QTranslator Class

Detailed Description

An object of this class contains a set of translations from a source language to a target language. QTranslator provides functions to look up translations in a translation file. Translation files are created using Qt Linguist.

The most common use of QTranslator is to: load a translation file, and install it using QCoreApplication::installTranslator().

Here's an example main() function using the QTranslator:

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

     QTranslator translator;
     // look up e.g. :/i18n/myapp_de.qm
     if (translator.load(QLocale(), QLatin1String("myapp"), QLatin1String("_"), QLatin1String(":/i18n")))
         QCoreApplication::installTranslator(&translator);

     QPushButton hello(QCoreApplication::translate("main", "Hello world!"));
     hello.resize(100, 30);

     hello.show();
     return app.exec();
 }

Note that the translator must be created before the application's widgets.

Most applications will never need to do anything else with this class. The other functions provided by this class are useful for applications that work on translator files.

Looking up Translations

It is possible to look up a translation using translate() (as tr() and QCoreApplication::translate() do). The translate() function takes up to three parameters:

• The context - usually the class name for the tr() caller.
• The source text - usually the argument to tr().
• The disambiguation - an optional string that helps disambiguate different uses of the same text in the same context.

For example, the "Cancel" in a dialog might have "Anuluj" when the program runs in Polish (in this case the source text would be "Cancel"). The context would (normally) be the dialog's class name; there would normally be no comment, and the translated text would be "Anuluj".

But it's not always so simple. The Spanish version of a printer dialog with settings for two-sided printing and binding would probably require both "Activado" and "Activada" as translations for "Enabled". In this case the source text would be "Enabled" in both cases, and the context would be the dialog's class name, but the two items would have disambiguations such as "two-sided printing" for one and "binding" for the other. The disambiguation enables the translator to choose the appropriate gender for the Spanish version, and enables Qt to distinguish between translations.

Using Multiple Translations

Multiple translation files can be installed in an application. Translations are searched for in the reverse order in which they were installed, so the most recently installed translation file is searched for translations first and the earliest translation file is searched last. The search stops as soon as a translation containing a matching string is found.

This mechanism makes it possible for a specific translation to be "selected" or given priority over the others; simply uninstall the translator from the application by passing it to the QCoreApplication::removeTranslator() function and reinstall it with QCoreApplication::installTranslator(). It will then be the first translation to be searched for matching strings.