[Bug] Accent Color and System Theme changes are not updated in Packaged WPF apps

[ShankarBUS]

This could be similar to #143. But this is an entirely different case.

There was an attempt to remove the app.manifest requirement (previously a mandatory need to detect the OS version) in 2c27fba. Despite removing the app.manifest requirement the bug has occurred to me (and I do have app manifest)

When the app is executed as an unpackaged application, there are no problems with theme/accent changes.
But when the same app is executed as a packaged (MSIX) application, the accent-color/system-theme changes are not perceived by the packaged application.

I can assure that this bug doesn't happen when the app is unpackaged.

Workaround

I used Reflection to invoke this internal method This won't work see #175 (comment)

private void ListenToSystemColorChanges()
{
    Type ColorsHelperType = Type.GetType("ModernWpf.ColorsHelper, ModernWpf");
    PropertyInfo CurrentProperty = ColorsHelperType.GetProperty("Current", BindingFlags.Static | BindingFlags.Public);
    object colorsHelperInstance = CurrentProperty.GetValue(null);
    MethodInfo ListenToSystemColorChangesMethod = ColorsHelperType.GetMethod("ListenToSystemColorChanges",
        BindingFlags.Instance | BindingFlags.NonPublic);
    ListenToSystemColorChangesMethod.Invoke(colorsHelperInstance, null);
}

[Kinnara]

Thanks for reporting. I'll look into it.

[Kinnara]

The cause seems to be UISettings doesn't raise any events in a packaged app, although its methods and properties work fine. Does the workaround actually work? ListenToSystemColorChanges is already called inside the library and calling it again shouldn't make any difference.

[ShankarBUS]

Yep, calling ListenToSystemColorChanges actually works. I'm really confused now. I don't know how it worked 😅

How can UISettings not fire events? We already use some other WinRT APIs in our app and all of them (except one event) work fine.

You can clone the ModernFlyouts repo and check it out yourself.

I thought there were problems with the OSVersionHelper & packaging.
So I manually called the ListenToSystemColorChanges method myself. It worked however. Are you sure UISettings is the problem here?

[Kinnara]

Yes, I'm fairly certain UISettings is the culprit, at least on Win10 2004. I tried ModernFlyouts and calling ListenToSystemColorChanges didn't seem to help—the settings window still didn't react to theme changes, for example.

[ShankarBUS]

Weird!!! There seems to be many issues with WinRT event triggering in .NET. Even an important API our app depends on (GSMTC) has this same problem. What should we do then?

How does the API work fine on unpackaged apps then?
It only happened while it was packaged. I thought the version checking didn't work but this seems to be out of our expertise, right?

[ShankarBUS]

Yep! It's what you say 😅.

[ShankarBUS]

I guess I will need to do another workaround

• Hook to registry changes (use WMI event watcher to watch changes in the reg key - "HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Themes\Personalize"'s value "AppsUseLightTheme" for theme changes)
• Handle window messages (i.e. WM_DWMCOLORIZATIONCOLORCHANGED for accent colour changes)

I already have a method to watch "SystemUsesLightTheme" so it will be relatively easy for me to workaround this until you find a way to fix this. (Referrence : SystemTheme.cs)

[Kinnara]

Fixed by 57b71b4.

[ShankarBUS]

Thanks @Kinnara!

[ShankarBUS]

Hey @Kinnara, a suggestion

While committing a fix regarding a issue, you can use the Fix\Fixed\Fixes #{issue-no} {Issue Title} format to automatically close those issues while committing.

It saves me a lot of time. Would be helpful for you maintaining a repo efficiently