headport and tailport functionality not working in graphviz

Question

The documentation for "headport" and "tailport" says that it Indicates where on the head/tail node to attach the head/tail of the edge. In the default case, the edge is aimed towards the center of the node, and then clipped at the node boundary. The code given below -

digraph G {
  graph [ rankdir =LR ];
  "struct1" [ shape =record, label = "a|b|<port1>c" ];
  "struct2" [ shape =record, label = "a|{<port2>b1|b2}|c" ];
  "struct1" -> "struct2" [ headport = "port1", tailport = "port2" ];
}

should generate an edge from node:struct1 port "c" to node:struct2 port "b1" like this(left) -

however it generates an edge like this(right),using default behavior. I understand that struct1:port1 -> struct2:port2 [ label="xyz" ]; can be used for the purpose ,but I don't know how to use addEdge method to generate such a dot string (open to suggestions ).

The code used to generate the above dot format representation is below -

var util = require('util'),
  graphviz = require('graphviz');

var g = graphviz.digraph("G");
g.set("rankdir","LR")

var n1 = g.addNode( "struct1", {"shape":"record","label":"a|b|<port1>c"} );
var n2 = g.addNode( "struct2", {"shape":"record","label":"a|{<port2>b1|b2}|c"} );
g.addEdge(n1,n2,{"headport":"port1","tailport":"port2"});

console.log( g.to_dot() );

I request the community to please help me generate an edge like in image 1. I have also tried other versions of port attribute argument such as such , "c","port0:c" etc yet no use.

Answer 1

The documentation is a bit fuzzy, but you are misusing headport/tailport. headport/tailport should be compass points. Here is a correct example:

tailport=ne headport=s

Here is a fix to the code, using fieldid - (port not needed here):

digraph G {
  graph [ rankdir =LR ];
  "struct1" [ shape =record, label = "a|b|<port1>c" ];
  "struct2" [ shape =record, label = "a|{<port2>b1|b2}|c" ];
  struct1:port1 -> struct2:port2 
}