idea: rounded connections?

[alixander]

maybe border-radius can be set for connections too, and determines the rounding of bend corners.

[ShupingHe]

@alixander i'd love to try working on this issue

[alixander]

@donglixiaoche awesome!

I'd probably start by adding to this test:

d2/e2etests/stable_test.go

Line 2039 in a41f5c9

name: "border-radius",

See a visual delta: ./ci/e2ereport.sh -delta -test-case=border-radius

And then keep making changes to https://github.com/terrastruct/d2/blob/master/d2renderers/d2svg/d2svg.go, rerunning the above to see what's changed, until the connections look good.

[ShupingHe]

@alixander
after reading some codes, although the description above is quite concise, there are lots of details i want to confirm with you.
so, for drawing connection between shapes, basically there are these steps:

1. use the input script to calc layout(by darge/elk layout engine), then we can get route path(points) of those connections
2. convert these points to the actual points used by a curve
3. construct the svg path string of these curves(bezier curve)

and below are my questions:

1. in which condition, could a connection not be a curve?
2. should i consider ELK graph as well?
3. suppose our user set border-radius: 3px to a connection, how can we apply this to a bezier curve? by set an offset to those points that draw the curve?

[alixander]

@donglixiaoche

1. Depends on layout engine, continued in 2.
2. ELK and TALA are the only ones that give orthogonal paths. Dagre's (the default) uses curves by default, and this property wouldn't make sense on them. You would just look at the ELK tests.
3. Yeah I don't think it should have an effect on a curve.

[ShupingHe]

@alixander cool, i will just look at ELK tests then, thx!