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Re: CSS-ISSUE-320: Profile :matches() / :not() for fast vs. complete implementation [Selectors Level 4]

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Mon, 22 Apr 2013 09:21:12 -0700
Message-ID: <CAAWBYDAsFi-pst+ED=v1usg6XLos5DhU-2+MeOiOss9RWpr7ww@mail.gmail.com>
To: "L. David Baron" <dbaron@dbaron.org>
Cc: www-style list <www-style@w3.org>
On Mon, Apr 22, 2013 at 6:27 AM, L. David Baron <dbaron@dbaron.org> wrote:
> On Thursday 2013-04-04 00:51 +0000, Cascading Style Sheets (CSS) Working Group Issue Tracker wrote:
>> CSS-ISSUE-320: Profile :matches() / :not() for fast vs. complete implementation [Selectors Level 4]
>>
>> http://www.w3.org/Style/CSS/Tracker/issues/320
>>
>> Raised by: Elika Etemad
>> On product: Selectors Level 4
>>
>> People keep being confused about :matches() and :not()'s intention
>> to allow full complex selectors. The only reason they're not
>> allowed is perf, so let's just make two profiles for Selectors and
>> let things like Selectors API and PDF processors implement the
>> full version.
>
> What's the performance problem with combinators here?  Allowing
> :not(div p) doesn't seem particularly worse than "div p" on its own
> (except that :not() in general can't use some of the filtering
> optimizations that we can use for "div p"); I think advanced authors
> are aware that such selectors can be slower.

You tell me.  ^_^  I thought we had pushback from implementors on
allowing that.  If y'all are okay with complex selectors in
:not()/:matches(), great!

> Or are you talking about allowing some use of combinators inside of
> :not() or :matches() that allows the "subject" to no longer be the
> last piece of the selector?  (That's a separate distinction already
> made between the "fast" and "complete" profiles, though.)

Nah, the subject indicator is definitely still in the complete profile
only for now.

~TJ
Received on Monday, 22 April 2013 16:22:01 UTC

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