How to listen for theme changes?

[jhinder]

We need to listen for theme changes in our application in order to call FrameworkElement.UpdateDefaultStyle on some elements in accordance with the summary tag of the method: https://github.com/dotnet/wpf/blob/v6.0.12/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Generated/FrameworkElement.cs#L124-L129

How can we properly listen for theme changes? The documentation doesn't say this at all. Right now we listen for the SystemEvents.UserPreferenceChanged event and filter on the Category property in order to be notified about all color or visual style changes.
In classic Win32 you'd probably listen for some messages like WM_THEMECHANGED and WM_SYSCOLORCHANGE, but we can't easily do that because we have no WPF window that can intercept and handle such messages. We'd have to create an invisible native window that translates the Win32 messages into CLR events, which is also not ideal.

[miloush]

What's wrong with using SystemEvents.UserPreferenceChanged for UserPreferenceCategory.VisualStyle?

We'd have to create an invisible native window

That's how it's done in Win32 and that's exactly what SystemEvents does: https://referencesource.microsoft.com/#System/compmod/microsoft/win32/SystemEvents.cs,45b5269c979ec097