User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:71.0) Gecko/20100101 Firefox/71.0

Steps to reproduce:

Run Firefox Nightly as of today's (Oct 3) update on Windows 7.

Actual results:

When running Firefox with webrender enabled, when a tab containing a non-system page is given focus, the min/max/close buttons of the window aren't drawn (or are drawn, and then disappear after page load is complete). The buttons do show up on system pages (options, addons, about:config, etc) without issue. Disabling webrender (and restarting the browser) allowed the buttons to be drawn normally on all tabs.

Example window screenshot: https://imgur.com/FVef7r1

Expected results:

Window control buttons should always be visible.

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

Did they use to show up? Or is this your first time trying webrender?

I've had webrender active for a very long time (at least since early this year, though I don't remember exactly when webrender went live), and have not had any issue with the buttons showing up prior to today.

Also, it may be Windows 7 specific, as another forum poster was not able to reproduce it on Windows 10.

Can you attach the contents of about:support as a text file? Thanks!

Would you mind running mozregression to track down what caused it?

https://mozilla.github.io/mozregression/

We suspect this will be fixed by the fix coming in https://bugzilla.mozilla.org/show_bug.cgi?id=1585898.

I don't have a Win7 machine available to test the fix on, unfortunately.

Assuming it'll be fixed by that patch, we don't need you to run mozregression then.

Attaching about:support info for the time being. If the problem persists to tomorrow, I'll do a regression check.

The buttons are showing up again after today's update.

Should this be closed as fixed or are there still artifacts occurring?

I'm not seeing any more artifacts. It can be closed.