[css-anchor-position] revert-layer should only revert the Position Fallback Origin

[fantasai]

The current spec defines the Position Fallback Origin with a special rule as follows:

Similar to the Animation Origin, use of the revert or revert-layer values (or anything else that would rollback the property to the preceding origin) acts as if the property was part of the Author Origin. (Thus, it instead reverts back to the User Origin.)

However the revert-layer keyword does not have this behavior. It's a special rule that applies only to the revert keyword.

It should therefore only apply to the revert keyword (and not the revert-layer keyword) when used in the Position Fallback Origin also.

[mfreed7]

Yes, this seems like an oversight in the spec. Happily, the shipped Chrome implementation follows your proposed behavior, so we should just update the spec. @tabatkins agrees and is in the process of updating the spec. Seems like no resolution is needed, but let us know if you disagree!

[frivoal]

A resolution wouldn't hurt, though I suppose this could fall under "Accepted as Obvious Bugfix" too.

[css-meeting-bot]

The CSS Working Group just discussed [css-anchor-position] revert-layer should only revert the Position Fallback Origin, and agreed to the following:

• RESOLVED: Fix definition of revert-layer's behavior to match the general behavior elsewhere

The full IRC log of that discussion

<emilio> fantasai: this one is I think an oversight in the spec
<emilio> ... revert-layer is defined to revert to author origin but that's not how it works
<emilio> TabAtkins: yeah I don't think I had paid enough attention to revert-layer, will fix in the spec
<emilio> RESOLVED: Fix definition of revert-layer's behavior to match the general behavior elsewhere