[csswg-drafts] [css-anchor-position] Anchor Recalculation Point + Initial Load (#13352)

dshin-moz has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-anchor-position] Anchor Recalculation Point + Initial Load ==
[Anchor recalculation point](https://drafts.csswg.org/css-anchor-position-1/#anchor-recalculation-point) dictates the anchor element's position when positioning the anchored element. It seems that if the document scrolls early on during the page load, on Blink and WebKit, the anchor recalculation point occurs _after_ that scroll takes effect.

See this [testcase](https://github.com/user-attachments/files/24623807/two-scrollers.html) - The initial scroll position would cause the outer scroller to scroll - However, removing the first `rAF` call and reloading removes the scrollbar.

This has a bigger implication for `position-area` when the position area grid is dictated by the scrollport size (i.e. abs-cb with a scroller inside it) - In this [testcase](https://github.com/user-attachments/files/24623835/two-scrollers-pa.html), with the `rAF()` call uncommented, position area grid is evaluated at initial scroll position, causing its height to be smaller than the positioned element, causing the positioned element to shift up into the anchor. With the `rAF()` call removed, the scrolled position increases the height of the position area grid enough that the positioned element can fit without shifting.

This seems like it can lead to inconsistent results, depending on load times?

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/13352 using your GitHub account


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Received on Wednesday, 14 January 2026 20:12:04 UTC