Re: [csswg-drafts] [css-animations-2, css-transitions-2] Entry and exit animations for top-layer elements (#8189)

> I'm aware of the specifics

Right, not suggesting you weren't, just saying that this is better considered a completely novel functionality.

> A new property is ok but the standard should be higher for a spec, given they last once you implement them on the web.

The alternative to "a property that exists only for transitions" (and which can have this condition enforced using existing mechanisms like the UA-!important style sheet) is "a property value that exists only for transitions" (and which has to have novel magic defined to enforce this condition). I'm not even sure what the full degree of the magic *is*, actually; we want to prevent authors from setting it (so the top-layer remains managed by the UA) which could possibly be a constraint on the computed value, but we also want to prevent authors from *un*setting it (for the same reason, so we can keep the top layer consistent when, for example, there are stacks that should close together), and I don't know how I'd do that. (I suspect the most straightforward way would be to say elements have a hidden state bit that, when turned on, forces z-index to compute to 'overlay' regardless of what the author does, and it's prevented from computing to 'overlay' otherwise? But that state bit functions identically to the 'overlay' property here.)

Both of a property and a value last once they're implemented, to the exact same degree. I don't think learnability is significantly different between the two? But being able to lean on existing functionality rather than forcing some *really* novel cascading behavior into one specific value seems like a big benefit of using a new property.

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Received on Friday, 31 March 2023 18:09:49 UTC