diff --git a/.gitignore b/.gitignore
index 53eebc859..4216e2f62 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,4 +5,4 @@ npm-debug.log
 .project
 *.pyc
 *.komodoproject
-/nbproject/private/
\ No newline at end of file
+/nbproject/private/
diff --git a/demos/blockfactory/app_controller.js b/demos/blockfactory/app_controller.js
index e3fc1bd23..16869bdf4 100644
--- a/demos/blockfactory/app_controller.js
+++ b/demos/blockfactory/app_controller.js
@@ -584,9 +584,9 @@ AppController.prototype.addBlockFactoryEventListeners = function() {
   document.getElementById('direction')
       .addEventListener('change', BlockFactory.updatePreview);
   document.getElementById('languageTA')
-      .addEventListener('change', BlockFactory.updatePreview);
+      .addEventListener('change', BlockFactory.manualEdit);
   document.getElementById('languageTA')
-      .addEventListener('keyup', BlockFactory.updatePreview);
+      .addEventListener('keyup', BlockFactory.manualEdit);
   document.getElementById('format')
       .addEventListener('change', BlockFactory.formatChange);
   document.getElementById('language')
diff --git a/demos/blockfactory/block_definition_extractor.js b/demos/blockfactory/block_definition_extractor.js
new file mode 100644
index 000000000..5c907491d
--- /dev/null
+++ b/demos/blockfactory/block_definition_extractor.js
@@ -0,0 +1,749 @@
+/**
+ * Copyright 2017 Juan Carlos Orozco Arena
+ * Apache License Version 2.0
+ */
+
+/**
+ * @fileoverview
+ * The BlockDefinitionExtractor is a class that generates a workspace DOM
+ * suitable for the BlockFactory's block editor, derived from an example
+ * Blockly.Block.
+ *
+ * <code>
+ * var workspaceDom = new BlockDefinitionExtractor()
+ *     .buildBlockFactoryWorkspace(exampleBlocklyBlock);
+ * Blockly.Xml.domToWorkspace(workspaceDom, BlockFactory.mainWorkspace);
+ * </code>
+ *
+ * The <code>exampleBlocklyBlock</code> is usually the block loaded into the
+ * preview workspace after manually entering the block definition.
+ *
+ * @author JC-Orozco (Juan Carlos Orozco), AnmAtAnm (Andrew n marshall)
+ */
+'use strict';
+
+/**
+ * Namespace for BlockDefinitionExtractor.
+ */
+goog.provide('BlockDefinitionExtractor');
+
+
+/**
+ * Class to contain all functions needed to extract block definition from
+ * the block preview data structure.
+ * @namespace
+ */
+BlockDefinitionExtractor = BlockDefinitionExtractor || Object.create(null);
+
+/**
+ * Builds a BlockFactory workspace that reflects the block structure of the
+ * exmaple block.
+ *
+ * @param {!Blockly.Block} block The reference block from which the definition
+ *     will be extracted.
+ * @return {!Element} Returns the root workspace DOM <xml> for the block editor
+ *     workspace.
+ */
+BlockDefinitionExtractor.buildBlockFactoryWorkspace = function(block) {
+  var workspaceXml = goog.dom.createDom('xml');
+  workspaceXml.append(
+      BlockDefinitionExtractor.factoryBase_(block, block.type));
+
+  return workspaceXml;
+};
+
+/**
+ * Helper function to create a new Element with the provided attributes and
+ * inner text.
+ *
+ * @param {string} name New element tag name.
+ * @param {Map<String,String>} opt_attrs Optional list of attributes.
+ * @param {string?} opt_text Optional inner text.
+ * @return {!Element} The newly created element.
+ * @private
+ */
+BlockDefinitionExtractor.newDomElement_ = function(name, opt_attrs, opt_text) {
+  // Avoid createDom(..)'s attributes argument for being too HTML specific.
+  var elem = goog.dom.createDom(name);
+  if (opt_attrs) {
+    for (var key in opt_attrs) {
+      elem.setAttribute(key, opt_attrs[key]);
+    }
+  }
+  if (opt_text) {
+    elem.append(opt_text);
+  }
+  return elem;
+};
+
+/**
+ * Creates an connection type constraint <block> Element representing the
+ * requested type.
+ *
+ * @param {string} type Type name of desired connection constraint.
+ * @return {!Element} The <block> representing the the constraint type.
+ * @private
+ */
+BlockDefinitionExtractor.buildBlockForType_ = function(type) {
+  switch (type) {
+    case 'Null':
+      return BlockDefinitionExtractor.typeNull_();
+    case 'Boolean':
+      return BlockDefinitionExtractor.typeBoolean_();
+    case 'Number':
+      return BlockDefinitionExtractor.typeNumber_();
+    case 'String':
+      return BlockDefinitionExtractor.typeString_();
+    case 'Array':
+      return BlockDefinitionExtractor.typeList_();
+    default:
+      return BlockDefinitionExtractor.typeOther_(type);
+  }
+};
+
+/**
+ * Constructs a <block> element representing the type constraints of the
+ * provided connection.
+ *
+ * @param {!Blockly.Connection} connection The connection with desired
+ *     connection constraints.
+ * @return {!Element} The root <block> element of the constraint definition.
+ * @private
+ */
+BlockDefinitionExtractor.buildTypeConstraintBlockForConnection_ =
+    function(connection)
+{
+  var typeBlock;
+  if (connection.check_) {
+    if (connection.check_.length < 1) {
+      typeBlock = BlockDefinitionExtractor.typeNullShadow_();
+    } else if (connection.check_.length === 1) {
+      typeBlock = BlockDefinitionExtractor.buildBlockForType_(
+          connection.check_[0]);
+    } else if (connection.check_.length > 1 ) {
+      typeBlock = BlockDefinitionExtractor.typeGroup_(connection.check_);
+    }
+  } else {
+    typeBlock = BlockDefinitionExtractor.typeNullShadow_();
+  }
+  return typeBlock;
+};
+
+/**
+ * Creates the root "factory_base" <block> element for the block definition.
+ *
+ * @param {!Blockly.Block} block The example block from which to extract the
+ *     definition.
+ * @param {string} name Block name.
+ * @return {!Element} The factory_base block element.
+ * @private
+ */
+BlockDefinitionExtractor.factoryBase_ = function(block, name) {
+  BlockDefinitionExtractor.src = {root: block, current: block};
+  var factoryBaseEl =
+      BlockDefinitionExtractor.newDomElement_('block', {type: 'factory_base'});
+  factoryBaseEl.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'NAME'}, name));
+  factoryBaseEl.append(BlockDefinitionExtractor.buildInlineField_(block));
+
+  BlockDefinitionExtractor.buildConnections_(block, factoryBaseEl);
+
+  var inputsStatement = BlockDefinitionExtractor.newDomElement_(
+      'statement', {name: 'INPUTS'});
+  inputsStatement.append(BlockDefinitionExtractor.parseInputs_(block));
+  factoryBaseEl.append(inputsStatement);
+
+  var tooltipValue =
+      BlockDefinitionExtractor.newDomElement_('value', {name: 'TOOLTIP'});
+  tooltipValue.append(BlockDefinitionExtractor.text_(block.tooltip));
+  factoryBaseEl.append(tooltipValue);
+
+  var helpUrlValue =
+      BlockDefinitionExtractor.newDomElement_('value', {name: 'HELPURL'});
+  helpUrlValue.append(BlockDefinitionExtractor.text_(block.helpUrl));
+  factoryBaseEl.append(helpUrlValue);
+
+  // Convert colour_ to hue value 0-360 degrees
+  // TODO(#1247): Solve off-by-one errors.
+  // TODO: Deal with colors that don't map to standard hues. (Needs improved
+  //     block definitions.)
+  var colour_hue = Math.floor(
+      goog.color.hexToHsv(block.colour_)[0]);  // Off by one... sometimes
+  var colourBlock = BlockDefinitionExtractor.colourBlockFromHue_(colour_hue);
+  var colourInputValue =
+      BlockDefinitionExtractor.newDomElement_('value', {name: 'COLOUR'});
+  colourInputValue.append(colourBlock);
+  factoryBaseEl.append(colourInputValue);
+  return factoryBaseEl;
+};
+
+/**
+ * Generates the appropriate <field> element for the block definition's
+ * CONNECTIONS field, which determines the next, previous, and output
+ * connections.
+ *
+ * @param {!Blockly.Block} block The example block from which to extract the
+ *     definition.
+ * @param {!Element} factoryBaseEl The root of the block definition.
+ * @private
+ */
+BlockDefinitionExtractor.buildConnections_ = function(block, factoryBaseEl) {
+  var connections = 'NONE';
+  if (block.outputConnection) {
+    connections = 'LEFT';
+  } else {
+    if (block.previousConnection) {
+      if (block.nextConnection) {
+        connections = 'BOTH';
+      } else {
+        connections = 'TOP';
+      }
+    } else if (block.nextConnection) {
+      connections = 'BOTTOM';
+    }
+  }
+  factoryBaseEl.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'CONNECTIONS'}, connections));
+
+  if (connections === 'LEFT') {
+    var inputValue =
+        BlockDefinitionExtractor.newDomElement_('value', {name: 'OUTPUTTYPE'});
+    inputValue.append(
+        BlockDefinitionExtractor.buildTypeConstraintBlockForConnection_(
+            block.outputConnection));
+    factoryBaseEl.append(inputValue);
+  } else {
+    if (connections === 'UP' || connections === 'BOTH') {
+      var inputValue =
+          BlockDefinitionExtractor.newDomElement_('value', {name: 'TOPTYPE'});
+      inputValue.append(
+          BlockDefinitionExtractor.buildTypeConstraintBlockForConnection_(
+              block.previousConnection));
+      factoryBaseEl.append(inputValue);
+    }
+    if (connections === 'DOWN' || connections === 'BOTH') {
+      var inputValue = BlockDefinitionExtractor.newDomElement_(
+          'value', {name: 'BOTTOMTYPE'});
+      inputValue.append(
+          BlockDefinitionExtractor.buildTypeConstraintBlockForConnection_(
+              block.nextConnection));
+      factoryBaseEl.append(inputValue);
+    }
+  }
+};
+
+/**
+ * Generates the appropriate <field> element for the block definition's INLINE
+ * field.
+ *
+ * @param {!Blockly.Block} block The example block from which to extract the
+ *     definition.
+ * @return {Element} The INLINE <field> with value 'AUTO', 'INT' (internal) or
+ *     'EXT' (external).
+ * @private
+ */
+BlockDefinitionExtractor.buildInlineField_ = function(block) {
+  var inline = 'AUTO'; // When block.inputsInlineDefault === undefined
+  if (block.inputsInlineDefault === true) {
+    inline = 'INT';
+  } else if (block.inputsInlineDefault === false) {
+    inline = 'EXT';
+  }
+  return BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'INLINE'}, inline);
+};
+
+/**
+ * Constructs a sequence of <block> elements that represent the inputs of the
+ * provided block.
+ *
+ * @param {!Blockly.Block} block The source block to copy the inputs of.
+ * @return {Element} The fist <block> element of the sequence
+ *     (and the root of the constructed DOM).
+ * @private
+ */
+BlockDefinitionExtractor.parseInputs_ = function(block) {
+  var firstInputDefElement = null;
+  var lastInputDefElement = null;
+  for (var i = 0; i < block.inputList.length; i++) {
+    var input = block.inputList[i];
+    var align = 'LEFT'; // Left alignment is the default.
+    if (input.align === Blockly.ALIGN_CENTRE) {
+      align = 'CENTRE';
+    } else if (input.align === Blockly.ALIGN_RIGHT) {
+      align = 'RIGHT';
+    }
+
+    var inputDefElement = BlockDefinitionExtractor.input_(input, align);
+    if (lastInputDefElement) {
+      var next = BlockDefinitionExtractor.newDomElement_('next');
+      next.append(inputDefElement);
+      lastInputDefElement.append(next);
+    } else {
+      firstInputDefElement = inputDefElement;
+    }
+    lastInputDefElement = inputDefElement;
+  }
+  return firstInputDefElement;
+};
+
+/**
+ * Creates a <block> element representing a block input.
+ *
+ * @param {!Blockly.Input} input The input object.
+ * @param {string} align Can be left, right or centre.
+ * @return {!Element} The <block> element that defines the input.
+ * @private
+ */
+BlockDefinitionExtractor.input_ = function(input, align) {
+  var isDummy = (input.type === Blockly.DUMMY_INPUT);
+  var inputTypeAttr =
+      isDummy ? 'input_dummy' :
+      (input.type === Blockly.INPUT_VALUE) ? 'input_value' : 'input_statement';
+  var inputDefBlock =
+      BlockDefinitionExtractor.newDomElement_('block', {type: inputTypeAttr});
+
+  if (!isDummy) {
+    inputDefBlock.append(BlockDefinitionExtractor.newDomElement_(
+        'field', {name: 'INPUTNAME'}, input.name));
+  }
+  inputDefBlock.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'ALIGN'}, align));
+
+  var fieldsDef = BlockDefinitionExtractor.newDomElement_(
+      'statement', {name: 'FIELDS'});
+  var fieldsXml = BlockDefinitionExtractor.buildFields_(input.fieldRow);
+  fieldsDef.append(fieldsXml);
+  inputDefBlock.append(fieldsDef);
+
+  if (!isDummy) {
+    var typeValue = BlockDefinitionExtractor.newDomElement_(
+        'value', {name: 'TYPE'});
+    typeValue.append(
+        BlockDefinitionExtractor.buildTypeConstraintBlockForConnection_(
+            input.connection));
+    inputDefBlock.append(typeValue);
+  }
+
+  return inputDefBlock;
+};
+
+/**
+ * Constructs a sequence <block> elements representing the field definition.
+ * @param {Array<Blockly.Field>} fieldRow A list of fields in a Blockly.Input.
+ * @return {Element} The fist <block> element of the sequence
+ *     (and the root of the constructed DOM).
+ * @private
+ */
+BlockDefinitionExtractor.buildFields_ = function(fieldRow) {
+  var firstFieldDefElement = null;
+  var lastFieldDefElement = null;
+
+  for (var i = 0; i < fieldRow.length; i++) {
+    var field = fieldRow[i];
+    var fieldDefElement = BlockDefinitionExtractor.buildFieldElement_(field);
+
+    if (lastFieldDefElement) {
+      var next = BlockDefinitionExtractor.newDomElement_('next');
+      next.append(fieldDefElement);
+      lastFieldDefElement.append(next);
+    } else {
+      firstFieldDefElement = fieldDefElement;
+    }
+    lastFieldDefElement = fieldDefElement;
+  }
+
+  return firstFieldDefElement;
+};
+
+/**
+ * Constructs a <field> element that describes the provided Blockly.Field.
+ * @param {!Blockly.Field} field The field from which the definition is copied.
+ * @param {!Element} A <field> for the Field definition.
+ * @private
+ */
+BlockDefinitionExtractor.buildFieldElement_ = function(field) {
+  if (field instanceof Blockly.FieldLabel) {
+    return BlockDefinitionExtractor.buildFieldLabel_(field.text_);
+  } else if (field instanceof Blockly.FieldTextInput) {
+     return BlockDefinitionExtractor.buildFieldInput_(field.name, field.text_);
+  } else if (field instanceof Blockly.FieldNumber) {
+    return BlockDefinitionExtractor.buildFieldNumber_(
+        field.name, field.text_, field.min_, field.max_, field.presicion_);
+  } else if (field instanceof Blockly.FieldAngle) {
+    return BlockDefinitionExtractor.buildFieldAngle_(field.name, field.text_);
+  } else if (field instanceof Blockly.FieldCheckbox) {
+    return BlockDefinitionExtractor.buildFieldCheckbox_(field.name, field.state_);
+  } else if (field instanceof Blockly.FieldColour) {
+    return BlockDefinitionExtractor.buildFieldColour_(field.name, field.colour_);
+  } else if (field instanceof Blockly.FieldImage) {
+    return BlockDefinitionExtractor.buildFieldImage_(
+        field.src_, field.width_, field.height_, field.text_);
+  } else if (field instanceof Blockly.FieldVariable) {
+    // FieldVariable must be before FieldDropdown, because FieldVariable is a
+    // subclass.
+    return BlockDefinitionExtractor.buildFieldVariable_(field.name, field.text_);
+  } else if (field instanceof Blockly.FieldDropdown) {
+    return BlockDefinitionExtractor.buildFieldDropdown_(field);
+  }
+  throw Error('Unrecognized field class: ' + field.constructor.name);
+};
+
+
+/**
+ * Creates a <block> element representing a FieldLabel definition.
+ * @param {string} text
+ * @return {Element} The XML for FieldLabel definition.
+ * @private
+ */
+BlockDefinitionExtractor.buildFieldLabel_ = function(text) {
+  var fieldBlock =
+      BlockDefinitionExtractor.newDomElement_('block', {type: 'field_static'});
+  fieldBlock.append(
+      BlockDefinitionExtractor.newDomElement_('field', {name: 'TEXT'}, text));
+  return fieldBlock;
+};
+
+/**
+ * Creates a <block> element representing a FieldInput (text input) definition.
+ *
+ * @param {string} fieldName The identifying name of the field.
+ * @param {string} text The default text string.
+ * @return {Element} The XML for FieldInput definition.
+ * @private
+ */
+BlockDefinitionExtractor.buildFieldInput_ = function(fieldName, text) {
+  var fieldInput =
+      BlockDefinitionExtractor.newDomElement_('block', {type: 'field_input'});
+  fieldInput.append(
+      BlockDefinitionExtractor.newDomElement_('field', {name: 'TEXT'}, text));
+  fieldInput.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'FIELDNAME'}, fieldName));
+  return fieldInput;
+};
+
+/**
+ * Creates a <block> element representing a FieldNumber definition.
+ *
+ * @param {string} fieldName The identifying name of the field.
+ * @param {number} value The field's default value.
+ * @param {number} min The minimum allowed value, or negative infinity.
+ * @param {number} max The maximum allowed value, or positive infinity.
+ * @param {number} precision The precision allowed for the number.
+ * @return {Element} The XML for FieldNumber definition.
+ * @private
+ */
+BlockDefinitionExtractor.buildFieldNumber_ =
+  function(fieldName, value, min, max, precision)
+{
+  var fieldNumber =
+      BlockDefinitionExtractor.newDomElement_('block', {type: 'field_number'});
+  fieldNumber.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'VALUE'}, value));
+  fieldNumber.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'FIELDNAME'}, fieldName));
+  fieldNumber.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'MIN'}, min));
+  fieldNumber.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'MAX'}, max));
+  fieldNumber.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'PRECISION'}, precision));
+  return fieldNumber;
+};
+
+/**
+ * Creates a <block> element representing a FieldAngle definition.
+ *
+ * @param {string} fieldName The identifying name of the field.
+ * @param {number} angle The field's default value.
+ * @return {Element} The XML for FieldAngle definition.
+ * @private
+ */
+BlockDefinitionExtractor.buildFieldAngle_ = function(angle, fieldName) {
+  var fieldAngle =
+      BlockDefinitionExtractor.newDomElement_('block', {type: 'field_angle'});
+  fieldAngle.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'ANGLE'}, angle));
+  fieldAngle.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'FIELDNAME'}, fieldName));
+  return fieldAngle;
+};
+
+/**
+ * Creates a <block> element representing a FieldDropdown definition.
+ *
+ * @param {Blockly.FieldDropdown} dropdown
+ * @return {Element} The <block> element representing a similar FieldDropdown.
+ * @private
+ */
+BlockDefinitionExtractor.buildFieldDropdown_ = function(dropdown) {
+  var menuGenerator = dropdown.menuGenerator_;
+  if (typeof menuGenerator === 'function') {
+    var options = menuGenerator();
+  } else if (goog.isArray(menuGenerator)) {
+    var options = menuGenerator;
+  } else {
+    throw new Error('Unrecognized type of menuGenerator: ' + menuGenerator);
+  }
+
+  var fieldDropdown = BlockDefinitionExtractor.newDomElement_(
+      'block', {type: 'field_dropdown'});
+  var optionsStr = '[';
+
+  var mutation = BlockDefinitionExtractor.newDomElement_('mutation');
+  fieldDropdown.append(mutation);
+  fieldDropdown.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'FIELDNAME'}, dropdown.name));
+  for (var i=0; i<options.length; i++) {
+    var option = options[i];
+    if (typeof option[0] === "string") {
+      optionsStr += '"text",'
+      fieldDropdown.append(BlockDefinitionExtractor.newDomElement_(
+          'field', {name: 'USER'+i}, option[0]));
+    } else {
+      optionsStr += '"image",';
+      fieldDropdown.append(
+          BlockDefinitionExtractor.newDomElement_(
+          'field', {name: 'SRC'+i}, option[0].src));
+      fieldDropdown.append(BlockDefinitionExtractor.newDomElement_(
+          'field', {name: 'WIDTH'+i}, option[0].width));
+      fieldDropdown.append(BlockDefinitionExtractor.newDomElement_(
+          'field', {name: 'HEIGHT'+i}, option[0].height));
+      fieldDropdown.append(BlockDefinitionExtractor.newDomElement_(
+          'field', {name: 'ALT'+i}, option[0].alt));
+    }
+    fieldDropdown.append(BlockDefinitionExtractor.newDomElement_(
+        'field', {name: 'CPU'+i}, option[1]));
+  }
+  optionsStr = optionsStr.slice(0,-1); // Drop last comma
+  optionsStr += ']';
+  mutation.setAttribute('options', optionsStr);
+
+  return fieldDropdown;
+};
+
+/**
+ * Creates a <block> element representing a FieldCheckbox definition.
+ *
+ * @param {string} fieldName The identifying name of the field.
+ * @param {string} checked The field's default value, true or false.
+ * @return {Element} The XML for FieldCheckbox definition.
+ * @private
+ */
+BlockDefinitionExtractor.buildFieldCheckbox_ =
+  function(fieldName, checked)
+{
+  var fieldCheckbox = BlockDefinitionExtractor.newDomElement_(
+      'block', {type: 'field_checkbox'});
+  fieldCheckbox.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'CHECKED'}, checked));
+  fieldCheckbox.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'FIELDNAME'}, fieldName));
+  return fieldCheckbox;
+};
+
+/**
+ * Creates a <block> element representing a FieldColour definition.
+ *
+ * @param {string} fieldName The identifying name of the field.
+ * @param {string} colour The field's default value as a string.
+ * @return {Element} The XML for FieldColour definition.
+ * @private
+ */
+BlockDefinitionExtractor.buildFieldColour_ =
+    function(fieldName, colour)
+{
+  var fieldColour = BlockDefinitionExtractor.newDomElement_(
+      'block', {type: 'field_colour'});
+  fieldColour.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'COLOUR'}, colour));
+  fieldColour.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'FIELDNAME'}, fieldName));
+  return fieldColour;
+};
+
+/**
+ * Creates a <block> element representing a FieldVaraible definition.
+ *
+ * @param {string} fieldName The identifying name of the field.
+ * @param {string} varName The variables
+ * @return {Element} The <block> element representing the FieldVariable.
+ * @private
+ */
+BlockDefinitionExtractor.buildFieldVariable_ = function(fieldName, varName) {
+  var fieldVar = BlockDefinitionExtractor.newDomElement_(
+      'block', {type: 'field_variable'});
+  fieldVar.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'FIELDNAME'}, fieldName));
+  fieldVar.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'TEXT'}, varName));
+  return fieldVar;
+};
+
+/**
+ * Creates a <block> element representing a FieldImage definition.
+ *
+ * @param {string} src The URL of the field image.
+ * @param {number} width The pixel width of the source image
+ * @param {number} height The pixel height of the source image.
+ * @param {string} alt Alterante text to describe image.
+ * @private
+ */
+BlockDefinitionExtractor.buildFieldImage_ =
+  function(src, width, height, alt)
+{
+  var block1 = BlockDefinitionExtractor.newDomElement_(
+      'block', {type: 'field_image'});
+  block1.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'SRC'}, src));
+  block1.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'WIDTH'}, width));
+  block1.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'HEIGHT'}, height));
+  block1.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'ALT'}, alt));
+};
+
+/**
+ * Creates a <block> element a group of allowed connection constraint types.
+ *
+ * @param {Array<string>} types List of type names in this group.
+ * @return {Element} The <block> element representing the group, with child
+ *     types attached.
+ * @private
+ */
+BlockDefinitionExtractor.typeGroup_ = function(types) {
+  var typeGroupBlock = BlockDefinitionExtractor.newDomElement_(
+      'block', {type: 'type_group'});
+  typeGroupBlock.append(BlockDefinitionExtractor.newDomElement_(
+      'mutation', {types:types.length}));
+  for (var i=0; i<types.length; i++) {
+    var typeBlock = BlockDefinitionExtractor.buildBlockForType_(types[i]);
+    var valueBlock = BlockDefinitionExtractor.newDomElement_(
+        'value', {name:'TYPE'+i});
+    valueBlock.append(typeBlock);
+    typeGroupBlock.append(valueBlock);
+  }
+  return typeGroupBlock;
+};
+
+/**
+ * Creates a <shadow> block element representing the default null connection
+ * constraint.
+ * @return {Element} The <block> element representing the "null" type
+ *     constraint.
+ * @private
+ */
+BlockDefinitionExtractor.typeNullShadow_ = function() {
+  return BlockDefinitionExtractor.newDomElement_(
+      'shadow', {type: 'type_null'});
+};
+
+/**
+ * Creates a <block> element representing null in a connection constraint.
+ * @return {Element} The <block> element representing the "null" type
+ *     constraint.
+ * @private
+ */
+BlockDefinitionExtractor.typeNull_ = function() {
+  return BlockDefinitionExtractor.newDomElement_('block', {type: 'type_null'});
+};
+
+/**
+ * Creates a <block> element representing the a boolean in a connection
+ * constraint.
+ * @return {Element} The <block> element representing the "boolean" type
+ *     constraint.
+ * @private
+ */
+BlockDefinitionExtractor.typeBoolean_ = function() {
+  return BlockDefinitionExtractor.newDomElement_(
+      'block', {type: 'type_boolean'});
+};
+
+/**
+ * Creates a <block> element representing the a number in a connection
+ * constraint.
+ * @return {Element} The <block> element representing the "number" type
+ *     constraint.
+ * @private
+ */
+BlockDefinitionExtractor.typeNumber_ = function() {
+  return BlockDefinitionExtractor.newDomElement_(
+      'block', {type: 'type_number'});
+};
+
+/**
+ * Creates a <block> element representing the a string in a connection
+ * constraint.
+ * @return {Element} The <block> element representing the "string" type
+ *     constraint.
+ * @private
+ */
+BlockDefinitionExtractor.typeString_ = function() {
+  return BlockDefinitionExtractor.newDomElement_(
+      'block', {type: 'type_string'});
+};
+
+/**
+ * Creates a <block> element representing the a list in a connection
+ * constraint.
+ * @return {Element} The <block> element representing the "list" type
+ *     constraint.
+ * @private
+ */
+BlockDefinitionExtractor.typeList_ = function() {
+  return BlockDefinitionExtractor.newDomElement_('block', {type: 'type_list'});
+};
+
+/**
+ * Creates a <block> element representing the given custom connection
+ * constraint type name.
+ *
+ * @param {string} type The connection constratin type name.
+ * @return {Element} The <block> element representing a custom input type
+ *     constraint.
+ * @private
+ */
+BlockDefinitionExtractor.typeOther_ = function(type) {
+  var block = BlockDefinitionExtractor.newDomElement_(
+      'block', {type: 'type_other'});
+  block.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'TYPE'}, type));
+  return block;
+};
+
+/**
+ * Creates a block Element for the color_hue block, with the given hue.
+ * @param hue {number} The hue value, from 0 to 360.
+ * @return {Element} The <block> Element representing a colour_hue block
+ *     with the given hue.
+ * @private
+ */
+BlockDefinitionExtractor.colourBlockFromHue_ = function(hue) {
+  var colourBlock = BlockDefinitionExtractor.newDomElement_(
+      'block', {type: 'colour_hue'});
+  colourBlock.append(BlockDefinitionExtractor.newDomElement_('mutation', {
+    colour: Blockly.hueToRgb(hue)
+  }));
+  colourBlock.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'HUE'}, hue.toString()));
+  return colourBlock;
+};
+
+/**
+ * Creates a block Element for a text block with the given text.
+ *
+ * @param text {string} The text value of the block.
+ * @return {Element} The <block> element representing a "text" block.
+ * @private
+ */
+BlockDefinitionExtractor.text_ = function(text) {
+  var textBlock =
+      BlockDefinitionExtractor.newDomElement_('block', {type: 'text'});
+  if (text) {
+    textBlock.append(BlockDefinitionExtractor.newDomElement_(
+      'field', {name: 'TEXT'}, text));
+  } // Else, use empty string default.
+  return textBlock;
+};
diff --git a/demos/blockfactory/factory.js b/demos/blockfactory/factory.js
index 974cd8a7e..821984b52 100644
--- a/demos/blockfactory/factory.js
+++ b/demos/blockfactory/factory.js
@@ -37,7 +37,6 @@ goog.provide('BlockFactory');
 goog.require('FactoryUtils');
 goog.require('StandardCategories');
 
-
 /**
  * Workspace for user to build block.
  * @type {Blockly.Workspace}
@@ -52,14 +51,32 @@ BlockFactory.previewWorkspace = null;
 
 /**
  * Name of block if not named.
+ * @type string
  */
 BlockFactory.UNNAMED = 'unnamed';
 
 /**
  * Existing direction ('ltr' vs 'rtl') of preview.
+ * @type string
  */
 BlockFactory.oldDir = null;
 
+/**
+ * Flag to signal that an update came from a manual update to the JSON or JavaScript.
+ * definition manually.
+ * @type boolean
+ */
+// TODO: Replace global state with parameter passed to functions.
+BlockFactory.updateBlocksFlag = false;
+
+/**
+ * Delayed flag to avoid infinite update after updating the JSON or JavaScript.
+ * definition manually.
+ * @type boolean
+ */
+// TODO: Replace global state with parameter passed to functions.
+BlockFactory.updateBlocksFlagDelayed = false;
+
 /*
  * The starting XML for the Block Factory main workspace. Contains the
  * unmovable, undeletable factory_base block.
@@ -85,7 +102,8 @@ BlockFactory.formatChange = function() {
   var mask = document.getElementById('blocklyMask');
   var languagePre = document.getElementById('languagePre');
   var languageTA = document.getElementById('languageTA');
-  if (document.getElementById('format').value == 'Manual') {
+  if (document.getElementById('format').value == 'Manual-JSON' ||
+      document.getElementById('format').value == 'Manual-JS') {
     Blockly.hideChaff();
     mask.style.display = 'block';
     languagePre.style.display = 'none';
@@ -98,6 +116,9 @@ BlockFactory.formatChange = function() {
     mask.style.display = 'none';
     languageTA.style.display = 'none';
     languagePre.style.display = 'block';
+    var code = languagePre.textContent.trim();
+    languageTA.value = code;
+
     BlockFactory.updateLanguage();
   }
   BlockFactory.disableEnableLink();
@@ -115,10 +136,26 @@ BlockFactory.updateLanguage = function() {
   if (!blockType) {
     blockType = BlockFactory.UNNAMED;
   }
-  var format = document.getElementById('format').value;
-  var code = FactoryUtils.getBlockDefinition(blockType, rootBlock, format,
-      BlockFactory.mainWorkspace);
-  FactoryUtils.injectCode(code, 'languagePre');
+
+  if (!BlockFactory.updateBlocksFlag) {
+    var format = document.getElementById('format').value;
+    if (format == 'Manual-JSON') {
+      format = 'JSON';
+    } else if (format == 'Manual-JS') {
+      format = 'JavaScript';
+    }
+
+    var code = FactoryUtils.getBlockDefinition(blockType, rootBlock, format,
+        BlockFactory.mainWorkspace);
+    FactoryUtils.injectCode(code, 'languagePre');
+    if (!BlockFactory.updateBlocksFlagDelayed) {
+      var languagePre = document.getElementById('languagePre');
+      var languageTA = document.getElementById('languageTA');
+      code = languagePre.textContent.trim();
+      languageTA.value = code;
+    }
+  }
+
   BlockFactory.updatePreview();
 };
 
@@ -151,20 +188,8 @@ BlockFactory.updatePreview = function() {
   }
   BlockFactory.previewWorkspace.clear();
 
-  // Fetch the code and determine its format (JSON or JavaScript).
-  var format = document.getElementById('format').value;
-  if (format == 'Manual') {
-    var code = document.getElementById('languageTA').value;
-    // If the code is JSON, it will parse, otherwise treat as JS.
-    try {
-      JSON.parse(code);
-      format = 'JSON';
-    } catch (e) {
-      format = 'JavaScript';
-    }
-  } else {
-    var code = document.getElementById('languagePre').textContent;
-  }
+  var format = BlockFactory.getBlockDefinitionFormat();
+  var code = document.getElementById('languageTA').value;
   if (!code.trim()) {
     // Nothing to render.  Happens while cloud storage is loading.
     return;
@@ -188,9 +213,13 @@ BlockFactory.updatePreview = function() {
         }
       };
     } else if (format == 'JavaScript') {
-      eval(code);
-    } else {
-      throw 'Unknown format: ' + format;
+      try {
+        eval(code);
+      } catch (e) {
+        // TODO: Display error in the UI
+        console.error("Error while evaluating JavaScript formatted block definition", e);
+        return;
+      }
     }
 
     // Look for a block on Blockly.Blocks that does not match the backup.
@@ -232,12 +261,36 @@ BlockFactory.updatePreview = function() {
     } else {
       rootBlock.setWarningText(null);
     }
-
+  } catch(err) {
+    // TODO: Show error on the UI
+    console.log(err);
+    BlockFactory.updateBlocksFlag = false
+    BlockFactory.updateBlocksFlagDelayed = false
   } finally {
     Blockly.Blocks = backupBlocks;
   }
 };
 
+/**
+ * Gets the format from the Block Definitions' format selector/drop-down.
+ * @return Either 'JavaScript' or 'JSON'.
+ * @throws If selector value is not recognized.
+ */
+BlockFactory.getBlockDefinitionFormat = function() {
+  switch (document.getElementById('format').value) {
+    case 'JSON':
+    case 'Manual-JSON':
+      return 'JSON';
+
+    case 'JavaScript':
+    case 'Manual-JS':
+      return 'JavaScript';
+
+    default:
+      throw 'Unknown format: ' + format;
+  }
+}
+
 /**
  * Disable link and save buttons if the format is 'Manual', enable otherwise.
  */
@@ -245,7 +298,7 @@ BlockFactory.disableEnableLink = function() {
   var linkButton = document.getElementById('linkButton');
   var saveBlockButton = document.getElementById('localSaveButton');
   var saveToLibButton = document.getElementById('saveToBlockLibraryButton');
-  var disabled = document.getElementById('format').value == 'Manual';
+  var disabled = document.getElementById('format').value.substr(0, 6) == 'Manual';
   linkButton.disabled = disabled;
   saveBlockButton.disabled = disabled;
   saveToLibButton.disabled = disabled;
@@ -265,12 +318,25 @@ BlockFactory.showStarterBlock = function() {
  */
 BlockFactory.isStarterBlock = function() {
   var rootBlock = FactoryUtils.getRootBlock(BlockFactory.mainWorkspace);
-  // The starter block does not have blocks nested into the factory_base block.
-  return !(rootBlock.getChildren().length > 0 ||
+  return rootBlock && !(
+      // The starter block does not have blocks nested into the factory_base block.
+      rootBlock.getChildren().length > 0 ||
       // The starter block's name is the default, 'block_type'.
       rootBlock.getFieldValue('NAME').trim().toLowerCase() != 'block_type' ||
       // The starter block has no connections.
       rootBlock.getFieldValue('CONNECTIONS') != 'NONE' ||
       // The starter block has automatic inputs.
-      rootBlock.getFieldValue('INLINE') != 'AUTO');
+      rootBlock.getFieldValue('INLINE') != 'AUTO'
+      );
 };
+
+/**
+ * Updates blocks from the manually edited js or json from their text area.
+ */
+BlockFactory.manualEdit = function() {
+  // TODO(#1267): Replace these global state flags with parameters passed to
+  //              the right functions.
+  BlockFactory.updateBlocksFlag = true;
+  BlockFactory.updateBlocksFlagDelayed = true;
+  BlockFactory.updateLanguage();
+}
diff --git a/demos/blockfactory/factory_utils.js b/demos/blockfactory/factory_utils.js
index d66225c3a..63f9864eb 100644
--- a/demos/blockfactory/factory_utils.js
+++ b/demos/blockfactory/factory_utils.js
@@ -24,15 +24,18 @@
  * Exporter applications within Blockly Factory. Holds functions to generate
  * block definitions and generator stubs and to create and download files.
  *
- * @author fraser@google.com (Neil Fraser), quachtina96 (Tina Quach)
+ * @author fraser@google.com (Neil Fraser), quachtina96 (Tina Quach), JC-Orozco
+ * (Juan Carlos Orozco)
  */
- 'use strict';
+'use strict';
 
 /**
  * Namespace for FactoryUtils.
  */
 goog.provide('FactoryUtils');
 
+goog.require('BlockDefinitionExtractor');
+
 
 /**
  * Get block definition code for the current block.
@@ -73,10 +76,23 @@ FactoryUtils.cleanBlockType = function(blockType) {
  * Get the generator code for a given block.
  * @param {!Blockly.Block} block Rendered block in preview workspace.
  * @param {string} generatorLanguage 'JavaScript', 'Python', 'PHP', 'Lua',
- *   'Dart'.
+ *     or 'Dart'.
  * @return {string} Generator code for multiple blocks.
  */
 FactoryUtils.getGeneratorStub = function(block, generatorLanguage) {
+  // Build factory blocks from block
+  if (BlockFactory.updateBlocksFlag) {  // TODO: Move this to updatePreview()
+    BlockFactory.mainWorkspace.clear();
+    var xml = BlockDefinitionExtractor.buildBlockFactoryWorkspace(block);
+    Blockly.Xml.domToWorkspace(xml, BlockFactory.mainWorkspace);
+    // Calculate timer to avoid infinite update loops
+    // TODO(#1267): Remove the global variables and any infinite loops.
+    BlockFactory.updateBlocksFlag = false;
+    setTimeout(
+        function() {BlockFactory.updateBlocksFlagDelayed = false;}, 3000);
+  }
+  BlockFactory.lastUpdatedBlock = block; // Variable to share the block value.
+
   function makeVar(root, name) {
     name = name.toLowerCase().replace(/\W/g, '_');
     return '  var ' + root + '_' + name;
diff --git a/demos/blockfactory/index.html b/demos/blockfactory/index.html
index 9190bd132..ccfc05654 100644
--- a/demos/blockfactory/index.html
+++ b/demos/blockfactory/index.html
@@ -10,6 +10,7 @@
   <script src="../../blocks_compressed.js"></script>
   <script src="../../../closure-library/closure/goog/base.js"></script>
   <script src="analytics.js"></script>
+  <script src="block_definition_extractor.js"></script>
   <script src="factory_utils.js"></script>
   <script src="workspacefactory/wfactory_model.js"></script>
   <script src="standard_categories.js"></script>
@@ -354,10 +355,21 @@
           <tr>
             <td height="5%">
               <h3>Block Definition:
+                <!-- TODO(#1268): Separate concerns of format and editable.
+                  -               Add "Editable" state toggle button? -->
                 <select id="format">
                   <option value="JSON">JSON</option>
                   <option value="JavaScript">JavaScript</option>
-                  <option value="Manual">Manual edit&hellip;</option>
+                  <option value="Manual-JSON">Manual JSON&hellip;</option>
+                  <script>
+                    // Manual JavaScript works but requires use of eval().
+                    // TODO(#1269): Replace eval() with JS-Interpreter before
+                    //              re-enabling "Manual JavaScript" mode.
+                    if (document.location.href.indexOf('file://') == 0) {
+                      document.write(
+                          '<option value="Manual-JS">Manual JavaScript&hellip;</option>');
+                    }
+                  </script>
                 </select>
               </h3>
             </td>