[css-color-5] Out of range percentages in color-mix() seem to be implemented incorrectly in every major browser?

[LeaVerou]

The spec says that percentages outside [0%, 100%] make color-mix() invalid:

Percentages are required to be in the range 0% to 100%. Negative percentages are specifically disallowed.

However, in my testing, browsers seem to handle this differently based on whether the percentage is the result of a calculation or not, which seems absurd.
Instead of IACVT, they seem to clamp the result of the calculation to [0%, 100%].

However, given the fact that they’re all interoperable about this behavior, I wonder if I’m missing something?

[cdoublev]

You are missing this:

Parse-time range-checking of values is not performed within math functions, and therefore out-of-range values do not cause the declaration to become invalid. However, the value resulting from a top-level calculation must be clamped to the range allowed in the target context.

I think this behavior is mainly needed for relative dimensions (whose computed value may or may not be out of range).

[LeaVerou]

Thanks! I’ll close this then.