I now have a simple three part RCP skeleton. I decided the extend the application model by adding drag and drop to the parts using the DnDAddon and CleanupAddon addons. Sure enough, just adding these to the model gives the new functionality.
My problem is having run up the application and dragged the parts to give a new layout, on restarting the application I often get IllegalArgumentException with the message:
"part ... is not a child of this container"
Even with the exception, sometimes the new layout is restored OK. Other times I loose one or more of the parts.
Is this a bug or do I need to add some additional functionality to support DND?