Crash updating UI on background thread

[pjrobertson]

Describe the bug
Xcode gives a Unexpected outstanding background CATransaction message and a crash when opening the UI while also checking for updates.

To Reproduce
Steps to reproduce the behavior:

1. Turn on 'Check for Updates' → 'On Launch'
2. Restart Quicksilver
3. Immediately open up the preferences, and then scroll on any scroll view
4. See Quicksilver Crash

Screenshots

Untitled.mov

What version of macOS?
10.14.6

What version of Quicksilver?
Master + 1.6.1
I thought it was because of my recent changes to add a spinning wheel in the UI to show when updating, but I went back to the current release and I still got the same problem.

[pjrobertson]

I'm looking at this and thinking it's a macOS issue, so it'd be great if either @skurfer or @n8henrie could try and reproduce.

Another way to reproduce is to immediately click the 'check now' button to check for updates, then scroll the left sidebar:

Untitled.mov

[skurfer]

I remember consistently seeing a crash when checking for updates because it was trying to show the alert window on a background thread. I thought we fixed it, but can’t find the PR. Maybe it was fixed in an OS update?

In any case, I can’t reproduce the crash using either of the methods described here.

[pjrobertson]

Reopening as I found out the reason (plugin updates were running on a background thread and then causing issues when updating the interface).

Fixed by #2671

[pjrobertson]

Fixed by #2671

[pjrobertson]

Thanks for the debugging. OK, so I think this is a macOS bug then. I debugged, and the NSAlert *is* getting called on the main thread, but what’s happening is this: 1. NSAlert gets called on main thread, blocking it 2. The OS decides to use NSConcurrentScreenUpdate to update the UI (I can’t find a way not to do this) 3. The OS tried to do an update on the background thread 4. Boom I’ve only noticed this bug now because I turned on ‘Check for updates on launch’ to debug some other stuff. I think this is a pretty rare edge case, so I won’t spend any more time on it.

…

On 12 Mar 2022, at 08:59, Rob McBroom ***@***.***> wrote: I remember consistently seeing a crash when checking for updates because it was trying to show the alert window on a background thread. I thought we fixed it, but can’t find the PR. Maybe it was fixed in an OS update? In any case, I can’t reproduce the crash using either of the methods described here. — Reply to this email directly, view it on GitHub <#2668 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABEXH6NMLCKBMY26I5SFYLU7PUAHANCNFSM5QM3PH7Q>. Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. You are receiving this because you authored the thread.