Bug: DarkTintOpacity breaks mica backdrop on dark mode

[yaira2]

Description

Modifying the DarkTintOpacity causes mica to be applied incorrectly on dark mode.

Steps to repro

1. Create a MicaSystemBackdrop in xaml and change the DarkTintOpacity value. This issue is only present when you set a custom DarkTintOpacity.

<winuiex:WindowEx.Backdrop>
	<winuiex:MicaSystemBackdrop DarkTintOpacity="0.8"/>
</winuiex:WindowEx.Backdrop>

Screenshot

Version

This issue was introduced in v2.0

[dotMorten]

Something SUPER funky is going on here.
If I step through this method:

WinUIEx/src/WinUIEx/SystemBackdrop.cs

Line 374 in ceacf87

mica.TintOpacity = (float)(isDark ? DarkTintOpacity : LightTintOpacity);

it's not an issue. As I'm stepping through it, I notice the default Mica values are changing mid-debugging.
If I delay the call of this method a few 100 ms, the issue goes away too (but that is error prone and also looks terrible).

It's called from the ActualThemeChanged event:

WinUIEx/src/WinUIEx/WindowManager.Backdrop.cs

Line 87 in ceacf87

m_backdrop.UpdateController(currentController, BackdropConfiguration.Theme);

It's like WinAppSDK doesn't like some properties to get changed right after a theme change, but considering you'd likely want different backdrop settings for light and dark mode, this is the time to do it.

@ChewWorker @codendone @BenJKuhn Any thoughts on this? Are we not supposed to update backdrop values in the theme changed event?

[dotMorten]

WinAppSDK bug. Logged: microsoft/microsoft-ui-xaml#10212

[dotMorten]

Closing now that backdrop APIs are in Windows App SDK and deprecated in WinUIEx

[yaira2]

@dotMorten thank you for your work on this issue!