add mutation observer polyfill package

pkg/mutation_observer/lib/mutation_observer.js

+/*
+ * Copyright 2013 The Polymer Authors. All rights reserved.
+ * Use of this source code is goverened by a BSD-style
+ * license that can be found in the LICENSE file.
+ */
+
+// TODO(jmesserly): polyfill does not have feature testing or the definition of
+// SideTable. The extra code is from:
+// https://github.com/Polymer/CustomElements/blob/master/src/MutationObserver.js
+// https://github.com/Polymer/CustomElements/blob/master/src/sidetable.js
+// I also renamed JsMutationObserver -> MutationObserver to correctly interact
+// with dart2js interceptors.
+if (!window.MutationObserver && !window.WebKitMutationObserver) {
+
+(function(global) {
+  // SideTable is a weak map where possible. If WeakMap is not available the
+  // association is stored as an expando property.
+  var SideTable;
+  // TODO(arv): WeakMap does not allow for Node etc to be keys in Firefox
+  if (typeof WeakMap !== 'undefined' && navigator.userAgent.indexOf('Firefox/') < 0) {
+    SideTable = WeakMap;
+  } else {
+    (function() {
+      var defineProperty = Object.defineProperty;
+      var hasOwnProperty = Object.hasOwnProperty;
+      var counter = new Date().getTime() % 1e9;
+
+      SideTable = function() {
+        this.name = '__st' + (Math.random() * 1e9 >>> 0) + (counter++ + '__');
+      };
+
+      SideTable.prototype = {
+        set: function(key, value) {
+          defineProperty(key, this.name, {value: value, writable: true});
+        },
+        get: function(key) {
+          return hasOwnProperty.call(key, this.name) ? key[this.name] : undefined;
+        },
+        delete: function(key) {
+          this.set(key, undefined);
+        }
+      }
+    })();
+  }
+
+  var registrationsTable = new SideTable();
+
+  // We use setImmediate or postMessage for our future callback.
+  var setImmediate = window.msSetImmediate;
+
+  // Use post message to emulate setImmediate.
+  if (!setImmediate) {
+    var setImmediateQueue = [];
+    var sentinel = String(Math.random());
+    window.addEventListener('message', function(e) {
+      if (e.data === sentinel) {
+        var queue = setImmediateQueue;
+        setImmediateQueue = [];
+        queue.forEach(function(func) {
+          func();
+        });
+      }
+    });
+    setImmediate = function(func) {
+      setImmediateQueue.push(func);
+      window.postMessage(sentinel, '*');
+    };
+  }
+
+  // This is used to ensure that we never schedule 2 callas to setImmediate
+  var isScheduled = false;
+
+  // Keep track of observers that needs to be notified next time.
+  var scheduledObservers = [];
+
+  /**
+   * Schedules |dispatchCallback| to be called in the future.
+   * @param {MutationObserver} observer
+   */
+  function scheduleCallback(observer) {
+    scheduledObservers.push(observer);
+    if (!isScheduled) {
+      isScheduled = true;
+      setImmediate(dispatchCallbacks);
+    }
+  }
+
+  function wrapIfNeeded(node) {
+    return window.ShadowDOMPolyfill &&
+        window.ShadowDOMPolyfill.wrapIfNeeded(node) ||
+        node;
+  }
+
+  function dispatchCallbacks() {
+    // http://dom.spec.whatwg.org/#mutation-observers
+
+    isScheduled = false; // Used to allow a new setImmediate call above.
+
+    var observers = scheduledObservers;
+    scheduledObservers = [];
+    // Sort observers based on their creation UID (incremental).
+    observers.sort(function(o1, o2) {
+      return o1.uid_ - o2.uid_;
+    });
+
+    var anyNonEmpty = false;
+    observers.forEach(function(observer) {
+
+      // 2.1, 2.2
+      var queue = observer.takeRecords();
+      // 2.3. Remove all transient registered observers whose observer is mo.
+      removeTransientObserversFor(observer);
+
+      // 2.4
+      if (queue.length) {
+        observer.callback_(queue, observer);
+        anyNonEmpty = true;
+      }
+    });
+
+    // 3.
+    if (anyNonEmpty)
+      dispatchCallbacks();
+  }
+
+  function removeTransientObserversFor(observer) {
+    observer.nodes_.forEach(function(node) {
+      var registrations = registrationsTable.get(node);
+      if (!registrations)
+        return;
+      registrations.forEach(function(registration) {
+        if (registration.observer === observer)
+          registration.removeTransientObservers();
+      });
+    });
+  }
+
+  /**
+   * This function is used for the "For each registered observer observer (with
+   * observer's options as options) in target's list of registered observers,
+   * run these substeps:" and the "For each ancestor ancestor of target, and for
+   * each registered observer observer (with options options) in ancestor's list
+   * of registered observers, run these substeps:" part of the algorithms. The
+   * |options.subtree| is checked to ensure that the callback is called
+   * correctly.
+   *
+   * @param {Node} target
+   * @param {function(MutationObserverInit):MutationRecord} callback
+   */
+  function forEachAncestorAndObserverEnqueueRecord(target, callback) {
+    for (var node = target; node; node = node.parentNode) {
+      var registrations = registrationsTable.get(node);
+
+      if (registrations) {
+        for (var j = 0; j < registrations.length; j++) {
+          var registration = registrations[j];
+          var options = registration.options;
+
+          // Only target ignores subtree.
+          if (node !== target && !options.subtree)
+            continue;
+
+          var record = callback(options);
+          if (record)
+            registration.enqueue(record);
+        }
+      }
+    }
+  }
+
+  var uidCounter = 0;
+
+  /**
+   * The class that maps to the DOM MutationObserver interface.
+   * @param {Function} callback.
+   * @constructor
+   */
+  function MutationObserver(callback) {
+    this.callback_ = callback;
+    this.nodes_ = [];
+    this.records_ = [];
+    this.uid_ = ++uidCounter;
+  }
+
+  MutationObserver.prototype = {
+    // TODO(jmesserly): why is this necessary?
+    get constructor() { return MutationObserver; },

[Jennifer Messerly, 2013/07/30 03:27:24]

I have no idea why this is needed. Without it, the constructor is "Object" and
interceptor dispatch fails.

+
+    observe: function(target, options) {
+      target = wrapIfNeeded(target);
+
+      // 1.1
+      if (!options.childList && !options.attributes && !options.characterData ||
+
+          // 1.2
+          options.attributeOldValue && !options.attributes ||
+
+          // 1.3
+          options.attributeFilter && options.attributeFilter.length &&
+              !options.attributes ||
+
+          // 1.4
+          options.characterDataOldValue && !options.characterData) {
+
+        throw new SyntaxError();
+      }
+
+      var registrations = registrationsTable.get(target);
+      if (!registrations)
+        registrationsTable.set(target, registrations = []);
+
+      // 2
+      // If target's list of registered observers already includes a registered
+      // observer associated with the context object, replace that registered
+      // observer's options with options.
+      var registration;
+      for (var i = 0; i < registrations.length; i++) {
+        if (registrations[i].observer === this) {
+          registration = registrations[i];
+          registration.removeListeners();
+          registration.options = options;
+          break;
+        }
+      }
+
+      // 3.
+      // Otherwise, add a new registered observer to target's list of registered
+      // observers with the context object as the observer and options as the
+      // options, and add target to context object's list of nodes on which it
+      // is registered.
+      if (!registration) {
+        registration = new Registration(this, target, options);
+        registrations.push(registration);
+        this.nodes_.push(target);
+      }
+
+      registration.addListeners();
+    },
+
+    disconnect: function() {
+      this.nodes_.forEach(function(node) {
+        var registrations = registrationsTable.get(node);
+        for (var i = 0; i < registrations.length; i++) {
+          var registration = registrations[i];
+          if (registration.observer === this) {
+            registration.removeListeners();
+            registrations.splice(i, 1);
+            // Each node can only have one registered observer associated with
+            // this observer.
+            break;
+          }
+        }
+      }, this);
+      this.records_ = [];
+    },
+
+    takeRecords: function() {
+      var copyOfRecords = this.records_;
+      this.records_ = [];
+      return copyOfRecords;
+    }
+  };
+
+  /**
+   * @param {string} type
+   * @param {Node} target
+   * @constructor
+   */
+  function MutationRecord(type, target) {
+    this.type = type;
+    this.target = target;
+    this.addedNodes = [];
+    this.removedNodes = [];
+    this.previousSibling = null;
+    this.nextSibling = null;
+    this.attributeName = null;
+    this.attributeNamespace = null;
+    this.oldValue = null;
+  }
+
+  function copyMutationRecord(original) {
+    var record = new MutationRecord(original.type, original.target);
+    record.addedNodes = original.addedNodes.slice();
+    record.removedNodes = original.removedNodes.slice();
+    record.previousSibling = original.previousSibling;
+    record.nextSibling = original.nextSibling;
+    record.attributeName = original.attributeName;
+    record.attributeNamespace = original.attributeNamespace;
+    record.oldValue = original.oldValue;
+    return record;
+  };
+
+  // We keep track of the two (possibly one) records used in a single mutation.
+  var currentRecord, recordWithOldValue;
+
+  /**
+   * Creates a record without |oldValue| and caches it as |currentRecord| for
+   * later use.
+   * @param {string} oldValue
+   * @return {MutationRecord}
+   */
+  function getRecord(type, target) {
+    return currentRecord = new MutationRecord(type, target);
+  }
+
+  /**
+   * Gets or creates a record with |oldValue| based in the |currentRecord|
+   * @param {string} oldValue
+   * @return {MutationRecord}
+   */
+  function getRecordWithOldValue(oldValue) {
+    if (recordWithOldValue)
+      return recordWithOldValue;
+    recordWithOldValue = copyMutationRecord(currentRecord);
+    recordWithOldValue.oldValue = oldValue;
+    return recordWithOldValue;
+  }
+
+  function clearRecords() {
+    currentRecord = recordWithOldValue = undefined;
+  }
+
+  /**
+   * @param {MutationRecord} record
+   * @return {boolean} Whether the record represents a record from the current
+   * mutation event.
+   */
+  function recordRepresentsCurrentMutation(record) {
+    return record === recordWithOldValue || record === currentRecord;
+  }
+
+  /**
+   * Selects which record, if any, to replace the last record in the queue.
+   * This returns |null| if no record should be replaced.
+   *
+   * @param {MutationRecord} lastRecord
+   * @param {MutationRecord} newRecord
+   * @param {MutationRecord}
+   */
+  function selectRecord(lastRecord, newRecord) {
+    if (lastRecord === newRecord)
+      return lastRecord;
+
+    // Check if the the record we are adding represents the same record. If
+    // so, we keep the one with the oldValue in it.
+    if (recordWithOldValue && recordRepresentsCurrentMutation(lastRecord))
+      return recordWithOldValue;
+
+    return null;
+  }
+
+  /**
+   * Class used to represent a registered observer.
+   * @param {MutationObserver} observer
+   * @param {Node} target
+   * @param {MutationObserverInit} options
+   * @constructor
+   */
+  function Registration(observer, target, options) {
+    this.observer = observer;
+    this.target = target;
+    this.options = options;
+    this.transientObservedNodes = [];
+  }
+
+  Registration.prototype = {
+    enqueue: function(record) {
+      var records = this.observer.records_;
+      var length = records.length;
+
+      // There are cases where we replace the last record with the new record.
+      // For example if the record represents the same mutation we need to use
+      // the one with the oldValue. If we get same record (this can happen as we
+      // walk up the tree) we ignore the new record.
+      if (records.length > 0) {
+        var lastRecord = records[length - 1];
+        var recordToReplaceLast = selectRecord(lastRecord, record);
+        if (recordToReplaceLast) {
+          records[length - 1] = recordToReplaceLast;
+          return;
+        }
+      } else {
+        scheduleCallback(this.observer);
+      }
+
+      records[length] = record;
+    },
+
+    addListeners: function() {
+      this.addListeners_(this.target);
+    },
+
+    addListeners_: function(node) {
+      var options = this.options;
+      if (options.attributes)
+        node.addEventListener('DOMAttrModified', this, true);
+
+      if (options.characterData)
+        node.addEventListener('DOMCharacterDataModified', this, true);
+
+      if (options.childList)
+        node.addEventListener('DOMNodeInserted', this, true);
+
+      if (options.childList || options.subtree)
+        node.addEventListener('DOMNodeRemoved', this, true);
+    },
+
+    removeListeners: function() {
+      this.removeListeners_(this.target);
+    },
+
+    removeListeners_: function(node) {
+      var options = this.options;
+      if (options.attributes)
+        node.removeEventListener('DOMAttrModified', this, true);
+
+      if (options.characterData)
+        node.removeEventListener('DOMCharacterDataModified', this, true);
+
+      if (options.childList)
+        node.removeEventListener('DOMNodeInserted', this, true);
+
+      if (options.childList || options.subtree)
+        node.removeEventListener('DOMNodeRemoved', this, true);
+    },
+
+    /**
+     * Adds a transient observer on node. The transient observer gets removed
+     * next time we deliver the change records.
+     * @param {Node} node
+     */
+    addTransientObserver: function(node) {
+      // Don't add transient observers on the target itself. We already have all
+      // the required listeners set up on the target.
+      if (node === this.target)
+        return;
+
+      this.addListeners_(node);
+      this.transientObservedNodes.push(node);
+      var registrations = registrationsTable.get(node);
+      if (!registrations)
+        registrationsTable.set(node, registrations = []);
+
+      // We know that registrations does not contain this because we already
+      // checked if node === this.target.
+      registrations.push(this);
+    },
+
+    removeTransientObservers: function() {
+      var transientObservedNodes = this.transientObservedNodes;
+      this.transientObservedNodes = [];
+
+      transientObservedNodes.forEach(function(node) {
+        // Transient observers are never added to the target.
+        this.removeListeners_(node);
+
+        var registrations = registrationsTable.get(node);
+        for (var i = 0; i < registrations.length; i++) {
+          if (registrations[i] === this) {
+            registrations.splice(i, 1);
+            // Each node can only have one registered observer associated with
+            // this observer.
+            break;
+          }
+        }
+      }, this);
+    },
+
+    handleEvent: function(e) {
+      // Stop propagation since we are managing the propagation manually.
+      // This means that other mutation events on the page will not work
+      // correctly but that is by design.
+      e.stopImmediatePropagation();
+
+      switch (e.type) {
+        case 'DOMAttrModified':
+          // http://dom.spec.whatwg.org/#concept-mo-queue-attributes
+
+          var name = e.attrName;
+          var namespace = e.relatedNode.namespaceURI;
+          var target = e.target;
+
+          // 1.
+          var record = new getRecord('attributes', target);
+          record.attributeName = name;
+          record.attributeNamespace = namespace;
+
+          // 2.
+          var oldValue =
+              e.attrChange === MutationEvent.ADDITION ? null : e.prevValue;
+
+          forEachAncestorAndObserverEnqueueRecord(target, function(options) {
+            // 3.1, 4.2
+            if (!options.attributes)
+              return;
+
+            // 3.2, 4.3
+            if (options.attributeFilter && options.attributeFilter.length &&
+                options.attributeFilter.indexOf(name) === -1 &&
+                options.attributeFilter.indexOf(namespace) === -1) {
+              return;
+            }
+            // 3.3, 4.4
+            if (options.attributeOldValue)
+              return getRecordWithOldValue(oldValue);
+
+            // 3.4, 4.5
+            return record;
+          });
+
+          break;
+
+        case 'DOMCharacterDataModified':
+          // http://dom.spec.whatwg.org/#concept-mo-queue-characterdata
+          var target = e.target;
+
+          // 1.
+          var record = getRecord('characterData', target);
+
+          // 2.
+          var oldValue = e.prevValue;
+
+
+          forEachAncestorAndObserverEnqueueRecord(target, function(options) {
+            // 3.1, 4.2
+            if (!options.characterData)
+              return;
+
+            // 3.2, 4.3
+            if (options.characterDataOldValue)
+              return getRecordWithOldValue(oldValue);
+
+            // 3.3, 4.4
+            return record;
+          });
+
+          break;
+
+        case 'DOMNodeRemoved':
+          this.addTransientObserver(e.target);
+          // Fall through.
+        case 'DOMNodeInserted':
+          // http://dom.spec.whatwg.org/#concept-mo-queue-childlist
+          var target = e.relatedNode;
+          var changedNode = e.target;
+          var addedNodes, removedNodes;
+          if (e.type === 'DOMNodeInserted') {
+            addedNodes = [changedNode];
+            removedNodes = [];
+          } else {
+
+            addedNodes = [];
+            removedNodes = [changedNode];
+          }
+          var previousSibling = changedNode.previousSibling;
+          var nextSibling = changedNode.nextSibling;
+
+          // 1.
+          var record = getRecord('childList', target);
+          record.addedNodes = addedNodes;
+          record.removedNodes = removedNodes;
+          record.previousSibling = previousSibling;
+          record.nextSibling = nextSibling;
+
+          forEachAncestorAndObserverEnqueueRecord(target, function(options) {
+            // 2.1, 3.2
+            if (!options.childList)
+              return;
+
+            // 2.2, 3.3
+            return record;
+          });
+
+      }
+
+      clearRecords();
+    }
+  };
+
+  global.MutationObserver = MutationObserver;
+})(window);
+
+}