Forward declare HINSTANCE and friends

Question

Is there a way to forward-declare the HINSTANCE type from the WinAPI without including the full (and big) windows.h header?

For example, if I have a class RenderWindow which owns an HINSTANCE mInstance, i will have to include windows.h in RenderWindow.h. So everything that needs RenderWindow also has to include windows.h.

I tried including windef.h but this seems to need some things from windows.h. :-( If I can't forward declare it, is there at least a portable way to use something like long mInstance in RenderWindow instead of HINSTANCE?

Answer 1

HINSTANCE is declared in WinDef.h as typedef HINSTANCE__* HINSTANCE;

You may write in your headers:

#ifndef _WINDEF_
class HINSTANCE__; // Forward or never
typedef HINSTANCE__* HINSTANCE;
#endif

You will get compilation errors referencing a HINSTANCE when WinDef.h is not included.

Answer 2

You could declare it void* and cast the errors away. This is close to a never-ending battle though, sooner or later you'll get tripped up. Use pre-compiled headers so you don't care about the size of windows.h

stdafx.h:

#define WIN32_LEAN_AND_MEAN
#include <windows.h>