[Lens] Stacked problem with negative values

[dej611]

Describe the bug:

Depending on the order of the dimensions, stacking charts can have weird results:

Percentage charts are even more strange with the bigger segment filling up the 100% span:

Steps to reproduce:

1. Create a count() formula
2. Add a new formula of the form of -3 * count()
3. Reorder the dimension to have different results with stacked

Expected behaviour

Not sure here. Perhaps it's worth discussing with @markov00 and @monfera some ideas.

[elasticmachine]

Pinging @elastic/kibana-vis-editors @elastic/kibana-vis-editors-external (Team:VisEditors)

[flash1293]

I agree, those cases are weird. Maybe we should show a warning if there are negative values in stacked series? Not sure whether we can do much better.

[dej611]

One idea it comes to mind would be to sort, for each column, the order having the negative values always at the bottom.
Because of the color mapping, changing the sorting on one bucket seems achievable without losing any information.

As for the Percentage chart, probably considering the Math.abs of the value instead of the raw value can be an idea? That would be achievable also on the consumer side.

[flash1293]

Interesting ideas. Can we control the order per column from the Kibana side?

[flash1293]

Marking as blocked for now

[nickofthyme]

I was hopeful this fix would get into 7.16.1 but unfortunately it was MUCH more involved than expected. See fun stacking logic here. I am working to add this to 8.0 in #120271.

[flash1293]

Fixed by now