C++ (Qt)
connect(sysTrayIcon, SIGNAL(activated(QSystemTrayIcon::ActivationReason)), SLOT(sysTrayActivated(QSystemTrayIcon::ActivationReason)));
...
void AutoEmpImporter::sysTrayActivated(QSystemTrayIcon::ActivationReason reason)
{
	if (reason == QSystemTrayIcon::DoubleClick)
		show();
}
 

C++ (Qt)
QFile f("in.txt");
int n = 0;
if (f.open(QIODevice::ReadOnly | QIODevice::Text)
   n = QTextStream(&f).readAll().split('\n').count();