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[edit] Internationalization

First of all: see the Internationalization section in the official docs, and look at the wxWidgets internal sample for the best reference.

For text problems only, be sure to check out poEdit for editing the gettext catalogs.

Other than text internationalization features are weak or missing. (e.g. Money formatting)

[edit] Data file organization

To be translated, your program must first have a catalog name, say "myprogram". This is just an identifier for your language files, nothing more.

There will be a directory on your system for installed languages, with a subdirectory for each language, for example 'nl' for Dutch.

• Windows : these directories typically come under the application directory. So, if your program is translated into Dutch there will be a file localedir\nl\myprogram.mo.
• Linux/Unix : generally {prefix}/share/locale/[lang code]/LC_MESSAGES/app_name.mo
• Mac OS X : {App name}.app/Contents/Resources/[lang code].lproj/app_name.mo

Your installer should take care of placing the language files in the appropriate directories.

You can check language codes here : http://xml.coverpages.org/iso639a.html

[edit] Getting started

Start by selecting which strings are translatable and mark them with the _() macro.

// example : 'Hello World' is flagged as translatable
wxMessageBox( _("Hello World") );

Once translatable strings are marked, you can extract the strings into a catalog using GNU gettext (you'll need to have it installed to extract the string catalog using the UNIX commands provided below, however your user will not need to have it installed since support is built inside wx).

# example sh script to generate catalog file
# it searches for strings marked with _() in all .cpp files in directory ./src
# the generated file is called 'app_name.pot' and is generated in ./po
CPP_FILE_LIST=`find ./src -name '*.cpp' -print`
xgettext -d app_name -s --keyword=_ -p ./po -o app_name.pot $CPP_FILE_LIST

Catalog editors may also be able to extract strings, however the process is less automatized this way.

[edit] Translating in poEdit

Once you have the .pot catalog, you can edit it in your favorite catalog editor. Here poEdit is the one used.

[edit] Starting a translation to a new language

• Use menu 'File > New catalog from POT file'
• Select the .pot catalog file
• Enter appropriate information about yourself and the language
• Translate the strings and save the file as a .po.

[edit] Updating an existing translation with latest strings updates

• Open the .po file in poEdit
• Choose menu 'Catalog > update from POT file'
• Select the .pot catalog file

[edit] Getting it inside your app

Use code similar to this :

wxLocale* locale;
long language;
 
void initLanguageSupport()
{
    language =  wxLANGUAGE_DEFAULT;
 
    // fake functions, use proper implementation
    if( userWantsAnotherLanguageThanDefault() )
        language = getUsersFavoriteLanguage();
       
    // load language if possible, fall back to english otherwise
    if(wxLocale::IsAvailable(language))
    {
	locale = new wxLocale( language, wxLOCALE_CONV_ENCODING );
 
        #ifdef __WXGTK__
        // add locale search paths
        locale->AddCatalogLookupPathPrefix(wxT("/usr"));
        locale->AddCatalogLookupPathPrefix(wxT("/usr/local"));
        wxStandardPaths* paths = (wxStandardPaths*) &wxStandardPaths::Get();
        wxString prefix = paths->GetInstallPrefix();
        locale->AddCatalogLookupPathPrefix( prefix );
        #endif
 
        locale->AddCatalog(wxT("app_name"));
 
	    if(! locale->IsOk() )
	    {
		    std::cerr << "selected language is wrong" << std::endl;
		    delete locale;
		    locale = new wxLocale( wxLANGUAGE_ENGLISH );
                    language = wxLANGUAGE_ENGLISH;
	    }
    }
    else
    {
        std::cout << "The selected language is not supported by your system."
                  << "Try installing support for this language." << std::endl;
	locale = new wxLocale( wxLANGUAGE_ENGLISH );
        language = wxLANGUAGE_ENGLISH;
    }
 
}

For other languages to work, you'll need your .po files compiled as .mo files (.mo translation files are binary versions of .po files) . poEdit will do it automatically upon saving if the appropriate option is checked in the preferences.

[edit] Support for RTL (right-to-left) languages

There is currently no support for this in wxWidgets but we should really add it. It seems like it should be relatively simple to do under Windows, as calling SetProcessDefaultLayout() does the major part of the job, see this thread for more details. RTL languages are also supported by Mac OS and by GTK2 but details are lacking. Yudit is the best example of right to left languages.

You can check Filezilla 3 FTP client as an example of RTL support

See also: Unicode, WxWidgets Source Oddities