title: QGraphicsScene ignores Stretches of Grid Layout
body: <p>I have a Widget that divides into two subwidgets. One shows a picture, the other one offers options to edit the picture. The picture subwidget should take 5 times the horizontal space than the edit subwidget. I specify this constraint in a Grid Layout. However, the constraint is ignored as soon as I add a QGraphicsScene (and View) to the edit subwidget.</p>
  
  <p>I tried several size policies, but none of them did what I wanted, however I am not too experienced using those.</p>
  
  <pre><code>class MapWidget(QWidget):
  """ Widget that renders the map and displays properties """
      def __init__(self, main_gui, parent=None):
          super().__init__(parent=parent)
          self.main_gui = main_gui
  
          # (Re-)Build the ui
          self.layout = QGridLayout()
          self.setLayout(self.layout)
  
          self.map_scene = QGraphicsScene()
          self.map_scene_view = QGraphicsView()
          self.map_scene_view.setViewport(QGLWidget())
          self.map_scene_view.setScene(self.map_scene)
          self.layout.addWidget(self.map_scene_view, 1, 1, 5, 1)
  
          blocks_container = QVBoxLayout()
          self.layout.addLayout(blocks_container, 1, 2, 1, 1)
  
          """
          Here I add other widgets to the blocks_container, 
          however none of those causes problems
          """
  
          # As soon as I also add this group, both widgets have the same size 
          group_blocks = QGroupBox('Blocks')
          self.blocks_scene = QGraphicsScene()
          self.blocks_scene_view = QGraphicsView()
          self.blocks_scene_view.setViewport(QGLWidget())
          self.blocks_scene_view.setScene(self.blocks_scene)
          group_blocks_layout = QHBoxLayout()
          group_blocks.setLayout(group_blocks_layout)
          group_blocks_layout.addWidget(self.blocks_scene_view)
          blocks_container.addWidget(group_blocks)
  </code></pre>
  
  <p>Instead of having the two widgets with ratios 5/6 and 1/6, both widgets share the same size, which makes the picture look small and the edit widget too big. Also, once I remove the 'group_blocks' widget, the edit subwidget has its proper size again. For simplicity I therefore excluded all the other widgets it contains.</p>