tools/dom/src/native_DOMImplementation.dart - sdk.git - Git at Google

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 part of html;

 class _ConsoleVariables {
   Map<String, Object> _data = new Map<String, Object>();

   /**
    * Forward member accesses to the backing JavaScript object.
    */
   noSuchMethod(Invocation invocation) {
     String member = MirrorSystem.getName(invocation.memberName);
     if (invocation.isGetter) {
       return _data[member];
     } else if (invocation.isSetter) {
       assert(member.endsWith('='));
       member = member.substring(0, member.length - 1);
       _data[member] = invocation.positionalArguments[0];
     } else {
       return Function.apply(_data[member], invocation.positionalArguments, invocation.namedArguments);
     }
   }

   void clear() => _data.clear();

   /**
    * List all variables currently defined.
    */
   List variables() => _data.keys.toList(growable: false);
 }

 class _Utils {
   static double dateTimeToDouble(DateTime dateTime) =>
       dateTime.millisecondsSinceEpoch.toDouble();
   static DateTime doubleToDateTime(double dateTime) {
     try {
       return new DateTime.fromMillisecondsSinceEpoch(dateTime.toInt());
     } catch(_) {
       // TODO(antonnm): treat exceptions properly in bindings and
       // find out how to treat NaNs.
       return null;
     }
   }

   static List convertToList(List list) {
     // FIXME: [possible optimization]: do not copy the array if Dart_IsArray is fine w/ it.
     final length = list.length;
     List result = new List(length);
     result.setRange(0, length, list);
     return result;
   }

   static List convertMapToList(Map map) {
     List result = [];
     map.forEach((k, v) => result.addAll([k, v]));
     return result;
   }

   static int convertCanvasElementGetContextMap(Map map) {
     int result = 0;
     if (map['alpha'] == true) result |= 0x01;
     if (map['depth'] == true) result |= 0x02;
     if (map['stencil'] == true) result |= 0x4;
     if (map['antialias'] == true) result |= 0x08;
     if (map['premultipliedAlpha'] == true) result |= 0x10;
     if (map['preserveDrawingBuffer'] == true) result |= 0x20;

     return result;
   }

   static List parseStackTrace(StackTrace stackTrace) {
     final regExp = new RegExp(r'#\d\s+(.*) \((.*):(\d+):(\d+)\)');
     List result = [];
     for (var match in regExp.allMatches(stackTrace.toString())) {
       result.add([match.group(1), match.group(2), int.parse(match.group(3)), int.parse(match.group(4))]);
     }
     return result;
   }

   static void populateMap(Map result, List list) {
     for (int i = 0; i < list.length; i += 2) {
       result[list[i]] = list[i + 1];
     }
   }

   static bool isMap(obj) => obj is Map;

   static Map createMap() => {};

   static makeUnimplementedError(String fileName, int lineNo) {
     return new UnsupportedError('[info: $fileName:$lineNo]');
   }

   static bool isTypeSubclassOf(Type type, Type other) {
     if (type == other) {
       return true;
     }
     var superclass = reflectClass(type).superclass;
     if (superclass != null) {
       return isTypeSubclassOf(superclass.reflectedType, other);
     }
     return false;
   }

   static window() native "Utils_window";
   static forwardingPrint(String message) native "Utils_forwardingPrint";
   static int _getNewIsolateId() native "Utils_getNewIsolateId";

   // The following methods were added for debugger integration to make working
   // with the Dart C mirrors API simpler.
   // TODO(jacobr): consider moving them to a separate library.
   // If Dart supported dynamic code injection, we would only inject this code
   // when the debugger is invoked.

   /**
    * Strips the private secret prefix from member names of the form
    * someName@hash.
    */
   static String stripMemberName(String name) {
     int endIndex = name.indexOf('@');
     return endIndex > 0 ? name.substring(0, endIndex) : name;
   }

   /**
    * Takes a list containing variable names and corresponding values and
    * returns a map from normalized names to values. Variable names are assumed
    * to have list offsets 2*n values at offset 2*n+1. This method is required
    * because Dart_GetLocalVariables returns a list instead of an object that
    * can be queried to lookup names and values.
    */
   static Map<String, dynamic> createLocalVariablesMap(List localVariables) {
     var map = {};
     for (int i = 0; i < localVariables.length; i+=2) {
       map[stripMemberName(localVariables[i])] = localVariables[i+1];
     }
     return map;
   }

   static _ConsoleVariables _consoleTempVariables = new _ConsoleVariables();

   /**
    * Header passed in from the Dartium Developer Tools when an expression is
    * evaluated in the console as opposed to the watch window or another context
    * that does not expect REPL support.
    */
   static const _CONSOLE_API_SUPPORT_HEADER =
       'with ((this && this.console && this.console._commandLineAPI) || {}) {\n';

   /**
    * Takes an [expression] and a list of [local] variable and returns an
    * expression for a closure with a body matching the original expression
    * where locals are passed in as arguments. Returns a list containing the
    * String expression for the closure and the list of arguments that should
    * be passed to it. The expression should then be evaluated using
    * Dart_EvaluateExpr which will generate a closure that should be invoked
    * with the list of arguments passed to this method.
    *
    * For example:
    * <code>
    * _consoleTempVariables = {'a' : someValue, 'b': someOtherValue}
    * wrapExpressionAsClosure("${_CONSOLE_API_SUPPORT_HEADER}foo + bar + a",
    *                         ["bar", 40, "foo", 2])
    * </code>
    * will return:
    * <code>
    * ["""(final $consoleVariables, final bar, final foo, final a, final b) =>
    * (foo + bar + a
    * )""",
    * [_consoleTempVariables, 40, 2, someValue, someOtherValue]]
    * </code>
    */
   static List wrapExpressionAsClosure(String expression, List locals) {
     // FIXME: dartbug.com/10434 find a less fragile way to determine whether
     // we need to strip off console API support added by InjectedScript.
     var args = {};
     var sb = new StringBuffer("(");
     addArg(arg, value) {
       arg = stripMemberName(arg);
       if (args.containsKey(arg)) return;
       // We ignore arguments with the name 'this' rather than throwing an
       // exception because Dart_GetLocalVariables includes 'this' and it
       // is more convenient to filter it out here than from C++ code.
       // 'this' needs to be handled by calling Dart_EvaluateExpr with
       // 'this' as the target rather than by passing it as an argument.
       if (arg == 'this') return;
       if (args.isNotEmpty) {
         sb.write(", ");
       }
       sb.write("final $arg");
       args[arg] = value;
     }

     if (expression.indexOf(_CONSOLE_API_SUPPORT_HEADER) == 0) {
       expression = expression.substring(expression.indexOf('\n') + 1);
       expression = expression.substring(0, expression.lastIndexOf('\n'));

       addArg("\$consoleVariables", _consoleTempVariables);

       // FIXME: use a real Dart tokenizer. The following regular expressions
       // only allow setting variables at the immediate start of the expression
       // to limit the number of edge cases we have to handle.

       // Match expressions that start with "var x"
       final _VARIABLE_DECLARATION = new RegExp("^(\\s*)var\\s+(\\w+)");
       // Match expressions that start with "someExistingConsoleVar ="
       final _SET_VARIABLE = new RegExp("^(\\s*)(\\w+)(\\s*=)");
       // Match trailing semicolons.
       final _ENDING_SEMICOLONS = new RegExp("(;\\s*)*\$");
       expression = expression.replaceAllMapped(_VARIABLE_DECLARATION,
           (match) {
             var variableName = match[2];
             // Set the console variable if it isn't already set.
             if (!_consoleTempVariables._data.containsKey(variableName)) {
               _consoleTempVariables._data[variableName] = null;
             }
             return "${match[1]}\$consoleVariables.${variableName}";
           });

       expression = expression.replaceAllMapped(_SET_VARIABLE,
           (match) {
             var variableName = match[2];
             // Only rewrite if the name matches an existing console variable.
             if (_consoleTempVariables._data.containsKey(variableName)) {
               return "${match[1]}\$consoleVariables.${variableName}${match[3]}";
             } else {
               return match[0];
             }
           });

       // We only allow dart expressions not Dart statements. Silently remove
       // trailing semicolons the user might have added by accident to reduce the
       // number of spurious compile errors.
       expression = expression.replaceFirst(_ENDING_SEMICOLONS, "");
     }

     if (locals != null) {
       for (int i = 0; i < locals.length; i+= 2) {
         addArg(locals[i], locals[i+1]);
       }
     }
     // Inject all the already defined console variables.
     _consoleTempVariables._data.forEach(addArg);

     // TODO(jacobr): remove the parentheses around the expresson once
     // dartbug.com/13723 is fixed. Currently we wrap expression in parentheses
     // to ensure only valid Dart expressions are allowed. Otherwise the DartVM
     // quietly ignores trailing Dart statements resulting in user confusion
     // when part of an invalid expression they entered is ignored.
     sb..write(') => (\n$expression\n)');
     return [sb.toString(), args.values.toList(growable: false)];
   }

   /**
    * TODO(jacobr): this is a big hack to get around the fact that we are still
    * passing some JS expression to the evaluate method even when in a Dart
    * context.
    */
   static bool isJsExpression(String expression) =>
     expression.startsWith("(function getCompletions");

   /**
    * Returns a list of completions to use if the receiver is o.
    */
   static List<String> getCompletions(o) {
     MirrorSystem system = currentMirrorSystem();
     var completions = new Set<String>();
     addAll(Map<Symbol, dynamic> map, bool isStatic) {
       map.forEach((symbol, mirror) {
         if (mirror.isStatic == isStatic && !mirror.isPrivate) {
           var name = MirrorSystem.getName(symbol);
           if (mirror is MethodMirror && mirror.isSetter)
             name = name.substring(0, name.length - 1);
           completions.add(name);
         }
       });
     }

     addForClass(ClassMirror mirror, bool isStatic) {
       if (mirror == null)
         return;
       addAll(mirror.members, isStatic);
       if (mirror.superclass != null)
         addForClass(mirror.superclass, isStatic);
       for (var interface in mirror.superinterfaces) {
         addForClass(interface, isStatic);
       }
     }

     if (o is Type) {
       addForClass(reflectClass(o), true);
     } else {
       addForClass(reflect(o).type, false);
     }
     return completions.toList(growable: false);
   }

   /**
    * Convenience helper to get the keys of a [Map] as a [List].
    */
   static List getMapKeyList(Map map) => map.keys.toList();

  /**
    * Returns the keys of an arbitrary Dart Map encoded as unique Strings.
    * Keys that are strings are left unchanged except that the prefix ":" is
    * added to disambiguate keys from other Dart members.
    * Keys that are not strings have # followed by the index of the key in the map
    * prepended to disambuguate. This scheme is simplistic but easy to encode and
    * decode. The use case for this method is displaying all map keys in a human
    * readable way in debugging tools.
    */
   static List<String> getEncodedMapKeyList(dynamic obj) {
     if (obj is! Map) return null;

     var ret = new List<String>();
     int i = 0;
     return obj.keys.map((key) {
       var encodedKey;
       if (key is String) {
         encodedKey = ':$key';
       } else {
         // If the key isn't a string, return a guaranteed unique for this map
         // string representation of the key that is still somewhat human
         // readable.
         encodedKey = '#${i}:$key';
       }
       i++;
       return encodedKey;
     }).toList(growable: false);
   }

   static final RegExp _NON_STRING_KEY_REGEXP = new RegExp("^#(\\d+):(.+)\$");

   static _decodeKey(Map map, String key) {
     // The key is a regular old String.
     if (key.startsWith(':')) return key.substring(1);

     var match = _NON_STRING_KEY_REGEXP.firstMatch(key);
     if (match != null) {
       int index = int.parse(match.group(1));
       var iter = map.keys.skip(index);
       if (iter.isNotEmpty) {
         var ret = iter.first;
         // Validate that the toString representation of the key matches what we
         // expect. FIXME: throw an error if it does not.
         assert(match.group(2) == '$ret');
         return ret;
       }
     }
     return null;
   }

   /**
    * Converts keys encoded with [getEncodedMapKeyList] to their actual keys.
    */
   static lookupValueForEncodedMapKey(Map obj, String key) => obj[_decodeKey(obj, key)];

   /**
    * Builds a constructor name with the form expected by the C Dart mirrors API.
    */
   static String buildConstructorName(String className, String constructorName) => '$className.$constructorName';

   /**
    * Strips the class name from an expression of the form "className.someName".
    */
   static String stripClassName(String str, String className) {
     if (str.length > className.length + 1 &&
         str.startsWith(className) && str[className.length] == '.') {
       return str.substring(className.length + 1);
     } else {
       return str;
     }
   }

   /**
    * Removes the trailing dot from an expression ending in a dot.
    * This method is used as Library prefixes include a trailing dot when using
    * the C Dart debugger API.
    */
   static String stripTrailingDot(String str) =>
     (str != null && str[str.length - 1] == '.') ? str.substring(0, str.length - 1) : str;

   static String addTrailingDot(String str) => '${str}.';

   static bool isNoSuchMethodError(obj) => obj is NoSuchMethodError;

   // TODO(jacobr): we need a failsafe way to determine that a Node is really a
   // DOM node rather than just a class that extends Node.
   static bool isNode(obj) => obj is Node;

   static bool _isBuiltinType(ClassMirror cls) {
     // TODO(vsm): Find a less hackish way to do this.
     LibraryMirror lib = cls.owner;
     String libName = lib.uri.toString();
     return libName.startsWith('dart:');
   }

   static void register(Document document, String tag, Type type,
       String extendsTagName) {
     // TODO(vsm): Move these checks into native code.
     ClassMirror cls = reflectClass(type);
     if (_isBuiltinType(cls)) {
       throw new UnsupportedError("Invalid custom element from $libName.");
     }
     var className = MirrorSystem.getName(cls.simpleName);
     if (!cls.constructors.containsKey(new Symbol('$className.created'))) {
       throw new UnsupportedError('Class is missing constructor $className.created');
     }
     _register(document, tag, type, extendsTagName);
   }

   static void _register(Document document, String tag, Type customType,
       String extendsTagName) native "Utils_register";

   static Element createElement(Document document, String tagName) native "Utils_createElement";

   static void initializeCustomElement(HtmlElement element) native "Utils_initializeCustomElement";
 }

 class _DOMWindowCrossFrame extends NativeFieldWrapperClass1 implements
     WindowBase {
   _DOMWindowCrossFrame.internal();

   // Fields.
   HistoryBase get history native "Window_history_cross_frame_Getter";
   LocationBase get location native "Window_location_cross_frame_Getter";
   bool get closed native "Window_closed_Getter";
   int get length native "Window_length_Getter";
   WindowBase get opener native "Window_opener_Getter";
   WindowBase get parent native "Window_parent_Getter";
   WindowBase get top native "Window_top_Getter";

   // Methods.
   void close() native "Window_close_Callback";
   void postMessage(/*SerializedScriptValue*/ message, String targetOrigin, [List messagePorts]) native "Window_postMessage_Callback";

   // Implementation support.
   String get typeName => "Window";
 }

 class _HistoryCrossFrame extends NativeFieldWrapperClass1 implements HistoryBase {
   _HistoryCrossFrame.internal();

   // Methods.
   void back() native "History_back_Callback";
   void forward() native "History_forward_Callback";
   void go(int distance) native "History_go_Callback";

   // Implementation support.
   String get typeName => "History";
 }

 class _LocationCrossFrame extends NativeFieldWrapperClass1 implements LocationBase {
   _LocationCrossFrame.internal();

   // Fields.
   void set href(String) native "Location_href_Setter";

   // Implementation support.
   String get typeName => "Location";
 }

 class _DOMStringMap extends NativeFieldWrapperClass1 implements Map<String, String> {
   _DOMStringMap.internal();

   bool containsValue(String value) => Maps.containsValue(this, value);
   bool containsKey(String key) native "DOMStringMap_containsKey_Callback";
   String operator [](String key) native "DOMStringMap_item_Callback";
   void operator []=(String key, String value) native "DOMStringMap_setItem_Callback";
   String putIfAbsent(String key, String ifAbsent()) => Maps.putIfAbsent(this, key, ifAbsent);
   String remove(String key) native "DOMStringMap_remove_Callback";
   void clear() => Maps.clear(this);
   void forEach(void f(String key, String value)) => Maps.forEach(this, f);
   Iterable<String> get keys native "DOMStringMap_getKeys_Callback";
   Iterable<String> get values => Maps.getValues(this);
   int get length => Maps.length(this);
   bool get isEmpty => Maps.isEmpty(this);
   bool get isNotEmpty => Maps.isNotEmpty(this);
 }

 final _printClosure = window.console.log;
 final _pureIsolatePrintClosure = (s) {
   throw new UnimplementedError("Printing from a background isolate "
                                "is not supported in the browser");
 };

 final _forwardingPrintClosure = _Utils.forwardingPrint;

  class _Timer implements Timer {
   var _canceler;

   _Timer(int milliSeconds, void callback(Timer timer), bool repeating) {

     if (repeating) {
       int id = window._setInterval(() {
         callback(this);
       }, milliSeconds);
       _canceler = () => window._clearInterval(id);
     } else {
       int id = window._setTimeout(() {
         _canceler = null;
         callback(this);
       }, milliSeconds);
       _canceler = () => window._clearTimeout(id);
     }
   }

   void cancel() {
     if (_canceler != null) {
       _canceler();
     }
     _canceler = null;
   }

   bool get isActive => _canceler != null;
 }

 get _timerFactoryClosure =>
     (int milliSeconds, void callback(Timer timer), bool repeating) {
   return new _Timer(milliSeconds, callback, repeating);
 };

 get _pureIsolateTimerFactoryClosure =>
     ((int milliSeconds, void callback(Timer time), bool repeating) =>
   throw new UnimplementedError("Timers on background isolates "
                                "are not supported in the browser"));

 void _initializeCustomElement(Element e) {
   _Utils.initializeCustomElement(e);
 }
	// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	part of html;

	class _ConsoleVariables {
	Map<String, Object> _data = new Map<String, Object>();

	/**
	* Forward member accesses to the backing JavaScript object.
	*/
	noSuchMethod(Invocation invocation) {
	String member = MirrorSystem.getName(invocation.memberName);
	if (invocation.isGetter) {
	return _data[member];
	} else if (invocation.isSetter) {
	assert(member.endsWith('='));
	member = member.substring(0, member.length - 1);
	_data[member] = invocation.positionalArguments[0];
	} else {
	return Function.apply(_data[member], invocation.positionalArguments, invocation.namedArguments);
	}
	}

	void clear() => _data.clear();

	/**
	* List all variables currently defined.
	*/
	List variables() => _data.keys.toList(growable: false);
	}

	class _Utils {
	static double dateTimeToDouble(DateTime dateTime) =>
	dateTime.millisecondsSinceEpoch.toDouble();
	static DateTime doubleToDateTime(double dateTime) {
	try {
	return new DateTime.fromMillisecondsSinceEpoch(dateTime.toInt());
	} catch(_) {
	// TODO(antonnm): treat exceptions properly in bindings and
	// find out how to treat NaNs.
	return null;
	}
	}

	static List convertToList(List list) {
	// FIXME: [possible optimization]: do not copy the array if Dart_IsArray is fine w/ it.
	final length = list.length;
	List result = new List(length);
	result.setRange(0, length, list);
	return result;
	}

	static List convertMapToList(Map map) {
	List result = [];
	map.forEach((k, v) => result.addAll([k, v]));
	return result;
	}

	static int convertCanvasElementGetContextMap(Map map) {
	int result = 0;
	if (map['alpha'] == true) result \|= 0x01;
	if (map['depth'] == true) result \|= 0x02;
	if (map['stencil'] == true) result \|= 0x4;
	if (map['antialias'] == true) result \|= 0x08;
	if (map['premultipliedAlpha'] == true) result \|= 0x10;
	if (map['preserveDrawingBuffer'] == true) result \|= 0x20;

	return result;
	}

	static List parseStackTrace(StackTrace stackTrace) {
	final regExp = new RegExp(r'#\d\s+(.) \((.):(\d+):(\d+)\)');
	List result = [];
	for (var match in regExp.allMatches(stackTrace.toString())) {
	result.add([match.group(1), match.group(2), int.parse(match.group(3)), int.parse(match.group(4))]);
	}
	return result;
	}

	static void populateMap(Map result, List list) {
	for (int i = 0; i < list.length; i += 2) {
	result[list[i]] = list[i + 1];
	}
	}

	static bool isMap(obj) => obj is Map;

	static Map createMap() => {};

	static makeUnimplementedError(String fileName, int lineNo) {
	return new UnsupportedError('[info: $fileName:$lineNo]');
	}

	static bool isTypeSubclassOf(Type type, Type other) {
	if (type == other) {
	return true;
	}
	var superclass = reflectClass(type).superclass;
	if (superclass != null) {
	return isTypeSubclassOf(superclass.reflectedType, other);
	}
	return false;
	}

	static window() native "Utils_window";
	static forwardingPrint(String message) native "Utils_forwardingPrint";
	static int _getNewIsolateId() native "Utils_getNewIsolateId";

	// The following methods were added for debugger integration to make working
	// with the Dart C mirrors API simpler.
	// TODO(jacobr): consider moving them to a separate library.
	// If Dart supported dynamic code injection, we would only inject this code
	// when the debugger is invoked.

	/**
	* Strips the private secret prefix from member names of the form
	* someName@hash.
	*/
	static String stripMemberName(String name) {
	int endIndex = name.indexOf('@');
	return endIndex > 0 ? name.substring(0, endIndex) : name;
	}

	/**
	* Takes a list containing variable names and corresponding values and
	* returns a map from normalized names to values. Variable names are assumed
	* to have list offsets 2n values at offset 2n+1. This method is required
	* because Dart_GetLocalVariables returns a list instead of an object that
	* can be queried to lookup names and values.
	*/
	static Map<String, dynamic> createLocalVariablesMap(List localVariables) {
	var map = {};
	for (int i = 0; i < localVariables.length; i+=2) {
	map[stripMemberName(localVariables[i])] = localVariables[i+1];
	}
	return map;
	}

	static _ConsoleVariables _consoleTempVariables = new _ConsoleVariables();

	/**
	* Header passed in from the Dartium Developer Tools when an expression is
	* evaluated in the console as opposed to the watch window or another context
	* that does not expect REPL support.
	*/
	static const _CONSOLE_API_SUPPORT_HEADER =
	'with ((this && this.console && this.console._commandLineAPI) \|\| {}) {\n';

	/**
	* Takes an [expression] and a list of [local] variable and returns an
	* expression for a closure with a body matching the original expression
	* where locals are passed in as arguments. Returns a list containing the
	* String expression for the closure and the list of arguments that should
	* be passed to it. The expression should then be evaluated using
	* Dart_EvaluateExpr which will generate a closure that should be invoked
	* with the list of arguments passed to this method.
	*
	* For example:
	* <code>
	* _consoleTempVariables = {'a' : someValue, 'b': someOtherValue}
	* wrapExpressionAsClosure("${_CONSOLE_API_SUPPORT_HEADER}foo + bar + a",
	* ["bar", 40, "foo", 2])
	* </code>
	* will return:
	* <code>
	* ["""(final $consoleVariables, final bar, final foo, final a, final b) =>
	* (foo + bar + a
	* )""",
	* [_consoleTempVariables, 40, 2, someValue, someOtherValue]]
	* </code>
	*/
	static List wrapExpressionAsClosure(String expression, List locals) {
	// FIXME: dartbug.com/10434 find a less fragile way to determine whether
	// we need to strip off console API support added by InjectedScript.
	var args = {};
	var sb = new StringBuffer("(");
	addArg(arg, value) {
	arg = stripMemberName(arg);
	if (args.containsKey(arg)) return;
	// We ignore arguments with the name 'this' rather than throwing an
	// exception because Dart_GetLocalVariables includes 'this' and it
	// is more convenient to filter it out here than from C++ code.
	// 'this' needs to be handled by calling Dart_EvaluateExpr with
	// 'this' as the target rather than by passing it as an argument.
	if (arg == 'this') return;
	if (args.isNotEmpty) {
	sb.write(", ");
	}
	sb.write("final $arg");
	args[arg] = value;
	}

	if (expression.indexOf(_CONSOLE_API_SUPPORT_HEADER) == 0) {
	expression = expression.substring(expression.indexOf('\n') + 1);
	expression = expression.substring(0, expression.lastIndexOf('\n'));

	addArg("\$consoleVariables", _consoleTempVariables);

	// FIXME: use a real Dart tokenizer. The following regular expressions
	// only allow setting variables at the immediate start of the expression
	// to limit the number of edge cases we have to handle.

	// Match expressions that start with "var x"
	final _VARIABLE_DECLARATION = new RegExp("^(\\s*)var\\s+(\\w+)");
	// Match expressions that start with "someExistingConsoleVar ="
	final _SET_VARIABLE = new RegExp("^(\\s)(\\w+)(\\s=)");
	// Match trailing semicolons.
	final _ENDING_SEMICOLONS = new RegExp("(;\\s)\$");
	expression = expression.replaceAllMapped(_VARIABLE_DECLARATION,
	(match) {
	var variableName = match[2];
	// Set the console variable if it isn't already set.
	if (!_consoleTempVariables._data.containsKey(variableName)) {
	_consoleTempVariables._data[variableName] = null;
	}
	return "${match[1]}\$consoleVariables.${variableName}";
	});

	expression = expression.replaceAllMapped(_SET_VARIABLE,
	(match) {
	var variableName = match[2];
	// Only rewrite if the name matches an existing console variable.
	if (_consoleTempVariables._data.containsKey(variableName)) {
	return "${match[1]}\$consoleVariables.${variableName}${match[3]}";
	} else {
	return match[0];
	}
	});

	// We only allow dart expressions not Dart statements. Silently remove
	// trailing semicolons the user might have added by accident to reduce the
	// number of spurious compile errors.
	expression = expression.replaceFirst(_ENDING_SEMICOLONS, "");
	}

	if (locals != null) {
	for (int i = 0; i < locals.length; i+= 2) {
	addArg(locals[i], locals[i+1]);
	}
	}
	// Inject all the already defined console variables.
	_consoleTempVariables._data.forEach(addArg);

	// TODO(jacobr): remove the parentheses around the expresson once
	// dartbug.com/13723 is fixed. Currently we wrap expression in parentheses
	// to ensure only valid Dart expressions are allowed. Otherwise the DartVM
	// quietly ignores trailing Dart statements resulting in user confusion
	// when part of an invalid expression they entered is ignored.
	sb..write(') => (\n$expression\n)');
	return [sb.toString(), args.values.toList(growable: false)];
	}

	/**
	* TODO(jacobr): this is a big hack to get around the fact that we are still
	* passing some JS expression to the evaluate method even when in a Dart
	* context.
	*/
	static bool isJsExpression(String expression) =>
	expression.startsWith("(function getCompletions");

	/**
	* Returns a list of completions to use if the receiver is o.
	*/
	static List<String> getCompletions(o) {
	MirrorSystem system = currentMirrorSystem();
	var completions = new Set<String>();
	addAll(Map<Symbol, dynamic> map, bool isStatic) {
	map.forEach((symbol, mirror) {
	if (mirror.isStatic == isStatic && !mirror.isPrivate) {
	var name = MirrorSystem.getName(symbol);
	if (mirror is MethodMirror && mirror.isSetter)
	name = name.substring(0, name.length - 1);
	completions.add(name);
	}
	});
	}

	addForClass(ClassMirror mirror, bool isStatic) {
	if (mirror == null)
	return;
	addAll(mirror.members, isStatic);
	if (mirror.superclass != null)
	addForClass(mirror.superclass, isStatic);
	for (var interface in mirror.superinterfaces) {
	addForClass(interface, isStatic);
	}
	}

	if (o is Type) {
	addForClass(reflectClass(o), true);
	} else {
	addForClass(reflect(o).type, false);
	}
	return completions.toList(growable: false);
	}

	/**
	* Convenience helper to get the keys of a [Map] as a [List].
	*/
	static List getMapKeyList(Map map) => map.keys.toList();

	/**
	* Returns the keys of an arbitrary Dart Map encoded as unique Strings.
	* Keys that are strings are left unchanged except that the prefix ":" is
	* added to disambiguate keys from other Dart members.
	* Keys that are not strings have # followed by the index of the key in the map
	* prepended to disambuguate. This scheme is simplistic but easy to encode and
	* decode. The use case for this method is displaying all map keys in a human
	* readable way in debugging tools.
	*/
	static List<String> getEncodedMapKeyList(dynamic obj) {
	if (obj is! Map) return null;

	var ret = new List<String>();
	int i = 0;
	return obj.keys.map((key) {
	var encodedKey;
	if (key is String) {
	encodedKey = ':$key';
	} else {
	// If the key isn't a string, return a guaranteed unique for this map
	// string representation of the key that is still somewhat human
	// readable.
	encodedKey = '#${i}:$key';
	}
	i++;
	return encodedKey;
	}).toList(growable: false);
	}

	static final RegExp _NON_STRING_KEY_REGEXP = new RegExp("^#(\\d+):(.+)\$");

	static _decodeKey(Map map, String key) {
	// The key is a regular old String.
	if (key.startsWith(':')) return key.substring(1);

	var match = _NON_STRING_KEY_REGEXP.firstMatch(key);
	if (match != null) {
	int index = int.parse(match.group(1));
	var iter = map.keys.skip(index);
	if (iter.isNotEmpty) {
	var ret = iter.first;
	// Validate that the toString representation of the key matches what we
	// expect. FIXME: throw an error if it does not.
	assert(match.group(2) == '$ret');
	return ret;
	}
	}
	return null;
	}

	/**
	* Converts keys encoded with [getEncodedMapKeyList] to their actual keys.
	*/
	static lookupValueForEncodedMapKey(Map obj, String key) => obj[_decodeKey(obj, key)];

	/**
	* Builds a constructor name with the form expected by the C Dart mirrors API.
	*/
	static String buildConstructorName(String className, String constructorName) => '$className.$constructorName';

	/**
	* Strips the class name from an expression of the form "className.someName".
	*/
	static String stripClassName(String str, String className) {
	if (str.length > className.length + 1 &&
	str.startsWith(className) && str[className.length] == '.') {
	return str.substring(className.length + 1);
	} else {
	return str;
	}
	}

	/**
	* Removes the trailing dot from an expression ending in a dot.
	* This method is used as Library prefixes include a trailing dot when using
	* the C Dart debugger API.
	*/
	static String stripTrailingDot(String str) =>
	(str != null && str[str.length - 1] == '.') ? str.substring(0, str.length - 1) : str;

	static String addTrailingDot(String str) => '${str}.';

	static bool isNoSuchMethodError(obj) => obj is NoSuchMethodError;

	// TODO(jacobr): we need a failsafe way to determine that a Node is really a
	// DOM node rather than just a class that extends Node.
	static bool isNode(obj) => obj is Node;

	static bool _isBuiltinType(ClassMirror cls) {
	// TODO(vsm): Find a less hackish way to do this.
	LibraryMirror lib = cls.owner;
	String libName = lib.uri.toString();
	return libName.startsWith('dart:');
	}

	static void register(Document document, String tag, Type type,
	String extendsTagName) {
	// TODO(vsm): Move these checks into native code.
	ClassMirror cls = reflectClass(type);
	if (_isBuiltinType(cls)) {
	throw new UnsupportedError("Invalid custom element from $libName.");
	}
	var className = MirrorSystem.getName(cls.simpleName);
	if (!cls.constructors.containsKey(new Symbol('$className.created'))) {
	throw new UnsupportedError('Class is missing constructor $className.created');
	}
	_register(document, tag, type, extendsTagName);
	}

	static void _register(Document document, String tag, Type customType,
	String extendsTagName) native "Utils_register";

	static Element createElement(Document document, String tagName) native "Utils_createElement";

	static void initializeCustomElement(HtmlElement element) native "Utils_initializeCustomElement";
	}

	class _DOMWindowCrossFrame extends NativeFieldWrapperClass1 implements
	WindowBase {
	_DOMWindowCrossFrame.internal();

	// Fields.
	HistoryBase get history native "Window_history_cross_frame_Getter";
	LocationBase get location native "Window_location_cross_frame_Getter";
	bool get closed native "Window_closed_Getter";
	int get length native "Window_length_Getter";
	WindowBase get opener native "Window_opener_Getter";
	WindowBase get parent native "Window_parent_Getter";
	WindowBase get top native "Window_top_Getter";

	// Methods.
	void close() native "Window_close_Callback";
	void postMessage(/SerializedScriptValue/ message, String targetOrigin, [List messagePorts]) native "Window_postMessage_Callback";

	// Implementation support.
	String get typeName => "Window";
	}

	class _HistoryCrossFrame extends NativeFieldWrapperClass1 implements HistoryBase {
	_HistoryCrossFrame.internal();

	// Methods.
	void back() native "History_back_Callback";
	void forward() native "History_forward_Callback";
	void go(int distance) native "History_go_Callback";

	// Implementation support.
	String get typeName => "History";
	}

	class _LocationCrossFrame extends NativeFieldWrapperClass1 implements LocationBase {
	_LocationCrossFrame.internal();

	// Fields.
	void set href(String) native "Location_href_Setter";

	// Implementation support.
	String get typeName => "Location";
	}

	class _DOMStringMap extends NativeFieldWrapperClass1 implements Map<String, String> {
	_DOMStringMap.internal();

	bool containsValue(String value) => Maps.containsValue(this, value);
	bool containsKey(String key) native "DOMStringMap_containsKey_Callback";
	String operator [](String key) native "DOMStringMap_item_Callback";
	void operator []=(String key, String value) native "DOMStringMap_setItem_Callback";
	String putIfAbsent(String key, String ifAbsent()) => Maps.putIfAbsent(this, key, ifAbsent);
	String remove(String key) native "DOMStringMap_remove_Callback";
	void clear() => Maps.clear(this);
	void forEach(void f(String key, String value)) => Maps.forEach(this, f);
	Iterable<String> get keys native "DOMStringMap_getKeys_Callback";
	Iterable<String> get values => Maps.getValues(this);
	int get length => Maps.length(this);
	bool get isEmpty => Maps.isEmpty(this);
	bool get isNotEmpty => Maps.isNotEmpty(this);
	}

	final _printClosure = window.console.log;
	final _pureIsolatePrintClosure = (s) {
	throw new UnimplementedError("Printing from a background isolate "
	"is not supported in the browser");
	};

	final _forwardingPrintClosure = _Utils.forwardingPrint;

	class _Timer implements Timer {
	var _canceler;

	_Timer(int milliSeconds, void callback(Timer timer), bool repeating) {

	if (repeating) {
	int id = window._setInterval(() {
	callback(this);
	}, milliSeconds);
	_canceler = () => window._clearInterval(id);
	} else {
	int id = window._setTimeout(() {
	_canceler = null;
	callback(this);
	}, milliSeconds);
	_canceler = () => window._clearTimeout(id);
	}
	}

	void cancel() {
	if (_canceler != null) {
	_canceler();
	}
	_canceler = null;
	}

	bool get isActive => _canceler != null;
	}

	get _timerFactoryClosure =>
	(int milliSeconds, void callback(Timer timer), bool repeating) {
	return new _Timer(milliSeconds, callback, repeating);
	};

	get _pureIsolateTimerFactoryClosure =>
	((int milliSeconds, void callback(Timer time), bool repeating) =>
	throw new UnimplementedError("Timers on background isolates "
	"are not supported in the browser"));

	void _initializeCustomElement(Element e) {
	_Utils.initializeCustomElement(e);
	}