Acrylic Blur does not work on Windows 11

Describe the bug Win2d acrylic blur does not work on Windows 11 build 22000.160. This also breaks TransparencyLevel.Blur if WinUI compositor is enabled.

DWM transparency and blur works fine.

To Reproduce Steps to reproduce the behavior:

1. Create new project from template
2. Set TransparencyLevelHint.AcrylicBlur on the main window.
3. Set background to null.
4. Run

This can also be observed in the SampleApp.

Expected behavior The acrylic layer should not be opaque.

Screenshots

Desktop (please complete the following information):

• OS: Windows 11 22000.160
• Version 0.10.3; 0.10.7 (master)

Additional context Side note: ICompositor3.CreateHostBackdropBrush() is not broken in this build of windows. ICompositor2.CreateBackdropBrush() might be though.

[gargakshit]

I got Mica to work with ExtendClientAreaToDecorationHint by using UseWindowsUIComposition = true along with ExtendClientAreaChromeHints = PreferSystemChrome

<Window
    xmlns="https://github.com/avaloniaui"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:vm="using:Avalonia.NETCoreMVVMApp1Fs.ViewModels"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
    x:Class="[ClassHere]"
    Icon="/Assets/avalonia-logo.ico"
    Title="[TitleHere]"
    TransparencyLevelHint="Mica"
    Background="{x:Null}"
    ExtendClientAreaToDecorationsHint="True"
    ExtendClientAreaChromeHints="PreferSystemChrome">
    <!-- ... -->
</Window>

[Nickelony]

Even though this issue is closed, I still have problems on Windows 11 and Acrylic Blur / Mica effects. On Windows 10, Acrylic Blur works perfectly fine, on Windows 11 it doesn’t work at all. Using Avalonia 0.10.10 and Windows 11 (22000.318)

Even the Avalonia Control Gallery demo doesn’t seem to have working acrylic either.