QSvgRenderer render does not work properly when it's passed elementId and rect bigger than the size of the element in the *.svg file

#ifndef MYSVGITEM_H
#define MYSVGITEM_H

#include <QGraphicsSvgItem>

class MySvgItem : public QGraphicsSvgItem
{
public:
    MySvgItem(QGraphicsItem* parent = 0);
    MySvgItem(const QString& fileName, QGraphicsItem* parent = 0);

    //==================
    // SETTERS & GETTERS
            void   setSize(QSizeF size);
    /*inl*/ void   setSize(qreal width, qreal height);
            QSizeF size();

    //========================================================
    // REIMPLEMENTATION OF VIRTUAL METHODS OF QGRAPHICSSVGITEM
    void paint(QPainter* painter, const QStyleOptionGraphicsItem* option, QWidget* widget = 0);
    QRectF boundingRect();

private:
    QSizeF size_m;
};

inline void   MySvgItem::setSize(qreal width, qreal height) { setSize(QSizeF(width, height)); }

#endif // MYSVGITEM_H

#include "mysvgitem.h"
#include <QSvgRenderer>
#include <QStyleOptionGraphicsItem>

MySvgItem::MySvgItem(QGraphicsItem* parent)
    : QGraphicsSvgItem(parent), size_m(-1.0, -1.0)
{
}

MySvgItem::MySvgItem(const QString& fileName, QGraphicsItem* parent)
    : QGraphicsSvgItem(fileName, parent), size_m(-1.0, -1.0)
{
}

void MySvgItem::paint(QPainter* painter, const QStyleOptionGraphicsItem* option, QWidget* widget)
{
    //QGraphicsSvgItem::paint(painter, option, widget);

    Q_UNUSED(widget);
    Q_UNUSED(option);

    if (!renderer()->isValid())
        return;

    if (elementId().isEmpty())
        renderer()->render(painter, boundingRect());
    else
        renderer()->render(painter, elementId(), boundingRect());
}

void MySvgItem::setSize(QSizeF size)
{
    if (size_m != size) {
        prepareGeometryChange();
        size_m = size;
        update(boundingRect());
    }
}

QSizeF MySvgItem::size()
{
    qreal width = size_m.width();
    qreal height = size_m.height();

    if (size_m.width() < 0) {
        width = (renderer()->boundsOnElement(elementId()).size().width());
    }

    if (size_m.height() < 0) {
        height = (renderer()->boundsOnElement(elementId()).size().width());
    }

    return QSizeF(width, height);
}

QRectF MySvgItem::boundingRect()
{
    return QRectF(QPointF(0.0, 0.0), size());
}