TextViewer: use Throttler for firePostSelectionChanged #1695

Avoids a 500ms delay after changing the selection, like higlighting the
selected word.

#1695

bundles/org.eclipse.jface.text/src/org/eclipse/jface/text/TextViewer.java

@@ -17,6 +17,7 @@
  *******************************************************************************/
 package org.eclipse.jface.text;
 
+import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
@@ -73,6 +74,7 @@
 import org.eclipse.jface.internal.text.StickyHoverManager;
 import org.eclipse.jface.util.Geometry;
 import org.eclipse.jface.util.OpenStrategy;
+import org.eclipse.jface.util.Throttler;
 import org.eclipse.jface.viewers.IPostSelectionProvider;
 import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.jface.viewers.ISelectionChangedListener;
@@ -1456,6 +1458,7 @@ public void documentRewriteSessionChanged(DocumentRewriteSessionEvent event) {
 
 	/** The viewer's text widget */
 	private StyledText fTextWidget;
+	private Throttler throttledPostSelection;
 	/** The viewer's input document */
 	private IDocument fDocument;
 	/** The viewer's visible document */
@@ -1716,7 +1719,7 @@ protected IDocumentAdapter createDocumentAdapter() {
 	 * @param styles the SWT style bits for the viewer's control
 	 */
 	protected void createControl(Composite parent, int styles) {
-
+		throttledPostSelection= new Throttler(parent.getDisplay(), Duration.ofMillis(getEmptySelectionChangedEventDelay()), this::postSelectionChanged);
 		fTextWidget= createTextWidget(parent, styles);
 
 		// Support scroll page upon MOD1+MouseWheel
@@ -2613,26 +2616,22 @@ private void queuePostSelectionChanged(final boolean fireEqualSelection) {
 
 		fNumberOfPostSelectionChangedEvents[0]++;
 		fFireEqualPostSelectionChange|= fireEqualSelection;
-		display.timerExec(getEmptySelectionChangedEventDelay(), new Runnable() {
-			final int id= fNumberOfPostSelectionChangedEvents[0];
-			@Override
-			public void run() {
-				if (id == fNumberOfPostSelectionChangedEvents[0]) {
-					// Check again because this is executed after the delay
-					if (getDisplay() != null)  {
-						Point selection= fTextWidget.getSelectionRange();
-						if (selection != null) {
-							IRegion r= widgetRange2ModelRange(new Region(selection.x, selection.y));
-							if (fFireEqualPostSelectionChange || (r != null && !r.equals(fLastSentPostSelectionChange)) || r == null)  {
-								fLastSentPostSelectionChange= r;
-								fFireEqualPostSelectionChange= false;
-								firePostSelectionChanged(selection.x, selection.y);
-							}
-						}
-					}
-				}
+		throttledPostSelection.throttledExec();
+	}
+
+	private void postSelectionChanged() {
+		if (fTextWidget == null || fTextWidget.isDisposed()) {
+			return;
+		}
+		Point selection= fTextWidget.getSelectionRange();
+		if (selection != null) {
+			IRegion r= widgetRange2ModelRange(new Region(selection.x, selection.y));
+			if (fFireEqualPostSelectionChange || (r != null && !r.equals(fLastSentPostSelectionChange)) || r == null) {
+				fLastSentPostSelectionChange= r;
+				fFireEqualPostSelectionChange= false;
+				firePostSelectionChanged(selection.x, selection.y);
 			}
-		});
+		}
 	}
 
 	/**

tests/org.eclipse.ui.tests/Eclipse UI Tests/org/eclipse/ui/tests/multipageeditor/MultiVariablePageTest.java

@@ -155,9 +155,9 @@ public void testPostSelection() throws Throwable {
 		try {
 			postProvider.addPostSelectionChangedListener(listener);
 			editor.setPage(1);
-			assertEquals(1, fPostCalled);
-			editor.setPage(0);
 			assertEquals(2, fPostCalled);
+			editor.setPage(0);
+			assertEquals(3, fPostCalled);
 		} finally {
 			postProvider.removePostSelectionChangedListener(listener);
 		}