Re: [csswg-drafts] [css-color-5] How should missing (`none`) components work with calc() on named components in the relative color syntax (#6920) from Chris Lilley via GitHub on 2021-12-29 (public-css-archive@w3.org from December 2021)

From: Chris Lilley via GitHub <sysbot+gh@w3.org>
Date: Wed, 29 Dec 2021 20:51:10 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-1002772015-1640811069-sysbot+gh@w3.org>

I think this is [already explicit](https://drafts.csswg.org/css-color-4/#missing):

> If a color with a missing component is interpolated with another color, the missing component is treated as having the other color’s component value. If both colors are missing the given component, the interpolated color will also be missing that component.

> For all other purposes, a missing component behaves as a zero value, in the appropriate unit for that component: 0, 0%, or 0deg. This includes rendering the color directly, converting it to another color space, etc.

There is no "other color" here so we have `lab(0% 0 0)` and 0 / 2 = 0

However, in your example the color starts as Lab and remains as Lab so "converting it to another color space" does not apply. Bur "etc" could usefully change to "performing computations on the color component values, etc"

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Received on Wednesday, 29 December 2021 20:51:12 UTC