Merge pull request #5844 from jdfreder/scrollmanager

'Paul' scroll feature

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

@@ -0,0 +1,193
+// Copyright (c) IPython Development Team.
+// Distributed under the terms of the Modified BSD License.
+define(['jquery'], function($){
+    "use strict";
+
+    var ScrollManager = function(notebook, options) {
+        // Public constructor.
+        this.notebook = notebook;
+        options = options || {};
+        this.animation_speed = options.animation_speed || 250; //ms
+    };
+
+    ScrollManager.prototype.scroll = function (delta) {
+        // Scroll the document.
+        //
+        // Parameters
+        // ----------
+        // delta: integer
+        //  direction to scroll the document.  Positive is downwards. 
+        //  Unit is one page length.
+        this.scroll_some(delta);
+        return false;
+    };
+
+    ScrollManager.prototype.scroll_to = function(selector) {
+        // Scroll to an element in the notebook.
+        $('#notebook').animate({'scrollTop': $(selector).offset().top + $('#notebook').scrollTop() - $('#notebook').offset().top}, this.animation_speed);
+    };
+
+    ScrollManager.prototype.scroll_some = function(pages) {
+        // Scroll up or down a given number of pages.
+        //
+        // Parameters
+        // ----------
+        // pages: integer
+        //  number of pages to scroll the document, may be positive or negative.
+        $('#notebook').animate({'scrollTop': $('#notebook').scrollTop() + pages * $('#notebook').height()}, this.animation_speed);
+    };
+
+    ScrollManager.prototype.get_first_visible_cell = function() {
+        // Gets the index of the first visible cell in the document.
+
+        // First, attempt to be smart by guessing the index of the cell we are
+        // scrolled to.  Then, walk from there up or down until the right cell 
+        // is found.  To guess the index, get the top of the last cell, and
+        // divide that by the number of cells to get an average cell height.  
+        // Then divide the scroll height by the average cell height.
+        var cell_count = this.notebook.ncells();
+        var first_cell_top = this.notebook.get_cell(0).element.offset().top;
+        var last_cell_top = this.notebook.get_cell(cell_count-1).element.offset().top;
+        var avg_cell_height = (last_cell_top - first_cell_top) / cell_count;
+        var notebook = $('#notebook');
+        var i = Math.ceil(notebook.scrollTop() / avg_cell_height);
+        i = Math.min(Math.max(i , 0), cell_count - 1);
+
+        while (this.notebook.get_cell(i).element.offset().top - first_cell_top < notebook.scrollTop() && i < cell_count - 1) {
+            i += 1;
+        } 
+
+        while (this.notebook.get_cell(i).element.offset().top - first_cell_top > notebook.scrollTop() - 50 && i >= 0) {
+            i -= 1;
+        } 
+        return Math.min(i + 1, cell_count - 1);
+    };
+
+
+    var TargetScrollManager = function(notebook, options) {
+        // Public constructor.
+        ScrollManager.apply(this, [notebook, options]);
+    };
+    TargetScrollManager.prototype = new ScrollManager();
+
+    TargetScrollManager.prototype.is_target = function (index) {
+        // Check if a cell should be a scroll stop.
+        //
+        // Returns `true` if the cell is a cell that the scroll manager
+        // should scroll to.  Otherwise, false is returned. 
+        //
+        // Parameters
+        // ----------
+        // index: integer
+        //  index of the cell to test.
+        return false;
+    };
+
+    TargetScrollManager.prototype.scroll = function (delta) {
+        // Scroll the document.
+        //
+        // Parameters
+        // ----------
+        // delta: integer
+        //  direction to scroll the document.  Positive is downwards.
+        //  Units are targets.
+
+        // Try to scroll to the next slide.
+        var cell_count = this.notebook.ncells();
+        var selected_index = this.get_first_visible_cell() + delta;
+        while (0 <= selected_index && selected_index < cell_count && !this.is_target(selected_index)) {
+            selected_index += delta;
+        }
+
+        if (selected_index < 0 || cell_count <= selected_index) {
+            return ScrollManager.prototype.scroll.apply(this, [delta]);
+        } else {
+            this.scroll_to(this.notebook.get_cell(selected_index).element);
+            
+            // Cancel browser keyboard scroll.
+            return false;
+        }
+    };
+
+
+    var SlideScrollManager = function(notebook, options) {
+        // Public constructor.
+        TargetScrollManager.apply(this, [notebook, options]);
+    };
+    SlideScrollManager.prototype = new TargetScrollManager();
+
+    SlideScrollManager.prototype.is_target = function (index) {
+        var cell = this.notebook.get_cell(index);
+        return cell.metadata && cell.metadata.slideshow && 
+            cell.metadata.slideshow.slide_type && 
+            (cell.metadata.slideshow.slide_type === "slide" ||
+            cell.metadata.slideshow.slide_type === "subslide");
+    };
+
+
+    var HeadingScrollManager = function(notebook, options) {
+        // Public constructor.
+        ScrollManager.apply(this, [notebook, options]);
+        options = options || {};
+        this._level = options.heading_level || 1;
+    };
+    HeadingScrollManager.prototype = new ScrollManager();
+
+    HeadingScrollManager.prototype.scroll = function (delta) {
+        // Scroll the document.
+        //
+        // Parameters
+        // ----------
+        // delta: integer
+        //  direction to scroll the document.  Positive is downwards.
+        //  Units are headers.
+
+        // Get all of the header elements that match the heading level or are of
+        // greater magnitude (a smaller header number).
+        var headers = $();
+        var i;
+        for (i = 1; i <= this._level; i++) {
+            headers = headers.add('#notebook-container h' + i);
+        }
+
+        // Find the header the user is on or below.
+        var first_cell_top = this.notebook.get_cell(0).element.offset().top;
+        var notebook = $('#notebook');
+        var current_scroll = notebook.scrollTop();
+        var header_scroll = 0;
+        i = -1;
+        while (current_scroll >= header_scroll && i < headers.length) {
+            if (++i < headers.length) {
+                header_scroll = $(headers[i]).offset().top - first_cell_top;
+            }
+        }
+        i--;
+
+        // Check if the user is below the header.
+        if (i < 0 || current_scroll > $(headers[i]).offset().top - first_cell_top + 30) {
+            // Below the header, count the header as a target.
+            if (delta < 0) {
+                delta += 1;
+            }
+        }
+        i += delta;
+
+        // Scroll!
+        if (0 <= i && i < headers.length) {
+            this.scroll_to(headers[i]);
+            return false;
+        } else {
+            // Default to the base's scroll behavior when target header doesn't
+            // exist.
+            return ScrollManager.prototype.scroll.apply(this, [delta]);
+        }
+    };
+
+    // Return naemspace for require.js loads
+    return {
+        'ScrollManager': ScrollManager,
+        'SlideScrollManager': SlideScrollManager,
+        'HeadingScrollManager': HeadingScrollManager,
+        'TargetScrollManager': TargetScrollManager
+    };
+});

docs/source/whatsnew/pr/paul-scroll.rst

@@ -0,0 +1,1
+* A ScrollManager was added to the notebook.  The ScrollManager controls how the notebook document is scrolled using keyboard.  Users can inherit from the ScrollManager or TargetScrollManager to customize how their notebook scrolls.  The default ScrollManager is the SlideScrollManager, which tries to scroll to the nearest slide or sub-slide cell.

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

@@ -1,566 +1,578
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     'base/js/namespace',
     'jquery',
     'base/js/utils',
     'base/js/keyboard',
 ], function(IPython, $, utils, keyboard) {
     "use strict";
     
     var browser = utils.browser[0];
     var platform = utils.platform;
 
     // Main keyboard manager for the notebook
     var keycodes = keyboard.keycodes;
 
     var KeyboardManager = function (options) {
         // Constructor
         //
         // Parameters:
         //  options: dictionary
         //      Dictionary of keyword arguments.
         //          events: $(Events) instance
         //          pager: Pager instance
         this.mode = 'command';
         this.enabled = true;
         this.pager = options.pager;
         this.quick_help = undefined;
         this.notebook = undefined;
         this.bind_events();
         this.command_shortcuts = new keyboard.ShortcutManager(undefined, options.events);
         this.command_shortcuts.add_shortcuts(this.get_default_common_shortcuts());
         this.command_shortcuts.add_shortcuts(this.get_default_command_shortcuts());
         this.edit_shortcuts = new keyboard.ShortcutManager(undefined, options.events);
         this.edit_shortcuts.add_shortcuts(this.get_default_common_shortcuts());
         this.edit_shortcuts.add_shortcuts(this.get_default_edit_shortcuts());
     };
 
     KeyboardManager.prototype.get_default_common_shortcuts = function() {
         var that = this;
         var shortcuts = {
             'shift' : {
                 help    : '',
                 help_index : '',
                 handler : function (event) {
                     // ignore shift keydown
                     return true;
                 }
             },
             'shift-enter' : {
                 help    : 'run cell, select below',
                 help_index : 'ba',
                 handler : function (event) {
                     that.notebook.execute_cell_and_select_below();
                     return false;
                 }
             },
             'ctrl-enter' : {
                 help    : 'run cell',
                 help_index : 'bb',
                 handler : function (event) {
                     that.notebook.execute_cell();
                     return false;
                 }
             },
             'alt-enter' : {
                 help    : 'run cell, insert below',
                 help_index : 'bc',
                 handler : function (event) {
                     that.notebook.execute_cell_and_insert_below();
                     return false;
                 }
             }
         };
 
         if (platform === 'MacOS') {
             shortcuts['cmd-s'] =
                 {
                     help    : 'save notebook',
                     help_index : 'fb',
                     handler : function (event) {
                         that.notebook.save_checkpoint();
                         event.preventDefault();
                         return false;
                     }
                 };
         } else {
             shortcuts['ctrl-s'] =
                 {
                     help    : 'save notebook',
                     help_index : 'fb',
                     handler : function (event) {
                         that.notebook.save_checkpoint();
                         event.preventDefault();
                         return false;
                     }
                 };
         }
         return shortcuts;
     };
 
     KeyboardManager.prototype.get_default_edit_shortcuts = function() {
         var that = this;
         return {
             'esc' : {
                 help    : 'command mode',
                 help_index : 'aa',
                 handler : function (event) {
                     that.notebook.command_mode();
                     return false;
                 }
             },
             'ctrl-m' : {
                 help    : 'command mode',
                 help_index : 'ab',
                 handler : function (event) {
                     that.notebook.command_mode();
                     return false;
                 }
             },
             'up' : {
                 help    : '',
                 help_index : '',
                 handler : function (event) {
                     var index = that.notebook.get_selected_index();
                     var cell = that.notebook.get_cell(index);
                     if (cell && cell.at_top() && index !== 0) {
                         event.preventDefault();
                         that.notebook.command_mode();
                         that.notebook.select_prev();
                         that.notebook.edit_mode();
                         var cm = that.notebook.get_selected_cell().code_mirror;
                         cm.setCursor(cm.lastLine(), 0);
                         return false;
                     } else if (cell) {
                         var cm = cell.code_mirror;
                         cm.execCommand('goLineUp');
                         return false;
                     }
                 }
             },
             'down' : {
                 help    : '',
                 help_index : '',
                 handler : function (event) {
                     var index = that.notebook.get_selected_index();
                     var cell = that.notebook.get_cell(index);
                     if (cell.at_bottom() && index !== (that.notebook.ncells()-1)) {
                         event.preventDefault();
                         that.notebook.command_mode();
                         that.notebook.select_next();
                         that.notebook.edit_mode();
                         var cm = that.notebook.get_selected_cell().code_mirror;
                         cm.setCursor(0, 0);
                         return false;
                     } else {
                         var cm = cell.code_mirror;
                         cm.execCommand('goLineDown');
                         return false;
                     }
                 }
             },
             'ctrl-shift--' : {
                 help    : 'split cell',
                 help_index : 'ea',
                 handler : function (event) {
                     that.notebook.split_cell();
                     return false;
                 }
             },
             'ctrl-shift-subtract' : {
                 help    : '',
                 help_index : 'eb',
                 handler : function (event) {
                     that.notebook.split_cell();
                     return false;
                 }
             },
         };
     };
 
     KeyboardManager.prototype.get_default_command_shortcuts = function() {
         var that = this;
         return {
+            'space': {
+                help: "Scroll down",
+                handler: function(event) {
+                    return that.notebook.scroll_manager.scroll(1);
+                },
+            },
+            'shift-space': {
+                help: "Scroll up",
+                handler: function(event) {
+                    return that.notebook.scroll_manager.scroll(-1);
+                },
+            },
             'enter' : {
                 help    : 'edit mode',
                 help_index : 'aa',
                 handler : function (event) {
                     that.notebook.edit_mode();
                     return false;
                 }
             },
             'up' : {
                 help    : 'select previous cell',
                 help_index : 'da',
                 handler : function (event) {
                     var index = that.notebook.get_selected_index();
                     if (index !== 0 && index !== null) {
                         that.notebook.select_prev();
                         that.notebook.focus_cell();
                     }
                     return false;
                 }
             },
             'down' : {
                 help    : 'select next cell',
                 help_index : 'db',
                 handler : function (event) {
                     var index = that.notebook.get_selected_index();
                     if (index !== (that.notebook.ncells()-1) && index !== null) {
                         that.notebook.select_next();
                         that.notebook.focus_cell();
                     }
                     return false;
                 }
             },
             'k' : {
                 help    : 'select previous cell',
                 help_index : 'dc',
                 handler : function (event) {
                     var index = that.notebook.get_selected_index();
                     if (index !== 0 && index !== null) {
                         that.notebook.select_prev();
                         that.notebook.focus_cell();
                     }
                     return false;
                 }
             },
             'j' : {
                 help    : 'select next cell',
                 help_index : 'dd',
                 handler : function (event) {
                     var index = that.notebook.get_selected_index();
                     if (index !== (that.notebook.ncells()-1) && index !== null) {
                         that.notebook.select_next();
                         that.notebook.focus_cell();
                     }
                     return false;
                 }
             },
             'x' : {
                 help    : 'cut cell',
                 help_index : 'ee',
                 handler : function (event) {
                     that.notebook.cut_cell();
                     return false;
                 }
             },
             'c' : {
                 help    : 'copy cell',
                 help_index : 'ef',
                 handler : function (event) {
                     that.notebook.copy_cell();
                     return false;
                 }
             },
             'shift-v' : {
                 help    : 'paste cell above',
                 help_index : 'eg',
                 handler : function (event) {
                     that.notebook.paste_cell_above();
                     return false;
                 }
             },
             'v' : {
                 help    : 'paste cell below',
                 help_index : 'eh',
                 handler : function (event) {
                     that.notebook.paste_cell_below();
                     return false;
                 }
             },
             'd' : {
                 help    : 'delete cell (press twice)',
                 help_index : 'ej',
                 count: 2,
                 handler : function (event) {
                     that.notebook.delete_cell();
                     return false;
                 }
             },
             'a' : {
                 help    : 'insert cell above',
                 help_index : 'ec',
                 handler : function (event) {
                     that.notebook.insert_cell_above();
                     that.notebook.select_prev();
                     that.notebook.focus_cell();
                     return false;
                 }
             },
             'b' : {
                 help    : 'insert cell below',
                 help_index : 'ed',
                 handler : function (event) {
                     that.notebook.insert_cell_below();
                     that.notebook.select_next();
                     that.notebook.focus_cell();
                     return false;
                 }
             },
             'y' : {
                 help    : 'to code',
                 help_index : 'ca',
                 handler : function (event) {
                     that.notebook.to_code();
                     return false;
                 }
             },
             'm' : {
                 help    : 'to markdown',
                 help_index : 'cb',
                 handler : function (event) {
                     that.notebook.to_markdown();
                     return false;
                 }
             },
             'r' : {
                 help    : 'to raw',
                 help_index : 'cc',
                 handler : function (event) {
                     that.notebook.to_raw();
                     return false;
                 }
             },
             '1' : {
                 help    : 'to heading 1',
                 help_index : 'cd',
                 handler : function (event) {
                     that.notebook.to_heading(undefined, 1);
                     return false;
                 }
             },
             '2' : {
                 help    : 'to heading 2',
                 help_index : 'ce',
                 handler : function (event) {
                     that.notebook.to_heading(undefined, 2);
                     return false;
                 }
             },
             '3' : {
                 help    : 'to heading 3',
                 help_index : 'cf',
                 handler : function (event) {
                     that.notebook.to_heading(undefined, 3);
                     return false;
                 }
             },
             '4' : {
                 help    : 'to heading 4',
                 help_index : 'cg',
                 handler : function (event) {
                     that.notebook.to_heading(undefined, 4);
                     return false;
                 }
             },
             '5' : {
                 help    : 'to heading 5',
                 help_index : 'ch',
                 handler : function (event) {
                     that.notebook.to_heading(undefined, 5);
                     return false;
                 }
             },
             '6' : {
                 help    : 'to heading 6',
                 help_index : 'ci',
                 handler : function (event) {
                     that.notebook.to_heading(undefined, 6);
                     return false;
                 }
             },
             'o' : {
                 help    : 'toggle output',
                 help_index : 'gb',
                 handler : function (event) {
                     that.notebook.toggle_output();
                     return false;
                 }
             },
             'shift-o' : {
                 help    : 'toggle output scrolling',
                 help_index : 'gc',
                 handler : function (event) {
                     that.notebook.toggle_output_scroll();
                     return false;
                 }
             },
             's' : {
                 help    : 'save notebook',
                 help_index : 'fa',
                 handler : function (event) {
                     that.notebook.save_checkpoint();
                     return false;
                 }
             },
             'ctrl-j' : {
                 help    : 'move cell down',
                 help_index : 'eb',
                 handler : function (event) {
                     that.notebook.move_cell_down();
                     return false;
                 }
             },
             'ctrl-k' : {
                 help    : 'move cell up',
                 help_index : 'ea',
                 handler : function (event) {
                     that.notebook.move_cell_up();
                     return false;
                 }
             },
             'l' : {
                 help    : 'toggle line numbers',
                 help_index : 'ga',
                 handler : function (event) {
                     that.notebook.cell_toggle_line_numbers();
                     return false;
                 }
             },
             'i' : {
                 help    : 'interrupt kernel (press twice)',
                 help_index : 'ha',
                 count: 2,
                 handler : function (event) {
                     that.notebook.kernel.interrupt();
                     return false;
                 }
             },
             '0' : {
                 help    : 'restart kernel (press twice)',
                 help_index : 'hb',
                 count: 2,
                 handler : function (event) {
                     that.notebook.restart_kernel();
                     return false;
                 }
             },
             'h' : {
                 help    : 'keyboard shortcuts',
                 help_index : 'ge',
                 handler : function (event) {
                     that.quick_help.show_keyboard_shortcuts();
                     return false;
                 }
             },
             'z' : {
                 help    : 'undo last delete',
                 help_index : 'ei',
                 handler : function (event) {
                     that.notebook.undelete_cell();
                     return false;
                 }
             },
             'shift-m' : {
                 help    : 'merge cell below',
                 help_index : 'ek',
                 handler : function (event) {
                     that.notebook.merge_cell_below();
                     return false;
                 }
             },
             'q' : {
                 help    : 'close pager',
                 help_index : 'gd',
                 handler : function (event) {
                     that.pager.collapse();
                     return false;
                 }
             },
         };
     };
 
     KeyboardManager.prototype.bind_events = function () {
         var that = this;
         $(document).keydown(function (event) {
             return that.handle_keydown(event);
         });
     };
 
     KeyboardManager.prototype.handle_keydown = function (event) {
         var notebook = this.notebook;
 
         if (event.which === keycodes.esc) {
             // Intercept escape at highest level to avoid closing
             // websocket connection with firefox
             event.preventDefault();
         }
         
         if (!this.enabled) {
             if (event.which === keycodes.esc) {
                 // ESC
                 notebook.command_mode();
                 return false;
             }
             return true;
         }
         
         if (this.mode === 'edit') {
             return this.edit_shortcuts.call_handler(event);
         } else if (this.mode === 'command') {
             return this.command_shortcuts.call_handler(event);
         }
         return true;
     };
 
     KeyboardManager.prototype.edit_mode = function () {
         this.last_mode = this.mode;
         this.mode = 'edit';
     };
 
     KeyboardManager.prototype.command_mode = function () {
         this.last_mode = this.mode;
         this.mode = 'command';
     };
 
     KeyboardManager.prototype.enable = function () {
         this.enabled = true;
     };
 
     KeyboardManager.prototype.disable = function () {
         this.enabled = false;
     };
 
     KeyboardManager.prototype.register_events = function (e) {
         var that = this;
         var handle_focus = function () {
             that.disable();
         };
         var handle_blur = function () {
             that.enable();
         };
         e.on('focusin', handle_focus);
         e.on('focusout', handle_blur);
         // TODO: Very strange. The focusout event does not seem fire for the 
         // bootstrap textboxes on FF25&26...  This works around that by 
         // registering focus and blur events recursively on all inputs within
         // registered element.
         e.find('input').blur(handle_blur);
         e.on('DOMNodeInserted', function (event) {
             var target = $(event.target);
             if (target.is('input')) {
                 target.blur(handle_blur);
             } else {
                 target.find('input').blur(handle_blur);    
             }
           });
         // There are times (raw_input) where we remove the element from the DOM before
         // focusout is called. In this case we bind to the remove event of jQueryUI,
         // which gets triggered upon removal, iff it is focused at the time.
         // is_focused must be used to check for the case where an element within
         // the element being removed is focused.
         e.on('remove', function () {
             if (utils.is_focused(e[0])) {
                 that.enable();
             }
         });
     };
 
     // For backwards compatability.
     IPython.KeyboardManager = KeyboardManager;
 
     return {'KeyboardManager': KeyboardManager};
 });

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

@@ -1,228 +1,226
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     'base/js/namespace',
     'jquery',
     'notebook/js/toolbar',
     'notebook/js/celltoolbar',
 ], function(IPython, $, toolbar, celltoolbar) {
     "use strict";
 
     var MainToolBar = function (selector, options) {
         // Constructor
         //
         // Parameters:
         //  selector: string
         //  options: dictionary
         //      Dictionary of keyword arguments.
         //          events: $(Events) instance
         //          notebook: Notebook instance
         toolbar.ToolBar.apply(this, arguments);
         this.events = options.events;
         this.notebook = options.notebook;
         this.construct();
         this.add_celltype_list();
         this.add_celltoolbar_list();
         this.bind_events();
     };
 
     MainToolBar.prototype = new toolbar.ToolBar();
 
     MainToolBar.prototype.construct = function () {
         var that = this;
         this.add_buttons_group([
                 {
                     id : 'save_b',
                     label : 'Save and Checkpoint',
                     icon : 'fa-save',
                     callback : function () {
                         that.notebook.save_checkpoint();
                         }
                 }
             ]);
 
         this.add_buttons_group([
                 {
                     id : 'insert_below_b',
                     label : 'Insert Cell Below',
                     icon : 'fa-plus',
                     callback : function () {
                         that.notebook.insert_cell_below('code');
                         that.notebook.select_next();
                         that.notebook.focus_cell();
                         }
                 }
             ],'insert_above_below');
 
         this.add_buttons_group([
                 {
                     id : 'cut_b',
                     label : 'Cut Cell',
                     icon : 'fa-cut',
                     callback : function () {
                         that.notebook.cut_cell();
                         }
                 },
                 {
                     id : 'copy_b',
                     label : 'Copy Cell',
                     icon : 'fa-copy',
                     callback : function () {
                         that.notebook.copy_cell();
                         }
                 },
                 {
                     id : 'paste_b',
                     label : 'Paste Cell Below',
                     icon : 'fa-paste',
                     callback : function () {
                         that.notebook.paste_cell_below();
                         }
                 }
             ],'cut_copy_paste');
 
         this.add_buttons_group([
                 {
                     id : 'move_up_b',
                     label : 'Move Cell Up',
                     icon : 'fa-arrow-up',
                     callback : function () {
                         that.notebook.move_cell_up();
                         }
                 },
                 {
                     id : 'move_down_b',
                     label : 'Move Cell Down',
                     icon : 'fa-arrow-down',
                     callback : function () {
                         that.notebook.move_cell_down();
                         }
                 }
             ],'move_up_down');
         
 
         this.add_buttons_group([
                 {
                     id : 'run_b',
                     label : 'Run Cell',
                     icon : 'fa-play',
                     callback : function () {
                         // emulate default shift-enter behavior
                         that.notebook.execute_cell_and_select_below();
                     }
                 },
                 {
                     id : 'interrupt_b',
                     label : 'Interrupt',
                     icon : 'fa-stop',
                     callback : function () {
                         that.notebook.session.interrupt_kernel();
                         }
                 },
                 {
                     id : 'repeat_b',
                     label : 'Restart Kernel',
                     icon : 'fa-repeat',
                     callback : function () {
                         that.notebook.restart_kernel();
                         }
                 }
             ],'run_int');
     };
     
     MainToolBar.prototype.add_celltype_list = function () {
         this.element
             .append($('<select/>')
                 .attr('id','cell_type')
                 .addClass('form-control select-xs')
                 .append($('<option/>').attr('value','code').text('Code'))
                 .append($('<option/>').attr('value','markdown').text('Markdown'))
                 .append($('<option/>').attr('value','raw').text('Raw NBConvert'))
                 .append($('<option/>').attr('value','heading1').text('Heading 1'))
                 .append($('<option/>').attr('value','heading2').text('Heading 2'))
                 .append($('<option/>').attr('value','heading3').text('Heading 3'))
                 .append($('<option/>').attr('value','heading4').text('Heading 4'))
                 .append($('<option/>').attr('value','heading5').text('Heading 5'))
                 .append($('<option/>').attr('value','heading6').text('Heading 6'))
             );
     };
 
-
     MainToolBar.prototype.add_celltoolbar_list = function () {
         var label = $('<span/>').addClass("navbar-text").text('Cell Toolbar:');
         var select = $('<select/>')
             .attr('id', 'ctb_select')
             .addClass('form-control select-xs')
             .append($('<option/>').attr('value', '').text('None'));
         this.element.append(label).append(select);
         var that = this;
         select.change(function() {
                 var val = $(this).val();
                 if (val ==='') {
                     celltoolbar.CellToolbar.global_hide();
                     delete that.notebook.metadata.celltoolbar;
                 } else {
                     celltoolbar.CellToolbar.global_show();
                     celltoolbar.CellToolbar.activate_preset(val, that.events);
                     that.notebook.metadata.celltoolbar = val;
                 }
             });
         // Setup the currently registered presets.
         var presets = celltoolbar.CellToolbar.list_presets();
         for (var i=0; i<presets.length; i++) {
             var name = presets[i];
             select.append($('<option/>').attr('value', name).text(name));
         }
         // Setup future preset registrations.
         this.events.on('preset_added.CellToolbar', function (event, data) {
             var name = data.name;
             select.append($('<option/>').attr('value', name).text(name));
         });
         // Update select value when a preset is activated.
         this.events.on('preset_activated.CellToolbar', function (event, data) {
             if (select.val() !== data.name)
                 select.val(data.name);
         });
     };
 
-
     MainToolBar.prototype.bind_events = function () {
         var that = this;
         
         this.element.find('#cell_type').change(function () {
             var cell_type = $(this).val();
             if (cell_type === 'code') {
                 that.notebook.to_code();
             } else if (cell_type === 'markdown')  {
                 that.notebook.to_markdown();
             } else if (cell_type === 'raw')  {
                 that.notebook.to_raw();
             } else if (cell_type === 'heading1')  {
                 that.notebook.to_heading(undefined, 1);
             } else if (cell_type === 'heading2')  {
                 that.notebook.to_heading(undefined, 2);
             } else if (cell_type === 'heading3')  {
                 that.notebook.to_heading(undefined, 3);
             } else if (cell_type === 'heading4')  {
                 that.notebook.to_heading(undefined, 4);
             } else if (cell_type === 'heading5')  {
                 that.notebook.to_heading(undefined, 5);
             } else if (cell_type === 'heading6')  {
                 that.notebook.to_heading(undefined, 6);
             }
         });
         this.events.on('selected_cell_type_changed.Notebook', function (event, data) {
             if (data.cell_type === 'heading') {
                 that.element.find('#cell_type').val(data.cell_type+data.level);
             } else {
                 that.element.find('#cell_type').val(data.cell_type);
             }
         });
     };
 
     // Backwards compatability.
     IPython.MainToolBar = MainToolBar;
 
     return {'MainToolBar': MainToolBar};
 });

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

@@ -1,2644 +1,2650
 // 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/textcell',
     'notebook/js/codecell',
     'services/sessions/js/session',
     'notebook/js/celltoolbar',
     'components/marked/lib/marked',
     'highlight',
     '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, 
     textcell, 
     codecell, 
     session, 
     celltoolbar, 
     marked,
     hljs,
     mathjaxutils,
     keyboard,
     tooltip,
     default_celltoolbar,
     rawcell_celltoolbar,
-    slideshow_celltoolbar
+    slideshow_celltoolbar,
+    scrollmanager
     ) {
 
     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
         //          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.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);
+
         // default_kernel_name is a temporary measure while we implement proper
         // kernel selection and delayed start. Do not rely on it.
         this.default_kernel_name = 'python';
         // 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,
                 langPrefix: "language-",
                 highlight: function(code, lang) {
                     if (!lang) {
                         // no language, no highlight
                         return code;
                     }
                     var highlighted;
                     try {
                         highlighted = hljs.highlight(lang, code, false);
                     } catch(err) {
                         highlighted = hljs.highlightAuto(code);
                     }
                     return highlighted.value;
                 }
             });
         }
 
         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;
         // 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;
         // single worksheet for now
         this.worksheet_metadata = {};
         this.notebook_name_blacklist_re = /[\/\\:]/;
         this.nbformat = 3; // Increment this when changing the nbformat
         this.nbformat_minor = 0; // Increment this when changing the nbformat
         this.codemirror_mode = 'ipython';
         this.create_elements();
         this.bind_events();
         this.save_notebook = function() { // don't allow save until notebook_loaded
             this.save_notebook_error(null, null, "Load failed, save is disabled");
         };
 
         // Trigger cell toolbar registration.
         default_celltoolbar.register(this);
         rawcell_celltoolbar.register(this);
         slideshow_celltoolbar.register(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) {
             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('set_dirty.Notebook', function (event, data) {
             that.dirty = data.value;
         });
 
         this.events.on('trust_changed.Notebook', function (event, data) {
             that.trusted = data.value;
         });
 
         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('status_autorestarting.Kernel', function () {
             dialog.modal({
                 notebook: that,
                 keyboard_manager: that.keyboard_manager,
                 title: "Kernel Restarting",
                 body: "The kernel appears to have died. It will restart automatically.",
                 buttons: {
                     OK : {
                         class : "btn-primary"
                     }
                 }
             });
         });
         
         this.events.on('spec_changed.Kernel', function(event, data) {
             that.set_kernelspec_metadata(data);
             if (data.codemirror_mode) {
                 that.set_codemirror_mode(data.codemirror_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.kill_kernel();
             }
             // 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;
         };
     };
 
     /**
      * 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});
     };
     
     Notebook.prototype.set_kernelspec_metadata = function(ks) {
         var tostore = {};
         $.map(ks, function(value, field) {
             if (field !== 'argv' && field !== 'env') {
                 tostore[field] = value;
             }
         });
         this.metadata.kernelspec = tostore;
     }
 
     // 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.children("div.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} A particular cell
      */
     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
      */
     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
      */
     Notebook.prototype.get_prev_cell = function (cell) {
         // TODO: off-by-one
         // nb.get_prev_cell(nb.get_cell(1)) is null
         var result = null;
         var index = this.find_cell_index(cell);
         if (index !== null && index > 1) {
             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
      */
     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_selected_cell();
         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','heading'], 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,
             };
             if (type === 'code') {
                 cell = new codecell.CodeCell(this.kernel, cell_options);
                 cell.set_input_prompt();
             } else if (type === 'markdown') {
                 cell = new textcell.MarkdownCell(cell_options);
             } else if (type === 'raw') {
                 cell = new textcell.RawCell(cell_options);
             } else if (type === 'heading') {
                 cell = new textcell.HeadingCell(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_element = this.get_cell_element(i);
             var source_cell = source_element.data("cell");
             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 = '';
                 }
                 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_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_element = this.get_cell_element(i);
             var source_cell = source_element.data("cell");
             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 = '';
                 }
                 // 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_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 source_element = this.get_cell_element(i);
             var source_cell = source_element.data("cell");
             var target_cell = null;
             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 = '';
                 }
                 // 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_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 heading cell.
      * 
      * @method to_heading
      * @param {Number} [index] A cell's index
      * @param {Number} [level] A heading level (e.g., 1 becomes &lt;h1&gt;)
      */
     Notebook.prototype.to_heading = function (index, level) {
         level = level || 1;
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var source_element = this.get_cell_element(i);
             var source_cell = source_element.data("cell");
             var target_cell = null;
             if (source_cell instanceof textcell.HeadingCell) {
                 source_cell.set_level(level);
             } else {
                 target_cell = this.insert_cell_below('heading',i);
                 var text = source_cell.get_text();
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 // We must show the editor before setting its contents
                 target_cell.set_level(level);
                 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_element.remove();
                 this.select(i);
                 var cursor = source_cell.code_mirror.getCursor();
                 target_cell.code_mirror.setCursor(cursor);
                 if ((source_cell instanceof textcell.TextCell) && source_cell.rendered) {
                     target_cell.render();
                 }
             }
             this.set_dirty(true);
             this.events.trigger('selected_cell_type_changed.Notebook',
                 {'cell_type':'heading',level:level}
             );
         }
     };
 
 
     // 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();
         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 mdc = textcell.MarkdownCell;
         var rc = textcell.RawCell;
         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 mdc = textcell.MarkdownCell;
         var rc = textcell.RawCell;
         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 mdc = textcell.MarkdownCell;
         var rc = textcell.RawCell;
         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 () {
         $.map(this.get_cells(), 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 () {
         $.map(this.get_cells(), 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 () {
         $.map(this.get_cells(), 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 () {
         $.map(this.get_cells(), 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 () {
         $.map(this.get_cells(), 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 () {
         $.map(this.get_cells(), 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;
         modename = newmode.name || newmode
 
         that = this;
         CodeMirror.requireMode(modename, function(){
             $.map(that.get_cells(), function(cell, i) {
                 if (cell.cell_type === 'code'){
                     cell.code_mirror.setOption('mode', newmode);
                     // 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 = newmode;
                 }
             });
         })
     };
 
     // Session related things
 
     /**
      * Start a new session and set it on each code cell.
      * 
      * @method start_session
      */
     Notebook.prototype.start_session = function (kernel_name) {
         var that = this;
         if (kernel_name === undefined) {
             kernel_name = this.default_kernel_name;
         }
         if (this._session_starting) {
             throw new session.SessionAlreadyStarting();
         }
         this._session_starting = true;
         
         if (this.session !== null) {
             var s = this.session;
             this.session = null;
             // need to start the new session in a callback after delete,
             // because javascript does not guarantee the ordering of AJAX requests (?!)
             s.delete(function () {
                     // on successful delete, start new session
                     that._session_starting = false;
                     that.start_session(kernel_name);
                 }, function (jqXHR, status, error) {
                     // log the failed delete, but still create a new session
                     // 404 just means it was already deleted by someone else,
                     // but other errors are possible.
                     utils.log_ajax_error(jqXHR, status, error);
                     that._session_starting = false;
                     that.start_session(kernel_name);
                 }
             );
             return;
         }
         
         
     
         this.session = new session.Session({
             base_url: this.base_url,
             ws_url: this.ws_url,
             notebook_path: this.notebook_path,
             notebook_name: this.notebook_name,
             // For now, create all sessions with the 'python' kernel, which is the
             // default. Later, the user will be able to select kernels. This is
             // overridden if KernelManager.kernel_cmd is specified for the server.
             kernel_name: kernel_name,
             notebook: this});
 
         this.session.start(
             $.proxy(this._session_started, this),
             $.proxy(this._session_start_failed, this)
         );
     };
 
 
     /**
      * 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.session.restart_kernel();
                     }
                 }
             }
         });
     };
     
     /**
      * 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();
         var cell_index = this.find_cell_index(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) {
         this.notebook_name = 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).
      * 
      * This currently handles one worksheet: others are deleted.
      * 
      * @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;
         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);
         }
         
         // Only handle 1 worksheet for now.
         var worksheet = content.worksheets[0];
         if (worksheet !== undefined) {
             if (worksheet.metadata) {
                 this.worksheet_metadata = worksheet.metadata;
             }
             var new_cells = worksheet.cells;
             ncells = new_cells.length;
             var cell_data = null;
             var new_cell = null;
             for (i=0; i<ncells; i++) {
                 cell_data = new_cells[i];
                 // VERSIONHACK: plaintext -> raw
                 // handle never-released plaintext name for raw cells
                 if (cell_data.cell_type === 'plaintext'){
                     cell_data.cell_type = 'raw';
                 }
 
                 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", {value: trusted});
         }
         if (content.worksheets.length > 1) {
             dialog.modal({
                 notebook: this,
                 keyboard_manager: this.keyboard_manager,
                 title : "Multiple worksheets",
                 body : "This notebook has " + data.worksheets.length + " worksheets, " +
                     "but this version of IPython can only handle the first.  " +
                     "If you save this notebook, worksheets after the first will be lost.",
                 buttons : {
                     OK : {
                         class : "btn-danger"
                     }
                 }
             });
         }
     };
 
     /**
      * Dump this notebook into a JSON-friendly object.
      * 
      * @method toJSON
      * @return {Object} A JSON-friendly representation of this notebook.
      */
     Notebook.prototype.toJSON = function () {
         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 = {
             // Only handle 1 worksheet for now.
             worksheets : [{
                 cells: cell_array,
                 metadata: this.worksheet_metadata
             }],
             metadata : this.metadata
         };
         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);
         }
         
         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 (extra_settings) {
         // Create a JSON model to be sent to the server.
         var model = {};
         model.name = this.notebook_name;
         model.path = this.notebook_path;
         model.type = 'notebook';
         model.format = 'json';
         model.content = this.toJSON();
         model.content.nbformat = this.nbformat;
         model.content.nbformat_minor = this.nbformat_minor;
         // time the ajax call for autosave tuning purposes.
         var start =  new Date().getTime();
         // We do the call with settings so we can set cache to false.
         var settings = {
             processData : false,
             cache : false,
             type : "PUT",
             data : JSON.stringify(model),
             headers : {'Content-Type': 'application/json'},
             success : $.proxy(this.save_notebook_success, this, start),
             error : $.proxy(this.save_notebook_error, this)
         };
         if (extra_settings) {
             for (var key in extra_settings) {
                 settings[key] = extra_settings[key];
             }
         }
         this.events.trigger('notebook_saving.Notebook');
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
     
     /**
      * Success callback for saving a notebook.
      * 
      * @method save_notebook_success
      * @param {Integer} start the time when the save request started
      * @param {Object} data JSON representation of a notebook
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.save_notebook_success = function (start, data, status, xhr) {
         this.set_dirty(false);
         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);
             }
         }
     };
     
     /**
      * Failure callback for saving a notebook.
      * 
      * @method save_notebook_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error HTTP error message
      */
     Notebook.prototype.save_notebook_error = function (xhr, status, error) {
         this.events.trigger('notebook_save_failed.Notebook', [xhr, status, error]);
     };
 
     /**
      * Explicitly trust the output of this notebook.
      *
      * @method trust_notebook
      */
     Notebook.prototype.trust_notebook = function (extra_settings) {
         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.new_notebook = function(){
         var path = this.notebook_path;
         var base_url = this.base_url;
         var settings = {
             processData : false,
             cache : false,
             type : "POST",
             dataType : "json",
             async : false,
             success : function (data, status, xhr){
                 var notebook_name = data.name;
                 window.open(
                     utils.url_join_encode(
                         base_url,
                         'notebooks',
                         path,
                         notebook_name
                     ),
                     '_blank'
                 );
             },
             error : utils.log_ajax_error,
         };
         var url = utils.url_join_encode(
             base_url,
             'api/contents',
             path
         );
         $.ajax(url,settings);
     };
 
 
     Notebook.prototype.copy_notebook = function(){
         var path = this.notebook_path;
         var base_url = this.base_url;
         var settings = {
             processData : false,
             cache : false,
             type : "POST",
             dataType : "json",
             data : JSON.stringify({copy_from : this.notebook_name}),
             async : false,
             success : function (data, status, xhr) {
                 window.open(utils.url_join_encode(
                     base_url,
                     'notebooks',
                     data.path,
                     data.name
                 ), '_blank');
             },
             error : utils.log_ajax_error,
         };
         var url = utils.url_join_encode(
             base_url,
             'api/contents',
             path
         );
         $.ajax(url,settings);
     };
 
     Notebook.prototype.rename = function (nbname) {
         var that = this;
         if (!nbname.match(/\.ipynb$/)) {
             nbname = nbname + ".ipynb";
         }
         var data = {name: nbname};
         var settings = {
             processData : false,
             cache : false,
             type : "PATCH",
             data : JSON.stringify(data),
             dataType: "json",
             headers : {'Content-Type': 'application/json'},
             success : $.proxy(that.rename_success, this),
             error : $.proxy(that.rename_error, this)
         };
         this.events.trigger('rename_notebook.Notebook', data);
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
 
     Notebook.prototype.delete = function () {
         var that = this;
         var settings = {
             processData : false,
             cache : false,
             type : "DELETE",
             dataType: "json",
             error : utils.log_ajax_error,
         };
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
 
     
     Notebook.prototype.rename_success = function (json, status, xhr) {
         var name = this.notebook_name = json.name;
         var path = json.path;
         this.session.rename_notebook(name, path);
         this.events.trigger('notebook_renamed.Notebook', json);
     };
 
     Notebook.prototype.rename_error = function (xhr, status, error) {
         var that = this;
         var dialog_body = $('<div/>').append(
             $("<p/>").text('This notebook name already exists.')
         );
         this.events.trigger('notebook_rename_failed.Notebook', [xhr, status, error]);
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title: "Notebook Rename Error!",
             body: dialog_body,
             buttons : {
                 "Cancel": {},
                 "OK": {
                     class: "btn-primary",
                     click: function () {
                         this.save_widget.rename_notebook({notebook:that});
                 }}
                 },
             open : function (event, ui) {
                 var that = $(this);
                 // Upon ENTER, click the OK button.
                 that.find('input[type="text"]').keydown(function (event, ui) {
                     if (event.which === this.keyboard.keycodes.enter) {
                         that.find('.btn-primary').first().click();
                     }
                 });
                 that.find('input[type="text"]').focus();
             }
         });
     };
 
     /**
      * Request a notebook's data from the server.
      * 
      * @method load_notebook
      * @param {String} notebook_name and path A notebook to load
      */
     Notebook.prototype.load_notebook = function (notebook_name, notebook_path) {
         var that = this;
         this.notebook_name = notebook_name;
         this.notebook_path = notebook_path;
         // We do the call with settings so we can set cache to false.
         var settings = {
             processData : false,
             cache : false,
             type : "GET",
             dataType : "json",
             success : $.proxy(this.load_notebook_success,this),
             error : $.proxy(this.load_notebook_error,this),
         };
         this.events.trigger('notebook_loading.Notebook');
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
 
     /**
      * 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
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.load_notebook_success = function (data, status, xhr) {
         this.fromJSON(data);
         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();
         if (data.orig_nbformat !== undefined && data.nbformat !== data.orig_nbformat) {
             var msg = "This notebook has been converted from an older " +
             "notebook format (v"+data.orig_nbformat+") to the current notebook " +
             "format (v"+data.nbformat+"). The next time you save this notebook, the " +
             "newer notebook format will be used and older versions of IPython " +
             "may not be able to read it. To keep the older 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 (data.orig_nbformat_minor !== undefined && data.nbformat_minor !== data.orig_nbformat_minor) {
             var that = this;
             var orig_vs = 'v' + data.nbformat + '.' + data.orig_nbformat_minor;
             var this_vs = 'v' + data.nbformat + '.' + this.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 some features " +
             "introduced in later notebook versions may not be available.";
 
             dialog.modal({
                 notebook: this,
                 keyboard_manager: this.keyboard_manager,
                 title : "Newer Notebook",
                 body : msg,
                 buttons : {
                     OK : {
                         class : "btn-danger"
                     }
                 }
             });
 
         }
         
         // 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 kernelspec = this.metadata.kernelspec || {};
             var kernel_name = kernelspec.name || this.default_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();
         }
 
         // now that we're fully loaded, it is safe to restore save functionality
         delete(this.save_notebook);
         this.events.trigger('notebook_loaded.Notebook');
     };
 
     /**
      * Failure callback for loading a notebook from the server.
      * 
      * @method load_notebook_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error HTTP error message
      */
     Notebook.prototype.load_notebook_error = function (xhr, status, error) {
         this.events.trigger('notebook_load_failed.Notebook', [xhr, status, error]);
         utils.log_ajax_error(xhr, status, error);
         var msg;
         if (xhr.status === 400) {
             msg = escape(utils.ajax_error_msg(xhr));
         } else if (xhr.status === 500) {
             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.";
         }
         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 url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name,
             'checkpoints'
         );
         $.get(url).done(
             $.proxy(this.list_checkpoints_success, this)
         ).fail(
             $.proxy(this.list_checkpoints_error, this)
         );
     };
 
     /**
      * Success callback for listing checkpoints.
      * 
      * @method list_checkpoint_success
      * @param {Object} data JSON representation of a checkpoint
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.list_checkpoints_success = function (data, status, xhr) {
         data = $.parseJSON(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]);
     };
 
     /**
      * Failure callback for listing a checkpoint.
      * 
      * @method list_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error_msg HTTP error message
      */
     Notebook.prototype.list_checkpoints_error = function (xhr, status, error_msg) {
         this.events.trigger('list_checkpoints_failed.Notebook');
     };
     
     /**
      * Create a checkpoint of this notebook on the server from the most recent save.
      * 
      * @method create_checkpoint
      */
     Notebook.prototype.create_checkpoint = function () {
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name,
             'checkpoints'
         );
         $.post(url).done(
             $.proxy(this.create_checkpoint_success, this)
         ).fail(
             $.proxy(this.create_checkpoint_error, this)
         );
     };
 
     /**
      * Success callback for creating a checkpoint.
      * 
      * @method create_checkpoint_success
      * @param {Object} data JSON representation of a checkpoint
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.create_checkpoint_success = function (data, status, xhr) {
         data = $.parseJSON(data);
         this.add_checkpoint(data);
         this.events.trigger('checkpoint_created.Notebook', data);
     };
 
     /**
      * Failure callback for creating a checkpoint.
      * 
      * @method create_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error_msg HTTP error message
      */
     Notebook.prototype.create_checkpoint_error = function (xhr, status, error_msg) {
         this.events.trigger('checkpoint_failed.Notebook');
     };
     
     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 url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name,
             'checkpoints',
             checkpoint
         );
         $.post(url).done(
             $.proxy(this.restore_checkpoint_success, this)
         ).fail(
             $.proxy(this.restore_checkpoint_error, this)
         );
     };
     
     /**
      * Success callback for restoring a notebook to a checkpoint.
      * 
      * @method restore_checkpoint_success
      * @param {Object} data (ignored, should be empty)
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.restore_checkpoint_success = function (data, status, xhr) {
         this.events.trigger('checkpoint_restored.Notebook');
         this.load_notebook(this.notebook_name, this.notebook_path);
     };
 
     /**
      * Failure callback for restoring a notebook to a checkpoint.
      * 
      * @method restore_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error_msg HTTP error message
      */
     Notebook.prototype.restore_checkpoint_error = function (xhr, status, error_msg) {
         this.events.trigger('checkpoint_restore_failed.Notebook');
     };
     
     /**
      * 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 url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name,
             'checkpoints',
             checkpoint
         );
         $.ajax(url, {
             type: 'DELETE',
             success: $.proxy(this.delete_checkpoint_success, this),
             error: $.proxy(this.delete_checkpoint_error, this)
         });
     };
     
     /**
      * Success callback for deleting a notebook checkpoint
      * 
      * @method delete_checkpoint_success
      * @param {Object} data (ignored, should be empty)
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.delete_checkpoint_success = function (data, status, xhr) {
         this.events.trigger('checkpoint_deleted.Notebook', data);
         this.load_notebook(this.notebook_name, this.notebook_path);
     };
 
     /**
      * Failure callback for deleting a notebook checkpoint.
      * 
      * @method delete_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error HTTP error message
      */
     Notebook.prototype.delete_checkpoint_error = function (xhr, status, error) {
         this.events.trigger('checkpoint_delete_failed.Notebook', [xhr, status, error]);
     };
 
 
     // For backwards compatability.
     IPython.Notebook = Notebook;
 
     return {'Notebook': Notebook};
 });