Keep legacy defaults for existing users

src/app/main.cpp

@@ -237,6 +237,8 @@ int main(int argc, char *argv[])
 #endif
 
         if (!firstTimeUser) {
+            handleChangedDefaults(DefaultPreferencesMode::Legacy);
+
 #ifndef DISABLE_GUI
             if (!upgrade()) return EXIT_FAILURE;
 #elif defined(Q_OS_WIN)
@@ -248,6 +250,10 @@ int main(int argc, char *argv[])
                          && isatty(fileno(stdout)))) return EXIT_FAILURE;
 #endif
         }
+        else {
+            handleChangedDefaults(DefaultPreferencesMode::Current);
+        }
+
 #if defined(DISABLE_GUI) && !defined(Q_OS_WIN)
         if (params.shouldDaemonize) {
             app.reset(); // Destroy current application

src/app/upgrade.cpp

@@ -82,3 +82,23 @@ bool upgrade(const bool /*ask*/)
     exportWebUIHttpsFiles();
     return true;
 }
+
+void handleChangedDefaults(const DefaultPreferencesMode mode)
+{
+    struct DefaultValue
+    {
+        QString name;
+        QVariant legacy;
+        QVariant current;
+    };
+
+    const QVector<DefaultValue> changedDefaults {
+        {QLatin1String {"BitTorrent/Session/QueueingSystemEnabled"}, true, false}
+    };
+
+    SettingsStorage *settingsStorage {SettingsStorage::instance()};
+    for (auto it = changedDefaults.cbegin(); it != changedDefaults.cend(); ++it) {
+        if (settingsStorage->loadValue(it->name).isNull())
+            settingsStorage->storeValue(it->name, (mode == DefaultPreferencesMode::Legacy ? it->legacy : it->current));
+    }
+}

src/app/upgrade.h

@@ -28,4 +28,11 @@
 
 #pragma once
 
+enum class DefaultPreferencesMode
+{
+    Legacy,
+    Current
+};
+
+void handleChangedDefaults(DefaultPreferencesMode mode);
 bool upgrade(bool ask = true);