[Extgraph-developer] Changes I've made (Was Improved drawing zoomed canvas)

[Phil S. <p.s...@gn...>]

> It will be interesting for us to know, which extensions you have made, not
> only for inspiration. Maybe they can be useful also for other users. 

Okay. My application is drawing thermodynamic schematic of a power plant,
which can be reduced to components linked in a planar graph (more or
less). To this end, I have extended graphlink and nodes with the huge no.
of properties required to characterize them. Obviously of no interest to
anyway else. Likewise I have add many different node types to cover the
standard symbols for pump, turbine etc. These have to be custom rather
than graphic because there are conventions concerning where a link may
join them. I did briefly consider generalising this. This would require a 
node to have a property listing allowed link points. Even more complicated
though for my application because entering link points are different from
exiting link points.

Of more general use is jointed link, but I confess that I hacked this by 
simply adding a midpoint property to link. When link is made, it calculates 
to the midpoint, but allows the moving of this node to anywhere so link can
do strong right-angle bends. Bezier links that I see are added address the
same problem more generally, but again, I have convention to follow. The
implementation changes a lot of core code

Finally I added export to couple of plane-graph representations. This is so 
I can feed a schematic into plane-graph optimiser program, get new node
positions and then read back. This is utter hack, never intended to be more
than a one-off exercise but is potentially a useful kind of extension.

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Phil Scadden, Institute of Geological and Nuclear Sciences
764 Cumberland St, Private Bag 1930, Dunedin, New Zealand
Ph +64 3 4799663, fax +64 3 477 5232