Function ImFileOpen

ImGUI GLFW Tutorial/imgui/imgui.cpp:1543–1558

#ifndef IMGUI_DISABLE_DEFAULT_FILE_FUNCTIONS

ImFileHandle ImFileOpen(const char* filename, const char* mode)
{
#if defined(_WIN32) && !defined(IMGUI_DISABLE_WIN32_FUNCTIONS) && !defined(__CYGWIN__) && !defined(__GNUC__)
    // We need a fopen() wrapper because MSVC/Windows fopen doesn't handle UTF-8 filenames.
    // Previously we used ImTextCountCharsFromUtf8/ImTextStrFromUtf8 here but we now need to support ImWchar16 and ImWchar32!
    const int filename_wsize = ::MultiByteToWideChar(CP_UTF8, 0, filename, -1, NULL, 0);
    const int mode_wsize = ::MultiByteToWideChar(CP_UTF8, 0, mode, -1, NULL, 0);
    ImVector<ImWchar> buf;
    buf.resize(filename_wsize + mode_wsize);
    ::MultiByteToWideChar(CP_UTF8, 0, filename, -1, (wchar_t*)&buf[0], filename_wsize);
    ::MultiByteToWideChar(CP_UTF8, 0, mode, -1, (wchar_t*)&buf[filename_wsize], mode_wsize);
    return ::_wfopen((const wchar_t*)&buf[0], (const wchar_t*)&buf[filename_wsize]);
#else
    return fopen(filename, mode);
#endif
}

// We should in theory be using fseeko()/ftello() with off_t and _fseeki64()/_ftelli64() with __int64, waiting for the PR that does that in a very portable pre-C++11 zero-warnings way.
bool    ImFileClose(ImFileHandle f)     { return fclose(f) == 0; }