How to add items in a QGraphicsScene?

[schmimona]

Hi,

I am trying to add some custom QGraphicsItems in a QGraphicsScene on mouse click and at mouse cursor coordinates. But the items are not added at the same coordinates as the mouse cursor's.

renderArea::renderArea(QWidget *parent):
            QGraphicsView(parent)
    {
        scene = new QGraphicsScene(this);
        scene->setItemIndexMethod(QGraphicsScene::NoIndex);
        scene->setSceneRect(0, 0, 850, 480);
        setScene(scene);
        setCacheMode(CacheBackground);
        setViewportUpdateMode(BoundingRectViewportUpdate);
        setRenderHint(QPainter::Antialiasing);
        setTransformationAnchor(AnchorUnderMouse);
        scale(qreal(1.0), qreal(1.0));
        setMinimumSize(400, 400);
    }
 
    void renderArea::mousePressEvent(QMouseEvent *event)
    {
        QPoint p = event->pos();
 
    updateList(p);
    }
 
    void renderArea::updateList(const QPoint &p)
    {
        Point point;
        point.point = p;
        point.isSelected = false;
        list.append(point);
        if (list.size() > 1)
            updateClothoid(list[list.size()-2].point, list[list.size()-1].point);
    }
 
    void renderArea::updateClothoid(const QPoint &p1, const QPoint &p2)
    {
        Clothoid *temp = new Clothoid(p1, p2);
 
        clothoids.append(temp);
 
        scene->addItem(temp);
    }

renderArea::renderArea(QWidget *parent):
            QGraphicsView(parent)
    {
        scene = new QGraphicsScene(this);
        scene->setItemIndexMethod(QGraphicsScene::NoIndex);
        scene->setSceneRect(0, 0, 850, 480);
        setScene(scene);
        setCacheMode(CacheBackground);
        setViewportUpdateMode(BoundingRectViewportUpdate);
        setRenderHint(QPainter::Antialiasing);
        setTransformationAnchor(AnchorUnderMouse);
        scale(qreal(1.0), qreal(1.0));
        setMinimumSize(400, 400);
    }
    
    void renderArea::mousePressEvent(QMouseEvent *event)
    {
        QPoint p = event->pos();
    
    updateList(p);
    }
    
    void renderArea::updateList(const QPoint &p)
    {
        Point point;
        point.point = p;
        point.isSelected = false;
        list.append(point);
        if (list.size() > 1)
            updateClothoid(list[list.size()-2].point, list[list.size()-1].point);
    }
    
    void renderArea::updateClothoid(const QPoint &p1, const QPoint &p2)
    {
        Clothoid *temp = new Clothoid(p1, p2);
    
        clothoids.append(temp);
    
        scene->addItem(temp);
    }

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renderArea being the QGraphicsView and Clothoids the custom QGraphicsItem

Clothoid::Clothoid(QPoint startPoint, QPoint endPoint)
    {
        sPoint = startPoint;
        ePoint = endPoint;
        startCurvature = 0.0;
        endCurvature = 0.0;
        clothoidLength = sqrt(pow(endPoint.x() - startPoint.x(),2) +
                              pow(endPoint.y() - startPoint.y(),2));
    }    
 
    QRectF Clothoid::boundingRect() const
        {
            qreal penWidth = 1;
 
            if ((sPoint.x() &lt ePoint.x()) && (sPoint.y() &lt ePoint.y()))
                return QRectF(sPoint.x(), sPoint.y(), ePoint.x() - sPoint.x(), ePoint.y()-sPoint.y())
                .normalized()
                .adjusted(-penWidth, -penWidth, penWidth, penWidth);
 
            if ((sPoint.x() &lt ePoint.x()) && (sPoint.y() > ePoint.y()))
                return QRectF(sPoint.x(), ePoint.y(), ePoint.x() - sPoint.x(), sPoint.y() - ePoint.y())
                .normalized()
                .adjusted(-penWidth, -penWidth, penWidth, penWidth);
 
            if ((sPoint.x() > ePoint.x()) && (sPoint.y() &lt ePoint.y()))
                return QRectF(ePoint.x(), sPoint.y(), sPoint.x() - ePoint.x(), ePoint.y()-sPoint.y())
                .normalized()
                .adjusted(-penWidth, -penWidth, penWidth, penWidth);
 
            if ((sPoint.x() > ePoint.x()) && (sPoint.y() > ePoint.y()))
                return QRectF(ePoint.x(), ePoint.y(), sPoint.x() - ePoint.x(), sPoint.y() - ePoint.y())
                .normalized()
                .adjusted(-penWidth, -penWidth, penWidth, penWidth);
 
            return QRectF();
 
        }
 
        void Clothoid::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
        {
            QLineF line(sPoint, ePoint);
 
            // Draw the line itself
            painter->setPen(QPen(Qt::black, 1, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
            painter->drawLine(line);
        }

Clothoid::Clothoid(QPoint startPoint, QPoint endPoint)
    {
        sPoint = startPoint;
        ePoint = endPoint;
        startCurvature = 0.0;
        endCurvature = 0.0;
        clothoidLength = sqrt(pow(endPoint.x() - startPoint.x(),2) +
                              pow(endPoint.y() - startPoint.y(),2));
    }    
    
    QRectF Clothoid::boundingRect() const
        {
            qreal penWidth = 1;
        
            if ((sPoint.x() &lt ePoint.x()) && (sPoint.y() &lt ePoint.y()))
                return QRectF(sPoint.x(), sPoint.y(), ePoint.x() - sPoint.x(), ePoint.y()-sPoint.y())
                .normalized()
                .adjusted(-penWidth, -penWidth, penWidth, penWidth);
        
            if ((sPoint.x() &lt ePoint.x()) && (sPoint.y() > ePoint.y()))
                return QRectF(sPoint.x(), ePoint.y(), ePoint.x() - sPoint.x(), sPoint.y() - ePoint.y())
                .normalized()
                .adjusted(-penWidth, -penWidth, penWidth, penWidth);
        
            if ((sPoint.x() > ePoint.x()) && (sPoint.y() &lt ePoint.y()))
                return QRectF(ePoint.x(), sPoint.y(), sPoint.x() - ePoint.x(), ePoint.y()-sPoint.y())
                .normalized()
                .adjusted(-penWidth, -penWidth, penWidth, penWidth);
        
            if ((sPoint.x() > ePoint.x()) && (sPoint.y() > ePoint.y()))
                return QRectF(ePoint.x(), ePoint.y(), sPoint.x() - ePoint.x(), sPoint.y() - ePoint.y())
                .normalized()
                .adjusted(-penWidth, -penWidth, penWidth, penWidth);
        
            return QRectF();
        
        }
        
        void Clothoid::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
        {
            QLineF line(sPoint, ePoint);
        
            // Draw the line itself
            painter->setPen(QPen(Qt::black, 1, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
            painter->drawLine(line);
        }

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I am guessing that the coordinates to which I am inserting the items belong to the GraphicsView and not the scene as in my application the scene doesn't cover the entire view. But how could I get the coordinates of the scene in my case?

[vallidor]

hmm, i may not be seeing the code which actuates the rendering to your scene in its entirety, but i would expect to see a 'QPointF QGraphicsView::mapToScene ( const QPoint & point ) const' in use to translate the click coordinates from the View to Scene coordinates, probably in updateList(). is this what you meant?

[schmimona]

yes..that was exactly what I meant. Thanks. It works now.