title: Painting background on QGraphicsView using drawBackground
body: <p>I have a problem trying to paint and draw on <code>QGraphicsView/Scene</code>. I'm drawing a bunch of <code>QLineF as background overriding</code>QGraphicsView::drawBackGround`. However, when I try to change the background color nothing happens.</p>
  
  <p>Here is minimal example of what I'm doing:</p>
  
  <pre><code>import sys
  import platform
  import ctypes
  from PySide import QtCore, QtGui
  from mygv import Ui_Dialog
  import sys
  
  class myView(QtGui.QDialog):
      def __init__(self, parent = None):
          QtGui.QDialog.__init__(self, parent)
          self.ui = Ui_Dialog()
          self.ui.setupUi(self)
          self.ui.view.drawBackground = self.drawBackground
          self.ui.view.wheelEvent = self.wheelEvent
          self.scene = QtGui.QGraphicsScene()
          self.ui.view.setScene(self.scene)
          self.scene.addEllipse(0,0,100,100)
  
      def drawBackground(self, painter, rect):
  
          bbrush = QtGui.QBrush( QtGui.QColor(255,170,255), QtCore.Qt.SolidPattern)
          painter.setBackgroundMode(QtCore.Qt.OpaqueMode)
  
          pen = QtGui.QPen(QtGui.QColor(46, 84, 255))
          pen.setWidth(5)
          painter.setPen(pen)
  
          line1 = QtCore.QLineF(0,0,0,100)
          line2 = QtCore.QLineF(0,100,100,100)
          line3 = QtCore.QLineF(100,100,100,0)
          line4 = QtCore.QLineF(100,0,0,0)
          painter.setBackground(bbrush)
          painter.drawLines([line1, line2, line3, line4])
  
  
  
  
      def wheelEvent(self,event):
          factor = 1.41 ** (event.delta() / 240.0)
          self.ui.view.scale(factor, factor)
  
  if __name__ == '__main__':
      app = QtGui.QApplication(sys.argv)
      diag = myView()
      diag.show()
      diag.ui.view.centerOn(50,50)
      app.exec_()
  </code></pre>
  
  <p>Ui_dialog is just a standard dialog generated from QDesigner with a QGraphicsView member named "view". </p>
  
  <p>This just an example of the problem. I need to be able to change the color of the background systematically during the execution of my app.</p>
  
  <p>What am I missing or doing (clearly) wrong?</p>