Bug 273617 – Scroll position is (sometimes) not correctly restored after restoring a page from the back/forward cache

• Status: NEW
• Component: Page Loading

[Daniel]

Created attachment 471249 [details]
Video showing how the scroll position is not correctly restored when going back, and back/forwards

How to reproduce quite reliably on a test page:

1. Go to https://webkit-bfcache-scroll-restore-bug.myshopify.com/collections/all
2. Enter password rtamay
3. Scroll down a bit (maybe to product 50)
4. Click a product
5. Go back

Expected behavior:

The scroll position is restored to where one left off

Actual behavior: there's sometimes some glitching but 3/4 times one ultimately ends up at nearly the top of the page, as can be seen in the attached video on latest ios safari (Mozilla/5.0 (iPhone; CPU iPhone OS 17_4_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.4.1 Mobile/15E148 Safari/604.1).


The scroll position is correctly restored in all other browsers and also on desktop safari, just not iOS.
It has something to do with the back/forward cache because when just reloading the page the scroll position is correctly maintained.

[Daniel]

Created attachment 471250 [details]
Screenshot from a `setInterval(log, 0)` that I had running on the page showing scroll position over time - safari briefly restores the correct scroll position before going back to the wrong one

[Radar WebKit Bug Importer]

<rdar://problem/127620537>