Re: [csswg-drafts] [css-backgrounds-4] Allow repeating `none` in `box-shadow-offset` (#8567)

`#{0,}` is valid but also confusing (one or more, or zero or more?).

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I understand that the use of `none` in coordinating value list does not get much attention (#2031 has been around for 5 years). Authors will use it alone in 99% of cases.

People are saying that implementing coordinating list value is hard in the [transcript for #7164](https://github.com/w3c/csswg-drafts/issues/7164#issuecomment-1201340918). I am not sure I identify the exact nature of the complexity but it could perhaps be decreased a bit by consistently allowing `none` to repeat in these shorthands and the corresponding coordinating list base property.

And why prevent the author from using `none` with other values, even if it turns out that it is always useless for the corresponding shorthand?

Below is a summary of the restrictions on `none` in shorthands taking a coordinating list value:

- `animation`
  - `animation` allows `none` with other longhand values
  - `animation` and `animation-name` allow repeating `none`
- `background`
  - `background` allows `none` with other longhand values
  - `background` and `background-image` allow repeating `none`
- `mask`
  - `mask` allows `none` with other longhand values
  - `mask` and `mask-reference` allow repeating `none`
- `transition`
  - `transition` allows `none` with other longhand values
  - `transition` disallows repeating `none` **(in prose)**
  - `transition-property` disallows repeating `none`
- `scroll-timeline` and `view-timeline`
  - `*-timeline` allows `none` with other longhand values
  - `*-timeline` allows repeating `none`
  - `*-timeline-name` diallows repeating `none`

In my opinion, `box-shadow`, `transition` (again, cf. #2031), `scroll-timeline-name`, `view-timeline-name`, should allow repeating `none`.

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Received on Tuesday, 14 March 2023 08:35:02 UTC