Can't install translations in application

[Arc676]

The API doesn't include a wrapper for QTranslator and since struct QmlEngineHolderis hidden within the crate and QmlEngineHolder::app is not visible to external code, there is no way to load translations via QCoreApplication::installTranslator, even from within an unsafe cpp! block.

Is there another way to load translations without CMake? The end goal is to be able to use i18n.tr in the QML frontend (and possibly the backend, though the frontend is currently the priority for me personally) and load translations based on the user's locale.

[ogoffart]

An API to use the translator would be a nice addition.

But in the mean time, QCoreApplication::installTranslator is a static member and can then be called from a cpp! block.
Even if it wasn't, there is also the qApp macro in Qt that allow to get the application without the need to expose it from whatever created it.

As for the build system, i don't know, but you probably can call lrelease from the build.rs

[Arc676]

Thanks for the tip; I didn't realize you didn't need the instance of the application from the QML engine. Seems like it can successfully load the translations but they aren't appearing on the interface. I don't currently know the reason though; I'll have to look into it further.

Update: Based on the following main function, it seems the translations don't continue to exist outside of the cpp! block in which they are loaded. Although it correctly prints the translated string immediately after loading, the interface is still in English and the second print statement in a new block also doesn't print the translated string.

Update 2: The translations become permanent in the backend by allocating the translator on the heap (I guess I should've thought of this) but the QML frontend still can't get the translated strings via qsTr or i18n.tr.

fn main() {
        unsafe {
                cpp! { {
                        #include <QtCore/QCoreApplication>
                        #include <QtCore/QString>
                        #include <QtCore/QTranslator>
                        #include <QtCore/QDebug>
                }}
                cpp!{[]{
                        QCoreApplication::setApplicationName(QStringLiteral("app.namespace"));
                }}
        }
        qrc::load();
        // qml_register_type::...
        let mut engine = QmlEngine::new();
        unsafe {
                cpp!{[]{
                        QTranslator* translator = new QTranslator();
                        bool isLoaded = translator->load("de", "po");
                        qDebug() << isLoaded;
                        QCoreApplication::installTranslator(translator);
                        qDebug() << QCoreApplication::translate("", "Cancel"); // prints the correct translation
                }}
        }
        engine.load_file("qrc:/qml/Main.qml".into());
        unsafe {
                cpp!{[]{
                        qDebug() << QCoreApplication::translate("", "Cancel"); // prints the correct translation
                }}
        }
        engine.exec();
}

[ogoffart]

The translations become permanent in the backend by allocating the translator on the heap

you can give the qApp as a parent, that way it is not going to leak on exit.

but the QML frontend still can't get the translated strings via qsTr or i18n.tr

You may need to load the right .qm files.
So that mean running lupdate and lrelease to create them. and make sure they can be found.
(the qrc! maco may be of use if you want to load them in the ressources)

[Arc676]

I was under the impression that loading the translation files via QTranslator::load was enough to load the translations. Is there something else I need on the QML side? I created the translation template (.pot) using xgettext, added some strings, converted to .ts and compiled with lrelease. I tried also adding the .qm file to the resource list in the qrc! macro but it didn't help.

[Arc676]

For the record (and for future visitors of this thread) someone else has already figured out how to generate the translation templates and copy them to the required directory as part of the build process. The repository is here. The relevant files are src/build.rs and src/main.rs.