'Return the region which has been requested to be visible.
(this is not necessarily the same as the region that is *actually* visible--
resizing and aspect ratio constraints can cause targetRect() and viewRect() to differ)'

def targetRect(self):

    try:
        tr0 = self.state['targetRange'][0]
        tr1 = self.state['targetRange'][1]
        return QtCore.QRectF(tr0[0], tr1[0], (tr0[1] - tr0[0]), (tr1[1] - tr1[0]))
    except:
        print ('make    qrectf    failed:', self.state['targetRange'])
        raise
