Fix "no more handles" exception during Edge browser creation #339

The Edge browser creation uses Display.readAndDispath() to process the
OS events for browser instantiation. When there are other asynchronous
executions scheduled while the browser is being initialized, they may be
processed in between the processing of browser-instantiating OS events
if too much time elapses between them. In case such an asynchronous
execution changes a state that makes the browser instantiation fail,
such as disposing the composite parent of the browser, an exception
occurs.

In order to avoid the processing of asynchronous executions during
browser instantiation, the change ensures that readAndDisplay() is only
called when an OS event is present to be processed.

Author: HeikoKlare

bundles/org.eclipse.swt/Eclipse SWT Browser/win32/org/eclipse/swt/browser/Edge.java

@@ -222,9 +222,8 @@ static int callAndWait(long[] ppv, ToIntFunction<IUnknown> callable) {
 	ppv[0] = 0;
 	phr[0] = callable.applyAsInt(completion);
 	completion.Release();
-	Display display = Display.getCurrent();
 	while (phr[0] == COM.S_OK && ppv[0] == 0) {
-		if (!display.readAndDispatch()) display.sleep();
+		processNextOSMessage();
 	}
 	return phr[0];
 }
@@ -241,13 +240,33 @@ static int callAndWait(String[] pstr, ToIntFunction<IUnknown> callable) {
 	pstr[0] = null;
 	phr[0] = callable.applyAsInt(completion);
 	completion.Release();
-	Display display = Display.getCurrent();
 	while (phr[0] == COM.S_OK && pstr[0] == null) {
-		if (!display.readAndDispatch()) display.sleep();
+		processNextOSMessage();
 	}
 	return phr[0];
 }
 
+/**
+ * Processes a single OS message using {@link Display#readAndDispatch()}. This
+ * is required for processing the OS events during browser initialization, since
+ * Edge browser initialization happens asynchronously.
+ * <p>
+ * {@link Display#readAndDisplay()} also processes events scheduled for
+ * asynchronous execution via {@link Display#asyncExec(Runnable)}. This may
+ * include events such as the disposal of the browser's parent composite, which
+ * leads to a failure in browser initialization if processed in between the OS
+ * events for initialization. Thus, this method does not implement an ordinary
+ * readAndDispatch loop, but waits for an OS event to be processed.
+ */
+private static void processNextOSMessage() {
+	Display display = Display.getCurrent();
+	MSG msg = new MSG();
+	while (!OS.PeekMessage (msg, 0, 0, 0, OS.PM_NOREMOVE)) {
+		display.sleep();
+	}
+	display.readAndDispatch();
+}
+
 static ICoreWebView2CookieManager getCookieManager() {
 	if (Instances.isEmpty()) {
 		SWT.error(SWT.ERROR_NOT_IMPLEMENTED, null, " [WebView2: cookie access requires a Browser instance]");

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_browser_Browser.java

@@ -268,6 +268,17 @@ public void test_ConstructorLorg_eclipse_swt_widgets_CompositeI() {
 	browser = createBrowser(null, SWT.NONE); // Should throw.
 }
 
+/**
+ * Regression test for issue #339: [Edge] No more handle exceptions from Edge browser
+ */
+@Test
+public void test_Constructor_asyncParentDisposal() {
+	Display.getCurrent().asyncExec(() -> {
+		shell.dispose();
+	});
+	Browser browser = createBrowser(shell, SWT.EDGE);
+	assertFalse(browser.isDisposed());
+}
 
 @Test
 public void test_evalute_Cookies () {