fix: brush scroll speed + CC snap + non-selected flicker

app/static/js/app.jsx

@@ -5250,7 +5250,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
             brushAutoScrollRef.current = {
               direction: 'up',
               id: setInterval(() => {
-                if (gridScrollRef.current) gridScrollRef.current.scrollTop = Math.max(0, gridScrollRef.current.scrollTop - NoteHeight * 2);
+                if (gridScrollRef.current) gridScrollRef.current.scrollTop = Math.max(0, gridScrollRef.current.scrollTop - Math.max(1, Math.floor(NoteHeight * 0.5)));
               }, 30)
             };
           }
@@ -5260,7 +5260,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
             brushAutoScrollRef.current = {
               direction: 'down',
               id: setInterval(() => {
-                if (gridScrollRef.current) gridScrollRef.current.scrollTop = Math.min(gridScrollRef.current.scrollHeight - gridScrollRef.current.clientHeight, gridScrollRef.current.scrollTop + NoteHeight * 2);
+                if (gridScrollRef.current) gridScrollRef.current.scrollTop = Math.min(gridScrollRef.current.scrollHeight - gridScrollRef.current.clientHeight, gridScrollRef.current.scrollTop + Math.max(1, Math.floor(NoteHeight * 0.5)));
               }, 30)
             };
           }
@@ -5376,12 +5376,13 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
     const h = rect.height;
     const beat = x / pixelsPerBeat;
 
-    let noteIdx = notes.findIndex(n => beat >= n.start_beat && beat <= n.start_beat + n.duration_beats);
+    const snappedBeat = getSnapBeat(beat, snapVal);
+    let noteIdx = notes.findIndex(n => snappedBeat >= n.start_beat && snappedBeat <= n.start_beat + n.duration_beats);
     if (noteIdx === -1) {
       let minDistance = Infinity;
       notes.forEach((n, idx) => {
         const center = n.start_beat + n.duration_beats / 2;
-        const dist = Math.abs(center - beat);
+        const dist = Math.abs(center - snappedBeat);
         if (dist < minDistance) {
           minDistance = dist;
           noteIdx = idx;
@@ -5390,14 +5391,6 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
     }
 
     const val = Math.max(0, Math.min(1, (h - y) / h));
-    const paintNote = (idx, v) => {
-      if (idx === -1) return;
-      setNotes(prev => prev.map((n, i) => {
-        if (i !== idx) return n;
-        if (ccMode === 'pan') { return { ...n, pan: (v - 0.5) * 2.0 }; }
-        return { ...n, velocity: v };
-      }));
-    };
 
     if (e.ctrlKey) {
       if (selectedNoteIds.length > 0) {
@@ -5421,13 +5414,18 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
           ccDragRef.current = { active: true, lastBeat: beat, selectedMode: true, lastPainted: [] };
         }
       } else {
-        if (noteIdx !== -1) paintNote(noteIdx, val);
         ccDragRef.current = { active: true, lastBeat: beat, lastPainted: noteIdx !== -1 ? [noteIdx] : [] };
       }
       return;
     }
 
-    if (noteIdx !== -1) paintNote(noteIdx, val);
+    if (noteIdx !== -1) {
+      setNotes(prev => prev.map((n, i) => {
+        if (i !== noteIdx) return n;
+        if (ccMode === 'pan') return { ...n, pan: (val - 0.5) * 2.0 };
+        return { ...n, velocity: val };
+      }));
+    }
   };
 
   const handleCCMouseMove = (e) => {
@@ -5468,7 +5466,8 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
       return;
     }
 
-    const candidateIdx = notes.findIndex(n => beat >= n.start_beat && beat <= n.start_beat + n.duration_beats);
+    const snappedBeat = getSnapBeat(beat, snapVal);
+    const candidateIdx = notes.findIndex(n => snappedBeat >= n.start_beat && snappedBeat <= n.start_beat + n.duration_beats);
 
     if (candidateIdx !== -1 && !painted.includes(candidateIdx)) {
       setNotes(prev => prev.map((n, i) => {
@@ -5482,7 +5481,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
       let minDist = Infinity;
       notes.forEach((n, idx) => {
         const center = n.start_beat + n.duration_beats / 2;
-        const d = Math.abs(center - beat);
+        const d = Math.abs(center - snappedBeat);
         if (d < minDist) { minDist = d; nearest = idx; }
       });
       if (nearest !== -1 && !painted.includes(nearest)) {

wiki.md

@@ -28,6 +28,11 @@
 - **Ghi chú/Test (nếu có):** `npm run build` pass. Thay `lastPainted` trong selectedMode từ array all indices thành array single-node index.
 ---
 
+### [2026-07-26 10:20] Task: Fix brush scroll speed + CC snap + non-selected flicker
+- **Tóm tắt thay đổi:** (1) Giảm auto-scroll step từ `NoteHeight * 2` xuống `max(1, floor(NoteHeight * 0.5))` — cuộn chậm hơn để draw note đúng pitch. (2) CC lane `handleCCMouseDown` và `handleCCMouseMove` dùng `getSnapBeat(beat, snapVal)` khi tìm note index — snap đúng grid. (3) Non-selected CC flicker: xóa `paintNote` helper, inline `setNotes` trực tiếp trong mousedown, không gọi setNotes riêng lẻ gây re-render dư thừa.
+- **Các file ảnh hưởng:** `app/static/js/app.jsx`
+- **Ghi chú/Test (nếu có):** `npm run build` pass.
+
 ### [2026-07-25 07:25] Task: Fix auto-scroll + maxDuration tab isolation + 1-bar margin
 - **Tóm tắt thay đổi:** (1) `maxDuration` dùng `activeTracks` + 4-bar buffer. (2) Cách ly MAIN vs SECTION-TAB. (3) Clip/section/MIDI drag/stretch/resize clamp 1-bar from right. (4) Clip drag + stretched clip dùng `updateActiveTracks`. (5) Stretched clip handler thêm auto-scroll.
 - **Các file ảnh hưởng:** `app/static/js/app.jsx`