title: QGraphicsView/QGraphicsScene rendering question
body: <p>I am using QGraphicsScene/QGraphicsView pair in my application.
  I had subclassed them for my purpose. The code snippet that generate the pair is below:</p>
  
  <pre><code>itsScene = new QGraphicsScene;
  itsView = new QGraphicsView;
  itsView-&gt;setParent(itsCanvas);
  
  itsView-&gt;setGeometry(20,20,1700,720);
  itsView-&gt;setBackgroundBrush(Qt::black);
  itsView-&gt;setAlignment(Qt::AlignTop);
  itsView-&gt;setScene(itsScene);
  </code></pre>
  
  <p>After adding some widgets into QGraphicsScene my application final UI snapshot is below:
  <a href="https://i.stack.imgur.com/1VqXT.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1VqXT.jpg" alt="Application UI snapshot"></a>
  
  Here my question is why there is some free space above the picture? What may cause this?
  I am using some negative coordinates for my widgets. Is it related with that?</p>