1561823 - Scroll anchoring makes Twitter's "N more replies" link throw all of the new tweets the top of the viewport

Status: NEW

(Core :: Layout: Scrolling and Overflow, defect, P3)

Description

[Daniel Holbert [:dholbert]]

STR:

1. Visit https://twitter.com/vandroidhelsing/status/1143657586455003136 (NSFW language)
2. Scroll down ~2/3 of the way through the page, and click the "169 more replies" link when you see it.

ACTUAL RESULTS:
Many new tweets appear, most of them thrown off the top of the screen. My scroll position is lost.

EXPECTED RESULTS:
New tweets should expand downwards. My scroll position (at the tweet just before the link that I clicked) should be preserved.

Chrome gives EXPECTED RESULTS.
Firefox Nightly gives ACTUAL RESULTS.
(Firefox Nightly with manual pref-flip layout.css.scroll-anchoring.enabled=false gives me EXPECTED RESULTS.)

Comment 1

[Daniel Holbert [:dholbert]]

Marking as a regression, since this is only an issue in builds with scroll anchoring enabled, and that's still a relatively new feature.

I think this has been broken since we added support for scroll anchoring, though. At least, it reproduces in Nightly 2019-01-19 which was back when scroll anchoring was pretty new.

Comment 2

[Daniel Holbert [:dholbert]]

(I'm testing on Firefox Nightly on desktop Linux, btw. And I can reproduce this bug regardless of whether I'm logged in to twitter.)

Comment 3

[Daniel Holbert [:dholbert]]

Attachment: screencast (Firefox Nightly on left, Chrome dev on right)

Comment 4

[Emilio Cobos Álvarez (:emilio)]

This seems to be working fine now?

Comment 5

[Daniel Holbert [:dholbert]]

Nope, still a problem for me -- I still see the same behavior shown in comment 3's screencast. (using a fresh profile on latest linux nightly)