How to use WinAPi in a C++ WinRT Component?

Question

I'm creating a C++ WinRT runtime component using Visual Studio 2022. I want to use functions like PeekMessage() to handle a basic message loop. However, I get the following errors:

error C3861: 'PeekMessage': identifier not found

I already have #include <Windows.h> at the top of the file, and I've also added #pragma comment(lib, "User32.lib").

Are there any limitations that prevent PeekMessage() from being used in a C++ WinRT component? If so, is there any workaround or recommended approach to use these APIs in this environment?

The OP' deleted question stackoverflow.com/questions/79687051/… — 3CEZVQ
– 3CEZVQ, Commented Jul 2 at 8:50
RTM PeekMessageA function (winuser.h): Windows 2000 Professional [desktop apps only]. — 3CEZVQ
– 3CEZVQ, Commented Jul 2 at 8:52
@3CEZVQ A desktop API can be called from a Windows Runtime component. — IInspectable
– IInspectable, Commented Jul 2 at 8:56
My previous question unintentionally focused on MessageBox, so I rewrote it to better reflect my intent; adding #undef WINAPI_FAMILY and #define WINAPI_FAMILY WINAPI_FAMILY_DESKTOP_APP in the WinRT component fixed the issue because the original setting was for UWP, but I want to use it with WinUI 3 in C#. — kinton
– kinton, Commented Jul 2 at 9:40

kinton · Accepted Answer · 2025-07-02 10:44:15Z

1

#undef WINAPI_FAMILY  
#define WINAPI_FAMILY WINAPI_FAMILY_DESKTOP_APP

in the WinRT component, it worked correctly. The original setting was for UWP, but I want to use it with WinUI 3 in C#.

answered Jul 2 at 10:44

kinton

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2 Comments

IInspectable Jul 2 at 12:43

Rather than fiddling with preprocessor symbols consider updating your MSBuild input (.vcxproj).,

kinton Jul 3 at 15:26

Thank you for your advice. I found the relevant section in the .vcxproj file and was able to fix it.

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