Qt Linguist Manual: Programmers

Loading Translations

 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);

This is how a simple main() function of a Qt application begins.

 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);

     QTranslator translator;
     translator.load("hellotr_la");
     app.installTranslator(&translator);

For a translation-aware application a translator object is created, a translation is loaded and the translator object installed into the application.

 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);

     QString locale = QLocale::system().name();

     QTranslator translator;
     translator.load(QString("arrowpad_") + locale);
     app.installTranslator(&translator);

For non-Latin1 strings in the sources you will also need for example:

     QTextCodec::setCodecForTr(QTextCodec::codecForName("utf8"));

In production applications a more flexible approach, for example, loading translations according to locale, might be more appropriate. If the TS files are all named according to a convention such as appname_locale, e.g. tt2_fr, tt2_de etc, then the code above will load the current locale's translation at runtime.

If there is no translation file for the current locale the application will fall back to using the original source text.

Note that if you need to programmatically add translations at runtime, you can reimplement QTranslator::translate().

 button = new QPushButton("&Quit", this);

 button = new QPushButton(tr("&Quit"), this);

 QPushButton::tr("&Quit")

 QObject::tr("&Quit")

 rbc = new QRadioButton(tr("Enabled", "Color frame"), this);

 rbh = new QRadioButton(tr("Enabled", "Hue frame"), this);

     exitAct = new QAction(tr("E&xit"), this);
     exitAct->setShortcut(tr("Ctrl+Q", "Quit"));

 /*
     TRANSLATOR FindDialog

     Choose Edit|Find from the menu bar or press Ctrl+F to pop up the
     Find dialog.

     ...
 */

 QString tr(const char *text, const char *comment, int n);

 tr("%n item(s) replaced", "", count);

 /*
     TRANSLATOR MyNamespace::MyClass

     Necessary for lupdate.

     ...
 */

 void some_global_function(LoginWidget *logwid)
 {
     QLabel *label = new QLabel(
             LoginWidget::tr("Password:"), logwid);
 }

 void same_global_function(LoginWidget *logwid)
 {
     QLabel *label = new QLabel(
             qApp->translate("LoginWidget", "Password:"),
             logwid);
 }

 QString FriendlyConversation::greeting(int greet_type)
 {
     static const char* greeting_strings[] = {
         QT_TR_NOOP("Hello"),
         QT_TR_NOOP("Goodbye")
     };
     return tr(greeting_strings[greet_type]);
 }

 static const char* greeting_strings[] = {
     QT_TRANSLATE_NOOP("FriendlyConversation", "Hello"),
     QT_TRANSLATE_NOOP("FriendlyConversation", "Goodbye")
 };

 QString FriendlyConversation::greeting(int greet_type)
 {
     return tr(greeting_strings[greet_type]);
 }

 QString global_greeting(int greet_type)
 {
     return qApp->translate("FriendlyConversation",
                             greeting_strings[greet_type]);
 }