Footer scrub bar and four keyboard shortcuts drive the silent multitrack instead of the audio engine

[thcp]

static/js/main.js operates on multitrack directly, but on the default playback path the multitrack is silent and audioEngine owns the clock. Every interaction wired in that file is therefore broken.

Verified

engineMode() (static/js/player.js) returns "chunked" unless localStorage["stemdeck.audioEngine"] === "0". On that path the multitrack is mounted for visuals only and audioEngine is the transport. static/js/transport.js handles this correctly and consistently:

const tx = audioEngine ?? multitrack;     // transport.js:74, :386, :423, :596

and its own comment at transport.js:391 confirms it: "The engine emits no play/pause events (the multitrack stays silent)".

static/js/main.js never references audioEngine at all. It imports only multitrack (line 2) and calls it bare.

The broken interactions

Footer scrub bar does nothing -- main.js:489-492:

function seekToX(clientX) {
  if (!multitrack || !totalDuration) return;
  ...
  multitrack.setTime(frac * totalDuration);
}

.footer-scrub is a full-size cursor: pointer overlay. Click or drag anywhere on it: the playhead does not move and audio does not seek. Nothing happens at all.

[ and ] (seek back/forward 5s) do nothing -- main.js:655-659, same cause.

I and O (set loop in/out at playhead) write wrong values -- main.js:669, :673:

setLoopStart(Math.min(multitrack.getCurrentTime(), loopEnd - 0.5));

multitrack.getCurrentTime() is stuck at 0 on the engine path, so "set loop in at playhead" always writes 0 regardless of where the playhead actually is, and "set loop out" always writes max(0, loopStart + 0.5).

Space (togglePlayPause) and ruler clicks work correctly because they live in transport.js.

Scope

Everyone on the default configuration. Only a user who has explicitly set localStorage["stemdeck.audioEngine"] = "0" gets a working scrub bar.

Fix

Use audioEngine ?? multitrack in main.js for all five call sites, matching transport.js. Better still, export a single accessor (e.g. transport()) from transport.js and use it everywhere, so this cannot drift again -- this is the same shape as the FFmpeg PATH duplication fixed in #506.

[thcp]

Fixed in 0.16.1, which is now on main via #541.

main.js was driving the silent multitrack while audioEngine owned the clock. That is why the footer scrub bar moved nothing you could hear and why "set loop in at playhead" always wrote 0: the two were reading different positions. Playback runs through the audio engine now, so there is only one clock to ask.

The fix landed in #536. Both the scrub bar and the loop-in shortcut were checked by hand on a packaged Windows build before the release merged.

Thanks for the report. Let me know if anything still feels off once 0.16.1 is published.