feat: Application.Exit on GTK and WPF

src/Uno.UI.Runtime.Skia.Gtk/GtkApplicationExtension.cs

@@ -0,0 +1,20 @@
+using System;
+using Uno.UI.Xaml;
+using Windows.UI.Xaml;
+
+namespace Uno.UI.Runtime.Skia
+{
+	public class GtkApplicationExtension : IApplicationExtension
+	{
+		private readonly Application _owner;
+
+		public GtkApplicationExtension(Application owner)
+		{
+			_owner = owner ?? throw new ArgumentNullException(nameof(owner));
+		}
+
+		public bool CanExit => true;
+
+		public void Exit() => Gtk.Application.Default.Quit();
+	}
+}

src/Uno.UI.Runtime.Skia.Gtk/GtkHost.cs

@@ -13,7 +13,8 @@
 using Windows.UI.Xaml.Controls;
 using Gtk;
 using Uno.UI.Runtime.Skia.GTK.Extensions.Helpers;
-
+using Uno.UI.Xaml;
+
 namespace Uno.UI.Runtime.Skia
 {
 	public class GtkHost : ISkiaHost
@@ -46,6 +47,7 @@ public void Run()
 			SetupTheme();
 
 			ApiExtensibility.Register(typeof(Windows.UI.Core.ICoreWindowExtension), o => new GtkCoreWindowExtension(o));
+			ApiExtensibility.Register<Windows.UI.Xaml.Application>(typeof(IApplicationExtension), o => new GtkApplicationExtension(o));
 			ApiExtensibility.Register(typeof(Windows.UI.ViewManagement.IApplicationViewExtension), o => new GtkApplicationViewExtension(o));
 			ApiExtensibility.Register(typeof(ISystemThemeHelperExtension), o => new GtkSystemThemeHelperExtension(o));
 			ApiExtensibility.Register(typeof(Windows.Graphics.Display.IDisplayInformationExtension), o => _displayInformationExtension ??= new GtkDisplayInformationExtension(o, _window));

src/Uno.UI.Runtime.Skia.Wpf/WpfApplicationExtension.cs

@@ -0,0 +1,20 @@
+using System;
+using Uno.UI.Xaml;
+using Windows.UI.Xaml;
+
+namespace Uno.UI.Runtime.Skia.Wpf
+{
+	public class WpfApplicationExtension : IApplicationExtension
+	{
+		private readonly Application _owner;
+
+		public WpfApplicationExtension(Application owner)
+		{
+			_owner = owner ?? throw new ArgumentNullException(nameof(owner));
+		}
+
+		public bool CanExit => true;
+
+		public void Exit() => System.Windows.Application.Current.Shutdown();
+	}
+}

src/Uno.UI.Runtime.Skia.Wpf/WpfHost.cs

@@ -22,6 +22,8 @@
 using WpfCanvas = System.Windows.Controls.Canvas;
 using WpfControl = System.Windows.Controls.Control;
 using WpfFrameworkPropertyMetadata = System.Windows.FrameworkPropertyMetadata;
+using Uno.UI.Xaml;
+using Uno.UI.Runtime.Skia.Wpf;
 
 namespace Uno.UI.Skia.Platform
 {
@@ -43,6 +45,7 @@ static WpfHost()
 			DefaultStyleKeyProperty.OverrideMetadata(typeof(WpfHost), new WpfFrameworkPropertyMetadata(typeof(WpfHost)));
 
 			ApiExtensibility.Register(typeof(Windows.UI.Core.ICoreWindowExtension), o => new WpfCoreWindowExtension(o));
+			ApiExtensibility.Register<Windows.UI.Xaml.Application>(typeof(IApplicationExtension), o => new WpfApplicationExtension(o));
 			ApiExtensibility.Register(typeof(Windows.UI.ViewManagement.IApplicationViewExtension), o => new WpfApplicationViewExtension(o));
 			ApiExtensibility.Register(typeof(ISystemThemeHelperExtension), o => new WpfSystemThemeHelperExtension(o));
 			ApiExtensibility.Register(typeof(IDisplayInformationExtension), o => new WpfDisplayInformationExtension(o));

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

@@ -12,13 +12,15 @@
 using Uno.UI;
 using Uno.UI.Xaml;
 using Uno.Foundation.Extensibility;
+using Microsoft.Extensions.Logging;
 
 namespace Windows.UI.Xaml
 {
 	public partial class Application : IApplicationEvents
 	{
 		private static bool _startInvoked = false;
 		private static string[] _args;
+		private readonly IApplicationExtension _applicationExtension;
 
 		internal ISkiaHost Host { get; set; }
 
@@ -32,7 +34,7 @@ public Application()
 				throw new InvalidOperationException("The application must be started using Application.Start first, e.g. Windows.UI.Xaml.Application.Start(_ => new App());");
 			}
 
-			CoreDispatcher.Main.RunAsync(CoreDispatcherPriority.Normal, Initialize);
+			ApiExtensibility.CreateInstance(this, out _applicationExtension);
 		}
 
 		internal static void Start(global::Windows.UI.Xaml.ApplicationInitializationCallback callback, string[] args)
@@ -41,6 +43,21 @@ internal static void Start(global::Windows.UI.Xaml.ApplicationInitializationCall
 			Start(callback);
 		}
 
+		public void Exit()
+		{
+			if (_applicationExtension != null && _applicationExtension.CanExit)
+			{
+				_applicationExtension.Exit();
+			}
+			else
+			{
+				if (this.Log().IsEnabled(LogLevel.Warning))
+				{
+					this.Log().LogWarning("This platform does not support application exit.");
+				}
+			}
+		}
+
 		static partial void StartPartial(ApplicationInitializationCallback callback)
 		{
 			_startInvoked = true;

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

@@ -11,6 +11,7 @@
 using Uno.Helpers.Theming;
 using Windows.UI.ViewManagement;
 using Uno.Extensions;
+using Microsoft.Extensions.Logging;
 
 #if HAS_UNO_WINUI
 using LaunchActivatedEventArgs = Microsoft.UI.Xaml.LaunchActivatedEventArgs;
@@ -182,11 +183,14 @@ public void OnSystemThemeChanged()
 			UISettings.OnColorValuesChanged();
 		}
 
-#if !__ANDROID__ && !__MACOS__
+#if !__ANDROID__ && !__MACOS__ && !__SKIA__
 		[NotImplemented]
 		public void Exit()
 		{
-
+			if (this.Log().IsEnabled(LogLevel.Warning))
+			{
+				this.Log().LogWarning("This platform does not support application exit.");
+			}
 		}
 #endif
 

src/Uno.UI/UI/Xaml/IApplicationExtension.cs

@@ -0,0 +1,9 @@
+namespace Uno.UI.Xaml
+{
+	internal interface IApplicationExtension
+    {
+        bool CanExit { get; }
+
+		void Exit();
+    }
+}