Getting the right painter inside QGraphicsView paintevent

[tonnot]

How can I get the right tranformed Painter of my GraphicsView extended class ?
To draw a temporal item not added to the scene, I have to write :

A_Gview2D::paintEvent(QPaintEvent *event) {
     QPainter painter(this->viewport());  // this is the 'widget' `painter
 
     QTransform AFT=QTransform(this->matrix());
     AFT.translate(w_temp_item->pos().x(),w_temp_item->pos().y() );
     painter.setTransform(AFT);

A_Gview2D::paintEvent(QPaintEvent *event) {
     QPainter painter(this->viewport());  // this is the 'widget' `painter
     
     QTransform AFT=QTransform(this->matrix());
     AFT.translate(w_temp_item->pos().x(),w_temp_item->pos().y() );
     painter.setTransform(AFT);

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Is any other way to get the right painter ?
Any idea ? Thanks