Re: [csswg-drafts] [css-values] Proposal for a 'progress' function to calculate progress between two <length> values (#7268)

Just some notes:
 - `progress()` or whatever it's called should probably provide the [input progress value](https://andreubotella.com/csswg-auto-build/css-easing-2/#input-progress-value), typically in [0, 1], but actually [-∞, ∞].
 - `mix()` is top-level. Something else will be needed for component values, see #6700. I think `progress()` should also be for component values, so names like `inverse-mix()` can be misleading.
 - `progress()` can only be the inverse when the easing function is injective (e.g. linear). With the ability to specify the easing function, if it's not injective, we can't have a global inverse. It's not clear which of the possible input progress values should be returned. Also, easing functions may not be surjective (e.g. `steps()`), so what should `progress()` return for values outside the domain? I think it may be better to just avoid easing functions in `progress()` and always use linear.

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Received on Thursday, 14 July 2022 15:39:54 UTC