[MingW] error: 'WM_MOUSEHWHEEL' was not declared in this scope

[Oldes]

Compiling directX demos using MingW failes on missing WM_MOUSEHWHEEL definition.

x:\mingw64\bin\g++.exe  imgui\examples\directx9_example\imgui_impl_dx9.cpp -c  -o imgui_impl_dx9.o -Iimgui  -ld3d9
imgui\examples\directx9_example\imgui_impl_dx9.cpp: In function 'LRESULT ImGui_ImplWin32_WndProcHandler(HWND, UINT, WPARAM, LPARAM)':
imgui\examples\directx9_example\imgui_impl_dx9.cpp:256:10: error: 'WM_MOUSEHWHEEL' was not declared in this scope
     case WM_MOUSEHWHEEL:
          ^~~~~~~~~~~~~~

Possible fix is adding this code into header file:

#ifndef WM_MOUSEHWHEEL
#define WM_MOUSEHWHEEL                  0x020E
#endif

With this code it is possible to compile the demo without any other problems.

[ocornut]

Thank you @Oldes, this is now fixed in all examples.

I have a serious question even though it may look provocative or troll-ey, but why does ANYONE uses MingW? A good portion of the problems we have with building Windows examples are related to MingW, it's seems absurdly limited and stuck in the past. Is there any reason why a simple define that Microsoft added in 2007 wouldn't be supported by your version of MingW? Which version of MingW are you using? I am missing part of the picture here?

[Oldes]

Above was with this version:

g++.exe (x86_64-posix-seh-rev1, Built by MinGW-W64 project) 7.2.0
Copyright (C) 2017 Free Software Foundation, Inc.

For me MingW is a cross-platform compiler, I can use it to compile Windows app from Linux.. for example.

I just searched MingW files for the WM_MOUSEWHEEL define, and it is included in winuser.h file, but under condition:

#if _WIN32_WINNT >= 0x0600
#define WM_MOUSEHWHEEL 0x020e
#endif

So it is quite possible that better fix would be to do the same check in imgui source (where it is used) and remove the proposed fix above as it is more as a hack now.

[Flix01]

@Oldes: AFAIR that's just happening because WM_MOUSEWHEEL was introduced only after WindowsXP.

Usually when you program for Windows you specify your target version globally or in some kind of precompiled header through the two definitions WINVER and _WIN32_WINNT.

Please see: https://docs.microsoft.com/en-us/cpp/porting/modifying-winver-and-win32-winnt.

If you #define WINVER 0x0501 (or bigger) globally, then WM_MOUSEWHEEL should be present.

P.S. Mingw can still be useful to cross-compile for Windows (64 or 32 bit) from other systems.

[Edit:] Probably now everybody knows this already...

[ocornut]

Probably now everybody knows this already...

Well I didn't (but I am not a MingW user) and apparently other people don't, so it's good you posted that because next that I'll have an answer. I am finding it a little silly that MINGW doesn't doesn't so the latest version it supports.

[Flix01]

[Edit:] Probably now everybody knows this already...

@ocornut: I just meant the cross-compilation part, because I missed @Oldes's answer about that.
I didn't mean to be ironic in any way. Sorry.

I am finding it a little silly that MINGW doesn't set them to the latest version it supports.

Yes, but I'm not sure that all the older cl.exe compilers set these definitions in the correct way too.
I think that perhaps that used to be the default many years ago (when I still used Windows).

[ocornut]

The default value for e..g _WIN32_WINNT is set Microsoft's `<windows.h> to the latest supported SDK version, so it's surprising that MinGW doesn't do it.

In theory, we should be explicitly setting _WIN32_WINNT everywhere in the examples but this is just getting in the way of experimentation with modern stuff (e.g. DPI, DWM for viewport/docking).

The proposed change in #1708 is the theorical correct thing but in practice it seems that every portable application are defining chunks of windows header and use DLL loading themselves (as we are doing in the viewport branch) to allow compiling with older SDK (my current oldest target is VS2010) so it's fine to keep doing this.