In #9598 it was resolved that anchor() computed to a pixel value, which ended up in edits in https://drafts.csswg.org/css-anchor-position-1/#scroll and elsewhere such that some scroll adjustment is snapshotted every frame (at an undefined time).

That timing should be defined. The spec says:

Define the precise timing of the snapshot: updated each frame, before style recalc.

But before style recalc seems wrong? The scroll position there depends on whether somebody had updated layout before, or otherwise it flickers... Or something like that?

• What should be the timing of that operation?
• Also, presumably we should also change the used value definition of the inset properties to add that offset, so that div.style.left = getComputedStyle(div).left round-trips? But it is super-weird that the position getComputedStyle() returns depends on whether you're before or after style recalc... wat?

I still think it'd be easier if we just didn't do the interleaving dance but... ;)

cc @dshin-moz, @andruud, @tabatkins, @fantasai