GraphZoomScrollPane scrolling problem

I'm working with the Jung Framework and got some issues:

I'm painting a graph into a GraphZoomScrollPane.

I remark that it doesn't scroll enough to get all the graph.

When I add vertices while the开发者_Python百科 window is maximized they don't appear when the window is in a litte size.

Could anyone help me out please? Is this a bug with the Jung API?