Supporting several languages is a key point to increase the audience of an application. We will see what is needed in Qt to enable internationalization and how to ensure all the components can be translated. We will also see the tools available for the translators and how to use them.
Presentation by Benjamin Poulain held during Qt Developer Days 2009.
http://qt.nokia.com/developer/learning/elearning
2. Who is Benjamin Poulain at Nokia?
• first support engineer
– Linux and Mac OS X
• now Webkit developer
• pet projects
– graphical tablet
– Cocoa support
2
3. What do I do after work?
• some hacking
– web applications
• lots of sport: running, cycling, climbing
I am not so good on a snowboard
4. Why do I work on translations?
• my family do not speak english
➡ need for localized software
• work on
– tutorial in french
– translation of Qt Creator
– french community of Qt
5. What are we gonna do today?
• Why bother?
• Translating your application
• Tools for translators
• Going further
• Conclusion
6. What are we gonna do today?
• Why bother?
• Translating your application
• Tools for translators
• Going further
• Conclusion
7. Translations increase your user base
Everybody speaks English. right?
Native speaker
Secondary
Do not understand English
writing an application is difficult ➜ spread it
8. What are we gonna do today?
• Why bother?
• Translating your application
– Simple application
– UI
– Source
– Integrate the translation
• Tools for translators
• Going further
• Conclusion
10. How do we translate the application?
Internationalization workflow:
1) write code ready for translation
2) extract strings
3) translate
4) compile strings
11. What are we gonna do today?
• Why bother?
• Translating your application
– Simple application
– UI
– Source
– Integrate the translation
• Tools for translators
• Going further
• Conclusion
12. The .ui files are the biggest part
• most strings are in the .ui
• this is what is seen by the user
• good news: work out of the box
- string extraction
- translation
13. What are we gonna do today?
• Why bother?
• Translating your application
– Simple application
– UI
– Source
– Integrate the translation
• Tools for translators
• Going further
• Conclusion
14. Translate the strings with tr()
• QObject::tr() translate a string:
trayIcon.showMessage("new message", "you have too many mail");
trayIcon.showMessage(tr("new message"), tr("you have too many mail"));
• works great with QString::arg():
QString::number(userCount) + "users online";
tr("%n user(s) online").arg(userCount);
15. Provide some context for short strings
What are 1, 2? tr("The %1 is %2").arg(...);
16. Provide some context for short strings
What are 1, 2? tr("The %1 is %2").arg(...);
3 ways to add context:
– luck
– context in tr():
tr("The %1 is %2", "The <extension> is <state>").arg(...);
– comment in code
//: The <extension> is <state>
tr("The %1 is %2").arg(...);
17. How to mark strings for translations?
• tr() returns QString
• QT_TR_NOOP marks for translation
• translated later with tr()
example:
char *const EDITOR = QT_TR_NOOP("emacs");
void function() {
(...)
QString editor = tr(EDITOR);
(...)
}
18. What are we gonna do today?
• Why bother?
• Translating your application
– Simple application
– UI
– Source
– Integrate the translation
• Tools for translators
• Going further
• Conclusion
19. Applications use a compiled version of the translation
• lrelease compiles .ts in .qm
• .qm is the binary format for release
• fast lookup
• not into the binary
20. A translator must be installed
• QTranslator
- translate the strings
- load the .qm file:
QTranslator uglySnakeTranslator;
uglySnakeTranslator.load("uglysnake_" + QLocale::system().name(),
QCoreApplication::applicationDirPath());
app.installTranslator(&uglySnakeTranslator);
21. What are we gonna do today?
• Why bother?
• Translating your application
• Tools for translators
• Going further
• Conclusion
22. There are two kinds of tools for translators
• offline ➜ Qt Linguist
• online ➜ Pootle, ...
24. Linguist is great but need to be distributed
• support multiple languages (simultaneously)
• great integration with Qt
• integration with the UI files:
• errors are spoted imediately
• full context
but: need to be distributed
26. Pootle is great, but offer no integration
• no need to distribute
• easier for amateur
but: no integration (ui files!)
27. What are we gonna do today?
• Why bother?
• Translating your application
• Tools for translators
• Going further
– “context”
– tricky UI
– change the language
– pitfalls
• Conclusion
28. One word, multiple concepts
noun édition
edit
verb éditer
• short text ➜ context
tr("edit", "verb");
tr("edit", "noun");
• also in designer
29. Comments does not disambiguate the strings
• works:
QString a = tr("edit", "N97");
QString b = tr("edit", "N900");
• do not work
//: N97
QString a = tr("edit");
//: N900
QString b = tr("edit");
• why?
31. Comments does not disambiguate the strings
• works:
QString a = tr("edit", "N97");
QString b = tr("edit", "N900");
• do not work:
//: N97
QString a = tr("edit");
//: N900
QString b = tr("edit");
• solution:
//: N97
QString a = tr("edit", "phoneA");
//: N900
QString b = tr("edit", "phoneB");
32. What are we gonna do today?
• Why bother?
• Translating your application
• Tools for translators
• Going further
– “context”
– tricky UI
– change the language
– pitfalls
• Conclusion
33. The translation should fit the widgets
• the layouts adapt the widgets
• problems:
- fixed size
- phone screen
34. Some images need a translation
• localize icons, images, etc
• qresource support locale:
<qresource lang="fr">
<file>burnIcon.png</file>
</qresource>
35. What if you want multiple UI?
• cultural conventions
• phone screens
• right to left interface
✓ Solution: QUiLoader to load the UI
X difficult to maintain
X difficult to document
36. What are we gonna do today?
• Why bother?
• Translating your application
• Tools for translators
• Going further
– “context”
– tricky UI
– change the language
– pitfalls
• Conclusion
37. What if the language is changed after the start?
• examples:
- phone
- public terminal
- MS Windows applications
38. Everything needs a new translation
• LanguageChange event on ::installTranslator()
• QWidget::changeEvent() to catch the event
• UI responds to retranslateUI()
• manual update for the code
void SettingsPanel::changeEvent(QEvent *e)
{
if (e->type() == QEvent::LanguageChange) {
ui->retranslateUi(this);
updateSpeedDescription();
}
QWidget::changeEvent(e);
}
39. When to change the translators?
• LocaleChange event to the active window
➡ install event filter on QApplication
➡ change the translators
40. What are we gonna do today?
• Why bother?
• Translating your application
• Tools for translators
• Going further
– “context”
– tricky UI
– change the language
– pitfalls
• Conclusion
41. Translate on painting is not a good strategy
char languageList[] = { QT_TR_NOOP("english"),
QT_TR_NOOP("german") };
if (language == "english”) {
...
void paintEvent(QEvent *) {
QString toShow = tr(m_language);
...
}
list sorted alphabetically:
✓ Solution: use classes for identity, not strings
42. The source might not be in Latin 1
• tr() uses Latin 1 by default
tr("Qt est génial"); // might fail
✓ Solution 1: use English for the source
✓ Solution 2:
- QTextCodec::setCodecForTr()
- CODECFORTR = UTF-8
43. Mac uses an ordered list of language
• Mac OS X
- ordered list of languages
Not accurate
• language selection:
QTranslator uglySnakeTranslator;
uglySnakeTranslator.load("uglysnake_" + QLocale::system().name(),
QCoreApplication::applicationDirPath());
app.installTranslator(&uglySnakeTranslator);
✓ Solution: iterate over the languages of core foundation
44. What are we gonna do today?
• Why bother?
• Translating your application
• Tools for translators
• Going further
• Conclusion
45. Qt makes translation easy
• Internationalization is important
• Qt already solves the problems
• Minimal changes are needed in the code
– tr() every string
– provide context for short strings
➡ think about it when you develop
