1671327 - Flickering top header on Twitter

Status: NEW

(Core :: Panning and Zooming, defect, P3)

Description

[Asif Youssuff]

Attachment: r1DdT9YsqQ.mp4

Steps to reproduce:

1. Navigate to https://twitter.com/home as a logged in user
2. Use spacebar to page down page quickly

What happens:

The "Home" header disappears and reappears. See video.

Expected result:

Static navbar

2020-10-15T02:22:59.726000: INFO : Narrowed integration regression window from [cab81767, 4f3c9c44] (3 builds) to [cab81767, 32a2e59a] (2 builds) (~1 steps left)
2020-10-15T02:22:59.737000: DEBUG : Starting merge handling...
2020-10-15T02:22:59.737000: DEBUG : Using url: https://hg.mozilla.org/integration/autoland/json-pushes?changeset=32a2e59ab7260118d8d5f430e503967fad6993cf&full=1
2020-10-15T02:22:59.738000: DEBUG : redo: attempt 1/3
2020-10-15T02:22:59.738000: DEBUG : redo: retry: calling _default_get with args: ('https://hg.mozilla.org/integration/autoland/json-pushes?changeset=32a2e59ab7260118d8d5f430e503967fad6993cf&full=1',), kwargs: {}, attempt #1
2020-10-15T02:22:59.741000: DEBUG : urllib3.connectionpool: Resetting dropped connection: hg.mozilla.org
2020-10-15T02:23:00.518000: DEBUG : urllib3.connectionpool: https://hg.mozilla.org:443 "GET /integration/autoland/json-pushes?changeset=32a2e59ab7260118d8d5f430e503967fad6993cf&full=1 HTTP/1.1" 200 None
2020-10-15T02:23:00.580000: DEBUG : Found commit message:
Bug 1657822. Enable new desktop zooming scrollbar code. r=kats

The mathml reftest pref needs to be added at the same time because the test needs that pref with the new scrollbar code to pass, but it fails with that pref with the old scrollbar code. Since that test uses the minimum scale, which is only valid with overlay scrollbars, it is correct to do so.

Differential Revision: https://phabricator.services.mozilla.com/D91243

2020-10-15T02:23:00.580000: DEBUG : Did not find a branch, checking all integration branches
2020-10-15T02:23:00.596000: INFO : The bisection is done.
2020-10-15T02:23:00.596000: INFO : Stopped

Comment 1

[Asif Youssuff]

Attachment: about:support

Comment 2

[Timothy Nikkel (:tnikkel)]

Bisecting with --pref "apz.force_disable_desktop_zooming_scrollbars:false" "apz.allow_zooming:true" to see what code change caused this interestingly results in bug 1655242 being the regressor.

Comment 3

[Timothy Nikkel (:tnikkel)]

If I just do very fast touchpad scrolling I can reproduce the flickering header. So I think what happened here is that we flip the switch that makes space bar scrolling performed by apz (instead of the main thread) and so bugs that happened when doing async scrolling by apz now show up with space bar scrolling.

Comment 4

[Timothy Nikkel (:tnikkel)]

And I can reproduce the flickering header with touchpad scrolling back at least as far as 2018-01-01.

And until we fixed the bug 1655242 we weren't able to scroll fast enough with space bar scrolling expose this bug.

Comment 5

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1657822

Comment 6

[Hiroyuki Ikezoe (:hiro)]

Asif, would you mind checking the twitter's header behavior on the latest nightly? I'd think if the header is position:sticky, it should be fixed by bug 1730998. Thanks!