1743255 - Glitches on About window with GLX+EGL HW WR, but more likely with EGL (Can be fixed with MOZ_GTK_TITLEBAR_DECORATION=system/none)

Status: NEW

(Core :: Widget: Gtk, defect)

Description

[Rinat]

Attachment: glitches-on-about-window-with-webrender-and-egl.webm

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:94.0) Gecko/20100101 Firefox/94.0

Steps to reproduce:

• Use Firefox 94.0.2 on a machine with Intel HD Graphics 530 (Skylake) and Mesa 21.2.5
• Make sure EGL is enabled
• Open About dialog window

Actual results:

Part of the About window is transparent, part of it flashes. It's not consistent, but happened two times out of three tries in the attached video.

Expected results:

There should be no transparent parts, there should be no flashes.

Comment 1

[Rinat]

This glitch disappears when I set gfx.x11-egl.force-disabled to true.

Comment 2

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

The Bugbug bot thinks this bug should belong to the 'Core::Graphics: WebRender' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Comment 3

[Darkspirit]

Thanks for the report! Please test if it still occurs with Nightly.
The bug from timestamp 3s also occured with GLX 2.5 years ago: bug 1502519 comment 3 (at 4s)

Comment 4

[Rinat]

(In reply to Darkspirit from comment #3)

Please test if it still occurs with Nightly.

Still happens on 96.0a1 (2021-11-28) (64-bit). It's even worse, with two-three flashes per second.
On Nightly with GLX I also see rendering issues for a split second, so it's not entirely EGL-specific. They usually stabilize to a sane-looking window, but occasionally rendering issues remain. It's much harder to reproduce with GLX. With EGL on the other hand, it's almost every time.

Comment 5

[Rinat]

I've just recently updated from 94.0.1 to 94.0.2, and starting to realize that this rendering issue became a lot more "into the face", so to speak. Now more than 50% of times I open Library (Ctrl+Shift+y) either whole window or part of it is transparent. Sometimes moving a mouse pointer over the window makes parts of the Library window show themselves. Parts remain transparent until the window is resized.

Not sure when it all became so apparent. Wasn't using Library often recently.

Comment 6

[Darkspirit]

1. Does it still occur if you start Firefox with MOZ_GTK_TITLEBAR_DECORATION=system environment variable?
2. Does it still occur if you start Firefox with MOZ_GTK_TITLEBAR_DECORATION=none environment variable?
3. Would setting gfx.webrender.allow-partial-present-buffer-age to false, gfx.webrender.max-partial-present-rects to 0 and restarting Firefox help?

Comment 7

[Rinat]

(In reply to Darkspirit from comment #6)

1. Does it still occur if you start Firefox with MOZ_GTK_TITLEBAR_DECORATION=system environment variable?

This brings back window decorations. Glitches seems to go away. I've tried to open About and Library windows for several dozens of times, and wasn't able to reproduce the glitches.

2. Does it still occur if you start Firefox with MOZ_GTK_TITLEBAR_DECORATION=none environment variable?

This also brings back window decorations. Glitches also seems to go away. I've tried to open About and Library windows for several dozens of times, and wasn't able to reproduce the glitches.

3. Would setting gfx.webrender.allow-partial-present-buffer-age to false, gfx.webrender.max-partial-present-rects to 0 and restarting Firefox help?

Doesn't help. Glitches are still there.

Comment 8

[Darkspirit]

Then it really seems to be bug 1502519, but with slightly different behavior on EGL/X11/XFCE.
In case it's not: Are you able to find a regression range?
$ sudo apt install python3-pip
$ pip3 install --user mozregression
$ MOZ_X11_EGL=1 mozregression --good 2021-05-01 --bad 2021-11-28 --pref gfx.webrender.all:true
or with a wider range:
$ MOZ_DISABLE_CONTENT_SANDBOX=1 MOZ_X11_EGL=1 ~/.local/bin/mozregression --good 2020-01-01 --bad 2021-11-28 --pref gfx.webrender.all:true
or just single days:
$ MOZ_DISABLE_CONTENT_SANDBOX=1 MOZ_X11_EGL=1 ~/.local/bin/mozregression --launch YYYY-MM-DD --pref gfx.webrender.all:true

Comment 9

[Robert Mader [:rmader]]

With MOZ_GTK_TITLEBAR_DECORATION=client I was just able to somewhat reproduce this on Gnome+Xwayland, a very brief flicker from black to the proper content at the right side of the window in like 1 out of 5 cases.

Comment 10

[Rinat]

(In reply to Robert Mader [:rmader] from comment #9)

a very brief flicker from black to the proper content at the right side of the window in like 1 out of 5 cases.

I've seen that too, but reviewing screen recording frame by frame revealed that About window is first displayed a bit narrower than it needs to be, then resized, and then content appears. It's still annoying, but I'd say that's another issue. The glitches I was talking about in this bug report, they do not "fix" themselves with time.

Comment 11

[Rinat]

(In reply to Darkspirit from comment #8)

Well, it's all over the place. Glitches are unstable, so it's too easy to miss bisection turn and arrive to wrong conclusion. I've tried to track specifically glitches at right and bottom borders of About window. Since the bug title was changed to "GLX+EGL", I didn't force EGL:

./.local/bin/mozregression --pref gfx.webrender.all:true gfx.webrender.enabled:true browser.tabs.drawInTitlebar:true browser.tabs.inTitlebar:1 --good=2020-01-01

which gave me this: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=7c4202065cd61b0d45a5c82ab1c177752902b960&tochange=48913f408b556755f3195883a689e0b60ef356ed.
Maybe I'm missing something, but to me this changeset range doesn't have anything related to rendering.

Another time when I was chasing general rendering issues of the About window, like some transparent areas, or all-white areas, or all-black areas. It gave me this range: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=05dbdc65a0da4889b4675986e80d0ed9ddf5b821&tochange=5a65ca077fd746f5f977342f2e0fc112ed79ad31.

I've noticed once that I've got all-black About window with a Firefox version from 2019-01-01. Then I've tried to start mozregression at 2018-06-01, and it resulted in this range: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=9f9a9234959f114825f58beee0cffbab82d0bb29&tochange=6e842238034cd847ede178b4e65ea07704e4ffe6. During this run I opened About window dozens of times. Rendering issues (all-white or all-black windows) are hard to reproduce, so this range is likely to be wrong.

And it seems that browser.tabs.drawInTitlebar:true is not strictly related to glitches, as I've seen all-black window with system title bar visible.

Comment 12

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

The bug has a release status flag that shows some version of Firefox is affected, thus it will be considered confirmed.