title: Qt modify PathItem
body: <p>is there a way to modify the path of QGraphicsPathItem in Qt?</p>
  
  <p>I created the Item this way:</p>
  
  <pre><code>    QGraphicsPathItem* item = new QGraphicsPathItem();
      QPainterPath* path = new QPainterPath();
      path-&gt;cubicTo(3,5, 3,10, 0,15);
      item-&gt;setPath(*path);
      item-&gt;moveBy(-20,-20);
      scene-&gt;addItem(item);
  </code></pre>
  
  <p>now i want to modify the elements of the path:</p>
  
  <pre><code>    item-&gt;path().elementAt(0).y = -5;
      item-&gt;path().elementAt(0).x =  0;
  </code></pre>
  
  <p>but i get following error:</p>
  
  <pre><code>assignment of member 'QPainterPath::Element::y' in read-only object
  </code></pre>