two new fade types + modified linter to be less cancer

eslint.config.js

@@ -37,14 +37,15 @@ export default defineConfig([
       // Variables
       'no-var': 'error',
       'prefer-const': 'error',
+      '@typescript-eslint/no-unused-vars': ['error', { varsIgnorePattern: '^_', argsIgnorePattern: '^_' }],
 
       // Naming conventions
       '@typescript-eslint/naming-convention': [
         'error',
         {
           selector: 'default',
           format: ['camelCase'],
-          leadingUnderscore: 'forbid',
+          leadingUnderscore: 'allow',
           trailingUnderscore: 'forbid',
         },
         {

src/audio/PlaylistManager.ts

@@ -1,4 +1,5 @@
 import type { Fade } from '../../types/Fade';
+import { FadeType } from '../../types/Fade';
 import type { ID, Seconds, PlaylistEntry, Transition, ScheduledEntry } from './types';
 
 /**
@@ -118,7 +119,7 @@ export class PlaylistManager {
       if (i > 0) {
         const prevEntry = this.entries[i - 1];
         const incomingTransition = this.getTransitionBetween(prevEntry.id, entry.id);
-        if (incomingTransition) {
+        if (incomingTransition && incomingTransition.fadeInType !== FadeType.NONE) {
           fades.push({
             type: incomingTransition.fadeInType,
             startOffset: 0,
@@ -133,7 +134,7 @@ export class PlaylistManager {
       if (i < this.entries.length - 1) {
         const nextEntry = this.entries[i + 1];
         const outgoingTransition = this.getTransitionBetween(entry.id, nextEntry.id);
-        if (outgoingTransition) {
+        if (outgoingTransition && outgoingTransition.fadeOutType !== FadeType.NONE) {
           fades.push({
             type: outgoingTransition.fadeOutType,
             startOffset: entry.duration - outgoingTransition.duration,

src/audio/Scheduler.ts

@@ -11,6 +11,17 @@ const SCHEDULE_AHEAD_S: Seconds = 0.2;
 /** grace period, nodes within this window of ctx.currentTime are considered "audible" */
 const AUDIBLE_GRACE_S = 0.05;
 
+const EQUAL_POWER_CURVE_LENGTH = 128;
+
+// fade-out: cos(t * pi/2), 1 -> 0
+const EQUAL_POWER_FADE_OUT = new Float32Array(EQUAL_POWER_CURVE_LENGTH).map((_, i) =>
+  Math.cos((i / (EQUAL_POWER_CURVE_LENGTH - 1)) * (Math.PI / 2)),
+);
+// fade-in: sin(t * pi/2), 0 -> 1
+const EQUAL_POWER_FADE_IN = new Float32Array(EQUAL_POWER_CURVE_LENGTH).map((_, i) =>
+  Math.sin((i / (EQUAL_POWER_CURVE_LENGTH - 1)) * (Math.PI / 2)),
+);
+
 /**
  * Look-ahead scheduler
  *
@@ -385,6 +396,13 @@ export class Scheduler {
 
       if (fade.type === FadeType.LINEAR) {
         gainNode.gain.linearRampToValueAtTime(Math.max(fade.endGain, 0.0001), fadeEndCtx);
+      } else if (fade.type === FadeType.EQUAL_POWER) {
+        const isFadeIn = fade.endGain > fade.startGain;
+        const fullCurve = isFadeIn ? EQUAL_POWER_FADE_IN : EQUAL_POWER_FADE_OUT;
+        // slice from the fraction we've already passed (mid-fade seek)
+        const startIdx = Math.round(fadeFraction * (EQUAL_POWER_CURVE_LENGTH - 1));
+        const curve = startIdx > 0 ? fullCurve.slice(startIdx) : fullCurve;
+        gainNode.gain.setValueCurveAtTime(curve, fadeStartCtx, fadeEndCtx - fadeStartCtx);
       } else {
         // exponentialRamp can't reach 0, so we use an epsilon
         gainNode.gain.exponentialRampToValueAtTime(Math.max(fade.endGain, 0.0001), fadeEndCtx);

types/Fade.ts

@@ -1,8 +1,10 @@
 import type {Seconds, Gain} from "./UtilTypes"
 
 export const FadeType = {
-    LINEAR: 0,
-    EXPONENTIAL: 1,
+    NONE: 0,
+    LINEAR: 1,
+    EXPONENTIAL: 2,
+    EQUAL_POWER: 3,
 } as const;
 
 export type FadeType = (typeof FadeType)[keyof typeof FadeType];