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Supporting Application-Specific Language Settings

Your application can support a different set of user interface languages from those supported by the target operating system. This topic discusses this type of support, using snippets from complete samples.

Interpret User's Language Preference

Your application must first determine which user interface language to display, based on user preference. The code can read the settings from a configuration file or from registry settings.

The following example defines two functions used to interpret the user's language preference. The first function illustrates the reading of a delimited list of languages from a file, represented in the code as "langs.txt". The delimiters supported in the sample are ",",";";"." and " ". The second function converts the string read from the file to a multi-string value. This operation is necessary because the MUI functions used to set languages only accept multi-string values.


BOOL GetMyUserDefinedLanguages(WCHAR * langStr, DWORD langStrSize)
{
    BOOL rtnVal = FALSE;
    // Very simple implementation - assumes that first 'langStrSize' characters of the
    // L".\\langs.txt" file comprises a string of one or more languages.
    HANDLE langConfigFileHandle = CreateFileW(L".\\langs.txt", GENERIC_READ, 0,
                                    NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    if(langConfigFileHandle != INVALID_HANDLE_VALUE)
    {
        // Clear the input variables.
        DWORD bytesActuallyRead = 0;
        if(ReadFile(langConfigFileHandle, langStr, langStrSize*sizeof(WCHAR), &bytesActuallyRead, NULL)
           && bytesActuallyRead > 0)
        {
            rtnVal = TRUE;
            DWORD nullIndex = (bytesActuallyRead/sizeof(WCHAR) < langStrSize)
                              ? bytesActuallyRead/sizeof(WCHAR) : langStrSize;
            langStr[nullIndex] = L'\0';
        }
        CloseHandle(langConfigFileHandle);
    }
    return rtnVal;
}
BOOL ConvertMyLangStrToMultiLangStr(WCHAR * langStr, WCHAR * langMultiStr, DWORD langMultiStrSize)
{
    BOOL rtnVal = FALSE;
    size_t strLen = 0;
    rtnVal = SUCCEEDED(StringCchLengthW(langStr, USER_CONFIGURATION_STRING_BUFFER*2, &strLen));
    if(rtnVal && strLen > 0 && langMultiStr && langMultiStrSize > 0)
    {
        WCHAR * langMultiStrPtr = langMultiStr;
        WCHAR * last = langStr + (langStr[0] == 0xFEFF ? 1 : 0);
        WCHAR * context = last;
        WCHAR * next = wcstok_s(last,L",; :",&context);
        while(next && rtnVal)
        {
            // Make sure you validate the user input.
            if(SUCCEEDED(StringCchLengthW(last, LOCALE_NAME_MAX_LENGTH, &strLen))
               && IsValidLocaleName(next))
            {
                langMultiStrPtr[0] = L'\0';
                rtnVal &= SUCCEEDED(StringCchCatW(langMultiStrPtr,
                                    (langMultiStrSize - (langMultiStrPtr - langMultiStr)), next));
                langMultiStrPtr += strLen + 1;
            }
            next = wcstok_s(NULL, L",; :", &context);
            if(next)
                last = next;
        }
        // Make sure there is a double null term for the multi-string.
        if(rtnVal && (langMultiStrSize - (langMultiStrPtr - langMultiStr)))
        {
            langMultiStrPtr[0] = L'\0';
        }
        else // Fail and guard anyone whom might use the multi-string.
        {
            langMultiStr[0] = L'\0';
            langMultiStr[1] = L'\0';
        }
    }
    return rtnVal;
}


Set the Application Language

After reading the language preference information, the application code must use the retrieved setting to set the application language. On Windows 7 and later, the application can set the language at the process level by calling the SetProcessPreferredUILanguages function.


DWORD langCount = 0;
// Using SetProcessPreferredUILanguages is recommended for new applications (esp. multi-threaded applications).
if(!SetProcessPreferredUILanguages(MUI_LANGUAGE_NAME, userLanguagesMultiString, &langCount) || langCount == 0)
{
    swprintf_s(displayBuffer, SUFFICIENTLY_LARGE_ERROR_BUFFER,
               L"FAILURE: Unable to set the user defined languages, last error = %d.", GetLastError());
    MessageBoxW(NULL, displayBuffer, L"HelloMUI ERROR!", MB_OK | MB_ICONERROR);
    return 1; // Exit.
}


On Windows Vista and later, the application language is set at the thread level by calling the SetThreadPreferredUILanguages function.


DWORD langCount = 0;
// The following line of code is supported on Windows Vista and later.
if(!SetThreadPreferredUILanguages(MUI_LANGUAGE_NAME, userLanguagesMultiString, &langCount) || langCount == 0)
{
    swprintf_s(displayBuffer, SUFFICIENTLY_LARGE_ERROR_BUFFER,
               L"FAILURE: Unable to set the user defined languages, last error = %d.", GetLastError());
    MessageBoxW(NULL, displayBuffer, L"HelloMUI ERROR!", MB_OK | MB_ICONERROR);
    return 1; // Exit.
}
return 1;


Related topics

Setting Application Language Preferences
MUI: Application-Specific Settings Sample (Windows Vista)
MUI: Application-Specific Settings Sample (Pre-Windows Vista)

 

 

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