Not entirely sure where to post possible bugs

I’m running Manjaro, up until recently building from the AUR repo was working for me, and I understand this isn’t the “stable” repo, but just wanted to report the issue. The controller I’m using started throwing this set of errors starting maybe about a bit ago when the AUR build started 2.4.0 pre-alpha.

Uncaught exception at line 1500 in file file:///usr/share/mixxx/controllers/common-hid-packet-parser.js.
Exception:
Error: script tried to connect to ControlObject (, enabled) which is non-existent.
Backtrace:
@file:///usr/share/mixxx/controllers/common-hid-packet-parser.js:1500
@file:///usr/share/mixxx/controllers/Traktor-Kontrol-S4-MK2-hid-scripts.js:561
@file:///usr/share/mixxx/controllers/Traktor-Kontrol-S4-MK2-hid-scripts.js:505
@file:///usr/share/mixxx/controllers/Traktor-Kontrol-S4-MK2-hid-scripts.js:669

Please report bugs on launchpad: Reporting Bugs · mixxxdj/mixxx Wiki · GitHub

I want to report that I experienced similar problems too this week, on the 2.3 branch (I didn’t test a recent build of Mixxx for some time, so I don’t know when the problem appeared)

It seems as if the javascript engine somehow started forgetting about things. In my case, it is as if the Button Object didn’t know it is a Component, so it doesn’t find the methods declared.

I will try to dig into this during this weekend.

This is the output I got withMixtrack Platinum (the lines on the mixtrack platinum script are slightly different than the official because I have some mods):

Uncaught exception at line 73 in file file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js.

Exception:
  TypeError: Property 'outValueScale' of object [object Object] is not a function

Backtrace:
output@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js:73
output@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/Numark-Mixtrack-Platinum-scripts.1.js:418
@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js:139
trigger@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js:138
Component@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js:52
Button@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js:163
@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/Numark-Mixtrack-Platinum-scripts.1.js:389
@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/Numark-Mixtrack-Platinum-scripts.1.js:499
@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/Numark-Mixtrack-Platinum-scripts.1.js:41


Uncaught exception at line 418 in file file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js.

Exception:
  TypeError: Property 'send' of object [object Object] is not a function

Backtrace:
output@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js:418
@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js:139
trigger@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js:138
Component@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js:52
Button@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js:163
SamplerButton@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/midi-components-0.0.2.3.js:368
@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/Numark-Mixtrack-Platinum-scripts.1.js:646
@file:///C:/Users/jazet/AppData/Local/Mixxx/controllers/Numark-Mixtrack-Platinum-scripts.1.js:46

2.4 uses a the new QJSEngine instead of the hacky QScriptEngine.

If a callback uses this, you now need to use the standard JavaScript bind() method. Check the documentation: Function.prototype.bind() - JavaScript | MDN

Example: migrate legacy controller system to QJSEngine by Be-ing · Pull Request #2682 · mixxxdj/mixxx · GitHub

That might be a possible cause of script errors on 2.4. No idea about 2.3 though.

As for my 2.3 problems. I refreshed my local repo ( was from december) and did a clean rebuild without fatal assertions and now it works without issues.

I also reinstalled a precompiled version out from downloads.mixxx.org/builds/2.3/windows and something weird happened: It was not updating the .exe file. I had to uninstall and reinstall it.

With the installer version, I get the fatal assertion on startup due to the missing group on the pitch pot. Patching the controller script to avoid the fatal allows to execute the application and no other errors appear.
So it seems it was some build problems from october-december.