Sample Library Browser, Step Sequencer, MIDI, Sample Recording, Effects Rack - #3

Reverse-engineered the real event schema from a user-recorded .xpj
project (note events live per-track at
sequences[].value.trackClipMaps[0][entryIdx].value.eventList.events,
960 ticks/beat, note = padIdx + 36) and wired the step sequencer's
pattern into the existing kit-export pipeline so it shows up as a
real, editable sequence on the hardware instead of only playing back
live from the app.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Panels can be dragged by their header to anywhere in the window
(pointer-drag, matching the existing Knob/PitchFader idiom;
double-click resets to the docked position), composing a
--drag-x/--drag-y translate on top of each panel's existing
slide-open/centering transform rather than fighting it. The
bottom-left HUD can be hidden/restored via a small persistent tab,
with hudVisible persisted alongside the other UI settings.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Uses Electron's session.setDisplayMediaRequestHandler with
useSystemPicker: true so getDisplayMedia triggers macOS's own
ScreenCaptureKit-backed picker — pick a specific window (a browser
tab, VLC, Plex) and capture just its audio. Recording taps a
dedicated native AudioContext via a ScriptProcessorNode (discovered
live that Tone.getContext().rawContext is actually Tone's
standardized-audio-context wrapper, which doesn't implement
createScriptProcessor), encodes to 16-bit PCM WAV with a new
hand-rolled encoder, and offers a waveform preview + click-to-assign
pad picker before committing the take.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

…ture

getDisplayMedia() worked, but every recording attempt failed with
NotAllowedError: Permission denied even after granting Screen
Recording in System Settings. Root-caused live (via CDP against the
packaged app) by logging every permission string Electron actually
checked: Chromium gates the getDisplayMedia() call itself on
"display-capture", but separately checks "media" to grant use of the
resulting audio track — and only "display-capture" was allow-listed.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Two more bugs found and fixed after the permission fix, both
root-caused live via Chrome DevTools Protocol attached directly to
the packaged app:

1. useSystemPicker's native macOS picker never actually returns an
   audio track (confirmed: electron/electron#44685, still open).
   Dropped it entirely in favor of granting audio: "loopback"
   directly in handleDisplayMediaRequest — capture is now always
   system-wide (no more per-window picker UI).

2. The direct loopback grant then returned an audio track that
   looked successful but was silently dead (readyState: "ended",
   zero signal, no error) — recent Chromium defaults to Apple's new
   CoreAudio Tap API for macOS loopback, which needs a different,
   newly-introduced Info.plist key (NSAudioCaptureUsageDescription)
   almost nothing has yet, and fails with no fallback when it's
   missing (electron/electron#49607). Fixed by explicitly disabling
   that path via disable-features: MacCatapLoopbackAudioForScreenShare.

Confirmed with real captured audio (readyState: "live", strong RMS
signal) and end-to-end through the actual UI: record, stop, waveform
preview, pad assignment, playback from that pad.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

getDisplayMedia's `audio: true` shorthand defaults echoCancellation,
noiseSuppression, and autoGainControl all to true, and channelCount
to mono — even for system-audio loopback. Those are voice-call DSP
tuned for mic input; applied to music/video they genuinely mangle
the signal.

Confirmed numerically with a clean 440Hz test tone: with the
defaults on, the captured signal measured 431.5Hz with amplitude
drift and discontinuities; with echoCancellation/noiseSuppression/
autoGainControl explicitly disabled and channelCount:2 requested, it
measured an exact 440.0Hz with a flat RMS envelope and zero
discontinuities.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

…iles

- Find the MPC SD card by scanning /Volumes for MPC-Sample/Projects (any
  volume name, e.g. SDCARD) instead of hardcoding MPC-SD; eject uses it too.
- Shrink waveform peaks from 600 to 72 points (thumbnail is 72px). The old
  cache hit ~526 MB on a 25k-sample library, exceeding V8's max string length.
  Stale-format cache entries are re-decoded.
- Batch library decode progress into one store update per 250 ms instead of
  rebuilding the entry list per file.
- Hide unreadable/corrupt audio files from the Sample Browser.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

The renderer is served from http://localhost in dev, making fetch() of
mpc-sample:// cross-origin. Register the scheme with corsEnabled and send
Access-Control-Allow-Origin on audio responses.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

… pass

The hardware forces add-effect -> resample -> add-next-effect per stacked
effect. Firmware research found no MIDI/USB control surface over the
effects engine to automate that remotely (see mpc-firmware-research:
the device's /api/v1 API is real but gated behind on-device PIN pairing).

Built an in-app workaround instead: a chain of filter/distortion/
bitcrusher/chorus/delay/reverb that renders through Tone.Offline in a
single pass and writes the result back onto the pad as a new sample.

- src/audio/effects.types.ts: plain, serializable EffectInstance chain.
- src/audio/effectsChain.ts: renderEffectsChain (offline) and
  previewEffectsChain (realtime audition) share one node-building path.
- src/components/EffectsRackPanel.tsx: new panel, opened via an
  "Effects..." button in KitEditor's per-pad editor.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Cover everything built on this branch: sample library browser (25k+
files), auto-tagging, step sequencer with native .xpj export, system-audio
sample recording, the offline effects rack, MIDI in/out, and the direct
unzipped SD card workflow.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

…-browser

Sample Library Browser, Step Sequencer, MIDI, Sample Recording, Effects Rack