Added support for Mica Light & Dark based on Win11

[adirh3]

What does the pull request do?

Add support for Mica Light and Dark based on how it looks in Windows 11

What is the current behavior?

The Mica blur is very simple and does not allow for same feel as other Windows 11 apps.

Note

I had this implementation for a while in Fluent Search, and did not push it here as I thought Avalonia composition will eventually replace WinUI one (maybe I misunderstood).
Currently this Light/Dark is based on WindowsTransparencyLevel as it was the only way I found for end-user to be able to interact with WinUI stuff outside of program startup.
I am open for suggestions about changing it.

Light

Dark

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/Documentation with user documentation

Breaking changes

Breaks the current Mica value for WindowsTranspencyLevel.

Obsoletions / Deprecations

Fixed issues

#10719

[Leon99]

Looks promising, lack of proper Mica is a huge gap in Avalonia, especially on Windows 11!
Do you think it'd be possible to leave WindowsTranspencyLevel as Mica and choose the light or dark variant based on system settings?

[maxkatz6]

Removing this value is a breaking change and can't be accepted mid 11.x.

Would be reasonable to keep singe "Mica", but change it behavior depending on the window theme variant?
See

Avalonia/src/Windows/Avalonia.Win32/WindowImpl.cs

Line 791 in 432dafa

public unsafe void SetFrameThemeVariant(PlatformThemeVariant themeVariant)

[robloo]

Mica should automatically switch based on theme variant. I don't think there should be two entries for this and there aren't in WinUI either I believe.

[adirh3]

Changed it, wrote it before ThemeVariants were available :D

[maxkatz6]

did not push it here as I thought Avalonia composition will eventually replace WinUI one (maybe I misunderstood).

Avalonia compositor is not going to replace WinUI one. They work similarly, but one works on a framework level, and another works on OS level, where we can't have full control.

[robloo]

did not push it here as I thought Avalonia composition will eventually replace WinUI one (maybe I misunderstood).

Avalonia compositor is not going to replace WinUI one. They work similarly, but one works on a framework level, and another works on OS level, where we can't have full control.

Sure, don't have full control but also it will be a fully cross-platform implementation by migrating to the Avalonia one. Removing WinUI composition behind the scenes as many places as possible does actually seem like the right move in a cross-platform framework.

[maxkatz6]

WinUI compositor is used onpy and only on windows. And only to prepare a surface to render into + a refresh timer.
Soon we will add Direct Composition support (one that existed before WinUI Composition) for the same goal, but support wider range or windows devices. So we could drop some old non-composition hacks. But again, it's all only about implementation details on Windows.

Avalonia compositor is well abstracted from that, and only is compositiing avalonia visuals.

[adirh3]

Looks promising, lack of proper Mica is a huge gap in Avalonia, especially on Windows 11! Do you think it'd be possible to leave WindowsTranspencyLevel as Mica and choose the light or dark variant based on system settings?

Changed it to be based on theme variant :)

[avaloniaui-team]

You can test this PR using the following package version. 11.0.999-cibuild0037772-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]