[Lens] Limit top values & filters on waffle visualizations

[ghudgins]

Describe the feature:
Limit the number of top values & filters allowed in waffle visualizations

Describe a specific use case for the feature:
Mitigate issues like this one which stem from how waffle calculates 1% bins:
elastic/elastic-charts#1516

[elasticmachine]

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

[ghudgins]

@elastic/datavis @gvnmagni this was discussed in a weekly late last year. what should the limit itself be?

[gvnmagni]

@elastic/datavis @gvnmagni this was discussed in a weekly late last year. what should the limit itself be?

I don't remember exactly but I believe the decision should revolve around the size of those data categories. The problems arose when we try to display categories with values close to 1%, so close to one square. Due to rounding in values we would end up with issues.

This could be a way to see his, we could prevent these errors putting all categories with value below 1% into a generic "other" or something similar. But don't take this for final since this is an over-simplistic solution, let's ping @monfera, @flash1293 and @markov00 to see if they remember a bit better.

[markov00]

Together with the reasoning provided by Giovanni, we need also to consider the number of colors used. We can have a full rainbow carousel because we are showing 100 different 1% series: the rule 5 ± 2 to me always applies, it's a good compromise and allow the user to clearly discern the colors, link them to a name in the legend and remember that name when watching again the chart next time.

[flash1293]

This issue just mentions top values and filters - does this mean we are fine with date histogram and intervals because they are not as common? As the buckets are automatically generated for these it will be much more complex to limit them in a way transparent to the user.

About terms and filters:

• For top values: When switching from another chart type to waffle, should it change the value the user entered? If they move away to a different chart type, is it OK the capped value is capped or should the original value be restored?
• For filters: When switching from another chart type to waffle and there are more than 7 filters defined, should it remove existing filters? Or should it keep them around in a "disabled" fashion somehow? I'm a bit concerned about removing them - changing the number of terms is very simple, but restoring the filters might be a lot of work

[markov00]

About terms and filters:

• For top values: When switching from another chart type to waffle, should it change the value the user entered? If they move away to a different chart type, is it OK the capped value is capped or should the original value be restored?
• For filters: When switching from another chart type to waffle and there are more than 7 filters defined, should it remove existing filters? Or should it keep them around in a "disabled" fashion somehow? I'm a bit concerned about removing them - changing the number of terms is very simple, but restoring the filters might be a lot of work

I think this really needs do be aligned with the Lens behaviour is similar situations, it should be clear, from the UX point of view, what is going to happen when switching between non-compatible charts: are you "keeping around" the unused configurations or are you removing them? if you are removing them, when do you perform that? at the time of saving the viz?
If values needs to be limited (for example if a previous max value needs to be reduced in a different chart) do you want to keep the previous value? what do we mean by "previous value" the last one before the switch? the value of 3 charts ago?
I think all this needs to be considered and aligned with your overall strategy of undo/redo in Lens, and it should be always clear and aligned across chart types.