I'm working on a feature for VisualWorks called Fluid Positioning. The idea is to simplify the layout of user interfaces in the UI Painter by making the layout automatically fill in the Position tab information in a natural way.
The following video shows what I have working so far. The video below is a bit blurry. A better version can be found on the Simberon Web Site. The demo shows a lot of flickering of the user interface. This is because I've disabled some optimizations at this stage to allow me to see exactly what's going on at all times. When I re-enable the optimizations, most of the flicker should disappear.