text: /**
   * @license
   * Visual Blocks Editor
   *
   * Copyright 2011 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 The class representing one block.
   * @author fraser@google.com (Neil Fraser)
   */
  'use strict';
  
  goog.provide('Blockly.Block');
  
  goog.require('Blockly.Blocks');
  goog.require('Blockly.Comment');
  goog.require('Blockly.Connection');
  goog.require('Blockly.Input');
  goog.require('Blockly.Mutator');
  goog.require('Blockly.Warning');
  goog.require('Blockly.Workspace');
  goog.require('Blockly.Xml');
  goog.require('goog.array');
  goog.require('goog.asserts');
  goog.require('goog.math.Coordinate');
  goog.require('goog.string');
  
  
  /**
   * Class for one block.
   * Not normally called directly, workspace.newBlock() is preferred.
   * @param {!Blockly.Workspace} workspace The block's workspace.
   * @param {?string} prototypeName Name of the language object containing
   *     type-specific functions for this block.
   * @param {=string} opt_id Optional ID.  Use this ID if provided, otherwise
   *     create a new id.
   * @constructor
   */
  Blockly.Block = function(workspace, prototypeName, opt_id) {
    /** @type {string} */
    this.id = (opt_id && !workspace.getBlockById(opt_id)) ?
        opt_id : Blockly.genUid();
    workspace.blockDB_[this.id] = this;
    /** @type {Blockly.Connection} */
    this.outputConnection = null;
    /** @type {Blockly.Connection} */
    this.nextConnection = null;
    /** @type {Blockly.Connection} */
    this.previousConnection = null;
    /** @type {!Array.<!Blockly.Input>} */
    this.inputList = [];
    /** @type {boolean|undefined} */
    this.inputsInline = undefined;
    /** @type {boolean} */
    this.disabled = false;
    /** @type {string|!Function} */
    this.tooltip = '';
    /** @type {boolean} */
    this.contextMenu = true;
  
    /**
     * @type {Blockly.Block}
     * @private
     */
    this.parentBlock_ = null;
  
    /**
     * @type {!Array.<!Blockly.Block>}
     * @private
     */
    this.childBlocks_ = [];
  
    /**
     * @type {boolean}
     * @private
     */
    this.deletable_ = true;
  
    /**
     * @type {boolean}
     * @private
     */
    this.movable_ = true;
  
    /**
     * @type {boolean}
     * @private
     */
    this.editable_ = true;
  
    /**
     * @type {boolean}
     * @private
     */
    this.isShadow_ = false;
  
    /**
     * @type {boolean}
     * @private
     */
    this.collapsed_ = false;
  
    /** @type {string|Blockly.Comment} */
    this.comment = null;
  
    /**
     * @type {!goog.math.Coordinate}
     * @private
     */
    this.xy_ = new goog.math.Coordinate(0, 0);
  
    /** @type {!Blockly.Workspace} */
    this.workspace = workspace;
    /** @type {boolean} */
    this.isInFlyout = workspace.isFlyout;
    /** @type {boolean} */
    this.RTL = workspace.RTL;
  
    // Copy the type-specific functions and data from the prototype.
    if (prototypeName) {
      /** @type {string} */
      this.type = prototypeName;
      var prototype = Blockly.Blocks[prototypeName];
      goog.asserts.assertObject(prototype,
          'Error: "%s" is an unknown language block.', prototypeName);
      goog.mixin(this, prototype);
    }
  
    workspace.addTopBlock(this);
  
    // Call an initialization function, if it exists.
    if (goog.isFunction(this.init)) {
      this.init();
    }
    // Record initial inline state.
    /** @type {boolean|undefined} */
    this.inputsInlineDefault = this.inputsInline;
    /** @type {number|undefined} */
    this.lineNumber = undefined;
    if (Blockly.Events.isEnabled()) {
      Blockly.Events.fire(new Blockly.Events.Create(this));
    }
    // Bind an onchange function, if it exists.
    if (goog.isFunction(this.onchange)) {
      this.onchangeWrapper_ = this.onchange.bind(this);
      this.workspace.addChangeListener(this.onchangeWrapper_);
    }
  };
  
  /**
   * Obtain a newly created block.
   * @param {!Blockly.Workspace} workspace The block's workspace.
   * @param {?string} prototypeName Name of the language object containing
   *     type-specific functions for this block.
   * @return {!Blockly.Block} The created block.
   * @deprecated December 2015
   */
  Blockly.Block.obtain = function(workspace, prototypeName) {
    console.warn('Deprecated call to Blockly.Block.obtain, ' +
                 'use workspace.newBlock instead.');
    return workspace.newBlock(prototypeName);
  };
  
  /**
   * Optional text data that round-trips beween blocks and XML.
   * Has no effect. May be used by 3rd parties for meta information.
   * @type {?string}
   */
  Blockly.Block.prototype.data = null;
  
  /**
   * Colour of the block in '#RRGGBB' format.
   * @type {string}
   * @private
   */
  Blockly.Block.prototype.colour_ = '#000000';
  
  /**
   * Dispose of this block.
   * @param {boolean} healStack If true, then try to heal any gap by connecting
   *     the next statement with the previous statement.  Otherwise, dispose of
   *     all children of this block.
   */
  Blockly.Block.prototype.dispose = function(healStack) {
    // Terminate onchange event calls.
    if (this.onchangeWrapper_) {
      this.workspace.removeChangeListener(this.onchangeWrapper_);
    }
    this.unplug(healStack);
    if (Blockly.Events.isEnabled()) {
      Blockly.Events.fire(new Blockly.Events.Delete(this));
    }
    Blockly.Events.disable();
  
    try {
      // This block is now at the top of the workspace.
      // Remove this block from the workspace's list of top-most blocks.
      if (this.workspace) {
        this.workspace.removeTopBlock(this);
        // Remove from block database.
        delete this.workspace.blockDB_[this.id];
        this.workspace = null;
      }
  
      // Just deleting this block from the DOM would result in a memory leak as
      // well as corruption of the connection database.  Therefore we must
      // methodically step through the blocks and carefully disassemble them.
  
      // First, dispose of all my children.
      for (var i = this.childBlocks_.length - 1; i >= 0; i--) {
        this.childBlocks_[i].dispose(false);
      }
      // Then dispose of myself.
      // Dispose of all inputs and their fields.
      for (var i = 0, input; input = this.inputList[i]; i++) {
        input.dispose();
      }
      this.inputList.length = 0;
      // Dispose of any remaining connections (next/previous/output).
      var connections = this.getConnections_(true);
      for (var i = 0; i < connections.length; i++) {
        var connection = connections[i];
        if (connection.isConnected()) {
          connection.disconnect();
        }
        connections[i].dispose();
      }
    } finally {
      Blockly.Events.enable();
    }
  };
  
  /**
   * Unplug this block from its superior block.  If this block is a statement,
   * optionally reconnect the block underneath with the block on top.
   * @param {boolean} opt_healStack Disconnect child statement and reconnect
   *   stack.  Defaults to false.
   */
  Blockly.Block.prototype.unplug = function(opt_healStack) {
    if (this.outputConnection) {
      if (this.outputConnection.isConnected()) {
        // Disconnect from any superior block.
        this.outputConnection.disconnect();
      }
    } else if (this.previousConnection) {
      var previousTarget = null;
      if (this.previousConnection.isConnected()) {
        // Remember the connection that any next statements need to connect to.
        previousTarget = this.previousConnection.targetConnection;
        // Detach this block from the parent's tree.
        this.previousConnection.disconnect();
      }
      var nextBlock = this.getNextBlock();
      if (opt_healStack && nextBlock) {
        // Disconnect the next statement.
        var nextTarget = this.nextConnection.targetConnection;
        nextTarget.disconnect();
        if (previousTarget && previousTarget.checkType_(nextTarget)) {
          // Attach the next statement to the previous statement.
          previousTarget.connect(nextTarget);
        }
      }
    }
  };
  
  /**
   * Returns all connections originating from this block.
   * @return {!Array.<!Blockly.Connection>} Array of connections.
   * @private
   */
  Blockly.Block.prototype.getConnections_ = function() {
    var myConnections = [];
    if (this.outputConnection) {
      myConnections.push(this.outputConnection);
    }
    if (this.previousConnection) {
      myConnections.push(this.previousConnection);
    }
    if (this.nextConnection) {
      myConnections.push(this.nextConnection);
    }
    for (var i = 0, input; input = this.inputList[i]; i++) {
      if (input.connection) {
        myConnections.push(input.connection);
      }
    }
    return myConnections;
  };
  
  /**
   * Walks down a stack of blocks and finds the last next connection on the stack.
   * @return {Blockly.Connection} The last next connection on the stack, or null.
   * @private
   */
  Blockly.Block.prototype.lastConnectionInStack_ = function() {
    var nextConnection = this.nextConnection;
    while (nextConnection) {
      var nextBlock = nextConnection.targetBlock();
      if (!nextBlock) {
        // Found a next connection with nothing on the other side.
        return nextConnection;
      }
      nextConnection = nextBlock.nextConnection;
    }
    // Ran out of next connections.
    return null;
  };
  
  /**
   * Bump unconnected blocks out of alignment.  Two blocks which aren't actually
   * connected should not coincidentally line up on screen.
   * @private
   */
  Blockly.Block.prototype.bumpNeighbours_ = function() {
    if (!this.workspace) {
      return;  // Deleted block.
    }
    if (Blockly.dragMode_ != Blockly.DRAG_NONE) {
      return;  // Don't bump blocks during a drag.
    }
    var rootBlock = this.getRootBlock();
    if (rootBlock.isInFlyout) {
      return;  // Don't move blocks around in a flyout.
    }
    // Loop though every connection on this block.
    var myConnections = this.getConnections_(false);
    for (var i = 0, connection; connection = myConnections[i]; i++) {
      // Spider down from this block bumping all sub-blocks.
      if (connection.isConnected() && connection.isSuperior()) {
        connection.targetBlock().bumpNeighbours_();
      }
  
      var neighbours = connection.neighbours_(Blockly.SNAP_RADIUS);
      for (var j = 0, otherConnection; otherConnection = neighbours[j]; j++) {
        // If both connections are connected, that's probably fine.  But if
        // either one of them is unconnected, then there could be confusion.
        if (!connection.isConnected() || !otherConnection.isConnected()) {
          // Only bump blocks if they are from different tree structures.
          if (otherConnection.getSourceBlock().getRootBlock() != rootBlock) {
            // Always bump the inferior block.
            if (connection.isSuperior()) {
              otherConnection.bumpAwayFrom_(connection);
            } else {
              connection.bumpAwayFrom_(otherConnection);
            }
          }
        }
      }
    }
  };
  
  /**
   * Return the parent block or null if this block is at the top level.
   * @return {Blockly.Block} The block that holds the current block.
   */
  Blockly.Block.prototype.getParent = function() {
    // Look at the DOM to see if we are nested in another block.
    return this.parentBlock_;
  };
  
  /**
   * Return the input that connects to the specified block.
   * @param {!Blockly.Block} block A block connected to an input on this block.
   * @return {Blockly.Input} The input that connects to the specified block.
   */
  Blockly.Block.prototype.getInputWithBlock = function(block) {
    for (var i = 0, input; input = this.inputList[i]; i++) {
      if (input.connection && input.connection.targetBlock() == block) {
        return input;
      }
    }
    return null;
  };
  
  /**
   * Return the parent block that surrounds the current block, or null if this
   * block has no surrounding block.  A parent block might just be the previous
   * statement, whereas the surrounding block is an if statement, while loop, etc.
   * @return {Blockly.Block} The block that surrounds the current block.
   */
  Blockly.Block.prototype.getSurroundParent = function() {
    var block = this;
    do {
      var prevBlock = block;
      block = block.getParent();
      if (!block) {
        // Ran off the top.
        return null;
      }
    } while (block.getNextBlock() == prevBlock);
    // This block is an enclosing parent, not just a statement in a stack.
    return block;
  };
  
  /**
   * Return the next statement block directly connected to this block.
   * @return {Blockly.Block} The next statement block or null.
   */
  Blockly.Block.prototype.getNextBlock = function() {
    return this.nextConnection && this.nextConnection.targetBlock();
  };
  
  /**
   * Return the top-most block in this block's tree.
   * This will return itself if this block is at the top level.
   * @return {!Blockly.Block} The root block.
   */
  Blockly.Block.prototype.getRootBlock = function() {
    var rootBlock;
    var block = this;
    do {
      rootBlock = block;
      block = rootBlock.parentBlock_;
    } while (block);
    return rootBlock;
  };
  
  /**
   * Find all the blocks that are directly nested inside this one.
   * Includes value and block inputs, as well as any following statement.
   * Excludes any connection on an output tab or any preceding statement.
   * @return {!Array.<!Blockly.Block>} Array of blocks.
   */
  Blockly.Block.prototype.getChildren = function() {
    return this.childBlocks_;
  };
  
  /**
   * Set parent of this block to be a new block or null.
   * @param {Blockly.Block} newParent New parent block.
   */
  Blockly.Block.prototype.setParent = function(newParent) {
    if (newParent == this.parentBlock_) {
      return;
    }
    if (this.parentBlock_) {
      // Remove this block from the old parent's child list.
      var children = this.parentBlock_.childBlocks_;
      for (var child, x = 0; child = children[x]; x++) {
        if (child == this) {
          children.splice(x, 1);
          break;
        }
      }
  
      // Disconnect from superior blocks.
      if (this.previousConnection && this.previousConnection.isConnected()) {
        throw 'Still connected to previous block.';
      }
      if (this.outputConnection && this.outputConnection.isConnected()) {
        throw 'Still connected to parent block.';
      }
      this.parentBlock_ = null;
      // This block hasn't actually moved on-screen, so there's no need to update
      // its connection locations.
    } else {
      // Remove this block from the workspace's list of top-most blocks.
      this.workspace.removeTopBlock(this);
    }
  
    this.parentBlock_ = newParent;
    if (newParent) {
      // Add this block to the new parent's child list.
      newParent.childBlocks_.push(this);
    } else {
      this.workspace.addTopBlock(this);
    }
  };
  
  /**
   * Find all the blocks that are directly or indirectly nested inside this one.
   * Includes this block in the list.
   * Includes value and block inputs, as well as any following statements.
   * Excludes any connection on an output tab or any preceding statements.
   * @return {!Array.<!Blockly.Block>} Flattened array of blocks.
   */
  Blockly.Block.prototype.getDescendants = function() {
    var blocks = [this];
    for (var child, x = 0; child = this.childBlocks_[x]; x++) {
      blocks.push.apply(blocks, child.getDescendants());
    }
    return blocks;
  };
  
  /**
   * Get whether this block is deletable or not.
   * @return {boolean} True if deletable.
   */
  Blockly.Block.prototype.isDeletable = function() {
    return this.deletable_ && !this.isShadow_ &&
        !(this.workspace && this.workspace.options.readOnly);
  };
  
  /**
   * Set whether this block is deletable or not.
   * @param {boolean} deletable True if deletable.
   */
  Blockly.Block.prototype.setDeletable = function(deletable) {
    this.deletable_ = deletable;
  };
  
  /**
   * Set the line number of the block.
   * @param {number} lineNumber The corresponding line number.
   */
  Blockly.Block.prototype.setLineNumber = function(lineNumber) {
    this.lineNumber = lineNumber;
  };
  
  /**
   * Get whether this block is deletable or not.
   * @return {number} The corresponding line number.
   */
  Blockly.Block.prototype.getLineNumber = function() {
    return this.lineNumber;
  };
  
  /**
   * Get whether this block is movable or not.
   * @return {boolean} True if movable.
   */
  Blockly.Block.prototype.isMovable = function() {
    return this.movable_ && !this.isShadow_ &&
        !(this.workspace && this.workspace.options.readOnly);
  };
  
  /**
   * Set whether this block is movable or not.
   * @param {boolean} movable True if movable.
   */
  Blockly.Block.prototype.setMovable = function(movable) {
    this.movable_ = movable;
  };
  
  /**
   * Get whether this block is a shadow block or not.
   * @return {boolean} True if a shadow.
   */
  Blockly.Block.prototype.isShadow = function() {
    return this.isShadow_;
  };
  
  /**
   * Set whether this block is a shadow block or not.
   * @param {boolean} shadow True if a shadow.
   */
  Blockly.Block.prototype.setShadow = function(shadow) {
    this.isShadow_ = shadow;
  };
  
  /**
   * Get whether this block is editable or not.
   * @return {boolean} True if editable.
   */
  Blockly.Block.prototype.isEditable = function() {
    return this.editable_ && !(this.workspace && this.workspace.options.readOnly);
  };
  
  /**
   * Set whether this block is editable or not.
   * @param {boolean} editable True if editable.
   */
  Blockly.Block.prototype.setEditable = function(editable) {
    this.editable_ = editable;
    for (var i = 0, input; input = this.inputList[i]; i++) {
      for (var j = 0, field; field = input.fieldRow[j]; j++) {
        field.updateEditable();
      }
    }
  };
  
  /**
   * Set whether the connections are hidden (not tracked in a database) or not.
   * Recursively walk down all child blocks (except collapsed blocks).
   * @param {boolean} hidden True if connections are hidden.
   */
  Blockly.Block.prototype.setConnectionsHidden = function(hidden) {
    if (!hidden && this.isCollapsed()) {
      if (this.outputConnection) {
        this.outputConnection.setHidden(hidden);
      }
      if (this.previousConnection) {
        this.previousConnection.setHidden(hidden);
      }
      if (this.nextConnection) {
        this.nextConnection.setHidden(hidden);
        var child = this.nextConnection.targetBlock();
        if (child) {
          child.setConnectionsHidden(hidden);
        }
      }
    } else {
      var myConnections = this.getConnections_(true);
      for (var i = 0, connection; connection = myConnections[i]; i++) {
        connection.setHidden(hidden);
        if (connection.isSuperior()) {
          var child = connection.targetBlock();
          if (child) {
            child.setConnectionsHidden(hidden);
          }
        }
      }
    }
  };
  
  /**
   * Set the URL of this block's help page.
   * @param {string|Function} url URL string for block help, or function that
   *     returns a URL.  Null for no help.
   */
  Blockly.Block.prototype.setHelpUrl = function(url) {
    this.helpUrl = url;
  };
  
  /**
   * Change the tooltip text for a block.
   * @param {string|!Function} newTip Text for tooltip or a parent element to
   *     link to for its tooltip.  May be a function that returns a string.
   */
  Blockly.Block.prototype.setTooltip = function(newTip) {
    this.tooltip = newTip;
  };
  
  /**
   * Get the colour of a block.
   * @return {string} #RRGGBB string.
   */
  Blockly.Block.prototype.getColour = function() {
    return this.colour_;
  };
  
  /**
   * Change the colour of a block.
   * @param {number|string} colour HSV hue value, or #RRGGBB string.
   */
  Blockly.Block.prototype.setColour = function(colour) {
    var hue = parseFloat(colour);
    if (!isNaN(hue)) {
      this.colour_ = Blockly.hueToRgb(hue);
    } else if (goog.isString(colour) && colour.match(/^#[0-9a-fA-F]{6}$/)) {
      this.colour_ = colour;
    } else {
      throw 'Invalid colour: ' + colour;
    }
  };
  
  /**
   * Returns the named field from a block.
   * @param {string} name The name of the field.
   * @return {Blockly.Field} Named field, or null if field does not exist.
   */
  Blockly.Block.prototype.getField = function(name) {
    for (var i = 0, input; input = this.inputList[i]; i++) {
      for (var j = 0, field; field = input.fieldRow[j]; j++) {
        if (field.name === name) {
          return field;
        }
      }
    }
    return null;
  };
  
  /**
   * Return all variables referenced by this block.
   * @return {!Array.<string>} List of variable names.
   */
  Blockly.Block.prototype.getVars = function() {
    var vars = [];
    for (var i = 0, input; input = this.inputList[i]; i++) {
      for (var j = 0, field; field = input.fieldRow[j]; j++) {
        if (field instanceof Blockly.FieldVariable) {
          vars.push(field.getValue());
        }
      }
    }
    return vars;
  };
  
  /**
   * Notification that a variable is renaming.
   * If the name matches one of this block's variables, rename it.
   * @param {string} oldName Previous name of variable.
   * @param {string} newName Renamed variable.
   */
  Blockly.Block.prototype.renameVar = function(oldName, newName) {
    for (var i = 0, input; input = this.inputList[i]; i++) {
      for (var j = 0, field; field = input.fieldRow[j]; j++) {
        if (field instanceof Blockly.FieldVariable &&
            Blockly.Names.equals(oldName, field.getValue())) {
          field.setValue(newName);
        }
      }
    }
  };
  
  /**
   * Returns the language-neutral value from the field of a block.
   * @param {string} name The name of the field.
   * @return {?string} Value from the field or null if field does not exist.
   */
  Blockly.Block.prototype.getFieldValue = function(name) {
    var field = this.getField(name);
    if (field) {
      return field.getValue();
    }
    return null;
  };
  
  /**
   * Returns the language-neutral value from the field of a block.
   * @param {string} name The name of the field.
   * @return {?string} Value from the field or null if field does not exist.
   * @deprecated December 2013
   */
  Blockly.Block.prototype.getTitleValue = function(name) {
    console.warn('Deprecated call to getTitleValue, use getFieldValue instead.');
    return this.getFieldValue(name);
  };
  
  /**
   * Change the field value for a block (e.g. 'CHOOSE' or 'REMOVE').
   * @param {string} newValue Value to be the new field.
   * @param {string} name The name of the field.
   */
  Blockly.Block.prototype.setFieldValue = function(newValue, name) {
    var field = this.getField(name);
    goog.asserts.assertObject(field, 'Field "%s" not found.', name);
    field.setValue(newValue);
  };
  
  /**
   * Change the field value for a block (e.g. 'CHOOSE' or 'REMOVE').
   * @param {string} newValue Value to be the new field.
   * @param {string} name The name of the field.
   * @deprecated December 2013
   */
  Blockly.Block.prototype.setTitleValue = function(newValue, name) {
    console.warn('Deprecated call to setTitleValue, use setFieldValue instead.');
    this.setFieldValue(newValue, name);
  };
  
  /**
   * Set whether this block can chain onto the bottom of another block.
   * @param {boolean} newBoolean True if there can be a previous statement.
   * @param {string|Array.<string>|null|undefined} opt_check Statement type or
   *     list of statement types.  Null/undefined if any type could be connected.
   */
  Blockly.Block.prototype.setPreviousStatement = function(newBoolean, opt_check) {
    if (newBoolean) {
      if (opt_check === undefined) {
        opt_check = null;
      }
      if (!this.previousConnection) {
        goog.asserts.assert(!this.outputConnection,
            'Remove output connection prior to adding previous connection.');
        this.previousConnection =
            this.makeConnection_(Blockly.PREVIOUS_STATEMENT);
      }
      this.previousConnection.setCheck(opt_check);
    } else {
      if (this.previousConnection) {
        goog.asserts.assert(!this.previousConnection.isConnected(),
            'Must disconnect previous statement before removing connection.');
        this.previousConnection.dispose();
        this.previousConnection = null;
      }
    }
  };
  
  /**
   * Set whether another block can chain onto the bottom of this block.
   * @param {boolean} newBoolean True if there can be a next statement.
   * @param {string|Array.<string>|null|undefined} opt_check Statement type or
   *     list of statement types.  Null/undefined if any type could be connected.
   */
  Blockly.Block.prototype.setNextStatement = function(newBoolean, opt_check) {
    if (newBoolean) {
      if (opt_check === undefined) {
        opt_check = null;
      }
      if (!this.nextConnection) {
        this.nextConnection = this.makeConnection_(Blockly.NEXT_STATEMENT);
      }
      this.nextConnection.setCheck(opt_check);
    } else {
      if (this.nextConnection) {
        goog.asserts.assert(!this.nextConnection.isConnected(),
            'Must disconnect next statement before removing connection.');
        this.nextConnection.dispose();
        this.nextConnection = null;
      }
    }
  };
  
  /**
   * Set whether this block returns a value.
   * @param {boolean} newBoolean True if there is an output.
   * @param {string|Array.<string>|null|undefined} opt_check Returned type or list
   *     of returned types.  Null or undefined if any type could be returned
   *     (e.g. variable get).
   */
  Blockly.Block.prototype.setOutput = function(newBoolean, opt_check) {
    if (newBoolean) {
      if (opt_check === undefined) {
        opt_check = null;
      }
      if (!this.outputConnection) {
        goog.asserts.assert(!this.previousConnection,
            'Remove previous connection prior to adding output connection.');
        this.outputConnection = this.makeConnection_(Blockly.OUTPUT_VALUE);
      }
      this.outputConnection.setCheck(opt_check);
    } else {
      if (this.outputConnection) {
        goog.asserts.assert(!this.outputConnection.isConnected(),
            'Must disconnect output value before removing connection.');
        this.outputConnection.dispose();
        this.outputConnection = null;
      }
    }
  };
  
  /**
   * Set whether value inputs are arranged horizontally or vertically.
   * @param {boolean} newBoolean True if inputs are horizontal.
   */
  Blockly.Block.prototype.setInputsInline = function(newBoolean) {
    if (this.inputsInline != newBoolean) {
      Blockly.Events.fire(new Blockly.Events.Change(
          this, 'inline', null, this.inputsInline, newBoolean));
      this.inputsInline = newBoolean;
    }
  };
  
  /**
   * Get whether value inputs are arranged horizontally or vertically.
   * @return {boolean} True if inputs are horizontal.
   */
  Blockly.Block.prototype.getInputsInline = function() {
    if (this.inputsInline != undefined) {
      // Set explicitly.
      return this.inputsInline;
    }
    // Not defined explicitly.  Figure out what would look best.
    for (var i = 1; i < this.inputList.length; i++) {
      if (this.inputList[i - 1].type == Blockly.DUMMY_INPUT &&
          this.inputList[i].type == Blockly.DUMMY_INPUT) {
        // Two dummy inputs in a row.  Don't inline them.
        return false;
      }
    }
    for (var i = 1; i < this.inputList.length; i++) {
      if (this.inputList[i - 1].type == Blockly.INPUT_VALUE &&
          this.inputList[i].type == Blockly.DUMMY_INPUT) {
        // Dummy input after a value input.  Inline them.
        return true;
      }
    }
    return false;
  };
  
  /**
   * Set whether the block is disabled or not.
   * @param {boolean} disabled True if disabled.
   */
  Blockly.Block.prototype.setDisabled = function(disabled) {
    if (this.disabled != disabled) {
      Blockly.Events.fire(new Blockly.Events.Change(
          this, 'disabled', null, this.disabled, disabled));
      this.disabled = disabled;
    }
  };
  
  /**
   * Get whether the block is disabled or not due to parents.
   * The block's own disabled property is not considered.
   * @return {boolean} True if disabled.
   */
  Blockly.Block.prototype.getInheritedDisabled = function() {
    var block = this;
    while (true) {
      block = block.getSurroundParent();
      if (!block) {
        // Ran off the top.
        return false;
      } else if (block.disabled) {
        return true;
      }
    }
  };
  
  /**
   * Get whether the block is collapsed or not.
   * @return {boolean} True if collapsed.
   */
  Blockly.Block.prototype.isCollapsed = function() {
    return this.collapsed_;
  };
  
  /**
   * Set whether the block is collapsed or not.
   * @param {boolean} collapsed True if collapsed.
   */
  Blockly.Block.prototype.setCollapsed = function(collapsed) {
    if (this.collapsed_ != collapsed) {
      Blockly.Events.fire(new Blockly.Events.Change(
          this, 'collapsed', null, this.collapsed_, collapsed));
      this.collapsed_ = collapsed;
    }
  };
  
  /**
   * Create a human-readable text representation of this block and any children.
   * @param {number=} opt_maxLength Truncate the string to this length.
   * @return {string} Text of block.
   */
  Blockly.Block.prototype.toString = function(opt_maxLength) {
    var text = [];
    if (this.collapsed_) {
      text.push(this.getInput('_TEMP_COLLAPSED_INPUT').fieldRow[0].text_);
    } else {
      for (var i = 0, input; input = this.inputList[i]; i++) {
        for (var j = 0, field; field = input.fieldRow[j]; j++) {
          text.push(field.getText());
        }
        if (input.connection) {
          var child = input.connection.targetBlock();
          if (child) {
            text.push(child.toString());
          } else {
            text.push('?');
          }
        }
      }
    }
    text = goog.string.trim(text.join(' ')) || '???';
    if (opt_maxLength) {
      // TODO: Improve truncation so that text from this block is given priority.
      // E.g. "1+2+3+4+5+6+7+8+9=0" should be "...6+7+8+9=0", not "1+2+3+4+5...".
      // E.g. "1+2+3+4+5=6+7+8+9+0" should be "...4+5=6+7...".
      text = goog.string.truncate(text, opt_maxLength);
    }
    return text;
  };
  
  /**
   * Shortcut for appending a value input row.
   * @param {string} name Language-neutral identifier which may used to find this
   *     input again.  Should be unique to this block.
   * @return {!Blockly.Input} The input object created.
   */
  Blockly.Block.prototype.appendValueInput = function(name) {
    return this.appendInput_(Blockly.INPUT_VALUE, name);
  };
  
  /**
   * Shortcut for appending a statement input row.
   * @param {string} name Language-neutral identifier which may used to find this
   *     input again.  Should be unique to this block.
   * @return {!Blockly.Input} The input object created.
   */
  Blockly.Block.prototype.appendStatementInput = function(name) {
    return this.appendInput_(Blockly.NEXT_STATEMENT, name);
  };
  
  /**
   * Shortcut for appending a dummy input row.
   * @param {string=} opt_name Language-neutral identifier which may used to find
   *     this input again.  Should be unique to this block.
   * @return {!Blockly.Input} The input object created.
   */
  Blockly.Block.prototype.appendDummyInput = function(opt_name) {
    return this.appendInput_(Blockly.DUMMY_INPUT, opt_name || '');
  };
  
  /**
   * Initialize this block using a cross-platform, internationalization-friendly
   * JSON description.
   * @param {!Object} json Structured data describing the block.
   */
  Blockly.Block.prototype.jsonInit = function(json) {
    // Validate inputs.
    goog.asserts.assert(json['output'] == undefined ||
        json['previousStatement'] == undefined,
        'Must not have both an output and a previousStatement.');
  
    // Set basic properties of block.
    if (json['colour'] !== undefined) {
      this.setColour(json['colour']);
    }
  
    // Interpolate the message blocks.
    var i = 0;
    while (json['message' + i] !== undefined) {
      this.interpolate_(json['message' + i], json['args' + i] || [],
          json['lastDummyAlign' + i]);
      i++;
    }
  
    if (json['inputsInline'] !== undefined) {
      this.setInputsInline(json['inputsInline']);
    }
    // Set output and previous/next connections.
    if (json['output'] !== undefined) {
      this.setOutput(true, json['output']);
    }
    if (json['previousStatement'] !== undefined) {
      this.setPreviousStatement(true, json['previousStatement']);
    }
    if (json['nextStatement'] !== undefined) {
      this.setNextStatement(true, json['nextStatement']);
    }
    if (json['tooltip'] !== undefined) {
      this.setTooltip(json['tooltip']);
    }
    if (json['helpUrl'] !== undefined) {
      this.setHelpUrl(json['helpUrl']);
    }
  };
  
  /**
   * Interpolate a message description onto the block.
   * @param {string} message Text contains interpolation tokens (%1, %2, ...)
   *     that match with fields or inputs defined in the args array.
   * @param {!Array} args Array of arguments to be interpolated.
   * @param {=string} lastDummyAlign If a dummy input is added at the end,
   *     how should it be aligned?
   * @private
   */
  Blockly.Block.prototype.interpolate_ = function(message, args, lastDummyAlign) {
    var tokens = Blockly.utils.tokenizeInterpolation(message);
    // Interpolate the arguments.  Build a list of elements.
    var indexDup = [];
    var indexCount = 0;
    var elements = [];
    for (var i = 0; i < tokens.length; i++) {
      var token = tokens[i];
      if (typeof token == 'number') {
        goog.asserts.assert(token > 0 && token <= args.length,
            'Message index "%s" out of range.', token);
        goog.asserts.assert(!indexDup[token],
            'Message index "%s" duplicated.', token);
        indexDup[token] = true;
        indexCount++;
        elements.push(args[token - 1]);
      } else {
        token = token.trim();
        if (token) {
          elements.push(token);
        }
      }
    }
    goog.asserts.assert(indexCount == args.length,
        'Message does not reference all %s arg(s).', args.length);
    // Add last dummy input if needed.
    if (elements.length && (typeof elements[elements.length - 1] == 'string' ||
        elements[elements.length - 1]['type'].indexOf('field_') == 0)) {
      var dummyInput = {type: 'input_dummy'};
      if (lastDummyAlign) {
        dummyInput['align'] = lastDummyAlign;
      }
      elements.push(dummyInput);
    }
    // Lookup of alignment constants.
    var alignmentLookup = {
      'LEFT': Blockly.ALIGN_LEFT,
      'RIGHT': Blockly.ALIGN_RIGHT,
      'CENTRE': Blockly.ALIGN_CENTRE
    };
    // Populate block with inputs and fields.
    var fieldStack = [];
    for (var i = 0; i < elements.length; i++) {
      var element = elements[i];
      if (typeof element == 'string') {
        fieldStack.push([element, undefined]);
      } else {
        var field = null;
        var input = null;
        do {
          var altRepeat = false;
          if (typeof element == 'string') {
            field = new Blockly.FieldLabel(element);
          } else {
            switch (element['type']) {
              case 'input_value':
                input = this.appendValueInput(element['name']);
                break;
              case 'input_statement':
                input = this.appendStatementInput(element['name']);
                break;
              case 'input_dummy':
                input = this.appendDummyInput(element['name']);
                break;
              case 'field_label':
                field = new Blockly.FieldLabel(element['text'], element['class']);
                break;
              case 'field_input':
                field = new Blockly.FieldTextInput(element['text']);
                if (typeof element['spellcheck'] == 'boolean') {
                  field.setSpellcheck(element['spellcheck']);
                }
                break;
              case 'field_angle':
                field = new Blockly.FieldAngle(element['angle']);
                break;
              case 'field_checkbox':
                field = new Blockly.FieldCheckbox(
                    element['checked'] ? 'TRUE' : 'FALSE');
                break;
              case 'field_colour':
                field = new Blockly.FieldColour(element['colour']);
                break;
              case 'field_variable':
                field = new Blockly.FieldVariable(element['variable']);
                break;
              case 'field_dropdown':
                field = new Blockly.FieldDropdown(element['options']);
                break;
              case 'field_image':
                field = new Blockly.FieldImage(element['src'],
                    element['width'], element['height'], element['alt']);
                break;
              case 'field_number':
                field = new Blockly.FieldNumber(element['value'],
                    element['min'], element['max'], element['precision']);
                break;
              case 'field_date':
                if (Blockly.FieldDate) {
                  field = new Blockly.FieldDate(element['date']);
                  break;
                }
                // Fall through if FieldDate is not compiled in.
              default:
                // Unknown field.
                if (element['alt']) {
                  element = element['alt'];
                  altRepeat = true;
                }
            }
          }
        } while (altRepeat);
        if (field) {
          fieldStack.push([field, element['name']]);
        } else if (input) {
          if (element['check']) {
            input.setCheck(element['check']);
          }
          if (element['align']) {
            input.setAlign(alignmentLookup[element['align']]);
          }
          for (var j = 0; j < fieldStack.length; j++) {
            input.appendField(fieldStack[j][0], fieldStack[j][1]);
          }
          fieldStack.length = 0;
        }
      }
    }
  };
  
  /**
   * Add a value input, statement input or local variable to this block.
   * @param {number} type Either Blockly.INPUT_VALUE or Blockly.NEXT_STATEMENT or
   *     Blockly.DUMMY_INPUT.
   * @param {string} name Language-neutral identifier which may used to find this
   *     input again.  Should be unique to this block.
   * @return {!Blockly.Input} The input object created.
   * @private
   */
  Blockly.Block.prototype.appendInput_ = function(type, name) {
    var connection = null;
    if (type == Blockly.INPUT_VALUE || type == Blockly.NEXT_STATEMENT) {
      connection = this.makeConnection_(type);
    }
    var input = new Blockly.Input(type, name, this, connection);
    // Append input to list.
    this.inputList.push(input);
    return input;
  };
  
  /**
   * Move a named input to a different location on this block.
   * @param {string} name The name of the input to move.
   * @param {?string} refName Name of input that should be after the moved input,
   *   or null to be the input at the end.
   */
  Blockly.Block.prototype.moveInputBefore = function(name, refName) {
    if (name == refName) {
      return;
    }
    // Find both inputs.
    var inputIndex = -1;
    var refIndex = refName ? -1 : this.inputList.length;
    for (var i = 0, input; input = this.inputList[i]; i++) {
      if (input.name == name) {
        inputIndex = i;
        if (refIndex != -1) {
          break;
        }
      } else if (refName && input.name == refName) {
        refIndex = i;
        if (inputIndex != -1) {
          break;
        }
      }
    }
    goog.asserts.assert(inputIndex != -1, 'Named input "%s" not found.', name);
    goog.asserts.assert(refIndex != -1, 'Reference input "%s" not found.',
                        refName);
    this.moveNumberedInputBefore(inputIndex, refIndex);
  };
  
  /**
   * Move a numbered input to a different location on this block.
   * @param {number} inputIndex Index of the input to move.
   * @param {number} refIndex Index of input that should be after the moved input.
   */
  Blockly.Block.prototype.moveNumberedInputBefore = function(
      inputIndex, refIndex) {
    // Validate arguments.
    goog.asserts.assert(inputIndex != refIndex, 'Can\'t move input to itself.');
    goog.asserts.assert(inputIndex < this.inputList.length,
                        'Input index ' + inputIndex + ' out of bounds.');
    goog.asserts.assert(refIndex <= this.inputList.length,
                        'Reference input ' + refIndex + ' out of bounds.');
    // Remove input.
    var input = this.inputList[inputIndex];
    this.inputList.splice(inputIndex, 1);
    if (inputIndex < refIndex) {
      refIndex--;
    }
    // Reinsert input.
    this.inputList.splice(refIndex, 0, input);
  };
  
  /**
   * Remove an input from this block.
   * @param {string} name The name of the input.
   * @param {boolean=} opt_quiet True to prevent error if input is not present.
   * @throws {goog.asserts.AssertionError} if the input is not present and
   *     opt_quiet is not true.
   */
  Blockly.Block.prototype.removeInput = function(name, opt_quiet) {
    for (var i = 0, input; input = this.inputList[i]; i++) {
      if (input.name == name) {
        if (input.connection && input.connection.isConnected()) {
          input.connection.setShadowDom(null);
          var block = input.connection.targetBlock();
          if (block.isShadow()) {
            // Destroy any attached shadow block.
            block.dispose();
          } else {
            // Disconnect any attached normal block.
            block.unplug();
          }
        }
        input.dispose();
        this.inputList.splice(i, 1);
        return;
      }
    }
    if (!opt_quiet) {
      goog.asserts.fail('Input "%s" not found.', name);
    }
  };
  
  /**
   * Fetches the named input object.
   * @param {string} name The name of the input.
   * @return {Blockly.Input} The input object, or null if input does not exist.
   */
  Blockly.Block.prototype.getInput = function(name) {
    for (var i = 0, input; input = this.inputList[i]; i++) {
      if (input.name == name) {
        return input;
      }
    }
    // This input does not exist.
    return null;
  };
  
  /**
   * Fetches the block attached to the named input.
   * @param {string} name The name of the input.
   * @return {Blockly.Block} The attached value block, or null if the input is
   *     either disconnected or if the input does not exist.
   */
  Blockly.Block.prototype.getInputTargetBlock = function(name) {
    var input = this.getInput(name);
    return input && input.connection && input.connection.targetBlock();
  };
  
  /**
   * Returns the comment on this block (or '' if none).
   * @return {string} Block's comment.
   */
  Blockly.Block.prototype.getCommentText = function() {
    return this.comment || '';
  };
  
  /**
   * Set this block's comment text.
   * @param {?string} text The text, or null to delete.
   */
  Blockly.Block.prototype.setCommentText = function(text) {
    if (this.comment != text) {
      Blockly.Events.fire(new Blockly.Events.Change(
          this, 'comment', null, this.comment, text || ''));
      this.comment = text;
    }
  };
  
  /**
   * Set this block's warning text.
   * @param {?string} text The text, or null to delete.
   */
  Blockly.Block.prototype.setWarningText = function(text) {
    // NOP.
  };
  
  /**
   * Give this block a mutator dialog.
   * @param {Blockly.Mutator} mutator A mutator dialog instance or null to remove.
   */
  Blockly.Block.prototype.setMutator = function(mutator) {
    // NOP.
  };
  
  /**
   * Return the coordinates of the top-left corner of this block relative to the
   * drawing surface's origin (0,0).
   * @return {!goog.math.Coordinate} Object with .x and .y properties.
   */
  Blockly.Block.prototype.getRelativeToSurfaceXY = function() {
    return this.xy_;
  };
  
  /**
   * Move a block by a relative offset.
   * @param {number} dx Horizontal offset.
   * @param {number} dy Vertical offset.
   */
  Blockly.Block.prototype.moveBy = function(dx, dy) {
    goog.asserts.assert(!this.parentBlock_, 'Block has parent.');
    var event = new Blockly.Events.Move(this);
    this.xy_.translate(dx, dy);
    event.recordNew();
    Blockly.Events.fire(event);
  };
  
  /**
   * Create a connection of the specified type.
   * @param {number} type The type of the connection to create.
   * @return {!Blockly.Connection} A new connection of the specified type.
   * @private
   */
  Blockly.Block.prototype.makeConnection_ = function(type) {
    return new Blockly.Connection(this, type);
  };
  