Fix flaky AsyncContentAssistTest.testCompleteActivationChar

Replace Display.post() with control.notifyListeners() for reliable
event delivery in headless CI environments. Display.post() sends
native OS events that may not be processed, causing the content
assist popup to never appear.

Also fix race condition by capturing beforeShells before posting
key events, process events after shell.open(), and increase
findNewShell timeout from 1s to 5s for slower CI environments.

Fixes #890

Author: vogella

tests/org.eclipse.jface.text.tests/src/org/eclipse/jface/text/tests/contentassist/AbstractContentAssistTest.java

@@ -229,7 +229,7 @@ protected static List<Shell> findNewShells(Collection<Shell> beforeShells) {
 
 	protected static Shell findNewShell(Collection<Shell> beforeShells) {
 		List<Shell> afterShells= findNewShells(beforeShells);
-		for (int attempt= 0; afterShells.size() != 1 && attempt < 10; attempt++) {
+		for (int attempt= 0; afterShells.size() != 1 && attempt < 50; attempt++) {
 			DisplayHelper.sleep(getDisplay(), 100);
 			afterShells= findNewShells(beforeShells);
 		}

tests/org.eclipse.jface.text.tests/src/org/eclipse/jface/text/tests/contentassist/AsyncContentAssistTest.java

@@ -17,7 +17,6 @@
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
-import static org.junit.jupiter.api.Assumptions.assumeFalse;
 
 import java.util.Arrays;
 import java.util.Collection;
@@ -41,8 +40,6 @@
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.Platform;
 
-import org.eclipse.jface.util.Util;
-
 import org.eclipse.jface.text.Document;
 import org.eclipse.jface.text.IDocument;
 import org.eclipse.jface.text.contentassist.ContentAssistant;
@@ -134,7 +131,6 @@ protected boolean condition() {
 
 	@Test
 	public void testCompleteActivationChar() {
-		assumeFalse(Util.isWindows(), "test fails on Windows, see https://github.com/eclipse-platform/eclipse.platform.ui/issues/890");
 		shell.setLayout(new FillLayout());
 		shell.setSize(500, 300);
 		SourceViewer viewer= new SourceViewer(shell, null, SWT.NONE);
@@ -151,17 +147,20 @@ public void testCompleteActivationChar() {
 		contentAssistant.install(viewer);
 		shell.open();
 		Display display= shell.getDisplay();
-		Event keyEvent= new Event();
+		DisplayHelper.runEventLoop(display, 0);
 		Control control= viewer.getTextWidget();
+		control.forceFocus();
+		DisplayHelper.runEventLoop(display, 0);
+		final Collection<Shell> beforeShells= AbstractContentAssistTest.getCurrentShells();
+		// Use notifyListeners instead of Display.post() for reliable event delivery
+		// Display.post() sends native OS events that may not be processed reliably
+		// in headless CI environments
+		Event keyEvent= new Event();
 		keyEvent.widget= control;
 		keyEvent.type= SWT.KeyDown;
 		keyEvent.character= 'b';
 		keyEvent.keyCode= 'b';
-		control.getShell().forceActive();
-		control.getDisplay().post(keyEvent);
-		keyEvent.type= SWT.KeyUp;
-		control.getDisplay().post(keyEvent);
-		final Collection<Shell> beforeShells= AbstractContentAssistTest.getCurrentShells();
+		control.notifyListeners(SWT.KeyDown, keyEvent);
 		AbstractContentAssistTest.processEvents();
 		Shell newShell= AbstractContentAssistTest.findNewShell(beforeShells);
 		assertTrue(new DisplayHelper() {