I wouldn't clamp, just like for #6701

It would seem very weird to me if progress(200px, 0px, 100px) was 1 despite 200px being farther than 100px from 0px.

This is something I thought about, and in the use cases where I tried progress(), I always wanted it to be clamped. And wrapping something with clamp(0, progress(), 1) was a bit cumbersome.

I wonder if we can make this to be controlled by an optional keyword inside progress()?

Like progress(clamped, 200px, 0px, 100px) if it is not clamped by default, or something like progress(full, 200px, 0px, 100px) if we decide to clamp by default.

Even without default clamping, having a keyword for this common case will be better than manually clamping. Personally, I would prefer to optimize for the more common use cases. But that's not a strong preference.

Maybe progress() and unlimited-progress() ?

It feels like there was a single word for unlimited progress, advance() perhaps?

As I started to use progress(), I was quite surprised that it doesn't clamp. I believe it should be clamped! If an author wants to open it up, they can easily set a wider range.

they can easily set a wider range

What do you mean? Let's say I want to know how far var(--x) is from 100px, compared with 200px. So for --x: 300px I expect 200% since it's twice as far. What wider range should I use?

It seems to me that the opposite is true: if the result is not clamped and you want it clamped, you can trivially clamp it with clamp(). But if the result is clamped and you don't want it clamped, then progress() is basically useless.