[web-animations-1] Export dfns to expose the effect target of an animation

[jakearchibald]

In the view transitions spec we want to write prose about the element being animated by a specific animation.

It feels like the right prose would be something like:

1. Let effect be animation's associated effect.
2. If effect is a keyframe effect, and effect's effect target's target element is…

If that's correct, I propose:

• Export keyframe effect.
• Create a proper association between "effect target" and "keyframe effect". A lot of prose right now talks about an effect's effect target, but there's no defined association between the two. This association will be exported.
• Export effect target, and its target element and target pseudo-selector.

[birtles]

In the view transitions spec we want to write prose about the element being animated by a specific animation.

The text for getAnimations might be useful here:

Returns the set of relevant Animation objects that contain at least one animation effect whose effect target is this object

Or are you trying to go in the other direction? An Animation can target 0..n (pseudo-)elements so I guess it depends on the specific prose in mind.

[jakearchibald]

Ohh, the getAnimations prose might work out. I'll give it a go, cheers!

An Animation can target 0..n (pseudo-)elements

Ohhh, I thought the hierarchy was "animation has a single animation effect, if that's a keyframe effect, it has a single effect target". When can it target more than one?

[jakearchibald]

The getAnimations stuff looks good. Could you export:

• https://drafts.csswg.org/web-animations-1/#relevant-animation
• https://drafts.csswg.org/web-animations-1/#effect-target
• https://drafts.csswg.org/web-animations-1/#target-element
• https://drafts.csswg.org/web-animations-1/#target-pseudo-selector

Or, create a new exported algorithm for getting the animations for an element + optional pseudo.

Maybe the latter is better, so if getAnimations needs updating, other specs trying to do the same thing won't need to update too.

[birtles]

An Animation can target 0..n (pseudo-)elements

Ohhh, I thought the hierarchy was "animation has a single animation effect, if that's a keyframe effect, it has a single effect target". When can it target more than one?

With a group effect or sequence effect from Web Animations level 2. These don't exist yet but the spec has always tried to accommodate their future addition.

That, and the fact that an Animation can have a null effect are why there's not really a concept of "the element targeted by an Animation".

[birtles]

Or, create a new exported algorithm for getting the animations for an element + optional pseudo.

Maybe the latter is better, so if getAnimations needs updating, other specs trying to do the same thing won't need to update too.

Oh now I saw this comment 🤦

I'll see what I can do but I might not get it before I go away. Feel free to make up a PR for it if you have time though!