[R-gui] After resizing a tkwidget, how do I get the size of the widget??

[Søren Højsgaard]

Dear all,
I am trying make a small tcltk thing for drawing graphs with vertices, edges etc. I can draw the graph in a window. 
 
- I would like it so that if I resize the window, the graph will also be resized. To do this, I guess I need the size of the window, so that I can calculate the new coordinates. 
- I would also like to be able to save the graph as e.g. a jpg/ps file.
Can anyone help on this? 
 
I find the documentation of the tcltk package difficult to comprehend so I have used the examples on http://bioinf.wehi.edu.au/~wettenhall/RTclTkExamples/. Can anyone point me to other sources of examples/doc of the tcltk package?
Thanks in advance
Søren