How do I paint with QPainter?

Question

I have started learning Qt recently.
I did not get quite clear how can I paint using QPainter class. Let`s say I want just to place a few points in the win

Answer 1

void SimpleExampleWidget::paintEvent(QPaintEvent *)
{
     QPainter painter(this);
     painter.setPen(Qt::blue);
     painter.setFont(QFont("Arial", 30));
     painter.drawText(rect(), Qt::AlignCenter, "Qt");
}

http://doc.qt.digia.com/4.4/qpainter.html