title: Scale image directly under mouse in Qt 4
body: <p>Similar to google.com/maps, I would like it so that if my mouse is over a QGraphicsItem, then when I move the wheelmouse forward and back, the area of the image under the mouse is what is centered in my QGraphicsView.</p>
  
  <p>Can I accomplish this in the wheelEvent method of the custom QGraphicsIte I have created?</p>
  
  <p>I have some code like this </p>
  
  <pre><code>update();
  qreal factor = 1.2;
  if (event-&gt;delta() &lt; 0)
    factor = 1.0 / factor;
  scale(factor, factor);
  scaleFactor *=factor;
  this-&gt;scene()-&gt;setSceneRect(0,0,this-&gt;boundingRect().width(), this-&gt;boundingRect().height());
  </code></pre>
  
  <p>What can I add to this to give the desired effect? </p>
  
  <p>As an example, in google maps, if you hold your mouse over utah, and keep zooming in with the wheel mouse, eventually Utah is the only thing left in the viewport.</p>