#10 Exploding nodes

[Jens Kanschik]

There is the need to allow the user to expand / shrink
the graph on mouse clicks, similar to the behavious of
(for example) Touchgraph.
The applet has to store the full graph, but only show
parts of it. If the user clicks on a node, the adjacent
nodes from the full graph are added to the visible
graph. Visible nodes which are too far away from the
current node should be removed from the visible graph
so that the number of visible nodes should be roughly
constant.