How can I control within level node order in graphviz's dot?

Question

I have a graph that has a tree as its backbone. So I have, for example a node A with children B, C, and D. Assuming the graph is being drawn top-down, A will be on one level, then B, C, and D. I would like to force graphviz to lay them out in B, C, D order within their rank. Is this possible? If so, how?

If there are only A, B, C, and D, I can get this effect by just putting B, C, and D in that order in the input dot file. But if there are other edges out of B, C, and/or D, sometimes the order gets scrambled. That's what I would like to avoid.

Answer 1

This can be achieved with "invisible" edges as shown. Please note well the comments that describe how it works.

digraph test{

// make invisible ranks
rank1 [style=invisible];
rank2 [style=invisible];

// make "invisible" (white) link between them
rank1 -> rank2 [color=white];

// declare nodes all out of desired order
A -> D;
A -> B;
A -> C;
A -> E;

// even these new connection don't mess up the order
B -> F -> G;
C -> F -> G;

{
rank = same;
// Here you enforce the desired order with "invisible" edges and arrowheads
rank2 -> B -> C -> D -> E [ style=invis ];
rankdir = LR;
}
}