Only enforce single instance if launched with arguments.

Took 5 minutes

cockatrice/src/main.cpp

@@ -277,18 +277,31 @@ int main(int argc, char *argv[])
     SpoilerBackgroundUpdater spoilerBackgroundUpdater;
 
     // --- Handle files or URLs passed at startup ---
-    SingleInstanceManager instance;
     QStringList startupFiles;
-
-    // Collect command-line files/URLs
     for (int i = 1; i < argc; ++i) {
-        QString arg = QString::fromLocal8Bit(argv[i]);
-        startupFiles.append(arg);
+        startupFiles.append(QString::fromLocal8Bit(argv[i]));
     }
 
-    if (!instance.tryRun(startupFiles)) {
-        // Another instance received our files, exit
-        return 0;
+    bool hasActivationFiles = !startupFiles.isEmpty();
+
+    SingleInstanceManager instance;
+
+    if (hasActivationFiles) {
+        // Activation launch: try to forward
+        if (!instance.tryRun(startupFiles)) {
+            // Sent successfully → exit
+            return 0;
+        }
+        // No primary instance → become server
+        qInfo() << "No existing instance found, becoming primary instance";
+    } else {
+        // Plain launch: try to start server, but do not connect to any existing
+        if (!instance.tryRun(QStringList())) {
+            // Server already exists → just run independently
+            qInfo() << "Another instance exists, running independently";
+        } else {
+            qInfo() << "No existing instance found, starting server";
+        }
     }
 
     ui.show();
@@ -328,18 +341,6 @@ int main(int argc, char *argv[])
         }
     });
 
-#ifdef Q_OS_MAC
-    // macOS: handle files opened via Finder after startup
-    QObject::connect(&app, &QApplication::fileOpen, [&ui](const QString &filePath) {
-        qDebug() << "macOS opened file:" << filePath;
-        std::optional<LoadedDeck> deckOpt =
-            DeckLoader::loadFromFile(filePath, DeckFileFormat::getFormatFromName(filePath), true);
-        if (deckOpt) {
-            ui.getTabSupervisor()->openDeckInNewTab(deckOpt.value());
-        }
-    });
-#endif
-
     int ret = app.exec();
 
     qCInfo(MainLog) << "Event loop finished, terminating...";

cockatrice/src/single_instance_manager.cpp

@@ -4,35 +4,35 @@ SingleInstanceManager::SingleInstanceManager(QObject *parent) : QObject(parent)
 {
 }
 
-bool SingleInstanceManager::tryRun(const QStringList &initialFiles)
+bool SingleInstanceManager::tryRun(const QStringList &filesToSend)
 {
     serverName = "CockatriceSingleInstance";
 
-    QLocalSocket socket;
-    socket.connectToServer(serverName);
+    // Attempt to connect only if we have files to send
+    if (!filesToSend.isEmpty()) {
+        QLocalSocket socket;
+        socket.connectToServer(serverName);
+        if (socket.waitForConnected(200)) {
+            // Serialize payload with length prefix
+            QByteArray payload;
+            QDataStream out(&payload, QIODevice::WriteOnly);
+            out << filesToSend;
 
-    if (socket.waitForConnected(200)) {
-        // Serialize into buffer first
-        QByteArray payload;
-        QDataStream out(&payload, QIODevice::WriteOnly);
-        out << initialFiles;
+            QByteArray message;
+            QDataStream msgStream(&message, QIODevice::WriteOnly);
+            msgStream << quint32(payload.size());
+            message.append(payload);
 
-        // Prefix with size
-        QByteArray message;
-        QDataStream msgStream(&message, QIODevice::WriteOnly);
-        msgStream << quint32(payload.size());
-        message.append(payload);
+            socket.write(message);
+            socket.flush();
+            socket.waitForBytesWritten(1000);
 
-        socket.write(message);
-        socket.flush();
-        socket.waitForBytesWritten(1000);
-
-        return false; // Another instance is running
+            return false; // Sent successfully → exit
+        }
     }
 
-    // No other instance → start server
+    // Otherwise, start server
     server = new QLocalServer(this);
-
     connect(server, &QLocalServer::newConnection, this, &SingleInstanceManager::handleNewConnection);
 
     if (!server->listen(serverName)) {
@@ -40,8 +40,9 @@ bool SingleInstanceManager::tryRun(const QStringList &initialFiles)
         server->listen(serverName);
     }
 
-    return true;
+    return true; // This process is now primary server
 }
+
 void SingleInstanceManager::handleNewConnection()
 {
     QLocalSocket *socket = server->nextPendingConnection();