Translating Qt Applications

09/12/09

Translating Qt applicationsIt does not have to be boring ;-)

Who is Benjamin Poulain at Nokia?

2

• first support engineer

– Linux and Mac OS X

• now Webkit developer

• pet projects

– graphical tablet

– Cocoa support

What do I do after work?

• some hacking

– web applications

• lots of sport: running, cycling, climbing

I am not so good on a snowboard

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

What are we gonna do today?

• Why bother?

• Translating your application

• Tools for translators

• Going further

• Conclusion


• Why bother?



• Going further

• Conclusion

Translations increase your user base

Everybody speaks English. right?

Do not understand English

Secondary

Native speaker

writing an application is difficult ➜ spread it


• Why bother?• Translating your application

– Simple application– UI– Source– Integrate the translation

• Tools for translators• Going further• Conclusion

Ugly Snake is a mini game in Qt

How do we translate the application?

1) write code ready for translation

2) extract strings

3) translate

4) compile strings

Internationalization workflow:





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





Translate the strings with tr()

• QObject::tr() translate a string:trayIcon.showMessage("new message", "you have too many mail");

• works great with QString::arg():

tr("%n user(s) online").arg(userCount);

QString::number(userCount) + "users online";

trayIcon.showMessage(tr("new message"), tr("you have too many mail"));

Provide some context for short strings

tr("The %1 is %2").arg(...);What are 1, 2?

Provide some context for short strings

3 ways to add context:

– luck

– context in tr():

– comment in code

tr("The %1 is %2").arg(...);What are 1, 2?

tr("The %1 is %2", "The <extension> is <state>").arg(...);

//: The <extension> is <state>tr("The %1 is %2").arg(...);

How to mark strings for translations?

• tr() returns QString

• QT_TR_NOOP marks for translation

• translated later with tr()

char *const EDITOR = QT_TR_NOOP("emacs");

void function() { (...) QString editor = tr(EDITOR); (...)}

example:





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

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);


• Why bother?



• Going further

• Conclusion

There are two kinds of tools for translators

• offline ➜ Qt Linguist

• online ➜ Pootle, ...

Presentation of Linguist

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

Presentation of Pootle

Pootle is great, but offer no integration

• no need to distribute

• easier for amateur

but: no integration (ui files!)


• Why bother?• Translating your application• Tools for translators• Going further

– “context”– tricky UI– change the language– pitfalls

• Conclusion

One word, multiple concepts

edit

édition

éditer

noun

verb

tr("edit", "verb");tr("edit", "noun");

• short text ➜ context

• also in designer

Comments does not disambiguate the strings

QString a = tr("edit", "N97");QString b = tr("edit", "N900");

• works:

• do not work//: N97QString a = tr("edit");

//: N900QString b = tr("edit");

• why?

Understanding context and disambiguation

QPushButton::tr("edit", "verb");

context

disambiguation

QCoreApplication::translate("QPushButton", "edit", "verb");

QTranslator::translate("QPushButton", "edit", "verb");

context source disambiguation ➜ result

QPushButton edit verb ➜ editer

QPushButton edit ➜

source

Comments does not disambiguate the strings

QString a = tr("edit", "N97");QString b = tr("edit", "N900");

• works:

• do not work://: N97QString a = tr("edit");

//: N900QString b = tr("edit");

• solution://: N97QString a = tr("edit", "phoneA");

//: N900QString b = tr("edit", "phoneB");




• Conclusion

The translation should fit the widgets

• the layouts adapt the widgets

• problems:

- fixed size- phone screen

Some images need a translation

• localize icons, images, etc

• qresource support locale:

<qresource lang="fr"> <file>burnIcon.png</file></qresource>

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




• Conclusion

What if the language is changed after the start?

• examples:

- phone

- public terminal

- MS Windows applications

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);}

When to change the translators?

• LocaleChange event to the active window

➡ install event filter on QApplication

➡ change the translators




• Conclusion

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

The source might not be in Latin 1

• tr() uses Latin 1 by default

✓ Solution 1: use English for the source

✓ Solution 2:

- QTextCodec::setCodecForTr()

- CODECFORTR = UTF-8

tr("Qt est génial"); // might fail

Mac uses an ordered list of language

• Mac OS X

- ordered list of languages

• language selection:QTranslator uglySnakeTranslator;uglySnakeTranslator.load("uglysnake_" + QLocale::system().name(), QCoreApplication::applicationDirPath());app.installTranslator(&uglySnakeTranslator);

Not accurate

✓ Solution: iterate over the languages of core foundation


• Why bother?



• Going further

• Conclusion

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

Technology

Translating Qt Applications