How does QTransform.squareToQuad work?
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I want to make a slight perspective warping. I thought I could do this:

    t = QPolygonF(
           QPointF(0.2,0.2),
           QPointF(0.8,0.2),
           QPointF(1,1),
           QPointF(0,1))

    view.setTransform(QTransform.squareToQuad(t))

but that gives me a bizarrely warped view. I just want a simple trapezoid.
If I do the same thing using quadToquad, it seems to work. What's the right way to do this?