v13 flatpak does not relaunch

[borgmanJeremy]

Flameshot Version

v13 RC1

Installation Type

Flatpak from Github

Operating System type and version

Arch (and uBlue Aurora )

Description

The v13 RC1 flatpak has an issue where if a user kills the process with ctrl+c from the CLI, the program will not restart.

Steps to reproduce

1. Install flatpak from github for v13 rc1
2. Start the flatpak via flatpak run
3. Terminate process with CTRL+C
4. Try to relaunch

Screenshots or screen recordings

No response

System Information

Arch + KDE + Wayland. Also reproduced on uBlue Aurora + KDE + Wayland

Happens on dual monitor and single laptop displays.

[borgmanJeremy]

I suspect this is an issue with the new KDSingleApplication. We saw a similar issue on the old SingleApplication dependency. However since I can only replicate this with the flatpak build, I will need to do some learning on how to properly debug the flatpak.

[borgmanJeremy]

Here is the solution implemented as a minimal working example. Ran out of time this morning, but later ill document it in detail and integrate into flameshot proper: https://github.com/borgmanJeremy/mwe_qtsignals

High level description:

• KDSingleApplication uses QLock to protect it's socket
• QLock uses PID as part of an identifier to determine if the lock is stale
• In flatpak flameshot always starts as PID 2 so the lock is not detected as stale
• Need to handle SIGTERM and SIGINT to clean up lock file on exit
• Can't call Qt functions from unix signal handlers so there is this pipe method described here: https://doc.qt.io/archives/qt-5.15/unix-signals.html
• Now when Ctrl+C is pressed, sig int is handled. When its handled it sends a message via a pipe which triggers a Qt slot. That qt slot calls quit(), and all destructors are properly called. The QLock destructor removes its lock file from the file system.

[borgmanJeremy]

closed with #4091. @mmahmoudian I think I'll make an RC2 to make sure this doesnt have weird side effects.

[mmahmoudian]

@borgmanJeremy

I think I'll make an RC2 to make sure this doesnt have weird side effects.

That would be great. I can also test it at my end too in the off chance of catching issues.