Can a node point to a cluster without involving that cluster own nodes?

Help
1

I am considering moving from mermaid.js to graphviz but one point is still blocking me: the ability for a node to point to a cluster.

Taking the typical example everyone shows (the version, modified with my attempts is online), I tried to point the node a3 to the cluster cluster_1:

digraph G {
    compount=true;

  subgraph cluster_0 {
    style=filled;
    color=lightgrey;
    node [style=filled,color=white];
    a0 -> a1 -> a2 -> a3;
    label = "process #1";
  }

  subgraph cluster_1 {
    node [style=filled];
    b0 -> b1 -> b2 -> b3;
    label = "process #2";
    color=blue
  }
  start -> a0;
  start -> b0;
  a1 -> b3;
  b2 -> a3;
  a3 -> cluster_1;
  a3 -> end;
  b3 -> end;

  start [shape=Mdiamond];
  end [shape=Msquare];
}

The result is

image

cluster_1 is perceived in that context as a new node instead of the cluster labeled process #2.

Is there a way to have a node point to a cluster, without having it point to a node in that cluster? The emphasized part is important because I just know that a node points to a cluster, (and not a node in that cluster).

In other words, I cannot do, for instance,

a3 -> b0 [lhead=cluster_1];

(because that requires me to know that b0 is part of cluster_1)

2

A post was merged into an existing topic: About the Help category

4

I don’t know if the dot layout engine supports edges to/from clusters, but fdp does. See this example.

5

Short answer: no

Medium answer:
Only fdp supports clusters as head and/or tail of an edge (though this feature was recently broken - see fdp cluster->cluster edges were correct but now drawn incorrectly (#2345) · Issues · graphviz / graphviz · GitLab)

Long answer & (lightly tested) work-around

Below is a (very lightly tested) gvpr (part of the Graphviz bundle) (see http://www.graphviz.org/pdf/gvpr.1.pdf) program that will take an input file containing edges with clusters as head and/or tail and produce a modified result, suitable for input into dot, with compound=true and each cluster-involved edge recreated as an edge to/from one of the nodes contained within the cluster.

The gvpr program:

BEGIN{
  graph_t aGraph, Root, Parent[];
  node_t  aNode, newH, newT, theKid[], kid[];
  edge_t  newE, anEdge;
  int     i, K, clust[], Clust[], rankCnt[], maxRnk[], deleteE[], deleteN[];

  graph_t graphTraverse(graph_t thisG){
    for (aGraph = fstsubg(thisG); aGraph; aGraph = nxtsubg(aGraph)) {
      //print ("//  graph:  >", aGraph.name,"<");
      if (match(aGraph.name,"cluster")==0 || (hasAttr(aGraph, "cluster") && aGraph.cluster=="true")){
        clust[aGraph.name]=1;  // ?????
        Clust[aGraph]=1;
        print ("// CLUSTER ",aGraph.name);
	K=0;
        for (aNode=fstnode(aGraph);aNode;aNode = nxtnode_sg(aGraph, aNode)){
          Parent[aNode]=aGraph;
	  kid[++K]=aNode;
        }
	i=(int)(K/2);  // or we could randomize??
	theKid[aGraph]=kid[i];
      }
      aGraph = graphTraverse(aGraph);
    }
    return thisG;
  }  // end of graphTraverse
}
BEG_G {
  Root=$G;
  graphTraverse ($G);
}
E{
  print("// ", $.name);
  if (clust[$.head.name]==0 && clust[$.tail.name]==0) continue;
  newH=$.head;
  newT=$.tail;
  if (clust[$.head.name]==1){
    print ("// BINGO - head ",$.head.name);
    $G.compound="true";
    deleteE[$]=1;
    newH=theKid[$.head];
  }
  if (clust[$.tail.name]==1){
    print ("// BINGO - tail ",$.tail.name);
    $G.compound="true";
    deleteE[$]=1;
    newT=theKid[$.tail];
  }
  print("// NEW: ", newT.name, "  ", newH.name);
  newE=edge(newT, newH,"");
  copyA($, newE);
  if (newT != $.tail){
    newE.ltail=$.tail.name;
    deleteN[$.tail]=1;
  }
  if (newH != $.head){
    newE.lhead=$.head.name;
    deleteN[$.head]=1;
  }
  //delete($G, $);
}
END_G{
  for (deleteE[anEdge]) delete(Root, anEdge);
  for (deleteN[aNode])  delete(Root, aNode);  
}

The (Linux) commandline (Windows should be similar?):
gvpr -cf clusterCluster.gvpr myFile.gv | dot -Tpng >myFile.png
Giving:

clusterCluster0
clusterCluster0323×543 26.6 KB