Feature: dynamic changes of language and locale at runtime issue #2644 (#2659)

This change updates the UI to allow for dynamic changes of language and
locale at runtime. Right now none of the language translations are finished
yet or in releasable shape so it also adds a new option to the build that
enables/disables the feature. By default no translations are currently
enabled to be built as part of a release.

Signed-off-by: Adam Treat <treat.adam@gmail.com>

gpt4all-chat/mysettings.cpp

@@ -7,6 +7,7 @@
 #include <QFile>
 #include <QFileInfo>
 #include <QGlobalStatic>
+#include <QGuiApplication>
 #include <QIODevice>
 #include <QMap>
 #include <QMetaObject>
@@ -23,6 +24,9 @@
 
 using namespace Qt::Literals::StringLiterals;
 
+// FIXME: All of these default strings that are shown in the UI for settings need to be marked as
+// translatable
+
 namespace defaults {
 
 static const int     threadCount             = std::min(4, (int32_t) std::thread::hardware_concurrency());
@@ -30,6 +34,7 @@ static const bool    forceMetal              = false;
 static const bool    networkIsActive         = false;
 static const bool    networkUsageStatsActive = false;
 static const QString device                  = "Auto";
+static const QString languageAndLocale       = "Default";
 
 } // namespace defaults
 
@@ -95,6 +100,46 @@ static QStringList getDevices(bool skipKompute = false)
     return deviceList;
 }
 
+static QString getUiLanguage(const QString directory, const QString fileName)
+{
+    QTranslator translator;
+    const QString filePath = directory + QDir::separator() + fileName;
+    if (translator.load(filePath)) {
+        const QString lang = fileName.mid(fileName.indexOf('_') + 1,
+            fileName.lastIndexOf('.') - fileName.indexOf('_') - 1);
+        return lang;
+    }
+
+    qDebug() << "ERROR: Failed to load translation file:" << filePath;
+    return QString();
+}
+
+static QStringList getUiLanguages(const QString &modelPath)
+{
+    QStringList languageList( { QObject::tr("Default") } );
+
+    // Add the language translations from model path files first which is used by translation developers
+    // to load translations in progress without having to rebuild all of GPT4All from source
+    {
+        const QDir dir(modelPath);
+        const QStringList qmFiles = dir.entryList({"*.qm"}, QDir::Files);
+        for (const QString &fileName : qmFiles)
+            languageList << getUiLanguage(modelPath, fileName);
+    }
+
+    // Now add the internal language translations
+    {
+        const QDir dir(":/i18n");
+        const QStringList qmFiles = dir.entryList({"*.qm"}, QDir::Files);
+        for (const QString &fileName : qmFiles) {
+            const QString lang = getUiLanguage(":/i18n", fileName);
+            if (!languageList.contains(lang))
+                languageList.append(lang);
+        }
+    }
+    return languageList;
+}
+
 class MyPrivateSettings: public MySettings { };
 Q_GLOBAL_STATIC(MyPrivateSettings, settingsInstance)
 MySettings *MySettings::globalInstance()
@@ -106,6 +151,7 @@ MySettings::MySettings()
     : QObject(nullptr)
     , m_deviceList(getDevices())
     , m_embeddingsDeviceList(getDevices(/*skipKompute*/ true))
+    , m_uiLanguages(getUiLanguages(modelPath()))
 {
 }
 
@@ -154,6 +200,7 @@ void MySettings::restoreApplicationDefaults()
     setUserDefaultModel(basicDefaults.value("userDefaultModel").toString());
     setForceMetal(defaults::forceMetal);
     setSuggestionMode(basicDefaults.value("suggestionMode").value<SuggestionMode>());
+    setLanguageAndLocale(defaults::languageAndLocale);
 }
 
 void MySettings::restoreLocalDocsDefaults()
@@ -521,3 +568,91 @@ void MySettings::setNetworkUsageStatsActive(bool value)
         emit networkUsageStatsActiveChanged();
     }
 }
+
+QString MySettings::languageAndLocale() const
+{
+    auto value = m_settings.value("languageAndLocale");
+    if (!value.isValid())
+        return defaults::languageAndLocale;
+    return value.toString();
+}
+
+QString MySettings::filePathForLocale(const QLocale &locale)
+{
+    // Check and see if we have a translation for the chosen locale and set it if possible otherwise
+    // we return the filepath for the 'en' translation
+    const QStringList uiLanguages = locale.uiLanguages(QLocale::TagSeparator::Underscore);
+
+    // Scan this directory for files named like gpt4all_%1.qm that match and if so return them first
+    // this is the model download directory and it can be used by translation developers who are
+    // trying to test their translations by just compiling the translation with the lrelease tool
+    // rather than having to recompile all of GPT4All
+    QString directory = modelPath();
+    for (const QString &bcp47Name : uiLanguages) {
+        QString filePath = QString("%1/gpt4all_%2.qm").arg(directory).arg(bcp47Name);
+        QFileInfo filePathInfo(filePath);
+        if (filePathInfo.exists()) return filePath;
+    }
+
+    // Now scan the internal built-in translations
+    for (QString bcp47Name : uiLanguages) {
+        QString filePath = QString(":/i18n/gpt4all_%1.qm").arg(bcp47Name);
+        QFileInfo filePathInfo(filePath);
+        if (filePathInfo.exists()) return filePath;
+    }
+    return QString(":/i18n/gpt4all_en.qm");
+}
+
+void MySettings::setLanguageAndLocale(const QString &bcp47Name)
+{
+    if (!bcp47Name.isEmpty() && languageAndLocale() != bcp47Name)
+        m_settings.setValue("languageAndLocale", bcp47Name);
+
+    // When the app is started this method is called with no bcp47Name given which sets the translation
+    // to either the default which is the system locale or the one explicitly set by the user previously.
+    QLocale locale;
+    const QString l = languageAndLocale();
+    if (l == "Default")
+        locale = QLocale::system();
+    else
+        locale = QLocale(l);
+
+    // If we previously installed a translator, then remove it
+    if (m_translator) {
+        if (!qGuiApp->removeTranslator(m_translator)) {
+            qDebug() << "ERROR: Failed to remove the previous translator";
+        } else {
+            delete m_translator;
+            m_translator = nullptr;
+        }
+    }
+
+    // We expect that the translator was removed and is now a nullptr
+    Q_ASSERT(!m_translator);
+
+    const QString filePath = filePathForLocale(locale);
+    // Installing the default gpt4all_en.qm fails presumably because it has no strings that are
+    // different from the ones stored in the binary
+    if (!m_translator && !filePath.endsWith("en.qm")) {
+        // Create a new translator object on the heap
+        m_translator = new QTranslator(this);
+        bool success = m_translator->load(filePath);
+        Q_ASSERT(success);
+        if (!success) {
+            qDebug() << "ERROR: Failed to load translation file:" << filePath;
+            delete m_translator;
+            m_translator = nullptr;
+        }
+
+        // If we've successfully loaded it, then try and install it
+        if (!qGuiApp->installTranslator(m_translator)) {
+            qDebug() << "ERROR: Failed to install the translator:" << filePath;
+            delete m_translator;
+            m_translator = nullptr;
+        }
+    }
+
+    // Finally, set the locale whether we have a translation or not
+    QLocale::setDefault(locale);
+    emit languageAndLocaleChanged();
+}