Re: [csswg-drafts] [css-color-4] Expand the concept of analogous components to analogous sets of components to minimize `none` → `0` conversions (#10210)

Just discussed with @svgeesus.

So the problem is that currently carrying component( set)s forwards is defined in [13. Color Interpolation](https://drafts.csswg.org/css-color-4/#interpolation). It needs to be moved to [11. Converting Colors](https://drafts.csswg.org/css-color-4/#color-conversion).

I was wrong that Step 2 is problematic; you _need_ to convert them to a number to actually feed numbers into the color conversion algorithm. I had forgotten that carrying forwards is implemented via re-inserting `none`s in the right places at the end of the conversion. So steps 1 + 4 need to move from §13 to §11.

Then, color interpolation basically becomes:

1. Convert both colors to the interpolation color space (analogous component sets preserve their `none`s)
2. Now that they're both in the same color space, look at each component pair:
 - Is at least one of them a `none`? → result is the other value (which could be a `none` as well or a number)
 - Is neither a `none`? → interpolate as usual

Additionally, §13 seems to need some serious editorial restructuring. Significant parts of the interpolation algorithm are buried in §13.2, which should just be defining how analogous sets work and what they are.

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Received on Wednesday, 22 April 2026 17:44:56 UTC