allow setting ThemeVariant to Default to reset theme to system on android

samples/SafeAreaDemo/App.xaml

@@ -2,7 +2,7 @@
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:local="using:SafeAreaDemo"
              x:Class="SafeAreaDemo.App"
-             RequestedThemeVariant="Light">
+             RequestedThemeVariant="Default">
     <Application.DataTemplates>
         <local:ViewLocator/>
     </Application.DataTemplates>

samples/SafeAreaDemo/Views/MainView.xaml

@@ -8,7 +8,6 @@
              d:DesignHeight="450"
              x:Class="SafeAreaDemo.Views.MainView"
              x:DataType="vm:MainViewModel"
-             Background="#ccc"
              TopLevel.AutoSafeAreaPadding="{Binding AutoSafeAreaPadding, Mode=TwoWay}">
     <Grid HorizontalAlignment="Stretch"
           VerticalAlignment="Stretch"

src/Android/Avalonia.Android/AvaloniaView.cs

@@ -17,21 +17,18 @@ namespace Avalonia.Android
 {
     public class AvaloniaView : FrameLayout
     {
-        private EmbeddableControlRoot _root;
+        private EmbeddableControlRoot? _root;
         private readonly ViewImpl _view;
 
         private IDisposable? _timerSubscription;
+        private object? _content;
 
         public AvaloniaView(Context context) : base(context)
         {
             _view = new ViewImpl(this);
             AddView(_view.View);
 
-            _root = new EmbeddableControlRoot(_view);
-            _root.Prepare();
-
             this.SetBackgroundColor(global::Android.Graphics.Color.Transparent);
-            OnConfigurationChanged();
         }
 
         internal TopLevelImpl TopLevelImpl => _view;
@@ -39,15 +36,42 @@ namespace Avalonia.Android
 
         public object? Content
         {
-            get { return _root.Content; }
-            set { _root.Content = value; }
+            get { return _root?.Content; }
+            set
+            {
+                _content = null;
+                if (_root != null)
+                    _root.Content = value;
+                else
+                {
+                    _content = value;
+                }
+            }
         }
 
         protected override void Dispose(bool disposing)
         {
             base.Dispose(disposing);
+        }
+
+        protected override void OnDetachedFromWindow()
+        {
+            base.OnDetachedFromWindow();
             _root?.Dispose();
-            _root = null!;
+            _root = null;
+        }
+
+        protected override void OnAttachedToWindow()
+        {
+            _root = new EmbeddableControlRoot(_view);
+            _root.Prepare();
+            if(_content != null)
+            {
+                _root.Content = _content;
+            }
+            SendConfigurationChanged(Context?.Resources?.Configuration);
+
+            base.OnAttachedToWindow();
         }
 
         public override bool DispatchKeyEvent(KeyEvent? e)
@@ -70,6 +94,8 @@ namespace Avalonia.Android
 
         internal void OnVisibilityChanged(bool isVisible)
         {
+            if (_root == null)
+                return;
             if (isVisible && _timerSubscription == null)
             {
                 if (AvaloniaLocator.Current.GetService<IRenderTimer>() is ChoreographerTimer timer)
@@ -95,16 +121,17 @@ namespace Avalonia.Android
         protected override void OnConfigurationChanged(Configuration? newConfig)
         {
             base.OnConfigurationChanged(newConfig);
-            OnConfigurationChanged();
+            SendConfigurationChanged(newConfig ?? Context?.Resources?.Configuration);
         }
 
-        private void OnConfigurationChanged()
+        private void SendConfigurationChanged(Configuration? newConfig)
         {
-            if (Context is { } context)
+            _view?.InsetsManager?.SetDefaultSystemLightMode(!(newConfig?.UiMode.HasFlag(UiMode.NightYes) ?? false));
+            if (Context is { } context && newConfig is { } config)
             {
                 var settings =
                     AvaloniaLocator.Current.GetRequiredService<IPlatformSettings>() as AndroidPlatformSettings;
-                settings?.OnViewConfigurationChanged(context);
+                settings?.OnViewConfigurationChanged(context, config);
             }
         }
 

src/Android/Avalonia.Android/Platform/AndroidInsetsManager.cs

@@ -166,6 +166,11 @@ namespace Avalonia.Android.Platform
             return insets;
         }
 
+        internal void SetDefaultSystemLightMode(bool islightMode)
+        {
+            _isDefaultSystemBarLightTheme = islightMode;
+        }
+
         private void NotifySafeAreaChanged(Thickness safeAreaPadding)
         {
             Dispatcher.UIThread.Send(_ => SafeAreaChanged?.Invoke(this, new SafeAreaChangedArgs(safeAreaPadding)));

src/Android/Avalonia.Android/Platform/AndroidPlatformSettings.cs

@@ -22,14 +22,14 @@ internal class AndroidPlatformSettings : DefaultPlatformSettings
         return _latestValues;
     }
 
-    internal void OnViewConfigurationChanged(Context context)
+    internal void OnViewConfigurationChanged(Context context, Configuration configuration)
     {
-        if (context.Resources?.Configuration is null)
+        if (context.Resources is null)
         {
             return;
         }
 
-        var systemTheme = (context.Resources.Configuration.UiMode & UiMode.NightMask) switch
+        PlatformThemeVariant systemTheme = (configuration.UiMode & UiMode.NightMask) switch
         {
             UiMode.NightYes => PlatformThemeVariant.Dark,
             UiMode.NightNo => PlatformThemeVariant.Light,
@@ -71,7 +71,7 @@ internal class AndroidPlatformSettings : DefaultPlatformSettings
                 }
                 finally
                 {
-                    array.Recycle();   
+                    array.Recycle();
                 }
             }
         }

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

@@ -282,9 +282,9 @@ namespace Avalonia.Android.Platform.SkiaPlatform
             }
         }
 
-        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+        public void SetFrameThemeVariant(PlatformThemeVariant? themeVariant)
         {
-            if(_insetsManager != null)
+            if (_insetsManager != null)
             {
                 _insetsManager.SystemBarTheme = themeVariant switch
                 {
@@ -294,7 +294,16 @@ namespace Avalonia.Android.Platform.SkiaPlatform
                 };
             }
 
-            AppCompatDelegate.DefaultNightMode = themeVariant == PlatformThemeVariant.Light ? AppCompatDelegate.ModeNightNo : AppCompatDelegate.ModeNightYes;
+            AppCompatDelegate.DefaultNightMode = themeVariant == null ? AppCompatDelegate.ModeNightFollowSystem :
+                themeVariant == PlatformThemeVariant.Light ? AppCompatDelegate.ModeNightNo : AppCompatDelegate.ModeNightYes;
+
+            if (AppCompatDelegate.DefaultNightMode == AppCompatDelegate.ModeNightFollowSystem && _view.Context is { } context
+                && context.Resources?.Configuration is { } config)
+            {
+                var settings =
+                    AvaloniaLocator.Current.GetRequiredService<IPlatformSettings>() as AndroidPlatformSettings;
+                settings?.OnViewConfigurationChanged(context, config);
+            }
         }
 
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels => new AcrylicPlatformCompensationLevels(1, 1, 1);
@@ -305,6 +314,8 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
         public double Scaling => RenderScaling;
 
+        internal AndroidInsetsManager? InsetsManager => _insetsManager;
+
         public void SetTransparencyLevelHint(IReadOnlyList<WindowTransparencyLevel> transparencyLevels)
         {
             if (_view.Context is not AvaloniaMainActivity activity)

src/Avalonia.Base/Styling/ThemeVariant.cs

@@ -100,11 +100,11 @@ public sealed record ThemeVariant
         {
             PlatformThemeVariant.Light => Light,
             PlatformThemeVariant.Dark => Dark,
-            _ => throw new ArgumentOutOfRangeException(nameof(themeVariant), themeVariant, null)
+            _ => Default,
         };
     }
 
-    public static explicit operator PlatformThemeVariant?(ThemeVariant themeVariant)
+    public static explicit operator PlatformThemeVariant?(ThemeVariant? themeVariant)
     {
         if (themeVariant == Light)
         {
@@ -114,7 +114,7 @@ public sealed record ThemeVariant
         {
             return PlatformThemeVariant.Dark;
         }
-        else if (themeVariant.InheritVariant is { } inheritVariant)
+        else if (themeVariant?.InheritVariant is { } inheritVariant)
         {
             return (PlatformThemeVariant?)inheritVariant;
         }

src/Avalonia.Controls/Application.cs

@@ -68,6 +68,11 @@ namespace Avalonia
         /// <inheritdoc/>
         public event EventHandler? ActualThemeVariantChanged;
 
+        static Application()
+        {
+            RequestedThemeVariantProperty.OverrideDefaultValue<Application>(ThemeVariant.Default);
+        }
+
         /// <summary>
         /// Creates an instance of the <see cref="Application"/> class.
         /// </summary>
@@ -364,20 +369,19 @@ namespace Avalonia
 
             if (change.Property == RequestedThemeVariantProperty)
             {
-                if (change.GetNewValue<ThemeVariant>() is {} themeVariant && themeVariant != ThemeVariant.Default)
+                if (change.GetNewValue<ThemeVariant>() is { } themeVariant)
                     SetValue(ActualThemeVariantProperty, themeVariant);
-                else
-                    ClearValue(ActualThemeVariantProperty);
             }
             else if (change.Property == ActualThemeVariantProperty)
             {
                 ActualThemeVariantChanged?.Invoke(this, EventArgs.Empty);
             }
         }
-        
+
         private void OnColorValuesChanged(object? sender, PlatformColorValues e)
         {
-            SetValue(ActualThemeVariantProperty, (ThemeVariant)e.ThemeVariant, BindingPriority.Template);
+            if ((RequestedThemeVariant ?? ThemeVariant.Default) == ThemeVariant.Default)
+                SetCurrentValue(ActualThemeVariantProperty, (ThemeVariant)e.ThemeVariant);
         }
     }
 }

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

@@ -61,7 +61,7 @@ namespace Avalonia.Controls.Embedding.Offscreen
 
         public Action<WindowTransparencyLevel>? TransparencyLevelChanged { get; set; }
 
-        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
+        public void SetFrameThemeVariant(PlatformThemeVariant? themeVariant) { }
 
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } = new AcrylicPlatformCompensationLevels(1, 1, 1);
 

src/Avalonia.Controls/Platform/ITopLevelImpl.cs

@@ -136,6 +136,6 @@ namespace Avalonia.Platform
         /// Sets the <see cref="PlatformThemeVariant"/> on the frame if it should be dark or light.
         /// Also applies for the mobile status bar.
         /// </summary>
-        void SetFrameThemeVariant(PlatformThemeVariant themeVariant);
+        void SetFrameThemeVariant(PlatformThemeVariant? themeVariant);
     }
 }

src/Avalonia.Controls/ThemeVariantScope.cs

@@ -15,6 +15,11 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<ThemeVariant?> RequestedThemeVariantProperty =
             ThemeVariant.RequestedThemeVariantProperty.AddOwner<ThemeVariantScope>();
 
+        static ThemeVariantScope()
+        {
+            RequestedThemeVariantProperty.OverrideDefaultValue<ThemeVariantScope>(ThemeVariant.Default);
+        }
+
         /// <summary>
         /// Gets or sets the UI theme variant that is used by the control (and its child elements) for resource determination.
         /// The UI theme you specify with ThemeVariant can override the app-level ThemeVariant.

src/Avalonia.Controls/TopLevel.cs

@@ -233,11 +233,6 @@ namespace Avalonia.Controls
             impl.TransparencyLevelChanged = HandleTransparencyLevelChanged;
 
             CreatePlatformImplBinding(TransparencyLevelHintProperty, hint => PlatformImpl.SetTransparencyLevelHint(hint ?? Array.Empty<WindowTransparencyLevel>()));
-            CreatePlatformImplBinding(ActualThemeVariantProperty, variant =>
-            {
-                variant ??= ThemeVariant.Default;
-                PlatformImpl?.SetFrameThemeVariant((PlatformThemeVariant?)variant ?? PlatformThemeVariant.Light);
-            });
 
             _keyboardNavigationHandler?.SetOwner(this);
             _accessKeyHandler?.SetOwner(this);
@@ -252,6 +247,16 @@ namespace Avalonia.Controls
                 SetValue(ActualThemeVariantProperty, _applicationThemeHost.ActualThemeVariant, BindingPriority.Template);
                 _applicationThemeHost.ActualThemeVariantChanged += GlobalActualThemeVariantChanged;
             }
+            CreatePlatformImplBinding(ActualThemeVariantProperty, variant =>
+            {
+                if(_applicationThemeHost is AvaloniaObject element)
+                {
+                    if (element.GetValue(ThemeVariantScope.RequestedThemeVariantProperty) is { } requestedThemeVariant)
+                        variant = requestedThemeVariant == ThemeVariant.Default ? ThemeVariant.Default : variant;
+                }
+                variant ??= ThemeVariant.Default;
+                PlatformImpl?.SetFrameThemeVariant((PlatformThemeVariant?)variant);
+            });
 
             ClientSize = impl.ClientSize;
 
@@ -878,7 +883,7 @@ namespace Avalonia.Controls
 
         private void GlobalActualThemeVariantChanged(object? sender, EventArgs e)
         {
-            SetValue(ActualThemeVariantProperty, ((IThemeVariantHost)sender!).ActualThemeVariant, BindingPriority.Template);
+            SetCurrentValue(ActualThemeVariantProperty, ((IThemeVariantHost)sender!).ActualThemeVariant);
         }
 
         private void SceneInvalidated(object? sender, SceneInvalidatedEventArgs e)

src/Avalonia.DesignerSupport/Remote/Stubs.cs

@@ -194,7 +194,7 @@ namespace Avalonia.DesignerSupport.Remote
 
         public bool NeedsManagedDecorations => false;
 
-        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
+        public void SetFrameThemeVariant(PlatformThemeVariant? themeVariant) { }
 
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } = new AcrylicPlatformCompensationLevels(1, 1, 1);
         public object TryGetFeature(Type featureType) => null;

src/Avalonia.Native/TopLevelImpl.cs

@@ -148,7 +148,7 @@ internal class TopLevelImpl : ITopLevelImpl, IFramebufferPlatformSurface
     }
 
     public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } = new AcrylicPlatformCompensationLevels(1, 0, 0);
-    public virtual void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+    public virtual void SetFrameThemeVariant(PlatformThemeVariant? themeVariant)
     {
         //noop
     }

src/Avalonia.Native/WindowImplBase.cs

@@ -70,9 +70,9 @@ namespace Avalonia.Native
             Native?.Resize(clientSize.Width, clientSize.Height, (AvnPlatformResizeReason)reason);
         }
         
-        public override void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+        public override void SetFrameThemeVariant(PlatformThemeVariant? themeVariant)
         {
-            Native?.SetFrameThemeVariant((AvnPlatformThemeVariant)themeVariant);
+            Native?.SetFrameThemeVariant((AvnPlatformThemeVariant)(themeVariant ?? PlatformThemeVariant.Light));
         }
 
         public override void Dispose()

src/Avalonia.X11/X11Window.cs

@@ -1440,7 +1440,7 @@ namespace Avalonia.X11
         public WindowTransparencyLevel TransparencyLevel =>
             _transparencyHelper?.CurrentLevel ?? WindowTransparencyLevel.None;
 
-        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
+        public void SetFrameThemeVariant(PlatformThemeVariant? themeVariant) { }
 
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } = new AcrylicPlatformCompensationLevels(1, 0.8, 0.8);
 

src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs

@@ -141,7 +141,7 @@ namespace Avalonia.Browser
         public Action? LostFocus { get; set; }
         public WindowTransparencyLevel TransparencyLevel => WindowTransparencyLevel.None;
 
-        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+        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

@@ -429,7 +429,7 @@ namespace Avalonia.Headless
             
         }
         
-        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+        public void SetFrameThemeVariant(PlatformThemeVariant? themeVariant)
         {
             
         }

src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs

@@ -78,7 +78,7 @@ using Avalonia.Rendering.Composition;
 
         public WindowTransparencyLevel TransparencyLevel => WindowTransparencyLevel.None;
 
-        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
+        public void SetFrameThemeVariant(PlatformThemeVariant? themeVariant) { }
 
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } = new AcrylicPlatformCompensationLevels(1, 1, 1);
         public object TryGetFeature(Type featureType) => null;

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -894,9 +894,9 @@ namespace Avalonia.Win32
             }
         }
 
-        public unsafe void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+        public unsafe void SetFrameThemeVariant(PlatformThemeVariant? themeVariant)
         {
-            _currentThemeVariant = themeVariant;
+            _currentThemeVariant = themeVariant ?? PlatformThemeVariant.Light;
             if (Win32Platform.WindowsVersion.Build >= 22000)
             {
                 var pvUseBackdropBrush = themeVariant == PlatformThemeVariant.Dark ? 1 : 0;

src/iOS/Avalonia.iOS/AvaloniaView.cs

@@ -238,7 +238,7 @@ namespace Avalonia.iOS
 
             public WindowTransparencyLevel TransparencyLevel => WindowTransparencyLevel.None;
 
-            public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+            public void SetFrameThemeVariant(PlatformThemeVariant? themeVariant)
             {
 #if !TVOS
                 // TODO adjust status bar depending on full screen mode.

tests/Avalonia.UnitTests/CompositorTestServices.cs

@@ -211,7 +211,7 @@ public class CompositorTestServices : IDisposable
 
         public WindowTransparencyLevel TransparencyLevel => WindowTransparencyLevel.None;
 
-        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+        public void SetFrameThemeVariant(PlatformThemeVariant? themeVariant)
         {
         }