I'm using both win32 and directx when making a game engine + game. Win32 directly needs the window header and directx header includes it aswell.
It is a decently-sized project and I'd rather avoid exposing the windows header to the rest of the project(s) if possible. Is there any good way to bypass this issue?
There's only one practical way to avoid exposing a header that your implementation code needs, and that's to include the header only in the implementation.
That's called the compiler firewall idiom.
Often (but this is not always required) one exposes a class with a member pointer to an object of declared but incomplete type, that is defined only in the implementation file. This is usually called the PIMPL, short for pointer to implementation, idiom, but it has also been called the handle-body idiom and the Cheshire Cat idiom.
One alternative to a PIMPL pointer is to declare a factory function in the header file, where that factory function produces objects of some known type Base, and in the implementation file let it produce an object of a derived type Derived that contains the dependencies on the undesirable header.
Another alternative, but then you might run into thread safety issues, is to just provide functions that operate on a static state variable. I.e. a singleton, a global. Yes this is as bad as it sounds (even though a whole programming language, Modula-2, was based on the idea), but it certainly is a technical option, and might be preferable in certain situations.
