Eclipse Layout Kernel

Question

As explained here we are currently testing Eclipse Layout Kernel.

For example, you can now have :

(You can click on the image to see the source)

This is still an alpha release, so do not expect to much from it.

The big question for our users is: do you think it's an interesting development ?

Thanks for your feedback.

Comments

Yes, it is an interesting development. I check with a previous Graphviz problem (not PlantUml) and a part is solved. https://forum.plantuml.net/12543/label-position-not-correct-in-entity-diagram

---

Having a sensible arrow between two packages (i.e. not via the corners) is a refreshing improvement. (Although I don't understand why this couldn't be an option in the existing engine).

The more options for automated layout the better - what works for one diagram might not work for another - so I'm all for this.  It looks like rank is ignored in the new engine, which certainly makes things simpler, but reduces the options for minor tweaking.

I'll try to remember to try this engine on my diagrams going forward in case it improves their look; especially when heavily using packages.

Answer 1

I think this is definitely a major improvement. Especially when working with larger diagrams and linestyle ortho the lines connecting to an interface e.g. in a component diagram look less distorted than with the current layout.

A simple plain example to test this is:

@startuml
skinparam linetype ortho
!pragma layout elk

() "/api?param" as api
component component1
component component2
component component3
component component4

component1 -- api
component2 --> api
component3 --> api
component4 --> api
@enduml

Comments

Hello all,

To compare, here are the corresponding diagrams:

Without layout elk (old fashion)
With layout elk (new fashion)

If that can help,
Regards,
Th.

---

Hello All,

Here is another example, from:

• https://forum.plantuml.net/9624/weird-layout-of-arrows?show=13995#a13995

Without layout elk (old fashion)
With layout elk (new fashion)

Regards,
Th.

---

As I demonstrate in the linked ticket, a small(?*) tweak to the existing engine to better handle shapes containing other shapes would improve the existing engine's effort.

(?* I have no idea whether treating containers the same as empty shapes from the point of view of connecting arrows is a small change or not; but it feels like code has been specifically written to handle containers differently which perhaps could be easily skipped on request...).

Answer 2

Hello All,

Here is another [old] example, from:

• https://forum.plantuml.net/1628/layout-of-grouping-component

Without layout elk (old fashion)
With layout elk (new fashion)

Perhaps some ajustements for direction management (left, right) will be necessary... 
Regards,
Th.

Comments

Again, if the old engine could allow containers to be treated as regular shapes, then it would do well for this diagram...

Answer 3

Hello PlantUML team,

• What is the algorithm with ELK for placement of nestabled elements?

See this example:

Code	Without ELK	With ELK
node Node {   artifact artifact_01   artifact artifact_02   artifact artifact_03   artifact artifact_04   artifact artifact_05   artifact artifact_06   artifact artifact_07   artifact artifact_08   artifact artifact_09   artifact artifact_10   artifact artifact_11   artifact artifact_12   artifact artifact_13   artifact artifact_14   artifact artifact_15 }

• What are the reason of the shift between the columns?

Regards,
Th.

Comments

Very nice new feature. For some diagrams the layout improves very much. Just one bug I noticed so far (not sure if this is relevant as it is still in alpha status):

For component diagrams the stereotype is missing in nested components.

Code	without ELK	with ELK
@startuml !pragma layout elk component foo <<test>>{  component bar <<test>> } @enduml