add basic spectrum function

packages/codemirror/widget.mjs

@@ -133,3 +133,10 @@ registerWidget('_pitchwheel', (id, options = {}, pat) => {
   const ctx = getCanvasWidget(id, options).getContext('2d');
   return pat.pitchwheel({ ...options, ctx, id });
 });
+
+registerWidget('_spectrum', (id, options = {}, pat) => {
+  let _size = options.size || 200;
+  options = { width: _size, height: _size, ...options, size: _size / 5 };
+  const ctx = getCanvasWidget(id, options).getContext('2d');
+  return pat.spectrum({ ...options, ctx, id });
+});

packages/draw/draw.mjs

@@ -26,7 +26,7 @@ export const getDrawContext = (id = 'test-canvas', options) => {
       }, 200);
     });
   }
-  return canvas.getContext(contextType);
+  return canvas.getContext(contextType, { willReadFrequently: true });
 };
 
 let animationFrames = {};

packages/superdough/superdough.mjs

@@ -270,11 +270,12 @@ function getReverb(orbit, duration, fade, lp, dim, ir) {
 export let analysers = {},
   analysersData = {};
 
-export function getAnalyserById(id, fftSize = 1024) {
+export function getAnalyserById(id, fftSize = 1024, smoothingTimeConstant = 0.5) {
   if (!analysers[id]) {
     // make sure this doesn't happen too often as it piles up garbage
     const analyserNode = getAudioContext().createAnalyser();
     analyserNode.fftSize = fftSize;
+    analyserNode.smoothingTimeConstant = smoothingTimeConstant;
     // getDestination().connect(analyserNode);
     analysers[id] = analyserNode;
     analysersData[id] = new Float32Array(analysers[id].frequencyBinCount);

packages/webaudio/index.mjs

@@ -6,4 +6,5 @@ This program is free software: you can redistribute it and/or modify it under th
 
 export * from './webaudio.mjs';
 export * from './scope.mjs';
+export * from './spectrum.mjs';
 export * from 'superdough';

packages/webaudio/spectrum.mjs

@@ -0,0 +1,69 @@
+import { Pattern, clamp } from '@strudel/core';
+import { getDrawContext, getTheme } from '@strudel/draw';
+import { analysers, getAnalyzerData } from 'superdough';
+
+/**
+ * Renders a spectrum analyzer for the incoming audio signal.
+ * @name spectrum
+ * @param {object} config optional config with options:
+ * @param {integer} thickness line thickness in px (default 3)
+ * @param {integer} speed scroll speed (default 1)
+ * @param {integer} min min db (default -80)
+ * @param {integer} max max db (default 0)
+ * @example
+ * n("<0 4 <2 3> 1>*3")
+ * .off(1/8, add(n(5)))
+ * .off(1/5, add(n(7)))
+ * .scale("d3:minor:pentatonic")
+ * .s('sine')
+ * .dec(.3).room(.5)
+ * ._spectrum()
+ */
+let latestColor = {};
+Pattern.prototype.spectrum = function (config = {}) {
+  let id = config.id ?? 1;
+  return this.analyze(id).draw(
+    (haps) => {
+      config.color = haps[0]?.value?.color || latestColor[id] || getTheme().foreground;
+      latestColor[id] = config.color;
+      drawSpectrum(analysers[id], config);
+    },
+    { id },
+  );
+};
+
+Pattern.prototype.scope = Pattern.prototype.tscope;
+
+const lastFrames = new Map();
+
+function drawSpectrum(
+  analyser,
+  { thickness = 3, speed = 1, min = -80, max = 0, ctx = getDrawContext(), id = 1, color } = {},
+) {
+  ctx.lineWidth = thickness;
+  ctx.strokeStyle = color;
+
+  if (!analyser) {
+    // if analyser is undefined, draw straight line
+    // it may be undefined when no sound has been played yet
+    return;
+  }
+  const scrollSize = speed;
+  const dataArray = getAnalyzerData('frequency', id);
+  const canvas = ctx.canvas;
+  ctx.fillStyle = color;
+  const bufferSize = analyser.frequencyBinCount;
+  let imageData = lastFrames.get(id) || ctx.getImageData(0, 0, canvas.width, canvas.height);
+  lastFrames.set(id, imageData);
+  ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
+  ctx.putImageData(imageData, -scrollSize, 0);
+  let q = canvas.width - speed;
+  for (let i = 0; i < bufferSize; i++) {
+    const normalized = clamp((dataArray[i] - min) / (max - min), 0, 1);
+    ctx.globalAlpha = normalized;
+    const next = (Math.log(i + 1) / Math.log(bufferSize)) * canvas.height;
+    const size = 2; //next - pos;
+    ctx.fillRect(q, canvas.height - next, scrollSize, size);
+  }
+  lastFrames.set(id, ctx.getImageData(0, 0, canvas.width, canvas.height));
+}

test/__snapshots__/examples.test.mjs.snap

@@ -7508,6 +7508,75 @@ exports[`runs examples > example "sometimesBy" example index 0 1`] = `
 ]
 `;
 
+exports[`runs examples > example "spectrum" example index 0 1`] = `
+[
+  "[ -5/24 ⇜ (0/1 → 1/8) | note:F4 s:sine decay:0.3 room:0.5 ]",
+  "[ -2/15 ⇜ (0/1 → 1/5) | note:A4 s:sine decay:0.3 room:0.5 ]",
+  "[ -1/120 ⇜ (0/1 → 1/5) ⇝ 13/40 | note:A5 s:sine decay:0.3 room:0.5 ]",
+  "[ 0/1 → 1/3 | note:D3 s:sine decay:0.3 room:0.5 ]",
+  "[ 1/8 → 11/24 | note:D4 s:sine decay:0.3 room:0.5 ]",
+  "[ -1/120 ⇜ (1/5 → 13/40) | note:A5 s:sine decay:0.3 room:0.5 ]",
+  "[ 1/5 → 8/15 | note:G4 s:sine decay:0.3 room:0.5 ]",
+  "[ 13/40 → 79/120 | note:G5 s:sine decay:0.3 room:0.5 ]",
+  "[ 1/3 → 2/3 | note:C4 s:sine decay:0.3 room:0.5 ]",
+  "[ 11/24 → 19/24 | note:C5 s:sine decay:0.3 room:0.5 ]",
+  "[ 8/15 → 13/15 | note:F5 s:sine decay:0.3 room:0.5 ]",
+  "[ 79/120 → 119/120 | note:F6 s:sine decay:0.3 room:0.5 ]",
+  "[ 2/3 → 1/1 | note:G3 s:sine decay:0.3 room:0.5 ]",
+  "[ (19/24 → 1/1) ⇝ 9/8 | note:G4 s:sine decay:0.3 room:0.5 ]",
+  "[ (13/15 → 1/1) ⇝ 6/5 | note:C5 s:sine decay:0.3 room:0.5 ]",
+  "[ (119/120 → 1/1) ⇝ 53/40 | note:C6 s:sine decay:0.3 room:0.5 ]",
+  "[ 19/24 ⇜ (1/1 → 9/8) | note:G4 s:sine decay:0.3 room:0.5 ]",
+  "[ 13/15 ⇜ (1/1 → 6/5) | note:C5 s:sine decay:0.3 room:0.5 ]",
+  "[ 119/120 ⇜ (1/1 → 6/5) ⇝ 53/40 | note:C6 s:sine decay:0.3 room:0.5 ]",
+  "[ 1/1 → 4/3 | note:F3 s:sine decay:0.3 room:0.5 ]",
+  "[ 9/8 → 35/24 | note:F4 s:sine decay:0.3 room:0.5 ]",
+  "[ 119/120 ⇜ (6/5 → 53/40) | note:C6 s:sine decay:0.3 room:0.5 ]",
+  "[ 6/5 → 23/15 | note:A4 s:sine decay:0.3 room:0.5 ]",
+  "[ 53/40 → 199/120 | note:A5 s:sine decay:0.3 room:0.5 ]",
+  "[ 4/3 → 5/3 | note:D3 s:sine decay:0.3 room:0.5 ]",
+  "[ 35/24 → 43/24 | note:D4 s:sine decay:0.3 room:0.5 ]",
+  "[ 23/15 → 28/15 | note:G4 s:sine decay:0.3 room:0.5 ]",
+  "[ 199/120 → 239/120 | note:G5 s:sine decay:0.3 room:0.5 ]",
+  "[ 5/3 → 2/1 | note:C4 s:sine decay:0.3 room:0.5 ]",
+  "[ (43/24 → 2/1) ⇝ 17/8 | note:C5 s:sine decay:0.3 room:0.5 ]",
+  "[ (28/15 → 2/1) ⇝ 11/5 | note:F5 s:sine decay:0.3 room:0.5 ]",
+  "[ (239/120 → 2/1) ⇝ 93/40 | note:F6 s:sine decay:0.3 room:0.5 ]",
+  "[ 43/24 ⇜ (2/1 → 17/8) | note:C5 s:sine decay:0.3 room:0.5 ]",
+  "[ 28/15 ⇜ (2/1 → 11/5) | note:F5 s:sine decay:0.3 room:0.5 ]",
+  "[ 239/120 ⇜ (2/1 → 11/5) ⇝ 93/40 | note:F6 s:sine decay:0.3 room:0.5 ]",
+  "[ 2/1 → 7/3 | note:A3 s:sine decay:0.3 room:0.5 ]",
+  "[ 17/8 → 59/24 | note:A4 s:sine decay:0.3 room:0.5 ]",
+  "[ 239/120 ⇜ (11/5 → 93/40) | note:F6 s:sine decay:0.3 room:0.5 ]",
+  "[ 11/5 → 38/15 | note:D5 s:sine decay:0.3 room:0.5 ]",
+  "[ 93/40 → 319/120 | note:D6 s:sine decay:0.3 room:0.5 ]",
+  "[ 7/3 → 8/3 | note:F3 s:sine decay:0.3 room:0.5 ]",
+  "[ 59/24 → 67/24 | note:F4 s:sine decay:0.3 room:0.5 ]",
+  "[ 38/15 → 43/15 | note:A4 s:sine decay:0.3 room:0.5 ]",
+  "[ 319/120 → 359/120 | note:A5 s:sine decay:0.3 room:0.5 ]",
+  "[ 8/3 → 3/1 | note:D3 s:sine decay:0.3 room:0.5 ]",
+  "[ (67/24 → 3/1) ⇝ 25/8 | note:D4 s:sine decay:0.3 room:0.5 ]",
+  "[ (43/15 → 3/1) ⇝ 16/5 | note:G4 s:sine decay:0.3 room:0.5 ]",
+  "[ (359/120 → 3/1) ⇝ 133/40 | note:G5 s:sine decay:0.3 room:0.5 ]",
+  "[ 67/24 ⇜ (3/1 → 25/8) | note:D4 s:sine decay:0.3 room:0.5 ]",
+  "[ 43/15 ⇜ (3/1 → 16/5) | note:G4 s:sine decay:0.3 room:0.5 ]",
+  "[ 359/120 ⇜ (3/1 → 16/5) ⇝ 133/40 | note:G5 s:sine decay:0.3 room:0.5 ]",
+  "[ 3/1 → 10/3 | note:C4 s:sine decay:0.3 room:0.5 ]",
+  "[ 25/8 → 83/24 | note:C5 s:sine decay:0.3 room:0.5 ]",
+  "[ 359/120 ⇜ (16/5 → 133/40) | note:G5 s:sine decay:0.3 room:0.5 ]",
+  "[ 16/5 → 53/15 | note:F5 s:sine decay:0.3 room:0.5 ]",
+  "[ 133/40 → 439/120 | note:F6 s:sine decay:0.3 room:0.5 ]",
+  "[ 10/3 → 11/3 | note:G3 s:sine decay:0.3 room:0.5 ]",
+  "[ 83/24 → 91/24 | note:G4 s:sine decay:0.3 room:0.5 ]",
+  "[ 53/15 → 58/15 | note:C5 s:sine decay:0.3 room:0.5 ]",
+  "[ 439/120 → 479/120 | note:C6 s:sine decay:0.3 room:0.5 ]",
+  "[ 11/3 → 4/1 | note:F3 s:sine decay:0.3 room:0.5 ]",
+  "[ (91/24 → 4/1) ⇝ 33/8 | note:F4 s:sine decay:0.3 room:0.5 ]",
+  "[ (58/15 → 4/1) ⇝ 21/5 | note:A4 s:sine decay:0.3 room:0.5 ]",
+  "[ (479/120 → 4/1) ⇝ 173/40 | note:A5 s:sine decay:0.3 room:0.5 ]",
+]
+`;
+
 exports[`runs examples > example "speed" example index 0 1`] = `
 [
   "[ 0/1 → 1/6 | s:bd speed:1 ]",

test/runtime.mjs

@@ -134,6 +134,9 @@ strudel.Pattern.prototype._pitchwheel = function () {
 strudel.Pattern.prototype._pianoroll = function () {
   return this;
 };
+strudel.Pattern.prototype._spectrum = function () {
+  return this;
+};
 strudel.Pattern.prototype.markcss = function () {
   return this;
 };

website/src/pages/learn/visual-feedback.mdx

@@ -99,6 +99,10 @@ What follows is the API doc of all the options you can pass:
 
 <JsDoc client:idle name="pitchwheel" h={0} />
 
+## Spectrum
+
+<JsDoc client:idle name="spectrum" h={0} />
+
 ## markcss
 
 <JsDoc client:idle name="markcss" h={0} />