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Re: [css-values] custom-idents and excluded keywords

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Thu, 17 Mar 2016 17:58:11 -0700
Message-ID: <CAAWBYDB0++7axZz3FU4ZwhiaQ4J6gEand8WOg5ZExtDVZjH+zA@mail.gmail.com>
To: Manuel Rego Casasnovas <rego@igalia.com>
Cc: www-style list <www-style@w3.org>
On Thu, Mar 17, 2016 at 1:51 AM, Manuel Rego Casasnovas <rego@igalia.com> wrote:
> in the CSS Values spec [1] we could find the following sentence:
> "This generic data type is denoted by <custom-ident>, and represents
>  any valid CSS identifier that would not be misinterpreted as a
>  pre-defined keyword in that property’s value definition."
>
> But a few lines later it says:
> "Specifications using <custom-ident> must specify clearly what other
>  keywords are excluded from <custom-ident>, if any—for example by
>  saying that any pre-defined keywords in that property’s value
>  definition are excluded."
>
> For example in the case of the CSS Grid Layout spec, it's not specified
> which keywords are excluded in the different properties that use
> <custom-ident> (for example the track sizing properties [2]).
> However, in a previous thread [3] Tab said that "minmax", "auto" and
> "subgrid" were not valid <custom-ident>.
>
> The question is if the CSS Grid Layout spec needs to be updated to
> specify the excluded keywords. Or the 2nd sentence above from the CSS
> Values spec needs to be removed/reworded.

Grid needs to be updated.  Previously, Values tried to *automatically*
define that keywords appearing the grammar at the same level were
excluded from <custom-ident>, but that ended up not actually working
in a reasonable way; it implied that different keywords could be
excluded between a longhand and a shorthand, for example.

That section of Grid was just written against the old text, and needs
to be updated to explicitly exclude the handful of keywords that can
appear near it.

~TJ
Received on Friday, 18 March 2016 00:58:58 UTC

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