Helper.okToUse(fContextSelectorTable)) {
+		if (isValid(fContextSelectorTable)) {
 
 			fContextSelectorInput= contexts;
 
@@ -672,7 +674,7 @@ class ContextInformationPopup implements IContentAssistListener {
 	 * Hides the context selector.
 	 */
 	private void hideContextSelector() {
-		if (Helper.okToUse(fContextSelectorShell)) {
+		if (isValid(fContextSelectorShell)) {
 			fContentAssistant.storeContextSelectorPopupSize();
 			fContentAssistant.removeContentAssistListener(this, ContentAssistant.CONTEXT_SELECTOR);
 
@@ -682,7 +684,7 @@ class ContextInformationPopup implements IContentAssistListener {
 			fContextSelectorShell= null;
 		}
 
-		if (!Helper.okToUse(fContextInfoPopup))
+		if (!isValid(fContextInfoPopup))
 			fContentAssistant.contextInformationClosed();
 	}
 
@@ -692,7 +694,7 @@ class ContextInformationPopup implements IContentAssistListener {
 	 * @return <code>true</code> if the context selector has the focus
 	 */
 	public boolean hasFocus() {
-		if (Helper.okToUse(fContextSelectorShell))
+		if (isValid(fContextSelectorShell))
 			return fContextSelectorShell.getDisplay().getActiveShell() == fContextSelectorShell;
 
 		return false;
@@ -713,14 +715,14 @@ class ContextInformationPopup implements IContentAssistListener {
 	 * @return <code>true</code> if the context selector is active
 	 */
 	public boolean isActive() {
-		return (Helper.okToUse(fContextInfoPopup) || Helper.okToUse(fContextSelectorShell));
+		return (isValid(fContextInfoPopup) || isValid(fContextSelectorShell));
 	}
 
 	@Override
 	public boolean verifyKey(VerifyEvent e) {
-		if (Helper.okToUse(fContextSelectorShell))
+		if (isValid(fContextSelectorShell))
 			return contextSelectorKeyPressed(e);
-		if (Helper.okToUse(fContextInfoPopup))
+		if (isValid(fContextInfoPopup))
 			return contextInfoPopupKeyPressed(e);
 		return true;
 	}
@@ -831,9 +833,9 @@ class ContextInformationPopup implements IContentAssistListener {
 
 	@Override
 	public void processEvent(VerifyEvent event) {
-		if (Helper.okToUse(fContextSelectorShell))
+		if (isValid(fContextSelectorShell))
 			contextSelectorProcessEvent(event);
-		if (Helper.okToUse(fContextInfoPopup))
+		if (isValid(fContextInfoPopup))
 			contextInfoPopupProcessEvent(event);
 	}
 
@@ -872,7 +874,7 @@ class ContextInformationPopup implements IContentAssistListener {
 		 * Otherwise, we'd validate the context information based on the
 		 * pre-key-stroke state.
 		 */
-		if (!Helper.okToUse(fContextInfoPopup))
+		if (!isValid(fContextInfoPopup))
 			return;
 
 		fContextInfoPopup.getDisplay().asyncExec(new Runnable() {
@@ -886,7 +888,7 @@ class ContextInformationPopup implements IContentAssistListener {
 					int offset= fContentAssistSubjectControlAdapter.getSelectedRange().x;
 
 					// iterate all contexts on the stack
-					while (Helper.okToUse(fContextInfoPopup) && !fContextFrameStack.isEmpty()) {
+					while (isValid(fContextInfoPopup) && !fContextFrameStack.isEmpty()) {
 						ContextFrame top= fContextFrameStack.peek();
 						if (top.fValidator == null || !top.fValidator.isContextInformationValid(offset)) {
 							hideContextInfoPopup(false); // loop variant: reduces the number of contexts on the stack
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/Helper.java b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/Helper.java
deleted file mode 100644
index 9eb7bbcf854..00000000000
--- a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/Helper.java
+++ /dev/null
@@ -1,33 +0,0 @@
-/*******************************************************************************
- * Copyright (c) 2000, 2005 IBM Corporation 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:
- *     IBM Corporation - initial API and implementation
- *******************************************************************************/
-package org.eclipse.jface.text.contentassist;
-
-import org.eclipse.swt.widgets.Widget;
-
-
-/**
- * Helper class for testing widget state.
- */
-class Helper {
-
-	/**
-	 * Returns whether the widget is <code>null</code> or disposed.
-	 *
-	 * @param widget the widget to check
-	 * @return <code>true</code> if the widget is neither <code>null</code> nor disposed
-	 */
-	public static boolean okToUse(Widget widget) {
-		return (widget != null && !widget.isDisposed());
-	}
-}
diff --git a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/PopupCloser.java b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/PopupCloser.java
index 46a9790be1f..9aba5cea763 100644
--- a/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/PopupCloser.java
+++ b/org.eclipse.jface.text/src/org/eclipse/jface/text/contentassist/PopupCloser.java
@@ -13,6 +13,8 @@
  *******************************************************************************/
 package org.eclipse.jface.text.contentassist;
 
+import static org.eclipse.jface.util.Util.isValid;
+
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.events.FocusEvent;
 import org.eclipse.swt.events.FocusListener;
@@ -92,7 +94,7 @@ class PopupCloser extends ShellAdapter implements FocusListener, SelectionListen
 		fTable= table;
 		fAdditionalInfoController= additionalInfoController;
 
-		if (Helper.okToUse(fTable)) {
+		if (isValid(fTable)) {
 			fShell= fTable.getShell();
 			fDisplay= fShell.getDisplay();
 
@@ -115,12 +117,12 @@ class PopupCloser extends ShellAdapter implements FocusListener, SelectionListen
 	 */
 	public void uninstall() {
 		fContentAssistant= null;
-		if (Helper.okToUse(fShell))
+		if (isValid(fShell))
 			fShell.removeShellListener(this);
 		fShell= null;
-		if (Helper.okToUse(fScrollbar))
+		if (isValid(fScrollbar))
 			fScrollbar.removeSelectionListener(this);
-		if (Helper.okToUse(fTable))
+		if (isValid(fTable))
 			fTable.removeFocusListener(this);
 		if (fDisplay != null && ! fDisplay.isDisposed()) {
 			fDisplay.removeFilter(SWT.Activate, this);
@@ -150,7 +152,7 @@ class PopupCloser extends ShellAdapter implements FocusListener, SelectionListen
 		fScrollbarClicked= false;
 		Display d= fTable.getDisplay();
 		d.asyncExec(() -> {
-			if (Helper.okToUse(fTable) && !fTable.isFocusControl() && !fScrollbarClicked && fContentAssistant != null)
+			if (isValid(fTable) && !fTable.isFocusControl() && !fScrollbarClicked && fContentAssistant != null)
 				fContentAssistant.popupFocusLost(e);
 		});
 	}