Many active QTimers timekeeping causing GUI lag - c++

Question

I have created a simple app for monitoring the connected devices. This app shows the connection status of 25 client devices.
This app implements a TCP server and listens at port 7777 and as many as 25 clients can be connected to this application. If no data is received from a client for 30 seconds, the app marks the device as "Offline".
For this purpose, QTimer for each connected device is started for 30 sec when some client connects and the payload is received. Each timer is connected to a common SLOT refreshOfflineDevices() Soon as any timer timeout occurs, refreshOfflineDevices() is called and the non-running timers corresponding to the device are marked as "Offline" in the GUI.
The app works fine and the GUI is updated instantly when the connected device count is not more than 4 or 5. As the connected devices rise, (greater than 8 or 9) the lag in the GUI update becomes obvious.
After some desk research, I assume that the parallel timers would need to be moved to a thread to avoid GUI lags. For that, I created a CyclicWorker class for separating the QTimer but not sure how this will work in this case
I need help with moving and managing all timekeeping events to a thread. Also, I need advise on my assumption of GUI lag correctness
my app GUI
monitor.h
#ifndef CENTRALMONITOR_H
#define CENTRALMONITOR_H
#include <QtCore>
#include <QMainWindow>
#include "ui_device_display.h"
#include "tcp_server.h"
#include "cyclic_worker.h"
#define MAX_DEVICES (25)
#define DEVICE_KEEP_ALIVE_MS (30*1000) // keeps track of the connection before marking "Offline"
namespace Ui
{
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
private:
Ui::MainWindow *ui;
TCPServer *ptr_server = nullptr;
QTimer *ptr_deviceTimer[MAX_DEVICES] = {nullptr};
void GUI_update(const int device_number, const QString device_status);
CyclicWorker timerThread;
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
UIDeviceDisplay *ptr_devices[MAX_DEVICES] = {nullptr};
public slots:
void parseJSON(QString response);
void refreshOfflineDevices();
};
#endif // CENTRALMONITOR_H
monitor.cpp
#include "monitor.h"
#include "ui_monitor.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
system("clear");
ui->setupUi(this);
// MyServer instance (TCPServer contains TCPClient instance).
ptr_server = new TCPServer();
connect(ptr_server, SIGNAL(uiPayloadReady(QString)), this, SLOT(parseJSON(QString)));
// draw (MAX_DEVICES) (initialize as offline)
for(int i=0 ; i<5 ; i++) // 5 rows
{
for(int j=0 ; j<5 ; j++) // 5 columns
{
ptr_devices[i*5 + j] = new UIDeviceDisplay(this, j, i);
ptr_devices[i*5 + j]->show();
QString text_device_number = QString("").append(QString::number( i*5 + j + 1) );
ptr_devices[i*5 + j]->ptr_label_device_number->setText(text_device_number);
}
}
// connect keep alive timers to use later
for(int device_idx=0; device_idx<MAX_DEVICES; device_idx++)
{
ptr_deviceTimer[device_idx] = new QTimer();
connect(ptr_deviceTimer[device_idx], SIGNAL(timeout()), this, SLOT(refreshOfflineDevices()));
this->ptr_deviceTimer[device_idx]->setSingleShot(true);
ptr_deviceTimer[device_idx]->setTimerType(Qt::PreciseTimer);
}
timerThread.start();
timerThread.threadFlag = 1;
}
MainWindow::~MainWindow()
{
delete ui;
}
/*
#brief This slot is emitted by ptr_socket readReady() signal by the TCP client handler
#param The received payload for updating GUI
*/
void MainWindow::parseJSON(const QString response)
{
const QJsonDocument jsonDocument = QJsonDocument::fromJson(response.toUtf8());
const QJsonObject jsonObjectRecords = jsonDocument.object();
const int device_number = jsonObjectRecords.value("device_number").toInt();
const QString device_status = jsonObjectRecords.value("device_status").toString();
// start time keeper for current device.
ptr_deviceTimer[device_number-1]->start(DEVICE_KEEP_ALIVE_MS);
GUI_update(device_number, device_status);
}
/*
#brief This method updates the GUI with provided params.
#param GUI update params
*/
void MainWindow::GUI_update(const int device_number, const QString device_status)
{
const int device_idx = device_number-1;
// update device label.
ptr_devices[device_idx]->ptr_label_device_status->setText(device_status);
// refresh online devices label.
int onlineCount =0;
for(int device_idx=0; device_idx<MAX_DEVICES; device_idx++)
{
if( ptr_deviceTimer[device_idx]->isActive() )
onlineCount++;
}
ui->label_online_devices->setText(QString("Online devices: %1").arg(onlineCount));
}
/*
#brief This method is called upon every device_timer expiration. It updates GUI for all the devices that are offline
*/
void MainWindow::refreshOfflineDevices()
{
for(int device_number=1; device_number<=MAX_DEVICES; device_number++)
{
// if device timer is not running, the device is offline
if( !ptr_deviceTimer[device_number-1]->isActive() )
{
GUI_update(device_number, "Offline");
}
}
}
cyclic_worker.h
#include <QDebug>
#include <QThread>
class CyclicWorker : public QThread
{
Q_OBJECT
public:
bool threadFlag; // variable used to control thread execution
CyclicWorker();
void run();
void quit();
private:
};
cyclic_worker.cpp
#include "cyclic_worker.h"
CyclicWorker::CyclicWorker()
{
qDebug() << "\nCyclicWorker object created";
threadFlag = false;
}
/*----------------------------------------------------------------------------
* void run()
*
* Return value : none
*
* Description : this function runs after thread start
*----------------------------------------------------------------------------*/
void CyclicWorker::run()
{
qDebug("Thread invoked . . .");
while(threadFlag)
{
}
}
/*----------------------------------------------------------------------------
* void quit()
*
* Return value : none
*
* Description : this function stops the running thread
*----------------------------------------------------------------------------*/
void CyclicWorker::quit()
{
qDebug() << "Thread stopped . . .";
}
ui_device_display.h
#ifndef UI_DEVICE_DISPLAY_H
#define UI_DEVICE_DISPLAY_H
#include <QtWidgets>
#define X_PADDING (30) // this is the base container widget co-ordinates
#define Y_PADDING (110)
class UIDeviceDisplay : public QFrame
{
Q_OBJECT
public:
UIDeviceDisplay(QWidget *parent = nullptr, int x=0, int y=0);
QLabel *ptr_label_device_number = nullptr;
QLabel *ptr_label_device_status = nullptr;
static const int frameWidth = 240;
static const int frameHeight = 190;
static const int deviceLabelWidth = 70;
static const int deviceLabelHeight = 50;
static const int statusLabelWidth = 150;
static const int statusLabelHeight = 30;
};
#endif
ui_device_display.cpp
#include "ui_device_display.h"
UIDeviceDisplay::UIDeviceDisplay(QWidget *parent, int x, int y) : QFrame(parent)
{
//QFrame containing all the elements.
this->setGeometry(QRect( X_PADDING + frameWidth*x, Y_PADDING + frameHeight*y, frameWidth, frameHeight));
this->hide();
//QLabel for bed number.
ptr_label_device_number = new QLabel(this);
ptr_label_device_number->setGeometry(QRect((frameWidth/2)-(deviceLabelWidth/2), 20, deviceLabelWidth, deviceLabelHeight));
ptr_label_device_number->setAlignment(Qt::AlignCenter);
//QLabel that displays the device status.
ptr_label_device_status = new QLabel(this);
ptr_label_device_status->setText("Offline");
ptr_label_device_status->setGeometry(QRect(45, 90, statusLabelWidth, statusLabelHeight));
ptr_label_device_status->setAlignment(Qt::AlignCenter);
}
tcp_server.h
#ifndef TCP_SERVER_H
#define TCP_SERVER_H
#include <QTcpServer>
#include <QTcpSocket>
#include <QAbstractSocket>
#include "tcp_client_handler.h"
class TCPServer : public QTcpServer
{
Q_OBJECT
public:
explicit TCPServer(QObject *parent=0);
protected:
void incomingConnection(int handle);
signals:
void uiPayloadReady(QString uiPayload);
public slots:
void payloadReady(QString payload);
};
#endif
tcp_server.cpp
#include "tcp_server.h"
TCPServer::TCPServer(QObject *parent) :
QTcpServer(parent)
{
if(listen(QHostAddress::Any,7777))
qDebug("DEBUG: Server listening at 7777");
else
qDebug("DEBUG: Could not start server");
}
void TCPServer::incomingConnection(int handle)
{
TCPClientHandler *ptr_client = new TCPClientHandler(this);
ptr_client->SetSocket(handle);
connect(ptr_client, SIGNAL(payloadReady(QString)), this, SLOT(payloadReady(QString)));
}
void TCPServer::payloadReady(QString payload)
{
emit uiPayloadReady(payload);
}
tcp_client_handler.h
#ifndef TCP_CLIENT_HANDLER_H
#define TCP_CLIENT_HANDLER_H
#include <QObject>
#include <QTcpSocket>
#include <QDebug>
class TCPClientHandler : public QObject
{
Q_OBJECT
public:
explicit TCPClientHandler(QObject *parent = nullptr);
void SetSocket(int Descriptor);
QTcpSocket *ptr_socket = nullptr;
signals:
void payloadReady(QString payload);
public slots:
void connected();
void disconnected();
void readReady();
private:
};
#endif
tcp_client_handler.cpp
#include "tcp_client_handler.h"
TCPClientHandler::TCPClientHandler(QObject *parent) : QObject(parent)
{
}
void TCPClientHandler::SetSocket(int Descriptor)
{
ptr_socket = new QTcpSocket(this);
connect(ptr_socket, SIGNAL(connected()), this, SLOT(connected()));
connect(ptr_socket, SIGNAL(disconnected()), this, SLOT(disconnected()));
connect(ptr_socket, SIGNAL(readyRead()), this, SLOT(readReady()));
ptr_socket->setSocketDescriptor(Descriptor);
}
void TCPClientHandler::connected()
{
//qDebug("DEBUG: client connect event");
}
void TCPClientHandler::disconnected()
{
//qDebug("DEBUG: client disconnect event");
}
void TCPClientHandler::readReady()
{
const QByteArray byteArrayResponse = ptr_socket->readAll();
const QString stringResponse = QString(byteArrayResponse);
//qDebug() << "DEBUG: " << stringResponse;
emit payloadReady(stringResponse);
}
main.cpp
#include "monitor.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.setWindowFlags(Qt::Window | Qt::FramelessWindowHint);
w.show();
return a.exec();
}