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?