implement pinch to zoom

node_modules/component-raf/Readme.md

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+
+# raf
+
+  request animation frame
+
+## Installation
+
+    $ component install component/raf
+
+## Example
+
+  Request the animation frame with `raf(fn)`, cancel with `raf.cancel(id)`.
+
+```js
+var x = 0;
+var y = 50;
+var canvas = document.querySelector('canvas');
+var ctx = canvas.getContext('2d');
+var raf = require('raf');
+
+function animate() {
+  raf(animate);
+  draw();
+}
+
+var prev = Date.now();
+function draw() {
+  var curr = Date.now();
+  var diff = curr - prev;
+  var p = diff / 16;
+  ctx.clearRect(0, 0, 900, 300);
+  ctx.beginPath();
+  ctx.globalAlpha = .5;
+  ctx.arc(x, y, 10, 0, Math.PI * 2, false);
+  ctx.fill();
+  x += 2;
+  y += Math.sin(x/20) * 5;
+  prev = curr;
+}
+
+animate();
+```
+
+## License
+
+  MIT