How to correct PlantUML Line Path

Question

I created this diagram using the following code. But as you can see, the lines going from (Cancel Order) and (Place Order) to (Publisher) decide to take a terribly rounded path to get their, instead of going straight to the right and then down to publisher. I tried using manual direction commands like "-down" but none of them seemed to help. Does anybody know how to fix this?

And here is my code. I appreciate any help. Thank you.

@startUML EBook Use Case Diagram
left to right direction
Actor Customer as customer
Actor EBook as ebook
Actor Publisher as publisher
rectangle "Book Catalogue" {
    together {
        Actor "Book Database" as bookLog
        (Retrieve Information) as getBook
        customer -- getBook
        getBook -- ebook
        getBook -- bookLog

        (Update Catalogue) as updateCatalogue
        ebook -- updateCatalogue
        updateCatalogue -- bookLog
    }

    together {
        (Place Order) as order
        customer -- order
        order -- ebook
        order--publisher

        (Cancel Order) as cancelOrder
        customer -- cancelOrder
        cancelOrder -- ebook
        cancelOrder--publisher
    }
}

(Ship To EBook) as shipEBook
shipEBook -- publisher
(Ship To Customer) as shipCustomer
customer -- shipCustomer
ebook -- shipEBook
shipCustomer -- ebook

(Return to EBook) as returnCustomer
(Returnto Publisher) as returnPublisher
customer -- returnCustomer
returnCustomer -- ebook
ebook -- returnPublisher
returnPublisher -- publisher

@endUML

how do you make the picture so clear? did you first export to svg and then convert to png? — FunkyBaby, Aug 02 '18 at 14:33
hey, I just did export to image (png probably?) with the vscode plant uml extension. I don't use vscode or plantuml anymore, so I can't be of much help, sorry. — aSamWow, Aug 03 '18 at 16:00

score 65 · Answer 1 · answered Feb 11 '18 at 18:58

There are some tricks that you can try, listed below. The layouting itself is performed by GraphViz (dot layouting iirc), and GraphViz simply does this sometimes. Graph layouting is a NP-complete problem, so algorithms usually take harsh shortcuts.

Typical workarounds that I've seen or used include:

adding hidden lines a -[hidden]- b
extending the length of a line a --- b (more dashes, longer line)
specifying preferred direction of lines (a -left- b)
swapping association ends (a -- b → b -- a)
changing the order of definitions (the order does matter... sometimes)
adding empty nodes with background/border colors set to Transparent

So if you really want to have a nice layout, you'll need to put some elbow grease in, but keep in mind that the layout will be still brittle -- if you add/remove items, you might need to redo it again.

I would like to point out the use of `together` done by @aSamWow. I didn't know this command before but I just successfully use it like following : `together group1 { class a class b } together group2 { class c class d } group1 -[hidden]- group2` — 6pi, Aug 01 '19 at 11:31
I didn't know about the line length feature! Thank you very much! — Fred, Jul 04 '20 at 21:56

score 48 · Answer 2 · answered Feb 15 '18 at 10:18

48

Try the options suggested by @Peter Uhnak along with linetype :

skinparam linetype polyline
skinparam linetype ortho

Give better options for lines. Using ortho - (Here)

you will get -

answered Feb 15 '18 at 10:18

Nikhil

849
8
10

1

Good idea, it does fix the problem, but Ortho lines mess up labels in plant UML so I try to avoid them for more complex diagrams. – aSamWow Feb 15 '18 at 14:04
1

"label positioning wrong in linetype ortho" - please vote for it: https://github.com/plantuml/plantuml/issues/149 – kinjelom Mar 04 '20 at 11:26

score 29 · Accepted Answer · answered May 14 '20 at 10:36

29

To make a connection less important in the layout, use [norank], e.g., a -[norank]-> b

answered May 14 '20 at 10:36

fkleedorfer

525
4
8

3

My goal with this answer is to document an undocumented PlantUML feature with minimal cognitive load in a place where related features are nicely listed (and accepted as the answer). Users of PlantUML will appreciate `norank` in the context of this question. – fkleedorfer May 15 '20 at 07:11

score 21 · Answer 4 · answered Feb 12 '18 at 05:27

21

If anyone wants to know a more specific, put probably much more useless answer, here is what I did in the end.

    order -down- publisher
    publisher -[hidden]up- order

so for some reason adding the duplicated command both ways solves it.

answered Feb 12 '18 at 05:27

aSamWow

861
1
7
9

> for some reason: I guess the reason is that every edge adds weight. In Graphviz one can specify weight of edges, but I have not found a way to do it in PlantUML. – Uwe Geuder May 26 '21 at 00:57

score 3 · Answer 5 · answered Dec 28 '21 at 07:42

3

All these good answers are compiled and referenced in the semi-official Hitchhiker’s Guide to PlantUML. See the Layout section.

Not sure how it was 3 years ago, but it's probably now a better starting point for PlantUML tweaks than SO.

answered Dec 28 '21 at 07:42

Digital Stoic

1,229
11
20

How to correct PlantUML Line Path

5 Answers5

Linked