Builder Help

I may not get to this for a while, since I’d like to clean up some of
the bugs first (and maybe get a 0.2 release out).

But I was thinking about the design for some “builder” extensions and
wanted to ask for some help about widgets. Both builders are similar
in concept: a new window comes up with the ability to define new
atoms, either by z-matrix or crystal cell coordinates.

For those who don’t know either of these, I’ll quickly explain.
Crystal cell coordinates are in reciprocal space. So the periodic
unit cell for a crystal runs from 0.0 -> 1.0 in the a, b, and c
directions. So the center of the unit cell is (0.5, 0.5, 0.5).

Z-matrix is a way of specifying coordinates based on the distance,
angle, and dihedral angle from other atoms.

What I’d really like to see is a little table, with one row per atom.
For crystal cell, there are 4 columns: atom, a, b, c coordinates.
Then there should be a little “+” button to create a new atom (row).

Can anyone point me to some examples or the class I’d want? I guess
this fits under the MVC idiom, right?