title: PyQt: properties via stylesheet only for painting?
body: <p>I would like to use within PyQt5 a <code>style sheet</code> to layout custom widgets. Generally this works: the widgets are displayed with the modified properties. However the property of the widget (e.g. <code>style-sheet font-family</code> vs. <code>QLabel.label()</code>) seems to stay the default value (s. minimal example below).</p>
  
  <p>Is the style sheet only used for painting the widget and does not change the widget itself?
  Is there a way to get the 'new' properties? Otherwise using for example <code>FontMetrics</code> in combination with a <code>style sheet</code> is not possible?</p>
  
  <pre><code>import sys
  
  from PyQt5.QtWidgets import QApplication, QLabel
  from PyQt5.QtGui import QFontInfo
  
  stylesheet = '''
  QLabel{
      font-family: Wingdings;
  }
  '''
  
  app = QApplication(sys.argv)
  label = QLabel('Hello World!')
  label.setStyleSheet(stylesheet)
  print(QFontInfo(label.font()).family())  # prints out: MS Shell Dlg 2; expected: Wingdings
  label.show()
  app.exec()
  </code></pre>