Changed button to use custom messages instead of state to communicate events.

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

@@ -75,7 +75,7 b' define(["components/underscore/underscore-min",'
                 cell = this.last_modified_view.cell;
             }
             var callbacks = this._make_callbacks(cell);
-            var data = {custom_content: content};
+            var data = {'custom_content': content};
             this.comm.send(data, callbacks);   
         },
 

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

@@ -25,11 +25,7 b' define(["notebook/js/widget"], function(widget_manager){'
         render : function(){
             var that = this;
             this.setElement($("<button />")
-                .addClass('btn')
-                .click(function() {
-                    that.model.set('clicks', that.model.get('clicks') + 1);
-                    that.model.update_other_views(that);
-                }));
+                .addClass('btn'));
 
             this.update(); // Set defaults.
         },
@@ -49,6 +45,14 b' define(["notebook/js/widget"], function(widget_manager){'
             return IPython.WidgetView.prototype.update.call(this);
         },
         
+        events: {
+            'click': '_handle_click',
+        },
+        
+        _handle_click: function(){
+            this.model.last_modified_view = this; // For callbacks.
+            this.model.send({event: 'click'});
+        },
     });
 
     widget_manager.register_widget_view('ButtonView', ButtonView);

IPython/html/widgets/widget.py

@@ -27,7 +27,6 b' from IPython.utils.traitlets import Unicode, Dict, List, Instance, Bool'
 from IPython.display import Javascript, display
 from IPython.utils.py3compat import string_types
 
-
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
@@ -384,7 +383,6 b' class Widget(LoggingConfigurable):'
         ----------
         view_name: unicode (optional)
             View to display in the frontend.  Overrides default_view_name."""
-
         if not view_name:
             view_name = self.default_view_name
         

IPython/html/widgets/widget_button.py

@@ -28,16 +28,17 b' class ButtonWidget(Widget):'
     default_view_name = Unicode('ButtonView')
 
     # Keys
-    _keys = ['clicks', 'description', 'disabled']
-    clicks = Int(0, help="Number of times the button has been clicked.")
+    _keys = ['description', 'disabled']
     description = Unicode('', help="Description of the button (label).")
     disabled = Bool(False, help="Enable or disable user changes.")
     
 
     def __init__(self, **kwargs):
-        self._click_handlers = []
         super(ButtonWidget, self).__init__(**kwargs)
 
+        self._click_handlers = []
+        self.on_msg(self._handle_button_msg)
+
 
     def on_click(self, callback, remove=False):
         """Register a callback to execute when the button is clicked.  The
@@ -57,10 +58,21 b' class ButtonWidget(Widget):'
             self._click_handlers.append(callback)
 
 
-    def _clicks_changed(self, name, old, new):
-        """Handles when the clicks property has been changed.  Fires on_click
+    def _handle_button_msg(self, content):
+        """Hanlde a msg from the front-end
+
+        Parameters
+        ----------
+        content: dict
+            Content of the msg."""
+        if 'event' in content and content['event'] == 'click':
+            self._handle_click()
+
+
+    def _handle_click(self):
+        """Handles when the button has been clicked.  Fires on_click
         callbacks when appropriate."""
-        if new > old:
+        
             for handler in self._click_handlers:
                 if callable(handler):
                     argspec = inspect.getargspec(handler)
@@ -78,3 +90,4 b' class ButtonWidget(Widget):'
                     else:
                         raise TypeError('ButtonWidget click callback must ' \
                             'accept 0 or 1 arguments.')
+