UI freezes when applying actions on multiple/many tracks

[Sébastien BLAISOT]

I just discovered a bug in Mixxx 2.0.0 (64 bits on win 10 64b).

If you select a (rather) large number of tracks in the library, open right-click menu and select BPM->Reset tempo and beatgrid, the interface freezes until mixxx has finish resetting tempo and beatgrid on all these tracks.

I've just seen that with 1000 tracks selected.

This should probably be done in another low-priority thread.

[Uwe Klotz (uklotzde-deactivatedaccount)]

https://github.com/mixxxdj/mixxx/pull/1624

I'll keep this bug and not mark it as a duplicate, because this one actually describes one of the issues with the current analysis architecture. Unrelated to multi-threading.

[Uwe Klotz (uklotzde-deactivatedaccount)]

Sorry, Sebastien, that I didn't notice this earlier!

[Uwe Klotz (uklotzde-deactivatedaccount)]

This is not a duplicate, but a known issue! In fact the new issue recently reported by Sean is a duplicate of this issue:

https://bugs.launchpad.net/mixxx/+bug/1765528

[Uwe Klotz (uklotzde-deactivatedaccount)]

We don't need a separate worker thread. I already have an idea in my mind how such a reactive, event-loop-driven TrackActionScheduler can be implemented efficiently:
- shared queue of pending track ids
- queue of pending actions: action functor working on a single TrackPointer, number of total tracks, number of finished tracks

Some parts of the new TrackAnalysisScheduler might be reusable.

[Uwe Klotz (uklotzde-deactivatedaccount)]

Unassigning myself, because I don't plan any major changes on the current software design of the UI. Even the mentioned reactive and multi-threaded redesign of the analysis has not been merged, yet.

Instead we should think about decoupling the backend from the frontend and eventually replace the frontend with QML components.

[Uwe Klotz (uklotzde-deactivatedaccount)]

Proof of concept using a modal progress dialog that can be aborted:

https://github.com/mixxxdj/mixxx/pull/2656

[Uwe Klotz (uklotzde-deactivatedaccount)]

The workaround is in place. Further improvements would require substantial changes to the architecture.

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/8480