Open Bug 1647035 Opened 21 days ago Updated 13 days ago

Missing characters with Webrender on AMD or Intel systems


(Core :: Graphics: WebRender, defect)

77 Branch



Tracking Status
firefox77 --- disabled


(Reporter: do-not-mail-the-lion, Unassigned, NeedInfo)


(Blocks 1 open bug)


(Keywords: correctness)


(3 files)

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:77.0) Gecko/20100101 Firefox/77.0

Steps to reproduce:

Actual results:

Text was missing letters as shown in screenshot attachment

Expected results:

Text should appear normally.

OS: Unspecified → Linux
Hardware: Unspecified → Desktop

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Component: Untriaged → Graphics: WebRender
Product: Firefox → Core

Thanks for the report! Please open about:support, click on "copy text to clipboard" and paste it here.

Attached file about:support text

Is this problem easy to reproduce for you or do you need luck and time?
Can you reproduce this bug right after Firefox startup? How many tabs do you have? Do you use multiple windows? (bug 1553578)

Please try disabling all dmabuf prefs on about:config, restart Firefox and use it for a while to check if the bug doesn't come back.

(Your configuration is different from regular Firefox: Flatpak, Wayland (bug 1543600; instead of XWayland) and DMABUF are all experimental and not even enabled in Firefox Nightly yet.) Mesa 20.0.5 (bug 1634213) had an Intel regression which was fixed with Mesa 20.0.8 and 20.1.0.

Very easy to reproduce, no luck. Had other people test it too.

It's reproducible regardless of startup, tabs and windows.

Also reproducible with XWayland window and DMABUF options set to false.

Can you reproduce it with as well?

Yeah, reproduceable with nightly using webrender. Worth mentioning this is using system Mesa 20.0.7

Hmm... Could you try to test older Firefox (Nightly) versions?
$ pip3 install --upgrade mozregression
First check if you can reproduce with recent Nightly:
$ ~/.local/bin/mozregression --launch 2020-06-19 --pref gfx.webrender.all:true -a
Then try to find a problem-free version. Go back version by version.
$ mozregression --launch 74 --pref gfx.webrender.all:true -a
If you encounter a problem-free version, you could try to find a regression range like this:
$ mozregression --good 67 --bad 69 --pref gfx.webrender.all:true -a
If you get tab crashes on load, append " security.sandbox.content.level:0" to pref, to disable the sandbox.
If you can't find a regression range, it might be caused by a problem outside of Firefox.

From 67 to 69, we had another bad text rendering which I will upload. But it seems that the text that we have today in 77 was present all the way back in 70. I'm unsure what this indicates.

Perhaps it will be fixed with newer mesa. It seems my machine has 20.1.1 as an update on the host system so I'll try that on mozregression. (It will still be broken in the flatpak until freedesktop updates. Will report back after a reboot.

Mesa 20.1.1 did not fix it.

With llvmpipe it looks totally fine, right?
$ LIBGL_ALWAYS_SOFTWARE=1 mozregression --launch 2020-06-19 --pref gfx.webrender.all:true -a

That doesn't work either. I guess this shows it's not a mesa bug? But it's still linux-specific since I've had someone try on windows and it worked fine.

Lee, fonts seem broken on this user's Fedora 32. What could help to narrow this down further?

Flags: needinfo?(lsalzman)
Severity: -- → S3

I've had someone test Nvidia too so it seems to affect all Linux users using Webrender both on X and Wayland. Feel free to change the bug report to reflect that. (even though we did also llvmpipe so that should've already been changed, I think)

Has no one at Mozilla been able to reproduce this? I can provide more information if needed for reproduction purposes.

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