Here's my QGraphicsView code:

Qt Code: 
  1. def wheelEvent(self, event):
  2.         if QApplication.keyboardModifiers() & (Qt.ControlModifier | Qt.ShiftModifier):
  3.             self.setTransformationAnchor(self.AnchorUnderMouse)
  4.             #Scale the view / do the zoom
  5.             scaleFactor = 1.08   
  6.  
  7.             if event.angleDelta().y() > 0:
  8.                 #Zoom in
  9.                 self.scale(scaleFactor, scaleFactor)
  10.             else:
  11.                 self.scale(1.0/scaleFactor, 1.0/scaleFactor)
  12.  
  13.     #Assumes scaleX = scaleY
  14.     def scale(self, scaleX, scaleY):
  15.         self.scene().viewScale(scaleX)
  16.         QGraphicsView.scale(self, scaleX, scaleY)
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viewScale() of scene() in turn calls viewScale of SnapGridGraphicsItem:

Qt Code: 
  1. def viewScale(self, scale):
  2.         #self.pen.setWidth(1.0 / scale)
  3.         self.pen = QPen(self.color, 1.0 / scale)
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I've also tried multiplying 1.0 / scale x pen.width() and the same result happens: nothing - lines are still scaled with zoom action. Please help! :|

I also already have ItemIgnoresGeometricTransformations enabled for SnapGridGraphicsItem...