How to drag the subtree the visualGraph to an area to generate a new topology graph

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Now I am using the ravis library to display a topology graph. My project 
required me to implements a function that allows user to drag part of the graph 
to the 
other area and creating a new graph. Is there any thing like the "dragEnable" 
attribute allows me to drag subtree and copy it to the other container to create
an new graph?

Original issue reported on code.google.com by xiaoyazh...@gmail.com on 16 May 2011 at 8:59