Compute virtual keyboard frequencies and cents

Fixes issues when accessing outside the pre-computed range.

ref #696

src/components/VirtualKeyboard.vue

@@ -2,6 +2,7 @@
 import { computed, ref } from 'vue'
 import VirtualKeyboardKey from '@/components/VirtualKeyboardKey.vue'
 import VirtualKeyInfo from '@/components/VirtualKeyInfo.vue'
+import type { Scale } from '@/scale'
 
 type NoteOff = () => void
 type NoteOnCallback = (index: number) => NoteOff
@@ -10,14 +11,11 @@ type LabelMap = (index: number) => string
 
 const props = defineProps<{
   baseIndex: number // Should incorporate equave shift
-  baseMidiNote: number
   isomorphicHorizontal: number
   isomorphicVertical: number
   noteOn: NoteOnCallback
   heldNotes: Map<number, number>
-  baseFrequency: number
-  frequencies: number[]
-  centss: number[]
+  scale: Scale
   colorMap: ColorMap
   labelMap: LabelMap
   showLabel: boolean
@@ -41,15 +39,14 @@ const virtualKeys = computed(() => {
   const horizontal = props.isomorphicHorizontal
   const vertical = props.isomorphicVertical
   const result: [number, VirtualKey[]][] = []
-  const inverseBaseFreq = 1 / props.baseFrequency
   for (let y = 3; y >= -1; y--) {
     const row = []
     for (let x = 0; x <= 12; ++x) {
       const index = props.baseIndex + x * horizontal + y * vertical
       const color = props.colorMap(index)
-      const frequency = props.frequencies[index]
-      const cents = props.centss[index]
-      const ratio = frequency * inverseBaseFreq
+      const ratio = props.scale.getRatio(index)
+      const frequency = props.scale.baseFrequency * ratio
+      const cents = props.scale.getCents(index)
       const label = props.labelMap(index)
       row.push({
         x,

src/scale.ts

@@ -39,7 +39,7 @@ export class Scale {
   }
 
   /**
-   * Obtain the ratio agains the base MIDI note.
+   * Obtain the ratio against the base MIDI note.
    * @param index MIDI index of a note.
    * @returns Ratio associated with the MIDI index.
    */
@@ -63,6 +63,24 @@ export class Scale {
     return this.baseFrequency * this.getRatio(index)
   }
 
+  /**
+   * Obtain the cents offset from the base MIDI note.
+   * @param index MIDI index of a note.
+   * @returns Cents associated with the MIDI index.
+   */
+  getCents(index: number) {
+    // Deal with implicit 0c
+    index -= 1
+    // Center on base MIDI note
+    index -= this.baseMidiNote
+
+    const baseIndex = mmod(index, this.size)
+    const numEquaves = (index - baseIndex) / this.size
+    return (
+      valueToCents(this.intervalRatios[baseIndex]) + valueToCents(this.equaveRatio) * numEquaves
+    )
+  }
+
   /**
    * Obtain a range of frequencies in the scale.
    * More efficient to compute than getting individual frequencies.

src/views/VirtualKeyboardView.vue

@@ -38,15 +38,12 @@ type NoteOnCallback = (index: number) => NoteOff
     <VirtualKeyboard
       v-else
       :baseIndex="baseIndex"
-      :baseMidiNote="scale.scale.baseMidiNote"
       :isomorphicHorizontal="state.isomorphicHorizontal"
       :isomorphicVertical="state.isomorphicVertical"
       :colorMap="scale.colorForIndex"
       :noteOn="noteOn"
       :heldNotes="state.heldNotes"
-      :baseFrequency="scale.scale.baseFrequency"
-      :frequencies="scale.frequencies"
-      :centss="scale.centss"
+      :scale="scale.scale"
       :labelMap="scale.labelForIndex"
       :showLabel="state.showKeyboardLabel"
       :showCents="state.showKeyboardCents"