Correct way to load .qm files in QTranslator

[therealmatiss]

Hello!

I am adding translation layer to my Qt6/QML application and I'm having issues loading my .em file.

I am following the QML documentation, which is lacking for Localization, to say the least. The closest thing I found for me as I only need to use .qml file localization is (https://doc.qt.io/qt-6/qtlinguist-arrowpad-example.html) and (https://doc.qt.io/qt-6/qtqml-qml-i18n-example.html)

Things I've done:

1. Include LinguistsTools in CMake (Works)
2. Added this to my CMakeLists.txt (It builds the .em file in my build folder)

qt6_add_translations(${CMAKE_PROJECT_NAME}
  TS_FILES qml/translations/EN_en.ts
)

3. Added this to my main.cpp (Doesn't work!)

  QTranslator translator;
  QString translationPath = app.applicationDirPath() + "/EN_en.qm";
  if (translator.load(translationPath)) {
    app.installTranslator(&translator);
    SPDLOG_INFO("Translator loaded");
  } else {
    SPDLOG_ERROR("Failed to load translator");
  }

This command translator.load(translationPath) returns false.

I'm pretty sure my path is wrong here - how can I add correct .em file path? I don't want to hardcode it, I want to be relative - how can I get the build folder via QApplication object? Or maybe is it better to define it in QRC file and use qrc:/translations/EN_en.qm or something like that? If so, then is it a good idea to add build folder files in QRC - isn't that against the standard? In the future I will want to add translations to other languages as well so I want to get the .em file saving right.

This is my EN_en.ts file:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE TS>
<TS version="2.1" language="en">
    <context>
        <name>Test</name>
        <message>
            <source>Hello World</source>
            <translation>Hello World EN</translation>
        </message>
        <message>
            <source>Goodbye</source>
            <translation>Goodbye EN</translation>
        </message>
    </context>
</TS>

In QML I am testing like this - it should be Hello World EN when I get it working.

text: qsTr("Hello World")

[kkoehne]

@therealmatiss , try

if  (translator.load(":/translations/EN_en.qm")) {

[Christian Ehrlicher]

@therealmatiss said in Correct way to load .qm files in QTranslator:

QTranslator translator

How long does this object live?

[therealmatiss]

@Christian-Ehrlicher Until the end of program. It's not a problem about QTranslator - it's a problem about loading the .em file.

There is nothing in documentation about the pathing of .qm files - where they are generated, where they should be located preferably, how they should be preferably loaded. Most of the tutorials are based from pre-Qt6 time with .pro files. For example, this (https://doc.qt.io/qt-6/qtqml-qml-i18n-example.html) is unfinished - it doesn't even show QTranslator object creation, let alone loading the .qm files.

I just want an example on how to add .ts files to QML in Qt6 using CMake - I am not using the device locale.

EDIT: I figured that I add that translator.load(translationPath) returns false. Must be my translationPath issue.

[Christian Ehrlicher]

@therealmatiss said in Correct way to load .qm files in QTranslator:

Until the end of program.

Not if your snippet you showed us is in a function.

The cmake macro adds the qm file to the resource file so your path is wrong: https://doc.qt.io/qt-6/qtlinguist-cmake-qt-add-translations.html#embedding-generated-qm-files-in-resources

[therealmatiss]

@Christian-Ehrlicher Yes, it's in int main(), same as the QApplication. Ok, thanks for showing that it adds it to resource file automatically. Unfortunately it still doesn't work. Now I have this setup:

CMakeLists.txt

qt6_add_translations(${CMAKE_PROJECT_NAME}
  TS_FILES qml/translations/EN_en.ts
  RESOURCE_PREFIX "/translations"
)

main.cpp [int main()] - translator.load("qrc:/translations/EN_en") still returns false :(

...
QTranslator translator;
  if (translator.load("qrc:/translations/EN_en")) {
    app.installTranslator(&translator);
    SPDLOG_INFO("Translator loaded");
  } else {
    SPDLOG_ERROR("Failed to load translator");
  }
...

[kkoehne]

@therealmatiss , try

if  (translator.load(":/translations/EN_en.qm")) {

[therealmatiss]

@kkoehne Sorry for the late response but thank you! It now loads correctly.

Is it that QResources, which are not defined in .qrc file, are accessible by : instead of qrc:? I have only been using resources via qrc file so I haven't experienced this before. I suggest to add here (https://doc.qt.io/qt-6/qtlinguist-cmake-qt-add-translations.html#embedding-generated-qm-files-in-resources) an example on how to load correct auto-added .qm resource path, after generating .qm file.

There are a few more things I would like to add - please, provide a .ts file example in the documents (there's one that only explains all parameters but doesn't show an example)

[kkoehne]

@therealmatiss said in Correct way to load .qm files in QTranslator:

Is it that QResources, which are not defined in .qrc file, are accessible by : instead of qrc:?

No, it's simpler: qrc:/ is a URL, :/ is a (special) file path. API's expecting a file path (QString) only acknowledge :/, while API's expecting a URL (QUrl) only acknowledge qrc:/. Traditional API's in Qt Core typically expect QString, while QML slowly moved towards QUrl for network transparency, so it became rather confusing :/

[therealmatiss]

@kkoehne Thank you for the explanation!