Add state packet delta compression.

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

@@ -32,7 +32,7 b' define(["static/components/underscore/underscore-min.js",'
         //--------------------------------------------------------------------
         var WidgetModel = Backbone.Model.extend({
             apply: function(sender) {
-                this.save();
+                this.save(this.changedAttributes(), {patch: true});
 
                 for (var index in this.views) {
                     var view = this.views[index];
@@ -95,7 +95,7 b' define(["static/components/underscore/underscore-min.js",'
             
             var that = this;
             Backbone.sync = function(method, model, options, error) {
-                var result = that.send_sync(method, model);
+                var result = that.send_sync(method, model, options);
                 if (options.success) {
                   options.success(result);
                 }
@@ -214,6 +214,7 b' define(["static/components/underscore/underscore-min.js",'
                     }
                 }
             }
+            comm.model.id = comm.comm_id;
             comm.model.save();
             this.updating = false;
         }
@@ -234,7 +235,7 b' define(["static/components/underscore/underscore-min.js",'
         }
 
         // Send widget state to python backend.
-        WidgetManager.prototype.send_sync = function (method, model) {
+        WidgetManager.prototype.send_sync = function (method, model, options) {
             var model_json = model.toJSON();
 
             // Only send updated state if the state hasn't been changed during an update.
@@ -250,10 +251,21 b' define(["static/components/underscore/underscore-min.js",'
                         clear_output : $.proxy(outputarea.handle_clear_output, outputarea)}
                     };
                 };
-                var data = {sync_method: method, sync_data: model_json};
+
+                // If this is a patch operation, just send the changes.
+                var send_json = model_json;
+                if (method=='patch') {
+                    send_json = {};
+                    for (var attr in options.attrs) {
+                        send_json[attr] = options.attrs[attr];
+                    }
+                }
+                var data = {sync_method: method, sync_data: send_json};
                 comm.send(data, callbacks);    
             }
             
+            // Since the comm is a one-way communication, assume the message 
+            // arrived.
             return model_json;
         }
 

IPython/html/widgets/widget.py

@@ -96,11 +96,10 b' class Widget(LoggingConfigurable):'
     ### Event handlers
     def _handle_msg(self, msg):
         
-        # Handle backbone sync methods
+        # Handle backbone sync methods CREATE, PATCH, and UPDATE
         sync_method = msg['content']['data']['sync_method']
         sync_data = msg['content']['data']['sync_data']
-        if sync_method.lower() in ['create', 'update']:
-            self._handle_recieve_state(sync_data)
+        self._handle_recieve_state(sync_data) # handles all methods
     
     
     def _handle_recieve_state(self, sync_data):
@@ -119,7 +118,7 b' class Widget(LoggingConfigurable):'
         if not self._property_lock and self.comm is not None:
             # TODO: Validate properties.
             # Send new state to frontend
-            self.send_state()
+            self.send_state(key=name)
 
 
     def _handle_close(self):
@@ -154,8 +153,15 b' class Widget(LoggingConfigurable):'
         return None
 
 
-    def send_state(self):
+    def send_state(self, key=None):
         state = {}
+
+        # If a key is provided, just send the state of that key.
+        keys = []
+        if key is None:
+            keys.extend(self.keys)
+        else:
+            keys.append(key)
         for key in self.keys:
             try:
                 state[key] = getattr(self, key)