QGraphicsView coordinate system

[totem]

That didn´t work either I´m afraid

What happened then ?

Speaking of zoom method, here is how I usually do :

void MyView::wheelEvent(QWheelEvent *e)
{
        const qreal zoomStep = 0.25 ;
        double zoomFactor = pow( 2.0, e->delta() / 8.0 / 15.0 * zoomStep ) ;
        scale(zoomFactor, zoomFactor);
 
        e->setModifiers(Qt::NoModifier) ; // to avoid [CTRL+wheel] behave like QAbstractScrollArea, maybe not useful for everyone
        QGraphicsView::wheelEvent(e) ;
}

void MyView::wheelEvent(QWheelEvent *e)
{
        const qreal zoomStep = 0.25 ;
        double zoomFactor = pow( 2.0, e->delta() / 8.0 / 15.0 * zoomStep ) ;
        scale(zoomFactor, zoomFactor);

        e->setModifiers(Qt::NoModifier) ; // to avoid [CTRL+wheel] behave like QAbstractScrollArea, maybe not useful for everyone
        QGraphicsView::wheelEvent(e) ;
}

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Plus, you can choose to zoom on view's center or under cursor using QGraphiscView::transformationAnchor