[Dot] When exactly do multiple splines occur?

[chtenb]

A spline type can have multiple splines, according to http://www.graphviz.org/doc/info/attrs.html#k:splineType

However, I have not been able to find an answer in the documentation to the following question:

When and why will there be multiple splines?

[magneticnorth]

There may be (and often are) multiple sections, in, say a piecewise cubic Bezier spline that has to route around a number of obstacles, or in orthogonal routes that have multiple horizontal and vertical segments. This is very common.

[chtenb]

I've got a situation in which there are multiple subsplines, but they result in two different edges being drawn, which I don't understand and which don't seem to fall under the above explanations.

[Removed example, see below for reproduction scenario.]

[chtenb]

It's hard to create a small reproduction scenario. When I start to remove nodes, these strange splines also start to dissappear. If I remove all clusters, these splines don't seem to occur either.

[chtenb]

I seem to have found a decently small enough reproduction case.

digraph "8285a152-0673-4d53-81f8-1eb06bc9b84f" {
	graph [
		compound=true,
		fontsize=30,
		labelloc=t,
		margin=10,
		newrank=true,
		ranksep=3
	];
	node [color=black,
		shape=point
	];
	edge [arrowhead=none,
		color=black,
	];
	subgraph "rank-213556c6-92a6-4884-8032-ac1ddc2303a3" {
		graph [
			compound=true,
			fontsize=30,
			label="",
			labelloc=t,
			margin=10,
			newrank=true,
			rank=same,
			ranksep=3
		];
		"logical.20:0D:00:2A:6A:D1:10:E8"	;
		"logical.20:0D:8C:60:4F:D7:12:50"	;
		"logical.20:0A:00:2A:6A:D1:10:E8"	;
		"logical.20:0A:8C:60:4F:D7:12:50"	;
	}
	subgraph "cluster_20:01:00:2A:6A:D1:10:E9" {
		graph [
			compound=true,
			fontsize=30,
			label="2001002A6AD110E9",
			labelloc=t,
			margin=10,
			newrank=true,
			ranksep=3
		];
		"logical.20:0D:00:2A:6A:D1:10:E8";
		"logical.20:0A:00:2A:6A:D1:10:E8" [color="red"];
		"logical.20:0D:00:2A:6A:D1:10:E8" -> "logical.20:0A:00:2A:6A:D1:10:E8"	;
	}
	subgraph "cluster_20:01:8C:60:4F:D7:12:51" {
		graph [
			compound=true,
			fontsize=30,
			label="20018C604FD71251",
			labelloc=t,
			margin=10,
			newrank=true,
			ranksep=3
		];
		"logical.20:0D:8C:60:4F:D7:12:50";
		"logical.20:0A:8C:60:4F:D7:12:50";
		"logical.20:0D:8C:60:4F:D7:12:50" -> "logical.20:0A:8C:60:4F:D7:12:50"	;
	}
	"logical.20:0D:00:2A:6A:D1:10:E8" -> "logical.20:0D:8C:60:4F:D7:12:50"	;
	"logical.20:0D:00:2A:6A:D1:10:E8" -> "logical.20:0A:8C:60:4F:D7:12:50"	;
	"logical.20:0D:8C:60:4F:D7:12:50" -> "logical.20:0A:00:2A:6A:D1:10:E8"	;
	"logical.20:0A:00:2A:6A:D1:10:E8" -> "logical.20:0A:8C:60:4F:D7:12:50"	[color="red"];
}

[emden]

This is a duplicate of issue 1223.