Qt: How to force a hidden widget to calculate its layout?

Question

What I am trying to do is render a qwidget onto a different window (manually using a QPainter)

I have a QWidget (w) with a layout and a bunch of child controls. w i

Answer 1

I had some succes in a similar problem by first calling w->layout()->update() before w->layout()->activate(). That seems to force the activate() to actually do something rather than think it is fine because the window isn't being shown anyway.