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diff --git a/src/blockly/core/events.js b/src/blockly/core/events.js
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+/**
+ * @license
+ * Visual Blocks Editor
+ *
+ * Copyright 2016 Google Inc.
+ * https://developers.google.com/blockly/
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @fileoverview Events fired as a result of actions in Blockly's editor.
+ * @author fraser@google.com (Neil Fraser)
+ */
+'use strict';
+
+goog.provide('Blockly.Events');
+
+goog.require('goog.math.Coordinate');
+
+
+/**
+ * Group ID for new events.  Grouped events are indivisible.
+ * @type {string}
+ * @private
+ */
+Blockly.Events.group_ = '';
+
+/**
+ * Sets whether events should be added to the undo stack.
+ * @type {boolean}
+ */
+Blockly.Events.recordUndo = true;
+
+/**
+ * Allow change events to be created and fired.
+ * @type {number}
+ * @private
+ */
+Blockly.Events.disabled_ = 0;
+
+/**
+ * Name of event that creates a block.
+ * @const
+ */
+Blockly.Events.CREATE = 'create';
+
+/**
+ * Name of event that deletes a block.
+ * @const
+ */
+Blockly.Events.DELETE = 'delete';
+
+/**
+ * Name of event that changes a block.
+ * @const
+ */
+Blockly.Events.CHANGE = 'change';
+
+/**
+ * Name of event that moves a block.
+ * @const
+ */
+Blockly.Events.MOVE = 'move';
+
+/**
+ * Name of event that records a UI change.
+ * @const
+ */
+Blockly.Events.UI = 'ui';
+
+/**
+ * List of events queued for firing.
+ * @private
+ */
+Blockly.Events.FIRE_QUEUE_ = [];
+
+/**
+ * Create a custom event and fire it.
+ * @param {!Blockly.Events.Abstract} event Custom data for event.
+ */
+Blockly.Events.fire = function(event) {
+  if (!Blockly.Events.isEnabled()) {
+    return;
+  }
+  if (!Blockly.Events.FIRE_QUEUE_.length) {
+    // First event added; schedule a firing of the event queue.
+    setTimeout(Blockly.Events.fireNow_, 0);
+  }
+  Blockly.Events.FIRE_QUEUE_.push(event);
+};
+
+/**
+ * Fire all queued events.
+ * @private
+ */
+Blockly.Events.fireNow_ = function() {
+  var queue = Blockly.Events.filter(Blockly.Events.FIRE_QUEUE_, true);
+  Blockly.Events.FIRE_QUEUE_.length = 0;
+  for (var i = 0, event; event = queue[i]; i++) {
+    var workspace = Blockly.Workspace.getById(event.workspaceId);
+    if (workspace) {
+      workspace.fireChangeListener(event);
+    }
+  }
+};
+
+/**
+ * Filter the queued events and merge duplicates.
+ * @param {!Array.<!Blockly.Events.Abstract>} queueIn Array of events.
+ * @param {boolean} forward True if forward (redo), false if backward (undo).
+ * @return {!Array.<!Blockly.Events.Abstract>} Array of filtered events.
+ */
+Blockly.Events.filter = function(queueIn, forward) {
+  var queue = goog.array.clone(queueIn);
+  if (!forward) {
+    // Undo is merged in reverse order.
+    queue.reverse();
+  }
+  // Merge duplicates.  O(n^2), but n should be very small.
+  for (var i = 0, event1; event1 = queue[i]; i++) {
+    for (var j = i + 1, event2; event2 = queue[j]; j++) {
+      if (event1.type == event2.type &&
+          event1.blockId == event2.blockId &&
+          event1.workspaceId == event2.workspaceId) {
+        if (event1.type == Blockly.Events.MOVE) {
+          // Merge move events.
+          event1.newParentId = event2.newParentId;
+          event1.newInputName = event2.newInputName;
+          event1.newCoordinate = event2.newCoordinate;
+          queue.splice(j, 1);
+          j--;
+        } else if (event1.type == Blockly.Events.CHANGE &&
+            event1.element == event2.element &&
+            event1.name == event2.name) {
+          // Merge change events.
+          event1.newValue = event2.newValue;
+          queue.splice(j, 1);
+          j--;
+        } else if (event1.type == Blockly.Events.UI &&
+            event2.element == 'click' &&
+            (event1.element == 'commentOpen' ||
+             event1.element == 'mutatorOpen' ||
+             event1.element == 'warningOpen')) {
+          // Merge change events.
+          event1.newValue = event2.newValue;
+          queue.splice(j, 1);
+          j--;
+        }
+      }
+    }
+  }
+  // Remove null events.
+  for (var i = queue.length - 1; i >= 0; i--) {
+    if (queue[i].isNull()) {
+      queue.splice(i, 1);
+    }
+  }
+  if (!forward) {
+    // Restore undo order.
+    queue.reverse();
+  }
+  // Move mutation events to the top of the queue.
+  // Intentionally skip first event.
+  for (var i = 1, event; event = queue[i]; i++) {
+    if (event.type == Blockly.Events.CHANGE &&
+        event.element == 'mutation') {
+      queue.unshift(queue.splice(i, 1)[0]);
+    }
+  }
+  return queue;
+};
+
+/**
+ * Modify pending undo events so that when they are fired they don't land
+ * in the undo stack.  Called by Blockly.Workspace.clearUndo.
+ */
+Blockly.Events.clearPendingUndo = function() {
+  for (var i = 0, event; event = Blockly.Events.FIRE_QUEUE_[i]; i++) {
+    event.recordUndo = false;
+  }
+};
+
+/**
+ * Stop sending events.  Every call to this function MUST also call enable.
+ */
+Blockly.Events.disable = function() {
+  Blockly.Events.disabled_++;
+};
+
+/**
+ * Start sending events.  Unless events were already disabled when the
+ * corresponding call to disable was made.
+ */
+Blockly.Events.enable = function() {
+  Blockly.Events.disabled_--;
+};
+
+/**
+ * Returns whether events may be fired or not.
+ * @return {boolean} True if enabled.
+ */
+Blockly.Events.isEnabled = function() {
+  return Blockly.Events.disabled_ == 0;
+};
+
+/**
+ * Current group.
+ * @return {string} ID string.
+ */
+Blockly.Events.getGroup = function() {
+  return Blockly.Events.group_;
+};
+
+/**
+ * Start or stop a group.
+ * @param {boolean|string} state True to start new group, false to end group.
+ *   String to set group explicitly.
+ */
+Blockly.Events.setGroup = function(state) {
+  if (typeof state == 'boolean') {
+    Blockly.Events.group_ = state ? Blockly.genUid() : '';
+  } else {
+    Blockly.Events.group_ = state;
+  }
+};
+
+/**
+ * Compute a list of the IDs of the specified block and all its descendants.
+ * @param {!Blockly.Block} block The root block.
+ * @return {!Array.<string>} List of block IDs.
+ * @private
+ */
+Blockly.Events.getDescendantIds_ = function(block) {
+  var ids = [];
+  var descendants = block.getDescendants();
+  for (var i = 0, descendant; descendant = descendants[i]; i++) {
+    ids[i] = descendant.id;
+  }
+  return ids;
+};
+
+/**
+ * Decode the JSON into an event.
+ * @param {!Object} json JSON representation.
+ * @param {!Blockly.Workspace} workspace Target workspace for event.
+ * @return {!Blockly.Events.Abstract} The event represented by the JSON.
+ */
+Blockly.Events.fromJson = function(json, workspace) {
+  var event;
+  switch (json.type) {
+    case Blockly.Events.CREATE:
+      event = new Blockly.Events.Create(null);
+      break;
+    case Blockly.Events.DELETE:
+      event = new Blockly.Events.Delete(null);
+      break;
+    case Blockly.Events.CHANGE:
+      event = new Blockly.Events.Change(null);
+      break;
+    case Blockly.Events.MOVE:
+      event = new Blockly.Events.Move(null);
+      break;
+    case Blockly.Events.UI:
+      event = new Blockly.Events.Ui(null);
+      break;
+    default:
+      throw 'Unknown event type.';
+  }
+  event.fromJson(json);
+  event.workspaceId = workspace.id;
+  return event;
+};
+
+/**
+ * Abstract class for an event.
+ * @param {Blockly.Block} block The block.
+ * @constructor
+ */
+Blockly.Events.Abstract = function(block) {
+  if (block) {
+    this.blockId = block.id;
+    this.workspaceId = block.workspace.id;
+  }
+  this.group = Blockly.Events.group_;
+  this.recordUndo = Blockly.Events.recordUndo;
+};
+
+/**
+ * Encode the event as JSON.
+ * @return {!Object} JSON representation.
+ */
+Blockly.Events.Abstract.prototype.toJson = function() {
+  var json = {
+    'type': this.type,
+  };
+  if (this.blockId) {
+    json['blockId'] = this.blockId;
+  }
+  if (this.group) {
+    json['group'] = this.group;
+  }
+  return json;
+};
+
+/**
+ * Decode the JSON event.
+ * @param {!Object} json JSON representation.
+ */
+Blockly.Events.Abstract.prototype.fromJson = function(json) {
+  this.blockId = json['blockId'];
+  this.group = json['group'];
+};
+
+/**
+ * Does this event record any change of state?
+ * @return {boolean} True if null, false if something changed.
+ */
+Blockly.Events.Abstract.prototype.isNull = function() {
+  return false;
+};
+
+/**
+ * Run an event.
+ * @param {boolean} forward True if run forward, false if run backward (undo).
+ */
+Blockly.Events.Abstract.prototype.run = function(forward) {
+  // Defined by subclasses.
+};
+
+/**
+ * Class for a block creation event.
+ * @param {Blockly.Block} block The created block.  Null for a blank event.
+ * @extends {Blockly.Events.Abstract}
+ * @constructor
+ */
+Blockly.Events.Create = function(block) {
+  if (!block) {
+    return;  // Blank event to be populated by fromJson.
+  }
+  Blockly.Events.Create.superClass_.constructor.call(this, block);
+  this.xml = Blockly.Xml.blockToDomWithXY(block);
+  this.ids = Blockly.Events.getDescendantIds_(block);
+};
+goog.inherits(Blockly.Events.Create, Blockly.Events.Abstract);
+
+/**
+ * Type of this event.
+ * @type {string}
+ */
+Blockly.Events.Create.prototype.type = Blockly.Events.CREATE;
+
+/**
+ * Encode the event as JSON.
+ * @return {!Object} JSON representation.
+ */
+Blockly.Events.Create.prototype.toJson = function() {
+  var json = Blockly.Events.Create.superClass_.toJson.call(this);
+  json['xml'] = Blockly.Xml.domToText(this.xml);
+  json['ids'] = this.ids;
+  return json;
+};
+
+/**
+ * Decode the JSON event.
+ * @param {!Object} json JSON representation.
+ */
+Blockly.Events.Create.prototype.fromJson = function(json) {
+  Blockly.Events.Create.superClass_.fromJson.call(this, json);
+  this.xml = Blockly.Xml.textToDom('<xml>' + json['xml'] + '</xml>').firstChild;
+  this.ids = json['ids'];
+};
+
+/**
+ * Run a creation event.
+ * @param {boolean} forward True if run forward, false if run backward (undo).
+ */
+Blockly.Events.Create.prototype.run = function(forward) {
+  var workspace = Blockly.Workspace.getById(this.workspaceId);
+  if (forward) {
+    var xml = goog.dom.createDom('xml');
+    xml.appendChild(this.xml);
+    Blockly.Xml.domToWorkspace(xml, workspace);
+  } else {
+    for (var i = 0, id; id = this.ids[i]; i++) {
+      var block = workspace.getBlockById(id);
+      if (block) {
+        block.dispose(false, false);
+      } else if (id == this.blockId) {
+        // Only complain about root-level block.
+        console.warn("Can't uncreate non-existant block: " + id);
+      }
+    }
+  }
+};
+
+/**
+ * Class for a block deletion event.
+ * @param {Blockly.Block} block The deleted block.  Null for a blank event.
+ * @extends {Blockly.Events.Abstract}
+ * @constructor
+ */
+Blockly.Events.Delete = function(block) {
+  if (!block) {
+    return;  // Blank event to be populated by fromJson.
+  }
+  if (block.getParent()) {
+    throw 'Connected blocks cannot be deleted.';
+  }
+  Blockly.Events.Delete.superClass_.constructor.call(this, block);
+  this.oldXml = Blockly.Xml.blockToDomWithXY(block);
+  this.ids = Blockly.Events.getDescendantIds_(block);
+};
+goog.inherits(Blockly.Events.Delete, Blockly.Events.Abstract);
+
+/**
+ * Type of this event.
+ * @type {string}
+ */
+Blockly.Events.Delete.prototype.type = Blockly.Events.DELETE;
+
+/**
+ * Encode the event as JSON.
+ * @return {!Object} JSON representation.
+ */
+Blockly.Events.Delete.prototype.toJson = function() {
+  var json = Blockly.Events.Delete.superClass_.toJson.call(this);
+  json['ids'] = this.ids;
+  return json;
+};
+
+/**
+ * Decode the JSON event.
+ * @param {!Object} json JSON representation.
+ */
+Blockly.Events.Delete.prototype.fromJson = function(json) {
+  Blockly.Events.Delete.superClass_.fromJson.call(this, json);
+  this.ids = json['ids'];
+};
+
+/**
+ * Run a deletion event.
+ * @param {boolean} forward True if run forward, false if run backward (undo).
+ */
+Blockly.Events.Delete.prototype.run = function(forward) {
+  var workspace = Blockly.Workspace.getById(this.workspaceId);
+  if (forward) {
+    for (var i = 0, id; id = this.ids[i]; i++) {
+      var block = workspace.getBlockById(id);
+      if (block) {
+        block.dispose(false, false);
+      } else if (id == this.blockId) {
+        // Only complain about root-level block.
+        console.warn("Can't delete non-existant block: " + id);
+      }
+    }
+  } else {
+    var xml = goog.dom.createDom('xml');
+    xml.appendChild(this.oldXml);
+    Blockly.Xml.domToWorkspace(xml, workspace);
+  }
+};
+
+/**
+ * Class for a block change event.
+ * @param {Blockly.Block} block The changed block.  Null for a blank event.
+ * @param {string} element One of 'field', 'comment', 'disabled', etc.
+ * @param {?string} name Name of input or field affected, or null.
+ * @param {string} oldValue Previous value of element.
+ * @param {string} newValue New value of element.
+ * @extends {Blockly.Events.Abstract}
+ * @constructor
+ */
+Blockly.Events.Change = function(block, element, name, oldValue, newValue) {
+  if (!block) {
+    return;  // Blank event to be populated by fromJson.
+  }
+  Blockly.Events.Change.superClass_.constructor.call(this, block);
+  this.element = element;
+  this.name = name;
+  this.oldValue = oldValue;
+  this.newValue = newValue;
+};
+goog.inherits(Blockly.Events.Change, Blockly.Events.Abstract);
+
+/**
+ * Type of this event.
+ * @type {string}
+ */
+Blockly.Events.Change.prototype.type = Blockly.Events.CHANGE;
+
+/**
+ * Encode the event as JSON.
+ * @return {!Object} JSON representation.
+ */
+Blockly.Events.Change.prototype.toJson = function() {
+  var json = Blockly.Events.Change.superClass_.toJson.call(this);
+  json['element'] = this.element;
+  if (this.name) {
+    json['name'] = this.name;
+  }
+  json['newValue'] = this.newValue;
+  return json;
+};
+
+/**
+ * Decode the JSON event.
+ * @param {!Object} json JSON representation.
+ */
+Blockly.Events.Change.prototype.fromJson = function(json) {
+  Blockly.Events.Change.superClass_.fromJson.call(this, json);
+  this.element = json['element'];
+  this.name = json['name'];
+  this.newValue = json['newValue'];
+};
+
+/**
+ * Does this event record any change of state?
+ * @return {boolean} True if something changed.
+ */
+Blockly.Events.Change.prototype.isNull = function() {
+  return this.oldValue == this.newValue;
+};
+
+/**
+ * Run a change event.
+ * @param {boolean} forward True if run forward, false if run backward (undo).
+ */
+Blockly.Events.Change.prototype.run = function(forward) {
+  var workspace = Blockly.Workspace.getById(this.workspaceId);
+  var block = workspace.getBlockById(this.blockId);
+  if (!block) {
+    console.warn("Can't change non-existant block: " + this.blockId);
+    return;
+  }
+  if (block.mutator) {
+    // Close the mutator (if open) since we don't want to update it.
+    block.mutator.setVisible(false);
+  }
+  var value = forward ? this.newValue : this.oldValue;
+  switch (this.element) {
+    case 'field':
+      var field = block.getField(this.name);
+      if (field) {
+        // Run the validator for any side-effects it may have.
+        // The validator's opinion on validity is ignored.
+        field.callValidator(value);
+        field.setValue(value);
+      } else {
+        console.warn("Can't set non-existant field: " + this.name);
+      }
+      break;
+    case 'comment':
+      block.setCommentText(value || null);
+      break;
+    case 'collapsed':
+      block.setCollapsed(value);
+      break;
+    case 'disabled':
+      block.setDisabled(value);
+      break;
+    case 'inline':
+      block.setInputsInline(value);
+      break;
+    case 'mutation':
+      var oldMutation = '';
+      if (block.mutationToDom) {
+        var oldMutationDom = block.mutationToDom();
+        oldMutation = oldMutationDom && Blockly.Xml.domToText(oldMutationDom);
+      }
+      if (block.domToMutation) {
+        value = value || '<mutation></mutation>';
+        var dom = Blockly.Xml.textToDom('<xml>' + value + '</xml>');
+        block.domToMutation(dom.firstChild);
+      }
+      Blockly.Events.fire(new Blockly.Events.Change(
+          block, 'mutation', null, oldMutation, value));
+      break;
+    default:
+      console.warn('Unknown change type: ' + this.element);
+  }
+};
+
+/**
+ * Class for a block move event.  Created before the move.
+ * @param {Blockly.Block} block The moved block.  Null for a blank event.
+ * @extends {Blockly.Events.Abstract}
+ * @constructor
+ */
+Blockly.Events.Move = function(block) {
+  if (!block) {
+    return;  // Blank event to be populated by fromJson.
+  }
+  Blockly.Events.Move.superClass_.constructor.call(this, block);
+  var location = this.currentLocation_();
+  this.oldParentId = location.parentId;
+  this.oldInputName = location.inputName;
+  this.oldCoordinate = location.coordinate;
+};
+goog.inherits(Blockly.Events.Move, Blockly.Events.Abstract);
+
+/**
+ * Type of this event.
+ * @type {string}
+ */
+Blockly.Events.Move.prototype.type = Blockly.Events.MOVE;
+
+/**
+ * Encode the event as JSON.
+ * @return {!Object} JSON representation.
+ */
+Blockly.Events.Move.prototype.toJson = function() {
+  var json = Blockly.Events.Move.superClass_.toJson.call(this);
+  if (this.newParentId) {
+    json['newParentId'] = this.newParentId;
+  }
+  if (this.newInputName) {
+    json['newInputName'] = this.newInputName;
+  }
+  if (this.newCoordinate) {
+    json['newCoordinate'] = Math.round(this.newCoordinate.x) + ',' +
+        Math.round(this.newCoordinate.y);
+  }
+  return json;
+};
+
+/**
+ * Decode the JSON event.
+ * @param {!Object} json JSON representation.
+ */
+Blockly.Events.Move.prototype.fromJson = function(json) {
+  Blockly.Events.Move.superClass_.fromJson.call(this, json);
+  this.newParentId = json['newParentId'];
+  this.newInputName = json['newInputName'];
+  if (json['newCoordinate']) {
+    var xy = json['newCoordinate'].split(',');
+    this.newCoordinate =
+        new goog.math.Coordinate(parseFloat(xy[0]), parseFloat(xy[1]));
+  }
+};
+
+/**
+ * Record the block's new location.  Called after the move.
+ */
+Blockly.Events.Move.prototype.recordNew = function() {
+  var location = this.currentLocation_();
+  this.newParentId = location.parentId;
+  this.newInputName = location.inputName;
+  this.newCoordinate = location.coordinate;
+};
+
+/**
+ * Returns the parentId and input if the block is connected,
+ *   or the XY location if disconnected.
+ * @return {!Object} Collection of location info.
+ * @private
+ */
+Blockly.Events.Move.prototype.currentLocation_ = function() {
+  var workspace = Blockly.Workspace.getById(this.workspaceId);
+  var block = workspace.getBlockById(this.blockId);
+  var location = {};
+  var parent = block.getParent();
+  if (parent) {
+    location.parentId = parent.id;
+    var input = parent.getInputWithBlock(block);
+    if (input) {
+      location.inputName = input.name;
+    }
+  } else {
+    location.coordinate = block.getRelativeToSurfaceXY();
+  }
+  return location;
+};
+
+/**
+ * Does this event record any change of state?
+ * @return {boolean} True if something changed.
+ */
+Blockly.Events.Move.prototype.isNull = function() {
+  return this.oldParentId == this.newParentId &&
+      this.oldInputName == this.newInputName &&
+      goog.math.Coordinate.equals(this.oldCoordinate, this.newCoordinate);
+};
+
+/**
+ * Run a move event.
+ * @param {boolean} forward True if run forward, false if run backward (undo).
+ */
+Blockly.Events.Move.prototype.run = function(forward) {
+  var workspace = Blockly.Workspace.getById(this.workspaceId);
+  var block = workspace.getBlockById(this.blockId);
+  if (!block) {
+    console.warn("Can't move non-existant block: " + this.blockId);
+    return;
+  }
+  var parentId = forward ? this.newParentId : this.oldParentId;
+  var inputName = forward ? this.newInputName : this.oldInputName;
+  var coordinate = forward ? this.newCoordinate : this.oldCoordinate;
+  var parentBlock = null;
+  if (parentId) {
+    parentBlock = workspace.getBlockById(parentId);
+    if (!parentBlock) {
+      console.warn("Can't connect to non-existant block: " + parentId);
+      return;
+    }
+  }
+  if (block.getParent()) {
+    block.unplug();
+  }
+  if (coordinate) {
+    var xy = block.getRelativeToSurfaceXY();
+    block.moveBy(coordinate.x - xy.x, coordinate.y - xy.y);
+  } else {
+    var blockConnection = block.outputConnection || block.previousConnection;
+    var parentConnection;
+    if (inputName) {
+      var input = parentBlock.getInput(inputName);
+      if (input) {
+        parentConnection = input.connection;
+      }
+    } else if (blockConnection.type == Blockly.PREVIOUS_STATEMENT) {
+      parentConnection = parentBlock.nextConnection;
+    }
+    if (parentConnection) {
+      blockConnection.connect(parentConnection);
+    } else {
+      console.warn("Can't connect to non-existant input: " + inputName);
+    }
+  }
+};
+
+/**
+ * Class for a UI event.
+ * @param {Blockly.Block} block The affected block.
+ * @param {string} element One of 'selected', 'comment', 'mutator', etc.
+ * @param {string} oldValue Previous value of element.
+ * @param {string} newValue New value of element.
+ * @extends {Blockly.Events.Abstract}
+ * @constructor
+ */
+Blockly.Events.Ui = function(block, element, oldValue, newValue) {
+  Blockly.Events.Ui.superClass_.constructor.call(this, block);
+  this.element = element;
+  this.oldValue = oldValue;
+  this.newValue = newValue;
+  this.recordUndo = false;
+};
+goog.inherits(Blockly.Events.Ui, Blockly.Events.Abstract);
+
+/**
+ * Type of this event.
+ * @type {string}
+ */
+Blockly.Events.Ui.prototype.type = Blockly.Events.UI;
+
+/**
+ * Encode the event as JSON.
+ * @return {!Object} JSON representation.
+ */
+Blockly.Events.Ui.prototype.toJson = function() {
+  var json = Blockly.Events.Ui.superClass_.toJson.call(this);
+  json['element'] = this.element;
+  if (this.newValue !== undefined) {
+    json['newValue'] = this.newValue;
+  }
+  return json;
+};
+
+/**
+ * Decode the JSON event.
+ * @param {!Object} json JSON representation.
+ */
+Blockly.Events.Ui.prototype.fromJson = function(json) {
+  Blockly.Events.Ui.superClass_.fromJson.call(this, json);
+  this.element = json['element'];
+  this.newValue = json['newValue'];
+};
+
+/**
+ * Enable/disable a block depending on whether it is properly connected.
+ * Use this on applications where all blocks should be connected to a top block.
+ * Recommend setting the 'disable' option to 'false' in the config so that
+ * users don't try to reenable disabled orphan blocks.
+ * @param {!Blockly.Events.Abstract} event Custom data for event.
+ */
+Blockly.Events.disableOrphans = function(event) {
+  if (event.type == Blockly.Events.MOVE ||
+      event.type == Blockly.Events.CREATE) {
+    Blockly.Events.disable();
+    var workspace = Blockly.Workspace.getById(event.workspaceId);
+    var block = workspace.getBlockById(event.blockId);
+    if (block) {
+      if (block.getParent() && !block.getParent().disabled) {
+        var children = block.getDescendants();
+        for (var i = 0, child; child = children[i]; i++) {
+          child.setDisabled(false);
+        }
+      } else if ((block.outputConnection || block.previousConnection) &&
+                 Blockly.dragMode_ == Blockly.DRAG_NONE) {
+        do {
+          block.setDisabled(true);
+          block = block.getNextBlock();
+        } while (block);
+      }
+    }
+    Blockly.Events.enable();
+  }
+};