PowerToys/src/settings-ui/Settings.UI/FlyoutWindow.xaml

<winuiex:WindowEx
    x:Class="Microsoft.PowerToys.Settings.UI.FlyoutWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:flyout="using:Microsoft.PowerToys.Settings.UI.Flyout"
    xmlns:local="using:Microsoft.PowerToys.Settings.UI"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:winuiex="using:WinUIEx"
    xmlns:i="using:Microsoft.Xaml.Interactivity"
    xmlns:ic="using:Microsoft.Xaml.Interactions.Core"
    Title="PowerToys Settings"
    IsAlwaysOnTop="True"
    IsMaximizable="False"
    IsMinimizable="False"
    IsResizable="False"
    IsShownInSwitchers="False"
    IsTitleBarVisible="False"
    mc:Ignorable="d">
    <winuiex:WindowEx.Backdrop>
        <winuiex:AcrylicSystemBackdrop
            DarkFallbackColor="#1c1c1c"
            DarkLuminosityOpacity="0.96"
            DarkTintColor="#202020"
            DarkTintOpacity="0.5"
            LightFallbackColor="#EEEEEE"
            LightLuminosityOpacity="0.90"
            LightTintColor="#F3F3F3"
            LightTintOpacity="0" />
    </winuiex:WindowEx.Backdrop>
    <Grid>
        <!-- HACK: https://github.com/microsoft/microsoft-ui-xaml/issues/7629 -->
        <!-- W11 grey border, W10: no border  -->
        <i:Interaction.Behaviors>
            <ic:DataTriggerBehavior
                Binding="{x:Bind ViewModel.Windows10}"
                ComparisonCondition="Equal"
                Value="True">
                <ic:ChangePropertyAction
                    PropertyName="BorderThickness"
                    Value="1" />
                <ic:ChangePropertyAction
                    PropertyName="BorderBrush"
                    Value="{ThemeResource SurfaceStrokeColorDefaultBrush}" />
            </ic:DataTriggerBehavior>
        </i:Interaction.Behaviors>
        <flyout:ShellPage x:Name="FlyoutShellPage" />
    </Grid>
</winuiex:WindowEx>