move Framer + Drawer to core

... from vite-vanilla-repl-cm6

packages/core/draw.mjs

@@ -29,3 +29,98 @@ Pattern.prototype.onPaint = function (onPaint) {
   this.context = { onPaint };
   return this;
 };
+
+// const round = (x) => Math.round(x * 1000) / 1000;
+
+// encapsulates starting and stopping animation frames
+export class Framer {
+  constructor(onFrame, onError) {
+    this.onFrame = onFrame;
+    this.onError = onError;
+  }
+  start() {
+    const self = this;
+    let frame = requestAnimationFrame(function updateHighlights(time) {
+      try {
+        self.onFrame(time);
+      } catch (err) {
+        self.onError(err);
+      }
+      frame = requestAnimationFrame(updateHighlights);
+    });
+    self.cancel = () => {
+      cancelAnimationFrame(frame);
+    };
+  }
+  stop() {
+    if (this.cancel) {
+      this.cancel();
+    }
+  }
+}
+
+// syncs animation frames to a cyclist scheduler
+// see vite-vanilla-repl-cm6 for an example
+export class Drawer {
+  constructor(onDraw, drawTime) {
+    let [lookbehind, lookahead] = drawTime; // e.g. [-2, 2]
+    lookbehind = Math.abs(lookbehind);
+    this.visibleHaps = [];
+    this.lastFrame = null;
+    this.drawTime = drawTime;
+    this.framer = new Framer(
+      () => {
+        if (!this.scheduler) {
+          console.warn('Drawer: no scheduler');
+          return;
+        }
+        // calculate current frame time (think right side of screen for pianoroll)
+        const phase = this.scheduler.now() + lookahead;
+        // first frame just captures the phase
+        if (this.lastFrame === null) {
+          this.lastFrame = phase;
+          return;
+        }
+        // query haps from last frame till now. take last 100ms max
+        const haps = this.scheduler.pattern.queryArc(Math.max(this.lastFrame, phase - 1 / 10), phase);
+        this.lastFrame = phase;
+        this.visibleHaps = (this.visibleHaps || [])
+          // filter out haps that are too far in the past (think left edge of screen for pianoroll)
+          .filter((h) => h.whole.end >= phase - lookbehind - lookahead)
+          // add new haps with onset (think right edge bars scrolling in)
+          .concat(haps.filter((h) => h.hasOnset()));
+        const time = phase - lookahead;
+        onDraw(this.visibleHaps, time, this);
+      },
+      (err) => {
+        console.warn('draw error', err);
+      },
+    );
+  }
+  check() {
+    if (!this.scheduler) {
+      throw new Error('no scheduler set..');
+    }
+  }
+  invalidate() {
+    this.check();
+    const t = this.scheduler.now();
+    let [_, lookahead] = this.drawTime;
+    // remove all future haps
+    this.visibleHaps = this.visibleHaps.filter((h) => h.whole.begin < t);
+    // query future haps
+    const futureHaps = this.scheduler.pattern.queryArc(Math.max(t, 0), t + lookahead + 0.1); // +0.1 = workaround for weird holes in query..
+    // append future haps
+    this.visibleHaps = this.visibleHaps.concat(futureHaps);
+  }
+  start(scheduler) {
+    this.scheduler = scheduler;
+    this.invalidate();
+    this.framer.start();
+  }
+  stop() {
+    if (this.framer) {
+      this.framer.stop();
+    }
+  }
+}