Implement MouseEvent#currentTarget and document MouseEvent#target.

Relates to #995

src/core/Emitter.js

@@ -80,10 +80,14 @@ var Emitter = {
         var handlers = this._callbacks && this._callbacks[type];
         if (!handlers)
             return false;
-        var args = [].slice.call(arguments, 1);
+        var args = [].slice.call(arguments, 1),
+            setTarget = event && 'target' in event &&
+                !('currentTarget' in event);
         // Create a clone of the handlers list so changes caused by on / off
         // won't throw us off track here:
         handlers = handlers.slice();
+        if (setTarget)
+            event.currentTarget = this;
         for (var i = 0, l = handlers.length; i < l; i++) {
             if (handlers[i].apply(this, args) === false) {
                 // If the handler returns false, prevent the default behavior
@@ -94,6 +98,8 @@ var Emitter = {
                 break;
            }
         }
+        if (setTarget)
+            delete event.currentTarget;
         return true;
     },
 

src/event/MouseEvent.js

@@ -51,6 +51,25 @@ var MouseEvent = Event.extend(/** @lends MouseEvent# */{
      * @type Point
      */
 
+    /**
+     * The item that dispatched the event. It is different from
+     * {@link #currentTarget} when the event handler is called during
+     * the bubbling phase of the event.
+     *
+     * @name MouseEvent#target
+     * @type Item
+     */
+
+    /**
+     * The current target for the event, as the event traverses the scene graph.
+     * It always refers to the element the event handler has been attached to as
+     * opposed to {@link #target} which identifies the element on
+     * which the event occurred.
+     *
+     * @name MouseEvent#currentTarget
+     * @type Item
+     */
+
     // DOCS: document MouseEvent#delta
     /**
      * @name MouseEvent#delta