Internationalization Guide


This guide will explain how to create internationalization support (ie: dictionaries files) and to use it to translate an application.

This will be done in two steps:
  • Using qilinguist, a qibuild tool, to create and generate a dictionary file.
  • Setting up the C++ application to find and translate strings.

qiLinguist How to use qilinguist

Configuration of translation files

First of all you need to create a po directory into your root application folder and in it.

  |_ po
  |_ src
    |_ main.cpp
    |_ hello.cpp
  |_ headers
    |_ hello.h


Into the you MUST add the relative path of all files you want to translate. For example, if you only have translation in hello.cpp, the looks like:

              $ cat po/


Add qilinguist configurations

You need to add a translate node into the qiproject.xml file. This configuration is used by qilinguist to generate translation files and installation rules.

The qiproject.xml will look like:

              <project name="helloApp">
  <translate name="helloApp" domain="hello" linguas="fr_FR en_US" tr="gettext" />

Tag definitions:
  • name : The name of the application or library.
  • domain : The name of the generated dictionary.
  • linguas : A list of all locales supported formatted as xx_XX (country and language code)
  • tr : Define if you use gettext or QT internationalization (value can be: “gettext” or “qt”).

Dictionaries will be install into:



How to use qilinguist

Everything is ready to generate and edit dictionaries.

There are two commands to use:
  • qilinguist update: finds the translatable strings in the specified source, header and generates or updates .po (or .ts) translation files.


Some po configuration isn’t correct (example: jp_JP.po, fr_FR.po). You need to replace

                 "Content-Type: text/plain; charset=ASCII\n"



                 "Content-Type: text/plain; charset=UTF-8\n"

  • qilinguist release: produces MO files out of PO ones or QM files out of TS ones. The format of those files is a binary format that is used by the localized application.

First of all you need to generate or update translatable files by using qilinguist update . This will create files (into po folder) you can edit using Linguist from the Qt SDK or poedit for instance.

Once you have translated those files, you need to compile them by using qilinguist release .

How to internationalize C++ applications

Update CMakeLists.txt

You must add the qi_create_trad(projectname “po”) into the CMakeLists.txt root file.

              cmake_minimum_required(VERSION 2.8)
qi_create_trad(yourProjectName "po")


Set and configure qi::Translator

You need to get a default qi::Translator , then you MUST set the default domain and current locale.

  • Get default Translator ( qi::defaultTranslator ) with name the name of the application or library.
  • Set default domain ( qi::Translator::setDefaultDomain ) with domain the name of the generated dictionary.
  • Set current locale ( qi::Translator::setCurrentLocale ) with locale the name of the default locale formatted as xx_XX (country and language code)


The name and domain must be the same as those define into the qiproject.xml


The locale must be a locale supported and define into the qiproject.xml, otherwise it will fallback to the default value.

You can add some domains by using qi::Translator::addDomain . This will allow qi::Translator to look it multiple dictionary.

You can change the locale you want to use by calling qi::Translator::setCurrentLocale . This function allows you to set and switch language at runtime.

How to translate sentences

You have two choices to translate your sentences:
  • Call qi::Translator::translate .
  • Call qi::tr .

All sentences will be parsed when calling qilinguist update, then generate translation files (ie: po/ts files). Then, at runtime qi::Translator::translate will look for translation regarding initialization done in the last paragraph.

You can use boost format to add variable that won’t be translate:

              std::string name = "nao";
std::string msgTranlate = boost::format(qi::tr("Hello my name is %s") % name);



 * Copyright (c) 2013 Aldebaran Robotics. All rights reserved.
 * Use of this source code is governed by a BSD-style license that can be
 * found in the COPYING file.

#include <iostream>

#include <qi/application.hpp>
#include <qi/os.hpp>
#include <qi/translator.hpp>

int main(int argc, char *argv[])
  qi::Application app(argc, argv);

  qi::Translator &tl = qi::defaultTranslator(;

  std::cout << qi::tr("Hi, my name is NAO.") << std::endl;
  std::cout << qi::tr("Where is Brian?") << std::endl;
  std::cout << qi::tr("Brian is in the kitchen.") << std::endl;

  std::cout << qi::tr("Hi, my name is NAO.") << std::endl;
  std::cout << qi::tr("Where is Brian?") << std::endl;
  std::cout << qi::tr("Brian is in the kitchen.") << std::endl;

  std::cout << qi::tr("Brian is in the kitchen.", "", "en_US") << std::endl;
  std::cout << qi::tr("Brian is in the kitchen.", "", "fr_FR") << std::endl;