Is there a reason you don't just use a JGoSubGraph instead of the example BoxArea?
1) I need roundrect-dashed-border as BoxArea has.
2) JGoSubGraph.setLocation() throws Exception and computes self bounds from bounds of child objects. In my case group object can exist without inner nodes with its own location.
I haven't tried this, but you should be able to adopt the BoxView class to apply to JGoSubGraphs instead of to BoxAreas, if that is behavior you are looking for.
Yes, I'm looking for exactly so behavior
but JGoSubGraph stretches when inner object moves off subgraph bounds. Is it possible to move off a node from JGoSubgraph?