User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:71.0) Gecko/20100101 Firefox/71.0

Steps to reproduce:

Go to any web page after updating to Firefox 70, while Chrome is not running.
This is on an early 2011 MacBook Pro running macOS 10.13.6 (17G9016) with a 15,4-inch (1680 x 1050) display and an AMD Radeon HD 6490M 256 MB graphics card, with both Firefox version 70 and 71.

Actual results:

Display is unreadable. Text looks like black blocks, images are (mostly) single-colour solid rectangles (see attached screenshot)

Expected results:

Page should have been displayed as it was in earlier versions, or as it is in 70 when Chrome is running. Starting Chrome in the background makes Firefox render the page correctly. Quitting Chrome immediately makes Firefox display garbled graphics again.

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The priority flag is not set for this bug.
:jbonisteel, could you have a look please?

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Hi Magnus - it looks like you are using WebRender. Can you go to about:config and set gfx.webrender.all to false, restart your browser and see if this issue still happens?

Changed the setting and restarted. Can't reproduce the problem with gfx.webrender.all set to false, and the problem comes back when setting it back to true and restarting.

Looks like your running release. Do you still see the problem if you try nightly (in a different profile)?

Sorry for not getting back earlier. I'm not being able to reproduce the issue, since a different display artifact (can't tell whether it's related to the issue causing the display artifact reported above), also specific to Firefox, is happening now. I'm attaching a screenshot of how things look as of 72.0.2, with webrender enabled. With webrender disabled, everything seems fine.

Do you have clear steps to reproduce the issue seen in comment 7? Or does it just immediately start happening when you enable WR? Does it also seem to happen when chrome is running?

Magnus, do you still see this?

Closing as no response.