twojs-browserify/events.js

A browserified two-dimensional drawing api meant for modern browsers.

/**
 * The Events module pulled from [Backbone.js](http://backbonejs.org/)
 * Stripped and modified to work with node.js and optimize types of calls
 * for animation based events.
 */

var Backbone = Backbone || {};

(function() {

  var array = [];
  var slice = array.slice;

  // Backbone.Events
  // ---------------

  // Regular expression used to split event strings.
  var eventSplitter = /\s+/;

  /**
   * Events API deprecated because of additional calls and checks
   * multiple times a frame tick in two.js
   */

  // Optimized internal dispatch function for triggering events. Tries to
  // keep the usual cases speedy (most Backbone events have 3 arguments).
  var triggerEvents = function(obj, events, args) {
    var ev, i = -1, l = events.length;
    switch (args.length) {
    case 0: while (++i < l) (ev = events[i]).callback.call(ev.ctx);
    return;
    case 1: while (++i < l) (ev = events[i]).callback.call(ev.ctx, args[0]);
    return;
    case 2: while (++i < l) (ev = events[i]).callback.call(ev.ctx, args[0], args[1]);
    return;
    case 3: while (++i < l) (ev = events[i]).callback.call(ev.ctx, args[0], args[1], args[2]);
    return;
    default: while (++i < l) (ev = events[i]).callback.apply(ev.ctx, args);
    }
  };

  var Events = Backbone.Events = {

    // Bind one or more space separated events, or an events map,
    // to a `callback` function. Passing `"all"` will bind the callback to
    // all events fired.
    on: function(name, callback, context) {
      // if (!(eventsApi(this, 'on', name, [callback, context]) && callback)) return this;
      this._events || (this._events = {});
      var list = this._events[name] || (this._events[name] = []);
      list.push({callback: callback, context: context, ctx: context || this});
      return this;
    },

    // Bind events to only be triggered a single time. After the first time
    // the callback is invoked, it will be removed.
    once: function(name, callback, context) {
      // if (!(eventsApi(this, 'once', name, [callback, context]) && callback)) return this;
      var self = this;
      var once = _.once(function() {
        self.off(name, once);
        callback.apply(this, arguments);
      });
      once._callback = callback;
      this.on(name, once, context);
      return this;
    },

    // Remove one or many callbacks. If `context` is null, removes all
    // callbacks with that function. If `callback` is null, removes all
    // callbacks for the event. If `events` is null, removes all bound
    // callbacks for all events.
    off: function(name, callback, context) {
      var list, ev, events, names, i, l, j, k;
      if (!this._events/** || !eventsApi(this, 'off', name, [callback, context])**/) return this;
      if (!name && !callback && !context) {
        this._events = {};
        return this;
      }

      names = name ? [name] : _.keys(this._events);
      for (i = 0, l = names.length; i < l; i++) {
        name = names[i];
        if (list = this._events[name]) {
          events = [];
          if (callback || context) {
            for (j = 0, k = list.length; j < k; j++) {
              ev = list[j];
              if ((callback && callback !== (ev.callback._callback || ev.callback)) ||
                  (context && context !== ev.context)) {
                events.push(ev);
              }
            }
          }
          this._events[name] = events;
        }
      }

      return this;
    },

    // Trigger one or many events, firing all bound callbacks. Callbacks are
    // passed the same arguments as `trigger` is, apart from the event name
    // (unless you're listening on `"all"`, which will cause your callback to
    // receive the true name of the event as the first argument).
    trigger: function(name) {
      if (!this._events) return this;
      var args = slice.call(arguments, 1);
      // if (!eventsApi(this, 'trigger', name, args)) return this;
      var events = this._events[name];
      var allEvents = this._events.all;
      if (events) triggerEvents(this, events, args);
      if (allEvents) triggerEvents(this, allEvents, arguments);
      return this;
    },

    // An inversion-of-control version of `on`. Tell *this* object to listen to
    // an event in another object ... keeping track of what it's listening to.
    listenTo: function(object, events, callback) {
      var listeners = this._listeners || (this._listeners = {});
      var id = object._listenerId || (object._listenerId = _.uniqueId('l'));
      listeners[id] = object;
      object.on(events, callback || this, this);
      return this;
    },

    // Tell this object to stop listening to either specific events ... or
    // to every object it's currently listening to.
    stopListening: function(object, events, callback) {
      var listeners = this._listeners;
      if (!listeners) return;
      if (object) {
        object.off(events, callback, this);
        if (!events && !callback) delete listeners[object._listenerId];
      } else {
        for (var id in listeners) {
          listeners[id].off(null, null, this);
        }
        this._listeners = {};
      }
      return this;
    }
  };

  // Aliases for backwards compatibility.
  Events.bind   = Events.on;
  Events.unbind = Events.off;

  if (typeof exports !== 'undefined') {
    if (typeof module !== 'undefined' && module.exports) {
      exports = module.exports = Events;
    }
    exports.Backbone = exports.Backbone || Backbone;
  }

})();