MenuFlyout does not update correctly on theme change

[bogdan-patraucean]

Describe the bug

Changing the system theme from Light to Dark or from Dark to Light will not update the Theme of a MenuFlyout on runtime like the rest of the controls.
This happens also in WinUI 3 Gallery app, but randomly, as I can't reproduce it everytime. On my app, on the otherhand, I can reproduce it everytime.

The only way it will display the correct theme is to reopen the app.

It might also be related to #3373 which was for WinUI 2.

Steps to reproduce the bug

1. Create a blank WASDK app, packaged.
2. Add a MenuFlyout on the MainWindow.

<StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center">
    <AppBarButton Icon="Sort" IsCompact="True">
        <AppBarButton.Flyout>
            <MenuFlyout>
                <MenuFlyoutItem Text="By rating" Tag="rating"/>
                <MenuFlyoutItem Text="By match" Tag="match"/>
                <MenuFlyoutItem Text="By distance" Tag="distance"/>
            </MenuFlyout>
        </AppBarButton.Flyout>
    </AppBarButton>
</StackPanel>

3. Open the MenuFlyout.

   Step 3 is important, because if you don't open it first, and you change the theme, then open, the correct theme will be applied.

4. Change the system theme from the Settings App > Personalization > Colors : Chose Color Mode - Light or Dark

5. Open the MenuFlyout.

6. Observe the strange color state of the Flyout, it's not Light or Dark theme, more of a broken dimmed or washed out state.

Expected behavior

The Flyout should display the correct theme based on what theme was selected by the OS at runtime, without the need to reopen the app or to not open the MenuFlyout first.

Screenshots

Light Theme normal state

Light Theme switched state

Dark Theme normal state

Dark Theme switched state

NuGet package version

WinUI 3 - Windows App SDK 1.2.2: 1.2.221209.1

Windows version

Windows 11 (22H2): Build 22621

Additional context

No response

[gabbybilka]

We were able to repro this simple case, looks like a theming issue on the background, thanks for filing.

[ThreeSevenths]

@gabbybilka I'm also hitting this with a Flyout with custom content. It seems that if the flyout isn't shown prior to the theme change it works correctly, but after, the style seems to be cached. Is there a workaround until this is fixed to notify the flyout to recreate the content or update its style references?

[mikernet]

This also affects content dialogs.

[bogdan-patraucean]

Based on my testing this issue seems to be fixed with latest 1.4.3 version of Windows App SDK.

[codendone]

A fix for this was checked in for WinAppSDK 1.6, and was included in 1.6-experimental1.