Avoiding flickering when dynamically changing content of a widget

[ghorwin]

Marcel (and others who want to see the effect), I attached a short example that illustrates the problem.

Compile, run and then press the buttons 1 and 5 (toggle visibility of a group box) and check/uncheck the advanced box.

You will see in either case a flickering when the layout is redone.

Mind that this is a fairly "lightweight" example of a dialog with about 50 widgets, others have about 150 to 300 widgets. For these cases the layout updating should really be done in the background before the whole thing gets drawn again.

Thanks for any suggestions!
Andreas