Take a screenshot of current monitor

[MarianaB]

I have three monitors and when I start my QT application, it starts on the monitor where the mouse cursor is in. Is there a way to specify the monitor number when taking a screenshot with QScreen::grabWindow() (on QT5)?
I tried this but it does not work (the taken screenshot is always of the primary monitor).
@
QDesktopWidget* desktop = QApplication::desktop();
QPixmap screenShot;
QScreen* myScreen = QApplication::screens()[desktop->screenNumber(m_mainAreaWidget)];

if (myScreen)
{
screenShot = myScreen->grabWindow(desktop->screen(desktop->screenNumber(m_mainAreaWidget))->winId());
}@

[hpollak]

Which OS to you use?

[MarianaB]

Windows 7, with Visual studio 2013.