Ability to Provide Title to Legend/ Legend Groups

I’m 😢 that I can add a heading to the different groups generated by legendgroup.

I’d like to group my traces by a particular property on the input data, and also display a label.

Imagine data:

[{ 'group': 'A', name: 'thing 1'}, 
{ 'group': 'A', name: 'thing 2'}, 
{ 'group': 'B', name: 'thing' }]

If I want the legend to include context about the group, I’d have to prefix the name with the group:

- A: thing 1
- A: thing 2

- B: thing

Whereas if we had the ability to add an overarching legend headings (and for each group) we could do this:

A
 - thing 1
 - thing 2
B
 - thing

you can see where this is an issue with longer group names

[seansfkelley]

AFAICT, using absolute positioning annotations doesn’t work if you have legend groups with varying lengths. I have two legend groups of unknown size, so I can’t safely position a label at all times so as to be readable and not misleading. Unfortunately, that makes the legend significantly less useful, since many of the traces are named similarly. Unless there’s a different workaround for this case?

[etpinard]

That would be nice!

It won’t be a priority for us though as legend headings can easily be mocked using with properly placed annotations.

That said, it would a great opportunity for a community contributor.

The patch should be in src/components/legend/draw.js. Currently the has-legend-group logic is in this block.