title: Why is it more efficient to remove a QGraphicsItem from its scene before destroying it?
body: <p>According to the <a href="http://qt-project.org/doc/qt-4.8/qgraphicsitem.html#dtor.QGraphicsItem">QGraphicsItem destructor documentation</a>, "It is more efficient to remove the item from the QGraphicsScene before destroying the item."</p>
  
  <p>Why is that? I can't think of how it could make a difference. And if it did make a difference, shouldn't the QGraphicsItem destructor just call:</p>
  
  <pre><code>if (scene() != NULL)
      scene()-&gt;removeItem(this);
  </code></pre>
  
  <p>I checked the source, and this does not seem to be the case, although sometimes I have a tough time understanding Qt source. <strong>EDIT</strong>: See comments in jdi's answer.</p>