title: Weird result from pyqt example: an image viewer
body: <p>I'm a beginner of PyQt, and I'm reading some examples in tutorials.</p>
  
  <p>When I build an image viewer from example, I find the result is weird.</p>
  
  <p><a href="https://github.com/Werkov/PyQt4/blob/master/examples/widgets/imageviewer.py" rel="nofollow noreferrer">https://github.com/Werkov/PyQt4/blob/master/examples/widgets/imageviewer.py</a></p>
  
  <p>Why there is a blank area on the top left of main window? How can I remove it?</p>
  
  <p><img src="https://i.stack.imgur.com/ulyIA.png" alt="enter image description here"></p>