Function ImFileOpen

src/imgui/imgui.cpp:2408–2430

#ifndef IMGUI_DISABLE_DEFAULT_FILE_FUNCTIONS

ImFileHandle ImFileOpen(const char* filename, const char* mode)
{
#if defined(_WIN32) && !defined(IMGUI_DISABLE_WIN32_FUNCTIONS) && (defined(__MINGW32__) || (!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);

    // Use stack buffer if possible, otherwise heap buffer. Sizes include zero terminator.
    // We don't rely on current ImGuiContext as this is implied to be a helper function which doesn't depend on it (see #7314).
    wchar_t local_temp_stack[FILENAME_MAX];
    ImVector<wchar_t> local_temp_heap;
    if (filename_wsize + mode_wsize > IM_ARRAYSIZE(local_temp_stack))
        local_temp_heap.resize(filename_wsize + mode_wsize);
    wchar_t* filename_wbuf = local_temp_heap.Data ? local_temp_heap.Data : local_temp_stack;
    wchar_t* mode_wbuf = filename_wbuf + filename_wsize;
    ::MultiByteToWideChar(CP_UTF8, 0, filename, -1, filename_wbuf, filename_wsize);
    ::MultiByteToWideChar(CP_UTF8, 0, mode, -1, mode_wbuf, mode_wsize);
    return ::_wfopen(filename_wbuf, mode_wbuf);
#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; }