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 void MainWindow::closeEvent(QCloseEvent *event)  {
     if (trayIcon->isVisible()) {
         hide();
         event->ignore();
     }
 }

connect(this, SIGNAL(signalPlaceToTray()),this, SLOT(slotPlaceToTray()), Qt::QueuedConnection);

void MainWindow::changeEvent(QEvent *event) {
    if (event->type() == QEvent::WindowStateChange)
    {
        if (isMinimized())
        {
            event->ignore();
            emit signalPlaceToTray();
            return;
        }
    }
    QMainWindow::changeEvent(event);
}

void MainWindow::slotPlaceToTray() {
    hide();
}

connect(restoreAction, SIGNAL(triggered()), this, SLOT(showNormal()));

 void MainWindow::iconActivated(QSystemTrayIcon::ActivationReason reason) {
     switch (reason) {
     case QSystemTrayIcon::Trigger:
     case QSystemTrayIcon::DoubleClick:
         showNormal();
         break;
     }
 }