Starts the selection process for this widget and snapshot area.
        
        :param      event | <QMousePressEvent>

def mousePressEvent(self, event):
        """
        Starts the selection process for this widget and snapshot area.
        
        :param      event | <QMousePressEvent>
        """
        self._region.setX(event.pos().x())
        self._region.setY(event.pos().y())
        super(XSnapshotWidget, self).mousePressEvent(event)