Enable quantization/synchronization of user actions to the beat

[RJ Skerry-Ryan]

We have solved half of the quantization problem -- loops/cues/hotcues are quantized to beats when they are set. Now we need to solve the other half -- make it possible to sync user actions (hotcue triggers, looping/beatlooping, sampler triggering) to the beat. This involves a lot of tricky engine work -- roughly the ability to delay the processing of a user action until a specified time.

[RJ Skerry-Ryan (rryan)]

Owen has added:

* seek queueing
* sync on play
* sync on hotcue trigger (though we reverted this -- should we keep it?)

What else do we need to do?

Sync on triggering samplers?

[jus (jus)]

* When throwing waveform (TSP does this)
* When clicking anywhere on the overview (TSP again)

Sync with sampler sounds cool too.

Often, e.g. for Hotcues, i found the quantization steps too wide, so i`ll end up setting Hotcues with Q disabled.
In the future, it would be cool if we`d be able to adjust the granularity from e.g. 1/ 16 beat upwards.

[Owen Williams (ywwg)]

With the new sync queuing mechanism, any call to seekAbs will adjust to match the phase of the beat -- this might have "fixed" a few of these other use cases. (seekExact is used to override phase matching).

clicking in the overview is already phase-locked.

Throwing the waveform is hard because there's a velocity decay... Someone will have to write a method that nudges the velocity so that it resolves on the beat.

[Owen Williams (ywwg)]

Unless someone knows of something that isn't being quantized, I think this is fixed.

[RJ Skerry-Ryan (rryan)]

Samplers are the big remaining thing here. I think Bug #774808 is related.

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/6170