[diagrams] diagrams status

[Brent Yorgey]

Hi all,

Here's an update on the current status of the diagrams project.
Obviously things are sort of ground to a halt at the moment.  Partly
that's due to me being busy with my internship at Microsoft Research.
But partly it's because of a giant roadblock in the design of the
project itself.

As you may already know, the main issue is the way our functional
representation of convex bounding regions interacts with certain
transformations.  In particular, we don't know how to correctly
transform convex bounding regions under transformations that don't
preserve angles (which includes shears, non-uniform scales, and pretty
much all projective transformations).  I see three options:

  1) Buckle down and work really hard and figure out how to do it.
     Pros: this would be awesome.  
     Cons: we don't even know if it's possible.

  2) Only allow angle-preserving transformations.  
     Pros: this option is simplest.
     Cons: might be too restrictive.

  3) Switch to a different representation of bounding regions that
     will integrate better with general transformations.
     Pros: ability to do general transformations.
     Cons: probably a lot of work, and the current representation
     seems so elegant and functional, it would be a shame to give it
     up.

I have some opinions, but first I'd like to hear if anyone has any
thoughts on these options (or other options to propose).

-Brent