User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:86.0) Gecko/20100101 Firefox/86.0

Steps to reproduce:

I have 2 monitors:
Main: 2560x1440p144Hz
Second: 1920x1080p60Hz

1. Open Firefox on both monitors
2. Open any site on the main monitor
3. Open a site with a video on the second monitor
4. Interact with stuff that changes parts of the page (like hover effects)

Actual results:

The site that is displayed on the second monitor will show up on the main monitor for some frames

Expected results:

Windows should only display own content.

Only happens with hardware acceleration enabled.

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

Here is a video showing it happen.

Here are some frames of where it happened

Looks like it shifts part of the frame to the left and parts from my second monitor ended up on the main one because the second monitor is on the right of my main monitor.

It sounds more like a layer/rendering issue. Moving this to the gfx component.

Here is the same happening in Firefox Nightly "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:88.0) Gecko/20100101 Firefox/88.0" (had to compress the video)

Here are some frames from Nightly 88

Thank you for the bug report. Could you please attach a copy of your about:support information?

Here is the about:support from FF 86

Here is the about:support from FF Nightly 88

Thanks. Could you try going to about:config and try setting gfx.webrender.compositor to false, then restart and see if that helps?

Jeff, this appears to be flickering on nvidia with mixed refresh rate monitors. I know we had issues with mixed refresh rate in the past, does this sound like anything we've seen before?

Setting gfx.webrender.compositor to false helps in both stable and nightly.

Likely a dup of bug 1638709