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Re: [css3-conditional] @supports compounds with general_enclosed

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Mon, 28 Jul 2014 17:14:40 -0700
Message-ID: <CAAWBYDB-6nVwN9-jHptknBXhjC6WVUa9Gk_euiPmOS2=u0=CZw@mail.gmail.com>
To: Bear Travis <betravis@adobe.com>
Cc: "www-style@w3.org" <www-style@w3.org>
On Mon, Jul 28, 2014 at 4:58 PM, Bear Travis <betravis@adobe.com> wrote:
> Hello,
> I was reading the section on @supports and the general_enclosed production.
> [1] The general_enclosed production is “always false. Additionally, style
> sheets must not write ‘@supports’ rules that match this grammar production.”
> What does the “must not write” portion entail? Can the general_enclosed
> production still be part of an overall true production, if combined using a
> disjunction and a true condition, or negated? I ask because some
> implementations maintain the general_production in CSSConditionalRule’s
> conditionText and cssText [2] for a production like "@supports((margin: 0)
> or (green))”, and I wasn’t sure if this counted as writing or not.

It's just an authoring conformance criteria - we defined
<general-enclosed> for future-compat, so that new things defined in a
future spec don't result in the entire rule failing to parse and
getting ignored in legacy UAs.  However, authors *must not* use
<general-enclosed> themselves; they must stick with the actual defined
stuff.  This isn't an onerous requirement, since <general-enclosed>
doesn't do anything.

So, implementations must support it, preserving it in their
representation and giving it the specified truth value (always false),
but authors must not use it in their stylesheets.

Received on Tuesday, 29 July 2014 00:15:27 UTC

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