Graphviz ignore edge when deciding layout

Question

I have an edge in a dot graph that I need to be ignored by other edges during the layout. I have tried feeding the first part of the code through dot and then adding dotted edges below, however the other solid edges still keep being affected by them.

The code:

digraph structs {
    rankdir=LR
    edge [tailclip=false];
    node [shape=record];
    header [label="{<0> |<1> header|<2>  }"];
    data0 [label="{<0> |<1> data0|<2> }"];
    data1 [label="{<0> |<1> data1|<2> }"];
    trailer [label="{<0> |<1> trailer|<2> }"];

    header -> data0 -> data1 -> trailer [style=invis, weight=100];
    edge [arrowhead=vee, arrowtail=dot, dir=both, weight=40];
    header:2:c -> data0:1:n;
    data0:0:c -> header:1:s;


    data0:2:c -> data1:1:n;
    data1:0:c -> data0:1:s;

    data1:2:c -> trailer:1:n ;
    trailer:0:c -> data1:1:s;

    edge [constraint=false, style=dashed, weight=0, layer=1];
    data0:2:c -> trailer:1:n [weight=0];
    trailer:0:c -> data0:1:s [weight=0];

}

The results:

Nitrile

I don't understand what you mean by your question. Can you give an explanation of what goes wrong (maybe also an image of the situation "before" and the wanted situation). – Paulino

This is exactly my question. I want to draw certain edges while the layout algorithm should ignore them when positioning the nodes. I know dot can do this but I don't know how to look it up in the documentation. – Hedgepeth

Answer 1

If constraint=false is inadequate, then

• run dot -Tdot ... >myfile.dot without the "ignore me" edges
• using a text editor, add the "ignore me" edges to myfile.dot (pretty much anywhere before the last brace)

• run neato -n2 -Tpng myfile.dot >myfile.png. neato -n2 will honor (keep) all of dot's positioning, but will do layout for the added edges. (see https://www.graphviz.org/faq/#FaqDotWithCoords)

Prunella