Removed `Application` parameter from ClassicDesktopStyleApplicationLifetime since it wasn't used anyway

src/Avalonia.Controls/AppBuilderBase.cs

@@ -125,7 +125,7 @@ namespace Avalonia.Controls
             });
             
             // Copy-pasted because we can't call extension methods due to generic constraints
-            var lifetime = new ClassicDesktopStyleApplicationLifetime(Instance) {ShutdownMode = ShutdownMode.OnMainWindowClose};
+            var lifetime = new ClassicDesktopStyleApplicationLifetime() {ShutdownMode = ShutdownMode.OnMainWindowClose};
             SetupWithLifetime(lifetime);
             lifetime.Start(Array.Empty<string>());
         }

src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs

@@ -5,12 +5,12 @@ using System.Threading;
 using Avalonia.Controls;
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Interactivity;
+using Avalonia.Threading;
 
 namespace Avalonia.Controls.ApplicationLifetimes
 {
     public class ClassicDesktopStyleApplicationLifetime : IClassicDesktopStyleApplicationLifetime, IDisposable
     {
-        private readonly Application _app;
         private int _exitCode;
         private CancellationTokenSource _cts;
         private bool _isShuttingDown;
@@ -34,12 +34,11 @@ namespace Avalonia.Controls.ApplicationLifetimes
             _activeLifetime?._windows.Add((Window)sender);
         }
 
-        public ClassicDesktopStyleApplicationLifetime(Application app)
+        public ClassicDesktopStyleApplicationLifetime()
         {
             if (_activeLifetime != null)
                 throw new InvalidOperationException(
                     "Can not have multiple active ClassicDesktopStyleApplicationLifetime instances and the previously created one was not disposed");
-            _app = app;
             _activeLifetime = this;
         }
         
@@ -103,7 +102,7 @@ namespace Avalonia.Controls.ApplicationLifetimes
             Startup?.Invoke(this, new ControlledApplicationLifetimeStartupEventArgs(args));
             _cts = new CancellationTokenSource();
             MainWindow?.Show();
-            _app.Run(_cts.Token);
+            Dispatcher.UIThread.MainLoop(_cts.Token);
             Environment.ExitCode = _exitCode;
             return _exitCode;
         }
@@ -124,7 +123,7 @@ namespace Avalonia
             this T builder, string[] args, ShutdownMode shutdownMode = ShutdownMode.OnLastWindowClose)
             where T : AppBuilderBase<T>, new()
         {
-            var lifetime = new ClassicDesktopStyleApplicationLifetime(builder.Instance) {ShutdownMode = shutdownMode};
+            var lifetime = new ClassicDesktopStyleApplicationLifetime() {ShutdownMode = shutdownMode};
             builder.SetupWithLifetime(lifetime);
             return lifetime.Start(args);
         }

tests/Avalonia.Controls.UnitTests/DesktopStyleApplicationLifetimeTests.cs

@@ -16,7 +16,7 @@ namespace Avalonia.Controls.UnitTests
         public void Should_Set_ExitCode_After_Shutdown()
         {
             using (UnitTestApplication.Start(TestServices.MockThreadingInterface))
-            using(var lifetime = new ClassicDesktopStyleApplicationLifetime(Application.Current))    
+            using(var lifetime = new ClassicDesktopStyleApplicationLifetime())    
             {
                 lifetime.Shutdown(1337);
 
@@ -31,7 +31,7 @@ namespace Avalonia.Controls.UnitTests
         public void Should_Close_All_Remaining_Open_Windows_After_Explicit_Exit_Call()
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
-            using(var lifetime = new ClassicDesktopStyleApplicationLifetime(Application.Current))
+            using(var lifetime = new ClassicDesktopStyleApplicationLifetime())
             {
                 var windows = new List<Window> { new Window(), new Window(), new Window(), new Window() };
 
@@ -50,7 +50,7 @@ namespace Avalonia.Controls.UnitTests
         public void Should_Only_Exit_On_Explicit_Exit()
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
-            using(var lifetime = new ClassicDesktopStyleApplicationLifetime(Application.Current))
+            using(var lifetime = new ClassicDesktopStyleApplicationLifetime())
             {
                 lifetime.ShutdownMode = ShutdownMode.OnExplicitShutdown;
 
@@ -84,7 +84,7 @@ namespace Avalonia.Controls.UnitTests
         public void Should_Exit_After_MainWindow_Closed()
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
-            using(var lifetime = new ClassicDesktopStyleApplicationLifetime(Application.Current))
+            using(var lifetime = new ClassicDesktopStyleApplicationLifetime())
             {
                 lifetime.ShutdownMode = ShutdownMode.OnMainWindowClose;
 
@@ -112,7 +112,7 @@ namespace Avalonia.Controls.UnitTests
         public void Should_Exit_After_Last_Window_Closed()
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
-            using(var lifetime = new ClassicDesktopStyleApplicationLifetime(Application.Current))
+            using(var lifetime = new ClassicDesktopStyleApplicationLifetime())
             {
                 lifetime.ShutdownMode = ShutdownMode.OnLastWindowClose;
 
@@ -142,7 +142,7 @@ namespace Avalonia.Controls.UnitTests
         public void Show_Should_Add_Window_To_OpenWindows()
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
-            using(var lifetime = new ClassicDesktopStyleApplicationLifetime(Application.Current))
+            using(var lifetime = new ClassicDesktopStyleApplicationLifetime())
             {
                 var window = new Window();
 
@@ -156,7 +156,7 @@ namespace Avalonia.Controls.UnitTests
         public void Window_Should_Be_Added_To_OpenWindows_Only_Once()
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
-            using(var lifetime = new ClassicDesktopStyleApplicationLifetime(Application.Current))
+            using(var lifetime = new ClassicDesktopStyleApplicationLifetime())
             {
                 var window = new Window();
 
@@ -174,7 +174,7 @@ namespace Avalonia.Controls.UnitTests
         public void Close_Should_Remove_Window_From_OpenWindows()
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
-            using(var lifetime = new ClassicDesktopStyleApplicationLifetime(Application.Current))
+            using(var lifetime = new ClassicDesktopStyleApplicationLifetime())
             {
                 var window = new Window();
 
@@ -197,7 +197,7 @@ namespace Avalonia.Controls.UnitTests
                 windowingPlatform: new MockWindowingPlatform(() => windowImpl.Object));
 
             using (UnitTestApplication.Start(services))
-            using(var lifetime = new ClassicDesktopStyleApplicationLifetime(Application.Current))
+            using(var lifetime = new ClassicDesktopStyleApplicationLifetime())
             {
                 var window = new Window();
 

tests/Avalonia.ReactiveUI.UnitTests/AutoSuspendHelperTest.cs

@@ -45,7 +45,7 @@ namespace Avalonia.ReactiveUI.UnitTests
         public void AutoSuspendHelper_Should_Immediately_Fire_IsLaunchingNew() 
         {
             using (UnitTestApplication.Start(TestServices.MockWindowingPlatform)) 
-            using (var lifetime = new ClassicDesktopStyleApplicationLifetime(Application.Current))
+            using (var lifetime = new ClassicDesktopStyleApplicationLifetime())
             {
                 var isLaunchingReceived = false;
                 var application = AvaloniaLocator.Current.GetService<Application>();
@@ -86,7 +86,7 @@ namespace Avalonia.ReactiveUI.UnitTests
         public void ShouldPersistState_Should_Fire_On_App_Exit_When_SuspensionDriver_Is_Initialized() 
         {
             using (UnitTestApplication.Start(TestServices.MockWindowingPlatform))
-            using (var lifetime = new ClassicDesktopStyleApplicationLifetime(Application.Current)) 
+            using (var lifetime = new ClassicDesktopStyleApplicationLifetime()) 
             {
                 var shouldPersistReceived = false;
                 var application = AvaloniaLocator.Current.GetService<Application>();
@@ -105,4 +105,4 @@ namespace Avalonia.ReactiveUI.UnitTests
             }
         }
     }
-}
+}