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Re: [selectors4] Use pesudo-class instead for selecting parent elems

From: Xidorn Quan <quanxunzhen@gmail.com>
Date: Tue, 3 Sep 2013 10:00:39 +0800
Message-ID: <CAMdq698snofX12T3FyvxqXf5m7ssiwqY2sV3TOY7A-bomXQR8Q@mail.gmail.com>
To: Simon Sapin <simon.sapin@exyr.org>
Cc: www-style@w3.org
On Tue, Sep 3, 2013 at 12:38 AM, Simon Sapin <simon.sapin@exyr.org> wrote:
> Le 31/08/2013 08:10, Xidorn Quan a écrit :
>
>> Hi all,
>>
>> I am new here. I have a suggestion for selecting parent elements.
>>
>> In the current draft, a new mechanism is introduced to change the
>> subjects of a complex selector, which is prepending (or appending)
>> exclamation mark, so that an element can be selected according to its
>> descendents.
>>
>> But IMHO, it is not a flexible way to do so. Sometimes we may want to
>> select not the elements with specified descendents themselves, but the
>> elements related to them, like preceding, descending, etc. Consider
>> the following document:
>>
>> <UL>
>>      <LI>
>>      <LI><UL></UL>
>>      <LI>
>> </UL>
>>
>> It is not possible for current selectors4 definition to write a
>> selector to represent LIs which follow a LI who has an UL inside.
>> There are many similar cases.
>
>
> :matches() to the rescue:
>
> li:matches(*! ul) ~ li

I found that in the overview table, :matches only accepts compound
selector as its arguments, so I didn't know this usage.

However, after I checked the details, I found that :matches accepting
complex selector requires complete profile, which might not be
implemented for CSS for performance reason. It is not acceptable to
me.

I believe that :matches which supports complete complex selector is
hard, if not impossible, to be implemented in a fast way, but it is
possible for the pseudo-class I requested which narrows the looking-up
range to its descendents.

>> However, if we use pesudo-class instead, like :contains() or
>> :has-child(), the problem can be solved. For the example above, we can
>> use "LI:has-child(UL)~LI" to select the elements required.
>>
>> IMO, this kind of notation looks more intuitive, and won't introduce
>> new symbols to complexify the grammar. And we would not need to worry
>> about whether the mark should be prepended or appended anymore. Just
>> drop it.
>>
>> What do you think about this idea?
>
> :has-child() seems less general than the subject indicator. Isn’t it?

I don't think so. :has-child() might seem to be confusing. :has() or
:contains() should be a better name.

The pseudo-class :-hitch-has() in hitchjs.com mentioned by Brian
Kardell has exactly the same function I wanted. You may want to check
it out: http://hitchjs.com/describe/native.html#has
Received on Tuesday, 3 September 2013 02:01:47 UTC

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