Affected versions

• Firefox 91.2.0esr
• Firefox 94.0 RC
• Nightly 95.0a1

Affected platforms

• macOS 11.6 with TouchBar

Steps to reproduce

1. Start Nightly
2. Have fission enabled from about:preferences#experimental
3. Restart for fission to apply
4. Load the testcase from bug 1730750 comment 2
5. Check the TouchBar

Expected result

• Search bar from TouchBar is usable.

Actual result

• Exit Fullscreen is displayed in the TouchBar and is unusable. A restart is needed to recover.

Additional notes

• I marked this as a security bug but please change it if its not required

I found it is much easier to reproduce this via test script in https://bugzilla.mozilla.org/show_bug.cgi?id=1736053#c0.
I could even reproduce this on 86, so it seems not a recent regression.
It could be recovered by entering and exiting a fullscreen normally again.

It is because we didn't notify "fullscreen-painted" observer after we exit fullscreen on chrome window, so the touchbar doesn't get updated in https://searchfox.org/mozilla-central/rev/6deb8b6af57a8b5b6b1bcb143ea498e566475d8d/browser/components/touchbar/MacTouchBar.js#433-449, I think the fix of bug 1739220 would also help this.

The fix of bug 1739220 would also ensure we notify "fullscreen-painted" observer properly for chrome window, and tests added in bug 1741280 also tests "fullscreen-painted" observer in a bunch of different cases. Let's wait for bug 1739220 and verify again.

The fix of bug 1739220 should also fix this. Bogdan, would you mind helping to verify this? Thanks!

I don't have access to bug 1736053 in order to try the test script, but with the testcase from bug 1730750 I can no longer reproduce this issue using latest Nightly 97.0a1 on my MacBook Pro with TouchBar.