Merge pull request #6494 from takluyver/widget-comm-require

Allow widget views to be loaded from require modules

IPython/html/static/widgets/js/manager.js

@@ -1,190 +1,204 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     "underscore",
     "backbone",
     "jquery",
     "base/js/namespace"
 ], function (_, Backbone, $, IPython) {
-
+    "use strict";
     //--------------------------------------------------------------------
     // WidgetManager class
     //--------------------------------------------------------------------
     var WidgetManager = function (comm_manager, notebook) {
         // Public constructor
         WidgetManager._managers.push(this);
 
         // Attach a comm manager to the 
         this.keyboard_manager = notebook.keyboard_manager;
         this.notebook = notebook;
         this.comm_manager = comm_manager;
         this._models = {}; /* Dictionary of model ids and model instances */
 
         // Register with the comm manager.
         this.comm_manager.register_target('ipython.widget', $.proxy(this._handle_comm_open, this));
     };
 
     //--------------------------------------------------------------------
     // Class level
     //--------------------------------------------------------------------
     WidgetManager._model_types = {}; /* Dictionary of model type names (target_name) and model types. */
     WidgetManager._view_types = {}; /* Dictionary of view names and view types. */
     WidgetManager._managers = []; /* List of widget managers */
 
     WidgetManager.register_widget_model = function (model_name, model_type) {
         // Registers a widget model by name.
         WidgetManager._model_types[model_name] = model_type;
     };
 
     WidgetManager.register_widget_view = function (view_name, view_type) {
         // Registers a widget view by name.
         WidgetManager._view_types[view_name] = view_type;
     };
 
     //--------------------------------------------------------------------
     // Instance level
     //--------------------------------------------------------------------
     WidgetManager.prototype.display_view = function(msg, model) {
         // Displays a view for a particular model.
         var cell = this.get_msg_cell(msg.parent_header.msg_id);
         if (cell === null) {
             console.log("Could not determine where the display" + 
                 " message was from.  Widget will not be displayed");
         } else {
-            var view = this.create_view(model, {cell: cell});
-            if (view === null) {
-                console.error("View creation failed", model);
-            }
-            this._handle_display_view(view);
-            if (cell.widget_subarea) {
-                cell.widget_subarea.append(view.$el);
-            }
-            view.trigger('displayed');
+            var that = this;
+            this.create_view(model, {cell: cell, callback: function(view) {
+                that._handle_display_view(view);
+                if (cell.widget_subarea) {
+                    cell.widget_subarea.append(view.$el);
+                }
+                view.trigger('displayed');
+            }});
         }
     };
 
     WidgetManager.prototype._handle_display_view = function (view) {
         // Have the IPython keyboard manager disable its event
         // handling so the widget can capture keyboard input.
         // Note, this is only done on the outer most widgets.
         if (this.keyboard_manager) {
             this.keyboard_manager.register_events(view.$el);
         
         if (view.additional_elements) {
             for (var i = 0; i < view.additional_elements.length; i++) {
                     this.keyboard_manager.register_events(view.additional_elements[i]);
             }
         } 
         }
     };
+    
 
-    WidgetManager.prototype.create_view = function(model, options, view) {
+    WidgetManager.prototype.create_view = function(model, options) {
         // Creates a view for a particular model.
+        
         var view_name = model.get('_view_name');
-        var ViewType = WidgetManager._view_types[view_name];
-        if (ViewType) {
-
-            // If a view is passed into the method, use that view's cell as
-            // the cell for the view that is created.
-            options = options || {};
-            if (view !== undefined) {
-                options.cell = view.options.cell;
+        var view_mod = model.get('_view_module');
+        var errback = options.errback || function(err) {console.log(err);};
+
+        var instantiate_view = function(ViewType) {
+            if (ViewType) {
+                // If a view is passed into the method, use that view's cell as
+                // the cell for the view that is created.
+                options = options || {};
+                if (options.parent !== undefined) {
+                    options.cell = options.parent.options.cell;
+                }
+
+                // Create and render the view...
+                var parameters = {model: model, options: options};
+                var view = new ViewType(parameters);
+                view.render();
+                model.on('destroy', view.remove, view);
+                options.callback(view);
+            } else {
+                errback({unknown_view: true, view_name: view_name,
+                         view_module: view_mod});
             }
+        };
 
-            // Create and render the view...
-            var parameters = {model: model, options: options};
-            view = new ViewType(parameters);
-            view.render();
-            model.on('destroy', view.remove, view);
-            return view;
+        if (view_mod) {
+            require([view_mod], function(module) {
+                instantiate_view(module[view_name]);
+            }, errback);
+        } else {
+            instantiate_view(WidgetManager._view_types[view_name]);
         }
-        return null;
     };
 
     WidgetManager.prototype.get_msg_cell = function (msg_id) {
         var cell = null;
         // First, check to see if the msg was triggered by cell execution.
         if (this.notebook) {
             cell = this.notebook.get_msg_cell(msg_id);
         }
         if (cell !== null) {
             return cell;
         }
         // Second, check to see if a get_cell callback was defined
         // for the message.  get_cell callbacks are registered for
         // widget messages, so this block is actually checking to see if the
         // message was triggered by a widget.
         var kernel = this.comm_manager.kernel;
         if (kernel) {
             var callbacks = kernel.get_callbacks_for_msg(msg_id);
             if (callbacks && callbacks.iopub &&
                 callbacks.iopub.get_cell !== undefined) {
                 return callbacks.iopub.get_cell();
             }
         }
         
         // Not triggered by a cell or widget (no get_cell callback 
         // exists).
         return null;
     };
 
     WidgetManager.prototype.callbacks = function (view) {
         // callback handlers specific a view
         var callbacks = {};
         if (view && view.options.cell) {
 
             // Try to get output handlers
             var cell = view.options.cell;
             var handle_output = null;
             var handle_clear_output = null;
             if (cell.output_area) {
                 handle_output = $.proxy(cell.output_area.handle_output, cell.output_area);
                 handle_clear_output = $.proxy(cell.output_area.handle_clear_output, cell.output_area);
             }
 
             // Create callback dict using what is known
             var that = this;
             callbacks = {
                 iopub : {
                     output : handle_output,
                     clear_output : handle_clear_output,
 
                     // Special function only registered by widget messages.
                     // Allows us to get the cell for a message so we know
                     // where to add widgets if the code requires it.
                     get_cell : function () {
                         return cell;
                     },
                 },
             };
         }
         return callbacks;
     };
 
     WidgetManager.prototype.get_model = function (model_id) {
         // Look-up a model instance by its id.
         var model = this._models[model_id];
         if (model !== undefined && model.id == model_id) {
             return model;
         }
         return null;
     };
 
     WidgetManager.prototype._handle_comm_open = function (comm, msg) {
         // Handle when a comm is opened.
         var that = this;
         var model_id = comm.comm_id;
         var widget_type_name = msg.content.data.model_name;
         var widget_model = new WidgetManager._model_types[widget_type_name](this, model_id, comm);
         widget_model.on('comm:close', function () {
           delete that._models[model_id];
         });
         this._models[model_id] = widget_model;
     };
 
     // Backwards compatability.
     IPython.WidgetManager = WidgetManager;
 
     return {'WidgetManager': WidgetManager};
 });

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

@@ -1,610 +1,613 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define(["widgets/js/manager",
         "underscore",
         "backbone", 
         "jquery",   
         "base/js/namespace",
 ], function(widgetmanager, _, Backbone, $, IPython){
 
     var WidgetModel = Backbone.Model.extend({
         constructor: function (widget_manager, model_id, comm) {
             // Constructor
             //
             // Creates a WidgetModel instance.
             //
             // Parameters
             // ----------
             // widget_manager : WidgetManager instance
             // model_id : string
             //      An ID unique to this model.
             // comm : Comm instance (optional)
             this.widget_manager = widget_manager;
             this._buffered_state_diff = {};
             this.pending_msgs = 0;
             this.msg_buffer = null;
             this.state_lock = null;
             this.id = model_id;
             this.views = {};
 
             if (comm !== undefined) {
                 // Remember comm associated with the model.
                 this.comm = comm;
                 comm.model = this;
 
                 // Hook comm messages up to model.
                 comm.on_close($.proxy(this._handle_comm_closed, this));
                 comm.on_msg($.proxy(this._handle_comm_msg, this));
             }
             return Backbone.Model.apply(this);
         },
 
         send: function (content, callbacks) {
             // Send a custom msg over the comm.
             if (this.comm !== undefined) {
                 var data = {method: 'custom', content: content};
                 this.comm.send(data, callbacks);
                 this.pending_msgs++;
             }
         },
 
         _handle_comm_closed: function (msg) {
             // Handle when a widget is closed.
             this.trigger('comm:close');
             this.stopListening();
             this.trigger('destroy', this);
             delete this.comm.model; // Delete ref so GC will collect widget model.
             delete this.comm;
             delete this.model_id; // Delete id from model so widget manager cleans up.
             for (var id in this.views) {
                 if (this.views.hasOwnProperty(id)) {
                     this.views[id].remove();
                 }
             }
         },
 
         _handle_comm_msg: function (msg) {
             // Handle incoming comm msg.
             var method = msg.content.data.method;
             switch (method) {
                 case 'update':
                     this.set_state(msg.content.data.state);
                     break;
                 case 'custom':
                     this.trigger('msg:custom', msg.content.data.content);
                     break;
                 case 'display':
                     this.widget_manager.display_view(msg, this);
                     break;
             }
         },
 
         set_state: function (state) {
             // Handle when a widget is updated via the python side.
             this.state_lock = state;
             try {
                 var that = this;
                 WidgetModel.__super__.set.apply(this, [Object.keys(state).reduce(function(obj, key) {
                     obj[key] = that._unpack_models(state[key]);
                     return obj;
                 }, {})]);
             } finally {
                this.state_lock = null;
             }
         },
 
         _handle_status: function (msg, callbacks) {
             // Handle status msgs.
 
             // execution_state : ('busy', 'idle', 'starting')
             if (this.comm !== undefined) {
                 if (msg.content.execution_state ==='idle') {
                     // Send buffer if this message caused another message to be
                     // throttled.
                     if (this.msg_buffer !== null &&
                         (this.get('msg_throttle') || 3) === this.pending_msgs) {
                         var data = {method: 'backbone', sync_method: 'update', sync_data: this.msg_buffer};
                         this.comm.send(data, callbacks);
                         this.msg_buffer = null;
                     } else {
                         --this.pending_msgs;
                     }
                 }
             }
         },
 
         callbacks: function(view) {
             // Create msg callbacks for a comm msg.
             var callbacks = this.widget_manager.callbacks(view);
 
             if (callbacks.iopub === undefined) {
                 callbacks.iopub = {};
             }
 
             var that = this;
             callbacks.iopub.status = function (msg) {
                 that._handle_status(msg, callbacks);
             };
             return callbacks;
         },
 
         set: function(key, val, options) {
             // Set a value.
             var return_value = WidgetModel.__super__.set.apply(this, arguments);
 
             // Backbone only remembers the diff of the most recent set()
             // operation.  Calling set multiple times in a row results in a 
             // loss of diff information.  Here we keep our own running diff.
             this._buffered_state_diff = $.extend(this._buffered_state_diff, this.changedAttributes() || {});
             return return_value;
         },
 
         sync: function (method, model, options) {
             // Handle sync to the back-end.  Called when a model.save() is called.
 
             // Make sure a comm exists.
             var error = options.error || function() {
                 console.error('Backbone sync error:', arguments);
             };
             if (this.comm === undefined) {
                 error();
                 return false;
             }
 
             // Delete any key value pairs that the back-end already knows about.
             var attrs = (method === 'patch') ? options.attrs : model.toJSON(options);
             if (this.state_lock !== null) {
                 var keys = Object.keys(this.state_lock);
                 for (var i=0; i<keys.length; i++) {
                     var key = keys[i];
                     if (attrs[key] === this.state_lock[key]) {
                         delete attrs[key];
                     }
                 }
             }
 
             // Only sync if there are attributes to send to the back-end.
             attrs = this._pack_models(attrs);
             if (_.size(attrs) > 0) {
 
                 // If this message was sent via backbone itself, it will not
                 // have any callbacks.  It's important that we create callbacks
                 // so we can listen for status messages, etc...
                 var callbacks = options.callbacks || this.callbacks();
 
                 // Check throttle.
                 if (this.pending_msgs >= (this.get('msg_throttle') || 3)) {
                     // The throttle has been exceeded, buffer the current msg so
                     // it can be sent once the kernel has finished processing 
                     // some of the existing messages.
                     
                     // Combine updates if it is a 'patch' sync, otherwise replace updates
                     switch (method) {
                         case 'patch':
                             this.msg_buffer = $.extend(this.msg_buffer || {}, attrs);
                             break;
                         case 'update':
                         case 'create':
                             this.msg_buffer = attrs;
                             break;
                         default:
                             error();
                             return false;
                     }
                     this.msg_buffer_callbacks = callbacks;
 
                 } else {
                     // We haven't exceeded the throttle, send the message like 
                     // normal.
                     var data = {method: 'backbone', sync_data: attrs};
                     this.comm.send(data, callbacks);
                     this.pending_msgs++;
                 }
             }
             // Since the comm is a one-way communication, assume the message 
             // arrived.  Don't call success since we don't have a model back from the server
             // this means we miss out on the 'sync' event.
             this._buffered_state_diff = {};
         },
 
         save_changes: function(callbacks) {
             // Push this model's state to the back-end
             //
             // This invokes a Backbone.Sync.
             this.save(this._buffered_state_diff, {patch: true, callbacks: callbacks});
         },
 
         _pack_models: function(value) {
             // Replace models with model ids recursively.
             var that = this;
             var packed;
             if (value instanceof Backbone.Model) {
                 return "IPY_MODEL_" + value.id;
 
             } else if ($.isArray(value)) {
                 packed = [];
                 _.each(value, function(sub_value, key) {
                     packed.push(that._pack_models(sub_value));
                 });
                 return packed;
 
             } else if (value instanceof Object) {
                 packed = {};
                 _.each(value, function(sub_value, key) {
                     packed[key] = that._pack_models(sub_value);
                 });
                 return packed;
 
             } else {
                 return value;
             }
         },
 
         _unpack_models: function(value) {
             // Replace model ids with models recursively.
             var that = this;
             var unpacked;
             if ($.isArray(value)) {
                 unpacked = [];
                 _.each(value, function(sub_value, key) {
                     unpacked.push(that._unpack_models(sub_value));
                 });
                 return unpacked;
 
             } else if (value instanceof Object) {
                 unpacked = {};
                 _.each(value, function(sub_value, key) {
                     unpacked[key] = that._unpack_models(sub_value);
                 });
                 return unpacked;
 
             } else if (typeof value === 'string' && value.slice(0,10) === "IPY_MODEL_") {
                 var model = this.widget_manager.get_model(value.slice(10, value.length));
                 if (model) {
                     return model;
                 } else {
                     return value;
                 }
             } else {
                     return value;
             }
         },
 
         on_some_change: function(keys, callback, context) {
             // on_some_change(["key1", "key2"], foo, context) differs from
             // on("change:key1 change:key2", foo, context).
             // If the widget attributes key1 and key2 are both modified, 
             // the second form will result in foo being called twice
             // while the first will call foo only once.
             this.on('change', function() {
                 if (keys.some(this.hasChanged, this)) {
                     callback.apply(context);
                 }
             }, this);
 
        },
     });
     widgetmanager.WidgetManager.register_widget_model('WidgetModel', WidgetModel);
 
 
     var WidgetView = Backbone.View.extend({
         initialize: function(parameters) {
             // Public constructor.
             this.model.on('change',this.update,this);
             this.options = parameters.options;
             this.child_model_views = {};
             this.child_views = {};
             this.id = this.id || IPython.utils.uuid();
             this.model.views[this.id] = this;
             this.on('displayed', function() { 
                 this.is_displayed = true; 
             }, this);
         },
 
         update: function(){
             // Triggered on model change.
             //
             // Update view to be consistent with this.model
         },
 
         create_child_view: function(child_model, options) {
             // Create and return a child view.
             //
             // -given a model and (optionally) a view name if the view name is 
             // not given, it defaults to the model's default view attribute.
         
             // TODO: this is hacky, and makes the view depend on this cell attribute and widget manager behavior
             // it would be great to have the widget manager add the cell metadata
             // to the subview without having to add it here.
-            options = $.extend({ parent: this }, options || {});
-            var child_view = this.model.widget_manager.create_view(child_model, options, this);
-            
-            // Associate the view id with the model id.
-            if (this.child_model_views[child_model.id] === undefined) {
-                this.child_model_views[child_model.id] = [];
-            }
-            this.child_model_views[child_model.id].push(child_view.id);
+            var that = this;
+            var old_callback = options.callback || function(view) {};
+            options = $.extend({ parent: this, callback: function(child_view) {
+                // Associate the view id with the model id.
+                if (that.child_model_views[child_model.id] === undefined) {
+                    that.child_model_views[child_model.id] = [];
+                }
+                that.child_model_views[child_model.id].push(child_view.id);
 
-            // Remember the view by id.
-            this.child_views[child_view.id] = child_view;
-            return child_view;
+                // Remember the view by id.
+                that.child_views[child_view.id] = child_view;
+                old_callback(child_view);
+             }}, options || {});
+            
+            this.model.widget_manager.create_view(child_model, options);
         },
 
         pop_child_view: function(child_model) {
             // Delete a child view that was previously created using create_child_view.
             var view_ids = this.child_model_views[child_model.id];
             if (view_ids !== undefined) {
 
                 // Only delete the first view in the list.
                 var view_id = view_ids[0];
                 var view = this.child_views[view_id];
                 delete this.child_views[view_id];
                 view_ids.splice(0,1);
                 delete child_model.views[view_id];
             
                 // Remove the view list specific to this model if it is empty.
                 if (view_ids.length === 0) {
                     delete this.child_model_views[child_model.id];
                 }
                 return view;
             }
             return null;
         },
 
         do_diff: function(old_list, new_list, removed_callback, added_callback) {
             // Difference a changed list and call remove and add callbacks for 
             // each removed and added item in the new list.
             //
             // Parameters
             // ----------
             // old_list : array
             // new_list : array
             // removed_callback : Callback(item)
             //      Callback that is called for each item removed.
             // added_callback : Callback(item)
             //      Callback that is called for each item added.
 
             // Walk the lists until an unequal entry is found.
             var i;
             for (i = 0; i < new_list.length; i++) {
                 if (i >= old_list.length || new_list[i] !== old_list[i]) {
                     break;
                 }
             }
 
             // Remove the non-matching items from the old list.
             for (var j = i; j < old_list.length; j++) {
                 removed_callback(old_list[j]);
             }
 
             // Add the rest of the new list items.
             for (; i < new_list.length; i++) {
                 added_callback(new_list[i]);
             }
         },
 
         callbacks: function(){
             // Create msg callbacks for a comm msg.
             return this.model.callbacks(this);
         },
 
         render: function(){
             // Render the view.
             //
             // By default, this is only called the first time the view is created
         },
 
         show: function(){
             // Show the widget-area
             if (this.options && this.options.cell &&
                 this.options.cell.widget_area !== undefined) {
                 this.options.cell.widget_area.show();
             }
         },
 
         send: function (content) {
             // Send a custom msg associated with this view.
             this.model.send(content, this.callbacks());
         },
 
         touch: function () {
             this.model.save_changes(this.callbacks());
         },
 
         after_displayed: function (callback, context) {
             // Calls the callback right away is the view is already displayed
             // otherwise, register the callback to the 'displayed' event.
             if (this.is_displayed) {
                 callback.apply(context);
             } else {
                 this.on('displayed', callback, context);
             }
         },
     });
 
 
     var DOMWidgetView = WidgetView.extend({
         initialize: function (parameters) {
             // Public constructor
             DOMWidgetView.__super__.initialize.apply(this, [parameters]);
             this.on('displayed', this.show, this);
             this.model.on('change:visible', this.update_visible, this);
             this.model.on('change:_css', this.update_css, this);
 
             this.model.on('change:_dom_classes', function(model, new_classes) {
                 var old_classes = model.previous('_dom_classes');
                 this.update_classes(old_classes, new_classes);
             }, this);
 
             this.model.on('change:color', function (model, value) { 
                 this.update_attr('color', value); }, this);
 
             this.model.on('change:background_color', function (model, value) { 
                 this.update_attr('background', value); }, this);
 
             this.model.on('change:width', function (model, value) { 
                 this.update_attr('width', value); }, this);
 
             this.model.on('change:height', function (model, value) { 
                 this.update_attr('height', value); }, this);
 
             this.model.on('change:border_color', function (model, value) { 
                 this.update_attr('border-color', value); }, this);
 
             this.model.on('change:border_width', function (model, value) { 
                 this.update_attr('border-width', value); }, this);
 
             this.model.on('change:border_style', function (model, value) { 
                 this.update_attr('border-style', value); }, this);
 
             this.model.on('change:font_style', function (model, value) { 
                 this.update_attr('font-style', value); }, this);
 
             this.model.on('change:font_weight', function (model, value) { 
                 this.update_attr('font-weight', value); }, this);
 
             this.model.on('change:font_size', function (model, value) { 
                 this.update_attr('font-size', this._default_px(value)); }, this);
 
             this.model.on('change:font_family', function (model, value) { 
                 this.update_attr('font-family', value); }, this);
 
             this.model.on('change:padding', function (model, value) { 
                 this.update_attr('padding', value); }, this);
 
             this.model.on('change:margin', function (model, value) { 
                 this.update_attr('margin', this._default_px(value)); }, this);
 
             this.model.on('change:border_radius', function (model, value) { 
                 this.update_attr('border-radius', this._default_px(value)); }, this);
 
             this.after_displayed(function() {
                 this.update_visible(this.model, this.model.get("visible"));
                 this.update_classes([], this.model.get('_dom_classes'));
                 
                 this.update_attr('color', this.model.get('color'));
                 this.update_attr('background', this.model.get('background_color'));
                 this.update_attr('width', this.model.get('width'));
                 this.update_attr('height', this.model.get('height'));
                 this.update_attr('border-color', this.model.get('border_color'));
                 this.update_attr('border-width', this.model.get('border_width'));
                 this.update_attr('border-style', this.model.get('border_style'));
                 this.update_attr('font-style', this.model.get('font_style'));
                 this.update_attr('font-weight', this.model.get('font_weight'));
                 this.update_attr('font-size', this.model.get('font_size'));
                 this.update_attr('font-family', this.model.get('font_family'));
                 this.update_attr('padding', this.model.get('padding'));
                 this.update_attr('margin', this.model.get('margin'));
                 this.update_attr('border-radius', this.model.get('border_radius'));
 
                 this.update_css(this.model, this.model.get("_css"));
             }, this);
         },
 
         _default_px: function(value) {
             // Makes browser interpret a numerical string as a pixel value.
             if (/^\d+\.?(\d+)?$/.test(value.trim())) {
                 return value.trim() + 'px';
             }
             return value;
         },
 
         update_attr: function(name, value) {
             // Set a css attr of the widget view.
             this.$el.css(name, value);
         },
 
         update_visible: function(model, value) {
             // Update visibility
             this.$el.toggle(value);
          },
 
         update_css: function (model, css) {
             // Update the css styling of this view.
             var e = this.$el;
             if (css === undefined) {return;}
             for (var i = 0; i < css.length; i++) {
                 // Apply the css traits to all elements that match the selector.
                 var selector = css[i][0];
                 var elements = this._get_selector_element(selector);
                 if (elements.length > 0) {
                     var trait_key = css[i][1];
                     var trait_value = css[i][2];
                     elements.css(trait_key ,trait_value);
                 }
             }
         },
 
         update_classes: function (old_classes, new_classes, $el) {
             // Update the DOM classes applied to an element, default to this.$el.
             if ($el===undefined) {
                 $el = this.$el;
             }
             this.do_diff(old_classes, new_classes, function(removed) {
                 $el.removeClass(removed);
             }, function(added) {
                 $el.addClass(added);
             });
         },
 
         update_mapped_classes: function(class_map, trait_name, previous_trait_value, $el) {
             // Update the DOM classes applied to the widget based on a single
             // trait's value.
             //
             // Given a trait value classes map, this function automatically
             // handles applying the appropriate classes to the widget element
             // and removing classes that are no longer valid.
             //
             // Parameters
             // ----------
             // class_map: dictionary
             //  Dictionary of trait values to class lists.
             //  Example:
             //      {
             //          success: ['alert', 'alert-success'],
             //          info: ['alert', 'alert-info'],
             //          warning: ['alert', 'alert-warning'],
             //          danger: ['alert', 'alert-danger']
             //      };
             // trait_name: string
             //  Name of the trait to check the value of.
             // previous_trait_value: optional string, default ''
             //  Last trait value
             // $el: optional jQuery element handle, defaults to this.$el
             //  Element that the classes are applied to.
             var key = previous_trait_value;
             if (key === undefined) {
                 key = this.model.previous(trait_name);
             }
             var old_classes = class_map[key] ? class_map[key] : [];
             key = this.model.get(trait_name);
             var new_classes = class_map[key] ? class_map[key] : [];
 
             this.update_classes(old_classes, new_classes, $el || this.$el);
         },
         
         _get_selector_element: function (selector) {
             // Get the elements via the css selector.
             var elements;
             if (!selector) {
                 elements = this.$el;
             } else {
                 elements = this.$el.find(selector).addBack(selector);
             }
             return elements;
         },
     });
 
     
     var widget = {
         'WidgetModel': WidgetModel,
         'WidgetView': WidgetView,
         'DOMWidgetView': DOMWidgetView,
     };
 
     // For backwards compatability.
     $.extend(IPython, widget);
 
     return widget;
 });

IPython/html/static/widgets/js/widget_box.js

@@ -1,344 +1,346 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     "widgets/js/widget",
     "jqueryui",
     "bootstrap",
 ], function(widget, $){
 
     var BoxView = widget.DOMWidgetView.extend({
         initialize: function(){
             // Public constructor
             BoxView.__super__.initialize.apply(this, arguments);
             this.model.on('change:children', function(model, value) {
                 this.update_children(model.previous('children'), value);
             }, this);
             this.model.on('change:overflow_x', function(model, value) {
                 this.update_overflow_x();
             }, this);
             this.model.on('change:overflow_y', function(model, value) {
                 this.update_overflow_y();
             }, this);
             this.model.on('change:box_style', function(model, value) {
                 this.update_box_style();
             }, this);
         },
 
         update_attr: function(name, value) {
             // Set a css attr of the widget view.
             this.$box.css(name, value);
         },
 
         render: function(){
             // Called when view is rendered.
             this.$box = this.$el;
             this.$box.addClass('widget-box');
             this.update_children([], this.model.get('children'));
             this.update_overflow_x();
             this.update_overflow_y();
             this.update_box_style('');
         },
 
         update_overflow_x: function() {
             // Called when the x-axis overflow setting is changed.
             this.$box.css('overflow-x', this.model.get('overflow_x'));
         },
 
         update_overflow_y: function() {
             // Called when the y-axis overflow setting is changed.
             this.$box.css('overflow-y', this.model.get('overflow_y'));
         },
 
         update_box_style: function(previous_trait_value) {
             var class_map = {
                 success: ['alert', 'alert-success'],
                 info: ['alert', 'alert-info'],
                 warning: ['alert', 'alert-warning'],
                 danger: ['alert', 'alert-danger']
             };
             this.update_mapped_classes(class_map, 'box_style', previous_trait_value, this.$box);
         },
         
         update_children: function(old_list, new_list) {
             // Called when the children list changes.
             this.do_diff(old_list, new_list, 
                 $.proxy(this.remove_child_model, this),
                 $.proxy(this.add_child_model, this));
         },
 
         remove_child_model: function(model) {
             // Called when a model is removed from the children list.
             this.pop_child_view(model).remove();
         },
 
         add_child_model: function(model) {
             // Called when a model is added to the children list.
-            var view = this.create_child_view(model);
-            this.$box.append(view.$el);
+            var that = this;
+            this.create_child_view(model, {callback: function(view) {
+                that.$box.append(view.$el);
 
-            // Trigger the displayed event of the child view.
-            this.after_displayed(function() {
-                view.trigger('displayed');
-            });
+                // Trigger the displayed event of the child view.
+                that.after_displayed(function() {
+                    view.trigger('displayed');
+                });
+            }});
         },
     });
 
 
     var FlexBoxView = BoxView.extend({
         render: function(){
             FlexBoxView.__super__.render.apply(this);
             this.model.on('change:orientation', this.update_orientation, this);
             this.model.on('change:flex', this._flex_changed, this);
             this.model.on('change:pack', this._pack_changed, this);
             this.model.on('change:align', this._align_changed, this);
             this._flex_changed();
             this._pack_changed();
             this._align_changed();
             this.update_orientation();
         },
 
         update_orientation: function(){
             var orientation = this.model.get("orientation");
             if (orientation == "vertical") {
                 this.$box.removeClass("hbox").addClass("vbox");
             } else {
                 this.$box.removeClass("vbox").addClass("hbox");
             }
         },
 
         _flex_changed: function(){
             if (this.model.previous('flex')) {
                 this.$box.removeClass('box-flex' + this.model.previous('flex'));
             }
             this.$box.addClass('box-flex' + this.model.get('flex'));
         },
 
         _pack_changed: function(){
             if (this.model.previous('pack')) {
                 this.$box.removeClass(this.model.previous('pack'));
             }
             this.$box.addClass(this.model.get('pack'));
         },
 
         _align_changed: function(){
             if (this.model.previous('align')) {
                 this.$box.removeClass('align-' + this.model.previous('align'));
             }
             this.$box.addClass('align-' + this.model.get('align'));
         },
     });
 
     var PopupView = BoxView.extend({
 
         render: function(){
             // Called when view is rendered.
             var that = this;
             
             this.$el.on("remove", function(){
                     that.$backdrop.remove();
                 });
             this.$backdrop = $('<div />')
                 .appendTo($('#notebook-container'))
                 .addClass('modal-dialog')
                 .css('position', 'absolute')
                 .css('left', '0px')
                 .css('top', '0px');
             this.$window = $('<div />')
                 .appendTo(this.$backdrop)
                 .addClass('modal-content widget-modal')
                 .mousedown(function(){
                     that.bring_to_front();
                 });
 
             // Set the elements array since the this.$window element is not child
             // of this.$el and the parent widget manager or other widgets may
             // need to know about all of the top-level widgets.  The IPython
             // widget manager uses this to register the elements with the
             // keyboard manager.
             this.additional_elements = [this.$window];
 
             this.$title_bar = $('<div />')
                 .addClass('popover-title')
                 .appendTo(this.$window)
                 .mousedown(function(){
                     that.bring_to_front();
                 });
             this.$close = $('<button />')
                 .addClass('close fa fa-remove')
                 .css('margin-left', '5px')
                 .appendTo(this.$title_bar)
                 .click(function(){
                     that.hide();
                     event.stopPropagation();
                 });
             this.$minimize = $('<button />')
                 .addClass('close fa fa-arrow-down')
                 .appendTo(this.$title_bar)
                 .click(function(){
                     that.popped_out = !that.popped_out;
                     if (!that.popped_out) {
                         that.$minimize
                             .removeClass('fa-arrow-down')
                             .addClass('fa-arrow-up');
                             
                         that.$window
                             .draggable('destroy')
                             .resizable('destroy')
                             .removeClass('widget-modal modal-content')
                             .addClass('docked-widget-modal')
                             .detach()
                             .insertBefore(that.$show_button);
                         that.$show_button.hide();
                         that.$close.hide();
                     } else {
                         that.$minimize
                             .addClass('fa-arrow-down')
                             .removeClass('fa-arrow-up');
 
                         that.$window
                             .removeClass('docked-widget-modal')
                             .addClass('widget-modal modal-content')
                             .detach()
                             .appendTo(that.$backdrop)
                             .draggable({handle: '.popover-title', snap: '#notebook, .modal', snapMode: 'both'})
                             .resizable()
                             .children('.ui-resizable-handle').show();
                         that.show();
                         that.$show_button.show();
                         that.$close.show();
                     }
                     event.stopPropagation();
                 });
             this.$title = $('<div />')
                 .addClass('widget-modal-title')
                 .html("&nbsp;")
                 .appendTo(this.$title_bar);     
             this.$box = $('<div />')
                 .addClass('modal-body')
                 .addClass('widget-modal-body')
                 .addClass('widget-box')
                 .addClass('vbox')
                 .appendTo(this.$window);
             
             this.$show_button = $('<button />')
                 .html("&nbsp;")
                 .addClass('btn btn-info widget-modal-show')
                 .appendTo(this.$el)
                 .click(function(){
                     that.show();
                 });
             
             this.$window.draggable({handle: '.popover-title', snap: '#notebook, .modal', snapMode: 'both'});
             this.$window.resizable();
             this.$window.on('resize', function(){
                 that.$box.outerHeight(that.$window.innerHeight() - that.$title_bar.outerHeight());
             });
 
             this._shown_once = false;
             this.popped_out = true;
 
             this.update_children([], this.model.get('children'));
             this.model.on('change:children', function(model, value) {
                 this.update_children(model.previous('children'), value);
             }, this);
         },
         
         hide: function() {
             // Called when the modal hide button is clicked.
             this.$window.hide();
             this.$show_button.removeClass('btn-info');
         },
         
         show: function() {
             // Called when the modal show button is clicked.
             this.$show_button.addClass('btn-info');
             this.$window.show();
             if (this.popped_out) {
                 this.$window.css("positon", "absolute");
                 this.$window.css("top", "0px");
                 this.$window.css("left", Math.max(0, (($('body').outerWidth() - this.$window.outerWidth()) / 2) + 
                     $(window).scrollLeft()) + "px");
                 this.bring_to_front();
             }
         },
         
         bring_to_front: function() {
             // Make the modal top-most, z-ordered about the other modals.
             var $widget_modals = $(".widget-modal");
             var max_zindex = 0;
             $widget_modals.each(function (index, el){
                 var zindex = parseInt($(el).css('z-index'));
                 if (!isNaN(zindex)) {
                     max_zindex = Math.max(max_zindex, zindex);
                 }
             });
             
             // Start z-index of widget modals at 2000
             max_zindex = Math.max(max_zindex, 2000);
             
             $widget_modals.each(function (index, el){
                 $el = $(el);
                 if (max_zindex == parseInt($el.css('z-index'))) {
                     $el.css('z-index', max_zindex - 1);
                 }
             });
             this.$window.css('z-index', max_zindex);
         },
         
         update: function(){
             // Update the contents of this view
             //
             // Called when the model is changed.  The model may have been 
             // changed by another view or by a state update from the back-end.
             var description = this.model.get('description');
             if (description.trim().length === 0) {
                 this.$title.html("&nbsp;"); // Preserve title height
             } else {
                 this.$title.text(description);
                 MathJax.Hub.Queue(["Typeset",MathJax.Hub,this.$title.get(0)]);
             }
             
             var button_text = this.model.get('button_text');
             if (button_text.trim().length === 0) {
                 this.$show_button.html("&nbsp;"); // Preserve button height
             } else {
                 this.$show_button.text(button_text);
             }
             
             if (!this._shown_once) {
                 this._shown_once = true;
                 this.show();
             }
             
             return PopupView.__super__.update.apply(this);
         },
         
         _get_selector_element: function(selector) {
             // Get an element view a 'special' jquery selector.  (see widget.js)
             //
             // Since the modal actually isn't within the $el in the DOM, we need to extend
             // the selector logic to allow the user to set css on the modal if need be.
             // The convention used is:
             // "modal" - select the modal div
             // "modal [selector]" - select element(s) within the modal div.
             // "[selector]" - select elements within $el
             // "" - select the $el
             if (selector.substring(0, 5) == 'modal') {
                 if (selector == 'modal') {
                     return this.$window;
                 } else {
                     return this.$window.find(selector.substring(6));
                 }
             } else {
                 return PopupView.__super__._get_selector_element.apply(this, [selector]);
             }
         },
     });
 
     return {
         'BoxView': BoxView,
         'PopupView': PopupView,
         'FlexBoxView': FlexBoxView,
     };
 });

IPython/html/static/widgets/js/widget_selectioncontainer.js

@@ -1,253 +1,257 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     "widgets/js/widget",
     "base/js/utils",
     "jquery",
     "bootstrap",
 ], function(widget, utils, $){
 
     var AccordionView = widget.DOMWidgetView.extend({
         render: function(){
             // Called when view is rendered.
             var guid = 'panel-group' + utils.uuid();
             this.$el
                 .attr('id', guid)
                 .addClass('panel-group');
             this.containers = [];
             this.model_containers = {};
             this.update_children([], this.model.get('children'));
             this.model.on('change:children', function(model, value, options) {
                 this.update_children(model.previous('children'), value);
             }, this);
             this.model.on('change:selected_index', function(model, value, options) {
                 this.update_selected_index(model.previous('selected_index'), value, options);
             }, this);
             this.model.on('change:_titles', function(model, value, options) {
                 this.update_titles(value);
             }, this);
             var that = this;
             this.on('displayed', function() {
                 this.update_titles();
             }, this);
         },
 
         update_titles: function(titles) {
             // Set tab titles
             if (!titles) {
                 titles = this.model.get('_titles');
             }
 
             var that = this;
             _.each(titles, function(title, page_index) {
                 var accordian = that.containers[page_index];
                 if (accordian !== undefined) {
                     accordian
                         .find('.panel-heading')
                         .find('.accordion-toggle')
                         .text(title);
                 }
             });
         },
 
         update_selected_index: function(old_index, new_index, options) {
             // Only update the selection if the selection wasn't triggered
             // by the front-end.  It must be triggered by the back-end.
             if (options === undefined || options.updated_view != this) {
                 this.containers[old_index].find('.panel-collapse').collapse('hide');
                 if (0 <= new_index && new_index < this.containers.length) {
                     this.containers[new_index].find('.panel-collapse').collapse('show');
                 }
             }
         },
         
         update_children: function(old_list, new_list) {
             // Called when the children list is modified.
             this.do_diff(old_list, 
                 new_list, 
                 $.proxy(this.remove_child_model, this),
                 $.proxy(this.add_child_model, this));
         },
 
         remove_child_model: function(model) {
             // Called when a child is removed from children list.
             var accordion_group = this.model_containers[model.id];
             this.containers.splice(accordion_group.container_index, 1);
             delete this.model_containers[model.id];
             accordion_group.remove();
             this.pop_child_view(model);
         },
 
         add_child_model: function(model) {
             // Called when a child is added to children list.
-            var view = this.create_child_view(model);
             var index = this.containers.length;
             var uuid = utils.uuid();
             var accordion_group = $('<div />')
                 .addClass('panel panel-default')
                 .appendTo(this.$el);
             var accordion_heading = $('<div />')
                 .addClass('panel-heading')
                 .appendTo(accordion_group);
             var that = this;
             var accordion_toggle = $('<a />')
                 .addClass('accordion-toggle')
                 .attr('data-toggle', 'collapse')
                 .attr('data-parent', '#' + this.$el.attr('id'))
                 .attr('href', '#' + uuid)
                 .click(function(evt){ 
             
                     // Calling model.set will trigger all of the other views of the 
                     // model to update.
                     that.model.set("selected_index", index, {updated_view: that});
                     that.touch();
                  })
                 .text('Page ' + index)
                 .appendTo(accordion_heading);
             var accordion_body = $('<div />', {id: uuid})
                 .addClass('panel-collapse collapse')
                 .appendTo(accordion_group);
             var accordion_inner = $('<div />')
                 .addClass('panel-body')
                 .appendTo(accordion_body);
             var container_index = this.containers.push(accordion_group) - 1;
             accordion_group.container_index = container_index;
             this.model_containers[model.id] = accordion_group;
-            accordion_inner.append(view.$el);
+            
+            this.create_child_view(model, {callback: function(view) {
+                accordion_inner.append(view.$el);
 
-            this.update();
-            this.update_titles();
+                that.update();
+                that.update_titles();
 
-            // Trigger the displayed event of the child view.
-            this.after_displayed(function() {
-                view.trigger('displayed');
-            });
+                // Trigger the displayed event of the child view.
+                that.after_displayed(function() {
+                    view.trigger('displayed');
+                });
+            }});
         },
     });
     
 
     var TabView = widget.DOMWidgetView.extend({    
         initialize: function() {
             // Public constructor.
             this.containers = [];
             TabView.__super__.initialize.apply(this, arguments);
         },
 
         render: function(){
             // Called when view is rendered.
             var uuid = 'tabs'+utils.uuid();
             var that = this;
             this.$tabs = $('<div />', {id: uuid})
                 .addClass('nav')
                 .addClass('nav-tabs')
                 .appendTo(this.$el);
             this.$tab_contents = $('<div />', {id: uuid + 'Content'})
                 .addClass('tab-content')
                 .appendTo(this.$el);
             this.containers = [];
             this.update_children([], this.model.get('children'));
             this.model.on('change:children', function(model, value, options) {
                 this.update_children(model.previous('children'), value);
             }, this);
         },
 
         update_attr: function(name, value) {
             // Set a css attr of the widget view.
             this.$tabs.css(name, value);
         },
 
         update_children: function(old_list, new_list) {
             // Called when the children list is modified.
             this.do_diff(old_list, 
                 new_list, 
                 $.proxy(this.remove_child_model, this),
                 $.proxy(this.add_child_model, this));
         },
 
         remove_child_model: function(model) {
             // Called when a child is removed from children list.
             var view = this.pop_child_view(model);
             this.containers.splice(view.parent_tab.tab_text_index, 1);
             view.parent_tab.remove();
             view.parent_container.remove();
             view.remove();
         },
 
         add_child_model: function(model) {
             // Called when a child is added to children list.
-            var view = this.create_child_view(model);
             var index = this.containers.length;
             var uuid = utils.uuid();
 
             var that = this;
             var tab = $('<li />')
                 .css('list-style-type', 'none')
                 .appendTo(this.$tabs);
-            view.parent_tab = tab;
-
-            var tab_text = $('<a />')
-                .attr('href', '#' + uuid)
-                .attr('data-toggle', 'tab') 
-                .text('Page ' + index)
-                .appendTo(tab)
-                .click(function (e) {
             
-                    // Calling model.set will trigger all of the other views of the 
-                    // model to update.
-                    that.model.set("selected_index", index, {updated_view: this});
-                    that.touch();
-                    that.select_page(index);
+            this.create_child_view(model, {callback: function(view) {
+                view.parent_tab = tab;
+
+                var tab_text = $('<a />')
+                    .attr('href', '#' + uuid)
+                    .attr('data-toggle', 'tab') 
+                    .text('Page ' + index)
+                    .appendTo(tab)
+                    .click(function (e) {
+                
+                        // Calling model.set will trigger all of the other views of the 
+                        // model to update.
+                        that.model.set("selected_index", index, {updated_view: that});
+                        that.touch();
+                        that.select_page(index);
+                    });
+                tab.tab_text_index = that.containers.push(tab_text) - 1;
+
+                var contents_div = $('<div />', {id: uuid})
+                    .addClass('tab-pane')
+                    .addClass('fade')
+                    .append(view.$el)
+                    .appendTo(that.$tab_contents);
+                view.parent_container = contents_div;
+
+                // Trigger the displayed event of the child view.
+                that.after_displayed(function() {
+                    view.trigger('displayed');
                 });
-            tab.tab_text_index = this.containers.push(tab_text) - 1;
-
-            var contents_div = $('<div />', {id: uuid})
-                .addClass('tab-pane')
-                .addClass('fade')
-                .append(view.$el)
-                .appendTo(this.$tab_contents);
-            view.parent_container = contents_div;
-
-            // Trigger the displayed event of the child view.
-            this.after_displayed(function() {
-                view.trigger('displayed');
-            });
+            }});
         },
 
         update: function(options) {
             // Update the contents of this view
             //
             // Called when the model is changed.  The model may have been 
             // changed by another view or by a state update from the back-end.
             if (options === undefined || options.updated_view != this) {
                 // Set tab titles
                 var titles = this.model.get('_titles');
                 var that = this;
                 _.each(titles, function(title, page_index) {
                    var tab_text = that.containers[page_index];
                     if (tab_text !== undefined) {
                         tab_text.text(title);
                     } 
                 });
 
                 var selected_index = this.model.get('selected_index');
                 if (0 <= selected_index && selected_index < this.containers.length) {
                     this.select_page(selected_index);
                 }
             }
             return TabView.__super__.update.apply(this);
         },
 
         select_page: function(index) {
             // Select a page.
             this.$tabs.find('li')
                 .removeClass('active');
             this.containers[index].tab('show');
         },
     });
 
     return {
         'AccordionView': AccordionView,
         'TabView': TabView,
     };
 });

IPython/html/widgets/widget.py

@@ -1,448 +1,450 b''
 """Base Widget class.  Allows user to create widgets in the back-end that render
 in the IPython notebook front-end.
 """
 #-----------------------------------------------------------------------------
 # Copyright (c) 2013, the IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 from contextlib import contextmanager
 import collections
 
 from IPython.core.getipython import get_ipython
 from IPython.kernel.comm import Comm
 from IPython.config import LoggingConfigurable
 from IPython.utils.traitlets import Unicode, Dict, Instance, Bool, List, \
     CaselessStrEnum, Tuple, CUnicode, Int, Set
 from IPython.utils.py3compat import string_types
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 class CallbackDispatcher(LoggingConfigurable):
     """A structure for registering and running callbacks"""
     callbacks = List()
     
     def __call__(self, *args, **kwargs):
         """Call all of the registered callbacks."""
         value = None
         for callback in self.callbacks:
             try:
                 local_value = callback(*args, **kwargs)
             except Exception as e:
                 ip = get_ipython()
                 if ip is None:
                     self.log.warn("Exception in callback %s: %s", callback, e, exc_info=True)
                 else:
                     ip.showtraceback()
             else:
                 value = local_value if local_value is not None else value
         return value
 
     def register_callback(self, callback, remove=False):
         """(Un)Register a callback
 
         Parameters
         ----------
         callback: method handle
             Method to be registered or unregistered.
         remove=False: bool
             Whether to unregister the callback."""
         
         # (Un)Register the callback.
         if remove and callback in self.callbacks:
             self.callbacks.remove(callback)
         elif not remove and callback not in self.callbacks:
             self.callbacks.append(callback)
 
 def _show_traceback(method):
     """decorator for showing tracebacks in IPython"""
     def m(self, *args, **kwargs):
         try:
             return(method(self, *args, **kwargs))
         except Exception as e:
             ip = get_ipython()
             if ip is None:
                 self.log.warn("Exception in widget method %s: %s", method, e, exc_info=True)
             else:
                 ip.showtraceback()
     return m
 
 class Widget(LoggingConfigurable):
     #-------------------------------------------------------------------------
     # Class attributes
     #-------------------------------------------------------------------------
     _widget_construction_callback = None
     widgets = {}
 
     @staticmethod
     def on_widget_constructed(callback):
         """Registers a callback to be called when a widget is constructed.
 
         The callback must have the following signature:
         callback(widget)"""
         Widget._widget_construction_callback = callback
 
     @staticmethod
     def _call_widget_constructed(widget):
         """Static method, called when a widget is constructed."""
         if Widget._widget_construction_callback is not None and callable(Widget._widget_construction_callback):
             Widget._widget_construction_callback(widget)
 
     #-------------------------------------------------------------------------
     # Traits
     #-------------------------------------------------------------------------
     _model_name = Unicode('WidgetModel', help="""Name of the backbone model 
         registered in the front-end to create and sync this widget with.""")
+    _view_module = Unicode(help="""A requirejs module in which to find _view_name.
+        If empty, look in the global registry.""", sync=True)
     _view_name = Unicode(None, allow_none=True, help="""Default view registered in the front-end
         to use to represent the widget.""", sync=True)
     comm = Instance('IPython.kernel.comm.Comm')
     
     msg_throttle = Int(3, sync=True, help="""Maximum number of msgs the 
         front-end can send before receiving an idle msg from the back-end.""")
     
     version = Int(0, sync=True, help="""Widget's version""")
     keys = List()
     def _keys_default(self):
         return [name for name in self.traits(sync=True)]
     
     _property_lock = Tuple((None, None))
     _send_state_lock = Int(0)
     _states_to_send = Set(allow_none=False)
     _display_callbacks = Instance(CallbackDispatcher, ())
     _msg_callbacks = Instance(CallbackDispatcher, ())
     
     #-------------------------------------------------------------------------
     # (Con/de)structor
     #-------------------------------------------------------------------------
     def __init__(self, **kwargs):
         """Public constructor"""
         self._model_id = kwargs.pop('model_id', None)
         super(Widget, self).__init__(**kwargs)
 
         Widget._call_widget_constructed(self)
         self.open()
 
     def __del__(self):
         """Object disposal"""
         self.close()
 
     #-------------------------------------------------------------------------
     # Properties
     #-------------------------------------------------------------------------
 
     def open(self):
         """Open a comm to the frontend if one isn't already open."""
         if self.comm is None:
             args = dict(target_name='ipython.widget', data={ 'model_name': self._model_name })
             if self._model_id is not None:
                 args['comm_id'] = self._model_id
             self.comm = Comm(**args)
             self._model_id = self.model_id
             
             self.comm.on_msg(self._handle_msg)
             Widget.widgets[self.model_id] = self
 
             # first update
             self.send_state()
 
     @property
     def model_id(self):
         """Gets the model id of this widget.
 
         If a Comm doesn't exist yet, a Comm will be created automagically."""
         return self.comm.comm_id
 
     #-------------------------------------------------------------------------
     # Methods
     #-------------------------------------------------------------------------
 
     def close(self):
         """Close method.
 
         Closes the underlying comm.
         When the comm is closed, all of the widget views are automatically
         removed from the front-end."""
         if self.comm is not None:
             Widget.widgets.pop(self.model_id, None)
             self.comm.close()
             self.comm = None
     
     def send_state(self, key=None):
         """Sends the widget state, or a piece of it, to the front-end.
 
         Parameters
         ----------
         key : unicode, or iterable (optional)
             A single property's name or iterable of property names to sync with the front-end.
         """
         self._send({
             "method" : "update",
             "state"  : self.get_state(key=key)
         })
 
     def get_state(self, key=None):
         """Gets the widget state, or a piece of it.
 
         Parameters
         ----------
         key : unicode or iterable (optional)
             A single property's name or iterable of property names to get.
         """
         if key is None:
             keys = self.keys
         elif isinstance(key, string_types):
             keys = [key]
         elif isinstance(key, collections.Iterable):
             keys = key
         else:
             raise ValueError("key must be a string, an iterable of keys, or None")
         state = {}
         for k in keys:
             f = self.trait_metadata(k, 'to_json', self._trait_to_json)
             value = getattr(self, k)
             state[k] = f(value)
         return state
 
     def set_state(self, sync_data):
         """Called when a state is received from the front-end."""
         for name in self.keys:
             if name in sync_data:
                 json_value = sync_data[name]
                 from_json = self.trait_metadata(name, 'from_json', self._trait_from_json)
                 with self._lock_property(name, json_value):
                     setattr(self, name, from_json(json_value))
     
     def send(self, content):
         """Sends a custom msg to the widget model in the front-end.
 
         Parameters
         ----------
         content : dict
             Content of the message to send.
         """
         self._send({"method": "custom", "content": content})
 
     def on_msg(self, callback, remove=False):
         """(Un)Register a custom msg receive callback.
 
         Parameters
         ----------
         callback: callable
             callback will be passed two arguments when a message arrives::
             
                 callback(widget, content)
             
         remove: bool
             True if the callback should be unregistered."""
         self._msg_callbacks.register_callback(callback, remove=remove)
 
     def on_displayed(self, callback, remove=False):
         """(Un)Register a widget displayed callback.
 
         Parameters
         ----------
         callback: method handler
             Must have a signature of::
             
                 callback(widget, **kwargs)
             
             kwargs from display are passed through without modification.
         remove: bool
             True if the callback should be unregistered."""
         self._display_callbacks.register_callback(callback, remove=remove)
 
     #-------------------------------------------------------------------------
     # Support methods
     #-------------------------------------------------------------------------
     @contextmanager
     def _lock_property(self, key, value):
         """Lock a property-value pair.
 
         The value should be the JSON state of the property.
 
         NOTE: This, in addition to the single lock for all state changes, is 
         flawed.  In the future we may want to look into buffering state changes 
         back to the front-end."""
         self._property_lock = (key, value)
         try:
             yield
         finally:
             self._property_lock = (None, None)
 
     @contextmanager
     def hold_sync(self):
         """Hold syncing any state until the context manager is released"""
         # We increment a value so that this can be nested.  Syncing will happen when
         # all levels have been released.
         self._send_state_lock += 1
         try:
             yield
         finally:
             self._send_state_lock -=1
             if self._send_state_lock == 0:
                 self.send_state(self._states_to_send)
                 self._states_to_send.clear()
 
     def _should_send_property(self, key, value):
         """Check the property lock (property_lock)"""
         to_json = self.trait_metadata(key, 'to_json', self._trait_to_json)
         if (key == self._property_lock[0]
             and to_json(value) == self._property_lock[1]):
             return False
         elif self._send_state_lock > 0:
             self._states_to_send.add(key)
             return False
         else:
             return True
     
     # Event handlers
     @_show_traceback
     def _handle_msg(self, msg):
         """Called when a msg is received from the front-end"""
         data = msg['content']['data']
         method = data['method']
         if not method in ['backbone', 'custom']:
             self.log.error('Unknown front-end to back-end widget msg with method "%s"' % method)
 
         # Handle backbone sync methods CREATE, PATCH, and UPDATE all in one.
         if method == 'backbone' and 'sync_data' in data:
             sync_data = data['sync_data']
             self.set_state(sync_data) # handles all methods
 
         # Handle a custom msg from the front-end
         elif method == 'custom':
             if 'content' in data:
                 self._handle_custom_msg(data['content'])
 
     def _handle_custom_msg(self, content):
         """Called when a custom msg is received."""
         self._msg_callbacks(self, content)
     
     def _notify_trait(self, name, old_value, new_value):
         """Called when a property has been changed."""
         # Trigger default traitlet callback machinery.  This allows any user
         # registered validation to be processed prior to allowing the widget
         # machinery to handle the state.
         LoggingConfigurable._notify_trait(self, name, old_value, new_value)
 
         # Send the state after the user registered callbacks for trait changes
         # have all fired (allows for user to validate values).
         if self.comm is not None and name in self.keys:
             # Make sure this isn't information that the front-end just sent us.
             if self._should_send_property(name, new_value):
                 # Send new state to front-end
                 self.send_state(key=name)
 
     def _handle_displayed(self, **kwargs):
         """Called when a view has been displayed for this widget instance"""
         self._display_callbacks(self, **kwargs)
 
     def _trait_to_json(self, x):
         """Convert a trait value to json
 
         Traverse lists/tuples and dicts and serialize their values as well.
         Replace any widgets with their model_id
         """
         if isinstance(x, dict):
             return {k: self._trait_to_json(v) for k, v in x.items()}
         elif isinstance(x, (list, tuple)):
             return [self._trait_to_json(v) for v in x]
         elif isinstance(x, Widget):
             return "IPY_MODEL_" + x.model_id
         else:
             return x # Value must be JSON-able
 
     def _trait_from_json(self, x):
         """Convert json values to objects
 
         Replace any strings representing valid model id values to Widget references.
         """
         if isinstance(x, dict):
             return {k: self._trait_from_json(v) for k, v in x.items()}
         elif isinstance(x, (list, tuple)):
             return [self._trait_from_json(v) for v in x]
         elif isinstance(x, string_types) and x.startswith('IPY_MODEL_') and x[10:] in Widget.widgets:
             # we want to support having child widgets at any level in a hierarchy
             # trusting that a widget UUID will not appear out in the wild
             return Widget.widgets[x[10:]]
         else:
             return x
 
     def _ipython_display_(self, **kwargs):
         """Called when `IPython.display.display` is called on the widget."""
         # Show view.
         if self._view_name is not None:
             self._send({"method": "display"})
             self._handle_displayed(**kwargs)
 
     def _send(self, msg):
         """Sends a message to the model in the front-end."""
         self.comm.send(msg)
 
 
 class DOMWidget(Widget):
     visible = Bool(True, help="Whether the widget is visible.", sync=True)
     _css = Tuple(sync=True, help="CSS property list: (selector, key, value)")
     _dom_classes = Tuple(sync=True, help="DOM classes applied to widget.$el.")
     
     width = CUnicode(sync=True)
     height = CUnicode(sync=True)
     padding = CUnicode(sync=True)
     margin = CUnicode(sync=True)
 
     color = Unicode(sync=True)
     background_color = Unicode(sync=True)
     border_color = Unicode(sync=True)
 
     border_width = CUnicode(sync=True)
     border_radius = CUnicode(sync=True)
     border_style = CaselessStrEnum(values=[ # http://www.w3schools.com/cssref/pr_border-style.asp
         'none', 
         'hidden', 
         'dotted', 
         'dashed', 
         'solid', 
         'double', 
         'groove', 
         'ridge', 
         'inset', 
         'outset', 
         'initial', 
         'inherit', ''],
         default_value='', sync=True)
 
     font_style = CaselessStrEnum(values=[ # http://www.w3schools.com/cssref/pr_font_font-style.asp
         'normal', 
         'italic', 
         'oblique', 
         'initial', 
         'inherit', ''], 
         default_value='', sync=True)
     font_weight = CaselessStrEnum(values=[ # http://www.w3schools.com/cssref/pr_font_weight.asp
         'normal', 
         'bold', 
         'bolder', 
         'lighter',
         'initial', 
         'inherit', ''] + [str(100 * (i+1)) for i in range(9)], 
         default_value='', sync=True)
     font_size = CUnicode(sync=True)
     font_family = Unicode(sync=True)
 
     def __init__(self, *pargs, **kwargs):
         super(DOMWidget, self).__init__(*pargs, **kwargs)
 
         def _validate_border(name, old, new):
             if new is not None and new != '':
                 if name != 'border_width' and not self.border_width:
                     self.border_width = 1
                 if name != 'border_style' and self.border_style == '':
                     self.border_style = 'solid'
         self.on_trait_change(_validate_border, ['border_width', 'border_style', 'border_color'])