Block Diagram / digraph Editor

[MakaMaka]

Hi,
Does anybody know of a good widget for wxpython, gtk, etc. that allows
the editing of block diagrams and make it easy to export the diagram as
a digraph?  It has to be available under Windows.  I want the user to
draw a series of blocks on a canvas, connect them with directional
arrows, and then a function will extract the digraph this represents
and do some graph traversal algorithms on it.  Think DIA or VISIO w/
only a few blocks and connectors available.  Any ideas?  I'd rather not
build my own w/ OGL....


thanks,
-Justin