Add Qt.uiLanguage and QJSEngine::uiLanguage properties

[ChangeLog][QtQml] Added Qt.uiLanguage and QJSEngine::uiLanguage properties

These properties mirror the same value in QML and C++ and can be used
freely. They also provide API symmetry to Qt for MCUs.
QQmlApplicationEngine binds to this property and applies translations
accordingly by constructing a QLocale with the value and using
QTranslator::load(locale).

Change-Id: Id87d6ee64679b07ff3cb47844594e8eeebd8c8b6
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Christian Kamm <mail@ckamm.de>

16 files changed, 236 insertions, 20 deletions

diff --git a/src/qml/jsapi/qjsengine.cpp b/src/qml/jsapi/qjsengine.cpp
index 065fbc1c0a..6946a64d11 100644
--- a/src/qml/jsapi/qjsengine.cpp
+++ b/src/qml/jsapi/qjsengine.cpp
@@ -71,11 +71,6 @@
 #include <private/qqmlglobal_p.h>
 #include <qqmlengine.h>
 
-#undef Q_D
-#undef Q_Q
-#define Q_D(blah)
-#define Q_Q(blah)
-
 Q_DECLARE_METATYPE(QList<int>)
 
 /*!
@@ -257,7 +252,7 @@ Q_DECLARE_METATYPE(QList<int>)
     \l installExtensions().
 
     \value TranslationExtension Indicates that translation functions (\c qsTr(),
-        for example) should be installed.
+        for example) should be installed. This also installs the Qt.uiLanguage property.
 
     \value ConsoleExtension Indicates that console functions (\c console.log(),
         for example) should be installed.
@@ -692,7 +687,6 @@ QJSValue QJSEngine::newArray(uint length)
 */
 QJSValue QJSEngine::newQObject(QObject *object)
 {
-    Q_D(QJSEngine);
     QV4::ExecutionEngine *v4 = m_v4Engine;
     QV4::Scope scope(v4);
     if (object) {
@@ -719,7 +713,6 @@ QJSValue QJSEngine::newQObject(QObject *object)
 */
 
 QJSValue QJSEngine::newQMetaObject(const QMetaObject* metaObject) {
-    Q_D(QJSEngine);
     QV4::ExecutionEngine *v4 = m_v4Engine;
     QV4::Scope scope(v4);
     QV4::ScopedValue v(scope, QV4::QMetaObjectWrapper::create(v4, metaObject));
@@ -1004,6 +997,35 @@ void QJSEngine::throwError(QJSValue::ErrorType errorType, const QString &message
     m_v4Engine->throwError(e);
 }
 
+/*!
+  \property QJSEngine::uiLanguage
+  \brief the language to be used for translating user interface strings
+  \since 5.15
+
+  This property holds the name of the language to be used for user interface
+  string translations. It is exposed for reading and writing as \c{Qt.uiLanguage} when
+  the QJSEngine::TranslationExtension is installed on the engine. It is always exposed
+  in instances of QQmlEngine.
+
+  You can set the value freely and use it in bindings. It is recommended to set it
+  after installing translators in your application. By convention, an empty string
+  means no translation from the language used in the source code is intended to occur.
+*/
+void QJSEngine::setUiLanguage(const QString &language)
+{
+    Q_D(QJSEngine);
+    if (language == d->uiLanguage)
+        return;
+    d->uiLanguage = language;
+    emit uiLanguageChanged();
+}
+
+QString QJSEngine::uiLanguage() const
+{
+    Q_D(const QJSEngine);
+    return d->uiLanguage;
+}
+
 QJSEnginePrivate *QJSEnginePrivate::get(QV4::ExecutionEngine *e)
 {
     return e->jsEngine()->d_func();
diff --git a/src/qml/jsapi/qjsengine.h b/src/qml/jsapi/qjsengine.h
index 31a4d68baa..31229e1f20 100644
--- a/src/qml/jsapi/qjsengine.h
+++ b/src/qml/jsapi/qjsengine.h
@@ -60,6 +60,7 @@ class Q_QML_EXPORT QJSEngine
     : public QObject
 {
     Q_OBJECT
+    Q_PROPERTY(QString uiLanguage READ uiLanguage WRITE setUiLanguage NOTIFY uiLanguageChanged)
 public:
     QJSEngine();
     explicit QJSEngine(QObject *parent);
@@ -121,6 +122,12 @@ public:
     void throwError(const QString &message);
     void throwError(QJSValue::ErrorType errorType, const QString &message = QString());
 
+    QString uiLanguage() const;
+    void setUiLanguage(const QString &language);
+
+Q_SIGNALS:
+    void uiLanguageChanged();
+
 private:
     QJSValue create(int type, const void *ptr);
 
diff --git a/src/qml/jsapi/qjsengine_p.h b/src/qml/jsapi/qjsengine_p.h
index 164a70d000..7866a5bdda 100644
--- a/src/qml/jsapi/qjsengine_p.h
+++ b/src/qml/jsapi/qjsengine_p.h
@@ -107,6 +107,7 @@ public:
     // Shared by QQmlEngine
     mutable QRecursiveMutex mutex;
 
+    QString uiLanguage;
 
     // These methods may be called from the QML loader thread
     inline QQmlPropertyCache *cache(QObject *obj, int minorVersion = -1);
diff --git a/src/qml/jsruntime/qv4engine.cpp b/src/qml/jsruntime/qv4engine.cpp
index dcdebfb398..86e178d568 100644
--- a/src/qml/jsruntime/qv4engine.cpp
+++ b/src/qml/jsruntime/qv4engine.cpp
@@ -1949,11 +1949,12 @@ void ExecutionEngine::initQmlGlobalObject()
 void ExecutionEngine::initializeGlobal()
 {
     QV4::Scope scope(this);
-    QV4::GlobalExtensions::init(globalObject, QJSEngine::AllExtensions);
 
     QV4::ScopedObject qt(scope, memoryManager->allocate<QV4::QtObject>(qmlEngine()));
     globalObject->defineDefaultProperty(QStringLiteral("Qt"), qt);
 
+    QV4::GlobalExtensions::init(globalObject, QJSEngine::AllExtensions);
+
 #if QT_CONFIG(qml_locale)
     QQmlLocale::registerStringLocaleCompare(this);
     QQmlDateExtension::registerExtension(this);
diff --git a/src/qml/qml/qqmlapplicationengine.cpp b/src/qml/qml/qqmlapplicationengine.cpp
index 7f80fe5e1c..7d961cd0c7 100644
--- a/src/qml/qml/qqmlapplicationengine.cpp
+++ b/src/qml/qml/qqmlapplicationengine.cpp
@@ -50,6 +50,7 @@ QT_BEGIN_NAMESPACE
 QQmlApplicationEnginePrivate::QQmlApplicationEnginePrivate(QQmlEngine *e)
     : QQmlEnginePrivate(e)
 {
+    uiLanguage = QLocale().bcp47Name();
 }
 
 QQmlApplicationEnginePrivate::~QQmlApplicationEnginePrivate()
@@ -72,6 +73,7 @@ void QQmlApplicationEnginePrivate::init()
                &QCoreApplication::quit, Qt::QueuedConnection);
     q->connect(q, &QQmlApplicationEngine::exit, QCoreApplication::instance(),
                &QCoreApplication::exit, Qt::QueuedConnection);
+    q->connect(q, SIGNAL(uiLanguageChanged()), q_func(), SLOT(_q_loadTranslations()));
 #if QT_CONFIG(translation)
     QTranslator* qtTranslator = new QTranslator(q);
     if (qtTranslator->load(QLocale(), QLatin1String("qt"), QLatin1String("_"), QLibraryInfo::location(QLibraryInfo::TranslationsPath), QLatin1String(".qm")))
@@ -83,20 +85,27 @@ void QQmlApplicationEnginePrivate::init()
     QCoreApplication::instance()->setProperty("__qml_using_qqmlapplicationengine", QVariant(true));
 }
 
-void QQmlApplicationEnginePrivate::loadTranslations(const QUrl &rootFile)
+void QQmlApplicationEnginePrivate::_q_loadTranslations()
 {
 #if QT_CONFIG(translation)
-    if (rootFile.scheme() != QLatin1String("file") && rootFile.scheme() != QLatin1String("qrc"))
+    if (translationsDirectory.isEmpty())
         return;
 
-    QFileInfo fi(QQmlFile::urlToLocalFileOrQrc(rootFile));
-
     Q_Q(QQmlApplicationEngine);
-    QTranslator *translator = new QTranslator(q);
-    if (translator->load(QLocale(), QLatin1String("qml"), QLatin1String("_"), fi.path() + QLatin1String("/i18n"), QLatin1String(".qm")))
-        QCoreApplication::installTranslator(translator);
-    else
-        delete translator;
+
+    QScopedPointer<QTranslator> translator(new QTranslator);
+    if (!uiLanguage.isEmpty()) {
+        QLocale locale(uiLanguage);
+        if (translator->load(locale, QLatin1String("qml"), QLatin1String("_"), translationsDirectory, QLatin1String(".qm"))) {
+            if (activeTranslator)
+                QCoreApplication::removeTranslator(activeTranslator.data());
+            QCoreApplication::installTranslator(translator.data());
+            activeTranslator.swap(translator);
+        }
+    } else {
+        activeTranslator.reset();
+    }
+    q->retranslate();
 #else
     Q_UNUSED(rootFile)
 #endif
@@ -106,7 +115,14 @@ void QQmlApplicationEnginePrivate::startLoad(const QUrl &url, const QByteArray &
 {
     Q_Q(QQmlApplicationEngine);
 
-    loadTranslations(url); //Translations must be loaded before the QML file is
+    if (url.scheme() == QLatin1String("file") || url.scheme() == QLatin1String("qrc")) {
+        QFileInfo fi(QQmlFile::urlToLocalFileOrQrc(url));
+        translationsDirectory = fi.path() + QLatin1String("/i18n");
+    } else {
+        translationsDirectory.clear();
+    }
+
+    _q_loadTranslations(); //Translations must be loaded before the QML file is
     QQmlComponent *c = new QQmlComponent(q, q);
 
     if (dataFlag)
@@ -181,6 +197,7 @@ void QQmlApplicationEnginePrivate::finishLoad(QQmlComponent *c)
       \list
           \li Translation files must have "qml_" prefix e.g. qml_ja_JP.qm.
       \endlist
+  \li Translations are reloaded when the \c QJSEngine::uiLanguage / \c Qt.uiLanguage property is changed.
   \li Automatically sets an incubation controller if the scene contains a QQuickWindow.
   \li Automatically sets a \c QQmlFileSelector as the url interceptor, applying file selectors to all
   QML files and assets.
diff --git a/src/qml/qml/qqmlapplicationengine.h b/src/qml/qml/qqmlapplicationengine.h
index 2b4de91154..37f75d5068 100644
--- a/src/qml/qml/qqmlapplicationengine.h
+++ b/src/qml/qml/qqmlapplicationengine.h
@@ -74,6 +74,7 @@ Q_SIGNALS:
 
 private:
     Q_DISABLE_COPY(QQmlApplicationEngine)
+    Q_PRIVATE_SLOT(d_func(), void _q_loadTranslations())
     Q_DECLARE_PRIVATE(QQmlApplicationEngine)
 };
 
diff --git a/src/qml/qml/qqmlapplicationengine_p.h b/src/qml/qml/qqmlapplicationengine_p.h
index 1279e400e8..c514e3daf9 100644
--- a/src/qml/qml/qqmlapplicationengine_p.h
+++ b/src/qml/qml/qqmlapplicationengine_p.h
@@ -70,10 +70,12 @@ public:
     void cleanUp();
 
     void startLoad(const QUrl &url, const QByteArray &data = QByteArray(), bool dataFlag = false);
-    void loadTranslations(const QUrl &rootFile);
+    void _q_loadTranslations();
     void finishLoad(QQmlComponent *component);
     QList<QObject *> objects;
     QVariantMap initialProperties;
+    QString translationsDirectory;
+    QScopedPointer<QTranslator> activeTranslator;
 };
 
 QT_END_NAMESPACE
diff --git a/src/qml/qml/qqmlengine.cpp b/src/qml/qml/qqmlengine.cpp
index 73d3ba1863..3345fcb19e 100644
--- a/src/qml/qml/qqmlengine.cpp
+++ b/src/qml/qml/qqmlengine.cpp
@@ -1336,6 +1336,21 @@ void QQmlEngine::setOutputWarningsToStandardError(bool enabled)
 }
 
 /*!
+  \qmlproperty string Qt::uiLanguage
+  \since 5.15
+
+  The uiLanguage holds the name of the language to be used for user interface
+  string translations. It is exposed in C++ as QQmlEngine::uiLanguage property.
+
+  You can set the value freely and use it in bindings. It is recommended to set it
+  after installing translators in your application. By convention, an empty string
+  means no translation from the language used in the source code is intended to occur.
+
+  If you're using QQmlApplicationEngine and the value changes, QQmlEngine::retranslate()
+  will be called.
+*/
+
+/*!
   \fn template<typename T> T QQmlEngine::singletonInstance(int qmlTypeId)
 
   Returns the instance of a singleton type that was registered under \a qmlTypeId.
diff --git a/src/qml/qml/v8/qqmlbuiltinfunctions.cpp b/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
index ac4b9b85b9..b1046b254b 100644
--- a/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
+++ b/src/qml/qml/v8/qqmlbuiltinfunctions.cpp
@@ -1338,6 +1338,41 @@ ReturnedValue QtObject::method_createComponent(const FunctionObject *b, const Va
     return QV4::QObjectWrapper::wrap(scope.engine, c);
 }
 
+ReturnedValue QtObject::method_get_uiLanguage(const FunctionObject *b, const Value * /*thisObject*/, const Value * /*argv*/, int /*argc*/)
+{
+    QV4::Scope scope(b);
+    QJSEngine *jsEngine = scope.engine->jsEngine();
+    if (!jsEngine)
+        return Encode::null();
+
+    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(scope.engine);
+    if (ep && ep->propertyCapture) {
+        static int propertyIndex = -1;
+        static int notifySignalIndex = -1;
+        if (propertyIndex < 0) {
+            QMetaProperty metaProperty =
+                    QQmlEngine::staticMetaObject.property(QQmlEngine::staticMetaObject.indexOfProperty("uiLanguage"));
+            propertyIndex = metaProperty.propertyIndex();
+            notifySignalIndex = metaProperty.notifySignalIndex();
+        }
+        ep->propertyCapture->captureProperty(QQmlEnginePrivate::get(ep), propertyIndex, notifySignalIndex);
+    }
+
+    return Encode(scope.engine->newString(QJSEnginePrivate::get(jsEngine)->uiLanguage));
+}
+
+ReturnedValue QtObject::method_set_uiLanguage(const FunctionObject *b, const Value * /*thisObject*/, const Value *argv, int argc)
+{
+    Scope scope(b);
+    if (!argc)
+        THROW_TYPE_ERROR();
+    QJSEngine *jsEngine = scope.engine->jsEngine();
+    if (!jsEngine)
+        THROW_TYPE_ERROR();
+    jsEngine->setUiLanguage(argv[0].toQString());
+    return Encode::undefined();
+}
+
 #if QT_CONFIG(qml_locale)
 /*!
     \qmlmethod Qt::locale(name)
@@ -1835,6 +1870,14 @@ void QV4::GlobalExtensions::init(Object *globalObject, QJSEngine::Extensions ext
         globalObject->defineDefaultProperty(QStringLiteral("qsTrId"), QV4::GlobalExtensions::method_qsTrId);
         globalObject->defineDefaultProperty(QStringLiteral("QT_TRID_NOOP"), QV4::GlobalExtensions::method_qsTrIdNoOp);
 
+        ScopedString qtName(scope, v4->newString(QStringLiteral("Qt")));
+        ScopedObject qt(scope, globalObject->get(qtName));
+        if (!qt) {
+            qt = v4->newObject();
+            globalObject->defineDefaultProperty(qtName, qt);
+        }
+        qt->defineAccessorProperty(QStringLiteral("uiLanguage"), QV4::QtObject::method_get_uiLanguage, QV4::QtObject::method_set_uiLanguage);
+
         // string prototype extension
         scope.engine->stringPrototype()->defineDefaultProperty(QStringLiteral("arg"), QV4::GlobalExtensions::method_string_arg);
     #endif
diff --git a/src/qml/qml/v8/qqmlbuiltinfunctions_p.h b/src/qml/qml/v8/qqmlbuiltinfunctions_p.h
index d87b83ba10..5cbb52471d 100644
--- a/src/qml/qml/v8/qqmlbuiltinfunctions_p.h
+++ b/src/qml/qml/v8/qqmlbuiltinfunctions_p.h
@@ -126,6 +126,8 @@ struct QtObject : Object
     static ReturnedValue method_resolvedUrl(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc);
     static ReturnedValue method_createQmlObject(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc);
     static ReturnedValue method_createComponent(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc);
+    static ReturnedValue method_get_uiLanguage(const FunctionObject *b, const Value *, const Value *, int);
+    static ReturnedValue method_set_uiLanguage(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc);
 #if QT_CONFIG(qml_locale)
     static ReturnedValue method_locale(const FunctionObject *b, const Value *thisObject, const Value *argv, int argc);
 #endif
diff --git a/tests/auto/qml/qjsengine/tst_qjsengine.cpp b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
index 28efb519ee..7b59087a72 100644
--- a/tests/auto/qml/qjsengine/tst_qjsengine.cpp
+++ b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
@@ -264,6 +264,8 @@ private slots:
     void printCircularArray();
     void typedArraySet();
 
+    void uiLanguage();
+
 public:
     Q_INVOKABLE QJSValue throwingCppMethod1();
     Q_INVOKABLE void throwingCppMethod2();
@@ -5143,6 +5145,33 @@ void tst_QJSEngine::typedArraySet()
     }
 }
 
+void tst_QJSEngine::uiLanguage()
+{
+    {
+        QJSEngine engine;
+
+        QVERIFY(!engine.globalObject().hasProperty("Qt"));
+
+        engine.installExtensions(QJSEngine::TranslationExtension);
+        QVERIFY(engine.globalObject().hasProperty("Qt"));
+        QVERIFY(engine.globalObject().property("Qt").hasProperty("uiLanguage"));
+
+        engine.setUiLanguage("Blah");
+        QCOMPARE(engine.globalObject().property("Qt").property("uiLanguage").toString(), "Blah");
+
+        engine.evaluate("Qt.uiLanguage = \"another\"");
+        QCOMPARE(engine.globalObject().property("Qt").property("uiLanguage").toString(), "another");
+    }
+
+    {
+        QQmlEngine qmlEngine;
+        QVERIFY(qmlEngine.globalObject().hasProperty("Qt"));
+        QVERIFY(qmlEngine.globalObject().property("Qt").hasProperty("uiLanguage"));
+        qmlEngine.setUiLanguage("Blah");
+        QCOMPARE(qmlEngine.globalObject().property("Qt").property("uiLanguage").toString(), "Blah");
+    }
+}
+
 QTEST_MAIN(tst_QJSEngine)
 
 #include "tst_qjsengine.moc"
diff --git a/tests/auto/qml/qqmlapplicationengine/data/i18n/qml_de_CH.qm b/tests/auto/qml/qqmlapplicationengine/data/i18n/qml_de_CH.qm
new file mode 100644
index 0000000000..926d74f905
--- /dev/null
+++ b/tests/auto/qml/qqmlapplicationengine/data/i18n/qml_de_CH.qm
diff --git a/tests/auto/qml/qqmlapplicationengine/data/i18n/qml_de_CH.ts b/tests/auto/qml/qqmlapplicationengine/data/i18n/qml_de_CH.ts
new file mode 100644
index 0000000000..2105cfb2cf
--- /dev/null
+++ b/tests/auto/qml/qqmlapplicationengine/data/i18n/qml_de_CH.ts
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE TS>
+<TS version="2.1" language="de_CH" sourcelanguage="en">
+<context>
+    <name>loadTranslation</name>
+    <message>
+        <source>translate it</source>
+        <translation>Grüezi</translation>
+    </message>
+</context>
+</TS>
diff --git a/tests/auto/qml/qqmlapplicationengine/tst_qqmlapplicationengine.cpp b/tests/auto/qml/qqmlapplicationengine/tst_qqmlapplicationengine.cpp
index 5e855efe1a..b019ff4535 100644
--- a/tests/auto/qml/qqmlapplicationengine/tst_qqmlapplicationengine.cpp
+++ b/tests/auto/qml/qqmlapplicationengine/tst_qqmlapplicationengine.cpp
@@ -53,6 +53,7 @@ private slots:
     void removeObjectsWhenDestroyed();
     void loadTranslation_data();
     void loadTranslation();
+    void translationChange();
     void setInitialProperties();
     void failureToLoadTriggersWarningSignal();
 
@@ -278,6 +279,28 @@ void tst_qqmlapplicationengine::loadTranslation()
     QCOMPARE(rootObject->property("translation").toString(), translation);
 }
 
+void tst_qqmlapplicationengine::translationChange()
+{
+    if (QLocale().language() == QLocale::SwissGerman) {
+        QSKIP("Skipping this when running under the Swiss locale as we would always load translation.");
+    }
+
+    QQmlApplicationEngine engine(testFileUrl("loadTranslation.qml"));
+
+    QCOMPARE(engine.uiLanguage(), QLocale().bcp47Name());
+
+    QObject *rootObject = engine.rootObjects().first();
+    QVERIFY(rootObject);
+
+    QCOMPARE(rootObject->property("translation").toString(), "translated");
+
+    engine.setUiLanguage("de_CH");
+    QCOMPARE(rootObject->property("translation").toString(), QString::fromUtf8("Gr\u00FCezi"));
+
+    engine.setUiLanguage(QString());
+    QCOMPARE(rootObject->property("translation").toString(), "translate it");
+}
+
 void tst_qqmlapplicationengine::setInitialProperties()
 {
     QQmlApplicationEngine test {};
diff --git a/tests/auto/qml/qqmlengine/data/uiLanguage.qml b/tests/auto/qml/qqmlengine/data/uiLanguage.qml
new file mode 100644
index 0000000000..bc20351245
--- /dev/null
+++ b/tests/auto/qml/qqmlengine/data/uiLanguage.qml
@@ -0,0 +1,9 @@
+import QtQml 2.15
+QtObject {
+    property string chosenLanguage: Qt.uiLanguage
+    property string textToTranslate: {
+        numberOfTranslationBindingEvaluations++;
+        return qsTr("Translate me maybe");
+    }
+    property int numberOfTranslationBindingEvaluations: 0
+}
diff --git a/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp b/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp
index d782df3e7f..ab4c083b65 100644
--- a/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp
+++ b/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp
@@ -84,6 +84,7 @@ private slots:
     void aggressiveGc();
     void cachedGetterLookup_qtbug_75335();
     void createComponentOnSingletonDestruction();
+    void uiLanguage();
 
 public slots:
     QObject *createAQObjectForOwnershipTest ()
@@ -1175,6 +1176,38 @@ void tst_qqmlengine::createComponentOnSingletonDestruction()
     QVERIFY(obj);
 }
 
+void tst_qqmlengine::uiLanguage()
+{
+    QQmlEngine engine;
+
+    QObject::connect(&engine, &QJSEngine::uiLanguageChanged, [&engine]() {
+        engine.retranslate();
+    });
+
+    QSignalSpy uiLanguageChangeSpy(&engine, SIGNAL(uiLanguageChanged()));
+
+    QQmlComponent component(&engine, testFileUrl("uiLanguage.qml"));
+
+    QTest::ignoreMessage(QtMsgType::QtWarningMsg, (component.url().toString() + ":2:1: QML QtObject: Binding loop detected for property \"textToTranslate\"").toLatin1());
+    QScopedPointer<QObject> object(component.create());
+    QVERIFY(!object.isNull());
+
+    QVERIFY(engine.uiLanguage().isEmpty());
+    QCOMPARE(object->property("numberOfTranslationBindingEvaluations").toInt(), 1);
+
+    QTest::ignoreMessage(QtMsgType::QtWarningMsg, (component.url().toString() + ":2:1: QML QtObject: Binding loop detected for property \"textToTranslate\"").toLatin1());
+    engine.setUiLanguage("TestLanguage");
+    QCOMPARE(object->property("numberOfTranslationBindingEvaluations").toInt(), 2);
+    QCOMPARE(object->property("chosenLanguage").toString(), "TestLanguage");
+
+
+    QTest::ignoreMessage(QtMsgType::QtWarningMsg, (component.url().toString() + ":2:1: QML QtObject: Binding loop detected for property \"textToTranslate\"").toLatin1());
+    engine.evaluate("Qt.uiLanguage = \"anotherLanguage\"");
+    QCOMPARE(engine.uiLanguage(), QString("anotherLanguage"));
+    QCOMPARE(object->property("numberOfTranslationBindingEvaluations").toInt(), 3);
+    QCOMPARE(object->property("chosenLanguage").toString(), "anotherLanguage");
+}
+
 QTEST_MAIN(tst_qqmlengine)
 
 #include "tst_qqmlengine.moc"