1545972 - [scroll anchoring] right sidebar sometimes jiggles indefinitely after scrolling, on www.reddit.com/r/linux

Status: NEW

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

Description

[Sean Feng [:sefeng211]]

Attachment: Screencast 2019-04-20 20:59:57.mp4

Please see the attached video. "GNU/Linux resources" moves up and down strangely.

I don't see the same behaviour on Chrome.

This is the profile https://perfht.ml/2UQ0jTh

Comment 1

[Daniel Holbert [:dholbert]]

I can reproduce.

If I turn off about:config pref layout.css.scroll-anchoring.enabled and reload, then I cannot reproduce. sefeng, would you mind testing that and seeing if you have the same results?

Comment 2

[Sean Feng [:sefeng211]]

dholbert: Thanks for rewording the bug!

Yep, turn that pref off made the issue disappeared

Comment 3

[Daniel Holbert [:dholbert]]

Attachment: dholbert's screencast of bug (minor jiggle after pagedown operations, and insufficient scrolling on final pageup operation)

For some reason sefeng's .mp4 screencast doesn't play for me directly in Firefox [edit: this seems to be bug 1450137].

So for convenience, I captured another screencast using gtk-recordmydesktop (which uses .ogv files that embed nicely).

In this screencast, I press "pagedown" on my keyboard 4 times, and then I press "pageup" once. The badness isn't as severe as in sefeng's original screencast, but I'll note two issues that are visible:
(1) the right sidebar has a jiggly "settling" after nearly every pagedown/pageup operation

(2) in my final "pageup" operation, we don't actually scroll the content feed upwards by a full viewport-height (i.e. we don't do a full pageup). Before I press pageup (at around 0:04), the highest visible line of text is "program using Gtk based on that project with some improvements". After my pageup operation completes, I'd expect that line of text to be at the very bottom of my viewport, but it only ends up ~70% of the way down.

Comment 4

[Ryan Hunt [:rhunt]]

I won't have time to look at this anytime soon, unfortunately.