[css-pseudo-4] Add CSSPseudoElement.parentElement

[birtles]

A CSSPseudoElement would be much more useful if it were possible to cross-reference it to the DOM tree. I believe this was part of the PseudoElement specified in CSSOM before that disappeared.

(In Gecko we currently implement CSSPseudoElement with only two attributes: type and parentElement since that seems to be all we need for now.)

[Loirooriol]

Is this "parent element" the originating element, or is this a different concept?

[AmeliaBR]

I agree with @Loirooriol that "parent element" is a potentially confusing name for "originating element", because of newer pseudo-elements like ::part (or the various well-established, prefixed selectors for styling browser widgets) which might match an element inside a shadow tree, where that element has parent elements in the shadow structure.

[birtles]

Yes, I think originating element is the corresponding spec term. I'm not sure what the IDL member should be called.

[fantasai]

Maybe just .element?

[tabatkins]

Hmm yeah, .parentElement is compelling but wrong; .originatingElement is correct but soft-exceeds my complexity budget for spelling. .element sounds good.

[css-meeting-bot]

The CSS Working Group just discussed Add CSSPseudoElement.parentElement, and agreed to the following:

• RESOLVED: Add a .element prop that brings psuedos back to their element

The full IRC log of that discussion

<dael> Topic: Add CSSPseudoElement.parentElement
<dael> github: https://github.com//issues/2816
<dael> fantasai: This one was filed by birtles and I don't know too much about the APIs. They have a big red notice saying this was just an idea. It seems Mozilla is shipping some form of this API.
<dael> fantasai: We should probably put something there
<dael> Rossen_: Currently suggested API, parent element was suggested and then pointed out that was not nec. the best name at the very least. It's the originalting element and fantasai suggested .element
<dael> Rossen_: If this is about naming, we can discuss if we want to add the API. I think adding is warranted
<dael> TabAtkins: Agree having the attribute to get back to the real element is a necessary part. I like .element suggestion for the name
<dael> Rossen_: Additional comments?
<florian> sounds good
<dael> Rossen_: Objections to adding a .element prop that brings psuedos back to their element?
<dael> RESOLVED: Add a .element prop that brings psuedos back to their element

[emilio]

Gecko is not shipping this on any release channel other than Nightly: https://searchfox.org/mozilla-central/rev/bee8cf15c901b9f4b0c074c9977da4bbebc506e3/modules/libpref/init/StaticPrefList.h#137