load the per kernel kernel.js and kernel.css

As per discussion, each kernel can provide a file name kernel.js that
we try to load at kernel switching. If such a file exist we assume that
the kernel pathches the javasscript and that this javascript cannot be
unpatched, and further switching of the kernel cannot be undone without
reloading the page. (separate PR for UI)

if a kernel provide kernel.js, the it should consist into a AMD module
definition that uses require.js the module shoudl define a function name
`onload` that will be called at the appropriate moment before the kernel
starts.

IPython/html/static/notebook/js/kernelselector.js

@@ -1,111 +1,156 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     'base/js/namespace',
     'jquery',
     'base/js/utils',
 ], function(IPython, $, utils) {
     "use strict";
     
     var KernelSelector = function(selector, notebook) {
         this.selector = selector;
         this.notebook = notebook;
         this.events = notebook.events;
         this.current_selection = null;
         this.kernelspecs = {};
         if (this.selector !== undefined) {
             this.element = $(selector);
             this.request_kernelspecs();
         }
         this.bind_events();
         // Make the object globally available for user convenience & inspection
         IPython.kernelselector = this;
+        Object.seal(this);
     };
     
     KernelSelector.prototype.request_kernelspecs = function() {
         var url = utils.url_join_encode(this.notebook.base_url, 'api/kernelspecs');
         utils.promising_ajax(url).then($.proxy(this._got_kernelspecs, this));
     };
     
     KernelSelector.prototype._got_kernelspecs = function(data) {
         this.kernelspecs = data.kernelspecs;
         var menu = this.element.find("#kernel_selector");
         var change_kernel_submenu = $("#menu-change-kernel-submenu");
         var keys = Object.keys(data.kernelspecs).sort(function (a, b) {
             // sort by display_name
             var da = data.kernelspecs[a].display_name;
             var db = data.kernelspecs[b].display_name;
             if (da === db) {
                 return 0;
             } else if (da > db) {
                 return 1;
             } else {
                 return -1;
             }
         });
         for (var i = 0; i < keys.length; i++) {
             var ks = this.kernelspecs[keys[i]];
             var ksentry = $("<li>").attr("id", "kernel-" +ks.name).append($('<a>')
                 .attr('href', '#')
                 .click($.proxy(this.change_kernel, this, ks.name))
                 .text(ks.display_name));
             menu.append(ksentry);
 
             var ks_submenu_entry = $("<li>").attr("id", "kernel-submenu-"+ks.name).append($('<a>')
                 .attr('href', '#')
                 .click($.proxy(this.change_kernel, this, ks.name))
                 .text(ks.display_name));
             change_kernel_submenu.append(ks_submenu_entry);
         }
     };
 
     KernelSelector.prototype.change_kernel = function(kernel_name) {
+        /**
+         * TODO, have a methods to set kernel spec directly ?
+         **/
+        var that = this;
         if (kernel_name === this.current_selection) {
             return;
         }
         var ks = this.kernelspecs[kernel_name];
+        var new_mode_url = 'kernelspecs/'+ks.name+'/kernel';
+
+        var css_url = this.notebook.base_url+new_mode_url+'.css';
+        $.ajax({
+            type: 'HEAD',
+            url: css_url,
+            success: function(){
+                $('#kernel-css')
+                .attr('href',css_url);
+            },
+            error:function(){
+                console.warn(new_mode_url+' does not provide custom URL, you might see a 404 error that shoudl not prevent '+
+                                     ' the Jupyter notebook from working :' ,css_url );
+            }
+        });
+
         try {
             this.notebook.start_session(kernel_name);
         } catch (e) {
             if (e.name === 'SessionAlreadyStarting') {
                 console.log("Cannot change kernel while waiting for pending session start.");
             } else {
                 // unhandled error
                 throw e;
             }
             // only trigger spec_changed if change was successful
             return;
         }
         this.events.trigger('spec_changed.Kernel', ks);
+
+
+        // load new mode kernel.js if exist
+        require([new_mode_url],
+            // if new mode has custom.js
+            function(new_mode){
+                that.lock_switch();
+                if(new_mode && new_mode.onload){
+                    new_mode.onload();
+                } else {
+                    console.warn("The current kernel seem to define a kernel.js file; though this file does"+
+                                 "not contain any asynchronous module definition. This is undefined behavior"+
+                                 "which is not recommeneded");
+                }
+            },
+            function(err){
+                // if new mode does not have custom.js
+                console.warn('Any above 404 on '+new_mode_url+'.js is normal');
+            }
+        );
     };
-    
+
+    KernelSelector.prototype.lock_switch = function() {
+        console.warn('switching kernel is not guarantied to work !');
+    };
+
     KernelSelector.prototype.bind_events = function() {
         var that = this;
         this.events.on('spec_changed.Kernel', function(event, data) {
             that.current_selection = data.name;
             that.element.find("#current_kernel_spec").find('.kernel_name').text(data.display_name);
             that.element.find("#current_kernel_logo").attr("src", "/kernelspecs/"+data.name+"/logo-64x64.png");
         });
-        
+
         this.events.on('kernel_created.Session', function(event, data) {
             if (data.kernel.name !== that.current_selection) {
                 // If we created a 'python' session, we only know if it's Python
                 // 3 or 2 on the server's reply, so we fire the event again to
                 // set things up.
                 var ks = that.kernelspecs[data.kernel.name];
                 that.events.trigger('spec_changed.Kernel', ks);
             }
         });
         
         var logo_img = this.element.find("#current_kernel_logo")
         logo_img.on("load", function() {
             logo_img.show();
         });
         logo_img.on("error", function() {
             logo_img.hide();
         });
     };
 
     return {'KernelSelector': KernelSelector};
 });

IPython/html/static/notebook/js/main.js

@@ -1,166 +1,167 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 require([
     'base/js/namespace',
     'jquery',
     'notebook/js/notebook',
     'contents',
     'services/config',
     'base/js/utils',
     'base/js/page',
     'base/js/events',
     'auth/js/loginwidget',
     'notebook/js/maintoolbar',
     'notebook/js/pager',
     'notebook/js/quickhelp',
     'notebook/js/menubar',
     'notebook/js/notificationarea',
     'notebook/js/savewidget',
     'notebook/js/actions',
     'notebook/js/keyboardmanager',
     'notebook/js/config',
     'notebook/js/kernelselector',
     'codemirror/lib/codemirror',
     'notebook/js/about',
     // only loaded, not used, please keep sure this is loaded last
     'custom/custom'
 ], function(
     IPython, 
     $,
     notebook, 
     contents,
     configmod,
     utils, 
     page, 
     events,
     loginwidget, 
     maintoolbar, 
     pager, 
     quickhelp, 
     menubar, 
     notificationarea, 
     savewidget,
     actions,
     keyboardmanager,
     config,
     kernelselector,
     CodeMirror,
     about,
     // please keep sure that even if not used, this is loaded last
     custom
     ) {
     "use strict";
 
     // compat with old IPython, remove for IPython > 3.0
     window.CodeMirror = CodeMirror;
 
     var common_options = {
         ws_url : utils.get_body_data("wsUrl"),
         base_url : utils.get_body_data("baseUrl"),
         notebook_path : utils.get_body_data("notebookPath"),
         notebook_name : utils.get_body_data('notebookName')
     };
 
     var user_config = $.extend({}, config.default_config);
     var page = new page.Page();
     var pager = new pager.Pager('div#pager', {
         events: events});
     var acts = new actions.init();
     var keyboard_manager = new keyboardmanager.KeyboardManager({
         pager: pager, 
         events: events, 
         actions: acts });
     var save_widget = new savewidget.SaveWidget('span#save_widget', {
         events: events, 
         keyboard_manager: keyboard_manager});
     var contents = new contents.Contents($.extend({
         events: events},
         common_options));
     var config_section = new configmod.ConfigSection('notebook', common_options);
     config_section.load();
     var notebook = new notebook.Notebook('div#notebook', $.extend({
         events: events,
         keyboard_manager: keyboard_manager,
         save_widget: save_widget,
         contents: contents,
         config: user_config},
         common_options));
     var login_widget = new loginwidget.LoginWidget('span#login_widget', common_options);
     var toolbar = new maintoolbar.MainToolBar('#maintoolbar-container', {
         notebook: notebook, 
         events: events, 
         actions: acts}); 
     var quick_help = new quickhelp.QuickHelp({
         keyboard_manager: keyboard_manager, 
         events: events,
         notebook: notebook});
     keyboard_manager.set_notebook(notebook);
     keyboard_manager.set_quickhelp(quick_help);
     var menubar = new menubar.MenuBar('#menubar', $.extend({
         notebook: notebook, 
         contents: contents,
         events: events, 
         save_widget: save_widget, 
         quick_help: quick_help}, 
         common_options));
     var notification_area = new notificationarea.NotebookNotificationArea(
         '#notification_area', {
         events: events, 
         save_widget: save_widget, 
         notebook: notebook,
         keyboard_manager: keyboard_manager});
     notification_area.init_notification_widgets();
     var kernel_selector = new kernelselector.KernelSelector(
         '#kernel_selector_widget', notebook);
+    notebook.set_kernelselector(kernel_selector);
 
     $('body').append('<div id="fonttest"><pre><span id="test1">x</span>'+
                      '<span id="test2" style="font-weight: bold;">x</span>'+
                      '<span id="test3" style="font-style: italic;">x</span></pre></div>');
     var nh = $('#test1').innerHeight();
     var bh = $('#test2').innerHeight();
     var ih = $('#test3').innerHeight();
     if(nh != bh || nh != ih) {
         $('head').append('<style>.CodeMirror span { vertical-align: bottom; }</style>');
     }
     $('#fonttest').remove();
 
     page.show();
 
     var first_load = function () {
         var hash = document.location.hash;
         if (hash) {
             document.location.hash = '';
             document.location.hash = hash;
         }
         notebook.set_autosave_interval(notebook.minimum_autosave_interval);
         // only do this once
         events.off('notebook_loaded.Notebook', first_load);
     };
     events.on('notebook_loaded.Notebook', first_load);
     
     IPython.page = page;
     IPython.notebook = notebook;
     IPython.contents = contents;
     IPython.pager = pager;
     IPython.quick_help = quick_help;
     IPython.login_widget = login_widget;
     IPython.menubar = menubar;
     IPython.toolbar = toolbar;
     IPython.notification_area = notification_area;
     IPython.keyboard_manager = keyboard_manager;
     IPython.save_widget = save_widget;
     IPython.config = user_config;
     IPython.tooltip = notebook.tooltip;
 
     events.trigger('app_initialized.NotebookApp');
     config_section.loaded.then(function() {
         if (config_section.data.load_extensions) {
             var nbextension_paths = Object.getOwnPropertyNames(
                                         config_section.data.load_extensions);
             IPython.load_extensions.apply(this, nbextension_paths);
         }
     });
     notebook.load_notebook(common_options.notebook_path);
 
 });

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

@@ -1,2530 +1,2541 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     'base/js/namespace',
     'jquery',
     'base/js/utils',
     'base/js/dialog',
     'notebook/js/cell',
     'notebook/js/textcell',
     'notebook/js/codecell',
     'services/sessions/session',
     'notebook/js/celltoolbar',
     'components/marked/lib/marked',
     'codemirror/lib/codemirror',
     'codemirror/addon/runmode/runmode',
     'notebook/js/mathjaxutils',
     'base/js/keyboard',
     'notebook/js/tooltip',
     'notebook/js/celltoolbarpresets/default',
     'notebook/js/celltoolbarpresets/rawcell',
     'notebook/js/celltoolbarpresets/slideshow',
     'notebook/js/scrollmanager'
 ], function (
     IPython, 
     $,
     utils,
     dialog,
     cellmod,
     textcell,
     codecell,
     session, 
     celltoolbar,
     marked,
     CodeMirror,
     runMode,
     mathjaxutils,
     keyboard,
     tooltip,
     default_celltoolbar,
     rawcell_celltoolbar,
     slideshow_celltoolbar,
     scrollmanager
     ) {
     "use strict";
 
     var Notebook = function (selector, options) {
         /**
          * Constructor
          *
          * A notebook contains and manages cells.
          *
          * Parameters:
          *  selector: string
          *  options: dictionary
          *      Dictionary of keyword arguments.
          *          events: $(Events) instance
          *          keyboard_manager: KeyboardManager instance
          *          contents: Contents instance
          *          save_widget: SaveWidget instance
          *          config: dictionary
          *          base_url : string
          *          notebook_path : string
          *          notebook_name : string
          */
         this.config = utils.mergeopt(Notebook, options.config);
         this.base_url = options.base_url;
         this.notebook_path = options.notebook_path;
         this.notebook_name = options.notebook_name;
         this.events = options.events;
         this.keyboard_manager = options.keyboard_manager;
         this.contents = options.contents;
         this.save_widget = options.save_widget;
         this.tooltip = new tooltip.Tooltip(this.events);
         this.ws_url = options.ws_url;
         this._session_starting = false;
         this.default_cell_type = this.config.default_cell_type || 'code';
 
         //  Create default scroll manager.
         this.scroll_manager = new scrollmanager.ScrollManager(this);
 
         // TODO: This code smells (and the other `= this` line a couple lines down)
         // We need a better way to deal with circular instance references.
         this.keyboard_manager.notebook = this;
         this.save_widget.notebook = this;
         
         mathjaxutils.init();
 
         if (marked) {
             marked.setOptions({
                 gfm : true,
                 tables: true,
                 // FIXME: probably want central config for CodeMirror theme when we have js config
                 langPrefix: "cm-s-ipython language-",
                 highlight: function(code, lang, callback) {
                     if (!lang) {
                         // no language, no highlight
                         if (callback) {
                             callback(null, code);
                             return;
                         } else {
                             return code;
                         }
                     }
                     utils.requireCodeMirrorMode(lang, function (spec) {
                         var el = document.createElement("div");
                         var mode = CodeMirror.getMode({}, spec);
                         if (!mode) {
                             console.log("No CodeMirror mode: " + lang);
                             callback(null, code);
                             return;
                         }
                         try {
                             CodeMirror.runMode(code, spec, el);
                             callback(null, el.innerHTML);
                         } catch (err) {
                             console.log("Failed to highlight " + lang + " code", err);
                             callback(err, code);
                         }
                     }, function (err) {
                         console.log("No CodeMirror mode: " + lang);
                         callback(err, code);
                     });
                 }
             });
         }
 
         this.element = $(selector);
         this.element.scroll();
         this.element.data("notebook", this);
         this.next_prompt_number = 1;
         this.session = null;
         this.kernel = null;
         this.clipboard = null;
         this.undelete_backup = null;
         this.undelete_index = null;
         this.undelete_below = false;
         this.paste_enabled = false;
         this.writable = false;
         // It is important to start out in command mode to match the intial mode
         // of the KeyboardManager.
         this.mode = 'command';
         this.set_dirty(false);
         this.metadata = {};
         this._checkpoint_after_save = false;
         this.last_checkpoint = null;
         this.checkpoints = [];
         this.autosave_interval = 0;
         this.autosave_timer = null;
         // autosave *at most* every two minutes
         this.minimum_autosave_interval = 120000;
         this.notebook_name_blacklist_re = /[\/\\:]/;
         this.nbformat = 4; // Increment this when changing the nbformat
         this.nbformat_minor = this.current_nbformat_minor = 0; // Increment this when changing the nbformat
         this.codemirror_mode = 'ipython';
         this.create_elements();
         this.bind_events();
         this.kernel_selector = null;
         this.dirty = null;
         this.trusted = null;
         this._fully_loaded = false;
 
         // Trigger cell toolbar registration.
         default_celltoolbar.register(this);
         rawcell_celltoolbar.register(this);
         slideshow_celltoolbar.register(this);
 
         // prevent assign to miss-typed properties.
         Object.seal(this);
     };
 
     Notebook.options_default = {
         // can be any cell type, or the special values of
         // 'above', 'below', or 'selected' to get the value from another cell.
         Notebook: {
             default_cell_type: 'code'
         }
     };
 
 
     /**
      * Create an HTML and CSS representation of the notebook.
      * 
      * @method create_elements
      */
     Notebook.prototype.create_elements = function () {
         var that = this;
         this.element.attr('tabindex','-1');
         this.container = $("<div/>").addClass("container").attr("id", "notebook-container");
         // We add this end_space div to the end of the notebook div to:
         // i) provide a margin between the last cell and the end of the notebook
         // ii) to prevent the div from scrolling up when the last cell is being
         // edited, but is too low on the page, which browsers will do automatically.
         var end_space = $('<div/>').addClass('end_space');
         end_space.dblclick(function (e) {
             var ncells = that.ncells();
             that.insert_cell_below('code',ncells-1);
         });
         this.element.append(this.container);
         this.container.append(end_space);
     };
 
     /**
      * Bind JavaScript events: key presses and custom IPython events.
      * 
      * @method bind_events
      */
     Notebook.prototype.bind_events = function () {
         var that = this;
 
         this.events.on('set_next_input.Notebook', function (event, data) {
             if (data.replace) {
                 data.cell.set_text(data.text);
                 data.cell.clear_output();
             } else {
                 var index = that.find_cell_index(data.cell);
                 var new_cell = that.insert_cell_below('code',index);
                 new_cell.set_text(data.text);
             }
             that.dirty = true;
         });
 
         this.events.on('unrecognized_cell.Cell', function () {
             that.warn_nbformat_minor();
         });
 
         this.events.on('unrecognized_output.OutputArea', function () {
             that.warn_nbformat_minor();
         });
 
         this.events.on('set_dirty.Notebook', function (event, data) {
             that.dirty = data.value;
         });
 
         this.events.on('trust_changed.Notebook', function (event, trusted) {
             that.trusted = trusted;
         });
 
         this.events.on('select.Cell', function (event, data) {
             var index = that.find_cell_index(data.cell);
             that.select(index);
         });
 
         this.events.on('edit_mode.Cell', function (event, data) {
             that.handle_edit_mode(data.cell);
         });
 
         this.events.on('command_mode.Cell', function (event, data) {
             that.handle_command_mode(data.cell);
         });
         
         this.events.on('spec_changed.Kernel', function(event, data) {
             that.metadata.kernelspec = 
                 {name: data.name, display_name: data.display_name};
         });
 
         this.events.on('kernel_ready.Kernel', function(event, data) {
             var kinfo = data.kernel.info_reply;
             var langinfo = kinfo.language_info || {};
             that.metadata.language_info = langinfo;
             // Mode 'null' should be plain, unhighlighted text.
             var cm_mode = langinfo.codemirror_mode || langinfo.name || 'null';
             that.set_codemirror_mode(cm_mode);
         });
 
         var collapse_time = function (time) {
             var app_height = $('#ipython-main-app').height(); // content height
             var splitter_height = $('div#pager_splitter').outerHeight(true);
             var new_height = app_height - splitter_height;
             that.element.animate({height : new_height + 'px'}, time);
         };
 
         this.element.bind('collapse_pager', function (event, extrap) {
             var time = (extrap !== undefined) ? ((extrap.duration !== undefined ) ? extrap.duration : 'fast') : 'fast';
             collapse_time(time);
         });
 
         var expand_time = function (time) {
             var app_height = $('#ipython-main-app').height(); // content height
             var splitter_height = $('div#pager_splitter').outerHeight(true);
             var pager_height = $('div#pager').outerHeight(true);
             var new_height = app_height - pager_height - splitter_height;
             that.element.animate({height : new_height + 'px'}, time);
         };
 
         this.element.bind('expand_pager', function (event, extrap) {
             var time = (extrap !== undefined) ? ((extrap.duration !== undefined ) ? extrap.duration : 'fast') : 'fast';
             expand_time(time);
         });
         
         // Firefox 22 broke $(window).on("beforeunload")
         // I'm not sure why or how.
         window.onbeforeunload = function (e) {
             // TODO: Make killing the kernel configurable.
             var kill_kernel = false;
             if (kill_kernel) {
                 that.session.delete();
             }
             // if we are autosaving, trigger an autosave on nav-away.
             // still warn, because if we don't the autosave may fail.
             if (that.dirty) {
                 if ( that.autosave_interval ) {
                     // schedule autosave in a timeout
                     // this gives you a chance to forcefully discard changes
                     // by reloading the page if you *really* want to.
                     // the timer doesn't start until you *dismiss* the dialog.
                     setTimeout(function () {
                         if (that.dirty) {
                             that.save_notebook();
                         }
                     }, 1000);
                     return "Autosave in progress, latest changes may be lost.";
                 } else {
                     return "Unsaved changes will be lost.";
                 }
             }
             // Null is the *only* return value that will make the browser not
             // pop up the "don't leave" dialog.
             return null;
         };
     };
     
     Notebook.prototype.warn_nbformat_minor = function (event) {
         /**
          * trigger a warning dialog about missing functionality from newer minor versions
          */
         var v = 'v' + this.nbformat + '.';
         var orig_vs = v + this.nbformat_minor;
         var this_vs = v + this.current_nbformat_minor;
         var msg = "This notebook is version " + orig_vs + ", but we only fully support up to " +
         this_vs + ".  You can still work with this notebook, but cell and output types " +
         "introduced in later notebook versions will not be available.";
 
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title : "Newer Notebook",
             body : msg,
             buttons : {
                 OK : {
                     "class" : "btn-danger"
                 }
             }
         });
     }
 
     /**
      * Set the dirty flag, and trigger the set_dirty.Notebook event
      * 
      * @method set_dirty
      */
     Notebook.prototype.set_dirty = function (value) {
         if (value === undefined) {
             value = true;
         }
         if (this.dirty == value) {
             return;
         }
         this.events.trigger('set_dirty.Notebook', {value: value});
     };
 
     /**
      * Scroll the top of the page to a given cell.
      * 
      * @method scroll_to_cell
      * @param {Number} cell_number An index of the cell to view
      * @param {Number} time Animation time in milliseconds
      * @return {Number} Pixel offset from the top of the container
      */
     Notebook.prototype.scroll_to_cell = function (cell_number, time) {
         var cells = this.get_cells();
         time = time || 0;
         cell_number = Math.min(cells.length-1,cell_number);
         cell_number = Math.max(0             ,cell_number);
         var scroll_value = cells[cell_number].element.position().top-cells[0].element.position().top ;
         this.element.animate({scrollTop:scroll_value}, time);
         return scroll_value;
     };
 
     /**
      * Scroll to the bottom of the page.
      * 
      * @method scroll_to_bottom
      */
     Notebook.prototype.scroll_to_bottom = function () {
         this.element.animate({scrollTop:this.element.get(0).scrollHeight}, 0);
     };
 
     /**
      * Scroll to the top of the page.
      * 
      * @method scroll_to_top
      */
     Notebook.prototype.scroll_to_top = function () {
         this.element.animate({scrollTop:0}, 0);
     };
 
     // Edit Notebook metadata
 
     Notebook.prototype.edit_metadata = function () {
         var that = this;
         dialog.edit_metadata({
             md: this.metadata, 
             callback: function (md) {
                 that.metadata = md;
             },
             name: 'Notebook',
             notebook: this,
             keyboard_manager: this.keyboard_manager});
     };
 
     // Cell indexing, retrieval, etc.
 
     /**
      * Get all cell elements in the notebook.
      * 
      * @method get_cell_elements
      * @return {jQuery} A selector of all cell elements
      */
     Notebook.prototype.get_cell_elements = function () {
         return this.container.find(".cell").not('.cell .cell');
     };
 
     /**
      * Get a particular cell element.
      * 
      * @method get_cell_element
      * @param {Number} index An index of a cell to select
      * @return {jQuery} A selector of the given cell.
      */
     Notebook.prototype.get_cell_element = function (index) {
         var result = null;
         var e = this.get_cell_elements().eq(index);
         if (e.length !== 0) {
             result = e;
         }
         return result;
     };
 
     /**
      * Try to get a particular cell by msg_id.
      * 
      * @method get_msg_cell
      * @param {String} msg_id A message UUID
      * @return {Cell} Cell or null if no cell was found.
      */
     Notebook.prototype.get_msg_cell = function (msg_id) {
         return codecell.CodeCell.msg_cells[msg_id] || null;
     };
 
     /**
      * Count the cells in this notebook.
      * 
      * @method ncells
      * @return {Number} The number of cells in this notebook
      */
     Notebook.prototype.ncells = function () {
         return this.get_cell_elements().length;
     };
 
     /**
      * Get all Cell objects in this notebook.
      * 
      * @method get_cells
      * @return {Array} This notebook's Cell objects
      */
     // TODO: we are often calling cells as cells()[i], which we should optimize
     // to cells(i) or a new method.
     Notebook.prototype.get_cells = function () {
         return this.get_cell_elements().toArray().map(function (e) {
             return $(e).data("cell");
         });
     };
 
     /**
      * Get a Cell object from this notebook.
      * 
      * @method get_cell
      * @param {Number} index An index of a cell to retrieve
      * @return {Cell} Cell or null if no cell was found.
      */
     Notebook.prototype.get_cell = function (index) {
         var result = null;
         var ce = this.get_cell_element(index);
         if (ce !== null) {
             result = ce.data('cell');
         }
         return result;
     };
 
     /**
      * Get the cell below a given cell.
      * 
      * @method get_next_cell
      * @param {Cell} cell The provided cell
      * @return {Cell} the next cell or null if no cell was found.
      */
     Notebook.prototype.get_next_cell = function (cell) {
         var result = null;
         var index = this.find_cell_index(cell);
         if (this.is_valid_cell_index(index+1)) {
             result = this.get_cell(index+1);
         }
         return result;
     };
 
     /**
      * Get the cell above a given cell.
      * 
      * @method get_prev_cell
      * @param {Cell} cell The provided cell
      * @return {Cell} The previous cell or null if no cell was found.
      */
     Notebook.prototype.get_prev_cell = function (cell) {
         var result = null;
         var index = this.find_cell_index(cell);
         if (index !== null && index > 0) {
             result = this.get_cell(index-1);
         }
         return result;
     };
     
     /**
      * Get the numeric index of a given cell.
      * 
      * @method find_cell_index
      * @param {Cell} cell The provided cell
      * @return {Number} The cell's numeric index or null if no cell was found.
      */
     Notebook.prototype.find_cell_index = function (cell) {
         var result = null;
         this.get_cell_elements().filter(function (index) {
             if ($(this).data("cell") === cell) {
                 result = index;
             }
         });
         return result;
     };
 
     /**
      * Get a given index , or the selected index if none is provided.
      * 
      * @method index_or_selected
      * @param {Number} index A cell's index
      * @return {Number} The given index, or selected index if none is provided.
      */
     Notebook.prototype.index_or_selected = function (index) {
         var i;
         if (index === undefined || index === null) {
             i = this.get_selected_index();
             if (i === null) {
                 i = 0;
             }
         } else {
             i = index;
         }
         return i;
     };
 
     /**
      * Get the currently selected cell.
      * @method get_selected_cell
      * @return {Cell} The selected cell
      */
     Notebook.prototype.get_selected_cell = function () {
         var index = this.get_selected_index();
         return this.get_cell(index);
     };
 
     /**
      * Check whether a cell index is valid.
      * 
      * @method is_valid_cell_index
      * @param {Number} index A cell index
      * @return True if the index is valid, false otherwise
      */
     Notebook.prototype.is_valid_cell_index = function (index) {
         if (index !== null && index >= 0 && index < this.ncells()) {
             return true;
         } else {
             return false;
         }
     };
 
     /**
      * Get the index of the currently selected cell.
      
      * @method get_selected_index
      * @return {Number} The selected cell's numeric index
      */
     Notebook.prototype.get_selected_index = function () {
         var result = null;
         this.get_cell_elements().filter(function (index) {
             if ($(this).data("cell").selected === true) {
                 result = index;
             }
         });
         return result;
     };
 
 
     // Cell selection.
 
     /**
      * Programmatically select a cell.
      * 
      * @method select
      * @param {Number} index A cell's index
      * @return {Notebook} This notebook
      */
     Notebook.prototype.select = function (index) {
         if (this.is_valid_cell_index(index)) {
             var sindex = this.get_selected_index();
             if (sindex !== null && index !== sindex) {
                 // If we are about to select a different cell, make sure we are
                 // first in command mode.
                 if (this.mode !== 'command') {
                     this.command_mode();
                 }
                 this.get_cell(sindex).unselect();
             }
             var cell = this.get_cell(index);
             cell.select();
             if (cell.cell_type === 'heading') {
                 this.events.trigger('selected_cell_type_changed.Notebook',
                     {'cell_type':cell.cell_type,level:cell.level}
                 );
             } else {
                 this.events.trigger('selected_cell_type_changed.Notebook',
                     {'cell_type':cell.cell_type}
                 );
             }
         }
         return this;
     };
 
     /**
      * Programmatically select the next cell.
      *
      * @method select_next
      * @return {Notebook} This notebook
      */
     Notebook.prototype.select_next = function () {
         var index = this.get_selected_index();
         this.select(index+1);
         return this;
     };
 
     /**
      * Programmatically select the previous cell.
      *
      * @method select_prev
      * @return {Notebook} This notebook
      */
     Notebook.prototype.select_prev = function () {
         var index = this.get_selected_index();
         this.select(index-1);
         return this;
     };
 
 
     // Edit/Command mode
 
     /**
      * Gets the index of the cell that is in edit mode.
      *
      * @method get_edit_index
      *
      * @return index {int}
      **/
     Notebook.prototype.get_edit_index = function () {
         var result = null;
         this.get_cell_elements().filter(function (index) {
             if ($(this).data("cell").mode === 'edit') {
                 result = index;
             }
         });
         return result;
     };
 
     /**
      * Handle when a a cell blurs and the notebook should enter command mode.
      *
      * @method handle_command_mode
      * @param [cell] {Cell} Cell to enter command mode on.
      **/
     Notebook.prototype.handle_command_mode = function (cell) {
         if (this.mode !== 'command') {
             cell.command_mode();
             this.mode = 'command';
             this.events.trigger('command_mode.Notebook');
             this.keyboard_manager.command_mode();
         }
     };
 
     /**
      * Make the notebook enter command mode.
      *
      * @method command_mode
      **/
     Notebook.prototype.command_mode = function () {
         var cell = this.get_cell(this.get_edit_index());
         if (cell && this.mode !== 'command') {
             // We don't call cell.command_mode, but rather call cell.focus_cell()
             // which will blur and CM editor and trigger the call to
             // handle_command_mode.
             cell.focus_cell();
         }
     };
 
     /**
      * Handle when a cell fires it's edit_mode event.
      *
      * @method handle_edit_mode
      * @param [cell] {Cell} Cell to enter edit mode on.
      **/
     Notebook.prototype.handle_edit_mode = function (cell) {
         if (cell && this.mode !== 'edit') {
             cell.edit_mode();
             this.mode = 'edit';
             this.events.trigger('edit_mode.Notebook');
             this.keyboard_manager.edit_mode();
         }
     };
 
     /**
      * Make a cell enter edit mode.
      *
      * @method edit_mode
      **/
     Notebook.prototype.edit_mode = function () {
         var cell = this.get_selected_cell();
         if (cell && this.mode !== 'edit') {
             cell.unrender();
             cell.focus_editor();
         }
     };
 
     /**
      * Focus the currently selected cell.
      *
      * @method focus_cell
      **/
     Notebook.prototype.focus_cell = function () {
         var cell = this.get_selected_cell();
         if (cell === null) {return;}  // No cell is selected
         cell.focus_cell();
     };
 
     // Cell movement
 
     /**
      * Move given (or selected) cell up and select it.
      * 
      * @method move_cell_up
      * @param [index] {integer} cell index
      * @return {Notebook} This notebook
      **/
     Notebook.prototype.move_cell_up = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i) && i > 0) {
             var pivot = this.get_cell_element(i-1);
             var tomove = this.get_cell_element(i);
             if (pivot !== null && tomove !== null) {
                 tomove.detach();
                 pivot.before(tomove);
                 this.select(i-1);
                 var cell = this.get_selected_cell();
                 cell.focus_cell();
             }
             this.set_dirty(true);
         }
         return this;
     };
 
 
     /**
      * Move given (or selected) cell down and select it
      * 
      * @method move_cell_down
      * @param [index] {integer} cell index
      * @return {Notebook} This notebook
      **/
     Notebook.prototype.move_cell_down = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i) && this.is_valid_cell_index(i+1)) {
             var pivot = this.get_cell_element(i+1);
             var tomove = this.get_cell_element(i);
             if (pivot !== null && tomove !== null) {
                 tomove.detach();
                 pivot.after(tomove);
                 this.select(i+1);
                 var cell = this.get_selected_cell();
                 cell.focus_cell();
             }
         }
         this.set_dirty();
         return this;
     };
 
 
     // Insertion, deletion.
 
     /**
      * Delete a cell from the notebook.
      * 
      * @method delete_cell
      * @param [index] A cell's numeric index
      * @return {Notebook} This notebook
      */
     Notebook.prototype.delete_cell = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (!cell.is_deletable()) {
             return this;
         }
 
         this.undelete_backup = cell.toJSON();
         $('#undelete_cell').removeClass('disabled');
         if (this.is_valid_cell_index(i)) {
             var old_ncells = this.ncells();
             var ce = this.get_cell_element(i);
             ce.remove();
             if (i === 0) {
                 // Always make sure we have at least one cell.
                 if (old_ncells === 1) {
                     this.insert_cell_below('code');
                 }
                 this.select(0);
                 this.undelete_index = 0;
                 this.undelete_below = false;
             } else if (i === old_ncells-1 && i !== 0) {
                 this.select(i-1);
                 this.undelete_index = i - 1;
                 this.undelete_below = true;
             } else {
                 this.select(i);
                 this.undelete_index = i;
                 this.undelete_below = false;
             }
             this.events.trigger('delete.Cell', {'cell': cell, 'index': i});
             this.set_dirty(true);
         }
         return this;
     };
 
     /**
      * Restore the most recently deleted cell.
      * 
      * @method undelete
      */
     Notebook.prototype.undelete_cell = function() {
         if (this.undelete_backup !== null && this.undelete_index !== null) {
             var current_index = this.get_selected_index();
             if (this.undelete_index < current_index) {
                 current_index = current_index + 1;
             }
             if (this.undelete_index >= this.ncells()) {
                 this.select(this.ncells() - 1);
             }
             else {
                 this.select(this.undelete_index);
             }
             var cell_data = this.undelete_backup;
             var new_cell = null;
             if (this.undelete_below) {
                 new_cell = this.insert_cell_below(cell_data.cell_type);
             } else {
                 new_cell = this.insert_cell_above(cell_data.cell_type);
             }
             new_cell.fromJSON(cell_data);
             if (this.undelete_below) {
                 this.select(current_index+1);
             } else {
                 this.select(current_index);
             }
             this.undelete_backup = null;
             this.undelete_index = null;
         }
         $('#undelete_cell').addClass('disabled');
     };
 
     /**
      * Insert a cell so that after insertion the cell is at given index.
      *
      * If cell type is not provided, it will default to the type of the
      * currently active cell.
      *
      * Similar to insert_above, but index parameter is mandatory
      *
      * Index will be brought back into the accessible range [0,n]
      *
      * @method insert_cell_at_index
      * @param [type] {string} in ['code','markdown', 'raw'], defaults to 'code'
      * @param [index] {int} a valid index where to insert cell
      *
      * @return cell {cell|null} created cell or null
      **/
     Notebook.prototype.insert_cell_at_index = function(type, index){
 
         var ncells = this.ncells();
         index = Math.min(index, ncells);
         index = Math.max(index, 0);
         var cell = null;
         type = type || this.default_cell_type;
         if (type === 'above') {
             if (index > 0) {
                 type = this.get_cell(index-1).cell_type;
             } else {
                 type = 'code';
             }
         } else if (type === 'below') {
             if (index < ncells) {
                 type = this.get_cell(index).cell_type;
             } else {
                 type = 'code';
             }
         } else if (type === 'selected') {
             type = this.get_selected_cell().cell_type;
         }
 
         if (ncells === 0 || this.is_valid_cell_index(index) || index === ncells) {
             var cell_options = {
                 events: this.events, 
                 config: this.config, 
                 keyboard_manager: this.keyboard_manager, 
                 notebook: this,
                 tooltip: this.tooltip
             };
             switch(type) {
             case 'code':
                 cell = new codecell.CodeCell(this.kernel, cell_options);
                 cell.set_input_prompt();
                 break;
             case 'markdown':
                 cell = new textcell.MarkdownCell(cell_options);
                 break;
             case 'raw':
                 cell = new textcell.RawCell(cell_options);
                 break;
             default:
                 console.log("Unrecognized cell type: ", type, cellmod);
                 cell = new cellmod.UnrecognizedCell(cell_options);
             }
 
             if(this._insert_element_at_index(cell.element,index)) {
                 cell.render();
                 this.events.trigger('create.Cell', {'cell': cell, 'index': index});
                 cell.refresh();
                 // We used to select the cell after we refresh it, but there
                 // are now cases were this method is called where select is
                 // not appropriate. The selection logic should be handled by the
                 // caller of the the top level insert_cell methods.
                 this.set_dirty(true);
             }
         }
         return cell;
 
     };
 
     /**
      * Insert an element at given cell index.
      *
      * @method _insert_element_at_index
      * @param element {dom_element} a cell element
      * @param [index] {int} a valid index where to inser cell
      * @private
      *
      * return true if everything whent fine.
      **/
     Notebook.prototype._insert_element_at_index = function(element, index){
         if (element === undefined){
             return false;
         }
 
         var ncells = this.ncells();
 
         if (ncells === 0) {
             // special case append if empty
             this.element.find('div.end_space').before(element);
         } else if ( ncells === index ) {
             // special case append it the end, but not empty
             this.get_cell_element(index-1).after(element);
         } else if (this.is_valid_cell_index(index)) {
             // otherwise always somewhere to append to
             this.get_cell_element(index).before(element);
         } else {
             return false;
         }
 
         if (this.undelete_index !== null && index <= this.undelete_index) {
             this.undelete_index = this.undelete_index + 1;
             this.set_dirty(true);
         }
         return true;
     };
 
     /**
      * Insert a cell of given type above given index, or at top
      * of notebook if index smaller than 0.
      *
      * default index value is the one of currently selected cell
      *
      * @method insert_cell_above
      * @param [type] {string} cell type
      * @param [index] {integer}
      *
      * @return handle to created cell or null
      **/
     Notebook.prototype.insert_cell_above = function (type, index) {
         index = this.index_or_selected(index);
         return this.insert_cell_at_index(type, index);
     };
 
     /**
      * Insert a cell of given type below given index, or at bottom
      * of notebook if index greater than number of cells
      *
      * default index value is the one of currently selected cell
      *
      * @method insert_cell_below
      * @param [type] {string} cell type
      * @param [index] {integer}
      *
      * @return handle to created cell or null
      *
      **/
     Notebook.prototype.insert_cell_below = function (type, index) {
         index = this.index_or_selected(index);
         return this.insert_cell_at_index(type, index+1);
     };
 
 
     /**
      * Insert cell at end of notebook
      *
      * @method insert_cell_at_bottom
      * @param {String} type cell type
      *
      * @return the added cell; or null
      **/
     Notebook.prototype.insert_cell_at_bottom = function (type){
         var len = this.ncells();
         return this.insert_cell_below(type,len-1);
     };
 
     /**
      * Turn a cell into a code cell.
      * 
      * @method to_code
      * @param {Number} [index] A cell's index
      */
     Notebook.prototype.to_code = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var source_cell = this.get_cell(i);
             if (!(source_cell instanceof codecell.CodeCell)) {
                 var target_cell = this.insert_cell_below('code',i);
                 var text = source_cell.get_text();
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 //metadata
                 target_cell.metadata = source_cell.metadata;
 
                 target_cell.set_text(text);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 target_cell.code_mirror.clearHistory();
                 source_cell.element.remove();
                 this.select(i);
                 var cursor = source_cell.code_mirror.getCursor();
                 target_cell.code_mirror.setCursor(cursor);
                 this.set_dirty(true);
             }
         }
     };
 
     /**
      * Turn a cell into a Markdown cell.
      * 
      * @method to_markdown
      * @param {Number} [index] A cell's index
      */
     Notebook.prototype.to_markdown = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var source_cell = this.get_cell(i);
 
             if (!(source_cell instanceof textcell.MarkdownCell)) {
                 var target_cell = this.insert_cell_below('markdown',i);
                 var text = source_cell.get_text();
 
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 // metadata
                 target_cell.metadata = source_cell.metadata;
                 // We must show the editor before setting its contents
                 target_cell.unrender();
                 target_cell.set_text(text);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 target_cell.code_mirror.clearHistory();
                 source_cell.element.remove();
                 this.select(i);
                 if ((source_cell instanceof textcell.TextCell) && source_cell.rendered) {
                     target_cell.render();
                 }
                 var cursor = source_cell.code_mirror.getCursor();
                 target_cell.code_mirror.setCursor(cursor);
                 this.set_dirty(true);
             }
         }
     };
 
     /**
      * Turn a cell into a raw text cell.
      * 
      * @method to_raw
      * @param {Number} [index] A cell's index
      */
     Notebook.prototype.to_raw = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var target_cell = null;
             var source_cell = this.get_cell(i);
 
             if (!(source_cell instanceof textcell.RawCell)) {
                 target_cell = this.insert_cell_below('raw',i);
                 var text = source_cell.get_text();
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 //metadata
                 target_cell.metadata = source_cell.metadata;
                 // We must show the editor before setting its contents
                 target_cell.unrender();
                 target_cell.set_text(text);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 target_cell.code_mirror.clearHistory();
                 source_cell.element.remove();
                 this.select(i);
                 var cursor = source_cell.code_mirror.getCursor();
                 target_cell.code_mirror.setCursor(cursor);
                 this.set_dirty(true);
             }
         }
     };
     
     Notebook.prototype._warn_heading = function () {
         /**
          * warn about heading cells being removed
          */
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title : "Use markdown headings",
             body : $("<p/>").text(
                 'IPython no longer uses special heading cells. ' + 
                 'Instead, write your headings in Markdown cells using # characters:'
             ).append($('<pre/>').text(
                 '## This is a level 2 heading'
             )),
             buttons : {
                 "OK" : {}
             }
         });
     };
     
     /**
      * Turn a cell into a markdown cell with a heading.
      * 
      * @method to_heading
      * @param {Number} [index] A cell's index
      * @param {Number} [level] A heading level (e.g., 1 for h1)
      */
     Notebook.prototype.to_heading = function (index, level) {
         this.to_markdown(index);
         level = level || 1;
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var cell = this.get_cell(i);
             cell.set_heading_level(level);
             this.set_dirty(true);
         }
     };
 
 
     // Cut/Copy/Paste
 
     /**
      * Enable UI elements for pasting cells.
      * 
      * @method enable_paste
      */
     Notebook.prototype.enable_paste = function () {
         var that = this;
         if (!this.paste_enabled) {
             $('#paste_cell_replace').removeClass('disabled')
                 .on('click', function () {that.paste_cell_replace();});
             $('#paste_cell_above').removeClass('disabled')
                 .on('click', function () {that.paste_cell_above();});
             $('#paste_cell_below').removeClass('disabled')
                 .on('click', function () {that.paste_cell_below();});
             this.paste_enabled = true;
         }
     };
 
     /**
      * Disable UI elements for pasting cells.
      * 
      * @method disable_paste
      */
     Notebook.prototype.disable_paste = function () {
         if (this.paste_enabled) {
             $('#paste_cell_replace').addClass('disabled').off('click');
             $('#paste_cell_above').addClass('disabled').off('click');
             $('#paste_cell_below').addClass('disabled').off('click');
             this.paste_enabled = false;
         }
     };
 
     /**
      * Cut a cell.
      * 
      * @method cut_cell
      */
     Notebook.prototype.cut_cell = function () {
         this.copy_cell();
         this.delete_cell();
     };
 
     /**
      * Copy a cell.
      * 
      * @method copy_cell
      */
     Notebook.prototype.copy_cell = function () {
         var cell = this.get_selected_cell();
         this.clipboard = cell.toJSON();
         // remove undeletable status from the copied cell
         if (this.clipboard.metadata.deletable !== undefined) {
             delete this.clipboard.metadata.deletable;
         }
         this.enable_paste();
     };
 
     /**
      * Replace the selected cell with a cell in the clipboard.
      * 
      * @method paste_cell_replace
      */
     Notebook.prototype.paste_cell_replace = function () {
         if (this.clipboard !== null && this.paste_enabled) {
             var cell_data = this.clipboard;
             var new_cell = this.insert_cell_above(cell_data.cell_type);
             new_cell.fromJSON(cell_data);
             var old_cell = this.get_next_cell(new_cell);
             this.delete_cell(this.find_cell_index(old_cell));
             this.select(this.find_cell_index(new_cell));
         }
     };
 
     /**
      * Paste a cell from the clipboard above the selected cell.
      * 
      * @method paste_cell_above
      */
     Notebook.prototype.paste_cell_above = function () {
         if (this.clipboard !== null && this.paste_enabled) {
             var cell_data = this.clipboard;
             var new_cell = this.insert_cell_above(cell_data.cell_type);
             new_cell.fromJSON(cell_data);
             new_cell.focus_cell();
         }
     };
 
     /**
      * Paste a cell from the clipboard below the selected cell.
      * 
      * @method paste_cell_below
      */
     Notebook.prototype.paste_cell_below = function () {
         if (this.clipboard !== null && this.paste_enabled) {
             var cell_data = this.clipboard;
             var new_cell = this.insert_cell_below(cell_data.cell_type);
             new_cell.fromJSON(cell_data);
             new_cell.focus_cell();
         }
     };
 
     // Split/merge
 
     /**
      * Split the selected cell into two, at the cursor.
      * 
      * @method split_cell
      */
     Notebook.prototype.split_cell = function () {
         var cell = this.get_selected_cell();
         if (cell.is_splittable()) {
             var texta = cell.get_pre_cursor();
             var textb = cell.get_post_cursor();
             cell.set_text(textb);
             var new_cell = this.insert_cell_above(cell.cell_type);
             // Unrender the new cell so we can call set_text.
             new_cell.unrender();
             new_cell.set_text(texta);
         }
     };
 
     /**
      * Combine the selected cell into the cell above it.
      * 
      * @method merge_cell_above
      */
     Notebook.prototype.merge_cell_above = function () {
         var index = this.get_selected_index();
         var cell = this.get_cell(index);
         var render = cell.rendered;
         if (!cell.is_mergeable()) {
             return;
         }
         if (index > 0) {
             var upper_cell = this.get_cell(index-1);
             if (!upper_cell.is_mergeable()) {
                 return;
             }
             var upper_text = upper_cell.get_text();
             var text = cell.get_text();
             if (cell instanceof codecell.CodeCell) {
                 cell.set_text(upper_text+'\n'+text);
             } else {
                 cell.unrender(); // Must unrender before we set_text.
                 cell.set_text(upper_text+'\n\n'+text);
                 if (render) {
                     // The rendered state of the final cell should match
                     // that of the original selected cell;
                     cell.render();
                 }
             }
             this.delete_cell(index-1);
             this.select(this.find_cell_index(cell));
         }
     };
 
     /**
      * Combine the selected cell into the cell below it.
      * 
      * @method merge_cell_below
      */
     Notebook.prototype.merge_cell_below = function () {
         var index = this.get_selected_index();
         var cell = this.get_cell(index);
         var render = cell.rendered;
         if (!cell.is_mergeable()) {
             return;
         }
         if (index < this.ncells()-1) {
             var lower_cell = this.get_cell(index+1);
             if (!lower_cell.is_mergeable()) {
                 return;
             }
             var lower_text = lower_cell.get_text();
             var text = cell.get_text();
             if (cell instanceof codecell.CodeCell) {
                 cell.set_text(text+'\n'+lower_text);
             } else {
                 cell.unrender(); // Must unrender before we set_text.
                 cell.set_text(text+'\n\n'+lower_text);
                 if (render) {
                     // The rendered state of the final cell should match
                     // that of the original selected cell;
                     cell.render();
                 }
             }
             this.delete_cell(index+1);
             this.select(this.find_cell_index(cell));
         }
     };
 
 
     // Cell collapsing and output clearing
 
     /**
      * Hide a cell's output.
      * 
      * @method collapse_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.collapse_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.collapse_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Hide each code cell's output area.
      * 
      * @method collapse_all_output
      */
     Notebook.prototype.collapse_all_output = function () {
         this.get_cells().map(function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.collapse_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /**
      * Show a cell's output.
      * 
      * @method expand_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.expand_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.expand_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Expand each code cell's output area, and remove scrollbars.
      * 
      * @method expand_all_output
      */
     Notebook.prototype.expand_all_output = function () {
         this.get_cells().map(function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.expand_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /**
      * Clear the selected CodeCell's output area.
      * 
      * @method clear_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.clear_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.clear_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Clear each code cell's output area.
      * 
      * @method clear_all_output
      */
     Notebook.prototype.clear_all_output = function () {
         this.get_cells().map(function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.clear_output();
             }
         });
         this.set_dirty(true);
     };
 
     /**
      * Scroll the selected CodeCell's output area.
      * 
      * @method scroll_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.scroll_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.scroll_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Expand each code cell's output area, and add a scrollbar for long output.
      * 
      * @method scroll_all_output
      */
     Notebook.prototype.scroll_all_output = function () {
         this.get_cells().map(function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.scroll_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /** Toggle whether a cell's output is collapsed or expanded.
      * 
      * @method toggle_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.toggle_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.toggle_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Hide/show the output of all cells.
      * 
      * @method toggle_all_output
      */
     Notebook.prototype.toggle_all_output = function () {
         this.get_cells().map(function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.toggle_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /**
      * Toggle a scrollbar for long cell outputs.
      * 
      * @method toggle_output_scroll
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.toggle_output_scroll = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.toggle_output_scroll();
             this.set_dirty(true);
         }
     };
 
     /**
      * Toggle the scrolling of long output on all cells.
      * 
      * @method toggle_all_output_scrolling
      */
     Notebook.prototype.toggle_all_output_scroll = function () {
         this.get_cells().map(function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.toggle_output_scroll();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     // Other cell functions: line numbers, ...
 
     /**
      * Toggle line numbers in the selected cell's input area.
      * 
      * @method cell_toggle_line_numbers
      */
     Notebook.prototype.cell_toggle_line_numbers = function() {
         this.get_selected_cell().toggle_line_numbers();
     };
     
     /**
      * Set the codemirror mode for all code cells, including the default for
      * new code cells.
      * 
      * @method set_codemirror_mode
      */
     Notebook.prototype.set_codemirror_mode = function(newmode){
         if (newmode === this.codemirror_mode) {
             return;
         }
         this.codemirror_mode = newmode;
         codecell.CodeCell.options_default.cm_config.mode = newmode;
         
         var that = this;
         utils.requireCodeMirrorMode(newmode, function (spec) {
             that.get_cells().map(function(cell, i) {
                 if (cell.cell_type === 'code'){
                     cell.code_mirror.setOption('mode', spec);
                     // This is currently redundant, because cm_config ends up as
                     // codemirror's own .options object, but I don't want to
                     // rely on that.
                     cell.cm_config.mode = spec;
                 }
             });
         });
     };
 
     // Session related things
 
     /**
      * Start a new session and set it on each code cell.
      * 
      * @method start_session
      */
     Notebook.prototype.start_session = function (kernel_name) {
         if (this._session_starting) {
             throw new session.SessionAlreadyStarting();
         }
         this._session_starting = true;
 
         var options = {
             base_url: this.base_url,
             ws_url: this.ws_url,
             notebook_path: this.notebook_path,
             notebook_name: this.notebook_name,
             kernel_name: kernel_name,
             notebook: this
         };
 
         var success = $.proxy(this._session_started, this);
         var failure = $.proxy(this._session_start_failed, this);
 
         if (this.session !== null) {
             this.session.restart(options, success, failure);
         } else {
             this.session = new session.Session(options);
             this.session.start(success, failure);
         }
     };
 
 
     /**
      * Once a session is started, link the code cells to the kernel and pass the 
      * comm manager to the widget manager
      *
      */
     Notebook.prototype._session_started = function (){
         this._session_starting = false;
         this.kernel = this.session.kernel;
         var ncells = this.ncells();
         for (var i=0; i<ncells; i++) {
             var cell = this.get_cell(i);
             if (cell instanceof codecell.CodeCell) {
                 cell.set_kernel(this.session.kernel);
             }
         }
     };
     Notebook.prototype._session_start_failed = function (jqxhr, status, error){
         this._session_starting = false;
         utils.log_ajax_error(jqxhr, status, error);
     };
     
     /**
      * Prompt the user to restart the IPython kernel.
      * 
      * @method restart_kernel
      */
     Notebook.prototype.restart_kernel = function () {
         var that = this;
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title : "Restart kernel or continue running?",
             body : $("<p/>").text(
                 'Do you want to restart the current kernel?  You will lose all variables defined in it.'
             ),
             buttons : {
                 "Continue running" : {},
                 "Restart" : {
                     "class" : "btn-danger",
                     "click" : function() {
                         that.kernel.restart();
                     }
                 }
             }
         });
     };
     
     /**
      * Execute or render cell outputs and go into command mode.
      * 
      * @method execute_cell
      */
     Notebook.prototype.execute_cell = function () {
         /**
          * mode = shift, ctrl, alt
          */
         var cell = this.get_selected_cell();
         
         cell.execute();
         this.command_mode();
         this.set_dirty(true);
     };
 
     /**
      * Execute or render cell outputs and insert a new cell below.
      * 
      * @method execute_cell_and_insert_below
      */
     Notebook.prototype.execute_cell_and_insert_below = function () {
         var cell = this.get_selected_cell();
         var cell_index = this.find_cell_index(cell);
         
         cell.execute();
 
         // If we are at the end always insert a new cell and return
         if (cell_index === (this.ncells()-1)) {
             this.command_mode();
             this.insert_cell_below();
             this.select(cell_index+1);
             this.edit_mode();
             this.scroll_to_bottom();
             this.set_dirty(true);
             return;
         }
 
         this.command_mode();
         this.insert_cell_below();
         this.select(cell_index+1);
         this.edit_mode();
         this.set_dirty(true);
     };
 
     /**
      * Execute or render cell outputs and select the next cell.
      * 
      * @method execute_cell_and_select_below
      */
     Notebook.prototype.execute_cell_and_select_below = function () {
 
         var cell = this.get_selected_cell();
         var cell_index = this.find_cell_index(cell);
         
         cell.execute();
 
         // If we are at the end always insert a new cell and return
         if (cell_index === (this.ncells()-1)) {
             this.command_mode();
             this.insert_cell_below();
             this.select(cell_index+1);
             this.edit_mode();
             this.scroll_to_bottom();
             this.set_dirty(true);
             return;
         }
 
         this.command_mode();
         this.select(cell_index+1);
         this.focus_cell();
         this.set_dirty(true);
     };
 
     /**
      * Execute all cells below the selected cell.
      * 
      * @method execute_cells_below
      */
     Notebook.prototype.execute_cells_below = function () {
         this.execute_cell_range(this.get_selected_index(), this.ncells());
         this.scroll_to_bottom();
     };
 
     /**
      * Execute all cells above the selected cell.
      * 
      * @method execute_cells_above
      */
     Notebook.prototype.execute_cells_above = function () {
         this.execute_cell_range(0, this.get_selected_index());
     };
 
     /**
      * Execute all cells.
      * 
      * @method execute_all_cells
      */
     Notebook.prototype.execute_all_cells = function () {
         this.execute_cell_range(0, this.ncells());
         this.scroll_to_bottom();
     };
 
     /**
      * Execute a contiguous range of cells.
      * 
      * @method execute_cell_range
      * @param {Number} start Index of the first cell to execute (inclusive)
      * @param {Number} end Index of the last cell to execute (exclusive)
      */
     Notebook.prototype.execute_cell_range = function (start, end) {
         this.command_mode();
         for (var i=start; i<end; i++) {
             this.select(i);
             this.execute_cell();
         }
     };
 
     // Persistance and loading
 
     /**
      * Getter method for this notebook's name.
      * 
      * @method get_notebook_name
      * @return {String} This notebook's name (excluding file extension)
      */
     Notebook.prototype.get_notebook_name = function () {
         var nbname = this.notebook_name.substring(0,this.notebook_name.length-6);
         return nbname;
     };
 
     /**
      * Setter method for this notebook's name.
      *
      * @method set_notebook_name
      * @param {String} name A new name for this notebook
      */
     Notebook.prototype.set_notebook_name = function (name) {
         var parent = utils.url_path_split(this.notebook_path)[0];
         this.notebook_name = name;
         this.notebook_path = utils.url_path_join(parent, name);
     };
 
     /**
      * Check that a notebook's name is valid.
      * 
      * @method test_notebook_name
      * @param {String} nbname A name for this notebook
      * @return {Boolean} True if the name is valid, false if invalid
      */
     Notebook.prototype.test_notebook_name = function (nbname) {
         nbname = nbname || '';
         if (nbname.length>0 && !this.notebook_name_blacklist_re.test(nbname)) {
             return true;
         } else {
             return false;
         }
     };
 
     /**
      * Load a notebook from JSON (.ipynb).
      * 
      * @method fromJSON
      * @param {Object} data JSON representation of a notebook
      */
     Notebook.prototype.fromJSON = function (data) {
 
         var content = data.content;
         var ncells = this.ncells();
         var i;
         for (i=0; i<ncells; i++) {
             // Always delete cell 0 as they get renumbered as they are deleted.
             this.delete_cell(0);
         }
         // Save the metadata and name.
         this.metadata = content.metadata;
         this.notebook_name = data.name;
         this.notebook_path = data.path;
         var trusted = true;
         
         // Trigger an event changing the kernel spec - this will set the default
         // codemirror mode
         if (this.metadata.kernelspec !== undefined) {
-            this.events.trigger('spec_changed.Kernel', this.metadata.kernelspec);
+            // TODO shoudl probably not trigger here, 
+            // should call the kernel selector, or custom.{js|css} not loaded.
+            if(this.kernel_selector){
+                // technically not perfect, we should check that the kernelspec matches
+                this.kernel_selector.change_kernel(this.metadata.kernelspec.name);
+            } else {
+                console.log('do not have handle on kernnel_selector');
+            }
         }
         
         // Set the codemirror mode from language_info metadata
         if (this.metadata.language_info !== undefined) {
             var langinfo = this.metadata.language_info;
             // Mode 'null' should be plain, unhighlighted text.
             var cm_mode = langinfo.codemirror_mode || langinfo.name || 'null';
             this.set_codemirror_mode(cm_mode);
         }
         
         var new_cells = content.cells;
         ncells = new_cells.length;
         var cell_data = null;
         var new_cell = null;
         for (i=0; i<ncells; i++) {
             cell_data = new_cells[i];
             new_cell = this.insert_cell_at_index(cell_data.cell_type, i);
             new_cell.fromJSON(cell_data);
             if (new_cell.cell_type == 'code' && !new_cell.output_area.trusted) {
                 trusted = false;
             }
         }
         if (trusted !== this.trusted) {
             this.trusted = trusted;
             this.events.trigger("trust_changed.Notebook", trusted);
         }
     };
 
     /**
      * Dump this notebook into a JSON-friendly object.
      * 
      * @method toJSON
      * @return {Object} A JSON-friendly representation of this notebook.
      */
     Notebook.prototype.toJSON = function () {
         /**
          * remove the conversion indicator, which only belongs in-memory
          */
         delete this.metadata.orig_nbformat;
         delete this.metadata.orig_nbformat_minor;
 
         var cells = this.get_cells();
         var ncells = cells.length;
         var cell_array = new Array(ncells);
         var trusted = true;
         for (var i=0; i<ncells; i++) {
             var cell = cells[i];
             if (cell.cell_type == 'code' && !cell.output_area.trusted) {
                 trusted = false;
             }
             cell_array[i] = cell.toJSON();
         }
         var data = {
             cells: cell_array,
             metadata: this.metadata,
             nbformat: this.nbformat,
             nbformat_minor: this.nbformat_minor
         };
         if (trusted != this.trusted) {
             this.trusted = trusted;
             this.events.trigger("trust_changed.Notebook", trusted);
         }
         return data;
     };
 
     /**
      * Start an autosave timer, for periodically saving the notebook.
      * 
      * @method set_autosave_interval
      * @param {Integer} interval the autosave interval in milliseconds
      */
     Notebook.prototype.set_autosave_interval = function (interval) {
         var that = this;
         // clear previous interval, so we don't get simultaneous timers
         if (this.autosave_timer) {
             clearInterval(this.autosave_timer);
         }
         if (!this.writable) {
             // disable autosave if not writable
             interval = 0;
         }
         
         this.autosave_interval = this.minimum_autosave_interval = interval;
         if (interval) {
             this.autosave_timer = setInterval(function() {
                 if (that.dirty) {
                     that.save_notebook();
                 }
             }, interval);
             this.events.trigger("autosave_enabled.Notebook", interval);
         } else {
             this.autosave_timer = null;
             this.events.trigger("autosave_disabled.Notebook");
         }
     };
     
     /**
      * Save this notebook on the server. This becomes a notebook instance's
      * .save_notebook method *after* the entire notebook has been loaded.
      * 
      * @method save_notebook
      */
     Notebook.prototype.save_notebook = function () {
         if (!this._fully_loaded) {
             this.events.trigger('notebook_save_failed.Notebook',
                 new Error("Load failed, save is disabled")
             );
             return;
         } else if (!this.writable) {
             this.events.trigger('notebook_save_failed.Notebook',
                 new Error("Notebook is read-only")
             );
             return;
         }
 
         // Trigger an event before save, which allows listeners to modify
         // the notebook as needed.
         this.events.trigger('before_save.Notebook');
 
         // Create a JSON model to be sent to the server.
         var model = {
             type : "notebook",
             content : this.toJSON()
         };
         // time the ajax call for autosave tuning purposes.
         var start =  new Date().getTime();
 
         var that = this;
         return this.contents.save(this.notebook_path, model).then(
                 $.proxy(this.save_notebook_success, this, start),
                 function (error) {
                     that.events.trigger('notebook_save_failed.Notebook', error);
                 }
             );
     };
     
     /**
      * Success callback for saving a notebook.
      * 
      * @method save_notebook_success
      * @param {Integer} start Time when the save request start
      * @param {Object} data JSON representation of a notebook
      */
     Notebook.prototype.save_notebook_success = function (start, data) {
         this.set_dirty(false);
         if (data.message) {
             // save succeeded, but validation failed.
             var body = $("<div>");
             var title = "Notebook validation failed";
 
             body.append($("<p>").text(
                 "The save operation succeeded," +
                 " but the notebook does not appear to be valid." +
                 " The validation error was:"
             )).append($("<div>").addClass("validation-error").append(
                 $("<pre>").text(data.message)
             ));
             dialog.modal({
                 notebook: this,
                 keyboard_manager: this.keyboard_manager,
                 title: title,
                 body: body,
                 buttons : {
                     OK : {
                         "class" : "btn-primary"
                     }
                 }
             });
         }
         this.events.trigger('notebook_saved.Notebook');
         this._update_autosave_interval(start);
         if (this._checkpoint_after_save) {
             this.create_checkpoint();
             this._checkpoint_after_save = false;
         }
     };
     
     /**
      * update the autosave interval based on how long the last save took
      * 
      * @method _update_autosave_interval
      * @param {Integer} timestamp when the save request started
      */
     Notebook.prototype._update_autosave_interval = function (start) {
         var duration = (new Date().getTime() - start);
         if (this.autosave_interval) {
             // new save interval: higher of 10x save duration or parameter (default 30 seconds)
             var interval = Math.max(10 * duration, this.minimum_autosave_interval);
             // round to 10 seconds, otherwise we will be setting a new interval too often
             interval = 10000 * Math.round(interval / 10000);
             // set new interval, if it's changed
             if (interval != this.autosave_interval) {
                 this.set_autosave_interval(interval);
             }
         }
     };
 
     /**
      * Explicitly trust the output of this notebook.
      *
      * @method trust_notebook
      */
     Notebook.prototype.trust_notebook = function () {
         var body = $("<div>").append($("<p>")
             .text("A trusted IPython notebook may execute hidden malicious code ")
             .append($("<strong>")
                 .append(
                     $("<em>").text("when you open it")
                 )
             ).append(".").append(
                 " Selecting trust will immediately reload this notebook in a trusted state."
             ).append(
                 " For more information, see the "
             ).append($("<a>").attr("href", "http://ipython.org/ipython-doc/2/notebook/security.html")
                 .text("IPython security documentation")
             ).append(".")
         );
 
         var nb = this;
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title: "Trust this notebook?",
             body: body,
 
             buttons: {
                 Cancel : {},
                 Trust : {
                     class : "btn-danger",
                     click : function () {
                         var cells = nb.get_cells();
                         for (var i = 0; i < cells.length; i++) {
                             var cell = cells[i];
                             if (cell.cell_type == 'code') {
                                 cell.output_area.trusted = true;
                             }
                         }
                         nb.events.on('notebook_saved.Notebook', function () {
                             window.location.reload();
                         });
                         nb.save_notebook();
                     }
                 }
             }
         });
     };
 
     Notebook.prototype.copy_notebook = function () {
         var that = this;
         var base_url = this.base_url;
         var w = window.open();
         var parent = utils.url_path_split(this.notebook_path)[0];
         this.contents.copy(this.notebook_path, parent).then(
             function (data) {
                 w.location = utils.url_join_encode(
                     base_url, 'notebooks', data.path
                 );
             },
             function(error) {
                 w.close();
                 that.events.trigger('notebook_copy_failed', error);
             }
         );
     };
 
     Notebook.prototype.rename = function (new_name) {
         if (!new_name.match(/\.ipynb$/)) {
             new_name = new_name + ".ipynb";
         }
 
         var that = this;
         var parent = utils.url_path_split(this.notebook_path)[0];
         var new_path = utils.url_path_join(parent, new_name);
         return this.contents.rename(this.notebook_path, new_path).then(
             function (json) {
                 that.notebook_name = json.name;
                 that.notebook_path = json.path;
                 that.session.rename_notebook(json.path);
                 that.events.trigger('notebook_renamed.Notebook', json);
             }
         );
     };
 
     Notebook.prototype.delete = function () {
         this.contents.delete(this.notebook_path);
     };
 
     /**
      * Request a notebook's data from the server.
      * 
      * @method load_notebook
      * @param {String} notebook_path A notebook to load
      */
     Notebook.prototype.load_notebook = function (notebook_path) {
         this.notebook_path = notebook_path;
         this.notebook_name = utils.url_path_split(this.notebook_path)[1];
         this.events.trigger('notebook_loading.Notebook');
         this.contents.get(notebook_path, {type: 'notebook'}).then(
             $.proxy(this.load_notebook_success, this),
             $.proxy(this.load_notebook_error, this)
         );
     };
 
     /**
      * Success callback for loading a notebook from the server.
      * 
      * Load notebook data from the JSON response.
      * 
      * @method load_notebook_success
      * @param {Object} data JSON representation of a notebook
      */
     Notebook.prototype.load_notebook_success = function (data) {
         var failed, msg;
         try {
             this.fromJSON(data);
         } catch (e) {
             failed = e;
             console.log("Notebook failed to load from JSON:", e);
         }
         if (failed || data.message) {
             // *either* fromJSON failed or validation failed
             var body = $("<div>");
             var title;
             if (failed) {
                 title = "Notebook failed to load";
                 body.append($("<p>").text(
                     "The error was: "
                 )).append($("<div>").addClass("js-error").text(
                     failed.toString()
                 )).append($("<p>").text(
                     "See the error console for details."
                 ));
             } else {
                 title = "Notebook validation failed";
             }
 
             if (data.message) {
                 if (failed) {
                     msg = "The notebook also failed validation:";
                 } else {
                     msg = "An invalid notebook may not function properly." +
                     " The validation error was:";
                 }
                 body.append($("<p>").text(
                     msg
                 )).append($("<div>").addClass("validation-error").append(
                     $("<pre>").text(data.message)
                 ));
             }
 
             dialog.modal({
                 notebook: this,
                 keyboard_manager: this.keyboard_manager,
                 title: title,
                 body: body,
                 buttons : {
                     OK : {
                         "class" : "btn-primary"
                     }
                 }
             });
         }
         if (this.ncells() === 0) {
             this.insert_cell_below('code');
             this.edit_mode(0);
         } else {
             this.select(0);
             this.handle_command_mode(this.get_cell(0));
         }
         this.set_dirty(false);
         this.scroll_to_top();
         this.writable = data.writable || false;
         var nbmodel = data.content;
         var orig_nbformat = nbmodel.metadata.orig_nbformat;
         var orig_nbformat_minor = nbmodel.metadata.orig_nbformat_minor;
         if (orig_nbformat !== undefined && nbmodel.nbformat !== orig_nbformat) {
             var src;
             if (nbmodel.nbformat > orig_nbformat) {
                 src = " an older notebook format ";
             } else {
                 src = " a newer notebook format ";
             }
             
             msg = "This notebook has been converted from" + src +
             "(v"+orig_nbformat+") to the current notebook " +
             "format (v"+nbmodel.nbformat+"). The next time you save this notebook, the " +
             "current notebook format will be used.";
             
             if (nbmodel.nbformat > orig_nbformat) {
                 msg += " Older versions of IPython may not be able to read the new format.";
             } else {
                 msg += " Some features of the original notebook may not be available.";
             }
             msg += " To preserve the original version, close the " +
                 "notebook without saving it.";
             dialog.modal({
                 notebook: this,
                 keyboard_manager: this.keyboard_manager,
                 title : "Notebook converted",
                 body : msg,
                 buttons : {
                     OK : {
                         class : "btn-primary"
                     }
                 }
             });
         } else if (this.nbformat_minor < nbmodel.nbformat_minor) {
             this.nbformat_minor = nbmodel.nbformat_minor;
         }
         
         // Create the session after the notebook is completely loaded to prevent
         // code execution upon loading, which is a security risk.
         if (this.session === null) {
             var kernel_name;
             if (this.metadata.kernelspec) {
                 var kernelspec = this.metadata.kernelspec || {};
                 kernel_name = kernelspec.name;
             } else {
                 kernel_name = utils.get_url_param('kernel_name');
             }
             this.start_session(kernel_name);
         }
         // load our checkpoint list
         this.list_checkpoints();
         
         // load toolbar state
         if (this.metadata.celltoolbar) {
             celltoolbar.CellToolbar.global_show();
             celltoolbar.CellToolbar.activate_preset(this.metadata.celltoolbar);
         } else {
             celltoolbar.CellToolbar.global_hide();
         }
         
         if (!this.writable) {
             this.set_autosave_interval(0);
             this.events.trigger('notebook_read_only.Notebook');
         }
         
         // now that we're fully loaded, it is safe to restore save functionality
         this._fully_loaded = true;
         this.events.trigger('notebook_loaded.Notebook');
     };
 
+    Notebook.prototype.set_kernelselector = function(k_selector){
+        this.kernel_selector = k_selector;
+    };
+
     /**
      * Failure callback for loading a notebook from the server.
      * 
      * @method load_notebook_error
      * @param {Error} error
      */
     Notebook.prototype.load_notebook_error = function (error) {
         this.events.trigger('notebook_load_failed.Notebook', error);
         var msg;
         if (error.name === utils.XHR_ERROR && error.xhr.status === 500) {
             utils.log_ajax_error(error.xhr, error.xhr_status, error.xhr_error);
             msg = "An unknown error occurred while loading this notebook. " +
             "This version can load notebook formats " +
             "v" + this.nbformat + " or earlier. See the server log for details.";
         } else {
             msg = error.message;
         }
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title: "Error loading notebook",
             body : msg,
             buttons : {
                 "OK": {}
             }
         });
     };
 
     /*********************  checkpoint-related  *********************/
     
     /**
      * Save the notebook then immediately create a checkpoint.
      * 
      * @method save_checkpoint
      */
     Notebook.prototype.save_checkpoint = function () {
         this._checkpoint_after_save = true;
         this.save_notebook();
     };
     
     /**
      * Add a checkpoint for this notebook.
      * for use as a callback from checkpoint creation.
      * 
      * @method add_checkpoint
      */
     Notebook.prototype.add_checkpoint = function (checkpoint) {
         var found = false;
         for (var i = 0; i < this.checkpoints.length; i++) {
             var existing = this.checkpoints[i];
             if (existing.id == checkpoint.id) {
                 found = true;
                 this.checkpoints[i] = checkpoint;
                 break;
             }
         }
         if (!found) {
             this.checkpoints.push(checkpoint);
         }
         this.last_checkpoint = this.checkpoints[this.checkpoints.length - 1];
     };
     
     /**
      * List checkpoints for this notebook.
      * 
      * @method list_checkpoints
      */
     Notebook.prototype.list_checkpoints = function () {
         var that = this;
         this.contents.list_checkpoints(this.notebook_path).then(
             $.proxy(this.list_checkpoints_success, this),
             function(error) {
                 that.events.trigger('list_checkpoints_failed.Notebook', error);
             }
         );
     };
 
     /**
      * Success callback for listing checkpoints.
      * 
      * @method list_checkpoint_success
      * @param {Object} data JSON representation of a checkpoint
      */
     Notebook.prototype.list_checkpoints_success = function (data) {
         this.checkpoints = data;
         if (data.length) {
             this.last_checkpoint = data[data.length - 1];
         } else {
             this.last_checkpoint = null;
         }
         this.events.trigger('checkpoints_listed.Notebook', [data]);
     };
 
     /**
      * Create a checkpoint of this notebook on the server from the most recent save.
      * 
      * @method create_checkpoint
      */
     Notebook.prototype.create_checkpoint = function () {
         var that = this;
         this.contents.create_checkpoint(this.notebook_path).then(
             $.proxy(this.create_checkpoint_success, this),
             function (error) {
                 that.events.trigger('checkpoint_failed.Notebook', error);
             }
         );
     };
 
     /**
      * Success callback for creating a checkpoint.
      * 
      * @method create_checkpoint_success
      * @param {Object} data JSON representation of a checkpoint
      */
     Notebook.prototype.create_checkpoint_success = function (data) {
         this.add_checkpoint(data);
         this.events.trigger('checkpoint_created.Notebook', data);
     };
 
     Notebook.prototype.restore_checkpoint_dialog = function (checkpoint) {
         var that = this;
         checkpoint = checkpoint || this.last_checkpoint;
         if ( ! checkpoint ) {
             console.log("restore dialog, but no checkpoint to restore to!");
             return;
         }
         var body = $('<div/>').append(
             $('<p/>').addClass("p-space").text(
                 "Are you sure you want to revert the notebook to " +
                 "the latest checkpoint?"
             ).append(
                 $("<strong/>").text(
                     " This cannot be undone."
                 )
             )
         ).append(
             $('<p/>').addClass("p-space").text("The checkpoint was last updated at:")
         ).append(
             $('<p/>').addClass("p-space").text(
                 Date(checkpoint.last_modified)
             ).css("text-align", "center")
         );
         
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title : "Revert notebook to checkpoint",
             body : body,
             buttons : {
                 Revert : {
                     class : "btn-danger",
                     click : function () {
                         that.restore_checkpoint(checkpoint.id);
                     }
                 },
                 Cancel : {}
                 }
         });
     };
     
     /**
      * Restore the notebook to a checkpoint state.
      * 
      * @method restore_checkpoint
      * @param {String} checkpoint ID
      */
     Notebook.prototype.restore_checkpoint = function (checkpoint) {
         this.events.trigger('notebook_restoring.Notebook', checkpoint);
         var that = this;
         this.contents.restore_checkpoint(this.notebook_path, checkpoint).then(
             $.proxy(this.restore_checkpoint_success, this),
             function (error) {
                 that.events.trigger('checkpoint_restore_failed.Notebook', error);
             }
         );
     };
     
     /**
      * Success callback for restoring a notebook to a checkpoint.
      * 
      * @method restore_checkpoint_success
      */
     Notebook.prototype.restore_checkpoint_success = function () {
         this.events.trigger('checkpoint_restored.Notebook');
         this.load_notebook(this.notebook_path);
     };
 
     /**
      * Delete a notebook checkpoint.
      * 
      * @method delete_checkpoint
      * @param {String} checkpoint ID
      */
     Notebook.prototype.delete_checkpoint = function (checkpoint) {
         this.events.trigger('notebook_restoring.Notebook', checkpoint);
         var that = this;
         this.contents.delete_checkpoint(this.notebook_path, checkpoint).then(
             $.proxy(this.delete_checkpoint_success, this),
             function (error) {
                 that.events.trigger('checkpoint_delete_failed.Notebook', error);
             }
         );
     };
     
     /**
      * Success callback for deleting a notebook checkpoint
      * 
      * @method delete_checkpoint_success
      */
     Notebook.prototype.delete_checkpoint_success = function () {
         this.events.trigger('checkpoint_deleted.Notebook');
         this.load_notebook(this.notebook_path);
     };
 
 
     // For backwards compatability.
     IPython.Notebook = Notebook;
 
     return {'Notebook': Notebook};
 });

IPython/html/templates/notebook.html

@@ -1,332 +1,333 b''
 {% extends "page.html" %}
 
 {% block stylesheet %}
 
 {% if mathjax_url %}
 <script type="text/javascript" src="{{mathjax_url}}?config=TeX-AMS_HTML-full&delayStartupUntil=configured" charset="utf-8"></script>
 {% endif %}
 <script type="text/javascript">
 // MathJax disabled, set as null to distingish from *missing* MathJax,
 // where it will be undefined, and should prompt a dialog later.
 window.mathjax_url = "{{mathjax_url}}";
 </script>
 
 <link rel="stylesheet" href="{{ static_url("components/bootstrap-tour/build/css/bootstrap-tour.min.css") }}" type="text/css" />
 <link rel="stylesheet" href="{{ static_url("components/codemirror/lib/codemirror.css") }}">
 
 {{super()}}
 
 <link rel="stylesheet" href="{{ static_url("notebook/css/override.css") }}" type="text/css" />
+<link rel="stylesheet" href=""  id='kernel-css'                             type="text/css" />
 
 {% endblock %}
 
 {% block params %}
 
 data-project="{{project}}"
 data-base-url="{{base_url}}"
 data-ws-url="{{ws_url}}"
 data-notebook-name="{{notebook_name}}"
 data-notebook-path="{{notebook_path}}"
 class="notebook_app"
 
 {% endblock %}
 
 
 {% block headercontainer %}
 
 
 <span id="save_widget" class="pull-left save_widget">
     <span class="filename"></span>
     <span class="checkpoint_status"></span>
     <span class="autosave_status"></span>
 </span>
 
 <span id="kernel_selector_widget" class="pull-right dropdown">
   <img id="current_kernel_logo"/>
   <button class="dropdown-toggle btn btn-sm navbar-btn" data-toggle="dropdown" type='button' id="current_kernel_spec">
     <span class='kernel_name'>Kernel</span>
     <span class="caret"></span> 
   </button>
   <ul id="kernel_selector" class="dropdown-menu">
   </ul>
 </span>
 
 {% endblock headercontainer %}
 
 {% block header %}
 <div id="menubar-container" class="container">
 <div id="menubar">
     <div id="menus" class="navbar navbar-default" role="navigation">
         <div class="container-fluid">
             <button type="button" class="btn btn-default navbar-btn navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
               <i class="fa fa-bars"></i>
               <span class="navbar-text">Menu</span>
             </button>
             <p id="kernel_indicator" class="navbar-text">
               <i id="kernel_indicator_icon"></i>
             </p>
             <p id="modal_indicator" class="navbar-text">
               <i id="modal_indicator_icon"></i>
             </p>
             <span id="notification_area"></span>
             <div class="navbar-collapse collapse">
               <ul class="nav navbar-nav">
                 <li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">File</a>
                     <ul id="file_menu" class="dropdown-menu">
                         <li id="new_notebook"
                             title="Make a new notebook (Opens a new window)">
                             <a href="#">New</a></li>
                         <li id="open_notebook"
                             title="Opens a new window with the Dashboard view">
                             <a href="#">Open...</a></li>
                         <!-- <hr/> -->
                         <li class="divider"></li>
                         <li id="copy_notebook"
                             title="Open a copy of this notebook's contents and start a new kernel">
                             <a href="#">Make a Copy...</a></li>
                         <li id="rename_notebook"><a href="#">Rename...</a></li>
                         <li id="save_checkpoint"><a href="#">Save and Checkpoint</a></li>
                         <!-- <hr/> -->
                         <li class="divider"></li>
                         <li id="restore_checkpoint" class="dropdown-submenu"><a href="#">Revert to Checkpoint</a>
                           <ul class="dropdown-menu">
                             <li><a href="#"></a></li>
                             <li><a href="#"></a></li>
                             <li><a href="#"></a></li>
                             <li><a href="#"></a></li>
                             <li><a href="#"></a></li>
                           </ul>
                         </li>
                         <li class="divider"></li>
                         <li id="print_preview"><a href="#">Print Preview</a></li>
                         <li class="dropdown-submenu"><a href="#">Download as</a>
                             <ul class="dropdown-menu">
                                 <li id="download_ipynb"><a href="#">IPython Notebook (.ipynb)</a></li>
                                 <li id="download_script"><a href="#">Script</a></li>
                                 <li id="download_html"><a href="#">HTML (.html)</a></li>
                                 <li id="download_rst"><a href="#">reST (.rst)</a></li>
                                 <li id="download_pdf"><a href="#">PDF (.pdf)</a></li>
                             </ul>
                         </li>
                         <li class="divider"></li>
                         <li id="trust_notebook"
                             title="Trust the output of this notebook">
                             <a href="#" >Trust Notebook</a></li>
                         <li class="divider"></li>
                         <li id="kill_and_exit"
                             title="Shutdown this notebook's kernel, and close this window">
                             <a href="#" >Close and halt</a></li>
                     </ul>
                 </li>
                 <li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">Edit</a>
                     <ul id="edit_menu" class="dropdown-menu">
                         <li id="cut_cell"><a href="#">Cut Cell</a></li>
                         <li id="copy_cell"><a href="#">Copy Cell</a></li>
                         <li id="paste_cell_above" class="disabled"><a href="#">Paste Cell Above</a></li>
                         <li id="paste_cell_below" class="disabled"><a href="#">Paste Cell Below</a></li>
                         <li id="paste_cell_replace" class="disabled"><a href="#">Paste Cell &amp; Replace</a></li>
                         <li id="delete_cell"><a href="#">Delete Cell</a></li>
                         <li id="undelete_cell" class="disabled"><a href="#">Undo Delete Cell</a></li>
                         <li class="divider"></li>
                         <li id="split_cell"><a href="#">Split Cell</a></li>
                         <li id="merge_cell_above"><a href="#">Merge Cell Above</a></li>
                         <li id="merge_cell_below"><a href="#">Merge Cell Below</a></li>
                         <li class="divider"></li>
                         <li id="move_cell_up"><a href="#">Move Cell Up</a></li>
                         <li id="move_cell_down"><a href="#">Move Cell Down</a></li>
                         <li class="divider"></li>
                         <li id="edit_nb_metadata"><a href="#">Edit Notebook Metadata</a></li>
                     </ul>
                 </li>
                 <li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">View</a>
                     <ul id="view_menu" class="dropdown-menu">
                         <li id="toggle_header"
                             title="Show/Hide the IPython Notebook logo and notebook title (above menu bar)">
                             <a href="#">Toggle Header</a></li>
                         <li id="toggle_toolbar"
                             title="Show/Hide the action icons (below menu bar)">
                             <a href="#">Toggle Toolbar</a></li>
                     </ul>
                 </li>
                 <li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">Insert</a>
                     <ul id="insert_menu" class="dropdown-menu">
                         <li id="insert_cell_above"
                             title="Insert an empty Code cell above the currently active cell">
                             <a href="#">Insert Cell Above</a></li>
                         <li id="insert_cell_below"
                             title="Insert an empty Code cell below the currently active cell">
                             <a href="#">Insert Cell Below</a></li>
                     </ul>
                 </li>
                 <li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">Cell</a>
                     <ul id="cell_menu" class="dropdown-menu">
                         <li id="run_cell" title="Run this cell, and move cursor to the next one">
                             <a href="#">Run</a></li>
                         <li id="run_cell_select_below" title="Run this cell, select below">
                             <a href="#">Run and Select Below</a></li>
                         <li id="run_cell_insert_below" title="Run this cell, insert below">
                             <a href="#">Run and Insert Below</a></li>
                         <li id="run_all_cells" title="Run all cells in the notebook">
                             <a href="#">Run All</a></li>
                         <li id="run_all_cells_above" title="Run all cells above (but not including) this cell">
                             <a href="#">Run All Above</a></li>
                         <li id="run_all_cells_below" title="Run this cell and all cells below it">
                             <a href="#">Run All Below</a></li>
                         <li class="divider"></li>
                         <li id="change_cell_type" class="dropdown-submenu"
                             title="All cells in the notebook have a cell type. By default, new cells are created as 'Code' cells">
                             <a href="#">Cell Type</a>
                             <ul class="dropdown-menu">
                               <li id="to_code"
                                   title="Contents will be sent to the kernel for execution, and output will display in the footer of cell">
                                   <a href="#">Code</a></li>
                               <li id="to_markdown"
                                   title="Contents will be rendered as HTML and serve as explanatory text">
                                   <a href="#">Markdown</a></li>
                               <li id="to_raw"
                                   title="Contents will pass through nbconvert unmodified">
                                   <a href="#">Raw NBConvert</a></li>
                             </ul>
                         </li>
                         <li class="divider"></li>
                         <li id="current_outputs" class="dropdown-submenu"><a href="#">Current Output</a>
                             <ul class="dropdown-menu">
                                 <li id="toggle_current_output"
                                     title="Hide/Show the output of the current cell">
                                     <a href="#">Toggle</a>
                                 </li>
                                 <li id="toggle_current_output_scroll"
                                     title="Scroll the output of the current cell">
                                     <a href="#">Toggle Scrolling</a>
                                 </li>
                                 <li id="clear_current_output"
                                     title="Clear the output of the current cell">
                                     <a href="#">Clear</a>
                                 </li>
                             </ul>
                         </li>
                         <li id="all_outputs" class="dropdown-submenu"><a href="#">All Output</a>
                             <ul class="dropdown-menu">
                                 <li id="toggle_all_output"
                                     title="Hide/Show the output of all cells">
                                     <a href="#">Toggle</a>
                                 </li>
                                 <li id="toggle_all_output_scroll"
                                     title="Scroll the output of all cells">
                                     <a href="#">Toggle Scrolling</a>
                                 </li>
                                 <li id="clear_all_output"
                                     title="Clear the output of all cells">
                                     <a href="#">Clear</a>
                                 </li>
                             </ul>
                         </li>
                     </ul>
                 </li>
                 <li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">Kernel</a>
                     <ul id="kernel_menu" class="dropdown-menu">
                         <li id="int_kernel"
                             title="Send KeyboardInterrupt (CTRL-C) to the Kernel">
                             <a href="#">Interrupt</a>
                         </li>
                         <li id="restart_kernel"
                             title="Restart the Kernel">
                             <a href="#">Restart</a>
                         </li>
                         <li id="reconnect_kernel"
                             title="Reconnect to the Kernel">
                             <a href="#">Reconnect</a>
                         </li>
                         <li class="divider"></li>
                         <li id="menu-change-kernel" class="dropdown-submenu">
                             <a href="#">Change kernel</a>
                             <ul class="dropdown-menu" id="menu-change-kernel-submenu"></ul>
                         </li>
                     </ul>
                 </li>
                 <li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">Help</a>
                     <ul  id="help_menu" class="dropdown-menu">
                         <li id="notebook_tour" title="A quick tour of the notebook user interface"><a href="#">User Interface Tour</a></li>
                         <li id="keyboard_shortcuts" title="Opens a tooltip with all keyboard shortcuts"><a href="#">Keyboard Shortcuts</a></li>
                         <li class="divider"></li>
                         {% set
                             sections = (
                                 (
                                     ("http://ipython.org/documentation.html","IPython Help",True),
                                     ("http://nbviewer.ipython.org/github/ipython/ipython/tree/2.x/examples/Index.ipynb", "Notebook Help", True),
                                 ),(
                                     ("http://docs.python.org","Python",True),
                                     ("http://help.github.com/articles/github-flavored-markdown","Markdown",True),
                                     ("http://docs.scipy.org/doc/numpy/reference/","NumPy",True),
                                     ("http://docs.scipy.org/doc/scipy/reference/","SciPy",True),
                                     ("http://matplotlib.org/contents.html","Matplotlib",True),
                                     ("http://docs.sympy.org/latest/index.html","SymPy",True),
                                     ("http://pandas.pydata.org/pandas-docs/stable/","pandas", True)
                                 )
                             )
                         %}
 
                         {% for helplinks in sections %}
                             {% for link in helplinks %}
                                 <li><a href="{{link[0]}}" {{'target="_blank" title="Opens in a new window"' if link[2]}}>
                                 {{'<i class="fa fa-external-link menu-icon pull-right"></i>' if link[2]}}
                                 {{link[1]}}
                                 </a></li>
                             {% endfor %}
                             {% if not loop.last %}
                                 <li class="divider"></li>
                             {% endif %}
                         {% endfor %}
                         <li class="divider"></li>
                         <li title="About IPython Notebook"><a id="notebook_about" href="#">About</a></li>
                     </ul>
                 </li>
               </ul>
             </div>
         </div>
     </div>
 </div>
 
 <div id="maintoolbar" class="navbar">
   <div class="toolbar-inner navbar-inner navbar-nobg">
     <div id="maintoolbar-container" class="container"></div>
   </div>
 </div>
 </div>
 
 <div class="lower-header-bar"></div>
 {% endblock header %}
 
 {% block site %}
 
 
 <div id="ipython-main-app">
     <div id="notebook_panel">
         <div id="notebook"></div>
     </div>
 </div>
 
 <div id="pager">
     <div id="pager-contents">
         <div id="pager-container" class="container"></div>
     </div>
     <div id='pager-button-area'></div>
 </div>
 
 <div id='tooltip' class='ipython_tooltip' style='display:none'></div>
 
 
 {% endblock %}
 
 
 {% block script %}
 {{super()}}
 <script type="text/javascript">
     sys_info = {{sys_info}};
 </script>
 
 <script src="{{ static_url("components/text-encoding/lib/encoding.js") }}" charset="utf-8"></script>
 
 <script src="{{ static_url("notebook/js/main.js") }}" charset="utf-8"></script>
 
 {% endblock %}

IPython/html/templates/page.html

@@ -1,119 +1,120 b''
 <!DOCTYPE HTML>
 <html>
 
 <head>
     <meta charset="utf-8">
 
     <title>{% block title %}IPython Notebook{% endblock %}</title>
     {% block favicon %}<link rel="shortcut icon" type="image/x-icon" href="{{static_url("base/images/favicon.ico") }}">{% endblock %}
     <meta http-equiv="X-UA-Compatible" content="chrome=1">
     <link rel="stylesheet" href="{{static_url("components/jquery-ui/themes/smoothness/jquery-ui.min.css") }}" type="text/css" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     
     {% block stylesheet %}
     <link rel="stylesheet" href="{{ static_url("style/style.min.css") }}" type="text/css"/>
     {% endblock %}
     <link rel="stylesheet" href="{{ static_url("custom/custom.css") }}" type="text/css" />
     <script src="{{static_url("components/es6-promise/promise.min.js")}}" type="text/javascript" charset="utf-8"></script>
     <script src="{{static_url("components/requirejs/require.js") }}" type="text/javascript" charset="utf-8"></script>
     <script>
       require.config({
           {% if version_hash %}
           urlArgs: "v={{version_hash}}",
           {% endif %}
           baseUrl: '{{static_url("", include_version=False)}}',
           paths: {
             nbextensions : '{{ base_url }}nbextensions',
+            kernelspecs : '{{ base_url }}kernelspecs',
             underscore : 'components/underscore/underscore-min',
             backbone : 'components/backbone/backbone-min',
             jquery: 'components/jquery/jquery.min',
             bootstrap: 'components/bootstrap/js/bootstrap.min',
             bootstraptour: 'components/bootstrap-tour/build/js/bootstrap-tour.min',
             jqueryui: 'components/jquery-ui/ui/minified/jquery-ui.min',
             moment: 'components/moment/moment',
             codemirror: 'components/codemirror',
             termjs: 'components/term.js/src/term',
           },
           shim: {
             underscore: {
               exports: '_'
             },
             backbone: {
               deps: ["underscore", "jquery"],
               exports: "Backbone"
             },
             bootstrap: {
               deps: ["jquery"],
               exports: "bootstrap"
             },
             bootstraptour: {
               deps: ["bootstrap"],
               exports: "Tour"
             },
             jqueryui: {
               deps: ["jquery"],
               exports: "$"
             }
           }
       });
 
       require.config({
           map: {
               '*':{
                 'contents': '{{ contents_js_source }}',
               }
           }
       });
     </script>
 
     {% block meta %}
     {% endblock %}
 
 </head>
 
 <body {% block params %}{% endblock %}>
 
 <noscript>
     <div id='noscript'>
       IPython Notebook requires JavaScript.<br>
       Please enable it to proceed.
   </div>
 </noscript>
 
 <div id="header" class="navbar navbar-fixed-top">
   <div id="header-container" class="container">
   <div id="ipython_notebook" class="nav navbar-brand pull-left"><a href="{{base_url}}tree" alt='dashboard'>{% block logo %}<img src='{{static_url("base/images/logo.png") }}' alt='Jupyter Notebook'/>{% endblock %}</a></div>
 
   {% block login_widget %}
 
     <span id="login_widget">
       {% if logged_in %}
         <button id="logout" class="btn btn-sm navbar-btn">Logout</button>
       {% elif login_available and not logged_in %}
         <button id="login" class="btn btn-sm navbar-btn">Login</button>
       {% endif %}
     </span>
 
   {% endblock %}
 
   {% block headercontainer %}
   {% endblock %}
   </div>
   <div class="header-bar"></div>
 
   {% block header %}
   {% endblock %}
 </div>
 <div id="header-spacer"></div>
 
 <div id="site">
 {% block site %}
 {% endblock %}
 </div>
 
 {% block script %}
 {% endblock %}
 
 </body>
 
 </html>