title: How to force render underlying widget in QStackedLayout
body: <p>I have a widget with some data. Every time the data is reloaded (which happens quite often) it takes some time to repaint the widget that leads to noticeable flickering. So I'm trying to implement some sort of double buffering. Instead of one widget I'm using two widgets in a QStackedLayout (the stacking mode is set to StackAll). So I can load the data into the non visible widget and switch to it when the repainting is finished. The problem is that paintEvent() is never called in the underlying widget because it is completely obscured by the visible widget, even if I manually call update() or repaint().
  Is there any way to force repaint the widget if it's completely overlapped by another widget?</p>