FDP subgraphs nodes link to external node

[MadaManu]

Example:

HOST_NETWORK_NODE = node("HOST")
                .with(Color.PERU, Size.mode(Size.Mode.FIXED).size(10, 1))
                .with(Shape.RECTANGLE)
        Graph g = graph("all")
                .graphAttr().with(splines(GraphAttr.SplineMode.POLYLINE))
                .with(
                        graph()
                                .directed()
                                .cluster().named("hostname")
                                .graphAttr().with(Label.of("hostname"))
                                .with(HOST_NETWORK_NODE)
                                .with(graph("subGraph1")
                                        .cluster().named("subGraph1")
                                        .graphAttr().with(Rank.dir(LEFT_TO_RIGHT))
                                        .graphAttr().with(Style.FILLED, Color.LIGHTGREY, Label.of("subGraph1"))
                                        .with(node("a")
                                                .link(to(HOST_NETWORK_NODE).with(Label.of("link1"))))
                                        .with(node("b"))
                                )
                                .with(graph("subGraph2")
                                        .cluster().named("subGraph2")
                                        .graphAttr().with(Rank.dir(LEFT_TO_RIGHT))
                                        .graphAttr().with(Style.FILLED, Color.LIGHTGREY, Label.of("subGraph2"))
                                        .with(node("c")
                                                .link(to(HOST_NETWORK_NODE).with(Label.of("link2"))))
                                        .with(node("d"))
                                )
                )

        Graphviz.fromGraph(g).engine(Engine.FDP).totalMemory(100_000_000).render(Format.DOT).toFile(new File("out/FDP.txt"))

        Graphviz.fromGraph(g).engine(Engine.FDP).totalMemory(100_000_000).render(Format.PNG).toFile(new File("out/image.png"))

ERROR in rendering PNG:

Exception in thread "main" guru.nidi.graphviz.engine.GraphvizException: Error: node "HOST" is contained in two non-comparable clusters "cluster_subGraph2" and "cluster_subGraph1"

Text file generated:

digraph "all" {
edge ["dir"="none"]
graph ["splines"="polyline"]
subgraph "cluster_hostname" {
edge ["dir"="forward"]
graph ["label"="hostname"]
"HOST" ["color"="peru","fixedsize"="true","width"="10.0","height"="1.0","shape"="rectangle"]
subgraph "cluster_subGraph1" {
edge ["dir"="none"]
graph ["rankdir"="LR","style"="filled","color"="lightgrey","label"="subGraph1"]
"HOST" ["color"="peru","fixedsize"="true","width"="10.0","height"="1.0","shape"="rectangle"]
"b"
"a" -> "HOST" ["label"="link1"]
}
subgraph "cluster_subGraph2" {
edge ["dir"="none"]
graph ["rankdir"="LR","style"="filled","color"="lightgrey","label"="subGraph2"]
"HOST" ["color"="peru","fixedsize"="true","width"="10.0","height"="1.0","shape"="rectangle"]
"d"
"c" -> "HOST" ["label"="link2"]
}
}
}

However, the expected generation for the expected outcome I am looking for would be:

Note the HOST node definition only once, compared to generated one where this node is defined in each subgraph. Also, note the links in the generated file are defined in each subgraph where the expected would be defined outside.

digraph "all" {
edge ["dir"="none"]
graph ["splines"="polyline"]
subgraph "cluster_hostname" {
edge ["dir"="forward"]
graph ["label"="hostname"]
"HOST" ["color"="peru","fixedsize"="true","width"="10.0","height"="1.0","shape"="rectangle"]
subgraph "cluster_subGraph1" {
edge ["dir"="none"]
graph ["rankdir"="LR","style"="filled","color"="lightgrey","label"="subGraph1"]
"b"
"a"
}
subgraph "cluster_subGraph2" {
edge ["dir"="none"]
graph ["rankdir"="LR","style"="filled","color"="lightgrey","label"="subGraph2"]
"d"
"c"
}
"a" -> "HOST" ["label"="link1"]
"c" -> "HOST" ["label"="link2"]
}
}

GraphvizOnline of expected

Image of expected (note the link between inner nodes of a subgraph to the HOST node.

Same result using both 0.18.0 and 0.18.1.

Is there something that I'm missing in my code? How can I achieve the described expected outcome?

[nidi3]

You should add the a->HOST and c->HOST links outside of the clusers, the same as in DOT:

        Graph g = graph("all")
                .graphAttr().with(splines(GraphAttr.SplineMode.POLYLINE))
                .with(
                        graph()
                                .directed()
                                .cluster().named("hostname")
                                .graphAttr().with(Label.of("hostname"))
                                .with(HOST_NETWORK_NODE)
                                .with(graph("subGraph1")
                                        .cluster().named("subGraph1")
                                        .graphAttr().with(Rank.dir(LEFT_TO_RIGHT))
                                        .graphAttr().with(Style.FILLED, Color.LIGHTGREY, Label.of("subGraph1"))
                                        .with(node("b"))
                                        .with(node("a"))
                                )
                                .with(graph("subGraph2")
                                        .cluster().named("subGraph2")
                                        .graphAttr().with(Rank.dir(LEFT_TO_RIGHT))
                                        .graphAttr().with(Style.FILLED, Color.LIGHTGREY, Label.of("subGraph2"))
                                        .with(node("c"))
                                        .with(node("d"))
                                )
                                .with(node("a")
                                        .link(to(HOST_NETWORK_NODE).with(Label.of("link1"))))
                                .with(node("c")
                                        .link(to(HOST_NETWORK_NODE).with(Label.of("link2"))))
                );

[nidi3]

Unfortunately, with the JS engines, the resulting layout is not the same as with native dot. I don't know why.

[MadaManu]

That indeed solved my issue. Thank you @nidi3

[nidi3]

Good to hear. @MadaManu So you use native dot engine and don't have an issue with the layout?

[MadaManu]

No issue with the layout. Works fine using both DOT and FDP engines.