[css-values] Make min and max value optional in clamp() · Issue #9713 · w3c/csswg-drafts (original) (raw)

As we know, we added clamp() because doing clamping logic with min() and max() is counterintuitive.
However, this doesn't only apply when you have both a min and a max, it’s still counterintuitive when you only have one of two. I keep finding myself using clamp() with dummy min or max values so that I can only use it for max or min respectively, which not only adds cognitive overhead, but also pointless computation.

A nice little improvement could be to make the min and max values optional via none keywords:

Before:

<clamp()> = clamp( <calc-sum>#{3} )

After:

<clamp()> = clamp( [ <calc-sum> | none ] , <calc-sum> , [ <calc-sum> | none ])

Alternative syntax: Using empty tokens for the omitted argument

<clamp()> = clamp( <calc-sum>? , <calc-sum> , <calc-sum>? )

Note that this is different from clamp( <calc-sum>#{2, 3} ): we still need empty tokens for the missing arguments, otherwise we wouldn't be able to disambiguate. I.e. clamp(3rem, 10vh) would not be valid, it would need to be either clamp(3rem, 10vh, ) or clamp( , 3rem, 10vh).
If we go that route we'd also need to add an exception to require the comma with empty arguments, per normal grammar specification rules the comma would be omitted, making disambiguation impossible.

When I first posted this I thought going the empty token route would be ideal, as none seemed too verbose, but I now think the clarity hit is not worth it, especially if we take the editorial challenges into account.

Hopefully this is such a small change we may be able to wedge it in css-values-4.

Edit: Agenda+ after discussing it with @fantasai and @tabatkins — this seems like such an easy win and pretty uncontroversial so we could move forwards with hopefully very little call time.