# Forcefully draw edges on top of each other **URL:** \ **Category:** Uncategorized\ **Created:** [July 20, 2020, 1:21pm UTC](https://forum.graphviz.org/t/forcefully-draw-edges-on-top-of-each-other/266 "2020-07-20T13:21:46Z")\ **Posts on this page:** 5\ **Page:** 1

**Author:** ![snowmb](https://avatars.discourse-cdn.com/v4/letter/s/a183cd/32.png) [@snowmb](https://forum.graphviz.org/u/snowmb)\ **Post date:** [July 20, 2020, 1:21pm UTC](https://forum.graphviz.org/t/forcefully-draw-edges-on-top-of-each-other/266/1 "2020-07-20T13:21:46Z")

Hello, I came to working with graphviz over a tool called [wireviz](https://github.com/formatc1702/WireViz). The author uses graphviz to visualize cable connections and wire colors. To make the resulting graph visually appealing he uses 2 colors (black, wire color, black) on edges. In reality there might also be 2 colored wires which now is solved by using 5 colors on a single edge (black, color1, color2, color1, black). I would prefer to get a banded look on 2 colored wires, which can be achieved (in a way) by defining color weights but than there is no black border anymore. ```auto color="#ffffff;0.1:#00ff00;0.1:#ffffff;0.1:#00ff00;0.1:#ffffff;0.1:#00ff00;0.1:#ffffff;0.1:#00ff00;0.1:#ffffff; 0.1:#00ff00;0.1" ``` While playing around with the graph description in the dot language I found a way to get graphviz to draw multiple edges exactly on top of each other, so I can use different `penwidth` and `style` to get a good result but I’m not sure if this behaviour is actually a bug in graphviz. ![](https://global.discourse-cdn.com/graphviz/original/1X/0167f067e4d547c588b6f4c0c56c54cc16179bbf.png) Here the `dot` code. ```auto graph { // Graph generated by WireViz // https://github.com/formatc1702/WireViz graph [bgcolor="#ffffff" fontname=arial nodesep=0.33 rankdir=LR ranksep=2] node [fillcolor=white fontname=arial shape=record style=filled] X1 [label=<

Stewart Connector SS-37000-002

male

8-pin

DA+	1
DA-	2
DB+	3
DC+	4
DC-	5
DB-	6
DD+	7
DD-	8

> fillcolor=white margin=0 shape=none style=filled] X2 [label=<

Stewart Connector SS-37000-002

male

8-pin

1	DB+
2	DB-
3	DA+
4	DD+
5	DD-
6	DA-
7	DC+
8	DC-

> fillcolor=white margin=0 shape=none style=filled] W1 [label=<

W1
CAT5e	8x	24 AWG	1 m

X1:1

WHGN

X2:3

X1:2

X2:6

X1:3

WHOG

X2:1

X1:4

X2:7

X1:5

WHBU

X2:8

X1:6

X2:2

X1:7

WHBN

X2:4

X1:8

X2:5

> fillcolor=white margin=0 shape=box style=""] edge [penwidth=10.0 color="#000000"] X1:p1r:e -- W1:w1:w W1:w1:e -- X2:p3l:w edge [style="invis"] X1 -- W1 W1 -- X2 edge [penwidth=6.0 style="" color="#ffffff;0.1:#00ff00;0.1:#ffffff;0.1:#00ff00;0.1:#ffffff;0.1:#00ff00;0.1:#ffffff;0.1:#00ff00;0.1:#ffffff;0.1:#00ff00;0.1"] X1:p1r:e -- W1:w1:w W1:w1:e -- X2:p3l:w edge [penwidth=10.0 color="#000000"]; X1:p2r:e -- W1:w2:w W1:w2:e -- X2:p6l:w edge [style="invis"] X1 -- W1 W1 -- X2 edge [penwidth=6.0 style="" color="#00ff00"] X1:p2r:e -- W1:w2:w W1:w2:e -- X2:p6l:w edge [penwidth=10.0 color="#000000"]; X1:p3r:e -- W1:w3:w W1:w3:e -- X2:p1l:w edge [style="invis"] X1 -- W1 W1 -- X2 edge [penwidth=6.0 style="" color="#ffffff;0.1:#ff8000;0.1:#ffffff;0.1:#ff8000;0.1:#ffffff;0.1:#ff8000;0.1:#ffffff;0.1:#ff8000;0.1:#ffffff;0.1:#ff8000;0.1"] X1:p3r:e -- W1:w3:w W1:w3:e -- X2:p1l:w edge [penwidth=10.0 color="#000000"]; X1:p4r:e -- W1:w4:w W1:w4:e -- X2:p7l:w edge [style="invis"] X1 -- W1 W1 -- X2 edge [penwidth=6.0 style="" color="#0066ff"] X1:p4r:e -- W1:w4:w W1:w4:e -- X2:p7l:w edge [penwidth=10.0 color="#000000"]; X1:p5r:e -- W1:w5:w W1:w5:e -- X2:p8l:w edge [style="invis"] X1 -- W1 W1 -- X2 edge [penwidth=6.0 style="" color="#ffffff;0.1:#0066ff;0.1:#ffffff;0.1:#0066ff;0.1:#ffffff;0.1:#0066ff;0.1:#ffffff;0.1:#0066ff;0.1:#ffffff;0.1:#0066ff;0.1"] X1:p5r:e -- W1:w5:w W1:w5:e -- X2:p8l:w edge [penwidth=10.0 color="#000000"]; X1:p6r:e -- W1:w6:w W1:w6:e -- X2:p2l:w edge [style="invis"] X1 -- W1 W1 -- X2 edge [penwidth=6.0 style="" color="#ff8000"] X1:p6r:e -- W1:w6:w W1:w6:e -- X2:p2l:w edge [penwidth=10.0 color="#000000"]; X1:p7r:e -- W1:w7:w W1:w7:e -- X2:p4l:w edge [style="invis"] X1 -- W1 W1 -- X2 edge [penwidth=6.0 style="" color="#ffffff;0.1:#895956;0.1:#ffffff;0.1:#895956;0.1:#ffffff;0.1:#895956;0.1:#ffffff;0.1:#895956;0.1:#ffffff;0.1:#895956;0.1"] X1:p7r:e -- W1:w7:w W1:w7:e -- X2:p4l:w edge [penwidth=10.0 color="#000000"]; X1:p8r:e -- W1:w8:w W1:w8:e -- X2:p5l:w edge [style="invis"] X1 -- W1 W1 -- X2 edge [penwidth=6.0 style="" color="#895956"] X1:p8r:e -- W1:w8:w W1:w8:e -- X2:p5l:w } ``` I’m not sure why this is working so here my question: Is there any way to force graphviz to draw edges on top of each other? Or are there any more sophisticated possibilities to style edges? ---

**Author:** ![steveroush](https://avatars.discourse-cdn.com/v4/letter/s/a9adbd/32.png) [@steveroush](https://forum.graphviz.org/u/steveroush)\ **Post date:** [July 20, 2020, 10:46pm UTC](https://forum.graphviz.org/t/forcefully-draw-edges-on-top-of-each-other/266/2 "2020-07-20T22:46:00Z")

What specific part(s) of this file are iffy to you? Could you provide a simpler graph with one set of edges? ---

**Author:** ![snowmb](https://avatars.discourse-cdn.com/v4/letter/s/a183cd/32.png) [@snowmb](https://forum.graphviz.org/u/snowmb)\ **Post date:** [July 21, 2020, 10:25am UTC](https://forum.graphviz.org/t/forcefully-draw-edges-on-top-of-each-other/266/3 "2020-07-21T10:25:13Z")

Sure here is a minimal example: ![ex10.gv](https://global.discourse-cdn.com/graphviz/original/1X/350a782e9e9df2d985fcc343131bc28ca35ed1d0.png) ```auto graph { A:e -- X:w [penwidth=9.0 color="#000000"] //A -- X [color="#ff0000"] A:e -- X:w [penwidth=3.0 style="" color="#ffff00"] B:e -- Y:w [penwidth=9.0 color="#000000"] B -- Y [color="#ff0000"] B:e -- Y:w [penwidth=3.0 style="" color="#ffff00"] C -- Z [color="#ff0000"] C:e -- Z:w [penwidth=9.0 color="#000000"] C:e -- Z:w [penwidth=3.0 style="" color="#ffff00"] } ``` without the red edge, the black and the yellow edge are drawn next to each other so that both edges are visible. If I add the red edge in between black and yellow, yellow is drawn exactly on top of the black edge. I would expect that the output is the same, if the red would be drawn first or last. But this is not the case here. I haven’t found any documentation about how the order of the edge definition matters to the drawing algorithm. Can you confirm that this behavior is intended? ---

**Author:** ![steveroush](https://avatars.discourse-cdn.com/v4/letter/s/a9adbd/32.png) [@steveroush](https://forum.graphviz.org/u/steveroush)\ **Post date:** [July 23, 2020, 1:29am UTC](https://forum.graphviz.org/t/forcefully-draw-edges-on-top-of-each-other/266/4 "2020-07-23T01:29:05Z")

[NOTE: I am not a Graphviz developer, just a “friend of the family”. I don’t speak for the developers] Cool, I think you found a fascinating “accidental” result of a complex set of algorithms. Not documented that I know of, but not necessarily a bug. A gray area. But can you depend on it, probably, but let me suggest a “more” legal alternative. The basic idea is : 1. you define the complete graph _excluding_ all the “on-top” edges 2. run it through dot with this command: **dot -Tdot myfile.gv \>myfile.dot** 3. you modify (edit) **myfile.dot** duplicating the “bottom” edges to create the “top” edges - change attribute values ( **color, penwidth, style, …** ) as needed - this process can be done manually (see below), with any programming language, or with the Graphviz **GVPR** language Then run the edited myfile.dot through this command: **neato -n2 -Tpng myfie.dot \>myfile.png** (note the **-n2** option) The FAQ has a section that helps explain, as does the documentation on **dot** as an output file format Here is an example of the result of step 3: graph { graph [bb=“0,0,252,108”]; node [label="\N"]; A [height=0.5, pos=“27,90”, width=0.75]; X [height=0.5, pos=“81,18”, width=0.75]; A:e – X:w [color="#000000", penwidth=9.0, pos=“55,90 71.006,90 36.994,18 53,18”]; // duplicated by hand A:e – X:w [color="#ff00ff", penwidth=3.0, pos=“55,90 71.006,90 36.994,18 53,18”]; B [height=0.5, pos=“99,90”, width=0.75]; Y [height=0.5, pos=“153,18”, width=0.75]; B:e – Y:w [color="#000000", penwidth=9.0, pos=“127,90 143.01,90 108.99,18 125,18”]; // again B:e – Y:w [color="#ffff00", penwidth=3.0, pos=“127,90 143.01,90 108.99,18 125,18”]; C [height=0.5, pos=“171,90”, width=0.75]; Z [height=0.5, pos=“225,18”, width=0.75]; C:e – Z:w [color="#000000", penwidth=9.0, pos=“199,90 215.01,90 180.99,18 197,18”]; // number 3 C:e – Z:w [color="#00ffff", penwidth=3.0, pos=“199,90 215.01,90 180.99,18 197,18”]; } Convoluted, yes. But definitely within the bounds of legal. If you decide to try this, you could add “extra” attributes to the edges you wanted to duplicate like dup\_pen=3 and dupcolor=blue (documented as legal). to give instructions to your script. ---

**Author:** ![snowmb](https://avatars.discourse-cdn.com/v4/letter/s/a183cd/32.png) [@snowmb](https://forum.graphviz.org/u/snowmb)\ **Post date:** [July 23, 2020, 1:49pm UTC](https://forum.graphviz.org/t/forcefully-draw-edges-on-top-of-each-other/266/5 "2020-07-23T13:49:59Z")

Wow I just play around with your suggestion and this is SUPER helpful. This solves basically all my problems, since I can force graphviz to layout some things for me and add to the layout later without it messing everything up. Very nice solution indeed! Thank you very much. I will come around later and show some results when I’m done with the scripting. 👍