https://bugs.winehq.org/show_bug.cgi?id=55859
--- Comment #15 from Zeb Figura z.figura12@gmail.com --- (In reply to Alex Henrie from comment #13)
(In reply to Zeb Figura from comment #11)
(In reply to Alex Henrie from comment #9)
difxappa.dll is closed-source and copyright Microsoft. Definitely off limits.
Well, it's off limits if we intend to reimplement it, as I understand. But I don't think reimplementing difxapp is an option. It's shipped by installers, and due to the way MSI works, it's not going to have the same name at runtime.
Isn't there a possibility that Microsoft might start distributing difxappa.dll with Windows, or that it shares code with some other DLL that we definitely do want to reimplement?
Well, Microsoft deprecated DIFx back in 2016, so I don't think it's very likely at this point.
It's also worth noting that decompilation isn't the only thing that's off-limits in terms of determining what a native DLL does; checking what calls it makes into Wine is also off-limits. When it comes to native DLLs, either they work or they don't.