1122965 - :hover pseudo-class doesn't work on ::before and ::after pseudo-elements

Status: NEW

(Core :: CSS Parsing and Computation, defect)

Description

[Sebastian Zartner [:sebo]]

According to bug 922669 it should be possible to use the :hover pseudo-class on pseudo-elements. Though this doesn't seem to work.

Comment 1

[Boris Zbarsky [:bzbarsky]]

It's possible for some pseudo-elements.  Specifically, the ones flagged with CSS_PSEUDO_ELEMENT_SUPPORTS_USER_ACTION_STATE in nsCSSPseudoElementList.h.  At the moment, that's just the HTML form control internal pseudo-elements.

See bug 922669 comment 3, in particular.

That said, the ::before and ::after do in fact have an Element associated with them, so I'm not sure why we can't support :hover there.  Cameron?

Comment 2

[Sebastian Zartner [:sebo]]

The needinfo was requested almost nine months ago. Cameron, can you provide the necessary info. If not, can you pass on the request to someone else?

Sebastian

Comment 3

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

I don't think Boris was asking for information; I think he was asking Cameron to do the work.

Comment 4

[Cameron McCormack (:heycam)]

Right.  (I'm taking the chance at the start of the quarter to go through my needinfo backlog so there's a greater chance of me getting to this soon.)

Comment 5

[Sebastian Zartner [:sebo]]

Once this is fixed, this should be documented at https://developer.mozilla.org/en-US/docs/Web/CSS/:hover, maybe also mentioned at https://developer.mozilla.org/en-US/docs/Web/CSS/::before and https://developer.mozilla.org/en-US/docs/Web/CSS/::after.

(In reply to Cameron McCormack (:heycam) from comment #4)
> Right.  (I'm taking the chance at the start of the quarter to go through my
> needinfo backlog so there's a greater chance of me getting to this soon.)

This "soon" is now already two and a half years long now. :-)

Sebastian

Comment 6

[Cameron McCormack (:heycam)]

So, yes, I don't think there's any real reason we can't support this, and the Selectors spec does require it to be supported.  (On all pseudo-elements, actually.)  FWIW no other browser supports this yet.

Just adding CSS_PSEUDO_ELEMENT_SUPPORTS_USER_ACTION_STATE to the relevant entries in nsCSSPseudoElementList.h is insufficient, though, so perhaps there's something else in the mouse handling code that needs to be adjusted.