Bug 264850

Summary:	Incorrect scroll snap behavior with this example
Product:	WebKit	Reporter:	Simon Fraser (smfr) <simon.fraser>
Component:	Scrolling	Assignee:	Nobody <webkit-unassigned>
Status:	NEW ---
Severity:	Normal	CC:	karlcow, m, nmouchtaris, simon.fraser, webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	WebKit Nightly Build
Hardware:	Unspecified
OS:	Unspecified

Description Simon Fraser (smfr) 2023-11-14 17:39:18 PST

https://github.com/w3c/csswg-drafts/issues/9187 points to this nested snap point example:
https://flackr.github.io/web-demos/css-scroll-snap/nested/sections.html

In Safari, I get no scroll snapping at all on that page. Firefox does snapping.

Comment 1 Radar WebKit Bug Importer 2023-11-14 17:39:40 PST

<rdar://problem/118428551>

Comment 2 Guido Bouman 2024-02-04 13:58:06 PST

For me Safari 17.1 does perform some form of scroll snapping, but incorrectly. 

There at least two issues:
- The end of the scrollable region snaps back to the last scroll anchor, making the last bit of content unreachable.
- When scroll back from end end to the start, the whenever a scroll anchor come into view, Safar snaps to the top of the element, instead of snapping to the bottom as explained in example #9 of the spec: https://drafts.csswg.org/css-scroll-snap-1/#example-e9209b74

Comment 3 Guido Bouman 2024-02-04 13:59:21 PST

Chromium has implemented the correct behavior, Firefox is similar to Safari, and has an open bug.

Comment 4 Guido Bouman 2024-02-05 00:56:43 PST

CSSWG Decision (https://github.com/w3c/csswg-drafts/issues/6863#issuecomment-1854300040):
> any postion within the overlarge snap area is a valid snap position, as defined in the (clarified) spec