RangeControl: if there are only 2 options, transform into a button group

[davewhitley]

Is your feature request related to a problem? Please describe.
A RangeControl is sometimes used when there are only 2 options, like selecting between 1 or 2 columns in the image gallery block. This is a bad user experience because only the extreme ends of the range slider are selectable. It's hard to use. A text field is also not needed if there are only 2 options. The text field is misleading in that it seems like I can input any number I'd like.

Describe the solution you'd like
I suggest that we create a guideline saying that RangeControls should only be used when the options are 3 or greater.

If there are only 2, then a button group is used.

[karmatosed]

In general I agree that any binary UI shouldn't have a range slider. Galleries by default if you have over 3 image show 3. I am not sure changing the interface is the way forward here.

The text field is misleading in that it seems like I can input any number I'd like.

I agree this should be iterated on.

Is there a different interface that would work and note change when less than 3 images?

[kjellr]

We mentioned this in the #design triage today:

https://wordpress.slack.com/archives/C02S78ZAL/p1554826903280300
(A slack login may be required to view that link)

In general, we agree. It's definitely weird to have this control max out at two choices.

It's worth noting however that in the case of the Gallery block, that control only has a max of two when you have exactly two items in a gallery. Given that caveat, it may not make technical sense to build in a separate treatment here. (Or at least, it should probably be low priority).

[karmatosed]

I think we can remove the design feedback as this seems to be agreed on as to move ahead with this.