Hello MetaFun Math Lovers,

I am using MetaFun to attach diagrams to formulas. Both the physics and the typesetting are going great! I attached a sample below, to give a taste of what I am trying to do. This page of actual calculations has examples of almost everything I need. It’s a lot, but it is all working. Right now the interface is terrible, but effective. Thanks to Hans and Mikael for many helpful hints!

I am still using \hpos and \setMPpositiongraphic, because I haven't figured out how to pass information from \mathboxanchored and \connectboxanchors to my MetaPost code. Here is the code for the connectors:

\startMPpositiongraphic{mypos:contract}
  path pa, pb, pab ; numeric na, nb ; string ta, tb, hand, product ;
  ta := mpvars("from") ;
  tb := mpvars("to") ;
  stemshiftfrom := (EmWidth/8)*mpvarn("startstem") ;
  stemshiftto   := (EmWidth/8)*mpvarn("stopstem") ;
  hand := mpvars("hand") ;
  product := mpvars("product") ;
  delta := mpvard("distance") ;
  na := positionpage(ta) ; % page number of a
  nb := positionpage(tb) ; % page number of b
  pa := positionbox(ta) ;  % box of a
  pb := positionbox(tb) ;  % box of b
  if hand = "right" :
     z1 = 0.5[llcorner pa,lrcorner pa] shifted (stemshiftfrom, -ExHeight/4) ;
     z2 = 0.5[llcorner pb,lrcorner pb] shifted (stemshiftto,   -ExHeight/4) ;
     y3 = min(y1,y2) - ExHeight/2 -delta; 
  else :
    z1 = 0.5[ulcorner pa,urcorner pa] shifted (stemshiftfrom,  ExHeight/4) ;
    z2 = 0.5[ulcorner pb,urcorner pb] shifted (stemshiftto,    ExHeight/4) ;
    y3 = max(y1,y2) + ExHeight/2 +delta; 
  fi ;
  if na = nb : % Check that positions are on the same page
    pickup pencircle scaled 0.6pt ;
    if product = "sym" :
      draw z1 -- (x1,y3+ExHeight/2) ;
      draw z2 -- (x2,y3+ExHeight/2) ;
      pickup pencircle scaled 1.2pt ;
      draw (x1-EmWidth/8,y3) -- (x2+EmWidth/8,y3) ;
    else :
      pab := z1 -- (x1,y3) -- (x2,y3) -- z2{down} ;
      draw pab ;
    fi ;
    positioninregion ;
  fi ;
\stopMPpositiongraphic

A connector command might look something like this:

\setMPpositiongraphic{X-1}{mypos:contract}{to=X-2,product=sym,startstem=-2,stopstem=2,distance=0.5ex}

All of the key=value pairs in the last argument of \setMPpositiongraphic pop right up in my MetaPost code with mpvar(“key”). I haven’t been able to follow this with \mathboxanchored and \connectboxanchors. My two questions are:

1) Can I use \setMPpositiongraphic with \mathboxanchored? That would allow me to go straight to my MetaPost code without the \connectboxanchors interface

2) Can I tell \connectboxanchors to use my MetaPost code and pass key=value pairs like I do with \setMPpositiongraphic?

Thanks for any hints!
Gavin