This is not directly related to my question but to the usage of your gvpr file.
When I try to add any parameter using the -a option, I always get an empty output and a “gvpr: gvpr” message:
$ dot input.dot | gvpr -a 'size=rank' -cf addGrid.gvpr
// SIZE start: 72pt delta: 0
// SIZE end: 72pt size: 72 delta: 0
// ARG >size=rank<
// type: s
gvpr: gvpr
I can move this subthread to the “Add a grid to your graphs”