Add UI language selection menu

src/CMakeLists.txt

@@ -79,7 +79,8 @@ qt6_add_translations(qdmr TS_FILES
   ${PROJECT_SOURCE_DIR}/i18n/de.ts ${PROJECT_SOURCE_DIR}/i18n/en_US.ts
   ${PROJECT_SOURCE_DIR}/i18n/sv.ts ${PROJECT_SOURCE_DIR}/i18n/it.ts
   ${PROJECT_SOURCE_DIR}/i18n/nl.ts ${PROJECT_SOURCE_DIR}/i18n/pl.ts
-  ${PROJECT_SOURCE_DIR}/i18n/fr.ts ${PROJECT_SOURCE_DIR}/i18n/pt_BR.ts)
+  ${PROJECT_SOURCE_DIR}/i18n/fr.ts ${PROJECT_SOURCE_DIR}/i18n/pt_BR.ts
+  ${PROJECT_SOURCE_DIR}/i18n/ru_RU.ts)
 
 #
 # Icon generation

src/application.cc

@@ -45,10 +45,10 @@
 
 
 
-inline QStringList getLanguages() {
+static QStringList systemLocaleCandidates() {
   QStringList languages = {QLocale::system().name()};
-  if (languages.last().contains("_")) {
-    languages.append(languages.last().split("_").first());
+  if (languages.last().contains(QLatin1Char('_'))) {
+    languages.append(languages.last().split(QLatin1Char('_')).first());
   }
   return languages;
 }
@@ -75,17 +75,14 @@ Application::Application(int &argc, char *argv[])
 
   // handle translations
   _translator = new QTranslator(this);
-  foreach (QString language, getLanguages()) {
-    logDebug() << "Search for translation in ':/i18n/" << language << ".qm'.";
-    if (_translator->load(language, ":/i18n/", "", ".qm")) {
-      this->installTranslator(_translator);
-      logDebug() << "Installed translator for locale '" << QLocale::system().name() << "'.";
-      break;
-    }
+  Settings settings;
+  {
+    const QString langPref =
+        settings.uiLanguage().isEmpty() ? QStringLiteral("system") : settings.uiLanguage();
+    loadLanguage(langPref);
   }
 
-  // load settings
-  Settings settings;
+  // load settings (same Settings instance as above)
   // load databases
   _repeater   = new RepeaterDatabase(this);
   if (settings.repeaterBookSourceEnabled())
@@ -917,3 +914,41 @@ Application::onPaletteChanged(const QPalette &palette) {
 }
 
 
+bool
+Application::loadLanguage(const QString &localeId) {
+  removeTranslator(_translator);
+  bool loaded = false;
+  const bool useSystemLocale =
+      localeId.isEmpty() || localeId == QStringLiteral("system");
+
+  if (! useSystemLocale) {
+    logDebug() << "Try translation ':/i18n/" << localeId << ".qm'.";
+    loaded = _translator->load(localeId, QStringLiteral(":/i18n/"), QString(), QStringLiteral(".qm"));
+    if (! loaded && localeId.contains(QLatin1Char('_'))) {
+      const QString shortTag = localeId.split(QLatin1Char('_')).first();
+      loaded = _translator->load(shortTag, QStringLiteral(":/i18n/"), QString(), QStringLiteral(".qm"));
+    }
+  } else {
+    foreach (const QString &cand, systemLocaleCandidates()) {
+      logDebug() << "Try system translation ':/i18n/" << cand << ".qm'.";
+      loaded = _translator->load(cand, QStringLiteral(":/i18n/"), QString(), QStringLiteral(".qm"));
+      if (loaded)
+        break;
+    }
+  }
+
+  if (! loaded) {
+    logDebug() << "Fallback to ':/i18n/en_US.qm'.";
+    loaded = _translator->load(QStringLiteral("en_US"), QStringLiteral(":/i18n/"), QString(),
+                               QStringLiteral(".qm"));
+  }
+
+  if (loaded) {
+    installTranslator(_translator);
+    logDebug() << "Installed translator for UI language preference '" << localeId << "'.";
+  } else {
+    logError() << "Failed to load any translation.";
+  }
+
+  return loaded;
+}

src/application.hh

@@ -89,6 +89,9 @@ private slots:
 
   void onPaletteChanged(const QPalette &palette);
 
+private:
+  bool loadLanguage(const QString &localeId);
+
 protected:
   Config *_config;
   MainWindow *_mainWindow;

src/mainwindow.cc

@@ -1,5 +1,6 @@
 #include "mainwindow.hh"
 #include "ui_mainwindow.h"
+#include <QActionGroup>
 #include <QProgressBar>
 #include <QCloseEvent>
 #include <QMessageBox>
@@ -26,7 +27,7 @@
 
 
 MainWindow::MainWindow(Config *config, QWidget *parent)
-  : QMainWindow(parent), ui(new Ui::MainWindow)
+  : QMainWindow(parent), ui(new Ui::MainWindow), _languageGroup(nullptr)
 {
   ui->setupUi(this);
   Application *app = qobject_cast<Application*>(QApplication::instance());
@@ -102,6 +103,45 @@ MainWindow::MainWindow(Config *config, QWidget *parent)
   connect(ui->actionUpload, SIGNAL(triggered()), app, SLOT(uploadCodeplug()));
   connect(ui->actionWriteSatellites, SIGNAL(triggered()), app, SLOT(uploadSatellites()));
 
+  _languageGroup = new QActionGroup(this);
+  _languageGroup->setExclusive(true);
+  ui->menuLanguage->clear();
+  // Locale ids match basenames of i18n/*.ts shipped as :/i18n/*.qm
+  static const struct {
+    const char *id;
+    const char *label;
+  } kUiLanguages[] = {
+      {"system", QT_TR_NOOP("System default")},
+      {"de", QT_TR_NOOP("German")},
+      {"en_US", QT_TR_NOOP("English")},
+      {"fr", QT_TR_NOOP("French")},
+      {"it", QT_TR_NOOP("Italian")},
+      {"nl", QT_TR_NOOP("Dutch")},
+      {"pl", QT_TR_NOOP("Polish")},
+      {"pt_BR", QT_TR_NOOP("Portuguese (Brazil)")},
+      {"ru_RU", QT_TR_NOOP("Russian")},
+      {"sv", QT_TR_NOOP("Swedish")},
+  };
+  for (const auto &entry : kUiLanguages) {
+    const QString id = QString::fromLatin1(entry.id);
+    QAction *a = ui->menuLanguage->addAction(tr(entry.label));
+    a->setCheckable(true);
+    a->setData(id);
+    _languageGroup->addAction(a);
+    QObject::connect(a, &QAction::triggered, this, [this, id]() {
+      const QString before =
+          Settings().uiLanguage().isEmpty() ? QStringLiteral("system") : Settings().uiLanguage();
+      Settings().setUiLanguage(id);
+      updateLanguageMenuChecks();
+      if (before != id) {
+        QMessageBox::information(
+              this, tr("Language"),
+              tr("The language will be applied fully after you restart the application."));
+      }
+    });
+  }
+  updateLanguageMenuChecks();
+
   // Wire-up "General Settings" view
   _generalSettings = new GeneralSettingsView(config);
   ui->tabs->addTab(_generalSettings, tr("Settings"));
@@ -139,6 +179,21 @@ MainWindow::MainWindow(Config *config, QWidget *parent)
 }
 
 
+void
+MainWindow::updateLanguageMenuChecks() {
+  const QString sel =
+      Settings().uiLanguage().isEmpty() ? QStringLiteral("system") : Settings().uiLanguage();
+  for (QAction *a : _languageGroup->actions()) {
+    if (a->data().toString() == sel) {
+      a->setChecked(true);
+      return;
+    }
+  }
+  if (!_languageGroup->actions().isEmpty())
+    _languageGroup->actions().first()->setChecked(true);
+}
+
+
 void
 MainWindow::closeEvent(QCloseEvent *event) {
   if (qobject_cast<Application*>(Application::instance())->isModified()) {

src/mainwindow.hh

@@ -3,6 +3,8 @@
 
 #include <QMainWindow>
 
+class QActionGroup;
+
 class Config;
 class GeneralSettingsView;
 class RadioIDListView;
@@ -24,7 +26,10 @@ protected:
   void closeEvent(QCloseEvent *event);
 
 private:
+  void updateLanguageMenuChecks();
+
   Ui::MainWindow *ui;
+  QActionGroup *_languageGroup;
   GeneralSettingsView *_generalSettings;
   RadioIDListView *_radioIdTab;
   RoamingZoneListView *_roamingZoneList;

src/mainwindow.ui

@@ -109,9 +109,15 @@
     <addaction name="actionRefreshOrbitalElements"/>
     <addaction name="actionEditSatellites"/>
    </widget>
+   <widget class="QMenu" name="menuLanguage">
+    <property name="title">
+     <string>Language</string>
+    </property>
+   </widget>
    <addaction name="menuFile"/>
    <addaction name="menuDevice"/>
    <addaction name="menuDatabases"/>
+   <addaction name="menuLanguage"/>
    <addaction name="menuHelp"/>
   </widget>
   <widget class="QStatusBar" name="statusbar">

src/settings.cc

@@ -301,6 +301,16 @@ Settings::setShowDisclaimer(bool show) {
   setValue("showDisclaimer", show);
 }
 
+QString
+Settings::uiLanguage() const {
+  return value("uiLanguage", QStringLiteral("system")).toString();
+}
+
+void
+Settings::setUiLanguage(const QString &localeId) {
+  setValue("uiLanguage", localeId);
+}
+
 ConfigMergeVisitor::ItemStrategy
 Settings::configMergeItemStrategy() const {
   return (ConfigMergeVisitor::ItemStrategy)value(

src/settings.hh

@@ -97,6 +97,10 @@ public:
   bool showDisclaimer() const;
   void setShowDisclaimer(bool show);
 
+  /// Application UI language: `"system"` or a locale tag matching `i18n/*.qm` (e.g. `en_US`, `de`, `ru_RU`).
+  QString uiLanguage() const;
+  void setUiLanguage(const QString &localeId);
+
   ConfigMergeVisitor::ItemStrategy configMergeItemStrategy() const;
   void setConfigMergeItemStrategy(ConfigMergeVisitor::ItemStrategy strategy);