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>

1 files changed, 23 insertions, 0 deletions

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 {};