User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:95.0) Gecko/20100101 Firefox/95.0

Steps to reproduce:

I had previously configured Firefox to show the regular system title bar.

I was running Firefox 94 on the beta channel, and was prompted to restart the browser for an update.

Actual results:

After updating, there was no title bar. Thus there was no way to move the Firefox window, or minimize/maximize/close it using the usual buttons on the title bar.

Eventually I tried "Customize Toolbar", where I found the Title Bar checkbox that had somehow been forcibly turned off during the update. Checking the box cause the title bar to reappear as desired.

Expected results:

The browser should have continued to respect the "Title Bar" setting across upgrades.

The Bugbug bot thinks this bug should belong to the 'Firefox::Toolbars and Customization' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Just ran into this on my Mac as well (with an unrelated profile), so it wasn't a one-off.

Before updating I deliberately went into "Customize Toolbar" and explicitly toggled "Title Bar" off and on, to see if that would make any difference.

Then after quitting and applying the update (95.0b2), I launched Firefox and found that my title bars had been turned off.

As before, I was able to manually turn them back on after the update.

Setting this to NEW as I could reproduce this when updating from Firefox 94 Beta to Firefox 95 beta - tested on macOS Big Sur 11.6 and Windows 10 x64.

Manually looked for a regression window and the Title Bar is firstly missing when updating to Nightly 95.0a1 from October 22nd - build ID: 20211022213234.

Pushlog: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=f12b7ea34395623b0480b78451e5a0fb6eeb7707&tochange=9226c23abfe35c9cea21fc73726568f86276c8af

:simona.marcu, since this bug is a regression, could you fill (if possible) the regressed_by field?
For more information, please visit auto_nag documentation.

Could it have been regressed by bug 1736518? It was a Linux bug but some of the files modified seem to be shared ones across OSes. Martin?

Yes, that's possible, especially https://phabricator.services.mozilla.com/D129004 . Emilio, any idea here?
Thanks.

Gijs do you know how to potentially migrate users from a bool to an int pref? Do we need to keep the old pref as is, then use a new one or something?

Err misclick

Something like this ought to do?

https://hg.mozilla.org/mozilla-central/rev/9fdfec4d93d3

Comment on attachment 9250167 [details]
Bug 1739539 - Rename titlebar pref and add migration from old pref. r=Gijs

Beta/Release Uplift Approval Request

• User impact if declined: Avoids resetting user titlebar preferences.
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: comment 0
• List of other uplifts needed: none
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Relatively simple rename + migration.
• String changes made/needed: none

Looks like I don't need to do anything here anymore. Sorry, I was out sick.

(Also, you got very lucky with the migration being upliftable, nice!)

Comment on attachment 9250167 [details]
Bug 1739539 - Rename titlebar pref and add migration from old pref. r=Gijs

Approved for 95 beta 8, thanks.

https://hg.mozilla.org/releases/mozilla-beta/rev/eb1599b9b1fe

I have reproduced this issue using Firefox 94.0b1 on Win 10 x64.
I can confirm this issue is fixed, I verified using Firefox 95.0b9 on Win 10 x64 and macOS 10.15.

Verified on 96.0a1 the issue is fixed, tested on Win 10 x64 and macOS 10.15.