Use DispatcherTaskScheduler instead of TaskScheduler.FromCurrentSynchronizationContext

src/Avalonia.Base/Animation/Animation.cs

@@ -7,6 +7,7 @@
 using Avalonia.Animation.Easings;
 using Avalonia.Data;
 using Avalonia.Metadata;
+using Avalonia.Threading;
 
 namespace Avalonia.Animation
 {
@@ -310,7 +311,7 @@ internal IDisposable Apply(Animatable control, IClock? clock, IObservable<bool>
                     Task.WhenAll(completionTasks!)
                         .ContinueWith((_, state) => ((Action)state!).Invoke()
                             , onComplete
-                            , TaskScheduler.FromCurrentSynchronizationContext()
+                            , DispatcherTaskScheduler.UIThread
                             );
                 }
             }

src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin.cs

@@ -3,6 +3,7 @@
 using System.Reflection;
 using System.Threading.Tasks;
 using Avalonia.Reactive;
+using Avalonia.Threading;
 
 namespace Avalonia.Data.Core.Plugins
 {
@@ -51,7 +52,7 @@ public virtual bool Match(WeakReference<object?> reference)
                             var subject = new LightweightSubject<object?>();
                             task.ContinueWith(
                                     x => HandleCompleted(task).Subscribe(subject),
-                                    TaskScheduler.FromCurrentSynchronizationContext())
+                                    DispatcherTaskScheduler.UIThread)
                                 .ConfigureAwait(false);
                             return subject;
                     }

src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin`1.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Threading.Tasks;
 using Avalonia.Reactive;
+using Avalonia.Threading;
 
 namespace Avalonia.Data.Core.Plugins;
 
@@ -27,7 +28,7 @@ public bool Match(WeakReference<object?> reference)
                 var subject = new LightweightSubject<object?>();
                 task.ContinueWith(
                         _ => HandleCompleted(task).Subscribe(subject),
-                        TaskScheduler.FromCurrentSynchronizationContext())
+                        DispatcherTaskScheduler.UIThread)
                     .ConfigureAwait(false);
                 return subject;
         }

src/Avalonia.Base/Threading/DispatcherTaskScheduler.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Avalonia.Threading;
+
+internal class DispatcherTaskScheduler : TaskScheduler
+{
+    private static DispatcherTaskScheduler? s_uiThread;
+    public static DispatcherTaskScheduler UIThread => s_uiThread ??= new DispatcherTaskScheduler(Dispatcher.UIThread); 
+
+    private readonly Dispatcher _dispatcher;
+    private readonly SendOrPostCallback _postCallback;
+
+    public DispatcherTaskScheduler(Dispatcher dispatcher)
+    {
+        _dispatcher = dispatcher ?? throw new ArgumentNullException(nameof(dispatcher));
+        _postCallback = QueueTaskCallback;
+    }
+
+    protected override IEnumerable<Task>? GetScheduledTasks() => null;
+
+    protected override void QueueTask(Task task)
+    {
+        _dispatcher.Post(_postCallback, task);
+    }
+
+    protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
+    {
+        if (!_dispatcher.CheckAccess())
+            return false;
+
+        return TryExecuteTask(task);
+    }
+
+    private void QueueTaskCallback(object? state) => TryExecuteTask((Task)state!);
+}

src/Avalonia.Controls/TransitioningContentControl.cs

@@ -5,6 +5,7 @@
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Templates;
 using Avalonia.Interactivity;
+using Avalonia.Threading;
 
 namespace Avalonia.Controls;
 
@@ -103,7 +104,7 @@ Presenter is { } presenter &&
                     {
                         HideOldPresenter();
                     }
-                }, TaskScheduler.FromCurrentSynchronizationContext());
+                }, DispatcherTaskScheduler.UIThread);
             }
 
             _shouldAnimate = false;

src/Avalonia.Controls/VirtualizingCarouselPanel.cs

@@ -7,6 +7,7 @@
 using Avalonia.Animation;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
+using Avalonia.Threading;
 
 namespace Avalonia.Controls
 {
@@ -167,7 +168,7 @@ _realized is { } to &&
                 }
 
                 transition.Start(_transitionFrom, to, forward, _transition.Token)
-                    .ContinueWith(TransitionFinished, TaskScheduler.FromCurrentSynchronizationContext());
+                    .ContinueWith(TransitionFinished, DispatcherTaskScheduler.UIThread);
             }
 
             return result;

src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/TaskStreamPlugin.cs

@@ -3,6 +3,7 @@
 using Avalonia.Data;
 using Avalonia.Data.Core.Plugins;
 using Avalonia.Reactive;
+using Avalonia.Threading;
 
 namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
 {
@@ -29,7 +30,7 @@ public bool Match(WeakReference<object?> reference)
                     var subject = new LightweightSubject<object?>();
                     task.ContinueWith(
                             _ => HandleCompleted(task).Subscribe(subject),
-                            TaskScheduler.FromCurrentSynchronizationContext())
+                            DispatcherTaskScheduler.UIThread)
                         .ConfigureAwait(false);
                     return subject;
             }