Added `visible` property to all widgets

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

@@ -307,10 +307,21 @@ define(["components/underscore/underscore-min",
         var WidgetView = Backbone.View.extend({
             
             initialize: function() {
+                this.visible = true;
                 this.model.on('change',this.update,this);
             },
             
             update: function() {
+                if (this.model.get('visible') != undefined) {
+                    if (this.visible != this.model.get('visible')) {
+                        this.visible = this.model.get('visible');
+                        if (this.visible) {
+                            this.$el.show();
+                        } else {
+                            this.$el.hide();
+                        }
+                    }
+                }
                 if (this.model.css != undefined) {
                     for (var selector in this.model.css) {
                         if (this.model.css.hasOwnProperty(selector)) {

IPython/html/widgets/widget.py

@@ -21,7 +21,7 @@ import os
 import IPython
 from IPython.kernel.comm import Comm
 from IPython.config import LoggingConfigurable
-from IPython.utils.traitlets import Unicode, Dict, List, Instance
+from IPython.utils.traitlets import Unicode, Dict, List, Instance, Bool
 from IPython.display import Javascript, display
 from IPython.utils.py3compat import string_types
 
@@ -50,6 +50,7 @@ class Widget(LoggingConfigurable):
     default_view_name = Unicode(help="""Default view registered in the frontend
         to use to represent the widget.""")
     parent = Instance('IPython.html.widgets.widget.Widget')
+    visible = Bool(True, help="Whether or not the widget is visible.")
 
     def _parent_changed(self, name, old, new):
         if self._displayed:
@@ -107,7 +108,7 @@ class Widget(LoggingConfigurable):
     
     # Properties      
     def _get_keys(self):
-        keys = ['_css']
+        keys = ['_css', 'visible']
         keys.extend(self._keys)
         return keys
     keys = property(_get_keys)