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Re: [selectors] Validity of pseudo-elements per context

From: fantasai <fantasai.lists@inkedblade.net>
Date: Thu, 27 Aug 2015 15:46:13 +0200
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: "www-style@w3.org" <www-style@w3.org>, Anne van Kesteren <annevk@annevk.nl>
Message-ID: <55DF14A5.2060606@inkedblade.net>
On 08/27/2015 12:38 PM, Tab Atkins Jr. wrote:
> On Thu, Aug 27, 2015 at 3:07 AM, fantasai <fantasai.lists@inkedblade.net> wrote:
>> We don't define anywhere what pseudo-elements the DOM methods accepting
>> a selector are allowed to use.
>>
>> For example, IIRC they can only return elements, so any selectors that
>> use most pseudo-elements should be invalid. E.g. ::selection, ::before,
>> ::first-letter, etc. should all be invalid.
>>
>> However, we might want that using ::shadow or ::content as a combinator
>> is valid, so that
>>    ::shadow
>> is either invalid or returns nothing but
>>    ::shadow div
>> is valid and returns <div> descendants of any shadow trees.
>>
>> I think this should be done by DOM specifying what it accepts rather
>> than Selectors defining what DOM should accept.
>
> You're confusing some issues.
>
> Wrt whether pseudo-elements should be returned by the matching
> algorithm when some API invokes it, that's controlled by an argument
> to the matching algorithm already.  You specify when you invoke it
> which pseudo-elements you want to allow in your result set.

Right. And DOM doesn't specify that flag atm, which means it gets
pseudo-elements in its result list atm.

> Wrt whether pseudo-elements are valid or invalid in a particular
> invoking context is of course definable by whatever thing is invoking
> Selectors.  We alter the set of "valid" things depending on context
> for several selectors in the spec already.

Yes, my point is that we need to define the set of DOM-valid things
somewhere. We could do it in Selectors (by creating a profile that
DOM references) or DOM could define it, or we could make the DOM-valid
profile the default one that you get when you reference Selectors.

But right now DOM just references Selectors and, since it doesn't say
otherwise anywhere, gets everything in it (which is perfect since the
current spec doesn't include anything we don't want) and nothing
outside it (which isn't great for Shadow DOM-supporting UAs, who'll
want the pseudo-elements in css-scoping).

~fantasai
Received on Thursday, 27 August 2015 13:47:06 UTC

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