User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Firefox/68.0

Steps to reproduce:

about:config
I accept the risk!
Toggle gfx.webrender.enabled to true
restart browser

Windows 10

Actual results:

Tab labels flash.

Expected results:

No flashing.

Thanks for the report! Please open about:support, click on "Copy text to clipboard", paste it into a text file and upload it here (Attach File).
And please also try out Nightly to test whether the problem is fixed or still occurring. Thanks! :)

Likely the intel flashing bug that Jeff and a few others have been looking into. It'd be good to at least confirm this is happening on an intel GPU with about:support info.

Yes, Intel GPU. See attached about-support.txt.

I also use the Intel HD Graphics 4000 and have the same problems. I'm on firefox 70b3

Things got much worse in 69.0.
I can also see the huge flashing black rectangles in the page content (e.g. MDN).
IMHO, it renders webrender pretty unusable, even for tests.

Maros - curious to know if you still see this bug happening?

menzo do you see this with current beta?

(In reply to Wayne Mery (:wsmwk) from comment #9)

menzo do you see this with current beta?

If I set it to true it seems not to turn on:

Compositing Direct3D 11 (Advanced Layers)

Decision Log
HW_COMPOSITING
force_enabled by user: Force-enabled by pref
WEBRENDER
opt-in by default: WebRender is an opt-in feature
available by user: Force enabled by pref
unavailable-no-gpu-process by runtime: GPU Process is disabled
WEBRENDER_QUALIFIED
blocked by env: Battery Intel requires os compositor
WEBRENDER_COMPOSITOR
unavailable by env: No DirectComposition usage
WEBGPU
disabled by default: Disabled by default
blocked by runtime: WebGPU can only be enabled in nightly

Maros - curious to know if you still see this bug happening?

I do not experience the flashing anymore.