Get Windows display Language

Question

I tried several things and according to following post, it should work but I can't get the Windows display language.

https://stackoverflow.com/questions/52849233/getuserpreferreduilanguages-never-returns-more-than-two-languages

Has anything changed in Windows 11?
I selected German (Luxemburg) but I can't get the value which should be 4103 according to the language id list:

https://renenyffenegger.ch/notes/Windows/development/Internationalization/language

My settings (I newly logged in and restartet the pc several times):

My code (also tried GetUserPreferredUILanguages):

auto a = GetUserDefaultUILanguage();    
auto b = GetSystemDefaultUILanguage();    
auto c = GetThreadUILanguage();    
auto d = GetUserDefaultLangID();    
auto e = GetSystemDefaultLangID();    
auto f = GetUserDefaultLCID();    
auto g = GetSystemDefaultLCID();     
ULONG pulNumLanguages = 0;    
ULONG pcchLanguagesBuffer = 80;    
wchar_t pwszLanguagesBuffer[80];    GetSystemPreferredUILanguages(MUI_MACHINE_LANGUAGE_SETTINGS, &pulNumLanguages, pwszLanguagesBuffer, &pcchLanguagesBuffer);     
auto h = pwszLanguagesBuffer + 6;

Answer 1

Oh man, it took forever, so I might as well post it as it suits me.

// Returns only the first null terminated string (selected Windows display language).
std::basic_string<TCHAR> GetWindowsDisplayLanguageFromRegistry()
{
    LPCTSTR subKey = _T("Control Panel\\International\\User Profile\\");
    LPCTSTR valueName = _T("Languages");
    DWORD bufferSize = 0;

    // Check buffer size.
    if (RegGetValue(HKEY_CURRENT_USER, subKey, valueName, RRF_RT_REG_MULTI_SZ, nullptr, nullptr, &bufferSize) == ERROR_SUCCESS)
    {
        //  Manage memory.
        std::vector<TCHAR> value(bufferSize / sizeof(TCHAR));

        // Get registry key value.
        if (RegGetValue(HKEY_CURRENT_USER, subKey, valueName, RRF_RT_REG_MULTI_SZ, nullptr, &value[0], &bufferSize) == ERROR_SUCCESS)
        {
            // Ensure null-termination.
            value[bufferSize / sizeof(TCHAR)] = _T('\0');

            std::basic_string<TCHAR> firstString(value.data());

            return firstString;
        }
    }

    return std::basic_string<TCHAR>();
}