diff --git a/lib/ace/mode/xquery_worker.js b/lib/ace/mode/xquery_worker.js
index cf01e423..863a06e3 100644
--- a/lib/ace/mode/xquery_worker.js
+++ b/lib/ace/mode/xquery_worker.js
@@ -36,8 +36,6 @@ var Mirror = require("../worker/mirror").Mirror;
 var JSONParseTreeHandler  = require("./xquery/JSONParseTreeHandler").JSONParseTreeHandler;
 var XQueryParser  = require("./xquery/XQueryParser").XQueryParser;
 var SyntaxHighlighter = require("../mode/xquery/visitors/SyntaxHighlighter").SyntaxHighlighter;
-window.addEventListener = function() {};
-
 
 var XQueryWorker = exports.XQueryWorker = function(sender) {
     Mirror.call(this, sender);
diff --git a/lib/ace/worker/worker_client.js b/lib/ace/worker/worker_client.js
index d3b9c3c8..8f11ff4b 100644
--- a/lib/ace/worker/worker_client.js
+++ b/lib/ace/worker/worker_client.js
@@ -3,7 +3,7 @@
  *
  * Copyright (c) 2010, Ajax.org B.V.
  * All rights reserved.
- * 
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *     * Redistributions of source code must retain the above copyright
@@ -14,7 +14,7 @@
  *     * Neither the name of Ajax.org B.V. nor the
  *       names of its contributors may be used to endorse or promote products
  *       derived from this software without specific prior written permission.
- * 
+ *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
@@ -36,14 +36,15 @@ var EventEmitter = require("../lib/event_emitter").EventEmitter;
 var config = require("../config");
 
 var WorkerClient = function(topLevelNamespaces, mod, classname) {
-
     this.changeListener = this.changeListener.bind(this);
+    this.onMessage = this.onMessage.bind(this);
+    this.onError = this.onError.bind(this);
 
+    var workerUrl;
     if (config.get("packaged")) {
-        this.$worker = new Worker(config.moduleUrl(mod, "worker"));
-    }
-    else {
-        var workerUrl;
+        workerUrl = config.moduleUrl(mod, "worker");
+    } else {
+        var normalizePath = this.$normalizePath;
         if (typeof require.supports !== "undefined" && require.supports.indexOf("ucjs2-pinf-0") >= 0) {
             // We are running in the sourcemint loader.
             workerUrl = require.nameToUrl("ace/worker/worker_sourcemint");
@@ -52,19 +53,16 @@ var WorkerClient = function(topLevelNamespaces, mod, classname) {
             // nameToUrl is renamed to toUrl in requirejs 2
             if (require.nameToUrl && !require.toUrl)
                 require.toUrl = require.nameToUrl;
-            workerUrl = this.$normalizePath(require.toUrl("ace/worker/worker", null, "_"));
+            workerUrl = normalizePath(require.toUrl("ace/worker/worker", null, "_"));
         }
-        this.$worker = new Worker(workerUrl);
 
         var tlns = {};
-        for (var i=0; i<topLevelNamespaces.length; i++) {
-            var ns = topLevelNamespaces[i];
-            var path = this.$normalizePath(require.toUrl(ns, null, "_").replace(/.js(\?.*)?$/, ""));
-
-            tlns[ns] = path;
-        }
+        topLevelNamespaces.forEach(function(ns) {
+            tlns[ns] = normalizePath(require.toUrl(ns, null, "_").replace(/.js(\?.*)?$/, ""));
+        });
     }
 
+    this.$worker = new Worker(workerUrl);
     this.$worker.postMessage({
         init : true,
         tlns: tlns,
@@ -75,12 +73,20 @@ var WorkerClient = function(topLevelNamespaces, mod, classname) {
     this.callbackId = 1;
     this.callbacks = {};
 
-    var _self = this;
-    this.$worker.onerror = function(e) {
+    this.$worker.onerror = this.onError;
+    this.$worker.onmessage = this.onMessage;
+};
+
+(function(){
+
+    oop.implement(this, EventEmitter);
+
+    this.onError = function(e) {
         window.console && console.log && console.log(e);
         throw e;
     };
-    this.$worker.onmessage = function(e) {
+
+    this.onMessage = function(e) {
         var msg = e.data;
         switch(msg.type) {
             case "log":
@@ -88,23 +94,18 @@ var WorkerClient = function(topLevelNamespaces, mod, classname) {
                 break;
 
             case "event":
-                _self._emit(msg.name, {data: msg.data});
+                this._emit(msg.name, {data: msg.data});
                 break;
 
             case "call":
-                var callback = _self.callbacks[msg.id];
+                var callback = this.callbacks[msg.id];
                 if (callback) {
                     callback(msg.data);
-                    delete _self.callbacks[msg.id];
+                    delete this.callbacks[msg.id];
                 }
                 break;
         }
     };
-};
-
-(function(){
-
-    oop.implement(this, EventEmitter);
 
     this.$normalizePath = function(path) {
         if (!location.host) // needed for file:// protocol
@@ -166,6 +167,51 @@ var WorkerClient = function(topLevelNamespaces, mod, classname) {
 
 }).call(WorkerClient.prototype);
 
+
+var UIWorkerClient = function(topLevelNamespaces, mod, classname) {
+    this.changeListener = this.changeListener.bind(this);
+    this.callbackId = 1;
+    this.callbacks = {};
+    this.messageBuffer = [];
+
+    var main = null;
+    var sender = Object.create(EventEmitter);
+    var _self = this;
+
+    this.$worker = {}
+    this.$worker.postMessage = function(e) {
+        _self.messageBuffer.push(e);
+        main && setTimeout(processNext);
+    };
+
+    var processNext = function() {
+        var msg = _self.messageBuffer.shift();
+        if (msg.command)
+            main[msg.command].apply(main, msg.args);
+        else if (msg.event)
+            sender._emit(msg.event, msg.data);
+    };
+
+    sender.postMessage = function(msg) {
+        _self.onMessage({data: msg});
+    };
+    sender.callback = function(data, callbackId) {
+        this.postMessage({type: "call", id: callbackId, data: data});
+    };
+    sender.emit = function(name, data) {
+        this.postMessage({type: "event", name: name, data: data});
+    };
+
+    require([mod], function(Main) {
+        main = new Main[classname](sender);
+        while (_self.messageBuffer.length)
+            processNext();
+    });
+};
+
+UIWorkerClient.prototype = WorkerClient.prototype;
+
+exports.UIWorkerClient = UIWorkerClient;
 exports.WorkerClient = WorkerClient;
 
 });