Merge pull request unoplatform#17902 from Youssef1313/onlaunched

fix: OnLaunched should be called synchronously with app initialization

src/SamplesApp/SamplesApp.Shared/App.xaml.cs

@@ -33,8 +33,12 @@
 #endif
 
 #if HAS_UNO_WINUI || WINAPPSDK
+using DispatcherQueue = Microsoft.UI.Dispatching.DispatcherQueue;
+using DispatcherQueuePriority = Microsoft.UI.Dispatching.DispatcherQueuePriority;
 using LaunchActivatedEventArgs = Microsoft/* UWP don't rename */.UI.Xaml.LaunchActivatedEventArgs;
 #else
+using DispatcherQueue = Windows.System.DispatcherQueue;
+using DispatcherQueuePriority = Windows.System.DispatcherQueuePriority;
 using LaunchActivatedEventArgs = Windows.ApplicationModel.Activation.LaunchActivatedEventArgs;
 #endif
 
@@ -62,6 +66,7 @@ sealed public partial class App : Application
 		private static Microsoft.UI.Xaml.Window? _mainWindow;
 		private bool _wasActivated;
 		private bool _isSuspended;
+		private bool _gotOnLaunched;
 
 		static App()
 		{
@@ -94,6 +99,11 @@ public App()
 			this.Suspending += OnSuspending;
 			this.Resuming += OnResuming;
 #endif
+
+			DispatcherQueue.GetForCurrentThread().TryEnqueue(DispatcherQueuePriority.High, () =>
+			{
+				Assert.IsTrue(_gotOnLaunched);
+			});
 		}
 
 		internal static Microsoft.UI.Xaml.Window? MainWindow => _mainWindow;
@@ -109,6 +119,7 @@ public App()
 #endif
 		override void OnLaunched(LaunchActivatedEventArgs e)
 		{
+			_gotOnLaunched = true;
 			EnsureMainWindow();
 
 			SetupAndroidEnvironment();

src/Uno.UI/UI/Xaml/Application.skia.cs

@@ -18,17 +18,19 @@ public partial class Application : IApplicationEvents
 	{
 		private static bool _startInvoked;
 
+		[ThreadStatic]
+		private static Application _current;
+
 		partial void InitializePartial()
 		{
+			_current = this;
 			SetCurrentLanguage();
 
 			if (!_startInvoked)
 			{
 				throw new InvalidOperationException("The application must be started using Application.Start first, e.g. Microsoft.UI.Xaml.Application.Start(_ => new App());");
 			}
 
-			_ = CoreDispatcher.Main.RunAsync(CoreDispatcherPriority.Normal, Initialize);
-
 			CoreApplication.SetInvalidateRender(compositionTarget =>
 			{
 				Debug.Assert(compositionTarget is null or CompositionTarget);
@@ -81,9 +83,11 @@ static partial void StartPartial(ApplicationInitializationCallback callback)
 			);
 
 			callback(new ApplicationInitializationCallbackParams());
+
+			_current.InvokeOnLaunched();
 		}
 
-		private void Initialize()
+		private void InvokeOnLaunched()
 		{
 			using (WritePhaseEventTrace(TraceProvider.LauchedStart, TraceProvider.LauchedStop))
 			{