Selection Event

[kyledecot]

I don't believe there is currently a way tell if the user is selecting a subset of the rendered track without digging down into private information (_selectionStart / _selectionEnd). It would be useful to expose the selection (or lack thereof) via an event.

[Danielku15]

This information is exposed as playbackRange describing the time range which should be played. This comes from the fact that in cases where multiple voices or tracks are rendered, the selection range is not guaranteed to be on the same hierarchy within the score model.

Unfortunately the tickLookup is not exposed which would allow optimized lookup of the beat related to a given tick so a mapping from tick to beat would need to be done manually.

[Danielku15]

Update: I quickly exposed it.

[kyledecot]

💯 Thanks for exposing that additional property @Danielku15 – I'm not sure it helps me though. To give a little insight I'm using React in conjunction w/ AlphaTab. I want to be able to watch/observe changes to playbackRange so that I can make some UI updates.

Knowing that I don't have to dig into _selectionStart and _selectionEnd gets me 1/2 of the way there but AKAIK there isn't a good event to hook into to get updates when the user selects/deselects/changes selection. I was thinking of something like:

const handlePlaybackRangeChange = useCallback((playbackRange) => {
  if (playbackRange) {
    // ...
  } else {
    // ...
  }
}, []);

useEffect(() => {
  if (!at) {
    return;
  }

  at.playbackRangeChanged.on(handlePlaybackRangeChange);

  return () => {
    at.playbackRangeChanged.off(handlePlaybackRangeChange);
  };
}, [at, handlePlaybackRangeChange]);

[Danielku15]

Have you considered using beatMouseDown, beatMouseMove and beatMouseUp?

Those events are emitted during selection and would even give you access to the beat. If you only need the final new playback range when the selection is complete beatMouseUp is sufficient, after that you can access the playbackRange property to get the exact time range of selection.

This would only work in case of end-user interaction/selection. For any kind of programmatic update I just merged a new event playbackRangeChanged. Docs here: https://alphatab.net/docs/reference/api/playbackrangechanged/

[kyledecot]

I had looked at beatMouseUp however this didn't work for me as I was programmatically modifying the selection. Thanks for adding #782 💯