Subclass QGraphicsPixmapItem and paint(draw) on pixmap() directly

[A Former User]

I want to create a custom QGraphicsPixmapItem and be able to draw on pixmap() directly. Any Suggestions?

This is what I want to do:

@
void myPixmapItem::drawLineTO(const QPointF &endPoint)
{
QPainter painter(&pixmap());
painter.drawLine(lastPoint, endPoint);
modified = true;
int rad = (penWidth /2)+2;
update(QRect(lastPoint.toPoint(), endPoint.toPoint().normalized().adjusted(-rad, -rad, +rad, +rad);
lastPoint = endPoint;

}
@
This crashes and I get the following error:
QPaintDevice: Cannot destroy paint device that is being painted

This is what works but is sluggish because I have to use a copy.

@
created in the header:
QPixmap pmap;

In the constructor:
pmap = pixmap();

void myPixmapItem::drawLineTO(const QPointF &endPoint)
{
QPainter painter(&pmap);
painter.drawLine(lastPoint, endPoint);
modified = true;
int rad = (penWidth /2)+2;
update(QRect(lastPoint.toPoint(), endPoint.toPoint().normalized().adjusted(-rad, -rad, +rad, +rad);
lastPoint = endPoint;
setPixmap(pmap);
}@