: QApplication(argc, argv)

, m_alreadyRunning(false)

, m_lockFile(nullptr)

{

QString userName = qgetenv("USER");

if (userName.isEmpty()) {

userName = qgetenv("USERNAME");

}

QString identifier = "feather";

if (!userName.isEmpty()) {

identifier += "-" + userName;

}

QString lockName = identifier + ".lock";

m_socketName = identifier + ".socket";

// According to documentation we should use RuntimeLocation on *nixes, but even Qt doesn't respect

// this and creates sockets in TempLocation, so let's be consistent.

m_lockFile = new QLockFile(QStandardPaths::writableLocation(QStandardPaths::TempLocation) + "/" + lockName);

m_lockFile->setStaleLockTime(0);

m_lockFile->tryLock();

m_lockServer.setSocketOptions(QLocalServer::UserAccessOption);

connect(&m_lockServer, SIGNAL(newConnection()), this, SIGNAL(anotherInstanceStarted()));

connect(&m_lockServer, &QLocalServer::newConnection, this, &Application::processIncomingConnection);

switch (m_lockFile->error()) {

case QLockFile::NoError:

// No existing lock was found, start listener

m_lockServer.listen(m_socketName);

break;

case QLockFile::LockFailedError: {

// Attempt to connect to the existing instance

QLocalSocket client;

for (int i = 0; i < 3; ++i) {

client.connectToServer(m_socketName);

if (client.waitForConnected(WaitTimeoutMSec)) {

// Connection succeeded, this will raise the existing window if minimized

client.abort();

m_alreadyRunning = true;

break;

}

}

if (!m_alreadyRunning) {

// If we get here then the original instance is likely dead

qWarning() << "Existing single-instance lock file is invalid. Launching new instance.";

// forceably reset the lock file

m_lockFile->removeStaleLockFile();

m_lockFile->tryLock();

// start the listen server

m_lockServer.listen(m_socketName);

}

break;

}

default:

qWarning() << "The lock file could not be created. Single-instance mode disabled.";

}

{

qDebug() << "We got an incoming connection";

if (m_lockServer.hasPendingConnections()) {

QLocalSocket* socket = m_lockServer.nextPendingConnection();

socket->setProperty(BlockSizeProperty, 0);

}