adding geom_edge_parallel (#44)

[schochastics]

Fixes #44

I have tried to understand cappedPath.R and the makeContent thing, but I have to admit that this is above my pay grade.

So this is the geom version that draws parallel edges "one level to high".
parallel edges are calculated in create_parallels(). The function edge_shift() spreads edges evenly so that the distance between edges is always the same, no matter how many multi edges exist.

The function creates a warning about unknown from and to parameters. I had to add them to
aes_intersect (line 128) to identify the multi edges but couldn't figure out how to revert back again.

The other code is a straightforward adoption of geom_edge_link()

I did not implement geom_edge_parallel0() and geom_edge_parallel2().

Hope this helps you in any way. Just decline if not.

[thomasp85]

Thank you — I’ll have a go with this once I’m done with the BioFabric layout

[thomasp85]

If you want you can look through the changes to see what it took - I admit it was a bit hairy :-)

[schochastics]

yep as I expected. Way beyond my skills. Thanks for considering my code. I learned a thing or two in the process :-)