implement pinch to zoom

node_modules/component-tween/index.js

@@ -0,0 +1,178 @@
+
+/**
+ * Module dependencies.
+ */
+
+var Emitter = require('emitter');
+var clone = require('clone');
+var type = require('type');
+var ease = require('ease');
+
+/**
+ * Expose `Tween`.
+ */
+
+module.exports = Tween;
+
+/**
+ * Initialize a new `Tween` with `obj`.
+ *
+ * @param {Object|Array} obj
+ * @api public
+ */
+
+function Tween(obj) {
+  if (!(this instanceof Tween)) return new Tween(obj);
+  this._from = obj;
+  this.ease('linear');
+  this.duration(500);
+}
+
+/**
+ * Mixin emitter.
+ */
+
+Emitter(Tween.prototype);
+
+/**
+ * Reset the tween.
+ *
+ * @api public
+ */
+
+Tween.prototype.reset = function(){
+  this.isArray = 'array' === type(this._from);
+  this._curr = clone(this._from);
+  this._done = false;
+  this._start = Date.now();
+  return this;
+};
+
+/**
+ * Tween to `obj` and reset internal state.
+ *
+ *    tween.to({ x: 50, y: 100 })
+ *
+ * @param {Object|Array} obj
+ * @return {Tween} self
+ * @api public
+ */
+
+Tween.prototype.to = function(obj){
+  this.reset();
+  this._to = obj;
+  return this;
+};
+
+/**
+ * Set duration to `ms` [500].
+ *
+ * @param {Number} ms
+ * @return {Tween} self
+ * @api public
+ */
+
+Tween.prototype.duration = function(ms){
+  this._duration = ms;
+  return this;
+};
+
+/**
+ * Set easing function to `fn`.
+ *
+ *    tween.ease('in-out-sine')
+ *
+ * @param {String|Function} fn
+ * @return {Tween}
+ * @api public
+ */
+
+Tween.prototype.ease = function(fn){
+  fn = 'function' == typeof fn ? fn : ease[fn];
+  if (!fn) throw new TypeError('invalid easing function');
+  this._ease = fn;
+  return this;
+};
+
+/**
+ * Stop the tween and immediately emit "stop" and "end".
+ *
+ * @return {Tween}
+ * @api public
+ */
+
+Tween.prototype.stop = function(){
+  this.stopped = true;
+  this._done = true;
+  this.emit('stop');
+  this.emit('end');
+  return this;
+};
+
+/**
+ * Perform a step.
+ *
+ * @return {Tween} self
+ * @api private
+ */
+
+Tween.prototype.step = function(){
+  if (this._done) return;
+
+  // duration
+  var duration = this._duration;
+  var now = Date.now();
+  var delta = now - this._start;
+  var done = delta >= duration;
+
+  // complete
+  if (done) {
+    this._from = this._to;
+    this._update(this._to);
+    this._done = true;
+    this.emit('end');
+    return this;
+  }
+
+  // tween
+  var from = this._from;
+  var to = this._to;
+  var curr = this._curr;
+  var fn = this._ease;
+  var p = (now - this._start) / duration;
+  var n = fn(p);
+
+  // array
+  if (this.isArray) {
+    for (var i = 0; i < from.length; ++i) {
+      curr[i] = from[i] + (to[i] - from[i]) * n;
+    }
+
+    this._update(curr);
+    return this;
+  }
+
+  // objech
+  for (var k in from) {
+    curr[k] = from[k] + (to[k] - from[k]) * n;
+  }
+
+  this._update(curr);
+  return this;
+};
+
+/**
+ * Set update function to `fn` or
+ * when no argument is given this performs
+ * a "step".
+ *
+ * @param {Function} fn
+ * @return {Tween} self
+ * @api public
+ */
+
+Tween.prototype.update = function(fn){
+  if (0 == arguments.length) return this.step();
+  this._update = fn;
+  return this;
+};