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

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;
+}