fix: lag khi ARM sau reload + câm sau vài lần nhấn MIDI - dedup loadSoundFont (1 font=1 sfload, tránh cạn heap 256MB) + preload instrument khi mở/khôi phục dự án

app/static/js/app.jsx

@@ -4627,6 +4627,23 @@ const ProfileModal = ({
     }
   };
 
+  const preloadTrackInstruments = async (tracks) => {
+    // Preload each track's soundfont before the user plays — otherwise the first
+    // MIDI key after reload triggers a lazy font load and the note sounds late.
+    if (!window.SonicSF || !window.SonicSF.selectInstrument) return;
+    for (const t of (tracks || [])) {
+      const se = t.synth_engine;
+      const sfId = (se && se.soundfont_id) || t.soundfont_id;
+      if (!sfId) continue;
+      const bank = se ? (se.soundfont_bank !== undefined ? se.soundfont_bank : 0) : (t.soundfont_bank !== undefined ? t.soundfont_bank : 0);
+      const prog = se ? (se.soundfont_program !== undefined ? se.soundfont_program : 0) : (t.soundfont_program !== undefined ? t.soundfont_program : 0);
+      var ch = window.SonicPianoRoll ? window.SonicPianoRoll.getTrackMidiChannel(t, tracks) : (t.midiChannel !== undefined ? t.midiChannel : 0);
+      try {
+        await window.SonicSF.selectInstrument(ch, bank, prog, sfId);
+      } catch (e) {}
+    }
+  };
+
   const handleOpenProject = async (projectId, projectName) => {
     setAppWarningModal({
       title: "Mở dự án",
@@ -4685,6 +4702,7 @@ const ProfileModal = ({
           }
           setTracks(restoredTracks);
           loadAudioBuffersForTracks(restoredTracks).catch(function(err) { console.warn('loadAudioBuffersForTracks error:', err); });
+          preloadTrackInstruments(restoredTracks).catch(function(err) { console.warn('preloadTrackInstruments error:', err); });
           setBpm(restoredBpm.toString());
           setSelectedTrackId(restoredTracks[0]?.id || '1');
           setProjectName(proj.name);
@@ -12110,6 +12128,7 @@ const App = () => {
       }
       setTracks(restoredTracks);
       loadAudioBuffersForTracks(restoredTracks).catch(function(err) { console.warn('loadAudioBuffersForTracks error:', err); });
+      preloadTrackInstruments(restoredTracks).catch(function(err) { console.warn('preloadTrackInstruments error:', err); });
       setBpm(restoredBpm.toString());
       setSelectedTrackId(restoredTracks[0]?.id || '1');
       setProjectName(lastName);

app/static/js/services/soundfontPlayer.js

@@ -23,6 +23,8 @@
     let _activeOscillators = {};
     let _gainNode = null;
     let _scheduledNotes = [];
+    let _loadPromises = {};
+    let _sfloadSeq = 0;
 
     const getCtx = function () {
         if (_audioCtx) {
@@ -186,7 +188,7 @@
         },
 
         _tryLoadSFL: function (buf, ext) {
-            var fname = '/' + ext + '_' + Date.now();
+            var fname = '/' + ext + '_' + (++_sfloadSeq) + '_' + Date.now();
             try { _fluidModule.FS.unlink(fname); } catch (e) {}
             _fluidModule.FS.writeFile(fname, new Uint8Array(buf));
             var cPath = this._allocCStr(fname);
@@ -203,6 +205,18 @@
                 _currentSfId = sfId;
                 return true;
             }
+            // Deduplicate concurrent loads: rapid key presses (or several armed
+            // tracks) all call loadSoundFont for the same font before the first
+            // load resolves. Without this, the same soundfont is sfload'd several
+            // times (handles 1,2,3,4…) — wasting the 256MB WASM heap and stalling
+            // notes until each load finishes (audible lag, then silence).
+            if (!_loadPromises[sfId]) {
+                _loadPromises[sfId] = this._doLoadSoundFont(sfId);
+            }
+            return _loadPromises[sfId];
+        },
+
+        _doLoadSoundFont: async function (sfId) {
             try {
                 var cache = window.SonicSFStorage;
                 var buf = cache ? await cache.getBuffer(sfId) : null;