ux: try to use Mica material for main window's titlebar on Windows 11

Signed-off-by: leo <longshuang@msn.cn>

Author: love-linger

src/Views/Launcher.axaml

@@ -22,7 +22,7 @@
     <Grid Grid.Row="0" ColumnDefinitions="Auto,32,32,*,Auto">
       <!-- Bottom border -->
       <Border Grid.Column="0" Grid.ColumnSpan="5"
-              Background="{DynamicResource Brush.TitleBar}"
+              x:Name="TitleBarBG"
               BorderThickness="0,0,0,1" BorderBrush="{DynamicResource Brush.Border0}"
               DoubleTapped="MaximizeOrRestoreWindow"
               PointerPressed="BeginMoveWindow"/>
@@ -115,7 +115,7 @@
     </Grid>
 
     <!-- Page -->
-    <ContentControl Grid.Row="1" Content="{Binding ActivePage}">
+    <ContentControl Grid.Row="1" Content="{Binding ActivePage}" Background="{DynamicResource Brush.Window}">
       <ContentControl.DataTemplates>
         <DataTemplate DataType="vm:LauncherPage">
           <v:LauncherPage/>

src/Views/Launcher.axaml.cs

@@ -4,6 +4,7 @@
 using Avalonia.Controls;
 using Avalonia.Input;
 using Avalonia.Interactivity;
+using Avalonia.Markup.Xaml.MarkupExtensions;
 using Avalonia.Media;
 using Avalonia.Platform;
 using Avalonia.VisualTree;
@@ -61,6 +62,17 @@ public Launcher()
             InitializeComponent();
             PositionChanged += OnPositionChanged;
 
+            if (OperatingSystem.IsWindows() && OperatingSystem.IsWindowsVersionAtLeast(10, 0, 22000))
+            {
+                Background = Brushes.Transparent;
+                TransparencyLevelHint = [WindowTransparencyLevel.Mica];
+                TitleBarBG.Background = Brushes.Transparent;
+            }
+            else
+            {
+                TitleBarBG.Bind(BackgroundProperty, new DynamicResourceExtension("Brush.TitleBar"));
+            }
+
             var layout = ViewModels.Preferences.Instance.Layout;
             Width = layout.LauncherWidth;
             Height = layout.LauncherHeight;