feat: add demo, sync theme from scope.

demo/Ursa.Demo/Models/MenuKeys.cs

@@ -25,5 +25,6 @@ public static class MenuKeys
     public const string MenuKeyTagInput = "TagInput";
     public const string MenuKeyTimeline = "Timeline";
     public const string MenuKeyTwoTonePathIcon = "TwoTonePathIcon";
+    public const string MenuKeyThemeToggler = "ThemeToggler";
 
 }

demo/Ursa.Demo/Pages/ThemeTogglerDemo.axaml

@@ -0,0 +1,26 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             xmlns:u="https://irihi.tech/ursa"
+             mc:Ignorable="d" d:DesignWidth="800"
+             d:DesignHeight="450"
+             x:Class="Ursa.Demo.Pages.ThemeTogglerDemo">
+    <Grid ColumnDefinitions="Auto, *">
+        <StackPanel Grid.Column="0">
+            <TextBlock Text="Global"></TextBlock>
+            <u:ThemeToggleButton/>
+            <TextBlock Text="Target To Scope"></TextBlock>
+            <u:ThemeToggleButton TargetScope="{Binding #scope}"></u:ThemeToggleButton>
+        </StackPanel>
+        <ThemeVariantScope Grid.Column="1" Name="scope" RequestedThemeVariant="Dark">
+            <Border Theme="{DynamicResource CardBorder}">
+                <StackPanel>
+                    <Button Content="Hello World"></Button>
+                    <Calendar></Calendar>
+                    <u:ThemeToggleButton></u:ThemeToggleButton>
+                </StackPanel>
+            </Border>
+        </ThemeVariantScope>
+    </Grid>
+</UserControl>

demo/Ursa.Demo/Pages/ThemeTogglerDemo.axaml.cs

@@ -0,0 +1,13 @@
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml;
+
+namespace Ursa.Demo.Pages;
+
+public partial class ThemeTogglerDemo : UserControl
+{
+    public ThemeTogglerDemo()
+    {
+        InitializeComponent();
+    }
+}

demo/Ursa.Demo/ViewModels/MainViewViewModel.cs

@@ -47,6 +47,7 @@ public class MainViewViewModel : ViewModelBase
             MenuKeys.MenuKeyTagInput => new TagInputDemoViewModel(),
             MenuKeys.MenuKeyTimeline => new TimelineDemoViewModel(),
             MenuKeys.MenuKeyTwoTonePathIcon => new TwoTonePathIconDemoViewModel(),
+            MenuKeys.MenuKeyThemeToggler => new ThemeTogglerDemoViewModel(),
         };
     }
 }

demo/Ursa.Demo/ViewModels/MenuViewModel.cs

@@ -32,6 +32,7 @@ public class MenuViewModel: ViewModelBase
             new() { MenuHeader = "Pagination", Key = MenuKeys.MenuKeyPagination },
             new() { MenuHeader = "RangeSlider", Key = MenuKeys.MenuKeyRangeSlider, Status = "New"},
             new() { MenuHeader = "TagInput", Key = MenuKeys.MenuKeyTagInput },
+            new() { MenuHeader = "Theme Toggler", Key = MenuKeys.MenuKeyThemeToggler },
             new() { MenuHeader = "Timeline", Key = MenuKeys.MenuKeyTimeline, Status = "Updated" },
             new() { MenuHeader = "TwoTonePathIcon", Key = MenuKeys.MenuKeyTwoTonePathIcon, Status = "New"},
         };

demo/Ursa.Demo/ViewModels/ThemeTogglerDemoViewModel.cs

@@ -0,0 +1,6 @@
+namespace Ursa.Demo.ViewModels;
+
+public class ThemeTogglerDemoViewModel
+{
+    
+}