paintEvent and Pixmap - not deleting old content!

Hi,

I would like to paint on a widget, but every time I call another function, it deletes the old widget content.

I already tried to create an instance of Pixmap with

Code:

pixmap = QPixmap(pixmap);

and removed fill() but this doesn't work.

Why is it possible to call

Code:

pixmap = QPixmap(size());

but not

Code:

pixmap = QPixmap(pixmap); ??

Here is the code snippet:

Code:

void ClientWindow::paintEvent(QPaintEvent * /* event */)
{
    QStylePainter painter(this);
    painter.drawPixmap(0, 0, pixmap);
 
    if (hasFocus()) {
        QStyleOptionFocusRect option;
        option.initFrom(this);
        option.backgroundColor = palette().dark().color();
        //painter.drawPrimitive(QStyle::PE_FrameFocusRect, option);
    }
}
 
void ClientWindow::drawCircle(int x, int y, int width, int height)
{
    pixmap = QPixmap(size());
    pixmap.fill(this, 0, 0);
 
    QPainter painter(&pixmap);
    painter.initFrom(this);
 
    pen.setStyle(Qt::SolidLine);
    pen.setWidth(3);
    pen.setBrush(Qt::green);
    pen.setCapStyle(Qt::RoundCap);
    pen.setJoinStyle(Qt::RoundJoin);
 
    brush.setStyle(Qt::SolidPattern);
 
    painter.setPen(pen);
    //painter.setBrush(brush);
 
    if (antialiased)
        painter.setRenderHint(QPainter::Antialiasing, true);
    painter.drawEllipse(x, y, width, height);
    update();
}
 
void ClientWindow::drawLine(int x1, int y1, int x2, int y2)
{
    pixmap = QPixmap(size());
    pixmap.fill(this, 0, 0);
 
    QPainter painter(&pixmap);
    painter.initFrom(this);
 
 //...