paint with mouse

[Vincenzo]

I want paint some circle by press the mouse button.

void GraphArea::mousePressEvent1(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton) {
        show = true;  
    }
}
 
void GraphArea::paintEvent(QPaintEvent * /*event*/)
{
    QPainter painter(this);
    if (show)
        paintCircle1(painter);
}

void GraphArea::mousePressEvent1(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton) {
        show = true;  
    }
}

void GraphArea::paintEvent(QPaintEvent * /*event*/)
{
    QPainter painter(this);
    if (show)
        paintCircle1(painter);
}

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It works...
...but my plan/problem is: if i press mouse button 2nd time, then paint 2nd circle, to third press clear the whole widget - I don't know how to do it!

PS.: sorry for my english...