Re: [csswg-drafts] [css-values-4][css-color] Addition of `<color>` is way underspecified. (#8576)

Not to argue one way or the other on whether adding colors even makes sense, but if we do add them, I think non-premultiplied is actually the only correct answer. An addition animation is fundamentally different from a normal animation; you write it as a delta around 0, rather than as an absolute animation between two values. (Adding two *normal* animations together generally gives nonsense results, I think.) So you need a meaningful zero to start from for each value being added; premultiplied makes the zero alpha have extra effects and generally ruins things.

As for "why would you add colors", I guess being able to, say, pulse a color's lightness independent of whatever else its color might be doing is in theory something useful to do? But I think it's a pretty rare thing to do, and almost certainly better to fold into the original animation (via color-mix() or something, for example). So I think "colors don't add" is still a very reasonable option to decide on.

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Received on Wednesday, 31 May 2023 16:28:12 UTC