store language file paths relatively

dialogs/advancedvideodialog.h

@@ -14,7 +14,8 @@ public:
                         int encoding_codec,
                         VideoCodecParams& iparams);
 
-    void accept();
+public slots:
+    virtual void accept() override;
 private:
     VideoCodecParams& params;
 

dialogs/preferencesdialog.cpp

@@ -392,11 +392,14 @@ void PreferencesDialog::setup_ui() {
 		if (translation_dir.exists()) {
 			QStringList translation_files = translation_dir.entryList({"*.qm"}, QDir::Files | QDir::NoDotAndDotDot);
 			for (int i=0;i<translation_files.size();i++) {
+                // get path of translation relative to the application path
 				QString locale_full_path = translation_dir.filePath(translation_files.at(i));
+                QString locale_relative_path = QDir(get_app_dir()).relativeFilePath(locale_full_path);
+
 				QFileInfo locale_file(translation_files.at(i));
 				QString locale_file_basename = locale_file.baseName();
 				QString locale_str = locale_file_basename.mid(locale_file_basename.lastIndexOf('_')+1);
-				language_combobox->addItem(QLocale(locale_str).nativeLanguageName(), locale_full_path);
+                language_combobox->addItem(QLocale(locale_str).nativeLanguageName(), locale_relative_path);
 
 				if (config.language_file == locale_full_path) {
 					language_combobox->setCurrentIndex(language_combobox->count() - 1);

mainwindow.cpp

@@ -207,11 +207,18 @@ MainWindow::MainWindow(QWidget *parent, const QString &an) :
 				config.language_file :
 				runtime_config.external_translation_file;
 
-	if (!language_file.isEmpty()
-			&& QFileInfo::exists(language_file)) {
-		QTranslator* translator = new QTranslator(this);
-		translator->load(language_file);
-		QApplication::installTranslator(translator);
+    if (!language_file.isEmpty()) {
+
+        // translation files are stored relative to app path (see GitHub issue #454)
+        QString full_language_path = QDir(get_app_dir()).filePath(language_file);
+
+        if (QFileInfo::exists(full_language_path)) {
+            QTranslator* translator = new QTranslator(this);
+            translator->load(full_language_path);
+            QApplication::installTranslator(translator);
+        } else {
+            qWarning() << "Failed to load translation file" << full_language_path << ". No language will be loaded.";
+        }
 	}
 
 	alloc_panels(this);