implement pinch to zoom

node_modules/component-raf/example.html

@@ -0,0 +1,43 @@
+
+<style>
+  body {
+    padding: 50px;
+  }
+  canvas {
+    border: 1px solid #eee;
+  }
+</style>
+
+<script src="build/build.js"></script>
+
+<canvas width=900 height=300></canvas>
+
+<script>
+  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();
+</script>