add draw helpers + pianoroll

repl/src/draw.mjs

@@ -0,0 +1,43 @@
+import * as Tone from 'tone';
+
+export const getDrawContext = (id = 'test-canvas') => {
+  let canvas = document.querySelector('#' + id);
+  if (!canvas) {
+    canvas = document.createElement('canvas');
+    canvas.id = id;
+    canvas.width = window.innerWidth;
+    canvas.height = window.innerHeight;
+    canvas.style = 'pointer-events:none;width:100%;height:100%;position:fixed;top:0;left:0';
+    document.body.prepend(canvas);
+  }
+  return canvas.getContext('2d');
+};
+
+export const draw = (callback) => {
+  if (window.strudelAnimation) {
+    cancelAnimationFrame(window.strudelAnimation);
+  }
+  const animate = (t) => {
+    callback(t);
+    window.strudelAnimation = requestAnimationFrame(animate);
+  };
+  requestAnimationFrame(animate);
+};
+
+export const queryEvents = (pattern, callback, seconds) => {
+  const queryEvents = () => {
+    const t = Tone.getTransport().seconds;
+    const begin = Math.floor(t / seconds) * seconds;
+    const end = begin + seconds * 4;
+    // console.log('query', t, begin, end);
+    const events = pattern.add(0).query(new State(new TimeSpan(begin, end)));
+    callback(events);
+  };
+  queryEvents();
+  if (window.strudelScheduler) {
+    clearInterval(window.strudelScheduler);
+  }
+  window.strudelScheduler = setInterval(() => {
+    queryEvents();
+  }, seconds * 1.5 * 1000);
+};