render: use elk edge label positioning

[gavin-ts]

Summary

Elk layout positions edge labels on the side, but we position labels in the middle and this could lead to unexpected container padding. We now configure elk to position edge labels the same way so that it doesn't add this extra padding.

Details

• fixes elk: investigate alignment issue #482
• configure elk to place edge labels on the edge
• adds e2e test

e2e report changes with new test

[alixander]

oh interesting, ELK naturally just placed the labels to the left?

[alixander]

can we tune it to... not always be left? https://www.eclipse.org/elk/reference.html

[gavin-ts]

oh interesting, ELK naturally just placed the labels to the left?

default is their SMART_DOWN option, which usually places it on the left side. ref

can we tune it to... not always be left? https://www.eclipse.org/elk/reference.html

it doesn't look like we can put it on the edge itself, but I added some padding and switched it to the SMART_UP option which usually places labels on the right instead.

[alixander]

they do allow it: https://www.eclipse.org/elk/reference/options/org-eclipse-elk-edgeLabels-inline.html

[gavin-ts]

they do allow it: https://www.eclipse.org/elk/reference/options/org-eclipse-elk-edgeLabels-inline.html

nice it looks more consistent with the other layouts in the center position