'Return a QRectF bounding the region visible within the ViewBox'

def viewRect(self):

    try:
        vr0 = self.state['viewRange'][0]
        vr1 = self.state['viewRange'][1]
        return QtCore.QRectF(vr0[0], vr1[0], (vr0[1] - vr0[0]), (vr1[1] - vr1[0]))
    except:
        print ('make    qrectf    failed:', self.state['viewRange'])
        raise
