[GTK4] Cleanup execution of non-blocking dialog calls

This adds a new AsyncReadyCallback class which is used to handle the
asynchronous execution of dialogs. The goal is provide a cleaner and
more readable interface than what is currently available by
SyncDialogUtil.

Note that this class currently simply wraps the call to SyncDialogUtil.
But once all of the remaining dialogs (Color/Font/MessageDialog) have
been migrated, it might make sense to remove this class entirely to
avoid this additional indirection.

Follow-up to 2e61b4b

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/internal/AsyncReadyCallback.java

@@ -0,0 +1,51 @@
+/*******************************************************************************
+ * Copyright (c) 2024 Patrick Ziegler 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:
+ *     Patrick Ziegler - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.swt.internal;
+
+import org.eclipse.swt.widgets.*;
+
+/**
+ * This class implements the GIO AsyncReadyCallback type and is used to
+ * transform an asynchronous {@code async} and synchronous {@code await}
+ * operation into a single synchronous {@code run} operation.
+ */
+public abstract class AsyncReadyCallback {
+	/**
+	 * This method is responsible for initializes the asynchronous operation
+	 *
+	 * @param callback The callback address to execute when the operation is
+	 *                 complete.
+	 */
+	protected abstract void async(long callback);
+
+	/**
+	 * This method is called from within the callback function in order to
+	 * finish the executed operation and to return the result.
+	 *
+	 * @param result The generic, asynchronous function result.
+	 * @return The specific result of the operation.
+	 */
+	protected abstract long await(long result);
+
+	/**
+	 * This method executes the asynchronous operation and blocks until it has
+	 * completed.
+	 *
+	 * @param display The display used for blocking.
+	 * @return The result of the asynchronous operation.
+	 */
+	public final long run(Display display) {
+		return SyncDialogUtil.run(display, this::async , this::await);
+	}
+}

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/DirectoryDialog.java

@@ -214,9 +214,17 @@ Optional<String> openNativeChooserDialog () {
 	int response;
 	long file = 0;
 	if (GTK.GTK4) {
-		file = SyncDialogUtil.run(display,
-				asyncCallback -> GTK4.gtk_file_dialog_select_folder(handle, shellHandle, 0, asyncCallback, 0),
-				asyncResult -> GTK4.gtk_file_dialog_select_folder_finish(handle, asyncResult, null));
+		file = new AsyncReadyCallback() {
+			@Override
+			protected void async(long result) {
+				GTK4.gtk_file_dialog_select_folder(handle, shellHandle, 0, result, 0);
+			}
+
+			@Override
+			protected long await(long result) {
+				return GTK4.gtk_file_dialog_select_folder_finish(handle, result, null);
+			}
+		}.run(display);
 		response = file != 0 ? GTK.GTK_RESPONSE_ACCEPT : GTK.GTK_RESPONSE_CANCEL;
 	} else {
 		display.externalEventLoop = true;

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/FileDialog.java

@@ -404,18 +404,42 @@ Optional<String> openNativeChooserDialog () {
 	long file = 0;
 	if (GTK.GTK4) {
 		if ((style & SWT.MULTI) != 0) {
-			file = SyncDialogUtil.run(display,
-					asyncCallback -> GTK4.gtk_file_dialog_open_multiple(handle, shellHandle, 0, asyncCallback, 0),
-					asyncResult -> GTK4.gtk_file_dialog_open_multiple_finish(handle, asyncResult, null));
+			file = new AsyncReadyCallback() {
+				@Override
+				protected void async(long callback) {
+					GTK4.gtk_file_dialog_open_multiple(handle, shellHandle, 0, callback, 0);
+				}
+
+				@Override
+				protected long await(long result) {
+					return GTK4.gtk_file_dialog_open_multiple_finish(handle, result, null);
+				}
+			}.run(display);
 		} else {
 			if ((style & SWT.SAVE) != 0) {
-				file = SyncDialogUtil.run(display,
-						asyncCallback -> GTK4.gtk_file_dialog_save(handle, shellHandle, 0, asyncCallback, 0),
-						asyncResult -> GTK4.gtk_file_dialog_save_finish(handle, asyncResult, null));
+				file = new AsyncReadyCallback() {
+					@Override
+					protected void async(long callback) {
+						GTK4.gtk_file_dialog_save(handle, shellHandle, 0, callback, 0);
+					}
+
+					@Override
+					protected long await(long result) {
+						return GTK4.gtk_file_dialog_save_finish(handle, result, null);
+					}
+				}.run(display);
 			} else {
-				file = SyncDialogUtil.run(display,
-						asyncCallback -> GTK4.gtk_file_dialog_open(handle, shellHandle, 0, asyncCallback, 0),
-						asyncResult -> GTK4.gtk_file_dialog_open_finish(handle, asyncResult, null));
+				file = new AsyncReadyCallback() {
+					@Override
+					protected void async(long callback) {
+						GTK4.gtk_file_dialog_open(handle, shellHandle, 0, callback, 0);
+					}
+
+					@Override
+					protected long await(long result) {
+						return GTK4.gtk_file_dialog_open_finish(handle, result, null);
+					}
+				}.run(display);
 			}
 		}
 		response = file != 0 ? GTK.GTK_RESPONSE_ACCEPT : GTK.GTK_RESPONSE_CANCEL;