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

[Marco W. <in...@ca...>]

Response below....

Phil Scadden wrote:

>>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.
>  
>
I've got similar requirements. However I use a information repository in 
a database. Once a node is placed onto the diagram it links up other 
nodes itself depending on the information in the database.

>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.
>  
>
Using undirected graph engines is what I've been using. Similar things 
as you describe here. Perhaps we should allow an export to such a 
format. Are you using publicly available engines or some custom build ones?

Marco.