Method mqttConnectionChanged

src/frontend/datasources/ImportFileWidget.cpp:2581–2630

! *\brief called when a different MQTT connection is selected in the connection ComboBox. * connects to the MQTT broker according to the connection settings. */

 * connects to the MQTT broker according to the connection settings.
 */
void ImportFileWidget::mqttConnectionChanged() {
	if (m_initialisingMQTT || ui.cbConnection->currentIndex() == -1) {
		ui.lLWT->hide();
		ui.bLWT->hide();
		ui.lMqttTopics->hide();
		return;
	}

	WAIT_CURSOR;
	CleanupNoArguments cleanup([] () {
		RESET_CURSOR;
	});
	Q_EMIT error(QString());

	// disconnected from the broker that was selected before
	disconnectMqttConnection();

	delete m_client;
	m_client = new QMqttClient;
	connect(m_client, &QMqttClient::connected, this, &ImportFileWidget::onMqttConnect);
	connect(m_client, &QMqttClient::disconnected, this, &ImportFileWidget::onMqttDisconnect);
	connect(m_client, &QMqttClient::messageReceived, this, &ImportFileWidget::mqttMessageReceived);
	connect(m_client, &QMqttClient::errorChanged, this, &ImportFileWidget::mqttErrorChanged);

	// determine the connection settings for the new broker and initialize the mqtt client
	KConfig config(m_configPath, KConfig::SimpleConfig);
	KConfigGroup group = config.group(ui.cbConnection->currentText());
	m_client->setHostname(group.readEntry("Host"));
	m_client->setPort(group.readEntry("Port").toUInt());

	const bool useID = group.readEntry("UseID").toUInt();
	if (useID)
		m_client->setClientId(group.readEntry("ClientID"));

	const bool useAuthentication = group.readEntry("UseAuthentication").toUInt();
	if (useAuthentication) {
		m_client->setUsername(group.readEntry("UserName"));
		m_client->setPassword(group.readEntry("Password"));
	}

	// connect to the selected broker
	QDEBUG("Connect to " << m_client->hostname() << ":" << m_client->port());
	if (!m_connectTimeoutTimer) {
		m_connectTimeoutTimer = new QTimer(this);
		m_connectTimeoutTimer->setInterval(6000);
		connect(m_connectTimeoutTimer, &QTimer::timeout, this, &ImportFileWidget::mqttConnectTimeout);
	}
	m_connectTimeoutTimer->start();
	m_client->connectToHost();
}

void ImportFileWidget::disconnectMqttConnection() {
	if (m_client && m_client->state() == QMqttClient::ClientState::Connected) {