[css-pseudo-4] Animations on ::marker?

[andruud]

We have some WPTs (mostly tentative) that expect animations and transitions to work on ::marker (see Chrome issue for list).

However, it appears that the spec does not currently allow animation and transition properties on ::marker. I'm wondering if there has been been any discussion regarding allowing this, or if we think it's a given that animations and transitions will be supported at some point.

Basically I'm wondering if I should remove ::marker from these tests, or keep them (if animation support is inevitable). (Sidenote: The reason this came up in the first place, is that the tests suddenly change behavior if ::marker is supported (via @supports selector)).

cc @birtles

[MatsPalmgren]

However, it appears that the spec does not currently allow animation and transition properties on ::marker.

What makes you think animation isn't allowed?

::marker is a CSSPseudoElement which makes it a target for animation (normative requirement). This was resolved in #3763 (comment).

[AmeliaBR]

What makes you think animation isn't allowed?

There's an explicit allow-list of properties that currently apply to marker, until the full layout model can be specified.

My assumption would be that animation/transition of the allowed properties are also allowed & that the animation/transition properties apply — but I agree that this should be specified explicitly!

[Loirooriol]

Being able to animate the properties that apply to ::marker sounds reasonable. But note that ::first-letter and ::first-line also filter which properties apply to them, and you can't animate the allowed ones.

[fantasai]

I don't see a reason to disallow animations and transitions on ::marker, so adding them to the allow list makes sense.

[css-meeting-bot]

The CSS Working Group just discussed [css-pseudo-4] Animations on ::marker?, and agreed to the following:

• RESOLVED: allow transitions on ::marker and allow animations with animations happening and animation rules applying the style

The full IRC log of that discussion

<dael> Topic: [css-pseudo-4] Animations on ::marker?
<dael> github: https://github.com//issues/4814
<dael> fantasai: We have an allow list for properties on ::marker b/c haven't figured out layout. POinted out animations and transitions not allowed but makes sense they should work. Suggestion is add them to list
<dael> Rossen_: Other thoughts?
<dael> oriol: Seems reasonable but a note it may be inconsistent since first-letter and -line restrict properties and you can't animate them. It would be inconsistent but could make sense since marker is deviding.
<flackr> s/deviding/tree-abiding
<dael> oriol: May be a bit annoying for impl b/c it will bypass filters for which properties apply. SHouldn't be hard to do I guess
<fantasai> s/deviding/tree-abiding/
<dael> AmeliaBR: So that's practical impl issue if makes harder to tell which properties can be animated. Should be able to set transition property but only ones where it works are those where allowed. But logically if you can set color you should be able to animate color
<dael> dbaron: Note thing with filtering isn't an issue with transitions since they can only go between those that apply
<dael> AmeliaBR: Making sure keyframes are properly filtered out so only those that should have an effect do
<dael> Rossen_: Hearing some feedback this might be somewhat challenging to impl but from user expectation and behavior I don't hear reasons why it shouldn't be allowed
<dael> dbaron: I don't think that' challenging. BUt not w/ animations there's two technical ways to do it and they're distinguishable. You can say animation happens and an animation rule applying the style doesn't apply or you say animation doesn't happen. First I suspect is easier but second is better api
<dael> fantasai: Plan to add more properties to ::marker once we have a layout model. Probably want to go with way animation happens b/c then don't need infrastruction in style system. Hopefullya. temp situation
<dael> flackr: Also prefer first approach
<dael> dbaron: Do have to have infrastruction b/c that they don't apply has implications for computed value. Not sure
<dael> emilio: Have a filter but if impl in FF it's a one
<dael> Rossen_: Consensus seems to be allow transitions on ::marker and allow animations with them happening and animation rules applying the style
<dael> flackr: Animation is applyed, style not observed b/c doesn't take effect
<dael> Rossen_: Objections?
<dael> RESOLVED: allow transitions on ::marker and allow animations with animations happening and animation rules applying the style