identifier "ImGui_ImplWin32_WndProcHandler" is undefined about imgui

[ocornut]

but an error haunts me

If you search for ImGui_ImplWin32_WndProcHandler in the codebase,

(1) The first hit says:

// Copy this line into your .cpp file to forward declare the function.
extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

(2) All five examples demonstrating how to use imgui_impl_win32 are doing exactly that:

// Forward declare message handler from imgui_impl_win32.cpp
extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

[...]
LRESULT WINAPI WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    if (ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam))
        return true;

(3)
The "Getting Started" guide:
https://github.com/ocornut/imgui/wiki/Getting-Started#example-if-you-are-using-raw-win32-api--directx11
Does the same thing:

extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
if (ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam))
    return true;

So here's your answer..