Graph the CSP problem

[jgraley]

Following on from #280, #281

For a CSP problem (i.e. an and-rule region), show

• Variables lined up in a row (they are ordered)
  • Show them much the way agents are shown at the moment, but
  • don't link them, just line them up, but
  • do show the link satellite serial # somewhere TBD
  • Bold edge for forced variables?
• Constraints will be above and below as required to minimise crossings
  • They should appear as some new kind of graph node
  • There should be edges to involved variables,
  • and not be directed in any way
  • and they can be labelled as dictated by the constraint not the variable (for which all links are the same)
• SystemicConstraint should have short and fat line to the variable for its base agent.
• MM constraints need to label links with MMvar names and then show the expression in math script

Note that we choose not to use the form in which edges show constraints, because we'll always have degree>2 constraints. And constraints as Venn-diagram sets with variables as points is problematic because drawing Venn diagrams is tricky in general (or so the Internet says).

[jgraley]

Is this still for dot, or do we want eg neato?

Should some shapes be taken away from the existing plotter eg circles, to be used for constraints? Maybe one shape for each category discussed here https://github.com/jgraley/inferno-cpp2v/issues/278#issuecomment-768855766

[jgraley]

More thoughts on this: I think the constraints should inherit the look of the nodes in the current graphs, and their links should come from ports/sub-blocks as at present. The variables should be small circles with just class name and serial #. The variables should be lined up vertically and the constraints be to their left so the links work properly. MM constraints TBD but they will also need ordered links, so record-type blocks might also be indicated.