void QWidget::activateWindow () 

#ifdef Q_OS_WIN
#define _WIN32_WINNT 0x0501
#include <qt_windows.h>
#endif

int main(int argc, char* argv[])
{
#ifdef Q_OS_WIN
	AllowSetForegroundWindow(ASFW_ANY);
#endif
//...

void MyMainWindow::activate()
{
	setWindowState(windowState() & ~Qt::WindowMinimized);
	raise();
	activateWindow();
}

void MainWindow::trayIconActivated(QSystemTrayIcon::ActivationReason reason)
{
	switch(reason)
	{
		case QSystemTrayIcon::Trigger:
			if(isMinimized())
			{
				setWindowState(windowState() & ~Qt::WindowMinimized | Qt::WindowActive);
			}
			else if(!isVisible())
			{
				show();
				activateWindow();
			}
			else
			{
				hide();
			}
			break;
		case QSystemTrayIcon::DoubleClick:
		default:
			break;
	}
}