this.updating should be a key specific lock

IPython/html/static/notebook/js/widgets/widget.js

@@ -38,6 +38,7 function(widget_manager, underscore, backbone){
             this.pending_msgs = 0;
             this.msg_throttle = 3;
             this.msg_buffer = null;
+            this.key_value_lock = null;
             this.id = model_id;
             this.views = [];
 
@@ -89,18 +90,20 function(widget_manager, underscore, backbone){
 
         // Handle when a widget is updated via the python side.
         apply_update: function (state) {
-            this.updating = true;
-            try {
+            //this.updating = true;
                 for (var key in state) {
                     if (state.hasOwnProperty(key)) {
+                    var value = state[key];
+                    this.key_value_lock = [key, value];
+                    try {
                             this.set(key, state[key]);
+                    } finally {
+                        this.key_value_lock = null;
+                    }
                     }
                 }
                 //TODO: are there callbacks that make sense in this case?  If so, attach them here as an option
                 this.save();
-            } finally {
-                this.updating = false;
-            }
         },
 
 
@@ -131,7 +134,6 function(widget_manager, underscore, backbone){
             // Only send updated state if the state hasn't been changed 
             // during an update.
             if (this.comm !== undefined) {
-                if (!this.updating) {
                     if (this.pending_msgs >= this.msg_throttle) {
                         // The throttle has been exceeded, buffer the current msg so
                         // it can be sent once the kernel has finished processing 
@@ -141,7 +143,10 function(widget_manager, underscore, backbone){
                                 this.msg_buffer = $.extend({}, model_json); // Copy
                             }
                             for (attr in options.attrs) {
-                                this.msg_buffer[attr] = options.attrs[attr];
+                            var value = options.attrs[attr];
+                            if (this.key_value_lock === null || attr != this.key_value_lock[0] || value != this.key_value_lock[1]) {
+                                this.msg_buffer[attr] = value;
+                            }
                             }
                         } else {
                             this.msg_buffer = $.extend({}, model_json); // Copy
@@ -155,7 +160,10 function(widget_manager, underscore, backbone){
                         if (method =='patch') {
                             send_json = {};
                             for (attr in options.attrs) {
-                                send_json[attr] = options.attrs[attr];
+                            var value = options.attrs[attr];
+                            if (this.key_value_lock === null || attr != this.key_value_lock[0] || value != this.key_value_lock[1]) {
+                                send_json[attr] = value;
+                            }
                             }
                         }
 
@@ -164,7 +172,6 function(widget_manager, underscore, backbone){
                         this.pending_msgs++;
                     }
                 }
-            }
             
             // Since the comm is a one-way communication, assume the message 
             // arrived.