Make sure we load translations on the main thread.

BUG: 346188
REVIEW: 123726

1 files changed, 63 insertions, 27 deletions

diff --git a/modules/ECMQmLoader.cpp.in b/modules/ECMQmLoader.cpp.in
index bc01bf98..f6b98e7b 100644
--- a/modules/ECMQmLoader.cpp.in
+++ b/modules/ECMQmLoader.cpp.in
@@ -5,41 +5,77 @@
  */
 #include <QCoreApplication>
 #include <QLocale>
+#include <QMetaObject>
 #include <QStandardPaths>
+#include <QThread>
 #include <QTranslator>
 
-#include <QDebug>
+namespace {
 
-static bool loadTranslation(const QString &localeDirName)
-{
-    QString subPath = QStringLiteral("locale/") + localeDirName + QStringLiteral("/LC_MESSAGES/@catalog_name@.qm");
-    QString fullPath = QStandardPaths::locate(QStandardPaths::GenericDataLocation, subPath);
-    if (fullPath.isEmpty()) {
-        return false;
+    bool loadTranslation(const QString &localeDirName)
+    {
+        QString subPath = QStringLiteral("locale/") + localeDirName + QStringLiteral("/LC_MESSAGES/@catalog_name@.qm");
+        QString fullPath = QStandardPaths::locate(QStandardPaths::GenericDataLocation, subPath);
+        if (fullPath.isEmpty()) {
+            return false;
+        }
+        QTranslator *translator = new QTranslator(QCoreApplication::instance());
+        if (!translator->load(fullPath)) {
+            delete translator;
+            return false;
+        }
+        QCoreApplication::instance()->installTranslator(translator);
+        return true;
     }
-    QTranslator *translator = new QTranslator(QCoreApplication::instance());
-    if (!translator->load(fullPath)) {
-        delete translator;
-        return false;
+
+    void load()
+    {
+        // The way Qt translation system handles plural forms makes it necessary to
+        // have a translation file which contains only plural forms for `en`. That's
+        // why we load the `en` translation unconditionally, then load the
+        // translation for the current locale to overload it.
+        loadTranslation(QStringLiteral("en"));
+
+        QLocale locale = QLocale::system();
+        if (locale.name() != QStringLiteral("en")) {
+            if (!loadTranslation(locale.name())) {
+                loadTranslation(locale.bcp47Name());
+            }
+        }
     }
-    QCoreApplication::instance()->installTranslator(translator);
-    return true;
-}
 
-static void load()
-{
-    // The way Qt translation system handles plural forms makes it necessary to
-    // have a translation file which contains only plural forms for `en`. That's
-    // why we load the `en` translation unconditionally, then load the
-    // translation for the current locale to overload it.
-    loadTranslation(QStringLiteral("en"));
-
-    QLocale locale = QLocale::system();
-    if (locale.name() != QStringLiteral("en")) {
-        if (!loadTranslation(locale.name())) {
-            loadTranslation(locale.bcp47Name());
+    // helper to call load() on the correct thread
+    class Loader : public QObject
+    {
+        Q_OBJECT
+
+    public Q_SLOTS:
+        void callLoadAndDeleteSelf()
+        {
+            load();
+            this->deleteLater();
+        }
+    };
+
+    void loadOnMainThread()
+    {
+        // If this library is loaded after the QCoreApplication instance is created
+        // (eg: because it is brought in by a plugin), there is no guarantee this
+        // function will be called on the main thread.
+        // QCoreApplication::installTranslator needs to be called on the main
+        // thread, because it uses QCoreApplication::sendEvent.
+        if (QThread::currentThread() == QCoreApplication::instance()->thread()) {
+            load();
+        } else {
+            // QObjects inherit their parent object's thread
+            Loader *loader = new Loader();
+            loader->moveToThread(QCoreApplication::instance()->thread());
+            QMetaObject::invokeMethod(loader, "callLoadAndDeleteSelf", Qt::AutoConnection);
         }
     }
+
 }
 
-Q_COREAPP_STARTUP_FUNCTION(load)
+Q_COREAPP_STARTUP_FUNCTION(loadOnMainThread)
+
+#include "ECMQmLoader.moc"