resources/js/cr.js

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/**
 * The global object.
 * @type {!Object}
 * @const
 */
var global = this;

/** Platform, package, object property, and Event support. **/
var cr = function() {
  'use strict';

  /**
   * Builds an object structure for the provided namespace path,
   * ensuring that names that already exist are not overwritten. For
   * example:
   * "a.b.c" -> a = {};a.b={};a.b.c={};
   * @param {string} name Name of the object that this file defines.
   * @param {*=} opt_object The object to expose at the end of the path.
   * @param {Object=} opt_objectToExportTo The object to add the path to;
   *     default is {@code global}.
   * @private
   */
  function exportPath(name, opt_object, opt_objectToExportTo) {
    var parts = name.split('.');
    var cur = opt_objectToExportTo || global;

    for (var part; parts.length && (part = parts.shift());) {
      if (!parts.length && opt_object !== undefined) {
        // last part and we have an object; use it
        cur[part] = opt_object;
      } else if (part in cur) {
        cur = cur[part];
      } else {
        cur = cur[part] = {};
      }
    }
    return cur;
  };

  /**
   * Fires a property change event on the target.
   * @param {EventTarget} target The target to dispatch the event on.
   * @param {string} propertyName The name of the property that changed.
   * @param {*} newValue The new value for the property.
   * @param {*} oldValue The old value for the property.
   */
  function dispatchPropertyChange(target, propertyName, newValue, oldValue) {
    var e = new Event(propertyName + 'Change');
    e.propertyName = propertyName;
    e.newValue = newValue;
    e.oldValue = oldValue;
    target.dispatchEvent(e);
  }

  /**
   * Converts a camelCase javascript property name to a hyphenated-lower-case
   * attribute name.
   * @param {string} jsName The javascript camelCase property name.
   * @return {string} The equivalent hyphenated-lower-case attribute name.
   */
  function getAttributeName(jsName) {
    return jsName.replace(/([A-Z])/g, '-$1').toLowerCase();
  }

  /**
   * The kind of property to define in {@code defineProperty}.
   * @enum {string}
   * @const
   */
  var PropertyKind = {
    /**
     * Plain old JS property where the backing data is stored as a "private"
     * field on the object.
     * Use for properties of any type. Type will not be checked.
     */
    JS: 'js',

    /**
     * The property backing data is stored as an attribute on an element.
     * Use only for properties of type {string}.
     */
    ATTR: 'attr',

    /**
     * The property backing data is stored as an attribute on an element. If the
     * element has the attribute then the value is true.
     * Use only for properties of type {boolean}.
     */
    BOOL_ATTR: 'boolAttr'
  };

  /**
   * Helper function for defineProperty that returns the getter to use for the
   * property.
   * @param {string} name The name of the property.
   * @param {PropertyKind} kind The kind of the property.
   * @return {function():*} The getter for the property.
   */
  function getGetter(name, kind) {
    switch (kind) {
      case PropertyKind.JS:
        var privateName = name + '_';
        return function() {
          return this[privateName];
        };
      case PropertyKind.ATTR:
        var attributeName = getAttributeName(name);
        return function() {
          return this.getAttribute(attributeName);
        };
      case PropertyKind.BOOL_ATTR:
        var attributeName = getAttributeName(name);
        return function() {
          return this.hasAttribute(attributeName);
        };
    }

    // TODO(dbeam): replace with assertNotReached() in assert.js when I can coax
    // the browser/unit tests to preprocess this file through grit.
    throw 'not reached';
  }

  /**
   * Helper function for defineProperty that returns the setter of the right
   * kind.
   * @param {string} name The name of the property we are defining the setter
   *     for.
   * @param {PropertyKind} kind The kind of property we are getting the
   *     setter for.
   * @param {function(*, *):void=} opt_setHook A function to run after the
   *     property is set, but before the propertyChange event is fired.
   * @return {function(*):void} The function to use as a setter.
   */
  function getSetter(name, kind, opt_setHook) {
    switch (kind) {
      case PropertyKind.JS:
        var privateName = name + '_';
        return function(value) {
          var oldValue = this[name];
          if (value !== oldValue) {
            this[privateName] = value;
            if (opt_setHook)
              opt_setHook.call(this, value, oldValue);
            dispatchPropertyChange(this, name, value, oldValue);
          }
        };

      case PropertyKind.ATTR:
        var attributeName = getAttributeName(name);
        return function(value) {
          var oldValue = this[name];
          if (value !== oldValue) {
            if (value == undefined)
              this.removeAttribute(attributeName);
            else
              this.setAttribute(attributeName, value);
            if (opt_setHook)
              opt_setHook.call(this, value, oldValue);
            dispatchPropertyChange(this, name, value, oldValue);
          }
        };

      case PropertyKind.BOOL_ATTR:
        var attributeName = getAttributeName(name);
        return function(value) {
          var oldValue = this[name];
          if (value !== oldValue) {
            if (value)
              this.setAttribute(attributeName, name);
            else
              this.removeAttribute(attributeName);
            if (opt_setHook)
              opt_setHook.call(this, value, oldValue);
            dispatchPropertyChange(this, name, value, oldValue);
          }
        };
    }

    // TODO(dbeam): replace with assertNotReached() in assert.js when I can coax
    // the browser/unit tests to preprocess this file through grit.
    throw 'not reached';
  }

  /**
   * Defines a property on an object. When the setter changes the value a
   * property change event with the type {@code name + 'Change'} is fired.
   * @param {!Object} obj The object to define the property for.
   * @param {string} name The name of the property.
   * @param {PropertyKind=} opt_kind What kind of underlying storage to use.
   * @param {function(*, *):void=} opt_setHook A function to run after the
   *     property is set, but before the propertyChange event is fired.
   */
  function defineProperty(obj, name, opt_kind, opt_setHook) {
    if (typeof obj == 'function')
      obj = obj.prototype;

    var kind = /** @type {PropertyKind} */ (opt_kind || PropertyKind.JS);

    if (!obj.__lookupGetter__(name))
      obj.__defineGetter__(name, getGetter(name, kind));

    if (!obj.__lookupSetter__(name))
      obj.__defineSetter__(name, getSetter(name, kind, opt_setHook));
  }

  /**
   * Counter for use with createUid
   */
  var uidCounter = 1;

  /**
   * @return {number} A new unique ID.
   */
  function createUid() {
    return uidCounter++;
  }

  /**
   * Returns a unique ID for the item. This mutates the item so it needs to be
   * an object
   * @param {!Object} item The item to get the unique ID for.
   * @return {number} The unique ID for the item.
   */
  function getUid(item) {
    if (item.hasOwnProperty('uid'))
      return item.uid;
    return item.uid = createUid();
  }

  /**
   * Dispatches a simple event on an event target.
   * @param {!EventTarget} target The event target to dispatch the event on.
   * @param {string} type The type of the event.
   * @param {boolean=} opt_bubbles Whether the event bubbles or not.
   * @param {boolean=} opt_cancelable Whether the default action of the event
   *     can be prevented. Default is true.
   * @return {boolean} If any of the listeners called {@code preventDefault}
   *     during the dispatch this will return false.
   */
  function dispatchSimpleEvent(target, type, opt_bubbles, opt_cancelable) {
    var e = new Event(type, {
      bubbles: opt_bubbles,
      cancelable: opt_cancelable === undefined || opt_cancelable
    });
    return target.dispatchEvent(e);
  }

  /**
   * Calls |fun| and adds all the fields of the returned object to the object
   * named by |name|. For example, cr.define('cr.ui', function() {
   *   function List() {
   *     ...
   *   }
   *   function ListItem() {
   *     ...
   *   }
   *   return {
   *     List: List,
   *     ListItem: ListItem,
   *   };
   * });
   * defines the functions cr.ui.List and cr.ui.ListItem.
   * @param {string} name The name of the object that we are adding fields to.
   * @param {!Function} fun The function that will return an object containing
   *     the names and values of the new fields.
   */
  function define(name, fun) {
    var obj = exportPath(name);
    var exports = fun();
    for (var propertyName in exports) {
      // Maybe we should check the prototype chain here? The current usage
      // pattern is always using an object literal so we only care about own
      // properties.
      var propertyDescriptor = Object.getOwnPropertyDescriptor(exports,
                                                               propertyName);
      if (propertyDescriptor)
        Object.defineProperty(obj, propertyName, propertyDescriptor);
    }
  }

  /**
   * Adds a {@code getInstance} static method that always return the same
   * instance object.
   * @param {!Function} ctor The constructor for the class to add the static
   *     method to.
   */
  function addSingletonGetter(ctor) {
    ctor.getInstance = function() {
      return ctor.instance_ || (ctor.instance_ = new ctor());
    };
  }

  /**
   * Forwards public APIs to private implementations.
   * @param {Function} ctor Constructor that have private implementations in its
   *     prototype.
   * @param {Array.<string>} methods List of public method names that have their
   *     underscored counterparts in constructor's prototype.
   * @param {string=} opt_target Selector for target node.
   */
  function makePublic(ctor, methods, opt_target) {
    methods.forEach(function(method) {
      ctor[method] = function() {
        var target = opt_target ? document.getElementById(opt_target) :
                     ctor.getInstance();
        return target[method + '_'].apply(target, arguments);
      };
    });
  }

  return {
    addSingletonGetter: addSingletonGetter,
    createUid: createUid,
    define: define,
    defineProperty: defineProperty,
    dispatchPropertyChange: dispatchPropertyChange,
    dispatchSimpleEvent: dispatchSimpleEvent,
    exportPath: exportPath,
    getUid: getUid,
    makePublic: makePublic,
    PropertyKind: PropertyKind,

    get doc() {
      return document;
    },

    /** Whether we are using a Mac or not. */
    get isMac() {
      return /Mac/.test(navigator.platform);
    },

    /** Whether this is on the Windows platform or not. */
    get isWindows() {
      return /Win/.test(navigator.platform);
    },

    /** Whether this is on chromeOS or not. */
    get isChromeOS() {
      return /CrOS/.test(navigator.userAgent);
    },

    /** Whether this is on vanilla Linux (not chromeOS). */
    get isLinux() {
      return /Linux/.test(navigator.userAgent);
    },

    /** Whether this uses the views toolkit or not. */
    get isViews() {
      return typeof chrome.getVariableValue == 'function' &&
          /views/.test(chrome.getVariableValue('toolkit'));
    },
  };
}();