https://github.com/WillAdams/gcodepreview
which I hope to then wrap up in a nice front-end using:
https://github.com/derkork/openscad-graph-editor
(or maybe some other tool --- is there a stand-alone, desktop version of Blockly which is extensible?)
Hopefully I'll also figure out how to write up a LaTeX package for the Literate Programming technique used and maybe a _TUGboat_ article.