fix: Set initial Window size earlier on WASM

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

@@ -110,7 +110,7 @@ namespace Windows.UI.Xaml
 				// Force init
 				Window.Current.ToString();
 
-				var arguments = WindowManagerInterop.FindLaunchArguments();
+				var arguments = WindowManagerInterop.BeforeLaunch();
 
 				if (this.Log().IsEnabled(Uno.Foundation.Logging.LogLevel.Debug))
 				{

src/Uno.UI/UI/Xaml/Window.wasm.cs

@@ -96,17 +96,7 @@ namespace Windows.UI.Xaml
 
 		[JSExport]
 		[Preserve]
-		public static void Resize(double width, double height)
-		{
-			var window = Current?._rootVisual;
-			if (window == null)
-			{
-				typeof(Window).Log().Error($"Resize ignore, no current window defined");
-				return; // nothing to measure
-			}
-
-			Current.OnNativeSizeChanged(new Size(width, height));
-		}
+		public static void Resize(double width, double height) => Current.OnNativeSizeChanged(new Size(width, height));
 
 		private void OnNativeSizeChanged(Size size)
 		{
@@ -164,6 +154,7 @@ namespace Windows.UI.Xaml
 				}
 
 				WindowManagerInterop.SetRootElement(_rootVisual.HtmlId);
+				DispatchInvalidateMeasure();
 
 				if (FeatureConfiguration.FrameworkElement.WasmUseManagedLoadedUnloaded)
 				{

src/Uno.UI/UI/Xaml/WindowManagerInterop.wasm.cs

@@ -28,9 +28,16 @@ namespace Uno.UI.Xaml
 		internal static Task InitAsync(bool isLoadEventsEnabled)
 			=> NativeMethods.InitAsync(isLoadEventsEnabled);
 
-		internal static string FindLaunchArguments()
-			=> NativeMethods.FindLaunchArguments();
-
+		/// <summary>
+		/// This method has two purposes:
+		/// - Initializes the window size before launch
+		/// - Returns the app arguments
+		/// The reason for having two concerns in one method 
+		/// is to avoid unnecessary roundtrip between JS and C#.
+		/// </summary>
+		/// <returns>App launch arguments.</returns>
+		internal static string BeforeLaunch()
+			=> NativeMethods.BeforeLaunch();
 
 		internal static double GetBootTime()
 			=> NativeMethods.GetBootTime();
@@ -1095,8 +1102,8 @@ namespace Uno.UI.Xaml
 			[JSImport("globalThis.Uno.UI.WindowManager.current.destroyViewNativeFast")]
 			internal static partial void DestroyView(IntPtr htmlId);
 
-			[JSImport("globalThis.Uno.UI.WindowManager.findLaunchArguments")]
-			internal static partial string FindLaunchArguments();
+			[JSImport("globalThis.Uno.UI.WindowManager.beforeLaunch")]
+			internal static partial string BeforeLaunch();
 
 			[JSImport("globalThis.Uno.UI.WindowManager.getBootTime")]
 			internal static partial double GetBootTime();

src/Uno.UI/ts/WindowManager.ts

@@ -194,7 +194,9 @@ namespace Uno.UI {
 			* Reads the window's search parameters
 			* 
 			*/
-		static findLaunchArguments(): string {
+		static beforeLaunch(): string {
+			WindowManager.resize();
+
 			if (typeof URLSearchParams === "function") {
 				return new URLSearchParams(window.location.search).toString();
 			}
@@ -1056,8 +1058,6 @@ namespace Uno.UI {
 				this.dispatchEvent(this.rootElement, "loaded");
 			}
 			this.setAsArranged(newRootElement); // patch because root is not measured/arranged
-
-			this.resize();
 		}
 
 		/**
@@ -1656,7 +1656,7 @@ namespace Uno.UI {
 			document.body.addEventListener("focusin", this.onfocusin);
 			document.body.appendChild(this.containerElement);
 
-			window.addEventListener("resize", x => this.resize());
+			window.addEventListener("resize", x => WindowManager.resize());
 			window.addEventListener("contextmenu", x => {
 				if (!(x.target instanceof HTMLInputElement) ||
 					x.target.classList.contains("context-menu-disabled")) {
@@ -1679,7 +1679,7 @@ namespace Uno.UI {
 			}
 		}
 
-		private resize() {
+		private static resize() {
 			WindowManager.resizeMethod(document.documentElement.clientWidth, document.documentElement.clientHeight);
 		}