feat: switch track volume to dB scale with Logic Pro-style fader (−∞dB ~ +12dB)

src/components/track/Track.css

@@ -51,7 +51,7 @@
 .track-info {
   width: 200px;
   height: 120px;
-  padding: 15px;
+  padding: 15px 5px 15px 15px;
   background-color: #2d2d2d;
   display: flex;
   flex-direction: column;
@@ -155,6 +155,34 @@
   gap: 6px;
 }
 
+.volume-slider .volume-label {
+  flex-shrink: 0;
+  font-size: 9px;
+  color: #aaa;
+  min-width: 22px;
+  text-align: left;
+  white-space: nowrap;
+  font-variant-numeric: tabular-nums;
+}
+
+.volume-slider .volume-label-clickable {
+  cursor: pointer;
+}
+
+.volume-slider .volume-label-clickable:hover {
+  color: #ddd;
+}
+
+.volume-slider .volume-label-input {
+  background: #2a2a2a;
+  border: 1px solid #555;
+  border-radius: 3px;
+  color: #e0e0e0;
+  padding: 0 2px;
+  width: 36px;
+  outline: none;
+}
+
 .volume-slider input[type="range"] {
   flex: 1;
   min-width: 0;

src/components/track/TrackInfoItem.tsx

@@ -13,6 +13,35 @@ import { DEBUG_MODE } from '../../constants/uiConstants';
 import { KGAudioInterface } from '../../core/audio-interface/KGAudioInterface';
 import { AUDIO_INTERFACE_CONSTANTS } from '../../constants/coreConstants';
 import { showAlert, showConfirm, showPrompt } from '../common/DialogProvider';
+
+const UNITY_POS = 750;
+const SLIDER_MAX = 1000;
+
+function sliderToDb(pos: number): number {
+  const MIN = AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB;
+  const MAX = AUDIO_INTERFACE_CONSTANTS.MAX_TRACK_VOLUME_DB;
+  if (pos <= 0) return MIN;
+  if (pos >= SLIDER_MAX) return MAX;
+  if (pos <= UNITY_POS) {
+    const t = pos / UNITY_POS;
+    return MIN * (1 - t * t);
+  }
+  return MAX * (pos - UNITY_POS) / (SLIDER_MAX - UNITY_POS);
+}
+
+function dbToSlider(db: number): number {
+  const MIN = AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB;
+  const MAX = AUDIO_INTERFACE_CONSTANTS.MAX_TRACK_VOLUME_DB;
+  if (db <= MIN) return 0;
+  if (db >= MAX) return SLIDER_MAX;
+  if (db <= 0) return Math.round(Math.sqrt(1 - db / MIN) * UNITY_POS);
+  return Math.round(UNITY_POS + (db / MAX) * (SLIDER_MAX - UNITY_POS));
+}
+
+function formatDb(db: number): string {
+  if (db <= AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB) return '−∞';
+  return `${db >= 0 ? '+' : ''}${db.toFixed(1)}`;
+}
 interface TrackInfoItemProps {
   track: KGTrack;
   index: number;
@@ -56,6 +85,9 @@ const TrackInfoItem: React.FC<TrackInfoItemProps> = ({
   const settingsDropdownRef = useRef<HTMLDivElement>(null);
   const suppressDragRef = useRef(false);
   const [volume, setVolume] = useState(track.getVolume());
+  const [isEditingVolume, setIsEditingVolume] = useState(false);
+  const [volumeInputText, setVolumeInputText] = useState('');
+  const volumeInputRef = useRef<HTMLInputElement>(null);
   // Local flag to track slider interaction; not used for rendering
   const isAdjustingVolumeRef = useRef(false);
   const [muted, setMuted] = useState(false);
@@ -129,11 +161,10 @@ const TrackInfoItem: React.FC<TrackInfoItemProps> = ({
 
   const handleVolumeChange = (e: React.ChangeEvent<HTMLInputElement>) => {
     e.stopPropagation();
-    const next = Number(e.target.value) / 100;
+    const next = sliderToDb(Number(e.target.value));
     isAdjustingVolumeRef.current = true;
     setVolume(next);
     try {
-      // Live preview: update audio only while sliding
       KGAudioInterface.instance().setTrackVolume(track.getId().toString(), next);
     } catch (err) {
       console.error('Failed to update live volume:', err);
@@ -167,6 +198,43 @@ const TrackInfoItem: React.FC<TrackInfoItemProps> = ({
     }
   };
 
+  const handleVolumeLabelClick = (e: React.MouseEvent) => {
+    e.stopPropagation();
+    const displayText = volume <= AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB
+      ? '-60'
+      : volume.toFixed(1);
+    setVolumeInputText(displayText);
+    setIsEditingVolume(true);
+    setTimeout(() => {
+      volumeInputRef.current?.select();
+    }, 0);
+  };
+
+  const commitVolumeLabelInput = () => {
+    setIsEditingVolume(false);
+    const parsed = parseFloat(volumeInputText);
+    if (isNaN(parsed)) return;
+    const clamped = Math.max(
+      AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB,
+      Math.min(AUDIO_INTERFACE_CONSTANTS.MAX_TRACK_VOLUME_DB, parsed)
+    );
+    setVolume(clamped);
+    try {
+      useProjectStore.getState().updateTrackProperties(track.getId(), { volume: clamped });
+    } catch (err) {
+      console.error('Failed to set volume from label input:', err);
+    }
+  };
+
+  const handleVolumeLabelKeyDown = (e: React.KeyboardEvent<HTMLInputElement>) => {
+    if (e.key === 'Enter') {
+      e.preventDefault();
+      commitVolumeLabelInput();
+    } else if (e.key === 'Escape') {
+      setIsEditingVolume(false);
+    }
+  };
+
   const handleToggleMute = (e: React.MouseEvent<HTMLButtonElement>) => {
     e.stopPropagation();
     const next = !muted;
@@ -302,8 +370,9 @@ const TrackInfoItem: React.FC<TrackInfoItemProps> = ({
               <input
                 type="range"
                 min="0"
-                max="100"
+                max="1000"
-                value={Math.round(volume * 100)}
+                step="1"
+                value={dbToSlider(volume)}
                 onChange={handleVolumeChange}
                 onMouseDown={(e) => { e.stopPropagation(); isAdjustingVolumeRef.current = true; }}
                 onMouseUp={(e) => { e.stopPropagation(); commitVolumeChange(); }}
@@ -314,12 +383,32 @@ const TrackInfoItem: React.FC<TrackInfoItemProps> = ({
               />
               <button
                 className="reset-volume"
-                title="Reset volume"
+                title="Reset to 0 dB"
-                aria-label="Reset volume"
+                aria-label="Reset volume to 0 dB"
                 onClick={handleResetVolume}
               >
                 ↺
               </button>
+              {isEditingVolume ? (
+                <input
+                  ref={volumeInputRef}
+                  className="volume-label volume-label-input"
+                  type="text"
+                  value={volumeInputText}
+                  onChange={(e) => setVolumeInputText(e.target.value)}
+                  onKeyDown={handleVolumeLabelKeyDown}
+                  onBlur={commitVolumeLabelInput}
+                  onClick={(e) => e.stopPropagation()}
+                />
+              ) : (
+                <span
+                  className="volume-label volume-label-clickable"
+                  title="Click to enter dB value"
+                  onClick={handleVolumeLabelClick}
+                >
+                  {formatDb(volume)}
+                </span>
+              )}
             </div>
           </div>
         </div>

src/constants/coreConstants.ts

@@ -63,7 +63,9 @@ export const KEY_SIGNATURE_MAP = {
 
 export const AUDIO_INTERFACE_CONSTANTS = {
   DEFAULT_MASTER_VOLUME: 0.8,
-  DEFAULT_TRACK_VOLUME: 0.8,
+  DEFAULT_TRACK_VOLUME: 0,   // 0 dB (unity gain)
+  MIN_TRACK_VOLUME_DB: -60,  // practical floor; displayed as −∞
+  MAX_TRACK_VOLUME_DB: 12,
 };
 
 export const SAMPLER_CONSTANTS = {

src/core/KGProject.ts

@@ -52,7 +52,7 @@ export class KGProject {
   @WithDefault(0)
   private projectStructureVersion: number = 0;
 
-  public static readonly CURRENT_PROJECT_STRUCTURE_VERSION: number = 6;
+  public static readonly CURRENT_PROJECT_STRUCTURE_VERSION: number = 7;
   
   @Expose()
   @Type(() => KGTrack, {

src/core/audio-interface/KGAudioBus.ts

@@ -283,9 +283,8 @@ export class KGAudioBus {
    */
   private updateSamplerVolume(): void {
     try {
-      const effectiveVolume = this.muted ? 0 : this.volume;
+      const isSilent = this.muted || this.volume <= AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB;
-      const volumeDb = effectiveVolume > 0 ? 20 * Math.log10(effectiveVolume) : -Infinity;
+      this.sampler.volume.value = isSilent ? -Infinity : this.volume;
-      this.sampler.volume.value = volumeDb;
     } catch (error) {
       console.error(`Error updating volume for ${this.instrument}:`, error);
     }
@@ -297,14 +296,8 @@ export class KGAudioBus {
    */
   public applyEffectiveVolume(hasSoloedTracks: boolean): void {
     try {
-      let effectiveVolume = this.volume;
+      const isSilent = this.muted || (hasSoloedTracks && !this.solo) || this.volume <= AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB;
-      if (this.muted) {
+      this.sampler.volume.value = isSilent ? -Infinity : this.volume;
-        effectiveVolume = 0;
-      } else if (hasSoloedTracks && !this.solo) {
-        effectiveVolume = 0;
-      }
-      const volumeDb = effectiveVolume > 0 ? 20 * Math.log10(effectiveVolume) : -Infinity;
-      this.sampler.volume.value = volumeDb;
     } catch (error) {
       console.error(`Error applying effective volume for ${this.instrument}:`, error);
     }

src/core/audio-interface/KGAudioPlayerBus.ts

@@ -200,14 +200,8 @@ export class KGAudioPlayerBus {
    */
   public applyEffectiveVolume(hasSoloedTracks: boolean): void {
     try {
-      let effectiveVolume = this.volume;
+      const isSilent = this.muted || (hasSoloedTracks && !this.solo) || this.volume <= AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB;
-      if (this.muted) {
+      this.gainNode.gain.value = isSilent ? 0 : Math.pow(10, this.volume / 20);
-        effectiveVolume = 0;
-      } else if (hasSoloedTracks && !this.solo) {
-        effectiveVolume = 0;
-      }
-      const volumeDb = effectiveVolume > 0 ? 20 * Math.log10(effectiveVolume) : -Infinity;
-      this.gainNode.gain.value = Math.pow(10, volumeDb / 20);
     } catch (error) {
       console.error('Error applying effective volume for audio player bus:', error);
     }
@@ -266,9 +260,8 @@ export class KGAudioPlayerBus {
 
   private updateGainVolume(): void {
     try {
-      const effectiveVolume = this.muted ? 0 : this.volume;
+      const isSilent = this.muted || this.volume <= AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB;
-      // Convert linear volume to gain value
+      this.gainNode.gain.value = isSilent ? 0 : Math.pow(10, this.volume / 20);
-      this.gainNode.gain.value = effectiveVolume;
     } catch (error) {
       console.error('Error updating gain volume:', error);
     }

src/core/project-upgrader/KGProjectUpgrader.ts

@@ -5,6 +5,7 @@ import { upgradeToV3 } from './upgradeToV3';
 import { upgradeToV4 } from './upgradeToV4';
 import { upgradeToV5 } from './upgradeToV5';
 import { upgradeToV6 } from './upgradeToV6';
+import { upgradeToV7 } from './upgradeToV7';
 
 /**
  * Upgrade the given project to the latest structure version, one version at a time.
@@ -48,6 +49,10 @@ export function upgradeProjectToLatest(project: KGProject): KGProject {
         workingProject = upgradeToV6(workingProject);
         break;
       }
+      case 7: {
+        workingProject = upgradeToV7(workingProject);
+        break;
+      }
       default: {
         // If an upgrader is missing, throw to prevent loading incompatible structures
         throw new Error(`No upgrader found for project structure version ${nextVersion}`);

src/core/project-upgrader/upgradeToV7.test.ts

@@ -0,0 +1,64 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { KGProject } from '../KGProject';
+import { KGMidiTrack } from '../track/KGMidiTrack';
+import { upgradeToV7 } from './upgradeToV7';
+import { AUDIO_INTERFACE_CONSTANTS } from '../../constants/coreConstants';
+
+function makeProject(volumes: number[]): KGProject {
+  const tracks = volumes.map((v, i) => {
+    const track = new KGMidiTrack(`Track ${i}`, i);
+    // Bypass setVolume clamping to simulate old 0–1 linear values stored in JSON
+    (track as unknown as { volume: number }).volume = v;
+    return track;
+  });
+  const project = new KGProject('Test', 32, 0, 125, undefined, undefined, undefined, undefined, undefined, undefined, tracks, 6);
+  return project;
+}
+
+describe('upgradeToV7', () => {
+  it('converts 1.0 linear to 0 dB', () => {
+    const project = makeProject([1.0]);
+    upgradeToV7(project);
+    expect(project.getTracks()[0].getVolume()).toBeCloseTo(0, 5);
+  });
+
+  it('converts 0.8 linear to ~−1.94 dB', () => {
+    const project = makeProject([0.8]);
+    upgradeToV7(project);
+    expect(project.getTracks()[0].getVolume()).toBeCloseTo(20 * Math.log10(0.8), 3);
+  });
+
+  it('converts 0.5 linear to ~−6.02 dB', () => {
+    const project = makeProject([0.5]);
+    upgradeToV7(project);
+    expect(project.getTracks()[0].getVolume()).toBeCloseTo(-6.021, 2);
+  });
+
+  it('converts 0.0 linear to MIN_TRACK_VOLUME_DB', () => {
+    const project = makeProject([0.0]);
+    upgradeToV7(project);
+    expect(project.getTracks()[0].getVolume()).toBe(AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB);
+  });
+
+  it('clamps values that exceed MAX_TRACK_VOLUME_DB', () => {
+    // linear > 1.0 would give positive dB; cap at +6
+    const project = makeProject([2.0]);
+    upgradeToV7(project);
+    expect(project.getTracks()[0].getVolume()).toBe(AUDIO_INTERFACE_CONSTANTS.MAX_TRACK_VOLUME_DB);
+  });
+
+  it('bumps project structure version to 7', () => {
+    const project = makeProject([1.0]);
+    upgradeToV7(project);
+    expect(project.getProjectStructureVersion()).toBe(7);
+  });
+
+  it('handles multiple tracks independently', () => {
+    const project = makeProject([1.0, 0.5, 0.0]);
+    upgradeToV7(project);
+    const tracks = project.getTracks();
+    expect(tracks[0].getVolume()).toBeCloseTo(0, 5);
+    expect(tracks[1].getVolume()).toBeCloseTo(-6.021, 2);
+    expect(tracks[2].getVolume()).toBe(AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB);
+  });
+});

src/core/project-upgrader/upgradeToV7.ts

@@ -0,0 +1,23 @@
+import { KGProject } from '../KGProject';
+import { AUDIO_INTERFACE_CONSTANTS } from '../../constants/coreConstants';
+
+export function upgradeToV7(project: KGProject): KGProject {
+  try {
+    // Convert track volumes from 0–1 linear scale to dB
+    for (const track of project.getTracks()) {
+      const linear = track.getVolume();
+      let db: number;
+      if (linear <= 0) {
+        db = AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB;
+      } else {
+        db = 20 * Math.log10(linear);
+        db = Math.max(AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB,
+             Math.min(AUDIO_INTERFACE_CONSTANTS.MAX_TRACK_VOLUME_DB, db));
+      }
+      track.setVolume(db);
+    }
+  } finally {
+    project.setProjectStructureVersion(7);
+  }
+  return project;
+}

src/core/track/KGMidiTrack.test.ts

@@ -19,18 +19,18 @@ describe('KGMidiTrack', () => {
       expect(defaultTrack.getId()).toBe(0)
       expect(defaultTrack.getType()).toBe(TrackType.MIDI)
       expect(defaultTrack.getInstrument()).toBe('acoustic_grand_piano')
-      expect(defaultTrack.getVolume()).toBe(0.8) // DEFAULT_TRACK_VOLUME
+      expect(defaultTrack.getVolume()).toBe(0) // DEFAULT_TRACK_VOLUME (0 dB)
       expect(defaultTrack.getRegions()).toEqual([])
     })
 
     it('should create track with custom parameters', () => {
-      const customTrack = new KGMidiTrack('My Piano Track', 5, 'electric_piano_1', 0.6)
+      const customTrack = new KGMidiTrack('My Piano Track', 5, 'electric_piano_1', -4)
 
       expect(customTrack.getName()).toBe('My Piano Track')
       expect(customTrack.getId()).toBe(5)
       expect(customTrack.getType()).toBe(TrackType.MIDI)
       expect(customTrack.getInstrument()).toBe('electric_piano_1')
-      expect(customTrack.getVolume()).toBe(0.6)
+      expect(customTrack.getVolume()).toBe(-4)
     })
 
     it('should set correct type identifier', () => {
@@ -193,33 +193,33 @@ describe('KGMidiTrack', () => {
 
   describe('inheritance from KGTrack', () => {
     it('should inherit all base track properties', () => {
-      const customTrack = new KGMidiTrack('Test Track', 42, 'violin', 0.9)
+      const customTrack = new KGMidiTrack('Test Track', 42, 'violin', -1)
 
       expect(customTrack.getName()).toBe('Test Track')
       expect(customTrack.getId()).toBe(42)
       expect(customTrack.getType()).toBe(TrackType.MIDI)
-      expect(customTrack.getVolume()).toBe(0.9)
+      expect(customTrack.getVolume()).toBe(-1)
     })
 
     it('should inherit base track setters', () => {
       track.setName('Updated Track')
       expect(track.getName()).toBe('Updated Track')
 
-      track.setVolume(0.5)
+      track.setVolume(-6)
-      expect(track.getVolume()).toBe(0.5)
+      expect(track.getVolume()).toBe(-6)
 
       track.setTrackIndex(3)
       expect(track.getTrackIndex()).toBe(3)
     })
 
     it('should inherit volume controls', () => {
-      expect(track.getVolume()).toBe(0.8) // Default volume
+      expect(track.getVolume()).toBe(0) // Default volume (0 dB)
 
-      track.setVolume(0.5)
+      track.setVolume(-6)
-      expect(track.getVolume()).toBe(0.5)
+      expect(track.getVolume()).toBe(-6)
 
-      track.setVolume(1.0)
+      track.setVolume(0)
-      expect(track.getVolume()).toBe(1.0)
+      expect(track.getVolume()).toBe(0)
     })
   })
 
@@ -275,8 +275,8 @@ describe('KGMidiTrack', () => {
       // Setup initial state
       track.setName('Piano Track')
       track.setInstrument('acoustic_grand_piano')
-      track.setVolume(0.7)
+      track.setVolume(-3)
-      
+
       const regions = [
         createMockMidiRegion({ id: 'r1', trackId: '0', name: 'Intro' }),
         createMockMidiRegion({ id: 'r2', trackId: '0', name: 'Verse' })
@@ -286,21 +286,21 @@ describe('KGMidiTrack', () => {
       // Verify initial state
       expect(track.getName()).toBe('Piano Track')
       expect(track.getInstrument()).toBe('acoustic_grand_piano')
-      expect(track.getVolume()).toBe(0.7)
+      expect(track.getVolume()).toBe(-3)
       expect(track.getRegions()).toHaveLength(2)
 
       // Modify state
       track.setInstrument('electric_piano_1')
-      track.addRegion(createMockMidiRegion({ 
+      track.addRegion(createMockMidiRegion({
-        id: 'r3', 
+        id: 'r3',
-        trackId: '0', 
+        trackId: '0',
-        name: 'Chorus' 
+        name: 'Chorus'
       }))
 
       // Verify modified state
       expect(track.getName()).toBe('Piano Track')
       expect(track.getInstrument()).toBe('electric_piano_1')
-      expect(track.getVolume()).toBe(0.7)
+      expect(track.getVolume()).toBe(-3)
       expect(track.getRegions()).toHaveLength(3)
     })
 
@@ -337,15 +337,21 @@ describe('KGMidiTrack', () => {
     })
 
     it('should handle volume boundaries', () => {
-      track.setVolume(0.0)
+      track.setVolume(-60)
-      expect(track.getVolume()).toBe(0.0)
+      expect(track.getVolume()).toBe(-60)
 
-      track.setVolume(1.0)
+      track.setVolume(0)
-      expect(track.getVolume()).toBe(1.0)
+      expect(track.getVolume()).toBe(0)
 
-      // Volume outside normal range (should still work)
+      track.setVolume(6)
-      track.setVolume(1.5)
+      expect(track.getVolume()).toBe(6)
-      expect(track.getVolume()).toBe(1.5)
+
+      // Volume outside valid dB range is clamped
+      track.setVolume(10)
+      expect(track.getVolume()).toBe(6)
+
+      track.setVolume(-100)
+      expect(track.getVolume()).toBe(-60)
     })
 
     it('should handle large number of regions', () => {

src/core/track/KGTrack.ts

@@ -104,7 +104,10 @@ export class KGTrack {
   }
 
   public setVolume(volume: number): void {
-    this.volume = volume;
+    this.volume = Math.max(
+      AUDIO_INTERFACE_CONSTANTS.MIN_TRACK_VOLUME_DB,
+      Math.min(AUDIO_INTERFACE_CONSTANTS.MAX_TRACK_VOLUME_DB, volume)
+    );
   }
 
   public setRegions(regions: KGRegion[]): void {