1532294 - Facebook messenger - chat bubble background glitches on scroll

Status: RESOLVED DUPLICATE of bug 1256677

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

Description

[Cristian Fogel [:cfogel]]

Attachment: fbChat_bgFlash.gif

Affected versions
*65.0.1, 66.0b11, 66.0b12, 67.0a1 (2019-03-03)

Affected platforms

• Windows 10, macOS 10.13.6

Steps to reproduce

1. Access https://www.facebook.com/
2. Open a chat with any contact;
3. Populate the chat window with multiple messages (own user);
4. Grab the scroll bar for the chat and move the mouse up-down;

Expected result

• No visual glitches occur while scrolling up-down;

Actual result

• Background glitches for the chat bubbles can occur while scrolling

Regression range

• Last good build_date: 2016-12-27 changeset: 3119a9a0b5dee60ac77b7596ae5dbe0658f598ad
• First bad build_date: 2016-12-28 changeset: d7b6af32811bddcec10a47d24bd455a1ec1836fc
• Pushlog URL: link

Additional notes

• attached recording with the issue;
• issue persists if chat color is changed to others as well (ex.orange color);
• issue reproduces with layout.css.scroll-anchoring.enabled preff turned either off or on.

Comment 1

[Lee Salzman [:lsalzman]]

Cristi, can you use mozregression (https://mozilla.github.io/mozregression/) to help us narrow down what change might have caused this?

Comment 2

[Kartikaya Gupta (email:[e-mail])]

Looks like checkerboarding to me. I'm guessing the background color of the scrollable element is actually blue so when you scroll too fast that's what we show.

This is basically a dupe of bug 1256677, but if you can get a Gecko performance profile while this happens we can make sure to eliminate any obvious problems.

Comment 3

[Cristian Fogel [:cfogel]]

Updated comment 0 with the regression check results.
Hope it helps out!

Comment 4

[Kartikaya Gupta (email:[e-mail])]

Regression range contains the bug that turned on APZ for scrollbar dragging. So yeah this is basically checkerboarding. Can you get a Gecko performance profile?

Comment 5

[Cristian Fogel [:cfogel]]

Sorry for the delayed response.
Hope this helps: https://perfht.ml/2NOHb1d

Comment 6

[Kartikaya Gupta (email:[e-mail])]

Thanks. The content thread is spending a large amount of time running Facebook JS code, so that's likely the main reason we're not keeping up with painting and end up checkerboarding. I don't know that there's much we can do here on the Gecko side. BenWa, any thoughts on the profile in the previous comment? Things we can try in Gecko or changes that can be made on FB's side?

Comment 7

[Benoit Girard (:BenWa)]

That FB code is not performant. Is the main confusion that Gecko is picking blue as the background color? I can make sure it can find white if that reduces glitch confusions.

Comment 8

[Kartikaya Gupta (email:[e-mail])]

The blue background does it make look more glitchy, so making sure it finds white would be an improvement. But obviously improving performance so we don't checkerboard at all would be best.

Comment 9

[Neha Kochar [:neha]]

Bulk change for all regression bugs with status-firefox67 as 'fix-optional' to be marked 'affected' for status-firefox68.

Comment 10

[Kartikaya Gupta (email:[e-mail])]

Going to close this as a general checkerboarding bug. If Benoit is able to help with a fix on the Facebook side, that would be great, but otherwise there's not a whole lot we can do on the browser side for this site specifically; we'd have to look at checkerboarding in general.