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Re: [csswg-drafts] [css-animations] Clarify properties that are not allowed in @keyframes rule

From: Brian Birtles via GitHub <sysbot+gh@w3.org>
Date: Wed, 06 Jun 2018 08:55:48 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-394995262-1528275347-sysbot+gh@w3.org>
I would love your help!

Originally @tabatkins suggested the definition of animation types could go in V&U and it certainly made sense to me at the time. I'm not sure I understand why css-cascade would be better.

The rough idea is that there are up to three procedures that make up a type's animation behavior:

* interpolation
* addition
* accumulation

These procedures are defined in the abstract in Web Animations: [procedures for animating properties](https://drafts.csswg.org/web-animations-1/#procedures-for-animating-properties).

For most types, addition is identical to accumulation and in most cases spec authors should not have to concern themselves with the difference between these two procedures. Web Animations tries to define things such that accumulation defaults to being equivalent to addition and we should probably preserve that however we link these definitions together.

Likewise, addition doesn't make sense for many types so we should also have a sensible default for that so that in many cases all you need to define is interpolation (like Web Animations attempts to do).

Currently the definition of animation types is mostly found in [CSS Transitions](https://drafts.csswg.org/css-transitions/#interpolated-types). The proposal is to take that and move it to V&U (or wherever is most appropriate) since it is used by CSS Transitions, CSS Animations, and Web Animations.

Web Animations also has a few [definitions of animation types for a limited set of types](https://drafts.csswg.org/web-animations-1/#animation-types). Most of that spec text, however, should just be dropped once we have something equivalent in V&U. I'm happy to help with that part.

When I tried to spec this in V&U I wasn't sure how to arrange it. For example, take the [`<number>` type](https://drafts.csswg.org/css-values-3/#numbers). It seemed awkward to extend that currently very brief little section with formulae like we have in Web Animations for [animating real numbers](https://drafts.csswg.org/web-animations-1/#real-number-animation-type-section).

In fact, it seemed like a lot of the sections would get a lot longer and I wasn't sure if it was better to create a new section for animation types and risk having them get out of sync or interrupt the definitions of these types with all this talk about animation.

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Received on Wednesday, 6 June 2018 08:55:52 UTC

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