Merge remote-tracking branch 'origin/master' into feature/borking-changes

samples/ControlCatalog/MainView.xaml.cs

@@ -83,9 +83,10 @@ namespace ControlCatalog
                 if (transparencyLevels.SelectedItem is WindowTransparencyLevel selected)
                 {
                     var topLevel = (TopLevel)this.GetVisualRoot()!;
-                    topLevel.TransparencyLevelHint = selected;
+                    topLevel.TransparencyLevelHint = new[] { selected };
 
-                    if (selected != WindowTransparencyLevel.None)
+                    if (topLevel.ActualTransparencyLevel != WindowTransparencyLevel.None &&
+                        topLevel.ActualTransparencyLevel == selected)
                     {
                         var transparentBrush = new ImmutableSolidColorBrush(Colors.White, 0);
                         var semiTransparentBrush = new ImmutableSolidColorBrush(Colors.Gray, 0.2);

samples/ControlCatalog/Pages/ContextMenuPage.xaml.cs

@@ -19,8 +19,8 @@ namespace ControlCatalog.Pages
             customContextRequestedBorder.AddHandler(ContextRequestedEvent, CustomContextRequested, RoutingStrategies.Tunnel);
 
             var cancellableContextBorder = this.Get<Border>("CancellableContextBorder");
-            cancellableContextBorder.ContextMenu!.ContextMenuClosing += ContextFlyoutPage_Closing;
-            cancellableContextBorder.ContextMenu!.ContextMenuOpening += ContextFlyoutPage_Opening;
+            cancellableContextBorder.ContextMenu!.Closing += ContextFlyoutPage_Closing;
+            cancellableContextBorder.ContextMenu!.Opening += ContextFlyoutPage_Opening;
         }
 
         private ContextPageViewModel? _model;

samples/IntegrationTestApp/MainWindow.axaml.cs

@@ -136,7 +136,7 @@ namespace IntegrationTestApp
                 Name = "TransparentWindow",
                 SystemDecorations = SystemDecorations.None,
                 Background = Brushes.Transparent,
-                TransparencyLevelHint = WindowTransparencyLevel.Transparent,
+                TransparencyLevelHint = new[] { WindowTransparencyLevel.Transparent },
                 WindowStartupLocation = WindowStartupLocation.CenterOwner,
                 Width = 200,
                 Height = 200,

src/Android/Avalonia.Android/AndroidPlatform.cs

@@ -52,11 +52,7 @@ namespace Avalonia.Android
                 EglPlatformGraphics.TryInitialize();
             }
             
-            Compositor = new Compositor(
-                AvaloniaLocator.Current.GetRequiredService<IRenderLoop>(),
-                AvaloniaLocator.Current.GetService<IPlatformGraphics>());
-            
-
+            Compositor = new Compositor(AvaloniaLocator.Current.GetService<IPlatformGraphics>());
         }
     }
 

src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Runtime.Versioning;
 using Android.App;
 using Android.Content;
 using Android.Graphics;
@@ -45,6 +46,7 @@ namespace Avalonia.Android.Platform.SkiaPlatform
         private readonly AndroidInsetsManager _insetsManager;
         private readonly ClipboardImpl _clipboard;
         private ViewImpl _view;
+        private WindowTransparencyLevel _transparencyLevel;
 
         public TopLevelImpl(AvaloniaView avaloniaView, bool placeOnTop = false)
         {
@@ -68,6 +70,7 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
             _nativeControlHost = new AndroidNativeControlHostImpl(avaloniaView);
             _storageProvider = new AndroidStorageProvider((Activity)avaloniaView.Context);
+            _transparencyLevel = WindowTransparencyLevel.None;
 
             _systemNavigationManager = new AndroidSystemNavigationManagerImpl(avaloniaView.Context as IActivityNavigationService);
         }
@@ -273,7 +276,18 @@ namespace Avalonia.Android.Platform.SkiaPlatform
         public Action LostFocus { get; set; }
         public Action<WindowTransparencyLevel> TransparencyLevelChanged { get; set; }
 
-        public WindowTransparencyLevel TransparencyLevel { get; private set; }
+        public WindowTransparencyLevel TransparencyLevel 
+        {
+            get => _transparencyLevel;
+            private set
+            {
+                if (_transparencyLevel != value)
+                {
+                    _transparencyLevel = value;
+                    TransparencyLevelChanged?.Invoke(value);
+                }
+            }
+        }
 
         public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
         {
@@ -298,91 +312,64 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
         public double Scaling => RenderScaling;
 
-        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel)
+        public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevels)
         {
-            if (TransparencyLevel != transparencyLevel)
+            if (_view.Context is not AvaloniaMainActivity activity)
+                return;
+
+            foreach (var level in transparencyLevels)
             {
-                bool isBelowR = Build.VERSION.SdkInt < BuildVersionCodes.R;
-                bool isAboveR = Build.VERSION.SdkInt > BuildVersionCodes.R;
-                if (_view.Context is AvaloniaMainActivity activity)
+                if (!IsSupported(level))
+                {
+                    continue;
+                }
+
+                if (level == TransparencyLevel)
+                {
+                    return;
+                }
+
+                if (level == WindowTransparencyLevel.None)
+                {
+                    if (OperatingSystem.IsAndroidVersionAtLeast(30))
+                    {
+                        activity.SetTranslucent(false);
+                    }
+
+                    activity.Window?.SetBackgroundDrawable(new ColorDrawable(Color.White));
+                }
+                else if (level == WindowTransparencyLevel.Transparent)
+                {
+                    if (OperatingSystem.IsAndroidVersionAtLeast(30))
+                    {
+                        activity.SetTranslucent(true);
+                        SetBlurBehind(activity, 0);
+                        activity.Window.SetBackgroundDrawable(new ColorDrawable(Color.Transparent));
+                    }
+                }
+                else if (level == WindowTransparencyLevel.Blur)
                 {
-                    switch (transparencyLevel)
+                    if (OperatingSystem.IsAndroidVersionAtLeast(31))
                     {
-                        case WindowTransparencyLevel.AcrylicBlur:
-                        case WindowTransparencyLevel.ForceAcrylicBlur:
-                        case WindowTransparencyLevel.Mica:
-                        case WindowTransparencyLevel.None:
-                            if (!isBelowR)
-                            {
-                                activity.SetTranslucent(false);
-                            }
-                            if (isAboveR)
-                            {
-                                activity.Window?.ClearFlags(WindowManagerFlags.BlurBehind);
-
-                                var attr = activity.Window?.Attributes;
-                                if (attr != null)
-                                {
-                                    attr.BlurBehindRadius = 0;
-
-                                    activity.Window.Attributes = attr;
-                                }
-                            }
-                            activity.Window.SetBackgroundDrawable(new ColorDrawable(Color.White));
-
-                            if(transparencyLevel != WindowTransparencyLevel.None)
-                            {
-                                return;
-                            }
-                            break;
-                        case WindowTransparencyLevel.Transparent:
-                            if (!isBelowR)
-                            {
-                                activity.SetTranslucent(true);
-                            }
-                            if (isAboveR)
-                            {
-                                activity.Window?.ClearFlags(WindowManagerFlags.BlurBehind);
-
-                                var attr = activity.Window?.Attributes;
-                                if (attr != null)
-                                {
-                                    attr.BlurBehindRadius = 0;
-
-                                    activity.Window.Attributes = attr;
-                                }
-                            }
-                            activity.Window.SetBackgroundDrawable(new ColorDrawable(Color.Transparent));
-                            break;
-                        case WindowTransparencyLevel.Blur:
-                            if (isAboveR)
-                            {
-                                activity.SetTranslucent(true);
-                                activity.Window?.AddFlags(WindowManagerFlags.BlurBehind);
-
-                                var attr = activity.Window?.Attributes;
-                                if (attr != null)
-                                {
-                                    attr.BlurBehindRadius = 120;
-
-                                    activity.Window.Attributes = attr;
-                                }
-                                activity.Window.SetBackgroundDrawable(new ColorDrawable(Color.Transparent));
-                            }
-                            else
-                            {
-                                activity.Window?.ClearFlags(WindowManagerFlags.BlurBehind);
-                                activity.Window.SetBackgroundDrawable(new ColorDrawable(Color.White));
-
-                                return;
-                            }
-                            break;
+                        activity.SetTranslucent(true);
+                        SetBlurBehind(activity, 120);
+                        activity.Window?.SetBackgroundDrawable(new ColorDrawable(Color.Transparent));
                     }
-                    TransparencyLevel = transparencyLevel;
                 }
+
+                TransparencyLevel = level;
+                return;
+            }
+
+            // If we get here, we didn't find a supported level. Use the default of None.
+            if (OperatingSystem.IsAndroidVersionAtLeast(30))
+            {
+                activity.SetTranslucent(false);
             }
+
+            activity.Window?.SetBackgroundDrawable(new ColorDrawable(Color.White));
         }
-        
+
         public virtual object TryGetFeature(Type featureType)
         {
             if (featureType == typeof(IStorageProvider))
@@ -417,6 +404,31 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
             return null;
         }
+
+        private static bool IsSupported(WindowTransparencyLevel level)
+        {
+            if (level == WindowTransparencyLevel.None)
+                return true;
+            if (level == WindowTransparencyLevel.Transparent)
+                return OperatingSystem.IsAndroidVersionAtLeast(30);
+            if (level == WindowTransparencyLevel.Blur)
+                return OperatingSystem.IsAndroidVersionAtLeast(31);
+            return false;
+        }
+
+        private static void SetBlurBehind(AvaloniaMainActivity activity, int radius)
+        {
+            if (radius == 0)
+                activity.Window?.ClearFlags(WindowManagerFlags.BlurBehind);
+            else
+                activity.Window?.AddFlags(WindowManagerFlags.BlurBehind);
+
+            if (OperatingSystem.IsAndroidVersionAtLeast(31) && activity.Window?.Attributes is { } attr)
+            {
+                attr.BlurBehindRadius = radius;
+                activity.Window.Attributes = attr;
+            }
+        }
     }
 
     internal class AvaloniaInputConnection : BaseInputConnection

src/Avalonia.Base/Data/TemplateBinding.cs

@@ -3,18 +3,21 @@ using System.Globalization;
 using Avalonia.Data.Converters;
 using Avalonia.Reactive;
 using Avalonia.Styling;
+using Avalonia.Threading;
 
 namespace Avalonia.Data
 {
     /// <summary>
     /// A XAML binding to a property on a control's templated parent.
     /// </summary>
-    public class TemplateBinding : SingleSubscriberObservableBase<object?>,
+    public class TemplateBinding : IObservable<object?>,
         IBinding,
         IDescription,
         IAvaloniaSubject<object?>,
-        ISetterValue
+        ISetterValue,
+        IDisposable
     {
+        private IObserver<object?>? _observer;
         private bool _isSetterValue;
         private StyledElement? _target;
         private Type? _targetType;
@@ -29,6 +32,28 @@ namespace Avalonia.Data
             Property = property;
         }
 
+        public IDisposable Subscribe(IObserver<object?> observer)
+        {
+            _ = observer ?? throw new ArgumentNullException(nameof(observer));
+            Dispatcher.UIThread.VerifyAccess();
+
+            if (_observer != null)
+            {
+                throw new InvalidOperationException("The observable can only be subscribed once.");
+            }
+
+            _observer = observer;
+            Subscribed();
+
+            return this;
+        }
+
+        public virtual void Dispose()
+        {
+            Unsubscribed();
+            _observer = null;
+        }
+
         /// <inheritdoc/>
         public InstancedBinding? Initiate(
             AvaloniaObject target,
@@ -111,7 +136,7 @@ namespace Avalonia.Data
         /// <inheritdoc/>
         void ISetterValue.Initialize(SetterBase setter) => _isSetterValue = true;
 
-        protected override void Subscribed()
+        private void Subscribed()
         {
             TemplatedParentChanged();
 
@@ -121,7 +146,7 @@ namespace Avalonia.Data
             }
         }
 
-        protected override void Unsubscribed()
+        private void Unsubscribed()
         {
             if (_target?.TemplatedParent is { } templatedParent)
             {
@@ -147,12 +172,12 @@ namespace Avalonia.Data
                     value = Converter.Convert(value, _targetType ?? typeof(object), ConverterParameter, CultureInfo.CurrentCulture);
                 }
 
-                PublishNext(value);
+                _observer?.OnNext(value);
                 _hasProducedValue = true;
             }
             else if (_hasProducedValue)
             {
-                PublishNext(AvaloniaProperty.UnsetValue);
+                _observer?.OnNext(AvaloniaProperty.UnsetValue);
                 _hasProducedValue = false;
             }
         }

src/Avalonia.Base/Input/AccessKeyHandler.cs

@@ -65,14 +65,14 @@ namespace Avalonia.Input
             {
                 if (_mainMenu != null)
                 {
-                    _mainMenu.MenuClosed -= MainMenuClosed;
+                    _mainMenu.Closed -= MainMenuClosed;
                 }
 
                 _mainMenu = value;
 
                 if (_mainMenu != null)
                 {
-                    _mainMenu.MenuClosed += MainMenuClosed;
+                    _mainMenu.Closed += MainMenuClosed;
                 }
             }
         }

src/Avalonia.Base/Input/IMainMenu.cs

@@ -26,6 +26,6 @@ namespace Avalonia.Input
         /// <summary>
         /// Occurs when the main menu closes.
         /// </summary>
-        event EventHandler<RoutedEventArgs>? MenuClosed;
+        event EventHandler<RoutedEventArgs>? Closed;
     }
 }

src/Avalonia.Base/Reactive/SingleSubscriberObservableBase.cs

@@ -3,7 +3,7 @@ using Avalonia.Threading;
 
 namespace Avalonia.Reactive
 {
-    public abstract class SingleSubscriberObservableBase<T> : IObservable<T>, IDisposable
+    internal abstract class SingleSubscriberObservableBase<T> : IObservable<T>, IDisposable
     {
         private Exception? _error;
         private IObserver<T>? _observer;

src/Avalonia.Base/Rendering/Composition/Compositor.cs

@@ -66,16 +66,14 @@ namespace Avalonia.Rendering.Composition
         /// Creates a new compositor on a specified render loop that would use a particular GPU
         /// </summary>
         [PrivateApi]
-        public Compositor(IPlatformGraphics? gpu, bool useUiThreadForSynchronousCommits = false) 
+        public Compositor(IPlatformGraphics? gpu, bool useUiThreadForSynchronousCommits = false)
             : this(RenderLoop.LocatorAutoInstance, gpu, useUiThreadForSynchronousCommits)
         {
-            
         }
-        
-        internal Compositor(IRenderLoop loop, IPlatformGraphics? gpu, bool useUiThreadForSynchronousCommits = false) 
+
+        internal Compositor(IRenderLoop loop, IPlatformGraphics? gpu, bool useUiThreadForSynchronousCommits = false)
             : this(loop, gpu, useUiThreadForSynchronousCommits, MediaContext.Instance, false)
         {
-            
         }
 
         internal Compositor(IRenderLoop loop, IPlatformGraphics? gpu,

src/Avalonia.Controls/ContextMenu.cs

@@ -196,14 +196,14 @@ namespace Avalonia.Controls
         /// <see cref="P:Avalonia.Controls.ContextMenu.IsOpen" />
         /// property is changing from false to true.
         /// </summary>
-        public event CancelEventHandler? ContextMenuOpening;
+        public event CancelEventHandler? Opening;
 
         /// <summary>
         /// Occurs when the value of the
         /// <see cref="P:Avalonia.Controls.ContextMenu.IsOpen" />
         /// property is changing from true to false.
         /// </summary>
-        public event CancelEventHandler? ContextMenuClosing;
+        public event CancelEventHandler? Closing;
 
         /// <summary>
         /// Called when the <see cref="Control.ContextMenu"/> property changes on a control.
@@ -353,7 +353,7 @@ namespace Avalonia.Controls
 
             RaiseEvent(new RoutedEventArgs
             {
-                RoutedEvent = MenuOpenedEvent,
+                RoutedEvent = OpenedEvent,
                 Source = this,
             });
         }
@@ -394,7 +394,7 @@ namespace Avalonia.Controls
 
             RaiseEvent(new RoutedEventArgs
             {
-                RoutedEvent = MenuClosedEvent,
+                RoutedEvent = ClosedEvent,
                 Source = this,
             });
             
@@ -446,14 +446,14 @@ namespace Avalonia.Controls
         private bool CancelClosing()
         {
             var eventArgs = new CancelEventArgs();
-            ContextMenuClosing?.Invoke(this, eventArgs);
+            Closing?.Invoke(this, eventArgs);
             return eventArgs.Cancel;
         }
 
         private bool CancelOpening()
         {
             var eventArgs = new CancelEventArgs();
-            ContextMenuOpening?.Invoke(this, eventArgs);
+            Opening?.Invoke(this, eventArgs);
             return eventArgs.Cancel;
         }
     }

src/Avalonia.Controls/DateTimePickers/DatePickerPresenter.cs

@@ -367,11 +367,11 @@ namespace Avalonia.Controls
             var dt = Date;
             if (DayVisible)
             {
+                _daySelector.FormatDate = dt.Date;
                 var maxDays = _calendar.GetDaysInMonth(dt.Year, dt.Month);
                 _daySelector.MaximumValue = maxDays;
                 _daySelector.MinimumValue = 1;
                 _daySelector.SelectedValue = dt.Day;
-                _daySelector.FormatDate = dt.Date;
             }
 
             if (MonthVisible)

src/Avalonia.Controls/Embedding/Offscreen/OffscreenTopLevelImpl.cs

@@ -93,9 +93,9 @@ namespace Avalonia.Controls.Embedding.Offscreen
         public Action? LostFocus { get; set; }
         public abstract IMouseDevice MouseDevice { get; }
 
-        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel) { }
+        public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevel) { }
 
-        public WindowTransparencyLevel TransparencyLevel { get; private set; }
+        public WindowTransparencyLevel TransparencyLevel => WindowTransparencyLevel.None;
 
         public IPopupImpl? CreatePopup() => null;
         

src/Avalonia.Controls/ExperimentalAcrylicBorder.cs

@@ -56,22 +56,12 @@ namespace Avalonia.Controls
                 {
                     if (tl.PlatformImpl is null)
                         return;
-
-                    switch (x)
-                    {
-                        case WindowTransparencyLevel.Transparent:
-                        case WindowTransparencyLevel.None:
-                            Material.PlatformTransparencyCompensationLevel = tl.PlatformImpl.AcrylicCompensationLevels.TransparentLevel;
-                            break;
-
-                        case WindowTransparencyLevel.Blur:
-                            Material.PlatformTransparencyCompensationLevel = tl.PlatformImpl.AcrylicCompensationLevels.BlurLevel;
-                            break;
-
-                        case WindowTransparencyLevel.AcrylicBlur:
-                            Material.PlatformTransparencyCompensationLevel = tl.PlatformImpl.AcrylicCompensationLevels.AcrylicBlurLevel;
-                            break;
-                    }
+                    if (x == WindowTransparencyLevel.Transparent || x == WindowTransparencyLevel.None)
+                        Material.PlatformTransparencyCompensationLevel = tl.PlatformImpl.AcrylicCompensationLevels.TransparentLevel;
+                    else if (x == WindowTransparencyLevel.Blur)
+                        Material.PlatformTransparencyCompensationLevel = tl.PlatformImpl.AcrylicCompensationLevels.BlurLevel;
+                    else if (x == WindowTransparencyLevel.AcrylicBlur)
+                        Material.PlatformTransparencyCompensationLevel = tl.PlatformImpl.AcrylicCompensationLevels.AcrylicBlurLevel;
                 });
             UpdateMaterialSubscription();
         }

src/Avalonia.Controls/Menu.cs

@@ -60,7 +60,7 @@ namespace Avalonia.Controls
 
             RaiseEvent(new RoutedEventArgs
             {
-                RoutedEvent = MenuClosedEvent,
+                RoutedEvent = ClosedEvent,
                 Source = this,
             });
         }
@@ -77,7 +77,7 @@ namespace Avalonia.Controls
 
             RaiseEvent(new RoutedEventArgs
             {
-                RoutedEvent = MenuOpenedEvent,
+                RoutedEvent = OpenedEvent,
                 Source = this,
             });
         }

src/Avalonia.Controls/MenuBase.cs

@@ -25,16 +25,16 @@ namespace Avalonia.Controls
                 o => o.IsOpen);
 
         /// <summary>
-        /// Defines the <see cref="MenuOpened"/> event.
+        /// Defines the <see cref="Opened"/> event.
         /// </summary>
-        public static readonly RoutedEvent<RoutedEventArgs> MenuOpenedEvent =
-            RoutedEvent.Register<MenuBase, RoutedEventArgs>(nameof(MenuOpened), RoutingStrategies.Bubble);
+        public static readonly RoutedEvent<RoutedEventArgs> OpenedEvent =
+            RoutedEvent.Register<MenuBase, RoutedEventArgs>(nameof(Opened), RoutingStrategies.Bubble);
 
         /// <summary>
-        /// Defines the <see cref="MenuClosed"/> event.
+        /// Defines the <see cref="Closed"/> event.
         /// </summary>
-        public static readonly RoutedEvent<RoutedEventArgs> MenuClosedEvent =
-            RoutedEvent.Register<MenuBase, RoutedEventArgs>(nameof(MenuClosed), RoutingStrategies.Bubble);
+        public static readonly RoutedEvent<RoutedEventArgs> ClosedEvent =
+            RoutedEvent.Register<MenuBase, RoutedEventArgs>(nameof(Closed), RoutingStrategies.Bubble);
 
         private bool _isOpen;
 
@@ -68,8 +68,8 @@ namespace Avalonia.Controls
         /// </summary>
         public bool IsOpen
         {
-            get { return _isOpen; }
-            protected set { SetAndRaise(IsOpenProperty, ref _isOpen, value); }
+            get => _isOpen;
+            protected set => SetAndRaise(IsOpenProperty, ref _isOpen, value);
         }
 
         /// <inheritdoc/>
@@ -105,19 +105,19 @@ namespace Avalonia.Controls
         /// <summary>
         /// Occurs when a <see cref="Menu"/> is opened.
         /// </summary>
-        public event EventHandler<RoutedEventArgs>? MenuOpened
+        public event EventHandler<RoutedEventArgs>? Opened
         {
-            add { AddHandler(MenuOpenedEvent, value); }
-            remove { RemoveHandler(MenuOpenedEvent, value); }
+            add => AddHandler(OpenedEvent, value);
+            remove => RemoveHandler(OpenedEvent, value);
         }
 
         /// <summary>
         /// Occurs when a <see cref="Menu"/> is closed.
         /// </summary>
-        public event EventHandler<RoutedEventArgs>? MenuClosed
+        public event EventHandler<RoutedEventArgs>? Closed
         {
-            add { AddHandler(MenuClosedEvent, value); }
-            remove { RemoveHandler(MenuClosedEvent, value); }
+            add => AddHandler(ClosedEvent, value);
+            remove => RemoveHandler(ClosedEvent, value);
         }
 
         /// <summary>

src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs

@@ -290,7 +290,7 @@ namespace Avalonia.Controls.Platform
             Menu.PointerPressed += PointerPressed;
             Menu.PointerReleased += PointerReleased;
             Menu.AddHandler(AccessKeyHandler.AccessKeyPressedEvent, AccessKeyPressed);
-            Menu.AddHandler(MenuBase.MenuOpenedEvent, MenuOpened);
+            Menu.AddHandler(MenuBase.OpenedEvent, MenuOpened);
             Menu.AddHandler(MenuItem.PointerEnteredItemEvent, PointerEntered);
             Menu.AddHandler(MenuItem.PointerExitedItemEvent, PointerExited);
             Menu.AddHandler(InputElement.PointerMovedEvent, PointerMoved);
@@ -326,7 +326,7 @@ namespace Avalonia.Controls.Platform
             Menu.PointerPressed -= PointerPressed;
             Menu.PointerReleased -= PointerReleased;
             Menu.RemoveHandler(AccessKeyHandler.AccessKeyPressedEvent, AccessKeyPressed);
-            Menu.RemoveHandler(MenuBase.MenuOpenedEvent, MenuOpened);
+            Menu.RemoveHandler(MenuBase.OpenedEvent, MenuOpened);
             Menu.RemoveHandler(MenuItem.PointerEnteredItemEvent, PointerEntered);
             Menu.RemoveHandler(MenuItem.PointerExitedItemEvent, PointerExited);
             Menu.RemoveHandler(InputElement.PointerMovedEvent, PointerMoved);

src/Avalonia.Controls/Platform/ITopLevelImpl.cs

@@ -117,7 +117,7 @@ namespace Avalonia.Platform
         /// <summary>
         /// Sets the <see cref="WindowTransparencyLevel"/> hint of the TopLevel.
         /// </summary>
-        void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel);
+        void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevels);
 
         /// <summary>
         /// Gets the current <see cref="WindowTransparencyLevel"/> of the TopLevel.

src/Avalonia.Controls/Primitives/LightDismissOverlayLayer.cs

@@ -46,13 +46,12 @@ namespace Avalonia.Controls.Primitives
             return manager?.LightDismissOverlayLayer;
         }
 
+        /// <inheritdoc />
         public bool HitTest(Point point)
         {
             if (InputPassThroughElement is Visual v)
             {
-                var hit = ((Visual?)VisualRoot)?.GetVisualAt(point, x => x != this);
-
-                if (hit is object)
+                if (VisualRoot is IInputElement ie && ie.InputHitTest(point, x => x != this) is Visual hit)
                 {
                     return !v.IsVisualAncestorOf(hit);
                 }

src/Avalonia.Controls/ProgressBar.cs

@@ -31,77 +31,157 @@ namespace Avalonia.Controls
             private double _containerAnimationEndPosition;
             private double _container2AnimationStartPosition;
             private double _container2AnimationEndPosition;
-
-            public static readonly DirectProperty<ProgressBarTemplateSettings, double> ContainerAnimationStartPositionProperty =
-           AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
-               nameof(ContainerAnimationStartPosition),
-               p => p.ContainerAnimationStartPosition,
-               (p, o) => p.ContainerAnimationStartPosition = o, 0d);
-
-            public static readonly DirectProperty<ProgressBarTemplateSettings, double> ContainerAnimationEndPositionProperty =
-                AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
-                    nameof(ContainerAnimationEndPosition),
-                    p => p.ContainerAnimationEndPosition,
-                    (p, o) => p.ContainerAnimationEndPosition = o, 0d);
-
-            public static readonly DirectProperty<ProgressBarTemplateSettings, double> Container2AnimationStartPositionProperty =
-                AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
-                    nameof(Container2AnimationStartPosition),
-                    p => p.Container2AnimationStartPosition,
-                    (p, o) => p.Container2AnimationStartPosition = o, 0d);
-
-            public static readonly DirectProperty<ProgressBarTemplateSettings, double> Container2AnimationEndPositionProperty =
-                AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
-                    nameof(Container2AnimationEndPosition),
-                    p => p.Container2AnimationEndPosition,
-                    (p, o) => p.Container2AnimationEndPosition = o);
-
+            private double _indeterminateStartingOffset;
+            private double _indeterminateEndingOffset;
+
+            /// <summary>
+            /// Defines the <see cref="ContainerAnimationStartPosition"/> property.
+            /// </summary>
+            public static readonly DirectProperty<ProgressBarTemplateSettings, double>
+                ContainerAnimationStartPositionProperty =
+                    AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
+                        nameof(ContainerAnimationStartPosition),
+                        p => p.ContainerAnimationStartPosition,
+                        (p, o) => p.ContainerAnimationStartPosition = o);
+
+            /// <summary>
+            /// Defines the <see cref="ContainerAnimationEndPosition"/> property.
+            /// </summary>
+            public static readonly DirectProperty<ProgressBarTemplateSettings, double>
+                ContainerAnimationEndPositionProperty =
+                    AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
+                        nameof(ContainerAnimationEndPosition),
+                        p => p.ContainerAnimationEndPosition,
+                        (p, o) => p.ContainerAnimationEndPosition = o);
+
+            /// <summary>
+            /// Defines the <see cref="Container2AnimationStartPosition"/> property.
+            /// </summary>
+            public static readonly DirectProperty<ProgressBarTemplateSettings, double>
+                Container2AnimationStartPositionProperty =
+                    AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
+                        nameof(Container2AnimationStartPosition),
+                        p => p.Container2AnimationStartPosition,
+                        (p, o) => p.Container2AnimationStartPosition = o);
+
+            /// <summary>
+            /// Defines the <see cref="Container2AnimationEndPosition"/> property.
+            /// </summary>
+            public static readonly DirectProperty<ProgressBarTemplateSettings, double>
+                Container2AnimationEndPositionProperty =
+                    AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
+                        nameof(Container2AnimationEndPosition),
+                        p => p.Container2AnimationEndPosition,
+                        (p, o) => p.Container2AnimationEndPosition = o);
+
+            /// <summary>
+            /// Defines the <see cref="Container2Width"/> property.
+            /// </summary>
             public static readonly DirectProperty<ProgressBarTemplateSettings, double> Container2WidthProperty =
                 AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
                     nameof(Container2Width),
                     p => p.Container2Width,
                     (p, o) => p.Container2Width = o);
 
+            /// <summary>
+            /// Defines the <see cref="ContainerWidth"/> property.
+            /// </summary>
             public static readonly DirectProperty<ProgressBarTemplateSettings, double> ContainerWidthProperty =
                 AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
                     nameof(ContainerWidth),
                     p => p.ContainerWidth,
                     (p, o) => p.ContainerWidth = o);
 
+            /// <summary>
+            /// Defines the <see cref="IndeterminateStartingOffset"/> property.
+            /// </summary>
+            public static readonly DirectProperty<ProgressBarTemplateSettings, double> IndeterminateStartingOffsetProperty =
+                AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
+                    nameof(IndeterminateStartingOffset),
+                    p => p.IndeterminateStartingOffset,
+                    (p, o) => p.IndeterminateStartingOffset = o);
+            
+            /// <summary>
+            /// Defines the <see cref="IndeterminateEndingOffset"/> property.
+            /// </summary>
+            public static readonly DirectProperty<ProgressBarTemplateSettings, double> IndeterminateEndingOffsetProperty =
+                AvaloniaProperty.RegisterDirect<ProgressBarTemplateSettings, double>(
+                    nameof(IndeterminateEndingOffset),
+                    p => p.IndeterminateEndingOffset,
+                    (p, o) => p.IndeterminateEndingOffset = o);
+
+            /// <summary>
+            /// Used by <see cref="Avalonia.Themes.Fluent"/> to define the first indeterminate indicator's width.
+            /// </summary>
+            public double ContainerWidth
+            {
+                get => _containerWidth;
+                set => SetAndRaise(ContainerWidthProperty, ref _containerWidth, value);
+            }
+            
+            /// <summary>
+            /// Used by <see cref="Avalonia.Themes.Fluent"/> to define the second indeterminate indicator's width.
+            /// </summary>
+            public double Container2Width
+            {
+                get => _container2Width;
+                set => SetAndRaise(Container2WidthProperty, ref _container2Width, value);
+            }
+
+            /// <summary>
+            /// Used by <see cref="Avalonia.Themes.Fluent"/> to define the first indeterminate indicator's start position when animated.
+            /// </summary>
             public double ContainerAnimationStartPosition
             {
                 get => _containerAnimationStartPosition;
-                set => SetAndRaise(ContainerAnimationStartPositionProperty, ref _containerAnimationStartPosition, value);
+                set => SetAndRaise(ContainerAnimationStartPositionProperty, ref _containerAnimationStartPosition,
+                    value);
             }
 
+            /// <summary>
+            /// Used by <see cref="Avalonia.Themes.Fluent"/> to define the first indeterminate indicator's end position when animated.
+            /// </summary>
             public double ContainerAnimationEndPosition
             {
                 get => _containerAnimationEndPosition;
                 set => SetAndRaise(ContainerAnimationEndPositionProperty, ref _containerAnimationEndPosition, value);
             }
 
+            /// <summary>
+            /// Used by <see cref="Avalonia.Themes.Fluent"/> to define the second indeterminate indicator's start position when animated.
+            /// </summary>
             public double Container2AnimationStartPosition
             {
                 get => _container2AnimationStartPosition;
-                set => SetAndRaise(Container2AnimationStartPositionProperty, ref _container2AnimationStartPosition, value);
+                set => SetAndRaise(Container2AnimationStartPositionProperty, ref _container2AnimationStartPosition,
+                    value);
             }
-
-            public double Container2Width
+            
+            /// <summary>
+            /// Used by <see cref="Avalonia.Themes.Fluent"/> to define the second indeterminate indicator's end position when animated.
+            /// </summary>
+            public double Container2AnimationEndPosition
             {
-                get => _container2Width;
-                set => SetAndRaise(Container2WidthProperty, ref _container2Width, value);
+                get => _container2AnimationEndPosition;
+                set => SetAndRaise(Container2AnimationEndPositionProperty, ref _container2AnimationEndPosition, value);
             }
 
-            public double ContainerWidth
+            /// <summary>
+            /// Used by <see cref="Avalonia.Themes.Simple"/>  to define the starting point of its indeterminate animation.
+            /// </summary>
+            public double IndeterminateStartingOffset
             {
-                get => _containerWidth;
-                set => SetAndRaise(ContainerWidthProperty, ref _containerWidth, value);
+                get => _indeterminateStartingOffset;
+                set => SetAndRaise(IndeterminateStartingOffsetProperty, ref _indeterminateStartingOffset, value);
             }
-
-            public double Container2AnimationEndPosition
+            
+            /// <summary>
+            /// Used by <see cref="Avalonia.Themes.Simple"/> to define the ending point of its indeterminate animation.
+            /// </summary>
+            public double IndeterminateEndingOffset
             {
-                get => _container2AnimationEndPosition;
-                set => SetAndRaise(Container2AnimationEndPositionProperty, ref _container2AnimationEndPosition, value);
+                get => _indeterminateEndingOffset;
+                set => SetAndRaise(IndeterminateEndingOffsetProperty, ref _indeterminateEndingOffset, value);
             }
         }
 
@@ -131,7 +211,7 @@ namespace Avalonia.Controls
         /// Defines the <see cref="Orientation"/> property.
         /// </summary>
         public static readonly StyledProperty<Orientation> OrientationProperty =
-            AvaloniaProperty.Register<ProgressBar, Orientation>(nameof(Orientation), Orientation.Horizontal);
+            AvaloniaProperty.Register<ProgressBar, Orientation>(nameof(Orientation));
 
         /// <summary>
         /// Defines the <see cref="Percentage"/> property.
@@ -141,18 +221,6 @@ namespace Avalonia.Controls
                 nameof(Percentage),
                 o => o.Percentage);
 
-        /// <summary>
-        /// Defines the <see cref="IndeterminateStartingOffset"/> property.
-        /// </summary>
-        public static readonly StyledProperty<double> IndeterminateStartingOffsetProperty =
-            AvaloniaProperty.Register<ProgressBar, double>(nameof(IndeterminateStartingOffset));
-
-        /// <summary>
-        /// Defines the <see cref="IndeterminateEndingOffset"/> property.
-        /// </summary>
-        public static readonly StyledProperty<double> IndeterminateEndingOffsetProperty =
-            AvaloniaProperty.Register<ProgressBar, double>(nameof(IndeterminateEndingOffset));
-
         /// <summary>
         /// Gets the overall percentage complete of the progress 
         /// </summary>
@@ -162,30 +230,13 @@ namespace Avalonia.Controls
         /// </remarks>
         public double Percentage
         {
-            get { return _percentage; }
+            get => _percentage;
             private set { SetAndRaise(PercentageProperty, ref _percentage, value); }
         }
 
-        public double IndeterminateStartingOffset
-        {
-            get => GetValue(IndeterminateStartingOffsetProperty);
-            set => SetValue(IndeterminateStartingOffsetProperty, value);
-        }
-
-        public double IndeterminateEndingOffset
-        {
-            get => GetValue(IndeterminateEndingOffsetProperty);
-            set => SetValue(IndeterminateEndingOffsetProperty, value);
-        }
-
         static ProgressBar()
         {
             ValueProperty.OverrideMetadata<ProgressBar>(new(defaultBindingMode: BindingMode.OneWay));
-            ValueProperty.Changed.AddClassHandler<ProgressBar>((x, e) => x.UpdateIndicatorWhenPropChanged(e));
-            MinimumProperty.Changed.AddClassHandler<ProgressBar>((x, e) => x.UpdateIndicatorWhenPropChanged(e));
-            MaximumProperty.Changed.AddClassHandler<ProgressBar>((x, e) => x.UpdateIndicatorWhenPropChanged(e));
-            IsIndeterminateProperty.Changed.AddClassHandler<ProgressBar>((x, e) => x.UpdateIndicatorWhenPropChanged(e));
-            OrientationProperty.Changed.AddClassHandler<ProgressBar>((x, e) => x.UpdateIndicatorWhenPropChanged(e));
         }
 
         /// <summary>
@@ -251,6 +302,15 @@ namespace Avalonia.Controls
         {
             base.OnPropertyChanged(change);
 
+            if (change.Property == ValueProperty ||
+                change.Property == MinimumProperty ||
+                change.Property == MaximumProperty ||
+                change.Property == IsIndeterminateProperty ||
+                change.Property == OrientationProperty)
+            {
+                UpdateIndicator();
+            }
+
             if (change.Property == IsIndeterminateProperty)
             {
                 UpdatePseudoClasses(change.GetNewValue<bool>(), null);
@@ -286,64 +346,50 @@ namespace Avalonia.Controls
             // Gets the size of the parent indicator container
             var barSize = _indicator?.VisualParent?.Bounds.Size ?? Bounds.Size;
 
-            if (_indicator != null)
+            if (_indicator == null) return;
+            if (IsIndeterminate)
             {
-                if (IsIndeterminate)
-                {
-                    // Pulled from ModernWPF.
+                // Pulled from ModernWPF.
 
-                    var dim = Orientation == Orientation.Horizontal ? barSize.Width : barSize.Height;
-                    var barIndicatorWidth = dim * 0.4; // Indicator width at 40% of ProgressBar
-                    var barIndicatorWidth2 = dim * 0.6; // Indicator width at 60% of ProgressBar
+                var dim = Orientation == Orientation.Horizontal ? barSize.Width : barSize.Height;
+                var barIndicatorWidth = dim * 0.4; // Indicator width at 40% of ProgressBar
+                var barIndicatorWidth2 = dim * 0.6; // Indicator width at 60% of ProgressBar
 
-                    TemplateSettings.ContainerWidth = barIndicatorWidth;
-                    TemplateSettings.Container2Width = barIndicatorWidth2;
+                TemplateSettings.ContainerWidth = barIndicatorWidth;
+                TemplateSettings.Container2Width = barIndicatorWidth2;
 
-                    TemplateSettings.ContainerAnimationStartPosition = barIndicatorWidth * -1.8; // Position at -180%
-                    TemplateSettings.ContainerAnimationEndPosition = barIndicatorWidth * 3.0; // Position at 300%
+                TemplateSettings.ContainerAnimationStartPosition = barIndicatorWidth * -1.8; // Position at -180%
+                TemplateSettings.ContainerAnimationEndPosition = barIndicatorWidth * 3.0; // Position at 300%
 
-                    TemplateSettings.Container2AnimationStartPosition = barIndicatorWidth2 * -1.5; // Position at -150%
-                    TemplateSettings.Container2AnimationEndPosition = barIndicatorWidth2 * 1.66; // Position at 166%
+                TemplateSettings.Container2AnimationStartPosition = barIndicatorWidth2 * -1.5; // Position at -150%
+                TemplateSettings.Container2AnimationEndPosition = barIndicatorWidth2 * 1.66; // Position at 166%
 
-                    // Remove these properties when we switch to fluent as default and removed the old one.
-                    SetCurrentValue(IndeterminateStartingOffsetProperty,-dim);
-                    SetCurrentValue(IndeterminateEndingOffsetProperty,dim);
+                TemplateSettings.IndeterminateStartingOffset = -dim;
+                TemplateSettings.IndeterminateEndingOffset = dim;
+            }
+            else
+            {
+                var percent = Math.Abs(Maximum - Minimum) < double.Epsilon ?
+                    1.0 :
+                    (Value - Minimum) / (Maximum - Minimum);
 
-                    var padding = Padding;
-                    var rectangle = new RectangleGeometry(
-                        new Rect(
-                            padding.Left,
-                            padding.Top,
-                            barSize.Width - (padding.Right + padding.Left),
-                            barSize.Height - (padding.Bottom + padding.Top)
-                            ));
+                // When the Orientation changed, the indicator's Width or Height should set to double.NaN.
+                // Indicator size calculation should consider the ProgressBar's Padding property setting
+                if (Orientation == Orientation.Horizontal)
+                {
+                    _indicator.Width = (barSize.Width - _indicator.Margin.Left - _indicator.Margin.Right) * percent;
+                    _indicator.Height = double.NaN;
                 }
                 else
                 {
-                    double percent = Maximum == Minimum ? 1.0 : (Value - Minimum) / (Maximum - Minimum);
-
-                    // When the Orientation changed, the indicator's Width or Height should set to double.NaN.
-                    // Indicator size calculation should consider the ProgressBar's Padding property setting
-                    if (Orientation == Orientation.Horizontal)
-                    {
-                        _indicator.Width = (barSize.Width - _indicator.Margin.Left - _indicator.Margin.Right) * percent;
-                        _indicator.Height = double.NaN;
-                    }
-                    else
-                    {
-                        _indicator.Width = double.NaN;
-                        _indicator.Height = (barSize.Height - _indicator.Margin.Top - _indicator.Margin.Bottom) * percent;
-                    }
-
-
-                    Percentage = percent * 100;
+                    _indicator.Width = double.NaN;
+                    _indicator.Height = (barSize.Height - _indicator.Margin.Top - _indicator.Margin.Bottom) *
+                                        percent;
                 }
-            }
-        }
 
-        private void UpdateIndicatorWhenPropChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            UpdateIndicator();
+
+                Percentage = percent * 100;
+            }
         }
 
         private void UpdatePseudoClasses(
@@ -355,11 +401,9 @@ namespace Avalonia.Controls
                 PseudoClasses.Set(":indeterminate", isIndeterminate.Value);
             }
 
-            if (o.HasValue)
-            {
-                PseudoClasses.Set(":vertical", o == Orientation.Vertical);
-                PseudoClasses.Set(":horizontal", o == Orientation.Horizontal);
-            }
+            if (!o.HasValue) return;
+            PseudoClasses.Set(":vertical", o == Orientation.Vertical);
+            PseudoClasses.Set(":horizontal", o == Orientation.Horizontal);
         }
     }
 }

src/Avalonia.Controls/TopLevel.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics;
 using Avalonia.Reactive;
@@ -22,6 +23,7 @@ using Avalonia.Utilities;
 using Avalonia.Input.Platform;
 using System.Linq;
 using System.Threading.Tasks;
+using Avalonia.Metadata;
 using Avalonia.Rendering.Composition;
 
 namespace Avalonia.Controls
@@ -65,8 +67,8 @@ namespace Avalonia.Controls
         /// <summary>
         /// Defines the <see cref="TransparencyLevelHint"/> property.
         /// </summary>
-        public static readonly StyledProperty<WindowTransparencyLevel> TransparencyLevelHintProperty =
-            AvaloniaProperty.Register<TopLevel, WindowTransparencyLevel>(nameof(TransparencyLevelHint), WindowTransparencyLevel.None);
+        public static readonly StyledProperty<IReadOnlyList<WindowTransparencyLevel>> TransparencyLevelHintProperty =
+            AvaloniaProperty.Register<TopLevel, IReadOnlyList<WindowTransparencyLevel>>(nameof(TransparencyLevelHint), Array.Empty<WindowTransparencyLevel>());
 
         /// <summary>
         /// Defines the <see cref="ActualTransparencyLevel"/> property.
@@ -173,7 +175,7 @@ namespace Avalonia.Controls
             PlatformImpl = impl ?? throw new InvalidOperationException(
                 "Could not create window implementation: maybe no windowing subsystem was initialized?");
 
-            _actualTransparencyLevel = PlatformImpl.TransparencyLevel;            
+            _actualTransparencyLevel = PlatformImpl.TransparencyLevel;
 
             dependencyResolver ??= AvaloniaLocator.Current;
 
@@ -311,8 +313,11 @@ namespace Avalonia.Controls
 
         /// <summary>
         /// Gets or sets the <see cref="WindowTransparencyLevel"/> that the TopLevel should use when possible.
+        /// Accepts multiple values which are applied in a fallback order.
+        /// For instance, with "Mica, Blur" Mica will be applied only on platforms where it is possible,
+        /// and Blur will be used on the rest of them. Default value is an empty array or "None".    
         /// </summary>
-        public WindowTransparencyLevel TransparencyLevelHint
+        public IReadOnlyList<WindowTransparencyLevel> TransparencyLevelHint
         {
             get { return GetValue(TransparencyLevelHintProperty); }
             set { SetValue(TransparencyLevelHintProperty, value); }
@@ -536,8 +541,8 @@ namespace Avalonia.Controls
             {
                 if (PlatformImpl != null)
                 {
-                    PlatformImpl.SetTransparencyLevelHint(change.GetNewValue<WindowTransparencyLevel>());
-                    HandleTransparencyLevelChanged(PlatformImpl.TransparencyLevel);
+                    PlatformImpl.SetTransparencyLevelHint(
+                        change.GetNewValue<IReadOnlyList<WindowTransparencyLevel>>() ?? Array.Empty<WindowTransparencyLevel>());
                 }
             }
             else if (change.Property == ActualThemeVariantProperty)
@@ -632,27 +637,11 @@ namespace Avalonia.Controls
             ScalingChanged?.Invoke(this, EventArgs.Empty);
         }
 
-        private static bool TransparencyLevelsMatch (WindowTransparencyLevel requested, WindowTransparencyLevel received)
-        {
-            if(requested == received)
-            {
-                return true;
-            }
-            else if(requested >= WindowTransparencyLevel.Blur && received >= WindowTransparencyLevel.Blur)
-            {
-                return true;
-            }
-
-            return false;
-        }
-
         private void HandleTransparencyLevelChanged(WindowTransparencyLevel transparencyLevel)
         {
-            if(_transparencyFallbackBorder != null)
+            if (_transparencyFallbackBorder != null)
             {
-                if(transparencyLevel == WindowTransparencyLevel.None || 
-                    TransparencyLevelHint == WindowTransparencyLevel.None || 
-                    !TransparencyLevelsMatch(TransparencyLevelHint, transparencyLevel))
+                if (transparencyLevel == WindowTransparencyLevel.None)
                 {
                     _transparencyFallbackBorder.Background = TransparencyBackgroundFallback;
                 }
@@ -682,7 +671,6 @@ namespace Avalonia.Controls
                 return;
 
             _transparencyFallbackBorder = e.NameScope.Find<Border>("PART_TransparencyFallback");
-
             HandleTransparencyLevelChanged(PlatformImpl.TransparencyLevel);
         }
 

src/Avalonia.Controls/WindowTransparencyLevel.cs

@@ -1,35 +1,51 @@
-namespace Avalonia.Controls
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+
+namespace Avalonia.Controls;
+
+public readonly record struct WindowTransparencyLevel
 {
-    public enum WindowTransparencyLevel
+    private readonly string _value;
+
+    private WindowTransparencyLevel(string value)
     {
-        /// <summary>
-        /// The window background is Black where nothing is drawn in the window.
-        /// </summary>
-        None,
-
-        /// <summary>
-        /// The window background is Transparent where nothing is drawn in the window.
-        /// </summary>
-        Transparent,
-
-        /// <summary>
-        /// The window background is a blur-behind where nothing is drawn in the window.
-        /// </summary>
-        Blur,
-
-        /// <summary>
-        /// The window background is a blur-behind with a high blur radius. This level may fallback to Blur.
-        /// </summary>
-        AcrylicBlur,
-        
-        /// <summary>
-        /// Force acrylic on some incompatible versions of Windows 10. 
-        /// </summary>
-        ForceAcrylicBlur,
-        
-        /// <summary>
-        /// The window background is based on desktop wallpaper tint with a blur. This will only work on Windows 11 
-        /// </summary>
-        Mica
+        _value = value;
+    }
+
+    /// <summary>
+    /// The window background is Black where nothing is drawn in the window.
+    /// </summary>
+    public static WindowTransparencyLevel None { get; } = new(nameof(None));
+
+    /// <summary>
+    /// The window background is Transparent where nothing is drawn in the window.
+    /// </summary>
+    public static WindowTransparencyLevel Transparent { get; } = new(nameof(Transparent));
+
+    /// <summary>
+    /// The window background is a blur-behind where nothing is drawn in the window.
+    /// </summary>
+    public static WindowTransparencyLevel Blur { get; } = new(nameof(Blur));
+
+    /// <summary>
+    /// The window background is a blur-behind with a high blur radius. This level may fallback to Blur.
+    /// </summary>
+    public static WindowTransparencyLevel AcrylicBlur { get; } = new(nameof(AcrylicBlur));
+
+    /// <summary>
+    /// The window background is based on desktop wallpaper tint with a blur. This will only work on Windows 11 
+    /// </summary>
+    public static WindowTransparencyLevel Mica { get; } = new(nameof(Mica));
+
+    public override string ToString()
+    {
+        return _value;
     }
 }
+
+public class WindowTransparencyLevelCollection : ReadOnlyCollection<WindowTransparencyLevel>
+{
+    public WindowTransparencyLevelCollection(IList<WindowTransparencyLevel> list) : base(list)
+    {
+    }
+} 

src/Avalonia.DesignerSupport/Remote/Stubs.cs

@@ -177,13 +177,13 @@ namespace Avalonia.DesignerSupport.Remote
 
         public Action GotInputWhenDisabled { get; set; }
 
-        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel) { }
+        public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevel) { }
 
         public void SetWindowManagerAddShadowHint(bool enabled)
         {
         }
 
-        public WindowTransparencyLevel TransparencyLevel { get; private set; }
+        public WindowTransparencyLevel TransparencyLevel => WindowTransparencyLevel.None;
 
         public bool IsClientAreaExtendedToDecorations { get; }
 

src/Avalonia.Native/WindowImplBase.cs

@@ -65,6 +65,7 @@ namespace Avalonia.Native
         private NativeControlHostImpl _nativeControlHost;
         private IStorageProvider _storageProvider;
         private PlatformBehaviorInhibition _platformBehaviorInhibition;
+        private WindowTransparencyLevel _transparencyLevel = WindowTransparencyLevel.None;
 
         internal WindowBaseImpl(IAvaloniaNativeFactory factory, AvaloniaNativePlatformOptions opts,
             AvaloniaNativeGlPlatformGraphics glFeature)
@@ -479,26 +480,47 @@ namespace Avalonia.Native
             _native?.BeginDragAndDropOperation(effects, point, clipboard, callback, sourceHandle);
         }
 
-        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel) 
+        public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevels) 
         {
-            if (TransparencyLevel != transparencyLevel)
+            foreach (var level in transparencyLevels)
             {
-                if (transparencyLevel > WindowTransparencyLevel.Transparent)
-                    transparencyLevel = WindowTransparencyLevel.AcrylicBlur;
+                AvnWindowTransparencyMode? mode = null;
 
-                TransparencyLevel = transparencyLevel;
+                if (level == WindowTransparencyLevel.None)
+                    mode = AvnWindowTransparencyMode.Opaque;
+                if (level == WindowTransparencyLevel.Transparent)
+                    mode = AvnWindowTransparencyMode.Transparent;
+                else if (level == WindowTransparencyLevel.AcrylicBlur)
+                    mode = AvnWindowTransparencyMode.Blur;
 
-                _native.SetTransparencyMode(transparencyLevel == WindowTransparencyLevel.None
-                    ? AvnWindowTransparencyMode.Opaque 
-                    : transparencyLevel == WindowTransparencyLevel.Transparent 
-                        ? AvnWindowTransparencyMode.Transparent
-                        : AvnWindowTransparencyMode.Blur);
+                if (mode.HasValue && level != TransparencyLevel)
+                {
+                    _native?.SetTransparencyMode(mode.Value);
+                    TransparencyLevel = level;
+                    return;
+                }
+            }
 
-                TransparencyLevelChanged?.Invoke(TransparencyLevel);
+            // If we get here, we didn't find a supported level. Use the default of None.
+            if (TransparencyLevel != WindowTransparencyLevel.None)
+            {
+                _native?.SetTransparencyMode(AvnWindowTransparencyMode.Opaque);
+                TransparencyLevel = WindowTransparencyLevel.None;
             }
         }
 
-        public WindowTransparencyLevel TransparencyLevel { get; private set; } = WindowTransparencyLevel.None;
+        public WindowTransparencyLevel TransparencyLevel
+        {
+            get => _transparencyLevel;
+            private set
+            {
+                if (_transparencyLevel != value)
+                {
+                    _transparencyLevel = value;
+                    TransparencyLevelChanged?.Invoke(value);
+                }
+            }
+        }
 
         public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
         {

src/Avalonia.Themes.Simple/Controls/ProgressBar.xaml

@@ -87,10 +87,10 @@
                    IterationCount="Infinite"
                    Duration="0:0:3">
           <KeyFrame Cue="0%">
-            <Setter Property="TranslateTransform.X" Value="{Binding IndeterminateStartingOffset, RelativeSource={RelativeSource TemplatedParent}}" />
+            <Setter Property="TranslateTransform.X" Value="{Binding $parent[ProgressBar].TemplateSettings.IndeterminateStartingOffset}" />
           </KeyFrame>
           <KeyFrame Cue="100%">
-            <Setter Property="TranslateTransform.X" Value="{Binding IndeterminateEndingOffset, RelativeSource={RelativeSource TemplatedParent}}" />
+            <Setter Property="TranslateTransform.X" Value="{Binding $parent[ProgressBar].TemplateSettings.IndeterminateEndingOffset}" />
           </KeyFrame>
         </Animation>
       </Style.Animations>
@@ -102,10 +102,10 @@
                    IterationCount="Infinite"
                    Duration="0:0:3">
           <KeyFrame Cue="0%">
-            <Setter Property="TranslateTransform.Y" Value="{Binding IndeterminateStartingOffset, RelativeSource={RelativeSource TemplatedParent}}" />
+            <Setter Property="TranslateTransform.Y" Value="{Binding $parent[ProgressBar].TemplateSettings.IndeterminateStartingOffset}" />
           </KeyFrame>
           <KeyFrame Cue="100%">
-            <Setter Property="TranslateTransform.Y" Value="{Binding IndeterminateEndingOffset, RelativeSource={RelativeSource TemplatedParent}}" />
+            <Setter Property="TranslateTransform.Y" Value="{Binding $parent[ProgressBar].TemplateSettings.IndeterminateEndingOffset}" />
           </KeyFrame>
         </Animation>
       </Style.Animations>

src/Avalonia.X11/TransparencyHelper.cs

@@ -1,6 +1,9 @@
 using System;
+using System.Collections.Generic;
 using Avalonia.Controls;
 
+#nullable enable
+
 namespace Avalonia.X11
 {
     internal class TransparencyHelper :  IDisposable, X11Globals.IGlobalsSubscriber
@@ -9,11 +12,23 @@ namespace Avalonia.X11
         private readonly IntPtr _window;
         private readonly X11Globals _globals;
         private WindowTransparencyLevel _currentLevel;
-        private WindowTransparencyLevel _requestedLevel;
+        private IReadOnlyList<WindowTransparencyLevel>? _requestedLevels;
         private bool _blurAtomsAreSet;
         
-        public Action<WindowTransparencyLevel> TransparencyLevelChanged { get; set; }
-        public WindowTransparencyLevel CurrentLevel => _currentLevel;
+        public Action<WindowTransparencyLevel>? TransparencyLevelChanged { get; set; }
+        
+        public WindowTransparencyLevel CurrentLevel
+        {
+            get => _currentLevel;
+            set
+            {
+                if (_currentLevel != value)
+                {
+                    _currentLevel = value;
+                    TransparencyLevelChanged?.Invoke(value);
+                }
+            }
+        }
 
         public TransparencyHelper(X11Info x11, IntPtr window, X11Globals globals)
         {
@@ -23,25 +38,53 @@ namespace Avalonia.X11
             _globals.AddSubscriber(this);
         }
 
-        public void SetTransparencyRequest(WindowTransparencyLevel level)
+        public void SetTransparencyRequest(IReadOnlyList<WindowTransparencyLevel> levels)
+        {
+            _requestedLevels = levels;
+
+            foreach (var level in levels)
+            {
+                if (!IsSupported(level))
+                    continue;
+
+                SetBlur(level == WindowTransparencyLevel.Blur);
+                CurrentLevel = level;
+                return;
+            }
+
+            // If we get here, we didn't find a supported level. Use the defualt of Transparent or
+            // None, depending on whether composition is enabled.
+            SetBlur(false);
+            CurrentLevel = _globals.IsCompositionEnabled ?
+                WindowTransparencyLevel.Transparent :
+                WindowTransparencyLevel.None;
+        }
+
+        private bool IsSupported(WindowTransparencyLevel level)
         {
-            _requestedLevel = level;
-            UpdateTransparency();
+            // None is suppported when composition is disabled.
+            if (level == WindowTransparencyLevel.None)
+                return !_globals.IsCompositionEnabled;
+
+            // Transparent is suppported when composition is enabled.
+            if (level == WindowTransparencyLevel.Transparent)
+                return _globals.IsCompositionEnabled;
+
+            // Blur is supported when composition is enabled and KWin is used.
+            if (level == WindowTransparencyLevel.Blur)
+                return _globals.IsCompositionEnabled && _globals.WmName == "KWin";
+            
+            return false;
         }
 
         private void UpdateTransparency()
         {
-            var newLevel = UpdateAtomsAndGetTransparency();
-            if (newLevel != _currentLevel)
-            {
-                _currentLevel = newLevel;
-                TransparencyLevelChanged?.Invoke(newLevel);
-            }
+            SetTransparencyRequest(_requestedLevels ?? Array.Empty<WindowTransparencyLevel>());
         }
-        
-        private WindowTransparencyLevel UpdateAtomsAndGetTransparency()
+
+        private void SetBlur(bool blur)
         {
-            if (_requestedLevel >= WindowTransparencyLevel.Blur)
+            if (blur)
             {
                 if (!_blurAtomsAreSet)
                 {
@@ -59,15 +102,7 @@ namespace Avalonia.X11
                     _blurAtomsAreSet = false;
                 }
             }
-
-            if (!_globals.IsCompositionEnabled)
-                return WindowTransparencyLevel.None;
-            if (_requestedLevel >= WindowTransparencyLevel.Blur && CanBlur)
-                return WindowTransparencyLevel.Blur;
-            return WindowTransparencyLevel.Transparent;
         }
-
-        private bool CanBlur => _globals.WmName == "KWin" && _globals.IsCompositionEnabled;
         
         public void Dispose()
         {

src/Avalonia.X11/X11Window.cs

@@ -196,7 +196,7 @@ namespace Avalonia.X11
             _rawEventGrouper = new RawEventGrouper(DispatchInput, platform.EventGrouperDispatchQueue);
             
             _transparencyHelper = new TransparencyHelper(_x11, _handle, platform.Globals);
-            _transparencyHelper.SetTransparencyRequest(WindowTransparencyLevel.None);
+            _transparencyHelper.SetTransparencyRequest(Array.Empty<WindowTransparencyLevel>());
 
             CreateIC();
 
@@ -1306,8 +1306,10 @@ namespace Avalonia.X11
 
         public IPopupPositioner? PopupPositioner { get; }
 
-        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel) =>
-            _transparencyHelper?.SetTransparencyRequest(transparencyLevel);
+        public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevels)
+        {
+            _transparencyHelper?.SetTransparencyRequest(transparencyLevels);
+        }
 
         public void SetWindowManagerAddShadowHint(bool enabled)
         {

src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs

@@ -39,7 +39,6 @@ namespace Avalonia.Browser
         {
             Surfaces = Enumerable.Empty<object>();
             _avaloniaView = avaloniaView;
-            TransparencyLevel = WindowTransparencyLevel.None;
             AcrylicCompensationLevels = new AcrylicPlatformCompensationLevels(1, 1, 1);
             _touchDevice = new TouchDevice();
             _penDevice = new PenDevice();
@@ -218,13 +217,8 @@ namespace Avalonia.Browser
             return null;
         }
 
-        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel)
+        public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevel)
         {
-            if (transparencyLevel == WindowTransparencyLevel.None
-                || transparencyLevel == WindowTransparencyLevel.Transparent)
-            {
-                TransparencyLevel = transparencyLevel;
-            }
         }
 
         public Size ClientSize => _clientSize;
@@ -244,7 +238,7 @@ namespace Avalonia.Browser
         public IMouseDevice MouseDevice { get; } = new MouseDevice();
 
         public IKeyboardDevice KeyboardDevice { get; } = BrowserWindowingPlatform.Keyboard;
-        public WindowTransparencyLevel TransparencyLevel { get; private set; }
+        public WindowTransparencyLevel TransparencyLevel => WindowTransparencyLevel.None;
         public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
         {
             // not in the standard, but we potentially can use "apple-mobile-web-app-status-bar-style" for iOS and "theme-color" for android.

src/Headless/Avalonia.Headless/HeadlessWindowImpl.cs

@@ -336,7 +336,7 @@ namespace Avalonia.Headless
             
         }
 
-        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel)
+        public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevel)
         {
             
         }

src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs

@@ -72,9 +72,9 @@ using Avalonia.Rendering.Composition;
 
         public Size ScaledSize => _outputBackend.PixelSize.ToSize(RenderScaling);
 
-        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel) { }
+        public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevel) { }
 
-        public WindowTransparencyLevel TransparencyLevel { get; private set; }
+        public WindowTransparencyLevel TransparencyLevel => WindowTransparencyLevel.None;
 
         public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
 

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/AvaloniaXamlIlLanguageParseIntrinsics.cs

@@ -274,6 +274,19 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
                 }
             }
 
+            if (type.Equals(types.WindowTransparencyLevel))
+            {
+                foreach (var property in types.WindowTransparencyLevel.Properties)
+                {
+                    if (property.PropertyType == types.WindowTransparencyLevel && property.Name.Equals(text, StringComparison.OrdinalIgnoreCase))
+                    {
+                        result = new XamlStaticOrTargetedReturnMethodCallNode(node, property.Getter, Enumerable.Empty<IXamlAstValueNode>());
+
+                        return true;
+                    }
+                }
+            }
+
             if (type.Equals(types.Uri))
             {
                 var uriText = text.Trim();
@@ -385,7 +398,8 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
                     result = new AvaloniaXamlIlArrayConstantAstNode(node, elementType.MakeArrayType(1), elementType, nodes);
                     return true;
                 }
-                else if (type == context.Configuration.WellKnownTypes.IListOfT.MakeGenericType(elementType))
+                else if (type == context.Configuration.WellKnownTypes.IListOfT.MakeGenericType(elementType) ||
+                    type == types.IReadOnlyListOfT.MakeGenericType(elementType))
                 {
                     var listType = context.Configuration.WellKnownTypes.IListOfT.MakeGenericType(elementType);
                     result = new AvaloniaXamlIlArrayConstantAstNode(node, listType, elementType, nodes);

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlWellKnownTypes.cs

@@ -117,6 +117,8 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
         public IXamlConstructor UriConstructor { get; }
         public IXamlType Style { get; }
         public IXamlType ControlTheme { get; }
+        public IXamlType WindowTransparencyLevel { get; }
+        public IXamlType IReadOnlyListOfT { get; }
 
         public AvaloniaXamlIlWellKnownTypes(TransformerConfiguration cfg)
         {
@@ -199,6 +201,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             FontFamily = cfg.TypeSystem.GetType("Avalonia.Media.FontFamily");
             FontFamilyConstructorUriName = FontFamily.GetConstructor(new List<IXamlType> { Uri, XamlIlTypes.String });
             ThemeVariant = cfg.TypeSystem.GetType("Avalonia.Styling.ThemeVariant");
+            WindowTransparencyLevel = cfg.TypeSystem.GetType("Avalonia.Controls.WindowTransparencyLevel");
 
             (IXamlType, IXamlConstructor) GetNumericTypeInfo(string name, IXamlType componentType, int componentCount)
             {
@@ -260,6 +263,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             UriConstructor = Uri.GetConstructor(new List<IXamlType>() { cfg.WellKnownTypes.String, UriKind });
             Style = cfg.TypeSystem.GetType("Avalonia.Styling.Style");
             ControlTheme = cfg.TypeSystem.GetType("Avalonia.Styling.ControlTheme");
+            IReadOnlyListOfT = cfg.TypeSystem.GetType("System.Collections.Generic.IReadOnlyList`1");
         }
     }
 

src/Windows/Avalonia.Win32.Interop/Wpf/WpfTopLevelImpl.cs

@@ -241,9 +241,9 @@ namespace Avalonia.Win32.Interop.Wpf
 
         public IPopupImpl CreatePopup() => null;
 
-        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel) { }
+        public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevel) { }
 
-        public WindowTransparencyLevel TransparencyLevel { get; private set; }
+        public WindowTransparencyLevel TransparencyLevel => WindowTransparencyLevel.None;
 
         public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
 

src/Windows/Avalonia.Win32/PlatformConstants.cs

@@ -2,12 +2,13 @@ using System;
 
 namespace Avalonia.Win32
 {
-    public static class PlatformConstants
+    internal static class PlatformConstants
     {
         public const string WindowHandleType = "HWND";
         public const string CursorHandleType = "HCURSOR";
 
-        internal static readonly Version Windows8 = new Version(6, 2);
-        internal static readonly Version Windows7 = new Version(6, 1);
+        public static readonly Version Windows10 = new Version(10, 0);
+        public static readonly Version Windows8 = new Version(6, 2);
+        public static readonly Version Windows7 = new Version(6, 1);
     }
 }

src/Windows/Avalonia.Win32/TrayIconImpl.cs

@@ -147,7 +147,7 @@ namespace Avalonia.Win32
                 SystemDecorations = SystemDecorations.None,
                 SizeToContent = SizeToContent.WidthAndHeight,
                 Background = null,
-                TransparencyLevelHint = WindowTransparencyLevel.Transparent,
+                TransparencyLevelHint = new[] { WindowTransparencyLevel.Transparent },
                 Content = new TrayIconMenuFlyoutPresenter()
                 {
                     ItemsSource = menuItems

src/Windows/Avalonia.Win32/WinRT/Composition/WinUiCompositionShared.cs

@@ -12,6 +12,7 @@ internal class WinUiCompositionShared : IDisposable
     public ICompositionBrush? MicaBrush { get; }
     public object SyncRoot { get; } = new();
 
+    public static readonly Version MinAcrylicVersion = new(10, 0, 15063);
     public static readonly Version MinHostBackdropVersion = new(10, 0, 22000);
     
     public WinUiCompositionShared(ICompositor compositor)

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
@@ -25,6 +25,7 @@ using Avalonia.Win32.WinRT.Composition;
 using Avalonia.Win32.WinRT;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 using Avalonia.Input.Platform;
+using System.Diagnostics;
 
 namespace Avalonia.Win32
 {
@@ -97,6 +98,7 @@ namespace Avalonia.Win32
         private bool _hiddenWindowIsParent;
         private uint _langid;
         private bool _ignoreWmChar;
+        private WindowTransparencyLevel _transparencyLevel;
 
         private const int MaxPointerHistorySize = 512;
         private static readonly PooledList<RawPointerPoint> s_intermediatePointsPooledList = new();
@@ -180,6 +182,7 @@ namespace Avalonia.Win32
             _storageProvider = new Win32StorageProvider(this);
 
             _nativeControlHost = new Win32NativeControlHost(this, _isUsingComposition);
+            _transparencyLevel = _isUsingComposition ? WindowTransparencyLevel.Transparent : WindowTransparencyLevel.None;
             s_instances.Add(this);
         }
 
@@ -313,7 +316,18 @@ namespace Avalonia.Win32
             }
         }
 
-        public WindowTransparencyLevel TransparencyLevel { get; private set; }
+        public WindowTransparencyLevel TransparencyLevel
+        {
+            get => _transparencyLevel;
+            private set
+            {
+                if (_transparencyLevel != value)
+                {
+                    _transparencyLevel = value;
+                    TransparencyLevelChanged?.Invoke(value);
+                }
+            }
+        }
 
         protected IntPtr Hwnd => _hwnd;
 
@@ -344,82 +358,132 @@ namespace Avalonia.Win32
             return null;
         }
 
-        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel)
+        public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevels)
         {
-            TransparencyLevel = EnableBlur(transparencyLevel);
-        }
+            var windowsVersion = Win32Platform.WindowsVersion;
+
+            foreach (var level in transparencyLevels)
+            {
+                if (!IsSupported(level, windowsVersion))
+                    continue;
+                if (level == TransparencyLevel)
+                    return;
+                if (level == WindowTransparencyLevel.Transparent)
+                    SetTransparencyTransparent(windowsVersion);
+                else if (level == WindowTransparencyLevel.Blur)
+                    SetTransparencyBlur(windowsVersion);
+                else if (level == WindowTransparencyLevel.AcrylicBlur)
+                    SetTransparencyAcrylicBlur(windowsVersion);
+                else if (level == WindowTransparencyLevel.Mica)
+                    SetTransparencyMica(windowsVersion);
+
+                TransparencyLevel = level;
+                return;
+            }
 
-        private WindowTransparencyLevel EnableBlur(WindowTransparencyLevel transparencyLevel)
-        {
-            if (Win32Platform.WindowsVersion.Major >= 6)
+            // If we get here, we didn't find a supported level. Use the defualt of Transparent or
+            // None, depending on whether composition is enabled.
+            if (_isUsingComposition)
             {
-                if (DwmIsCompositionEnabled(out var compositionEnabled) != 0 || !compositionEnabled)
-                {
-                    return WindowTransparencyLevel.None;
-                }
-                else if (Win32Platform.WindowsVersion.Major >= 10)
-                {
-                    return Win10EnableBlur(transparencyLevel);
-                }
-                else if (Win32Platform.WindowsVersion.Minor >= 2)
-                {
-                    return Win8xEnableBlur(transparencyLevel);
-                }
-                else
-                {
-                    return Win7EnableBlur(transparencyLevel);
-                }
+                SetTransparencyTransparent(windowsVersion);
+                TransparencyLevel = WindowTransparencyLevel.Transparent;
             }
             else
             {
-                return WindowTransparencyLevel.None;
+                TransparencyLevel = WindowTransparencyLevel.None;
             }
         }
 
-        private WindowTransparencyLevel Win7EnableBlur(WindowTransparencyLevel transparencyLevel)
+        private bool IsSupported(WindowTransparencyLevel level, Version windowsVersion)
         {
-            if (transparencyLevel == WindowTransparencyLevel.AcrylicBlur)
-            {
-                transparencyLevel = WindowTransparencyLevel.Blur;
-            }
+            // Only None is suppported when composition is disabled.
+            if (!_isUsingComposition)
+                return level == WindowTransparencyLevel.None;
 
-            var blurInfo = new DWM_BLURBEHIND(false);
+            // When composition is enabled, None is not supported because the backing visual always
+            // has an alpha channel
+            if (level == WindowTransparencyLevel.None)
+                return false;
 
-            if (transparencyLevel == WindowTransparencyLevel.Blur)
+            // Transparent only supported on Windows 8+.
+            if (level == WindowTransparencyLevel.Transparent)
+                return windowsVersion >= PlatformConstants.Windows8;
+
+            // Blur only supported on Windows 8 and lower.
+            if (level == WindowTransparencyLevel.Blur)
+                return windowsVersion < PlatformConstants.Windows10;
+
+            // Acrylic is supported on Windows >= 10.0.15063.
+            if (level == WindowTransparencyLevel.AcrylicBlur)
+                return windowsVersion >= WinUiCompositionShared.MinAcrylicVersion;
+
+            // Mica is supported on Windows >= 10.0.22000.
+            if (level == WindowTransparencyLevel.Mica)
+                return windowsVersion >= WinUiCompositionShared.MinHostBackdropVersion;
+
+            return false;
+        }
+
+        private void SetTransparencyTransparent(Version windowsVersion)
+        {
+            // Transparent only supported with composition on Windows 8+.
+            if (!_isUsingComposition || windowsVersion < PlatformConstants.Windows8)
+                return;
+
+            if (windowsVersion < PlatformConstants.Windows10)
             {
-                blurInfo = new DWM_BLURBEHIND(true);
+                // Some of the AccentState Enum's values have different meanings on Windows 8.x than on
+                // Windows 10, hence using ACCENT_ENABLE_BLURBEHIND to disable blurbehind  ¯\_(ツ)_/¯.
+                // Hey, I'm just porting what was here before.
+                SetAccentState(AccentState.ACCENT_ENABLE_BLURBEHIND);
+                var blurInfo = new DWM_BLURBEHIND(false);
+                DwmEnableBlurBehindWindow(_hwnd, ref blurInfo);
             }
 
+            SetUseHostBackdropBrush(false);
+            _blurHost?.SetBlur(BlurEffect.None);
+        }
+
+        private void SetTransparencyBlur(Version windowsVersion)
+        {
+            // Blur only supported with composition on Windows 8 and lower.
+            if (!_isUsingComposition || windowsVersion >= PlatformConstants.Windows10)
+                return;
+
+            // Some of the AccentState Enum's values have different meanings on Windows 8.x than on
+            // Windows 10.
+            SetAccentState(AccentState.ACCENT_DISABLED);
+            var blurInfo = new DWM_BLURBEHIND(true);
             DwmEnableBlurBehindWindow(_hwnd, ref blurInfo);
+        }
 
-            if (transparencyLevel == WindowTransparencyLevel.Transparent)
-            {
-                return WindowTransparencyLevel.None;
-            }
-            else
-            {
-                return transparencyLevel;
-            }
+        private void SetTransparencyAcrylicBlur(Version windowsVersion)
+        {
+            // Acrylic blur only supported with composition on Windows >= 10.0.15063.
+            if (!_isUsingComposition || windowsVersion < WinUiCompositionShared.MinAcrylicVersion)
+                return;
+
+            SetUseHostBackdropBrush(true);
+            _blurHost?.SetBlur(BlurEffect.Acrylic);
         }
 
-        private WindowTransparencyLevel Win8xEnableBlur(WindowTransparencyLevel transparencyLevel)
+        private void SetTransparencyMica(Version windowsVersion)
         {
-            var accent = new AccentPolicy();
-            var accentStructSize = Marshal.SizeOf<AccentPolicy>();
+            // Mica only supported with composition on Windows >= 10.0.22000.
+            if (!_isUsingComposition || windowsVersion < WinUiCompositionShared.MinHostBackdropVersion)
+                return;
 
-            if (transparencyLevel == WindowTransparencyLevel.AcrylicBlur)
-            {
-                transparencyLevel = WindowTransparencyLevel.Blur;
-            }
+            SetUseHostBackdropBrush(false);
+            _blurHost?.SetBlur(BlurEffect.Mica);
+        }
 
-            if (transparencyLevel == WindowTransparencyLevel.Transparent)
-            {
-                accent.AccentState = AccentState.ACCENT_ENABLE_BLURBEHIND;
-            }
-            else
-            {
-                accent.AccentState = AccentState.ACCENT_DISABLED;
-            }
+        private void SetAccentState(AccentState state)
+        {
+            var accent = new AccentPolicy();
+            var accentStructSize = Marshal.SizeOf(accent);
+
+            //Some of the AccentState Enum's values have different meanings on Windows 8.x than on Windows 10
+            accent.AccentState = state;
 
             var accentPtr = Marshal.AllocHGlobal(accentStructSize);
             Marshal.StructureToPtr(accent, accentPtr, false);
@@ -430,98 +494,18 @@ namespace Avalonia.Win32
             data.Data = accentPtr;
 
             SetWindowCompositionAttribute(_hwnd, ref data);
-
             Marshal.FreeHGlobal(accentPtr);
-
-            if (transparencyLevel >= WindowTransparencyLevel.Blur)
-            {
-                Win7EnableBlur(transparencyLevel);
-            }
-
-            return transparencyLevel;
         }
 
-        private WindowTransparencyLevel Win10EnableBlur(WindowTransparencyLevel transparencyLevel)
+        private void SetUseHostBackdropBrush(bool useHostBackdropBrush)
         {
-            if (_isUsingComposition)
-            {
-                var effect = transparencyLevel switch
-                {
-                    WindowTransparencyLevel.Mica => BlurEffect.Mica,
-                    WindowTransparencyLevel.AcrylicBlur => BlurEffect.Acrylic,
-                    WindowTransparencyLevel.Blur => BlurEffect.Acrylic,
-                    _ => BlurEffect.None
-                };
-
-                if (Win32Platform.WindowsVersion >= WinUiCompositionShared.MinHostBackdropVersion)
-                {
-                    unsafe
-                    {
-                        int pvUseBackdropBrush = effect == BlurEffect.Acrylic ? 1 : 0;
-                        DwmSetWindowAttribute(_hwnd, (int)DwmWindowAttribute.DWMWA_USE_HOSTBACKDROPBRUSH, &pvUseBackdropBrush, sizeof(int));
-                    }
-                }
-
-                if (Win32Platform.WindowsVersion < WinUiCompositionShared.MinHostBackdropVersion && effect == BlurEffect.Mica)
-                {
-                    effect = BlurEffect.Acrylic;
-                }
-
-                _blurHost?.SetBlur(effect);
+            if (Win32Platform.WindowsVersion < WinUiCompositionShared.MinHostBackdropVersion)
+                return;
 
-                return transparencyLevel;
-            }
-            else
+            unsafe
             {
-                bool canUseAcrylic = Win32Platform.WindowsVersion.Major > 10 || Win32Platform.WindowsVersion.Build >= 19628;
-
-                var accent = new AccentPolicy();
-                var accentStructSize = Marshal.SizeOf<AccentPolicy>();
-
-                if (transparencyLevel == WindowTransparencyLevel.AcrylicBlur && !canUseAcrylic)
-                {
-                    transparencyLevel = WindowTransparencyLevel.Blur;
-                }
-
-                switch (transparencyLevel)
-                {
-                    default:
-                    case WindowTransparencyLevel.None:
-                        accent.AccentState = AccentState.ACCENT_DISABLED;
-                        break;
-
-                    case WindowTransparencyLevel.Transparent:
-                        accent.AccentState = AccentState.ACCENT_ENABLE_TRANSPARENTGRADIENT;
-                        break;
-
-                    case WindowTransparencyLevel.Blur:
-                        accent.AccentState = AccentState.ACCENT_ENABLE_BLURBEHIND;
-                        break;
-
-                    case WindowTransparencyLevel.AcrylicBlur:
-                    case WindowTransparencyLevel.ForceAcrylicBlur: // hack-force acrylic.
-                    case WindowTransparencyLevel.Mica:
-                        accent.AccentState = AccentState.ACCENT_ENABLE_ACRYLIC;
-                        transparencyLevel = WindowTransparencyLevel.AcrylicBlur;
-                        break;
-                }
-
-                accent.AccentFlags = 2;
-                accent.GradientColor = 0x01000000;
-
-                var accentPtr = Marshal.AllocHGlobal(accentStructSize);
-                Marshal.StructureToPtr(accent, accentPtr, false);
-
-                var data = new WindowCompositionAttributeData();
-                data.Attribute = WindowCompositionAttribute.WCA_ACCENT_POLICY;
-                data.SizeOfData = accentStructSize;
-                data.Data = accentPtr;
-
-                SetWindowCompositionAttribute(_hwnd, ref data);
-
-                Marshal.FreeHGlobal(accentPtr);
-
-                return transparencyLevel;
+                var pvUseBackdropBrush = useHostBackdropBrush ? 1 : 0;
+                DwmSetWindowAttribute(_hwnd, (int)DwmWindowAttribute.DWMWA_USE_HOSTBACKDROPBRUSH, &pvUseBackdropBrush, sizeof(int));
             }
         }
 

src/iOS/Avalonia.iOS/AvaloniaView.cs

@@ -137,7 +137,7 @@ namespace Avalonia.iOS
                 return null;
             }
 
-            public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel)
+            public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevel)
             {
                 // No-op
             }
@@ -157,8 +157,8 @@ namespace Avalonia.iOS
 
             // legacy no-op
             public IMouseDevice MouseDevice { get; } = new MouseDevice();
-            public WindowTransparencyLevel TransparencyLevel { get; }
-            
+            public WindowTransparencyLevel TransparencyLevel => WindowTransparencyLevel.None;
+
             public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
             {
                 // TODO adjust status bar depending on full screen mode.

src/iOS/Avalonia.iOS/Platform.cs

@@ -47,12 +47,8 @@ namespace Avalonia.iOS
                 .Bind<IDispatcherImpl>().ToConstant(DispatcherImpl.Instance)
                 .Bind<IKeyboardDevice>().ToConstant(keyboard);
 
-                Compositor = new Compositor(
-                    AvaloniaLocator.Current.GetRequiredService<IRenderLoop>(),
-                    AvaloniaLocator.Current.GetService<IPlatformGraphics>());
+                Compositor = new Compositor(AvaloniaLocator.Current.GetService<IPlatformGraphics>());
         }
-
-
     }
 }
 

tests/Avalonia.Controls.UnitTests/ContextMenuTests.cs

@@ -36,7 +36,7 @@ namespace Avalonia.Controls.UnitTests
 
                 int openedCount = 0;
 
-                sut.MenuOpened += (sender, args) =>
+                sut.Opened += (sender, args) =>
                 {
                     openedCount++;
                 };
@@ -139,7 +139,7 @@ namespace Avalonia.Controls.UnitTests
 
                 int openedCount = 0;
 
-                sut.MenuOpened += (sender, args) =>
+                sut.Opened += (sender, args) =>
                 {
                     openedCount++;
                 };
@@ -168,7 +168,7 @@ namespace Avalonia.Controls.UnitTests
 
                 bool opened = false;
 
-                sut.MenuOpened += (sender, args) =>
+                sut.Opened += (sender, args) =>
                 {
                     opened = true;
                 };
@@ -221,7 +221,7 @@ namespace Avalonia.Controls.UnitTests
 
                 int closedCount = 0;
 
-                sut.MenuClosed += (sender, args) =>
+                sut.Closed += (sender, args) =>
                 {
                     closedCount++;
                 };
@@ -259,7 +259,7 @@ namespace Avalonia.Controls.UnitTests
                 var tracker = 0;
 
                 var c = new ContextMenu();
-                c.ContextMenuClosing += (s, e) =>
+                c.Closing += (s, e) =>
                 {
                     tracker++;
                     e.Cancel = true;
@@ -431,7 +431,7 @@ namespace Avalonia.Controls.UnitTests
                 };
                 new Window { Content = target };
 
-                sut.ContextMenuOpening += (c, e) => { eventCalled = true; e.Cancel = true; };
+                sut.Opening += (c, e) => { eventCalled = true; e.Cancel = true; };
 
                 _mouse.Click(target, MouseButton.Right);
 
@@ -575,7 +575,7 @@ namespace Avalonia.Controls.UnitTests
                 var window = PreparedWindow(target);
                 var overlay = LightDismissOverlayLayer.GetLightDismissOverlayLayer(window);
 
-                sut.ContextMenuClosing += (c, e) => { eventCalled = true; e.Cancel = true; };
+                sut.Closing += (c, e) => { eventCalled = true; e.Cancel = true; };
 
                 window.Show();
 

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/WindowTests.cs

@@ -0,0 +1,26 @@
+using Avalonia.Controls;
+using Avalonia.UnitTests;
+using Xunit;
+
+namespace Avalonia.Markup.Xaml.UnitTests.Xaml
+{
+    public class WindowTests : XamlTestBase
+    {
+        [Fact]
+        public void Can_Specify_TransparencyLevelHint()
+        {
+            using var app = UnitTestApplication.Start(TestServices.MockWindowingPlatform);
+            var xaml = @"<Window xmlns='https://github.com/avaloniaui' TransparencyLevelHint='Blur,Transparent,None'/>";
+
+            var target = AvaloniaRuntimeXamlLoader.Parse<Window>(xaml);
+
+            Assert.Equal(
+                new[]
+                {
+                    WindowTransparencyLevel.Blur,
+                    WindowTransparencyLevel.Transparent,
+                    WindowTransparencyLevel.None,
+                }, target.TransparencyLevelHint);
+        }
+    }
+}

tests/Avalonia.UnitTests/CompositorTestServices.cs

@@ -186,11 +186,11 @@ public class CompositorTestServices : IDisposable
         public IMouseDevice MouseDevice { get; } = new MouseDevice();
         public IPopupImpl CreatePopup() => throw new NotImplementedException();
 
-        public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel)
+        public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevel)
         {
         }
 
-        public WindowTransparencyLevel TransparencyLevel { get; }
+        public WindowTransparencyLevel TransparencyLevel => WindowTransparencyLevel.None;
 
         public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
         {