[css-animations-1][css-animations-2] Should any of the new `animation-*` longhands be forbidden in @keyframes ?

[nt1m]

Currently the spec says:

The inside of accepts any CSS property except those defined in this specification, but does accept the animation-timing-function property and interprets it specially. None of the properties interact with the cascade (so using !important on them is invalid and will cause the property to be ignored).

I think this prose is outdated and probably doesn't take in account animation-range and other new stuff defined in css-animations-2.

[bramus]

The title of this issue suggests to exclude the properties introduced by scroll-driven animations, but I think it would be more broader than that. As in: none of the animation-* longhands are accepted inside a <declaration-list> inside of a <keyframe-block>, with the exception of animation-timing-function property.

I believe it’s that what you mean?

[nt1m]

Yes!

[ydaniv]

Isn't -composite also an exception? I guess it's currently only valid in WAAPI.

[nt1m]

Isn't -composite also an exception? I guess it's currently only valid in WAAPI.

It's possible I missed some exceptions, my point here is that the whole set of forbidden properties should be well defined to include stuff from level 2 if necessary.