fix(transpose): open a song at the key its saved record holds

static/js/mixer.js

@@ -21,7 +21,7 @@ import { storeGet, storeSetDebounced, storeFlushPending } from "./utils.js";
 import { getMode } from "./mode.js";
 import { t } from "./i18n.js";
 import { stemFileExt } from "./playbackStems.js";
-import { PITCH_MAX, PITCH_MIN, clampPitch, pitchBlockedKey } from "./pitchBus.js";
+import { PITCH_MAX, PITCH_MIN, clampPitch, pitchBlockedKey, savedGlobalPitch } from "./pitchBus.js";
 
 function defaultMixerEntry() {
   // `pitch` is the key this lane is actually in, in semitones from the
@@ -98,6 +98,11 @@ export async function loadMixIntoState(jobId, loadedStemNames = STEM_NAMES) {
     const mode = _activeMode;
     stored = null;
     try {
+      // A change made a moment ago may still be waiting in the debounce:
+      // reading past it would open the song as it was before that change,
+      // and the late write would then put the change back in the store
+      // behind a screen and an engine that never had it (#781).
+      await storeFlushPending(mixKey(jobId, mode));
       stored = await storeGet(mixKey(jobId, mode), null);
       if (!stored && LEGACY_MODES.has(mode)) stored = await storeGet(legacyMixKey(jobId), null);
     } catch (e) { console.warn("[mixer] failed to load mix state:", e); }
@@ -110,7 +115,10 @@ export async function loadMixIntoState(jobId, loadedStemNames = STEM_NAMES) {
     if (!Array.isArray(mixerState[name].fx)) mixerState[name].fx = [];
   }
   mixerState[MASTER_SLOT] = masterEntry(stored[MASTER_SLOT]);
-  Object.assign(mixGlobals, cleanGlobals(stored.__global));
+  // The global key comes from the same record as the lanes it moved, so the
+  // counter can never disagree with what they play (a record without one is
+  // read from its lanes: savedGlobalPitch).
+  Object.assign(mixGlobals, cleanGlobals({ ...stored.__global, pitch: savedGlobalPitch(stored, loadedStemNames) }));
   // If all loaded stems are muted the session is unplayable -- unmute as recovery.
   const loadedStems = loadedStemNames.filter((n) => mixerState[n]);
   if (loadedStems.length > 0 && loadedStems.every((n) => mixerState[n].muted)) {

static/js/pitchBus.js

@@ -59,3 +59,39 @@ export function inputForPitch(semitones) {
 export function pitchBlockedKey() {
   return window.isSecureContext === false ? "pitch.insecureOrigin" : "pitch.unavailable";
 }
+
+/**
+ * The global key a song's saved record was left at.
+ *
+ * The record holds it under `__global.pitch`. A record from before the global
+ * key was saved (0.20 and earlier, `stemdeck:mix:<jobId>`) has only the lanes,
+ * which are absolute: the global control moved every lane but drums by the
+ * same amount. Opening one showed 0 on the counter over lanes still playing
+ * two semitones down (#781), so the key is read back from the lanes: the one
+ * most of the song's pitched lanes are in, the one nearer the original on a
+ * tie, and 0 when no lane says anything.
+ *
+ * `laneNames` are the lanes the song actually has; a record also holds every
+ * lane the app knows, at whatever the control last pushed them to.
+ */
+export function savedGlobalPitch(record, laneNames) {
+  const stored = record?.__global?.pitch;
+  if (Number.isFinite(stored)) return clampPitch(stored);
+  const counts = new Map();
+  for (const name of laneNames || []) {
+    if (name === "drums") continue;
+    const p = record?.[name]?.pitch;
+    if (!Number.isFinite(p)) continue;
+    const k = clampPitch(p);
+    counts.set(k, (counts.get(k) || 0) + 1);
+  }
+  let best = 0;
+  let bestCount = 0;
+  for (const [k, n] of counts) {
+    if (n > bestCount || (n === bestCount && Math.abs(k) < Math.abs(best))) {
+      best = k;
+      bestCount = n;
+    }
+  }
+  return best;
+}

static/js/player.js

@@ -1843,16 +1843,23 @@ export function wireUpAudio(jobId, stems, duration, thumbnail, mixUrl = null, ti
           // "playback failed" notification if one was sitting there (#401).
           resolvePlaybackSuccess(jobId);
           eng.setLoop(loopEnabled, loopStart, loopEnd);
-          updatePitchAvailability(eng.supportsPitchShift?.() === true);
-          applyMix(); // push per-stem gains (incl. >1.0 boost) into the engine
-          // Lane keys ride on the same engine, so they are restored from the
-          // per-track store in the same breath as the gains.
-          setLaneKeysAvailable(eng.supportsPitchShift?.() === true);
-          applyAllLanePitches();
-          // Saved EQs ride on the same engine and are restored with the keys.
-          applyAllLaneEq();
-          // And the speed and global key the song was left at, in this mode.
-          restoreGlobals();
+          // The song's saved record is the one source of what the engine and
+          // the screen show: gains, lane keys, EQs, and the speed and global
+          // key it was left at. The engine can come up before the record has
+          // been read (desktop reads it over IPC), and pushing what was in
+          // memory then left the engine and the counter on the defaults, or
+          // on the previous song, under the record's lanes (#781). So all of
+          // it waits for the record, and the key controls stay off until it
+          // is in, so a step cannot land on a key about to be replaced.
+          mixReady.then(() => {
+            if (token !== visualRenderToken || multitrack !== mt || audioEngine !== eng) return;
+            updatePitchAvailability(eng.supportsPitchShift?.() === true);
+            applyMix(); // push per-stem gains (incl. >1.0 boost) into the engine
+            setLaneKeysAvailable(eng.supportsPitchShift?.() === true);
+            applyAllLanePitches();
+            applyAllLaneEq();
+            restoreGlobals();
+          });
 
           // Click track. Bound to this engine instance, so it is rebuilt on
           // every engine bring-up (including the chunked -> fulldecode

tests/e2e/spec-map.json

@@ -86,7 +86,7 @@
         "static/js/modeUi.js", "static/js/mixMode.js", "static/js/modeStems.js", "static/js/partChoice.js",
         "static/js/stemChoice.js", "static/js/stemsControl.js", "static/js/playbackStems.js", "static/css/appbar.css"
       ],
-      "specs": ["modes", "help-mode", "mode-stems", "partial-stems", "extract-row", "stem-chip-overflow", "karaoke", "streamer", "streamer-media", "panel-toggles"]
+      "specs": ["modes", "help-mode", "mode-stems", "partial-stems", "extract-row", "stem-chip-overflow", "karaoke", "streamer", "streamer-media", "panel-toggles", "transpose-switch-song"]
     },
     {
       "why": "The import form: URL box, search, file drop, playlist import, and the stem choice submitted with it",
@@ -141,7 +141,7 @@
         "static/js/pitchBus.js", "static/js/tempoStage.js", "static/js/tickLoop.js", "static/js/keyLabel.js",
         "static/vendor/signalsmith-stretch.js", "static/vendor/soundtouch-processor.js"
       ],
-      "specs": ["tempo-stage", "slow-speed", "transpose", "mobile-transpose", "network-transpose-warning", "click-track", "count-in-replay", "key-card", "help-mode"]
+      "specs": ["tempo-stage", "slow-speed", "transpose", "transpose-switch-song", "mobile-transpose", "network-transpose-warning", "click-track", "count-in-replay", "key-card", "help-mode"]
     },
     {
       "why": "Footer and transport layout",
@@ -180,7 +180,7 @@
     {
       "why": "Karaoke mode",
       "paths": ["static/js/karaoke/**", "static/css/karaoke.css", "app/api/backing.py", "app/pipeline/backing.py"],
-      "specs": ["karaoke", "streamer", "modes", "help-mode", "mode-stems", "lyrics", "playback-memory", "track-header", "video-sync", "zoom"]
+      "specs": ["karaoke", "streamer", "modes", "help-mode", "mode-stems", "lyrics", "playback-memory", "track-header", "video-sync", "zoom", "transpose-switch-song"]
     },
     {
       "why": "Performance (streamer) mode",