[Problem/Bug]: Mica effect stopped working

[Andreas-Froyland]

What happened?

Hi, I have some issues with the Mica effect in our application. We have built an application on Tauri, which uses WebView2. In tauri, we use the Window Vibrancy crate to apply the Mica effect as a background to our app. This worked great and gave a nice look to the application. However, after a recent update to Windows/WebView2, this stopped working.

Below are images of our application, one in a Virtual Machine running an older win 11 build with an older WebView2, and one running locally on the latest Windows version with the latest WebView2. Both are running the same version of the application. "Transparency effects" is turned on in settings on both.

Mica is working:

Mica not working, window is focused:

Importance

Moderate. My app's user experience is affected, but still usable.

Runtime Channel

Stable release (WebView2 Runtime), Prerelease (Edge Canary/Dev/Beta)

Runtime Version

141.0.3537.99

SDK Version

No response

Framework

Other

Operating System

Windows 11

OS Version

10.0.26200

Repro steps

1. Set Mica as the background effect ( set DWMWA_SYSTEMBACKDROP_TYPE to DWMSBT_MAINWINDOW)
2. Mica should apply as background color. It does not.

Repros in Edge Browser

No, issue does not reproduce in the corresponding Edge version

Regression

Regression in newer Runtime

Last working version (if regression)

No response

[Navdeep-ss]

Webview2 runtime is independent of windows update. Can you check with what version of webview2 things were working for you?
Also, it will help if you can provide a bit more detail on how your app uses webview2

as far as I can see window-vibrancy don't use webview2

[Andreas-Froyland]

Thank you for the clarification! I mistakingly thought the effect was handled by WebView when applied to a WebView window. I now realize that is not the case, and its all handled by the Desktop Window Manager if I understand correctly.

Upon checking, they are actually running the same WebView version, the latest stable build.

The app uses WebView through a framework called Tauri, and uses the native web view for rendering, which in this case is WebView2.

Since this probably has nothing to do with WebView, do you think it could be a bug in the Windows Desktop Window Manager then?