for discussion: support for zones in DOM events

sdk/lib/async/zone.dart

 // Copyright (c) 2013, 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 dart.async;
 
 /**
  * A Zone represents the asynchronous version of a dynamic extent. Asynchronous
  * callbacks are executed in the zone they have been queued in. For example,
  * the callback of a `future.then` is executed in the same zone as the one where
@@ skipping 112 matching lines @@
    * of `this`.
    */
   void _addChild(_Zone child);
 
   /**
    * Removes [child] from `this`' children.
    *
    * This usually means that the [child] has finished executing and is done.
    */
   void _removeChild(_Zone child);
+
+  /**
+   * True if this is the default zone, otherwise false.
+   */
+  bool get isDefault;
 }
 
 /**
  * Basic implementation of a [_Zone]. This class is intended for subclassing.
  */
 class _ZoneBase implements _Zone {
   /// The parent zone. [null] if `this` is the default zone.
   final _Zone _parentZone;
 
   /// The children of this zone. A child's [_parentZone] is `this`.
   // TODO(floitsch): this should be a double-linked list.
   final List<_Zone> _children = <_Zone>[];
 
   /// The number of outstanding (asynchronous) callbacks. As long as the
   /// number is greater than 0 it means that the zone is not done yet.
   int _openCallbacks = 0;
 
   bool _isExecutingCallback = false;
 
   _ZoneBase(this._parentZone) {
     _parentZone._addChild(this);
   }
 
   _ZoneBase._defaultZone() : _parentZone = null {
     assert(this is _DefaultZone);
   }
 
+  bool get isDefault => false;
+
   _Zone get _errorZone => _parentZone._errorZone;
 
   void handleUncaughtError(error) {
     _parentZone.handleUncaughtError(error);
   }
 
   bool inSameErrorZone(_Zone otherZone) => _errorZone == otherZone._errorZone;
 
   _Zone fork() => this;
 
@@ skipping 144 matching lines @@
     throw new ArgumentError(child);
   }
 }
 
 /**
  * The default-zone that conceptually surrounds the `main` function.
  */
 class _DefaultZone extends _ZoneBase {
   _DefaultZone() : super._defaultZone();
 
+  bool get isDefault => true;
+
   _Zone get _errorZone => this;
 
   handleUncaughtError(error) {
     _scheduleAsyncCallback(() {
       print("Uncaught Error: ${error}");
       var trace = getAttachedStackTrace(error);
       _attachStackTrace(error, null);
       if (trace != null) {
         print("Stack Trace:\n$trace\n");
       }
@@ skipping 215 matching lines @@
   if (onError == null && onDone == null) return body();
   if (onError == null) {
     _WaitForCompletionZone zone =
         new _WaitForCompletionZone(_Zone._current, onDone);
     return zone.runWaitForCompletion(body);
   }
   if (onDone == null) onDone = _nullDoneHandler;
   _CatchErrorsZone zone = new _CatchErrorsZone(_Zone._current, onError, onDone);
   return zone.runWaitForCompletion(body);
 }
+
+/**
+ * Gets the current zone. See [runZonedExperimental].
+ *
+ * *Warning*: all Zone APIs are subject to change. Your code may break in the
+ * future with [NoSuchMethodError] or cause have other unexpected behavior.
+ */
+// TODO(jmesserly): how do we expose only the features that dart:html needs?
+// Crazy idea: move EventStreamSubscription to be an abstract base class in
+// dart:async (possibly renaming it) and make the calls to add and remove the
+// listener abstract. Then dart:html overrides it to use DOM addEventListener
+// and removeEventListener.
+get currentZoneExperimental => _Zone.current;