1693998 - images distorted

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect)

Description

[Michal Kluka]

Attachment: images.png

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:87.0) Gecko/20100101 Firefox/87.0

Steps to reproduce:

1. Open https://arstechnica.com/
2. scroll down

Actual results:

Images further down the page (not visible when page loaded without scrolling) are distorted. That will sometimes fix without any intervention withing few seconds. Sometimes it will not fix. Mozregression points to https://bugzilla.mozilla.org/show_bug.cgi?id=1691859

Comment 1

[Lee Salzman [:lsalzman]]

Can you please attach your "about:support" information? Also, if mozregression output any logs, can you attach those as well?

Comment 2

[Lee Salzman [:lsalzman]]

Glenn, is there possibly a bug in the KHR support that that patch effectively enables for this case? It is uses background-blend-mode multiply, but that patch didn't do anything particularly special in terms of feature usage other than dual-source blending.

Comment 3

[Lee Salzman [:lsalzman]]

This occurs even in SWGL when KHR_blend_equation_advanced extension actually gets used instead of dual-source blending. That is useful to know, as it rules out dual-source blending or this being any sort of hardware bug. This is likely a bug in how we utilize the KHR extension (or similar) itself.

Comment 4

[Michal Kluka]

Attachment: about_support.txt

Comment 5

[Michal Kluka]

Attachment: mozregression_log.txt

Comment 6

[Glenn Watson [:gw]]

Looks like we've determined above it's related to the advanced blend code path, which was not previously enabled, that has a bug. Will need some investigation - perhaps for now we should disable that code path until someone has time to investigate further?

Although - I thought we deliberately only enabled this path for SWGL, and the about:support appears to show regular HW-WR in use?

Comment 7

[Lee Salzman [:lsalzman]]

(In reply to Glenn Watson [:gw] from comment #6)

Looks like we've determined above it's related to the advanced blend code path, which was not previously enabled, that has a bug. Will need some investigation - perhaps for now we should disable that code path until someone has time to investigate further?

Although - I thought we deliberately only enabled this path for SWGL, and the about:support appears to show regular HW-WR in use?

The same code path is now used for the dual-source multiply support.

Comment 8

[Glenn Watson [:gw]]

I did some investigation of this after discussing with Lee.

I was unable to repro locally at all, but then I realized I had my local mix-blend optimizations patch enabled (https://phabricator.services.mozilla.com/D104491). Although I thought this patch would be unrelated to the bug, it turns out it inadvertently also fixes a bug in the existing mix-blend implementation (I can repro it locally without that patch).

So, let's:

• Get the patch linked above landed as soon as the current soft-freeze is lifted.
• Let it bake in nightly for a few days to make sure it doesn't cause any other issues from the rest of the patch
• Uplift that patch to beta.

Comment 9

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

Set release status flags based on info from the regressing bug 1691859

Comment 10

[Julien Cristau [:jcristau] (back April 22)]

AIUI this is now fixed in nightly? Where do we stand wrt beta?

Comment 11

[Glenn Watson [:gw]]

It's not currently fixed in beta, but I think it's been in nightly long enough now that I am going to request uplift of the two patches (https://phabricator.services.mozilla.com/D104491 and https://phabricator.services.mozilla.com/D106572)

Comment 12

[Glenn Watson [:gw]]

Added uplift request in https://bugzilla.mozilla.org/show_bug.cgi?id=1684781#c14

Comment 13

[Mathew Hodson]

Was this fixed in Firefox 87 by bug 1695807?

Comment 14

[Lee Salzman [:lsalzman]]

(In reply to Mathew Hodson from comment #13)

Was this fixed in Firefox 87 by bug 1695807?

Bug 1695807 should have fixed this, yes.