CSS4 selector subject support

[kraih]

Once the CSS4 selector spec becomes more stable, i think we should add selector subject support to Mojo::DOM::CSS again.

http://dev.w3.org/csswg/selectors4/#subject

A previous attempt had to be aborted since the exact semantics are not clear yet, but many of the implementation details should be reusable.

3bdecef

[tempire]

Yay

[kraih]

They better hurry up with the spec, this is so useful.

[marcusramberg]

Editor's Draft 3 was released January 2012

[kraih]

Looks like semantics and syntax did not change this time, lets hope it stays that way.

[judofyr]

One thing that the spec doesn't clarify:

<p>123</p>
<p>456</p>
<div id="toc"></div>

?p ~ #toc can either:

1. Work like p ~ #toc, but instead of returning #toc it follows the parent-chain and returns one of the p's instead.
2. Return both p's.

I think that the second option makes more sense, but it's quite a lot harder to implement.

[kraih]

The spec seems pretty clear about that actually, it can only be 1.

Although the element structure that the selector represents is the same with or without the exclamation mark, indicating the subject in this way can change which compound selector represents the subject in that structure.

[dpetrov]

Editor's Draft 4 released 15 October 2012

[mokko]

Selectors Level 4, Editor's Draft 13 May 2013
W3C Working Draft 2 May 2013

[kraih]

Interesting change in the spec, a selector can now have multiple subjects.

!div > !p.warning

[kraih]

Looks like subject selectors have been replaced with the :has() pseudo-class now. http://dev.w3.org/csswg/selectors4/#relational

[kraih]

The spec is still changing so much, i don't think we can really plan ahead.