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.
         },
@@ -48,7 +44,15 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
 #-----------------------------------------------------------------------------
@@ -114,7 +113,7 b' class Widget(LoggingConfigurable):'
     def _handle_msg(self, msg):
         """Called when a msg is recieved from the frontend"""
         data = msg['content']['data']
-
+        
         # Handle backbone sync methods CREATE, PATCH, and UPDATE
         if 'sync_method' in data and 'sync_data' in data:
             sync_method = data['sync_method']
@@ -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

@@ -28,15 +28,16 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):
@@ -57,24 +58,36 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)
-                    nargs = len(argspec[0])
-
-                    # Bound methods have an additional 'self' argument
-                    if isinstance(handler, types.MethodType):
-                        nargs -= 1
-
-                    # Call the callback
-                    if nargs == 0:
-                        handler()
-                    elif nargs == 1:
-                        handler(self)
-                    else:
-                        raise TypeError('ButtonWidget click callback must ' \
-                            'accept 0 or 1 arguments.')
+        
+        for handler in self._click_handlers:
+            if callable(handler):
+                argspec = inspect.getargspec(handler)
+                nargs = len(argspec[0])
+
+                # Bound methods have an additional 'self' argument
+                if isinstance(handler, types.MethodType):
+                    nargs -= 1
+
+                # Call the callback
+                if nargs == 0:
+                    handler()
+                elif nargs == 1:
+                    handler(self)
+                else:
+                    raise TypeError('ButtonWidget click callback must ' \
+                        'accept 0 or 1 arguments.')
+