Fix crash when deleting script runner

[daves003]

Description

Avoid deleting the script runner immediately in the slot connected to finished() .
QThread is not quite done executing, so this crashed. Using deleteLater() is explicitly mentioned by Qt to avoid this problem and only delete the thread when it's fully done.

Checklist

• I have read and followed the QLC+ Coding Guidelines.
• My code adheres to the project's coding style, including:
  • Placing opening braces { on a new line for functions and class definitions.
  • Consistent use of spaces and indentation.
• I have tested my changes on the following platforms:
  • Linux
  • Windows
  • macOS

[coveralls]

coverage: 33.994%. remained the same
when pulling f5854a1 on daves003:fix-crash-on-scripts-shutdown
into 77c7ea7 on mcallegari:master.

[mcallegari]

Thanks
@jpue since you worked on #1933, is this somehow related or conflicting? Or perhaps you already observed/solved this?

[jpue]

No, I have never encountered any issues related to such crashes while working on the Script function in the past months. Therefore, I did not fix anything.

@daves003 Can you provide a concrete example of this issue or Steps To Reproduce? Or did you just notice it during code review – be it manual, using a linter, or an AI tool?

Furthermore, #1933 just adapts to Script code so that the underlying superclass Function is correctly terminated and deleted after everything Script-related has already been shut down.

I did a quick test on a branch where both this commit and the one from #1933 had been applied and this seems to work fine as well.

[daves003]

I just came across the crash when building some really short looping scripts. So instead of the AppImage I built it locally in debug mode and that showed a this = 0x0 in the script runner.

Repro that crashes consistently for me:

• New project using QML UI
• Create a script with just this line: Engine.waitTime(20);
• Create a chaser with the script as the only step
• Set hold time to 20ms
• Make sure the run order is set to loop
• Preview the chaser
• Should crash almost immediately

#1933 also looks not directly related to me. I've quickly tested a version with both of the changes and it seems to be running fine.

[jpue]

Thank you for the information.

Using the steps, I was able to reproduce the behaviour described above.

However, your fix does not solve this issue for me – QLC+ still crashes in various different Script-related place (might take a couple of seconds), seemingly at random, whereas previously, it was very localised to destructor of the ScriptRunner class, according to some quick debugging.

I was unable to find the root cause in the time available.

[daves003]

Interesting, it looked stable for me so far. I'll keep using this branch and see if I can catch crashes in other places.

[mcallegari]

Merged, thanks 👍