[libcalamares] Refactor translation-setting

- Split the actual loading of translations into classes
   to encapsulate the loading logic,
 - Build a collection of classes to do the different kinds
   of translation loading,
 - Build a generic function to load something and update a
   static pointer to the translation.

This makes installTranslator() much easier to read, and encapsulates
the type-specific loading somewhere else. While here, add a timezone-
translations loader so that the split-out TZ translations also work.

src/libcalamares/utils/Retranslator.cpp

@@ -25,16 +25,15 @@
 #include <QEvent>
 #include <QTranslator>
 
-
-namespace CalamaresUtils
-{
-static QTranslator* s_brandingTranslator = nullptr;
-static QTranslator* s_translator = nullptr;
-static QString s_translatorLocaleName;
-
-void
-installTranslator( const QLocale& locale, const QString& brandingTranslationsPrefix, QObject* parent )
+/** @brief Helper class for loading translations
+ *
+ * This is used by the loadSingletonTranslator() function to hand off
+ * work to translation-type specific code.
+ */
+struct TranslationLoader
 {
+    static QString mungeLocaleName( const QLocale& locale )
+    {
         QString localeName = locale.name();
         localeName.replace( "-", "_" );
 
@@ -50,65 +49,132 @@ installTranslator( const QLocale& locale, const QString& brandingTranslationsPre
         {
             localeName = QStringLiteral( "sr@latin" );
         }
+        return localeName;
+    }
+
+    TranslationLoader( const QLocale& locale )
+        : m_locale( locale )
+        , m_localeName( mungeLocaleName( locale ) )
+    {
+    }
+
+    virtual ~TranslationLoader() {};
+    /// @brief Loads @p translator with the specific translations of this type
+    virtual bool tryLoad( QTranslator* translator ) = 0;
 
-    cDebug() << "Looking for translations for" << localeName;
+    const QLocale& m_locale;
+    QString m_localeName;
+};
 
-    QTranslator* translator = nullptr;
+struct BrandingLoader : public TranslationLoader
+{
+    BrandingLoader( const QLocale& locale, const QString& prefix )
+        : TranslationLoader( locale )
+        , m_prefix( prefix )
+    {
+    }
 
-    // Branding translations
-    if ( !brandingTranslationsPrefix.isEmpty() )
+    bool tryLoad( QTranslator* translator ) override
+    {
+        if ( m_prefix.isEmpty() )
         {
-        QString brandingTranslationsDirPath( brandingTranslationsPrefix );
-        brandingTranslationsDirPath.truncate( brandingTranslationsPrefix.lastIndexOf( QDir::separator() ) );
+            return false;
+        }
+        QString brandingTranslationsDirPath( m_prefix );
+        brandingTranslationsDirPath.truncate( m_prefix.lastIndexOf( QDir::separator() ) );
         QDir brandingTranslationsDir( brandingTranslationsDirPath );
         if ( brandingTranslationsDir.exists() )
         {
-            QString filenameBase( brandingTranslationsPrefix );
-            filenameBase.remove( 0, brandingTranslationsPrefix.lastIndexOf( QDir::separator() ) + 1 );
-            translator = new QTranslator( parent );
-            if ( translator->load( locale, filenameBase, "_", brandingTranslationsDir.absolutePath() ) )
+            QString filenameBase( m_prefix );
+            filenameBase.remove( 0, m_prefix.lastIndexOf( QDir::separator() ) + 1 );
+            if ( translator->load( m_locale, filenameBase, "_", brandingTranslationsDir.absolutePath() ) )
             {
-                cDebug() << Logger::SubEntry << "Branding using locale:" << localeName;
+                cDebug() << Logger::SubEntry << "Branding using locale:" << m_localeName;
+                return true;
             }
             else
             {
-                cDebug() << Logger::SubEntry << "Branding using default, system locale not found:" << localeName;
-                translator->load( brandingTranslationsPrefix + "en" );
+                cDebug() << Logger::SubEntry << "Branding using default, system locale not found:" << m_localeName;
+                // TODO: this loads something completely different
+                return translator->load( m_prefix + "en" );
+            }
+        }
+        return false;
     }
 
-            if ( s_brandingTranslator )
+    QString m_prefix;
+};
+
+struct CalamaresLoader : public TranslationLoader
+{
+    using TranslationLoader::TranslationLoader;
+
+    bool tryLoad( QTranslator* translator ) override
     {
-                QCoreApplication::removeTranslator( s_brandingTranslator );
-                delete s_brandingTranslator;
+        if ( translator->load( QString( ":/lang/calamares_" ) + m_localeName ) )
+        {
+            cDebug() << Logger::SubEntry << "Calamares using locale:" << m_localeName;
+            return true;
         }
-
-            QCoreApplication::installTranslator( translator );
-            s_brandingTranslator = translator;
+        else
+        {
+            cDebug() << Logger::SubEntry << "Calamares using default, system locale not found:" << m_localeName;
+            return translator->load( QString( ":/lang/calamares_en" ) );
         }
     }
+};
 
-    // Calamares translations
-    translator = new QTranslator( parent );
-    if ( translator->load( QString( ":/lang/calamares_" ) + localeName ) )
+struct TZLoader : public TranslationLoader
+{
+    using TranslationLoader::TranslationLoader;
+    bool tryLoad( QTranslator* translator ) override
     {
-        cDebug() << Logger::SubEntry << "Calamares using locale:" << localeName;
+        if ( translator->load( QString( ":/lang/tz_" ) + m_localeName ) )
+        {
+            cDebug() << Logger::SubEntry << "Calamares Timezones using locale:" << m_localeName;
+            return true;
         }
         else
         {
-        cDebug() << Logger::SubEntry << "Calamares using default, system locale not found:" << localeName;
-        translator->load( QString( ":/lang/calamares_en" ) );
+            cDebug() << Logger::SubEntry
+                     << "Calamares Timezones using default, system locale not found:" << m_localeName;
+            return translator->load( QString( ":/lang/tz_en" ) );
+        }
     }
+};
+
+static void
+loadSingletonTranslator( TranslationLoader&& loader, QTranslator*& translator_p )
+{
+    QTranslator* translator = new QTranslator();
+    loader.tryLoad( translator );
 
-    if ( s_translator )
+    if ( translator_p )
     {
-        QCoreApplication::removeTranslator( s_translator );
-        delete s_translator;
+        QCoreApplication::removeTranslator( translator_p );
+        delete translator_p;
     }
 
     QCoreApplication::installTranslator( translator );
-    s_translator = translator;
+    translator_p = translator;
+}
+
+namespace CalamaresUtils
+{
+static QTranslator* s_brandingTranslator = nullptr;
+static QTranslator* s_translator = nullptr;
+static QTranslator* s_tztranslator = nullptr;
+static QString s_translatorLocaleName;
+
+void
+installTranslator( const QLocale& locale, const QString& brandingTranslationsPrefix, QObject* parent )
+{
+    loadSingletonTranslator( BrandingLoader( locale, brandingTranslationsPrefix ), s_brandingTranslator );
+    loadSingletonTranslator( TZLoader( locale ), s_tztranslator );
 
-    s_translatorLocaleName = localeName;
+    CalamaresLoader l( locale );  // because we want the extracted localeName
+    loadSingletonTranslator( std::move( l ), s_translator );
+    s_translatorLocaleName = l.m_localeName;
 }