1744455 - gfx.webrender.compositor: Window preview in alt+tab is glitchy, 1 screen @ 60Hz, Intel+Nvidia GPUs

Status: NEW

(Core :: Graphics: WebRender, defect)

Description

[pokechu022]

Attachment: Video of the issue, recorded using OBS Studio's display capture.

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:94.0) Gecko/20100101 Firefox/94.0

Steps to reproduce:

Load https://smwcentral.net, and then press alt+tab while the page is visible. The alt+tab window preview and the preview when hovering over Firefox in the taskbar will show an incorrect preview. This might be easier to reproduce on https://www.smwcentral.net/?p=section&s=smwmusic - I was also able to reproduce it with archived, JS-free versions at https://archive.today/2021.11.21-090046/https://www.smwcentral.net// and http://archive.today/2021.11.21-090133/https://www.smwcentral.net/?p=section&s=smwmusic

I have also seen this issue on e.g. https://old.reddit.com/r/AskReddit/ but it is a lot more subtle/flickers rapidly.

Actual results:

The preview shows flickering blocks, presumably where the background image is rendered as black instead, and also experiences what I think are scaling artifacts. After the page has been loaded for a while, the number and severity of these artifacts goes down, but they reappear after refreshing the page.

These artifacts can be captured using OBS Studio's display capture; I've attached a video of it. However, I feel like additional artifacts were visible in the display capture than actually showed up on screen (though there is no easy way to verify this).

Expected results:

The preview should have matched what was actually on screen.

Comment 1

[Negritas Sergiu, Desktop QA]

Hello! I have tried to reproduce the issue with firefox 96.0a1(2021-12-06) on Windows 10. Unfortunately I wasn't able to reproduce it with the steps provided in the description.

Could you please answer the following questions in order to further investigate this issue?

1. Does this issue happen with a new profile? Here is a link on how to create one: https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles
2. Does this issue happen in the latest nightly? Here is a link from where you can download it: https://www.mozilla.org/en-US/firefox/channel/desktop/
3. Do you have any addons installed if so can you list them?

Comment 2

[pokechu022]

1. Yes, the issue happens with a new profile.
2. Yes, the issue happens in Nightly 96.0a1 (2021-12-06).
3. I do have addons installed: Don't track me Google, HTTPS Everywhere, SponsorBlock, uBlock Origin. All are enabled in private browsing. However, the issue also occurs in the separate profile and in nightly, which do not have those addons installed.

This issue also happens if I disable both display adapters (Intel(R) UHD Graphics and NVIDIA GeForce GTX 1650 Ti) in the Windows Device Manager - I thought I would try that to see if Windows' fallback display driver has the issue too, and it does, so it's probably not a graphics card/driver issue.

I'll attach the contents of about:support in case it is helpful.

Comment 3

[pokechu022]

Attachment: about:support contents

Comment 4

[Patrick (he/him)]

Able to reproduce this issue in Firefox 95 on Windows 10, using URL https://smwcentral.net

Comment 5

[Patrick (he/him)]

This bug appears to be a regression, last good build 2020-05-11, first bad build 2020-05-12. Unable to bisect further in mozregression.

Comment 6

[Luca Greco [:rpl] [:luca] [:lgreco]]

(In reply to mpj.5 from comment #5)

This bug appears to be a regression, last good build 2020-05-11, first bad build 2020-05-12. Unable to bisect further in mozregression.

Follows the push log for the range of dates from comment 5:

• https://hg.mozilla.org/mozilla-central/pushloghtml?startdate=2020-05-11&enddate=2020-05-12

Comment 7

[Darkspirit]

Please open about:config in the address bar, set gfx.webrender.compositor to false and restart Firefox. Does this help?

Comment 8

[pokechu022]

Tested on Nightly 97.0a1 (2021-12-13). With gfx.webrender.compositor as true (the default), the issue happens. With gfx.webrender.compositor as false, the issue does not happen.

Comment 9

[Christian Holler (:decoder)]

Miko, could bug 1554499 be somehow related to this? (given the pushlog in comment 6).

Comment 10

[Miko Mynttinen]

(In reply to Christian Holler (:decoder) from comment #9)

Miko, could bug 1554499 be somehow related to this? (given the pushlog in comment 6).

Possible but unlikely since the compositor pref fixes it. There are quite a few WebRender related patches on the pushlog as well so it's hard to tell which one could be the culprit without manually bisecting.