Add initial shader module

This change adds the `loadShader` and `shader` function, to be used like this:

```strudel
await loadShader`
  // The modulation targets
  uniform float iColor;

  void mainImage( out vec4 fragColor, in vec2 fragCoord ) {
    vec2 uv = fragCoord / iResolution.xy;
    vec3 col = 0.5 + 0.5*cos(iColor+uv.xyx+vec3(0,2,4));
    fragColor = vec4(col, 0);
  }
`

$: s("bd").shader({uniform: 'iColor'})
```

packages/draw/index.mjs

@@ -2,5 +2,6 @@ export * from './animate.mjs';
 export * from './color.mjs';
 export * from './draw.mjs';
 export * from './pianoroll.mjs';
+export * from './shader.mjs';
 export * from './spiral.mjs';
 export * from './pitchwheel.mjs';

packages/draw/package.json

@@ -29,7 +29,8 @@
   },
   "homepage": "https://github.com/tidalcycles/strudel#readme",
   "dependencies": {
-    "@strudel/core": "workspace:*"
+    "@strudel/core": "workspace:*",
+    "picogl": "^0.17.9"
   },
   "devDependencies": {
     "vite": "^5.0.10"

packages/draw/shader.mjs

@@ -0,0 +1,230 @@
+/*
+shader.mjs - implements the `loadShader` helper and `shader` pattern function
+Copyright (C) 2024 Strudel contributors
+This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details. You should have received a copy of the GNU Affero General Public License along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+import { PicoGL } from "picogl";
+import { register, logger } from '@strudel/core';
+
+// The standard fullscreen vertex shader.
+const vertexShader = `#version 300 es
+precision highp float;
+layout(location=0) in vec2 position;
+void main() {
+  gl_Position = vec4(position, 1, 1);
+}
+`;
+
+// Make the fragment source, similar to the one from shadertoy.
+function mkFragmentShader(code) {
+  return `#version 300 es
+precision highp float;
+out vec4 oColor;
+uniform float iTime;
+uniform vec2 iResolution;
+
+${code}
+
+void main(void) {
+  mainImage(oColor, gl_FragCoord.xy);
+}
+`
+}
+
+// Modulation helpers.
+const hardModulation = () => {
+  let val = 0;
+  return {
+    get: () => val,
+    set: (v) => { val = v },
+  }
+}
+
+const decayModulation = (decay) => {
+  let val = 0;
+  let desired = 0
+  return {
+    get: (ts) => {
+      val += (desired - val) / decay
+      return val
+    },
+    set: (v) => { desired = val + v },
+  }
+}
+
+// Set an uniform value (from a pattern).
+function setUniform(instance, name, value, position) {
+  const uniform = instance.uniforms[name]
+  if (uniform) {
+    if (uniform.count == 0) {
+      // This is a single value
+      uniform.mod.set(value)
+    } else {
+      // This is an array
+      const idx = position % uniform.mod.length
+      uniform.mod[idx].set(value)
+    }
+  } else {
+    logger('[shader] unknown uniform: ' + name)
+  }
+
+  // Ensure the instance is drawn
+  instance.age = 0
+  if (!instance.drawing) {
+    instance.drawing = requestAnimationFrame(instance.update)
+  }
+}
+
+// Update the uniforms for a given drawFrame call.
+function updateUniforms(drawFrame, elapsed, uniforms) {
+  Object.values(uniforms).forEach((uniform) => {
+    const value = uniform.count == 0
+          ? uniform.mod.get(elapsed)
+          : uniform.value.map((_, i) => uniform.mod[i].get(elapsed))
+    // Send the value to the GPU
+    drawFrame.uniform(uniform.name, value)
+  })
+}
+
+// Setup the instance's uniform after shader compilation.
+function setupUniforms(uniforms, program) {
+  Object.entries(program.uniforms).forEach(([name, uniform]) => {
+    if (name != "iTime" && name != "iResolution") {
+      // remove array suffix
+      const uname = name.replace("[0]", "")
+      const count = uniform.count | 0
+      if (!uniforms[uname] || uniforms[name].count != count) {
+        // TODO: keep the previous value when the count change...
+        uniforms[uname] = {
+          name,
+          count,
+          value: count == 0 ? 0 : new Float32Array(count),
+          mod: count == 0 ? decayModulation(50) : new Array(count).fill().map(() => decayModulation(50))
+        }
+      }
+    }
+  })
+  // TODO: remove previous uniform that are no longer used...
+  return uniforms
+}
+
+// Setup the canvas and return the WebGL context.
+function setupCanvas(name) {
+  // TODO: support custom size
+  const width = 400; const height = 300;
+  const canvas = document.createElement('canvas');
+  canvas.id = "cnv-" + name
+  canvas.width = width
+  canvas.height = height
+  const top = 60 + Object.keys(_instances).length * height
+  canvas.style = `pointer-events:none;width:${width}px;height:${height}px;position:fixed;top:${top}px;right:23px`;
+  document.body.append(canvas)
+  return canvas.getContext("webgl2")
+}
+
+// Setup the shader instance
+async function initializeShaderInstance(name, code) {
+  // Setup PicoGL app
+  const ctx = setupCanvas(name)
+  console.log(ctx)
+  const app = PicoGL.createApp(ctx);
+  app.resize(400, 300)
+
+  // Setup buffers
+  const resolution = new Float32Array([ctx.canvas.width, ctx.canvas.height])
+
+  // Two triangle to cover the whole canvas
+  const positionBuffer = app.createVertexBuffer(PicoGL.FLOAT, 2, new Float32Array([
+    -1, -1, -1,  1,  1,  1,
+     1,  1,  1, -1, -1, -1,
+  ]))
+
+  // Setup the arrays
+  const arrays = app.createVertexArray().vertexAttributeBuffer(0, positionBuffer);
+
+  return app.createPrograms([vertexShader, code]).then(([program]) => {
+    const drawFrame = app.createDrawCall(program, arrays)
+    const instance = {app, code, program, arrays, drawFrame, uniforms: setupUniforms({}, program)}
+
+    // Render frame logic
+    let prev = performance.now() / 1000;
+    instance.age = 0
+    instance.update = () => {
+      const now = performance.now() / 1000;
+      const elapsed = now - prev
+      prev = now
+      // console.log("drawing!")
+      app.clear()
+      instance.drawFrame
+        .uniform("iResolution", resolution)
+        .uniform("iTime", now)
+
+      updateUniforms(instance.drawFrame, elapsed, instance.uniforms)
+
+      instance.drawFrame.draw()
+      if (instance.age++ < 100)
+        requestAnimationFrame(instance.update)
+      else
+        instance.drawing = false
+    }
+    return instance
+  }).catch((err) => {
+    ctx.canvas.remove()
+    throw err
+  })
+}
+
+// Update the instance program
+async function reloadShaderInstanceCode(instance, code) {
+  return instance.app.createPrograms([vertexShader, code]).then(([program]) => {
+    instance.program.delete()
+    instance.program = program
+    instance.uniforms = setupUniforms(instance.uniforms, program)
+    instance.draw = instance.app.createDrawCall(program, instance.arrays)
+  })
+}
+
+// Keep track of the running shader instances
+let _instances = {}
+export async function loadShader(code = '', name = 'default') {
+  if (code) {
+    code = mkFragmentShader(code)
+  }
+  if (!_instances[name]) {
+    _instances[name] = await initializeShaderInstance(name, code)
+    logger('[shader] ready')
+  } else if (_instances[name].code != code) {
+    await reloadShaderInstanceCode(_instances[name], code)
+    logger('[shader] reloaded')
+  }
+}
+
+export const shader = register('shader', (options, pat) => {
+  // Keep track of the pitches value: Map String Int
+  const pitches = {_count: 0};
+
+  return pat.onTrigger((time_deprecate, hap, currentTime, cps, targetTime) => {
+    const instance = _instances[options.instance || "default"]
+    if (!instance) {
+      logger('[shader] not loaded yet', 'warning')
+      return
+    }
+
+    const value = options.gain || 1.0;
+    if (options.pitch !== undefined) {
+      const note = hap.value.note || hap.value.s;
+      if (pitches[note] === undefined) {
+        // Assign new value, the first note gets 0, then 1, then 2, ...
+        pitches[note] = Object.keys(pitches).length
+      }
+      setUniform(instance, options.pitch, value, pitches[note])
+    } else if (options.seq !== undefined) {
+      setUniform(instance, options.seq, value, pitches.count++)
+    } else if (options.uniform !== undefined) {
+      setUniform(instance, options.uniform, value)
+    } else {
+      console.error("Unknown shader options, need either pitch or uniform", options)
+    }
+  }, false)
+})