[BioC] parameters in graph.par in Rgraphviz

[Paolo Innocenti]

Is there a way to change the shape of nodes using the new rendering 
interface in Rgraphviz?
"$nodes$shape" appears in the graph.par() list, but changing the default 
value (circle) doesn't affect the output.
No surprise, since the vignette doesn't include "shape" in the list of 
node parameters currently available, but I was wondering if there is a 
dirty shortcut to avoid this problem (using layoutGraph and renderGraph 
though).

More generally, I need ellipses because my labels are realllly long, and 
therefore the whole graph is short and wide, and the fontsize results 
too small...

Thanks,
paolo