The Tor Browser: browser/components/tabview/groupitems.js@6474c204b198 (annotated)

browser/components/tabview/groupitems.js@6474c204b198 (annotated)

browser/components/tabview/groupitems.js

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 // **********
 // Title: groupItems.js
 // ##########
 // Class: GroupItem
 // A single groupItem in the TabView window. Descended from <Item>.
 // Note that it implements the <Subscribable> interface.
 //
 // ----------
 // Constructor: GroupItem
 //
 // Parameters:
 //   listOfEls - an array of DOM elements for tabs to be added to this groupItem
 //   options - various options for this groupItem (see below). In addition, gets passed
 //     to <add> along with the elements provided.
 //
 // Possible options:
 //   id - specifies the groupItem's id; otherwise automatically generated
 //   userSize - see <Item.userSize>; default is null
 //   bounds - a <Rect>; otherwise based on the locations of the provided elements
 //   container - a DOM element to use as the container for this groupItem; otherwise will create
 //   title - the title for the groupItem; otherwise blank
 //   focusTitle - focus the title's input field after creation
 //   dontPush - true if this groupItem shouldn't push away or snap on creation; default is false
 //   immediately - true if we want all placement immediately, not with animation
 function GroupItem(listOfEls, options) {
   if (!options)
     options = {};
   this._inited = false;
   this._uninited = false;
   this._children = []; // an array of Items
   this.isAGroupItem = true;
   this.id = options.id || GroupItems.getNextID();
   this._isStacked = false;
   this.expanded = null;
   this.hidden = false;
   this.fadeAwayUndoButtonDelay = 15000;
   this.fadeAwayUndoButtonDuration = 300;
   this.keepProportional = false;
   this._frozenItemSizeData = {};
   this._onChildClose = this._onChildClose.bind(this);
   // Variable: _activeTab
   // The <TabItem> for the groupItem's active tab.
   this._activeTab = null;
   if (Utils.isPoint(options.userSize))
     this.userSize = new Point(options.userSize);
   var self = this;
   var rectToBe;
   if (options.bounds) {
     Utils.assert(Utils.isRect(options.bounds), "options.bounds must be a Rect");
     rectToBe = new Rect(options.bounds);
   }
   if (!rectToBe) {
     rectToBe = GroupItems.getBoundingBox(listOfEls);
     rectToBe.inset(-42, -42);
   }
   var $container = options.container;
   let immediately = options.immediately || $container ? true : false;
   if (!$container) {
     $container = iQ('<div>')
       .addClass('groupItem')
       .css({position: 'absolute'})
       .css(rectToBe);
   }
   this.bounds = $container.bounds();
   this.isDragging = false;
   $container
     .css({zIndex: -100})
     .attr("data-id", this.id)
     .appendTo("body");
   // ___ Resizer
   this.$resizer = iQ("<div>")
     .addClass('resizer')
     .appendTo($container)
     .hide();
   // ___ Titlebar
   var html =
     "<div class='title-container'>" +
       "<input class='name' />" +
       "<div class='title-shield' />" +
     "</div>";
   this.$titlebar = iQ('<div>')
     .addClass('titlebar')
     .html(html)
     .appendTo($container);
   this.$closeButton = iQ('<div>')
     .addClass('close')
     .click(function() {
       self.closeAll();
     })
     .attr("title", tabviewString("groupItem.closeGroup"))
     .appendTo($container);
   // ___ Title
   this.$titleContainer = iQ('.title-container', this.$titlebar);
   this.$title = iQ('.name', this.$titlebar).attr('placeholder', this.defaultName);
   this.$titleShield = iQ('.title-shield', this.$titlebar);
   this.setTitle(options.title);
   var handleKeyPress = function (e) {
     if (e.keyCode == KeyEvent.DOM_VK_ESCAPE ||
         e.keyCode == KeyEvent.DOM_VK_RETURN) {
       (self.$title)[0].blur();
       self.$title
         .addClass("transparentBorder")
         .one("mouseout", function() {
           self.$title.removeClass("transparentBorder");
         });
       e.stopPropagation();
       e.preventDefault();
     }
   };
   var handleKeyUp = function(e) {
     // NOTE: When user commits or cancels IME composition, the last key
     //       event fires only a keyup event.  Then, we shouldn't take any
     //       reactions but we should update our status.
     self.save();
   };
   this.$title
     .blur(function() {
       self._titleFocused = false;
       self.$title[0].setSelectionRange(0, 0);
       self.$titleShield.show();
       if (self.getTitle())
         gTabView.firstUseExperienced = true;
       self.save();
     })
     .focus(function() {
       self._unfreezeItemSize();
       if (!self._titleFocused) {
         (self.$title)[0].select();
         self._titleFocused = true;
       }
     })
     .mousedown(function(e) {
       e.stopPropagation();
     })
     .keypress(handleKeyPress)
     .keyup(handleKeyUp)
     .attr("title", tabviewString("groupItem.defaultName"));
   this.$titleShield
     .mousedown(function(e) {
       self.lastMouseDownTarget = (Utils.isLeftClick(e) ? e.target : null);
     })
     .mouseup(function(e) {
       var same = (e.target == self.lastMouseDownTarget);
       self.lastMouseDownTarget = null;
       if (!same)
         return;
       if (!self.isDragging)
         self.focusTitle();
     })
     .attr("title", tabviewString("groupItem.defaultName"));
   if (options.focusTitle)
     this.focusTitle();
   // ___ Stack Expander
   this.$expander = iQ("<div/>")
     .addClass("stackExpander")
     .appendTo($container)
     .hide();
   // ___ app tabs: create app tab tray and populate it
   let appTabTrayContainer = iQ("<div/>")
     .addClass("appTabTrayContainer")
     .appendTo($container);
   this.$appTabTray = iQ("<div/>")
     .addClass("appTabTray")
     .appendTo(appTabTrayContainer);
   let pinnedTabCount = gBrowser._numPinnedTabs;
   AllTabs.tabs.forEach(function (xulTab, index) {
     // only adjust tray when it's the last app tab.
     if (xulTab.pinned)
       this.addAppTab(xulTab, {dontAdjustTray: index + 1 < pinnedTabCount});
   }, this);
   // ___ Undo Close
   this.$undoContainer = null;
   this._undoButtonTimeoutId = null;
   // ___ Superclass initialization
   this._init($container[0]);
   // ___ Children
   // We explicitly set dontArrange=true to prevent the groupItem from
   // re-arranging its children after a tabItem has been added. This saves us a
   // group.arrange() call per child and therefore some tab.setBounds() calls.
   options.dontArrange = true;
   listOfEls.forEach(function (el) {
     self.add(el, options);
   });
   // ___ Finish Up
   this._addHandlers($container);
   this.setResizable(true, immediately);
   GroupItems.register(this);
   // ___ Position
   this.setBounds(rectToBe, immediately);
   if (options.dontPush) {
     this.setZ(drag.zIndex);
     drag.zIndex++;
   } else {
     // Calling snap will also trigger pushAway
     this.snap(immediately);
   }
   if (!options.immediately && listOfEls.length > 0)
     $container.hide().fadeIn();
   this._inited = true;
   this.save();
   GroupItems.updateGroupCloseButtons();
 };
 // ----------
 GroupItem.prototype = Utils.extend(new Item(), new Subscribable(), {
   // ----------
   // Function: toString
   // Prints [GroupItem id=id] for debug use
   toString: function GroupItem_toString() {
     return "[GroupItem id=" + this.id + "]";
   },
   // ----------
   // Variable: defaultName
   // The prompt text for the title field.
   defaultName: tabviewString('groupItem.defaultName'),
   // -----------
   // Function: setActiveTab
   // Sets the active <TabItem> for this groupItem; can be null, but only
   // if there are no children.
   setActiveTab: function GroupItem_setActiveTab(tab) {
     Utils.assertThrow((!tab && this._children.length == 0) || tab.isATabItem,
         "tab must be null (if no children) or a TabItem");
     this._activeTab = tab;
     if (this.isStacked())
       this.arrange({immediately: true});
   },
   // -----------
   // Function: getActiveTab
   // Gets the active <TabItem> for this groupItem; can be null, but only
   // if there are no children.
   getActiveTab: function GroupItem_getActiveTab() {
     return this._activeTab;
   },
   // ----------
   // Function: getStorageData
   // Returns all of the info worth storing about this groupItem.
   getStorageData: function GroupItem_getStorageData() {
     var data = {
       bounds: this.getBounds(),
       userSize: null,
       title: this.getTitle(),
       id: this.id
     };
     if (Utils.isPoint(this.userSize))
       data.userSize = new Point(this.userSize);
     return data;
   },
   // ----------
   // Function: isEmpty
   // Returns true if the tab groupItem is empty and unnamed.
   isEmpty: function GroupItem_isEmpty() {
     return !this._children.length && !this.getTitle();
   },
   // ----------
   // Function: isStacked
   // Returns true if this item is in a stacked groupItem.
   isStacked: function GroupItem_isStacked() {
     return this._isStacked;
   },
   // ----------
   // Function: isTopOfStack
   // Returns true if the item is showing on top of this group's stack,
   // determined by whether the tab is this group's topChild, or
   // if it doesn't have one, its first child.
   isTopOfStack: function GroupItem_isTopOfStack(item) {
     return this.isStacked() && item == this.getTopChild();
   },
   // ----------
   // Function: save
   // Saves this groupItem to persistent storage.
   save: function GroupItem_save() {
     if (!this._inited || this._uninited) // too soon/late to save
       return;
     var data = this.getStorageData();
     if (GroupItems.groupItemStorageSanity(data))
       Storage.saveGroupItem(gWindow, data);
   },
   // ----------
   // Function: deleteData
   // Deletes the groupItem in the persistent storage.
   deleteData: function GroupItem_deleteData() {
     this._uninited = true;
     Storage.deleteGroupItem(gWindow, this.id);
   },
   // ----------
   // Function: getTitle
   // Returns the title of this groupItem as a string.
   getTitle: function GroupItem_getTitle() {
     return this.$title ? this.$title.val() : '';
   },
   // ----------
   // Function: setTitle
   // Sets the title of this groupItem with the given string
   setTitle: function GroupItem_setTitle(value) {
     this.$title.val(value);
     this.save();
   },
   // ----------
   // Function: focusTitle
   // Hide the title's shield and focus the underlying input field.
   focusTitle: function GroupItem_focusTitle() {
     this.$titleShield.hide();
     this.$title[0].focus();
   },
   // ----------
   // Function: adjustAppTabTray
   // Used to adjust the appTabTray size, to split the appTabIcons across
   // multiple columns when needed - if the groupItem size is too small.
   //
   // Parameters:
   //   arrangeGroup - rearrange the groupItem if the number of appTab columns
   //   changes. If true, then this.arrange() is called, otherwise not.
   adjustAppTabTray: function GroupItem_adjustAppTabTray(arrangeGroup) {
     let icons = iQ(".appTabIcon", this.$appTabTray);
     let container = iQ(this.$appTabTray[0].parentNode);
     if (!icons.length) {
       // There are no icons, so hide the appTabTray if needed.
       if (parseInt(container.css("width")) != 0) {
         this.$appTabTray.css("-moz-column-count", "auto");
         this.$appTabTray.css("height", 0);
         container.css("width", 0);
         container.css("height", 0);
         if (container.hasClass("appTabTrayContainerTruncated"))
           container.removeClass("appTabTrayContainerTruncated");
         if (arrangeGroup)
           this.arrange();
       }
       return;
     }
     let iconBounds = iQ(icons[0]).bounds();
     let boxBounds = this.getBounds();
     let contentHeight = boxBounds.height -
                         parseInt(container.css("top")) -
                         this.$resizer.height();
     let rows = Math.floor(contentHeight / iconBounds.height);
     let columns = Math.ceil(icons.length / rows);
     let columnsGap = parseInt(this.$appTabTray.css("-moz-column-gap"));
     let iconWidth = iconBounds.width + columnsGap;
     let maxColumns = Math.floor((boxBounds.width * 0.20) / iconWidth);
     Utils.assert(rows > 0 && columns > 0 && maxColumns > 0,
       "make sure the calculated rows, columns and maxColumns are correct");
     if (columns > maxColumns)
       container.addClass("appTabTrayContainerTruncated");
     else if (container.hasClass("appTabTrayContainerTruncated"))
       container.removeClass("appTabTrayContainerTruncated");
     // Need to drop the -moz- prefix when Gecko makes it obsolete.
     // See bug 629452.
     if (parseInt(this.$appTabTray.css("-moz-column-count")) != columns)
       this.$appTabTray.css("-moz-column-count", columns);
     if (parseInt(this.$appTabTray.css("height")) != contentHeight) {
       this.$appTabTray.css("height", contentHeight + "px");
       container.css("height", contentHeight + "px");
     }
     let fullTrayWidth = iconWidth * columns - columnsGap;
     if (parseInt(this.$appTabTray.css("width")) != fullTrayWidth)
       this.$appTabTray.css("width", fullTrayWidth + "px");
     let trayWidth = iconWidth * Math.min(columns, maxColumns) - columnsGap;
     if (parseInt(container.css("width")) != trayWidth) {
       container.css("width", trayWidth + "px");
       // Rearrange the groupItem if the width changed.
       if (arrangeGroup)
         this.arrange();
     }
   },
   // ----------
   // Function: getContentBounds
   // Returns a <Rect> for the groupItem's content area (which doesn't include the title, etc).
   //
   // Parameters:
   //   options - an object with additional parameters, see below
   //
   // Possible options:
   //   stacked - true to get content bounds for stacked mode
   getContentBounds: function GroupItem_getContentBounds(options) {
     let box = this.getBounds();
     let titleHeight = this.$titlebar.height();
     box.top += titleHeight;
     box.height -= titleHeight;
     let appTabTrayContainer = iQ(this.$appTabTray[0].parentNode);
     let appTabTrayWidth = appTabTrayContainer.width();
     if (appTabTrayWidth)
       appTabTrayWidth += parseInt(appTabTrayContainer.css(UI.rtl ? "left" : "right"));
     box.width -= appTabTrayWidth;
     if (UI.rtl) {
       box.left += appTabTrayWidth;
     }
     // Make the computed bounds' "padding" and expand button margin actually be
     // themeable --OR-- compute this from actual bounds. Bug 586546
     box.inset(6, 6);
     // make some room for the expand button in stacked mode
     if (options && options.stacked)
       box.height -= this.$expander.height() + 9; // the button height plus padding
     return box;
   },
   // ----------
   // Function: setBounds
   // Sets the bounds with the given <Rect>, animating unless "immediately" is false.
   //
   // Parameters:
   //   inRect - a <Rect> giving the new bounds
   //   immediately - true if it should not animate; default false
   //   options - an object with additional parameters, see below
   //
   // Possible options:
   //   force - true to always update the DOM even if the bounds haven't changed; default false
   setBounds: function GroupItem_setBounds(inRect, immediately, options) {
       Utils.assert(Utils.isRect(inRect), 'GroupItem.setBounds: rect is not a real rectangle!');
     // Validate and conform passed in size
     let validSize = GroupItems.calcValidSize(
       new Point(inRect.width, inRect.height));
     let rect = new Rect(inRect.left, inRect.top, validSize.x, validSize.y);
     if (!options)
       options = {};
     var titleHeight = this.$titlebar.height();
     // ___ Determine what has changed
     var css = {};
     var titlebarCSS = {};
     var contentCSS = {};
     if (rect.left != this.bounds.left || options.force)
       css.left = rect.left;
     if (rect.top != this.bounds.top || options.force)
       css.top = rect.top;
     if (rect.width != this.bounds.width || options.force) {
       css.width = rect.width;
       titlebarCSS.width = rect.width;
       contentCSS.width = rect.width;
     }
     if (rect.height != this.bounds.height || options.force) {
       css.height = rect.height;
       contentCSS.height = rect.height - titleHeight;
     }
     if (Utils.isEmptyObject(css))
       return;
     var offset = new Point(rect.left - this.bounds.left, rect.top - this.bounds.top);
     this.bounds = new Rect(rect);
     // Make sure the AppTab icons fit the new groupItem size.
     if (css.width || css.height)
       this.adjustAppTabTray();
     // ___ Deal with children
     if (css.width || css.height) {
       this.arrange({animate: !immediately}); //(immediately ? 'sometimes' : true)});
     } else if (css.left || css.top) {
       this._children.forEach(function(child) {
         if (!child.getHidden()) {
           var box = child.getBounds();
           child.setPosition(box.left + offset.x, box.top + offset.y, immediately);
         }
       });
     }
     // ___ Update our representation
     if (immediately) {
       iQ(this.container).css(css);
       this.$titlebar.css(titlebarCSS);
     } else {
       TabItems.pausePainting();
       iQ(this.container).animate(css, {
         duration: 350,
         easing: "tabviewBounce",
         complete: function() {
           TabItems.resumePainting();
         }
       });
       this.$titlebar.animate(titlebarCSS, {
         duration: 350
       });
     }
     UI.clearShouldResizeItems();
     this.setTrenches(rect);
     this.save();
   },
   // ----------
   // Function: setZ
   // Set the Z order for the groupItem's container, as well as its children.
   setZ: function GroupItem_setZ(value) {
     this.zIndex = value;
     iQ(this.container).css({zIndex: value});
     var count = this._children.length;
     if (count) {
       var topZIndex = value + count + 1;
       var zIndex = topZIndex;
       var self = this;
       this._children.forEach(function(child) {
         if (child == self.getTopChild())
           child.setZ(topZIndex + 1);
         else {
           child.setZ(zIndex);
           zIndex--;
         }
       });
     }
   },
   // ----------
   // Function: close
   // Closes the groupItem, removing (but not closing) all of its children.
   //
   // Parameters:
   //   options - An object with optional settings for this call.
   //
   // Options:
   //   immediately - (bool) if true, no animation will be used
   close: function GroupItem_close(options) {
     this.removeAll({dontClose: true});
     GroupItems.unregister(this);
     // remove unfreeze event handlers, if item size is frozen
     this._unfreezeItemSize({dontArrange: true});
     let self = this;
     let destroyGroup = function () {
       iQ(self.container).remove();
       if (self.$undoContainer) {
         self.$undoContainer.remove();
         self.$undoContainer = null;
       }
       self.removeTrenches();
       Items.unsquish();
       self._sendToSubscribers("close");
       GroupItems.updateGroupCloseButtons();
     }
     if (this.hidden || (options && options.immediately)) {
       destroyGroup();
     } else {
       iQ(this.container).animate({
         opacity: 0,
         "transform": "scale(.3)",
       }, {
         duration: 170,
         complete: destroyGroup
       });
     }
     this.deleteData();
   },
   // ----------
   // Function: closeAll
   // Closes the groupItem and all of its children.
   closeAll: function GroupItem_closeAll() {
     if (this._children.length > 0) {
       this._unfreezeItemSize();
       this._children.forEach(function(child) {
         iQ(child.container).hide();
       });
       iQ(this.container).animate({
          opacity: 0,
          "transform": "scale(.3)",
       }, {
         duration: 170,
         complete: function() {
           iQ(this).hide();
         }
       });
       this.droppable(false);
       this.removeTrenches();
       this._createUndoButton();
     } else
       this.close();
     this._makeLastActiveGroupItemActive();
   },
   // ----------
   // Function: _makeClosestTabActive
   // Make the closest tab external to this group active.
   // Used when closing the group.
   _makeClosestTabActive: function GroupItem__makeClosestTabActive() {
     let closeCenter = this.getBounds().center();
     // Find closest tab to make active
     let closestTabItem = UI.getClosestTab(closeCenter);
     if (closestTabItem)
       UI.setActive(closestTabItem);
   },
   // ----------
   // Function: _makeLastActiveGroupItemActive
   // Makes the last active group item active.
   _makeLastActiveGroupItemActive: function GroupItem__makeLastActiveGroupItemActive() {
     let groupItem = GroupItems.getLastActiveGroupItem();
     if (groupItem)
       UI.setActive(groupItem);
     else
       this._makeClosestTabActive();
   },
   // ----------
   // Function: closeIfEmpty
   // Closes the group if it's empty, is closable, and autoclose is enabled
   // (see pauseAutoclose()). Returns true if the close occurred and false
   // otherwise.
   closeIfEmpty: function GroupItem_closeIfEmpty() {
     if (this.isEmpty() && !UI._closedLastVisibleTab &&
         !GroupItems.getUnclosableGroupItemId() && !GroupItems._autoclosePaused) {
       this.close();
       return true;
     }
     return false;
   },
   // ----------
   // Function: _unhide
   // Shows the hidden group.
   //
   // Parameters:
   //   options - various options (see below)
   //
   // Possible options:
   //   immediately - true when no animations should be used
   _unhide: function GroupItem__unhide(options) {
     this._cancelFadeAwayUndoButtonTimer();
     this.hidden = false;
     this.$undoContainer.remove();
     this.$undoContainer = null;
     this.droppable(true);
     this.setTrenches(this.bounds);
     let self = this;
     let finalize = function () {
       self._children.forEach(function(child) {
         iQ(child.container).show();
       });
       UI.setActive(self);
       self._sendToSubscribers("groupShown");
     };
     let $container = iQ(this.container).show();
     if (!options || !options.immediately) {
       $container.animate({
         "transform": "scale(1)",
         "opacity": 1
       }, {
         duration: 170,
         complete: finalize
       });
     } else {
       $container.css({"transform": "none", opacity: 1});
       finalize();
     }
     GroupItems.updateGroupCloseButtons();
   },
   // ----------
   // Function: closeHidden
   // Removes the group item, its children and its container.
   closeHidden: function GroupItem_closeHidden() {
     let self = this;
     this._cancelFadeAwayUndoButtonTimer();
     // When the last non-empty groupItem is closed and there are no
     // pinned tabs then create a new group with a blank tab.
     let remainingGroups = GroupItems.groupItems.filter(function (groupItem) {
       return (groupItem != self && groupItem.getChildren().length);
     });
     let tab = null;
     if (!gBrowser._numPinnedTabs && !remainingGroups.length) {
       let emptyGroups = GroupItems.groupItems.filter(function (groupItem) {
         return (groupItem != self && !groupItem.getChildren().length);
       });
       let group = (emptyGroups.length ? emptyGroups[0] : GroupItems.newGroup());
       tab = group.newTab(null, {dontZoomIn: true});
     }
     let closed = this.destroy();
     if (!tab)
       return;
     if (closed) {
       // Let's make the new tab the selected tab.
       UI.goToTab(tab);
     } else {
       // Remove the new tab and group, if this group is no longer closed.
       tab._tabViewTabItem.parent.destroy({immediately: true});
     }
   },
   // ----------
   // Function: destroy
   // Close all tabs linked to children (tabItems), removes all children and
   // close the groupItem.
   //
   // Parameters:
   //   options - An object with optional settings for this call.
   //
   // Options:
   //   immediately - (bool) if true, no animation will be used
   //
   // Returns true if the groupItem has been closed, or false otherwise. A group
   // could not have been closed due to a tab with an onUnload handler (that
   // waits for user interaction).
   destroy: function GroupItem_destroy(options) {
     let self = this;
     // when "TabClose" event is fired, the browser tab is about to close and our
     // item "close" event is fired.  And then, the browser tab gets closed.
     // In other words, the group "close" event is fired before all browser
     // tabs in the group are closed.  The below code would fire the group "close"
     // event only after all browser tabs in that group are closed.
     this._children.concat().forEach(function(child) {
       child.removeSubscriber("close", self._onChildClose);
       if (child.close(true)) {
         self.remove(child, { dontArrange: true });
       } else {
         // child.removeSubscriber() must be called before child.close(),
         // therefore we call child.addSubscriber() if the tab is not removed.
         child.addSubscriber("close", self._onChildClose);
       }
     });
     if (this._children.length) {
       if (this.hidden)
         this.$undoContainer.fadeOut(function() { self._unhide() });
       return false;
     } else {
       this.close(options);
       return true;
     }
   },
   // ----------
   // Function: _fadeAwayUndoButton
   // Fades away the undo button
   _fadeAwayUndoButton: function GroupItem__fadeAwayUndoButton() {
     let self = this;
     if (this.$undoContainer) {
       // if there is more than one group and other groups are not empty,
       // fade away the undo button.
       let shouldFadeAway = false;
       if (GroupItems.groupItems.length > 1) {
         shouldFadeAway =
           GroupItems.groupItems.some(function(groupItem) {
             return (groupItem != self && groupItem.getChildren().length > 0);
           });
       }
       if (shouldFadeAway) {
         self.$undoContainer.animate({
           color: "transparent",
           opacity: 0
         }, {
           duration: this._fadeAwayUndoButtonDuration,
           complete: function() { self.closeHidden(); }
         });
       }
     }
   },
   // ----------
   // Function: _createUndoButton
   // Makes the affordance for undo a close group action
   _createUndoButton: function GroupItem__createUndoButton() {
     let self = this;
     this.$undoContainer = iQ("<div/>")
       .addClass("undo")
       .attr("type", "button")
       .attr("data-group-id", this.id)
       .appendTo("body");
     iQ("<span/>")
       .text(tabviewString("groupItem.undoCloseGroup"))
       .appendTo(this.$undoContainer);
     let undoClose = iQ("<span/>")
       .addClass("close")
       .attr("title", tabviewString("groupItem.discardClosedGroup"))
       .appendTo(this.$undoContainer);
     this.$undoContainer.css({
       left: this.bounds.left + this.bounds.width/2 - iQ(self.$undoContainer).width()/2,
       top:  this.bounds.top + this.bounds.height/2 - iQ(self.$undoContainer).height()/2,
       "transform": "scale(.1)",
       opacity: 0
     });
     this.hidden = true;
     // hide group item and show undo container.
     setTimeout(function() {
       self.$undoContainer.animate({
         "transform": "scale(1)",
         "opacity": 1
       }, {
         easing: "tabviewBounce",
         duration: 170,
         complete: function() {
           self._sendToSubscribers("groupHidden");
         }
       });
     }, 50);
     // add click handlers
     this.$undoContainer.click(function(e) {
       // don't do anything if the close button is clicked.
       if (e.target == undoClose[0])
         return;
       self.$undoContainer.fadeOut(function() { self._unhide(); });
     });
     undoClose.click(function() {
       self.$undoContainer.fadeOut(function() { self.closeHidden(); });
     });
     this.setupFadeAwayUndoButtonTimer();
     // Cancel the fadeaway if you move the mouse over the undo
     // button, and restart the countdown once you move out of it.
     this.$undoContainer.mouseover(function() {
       self._cancelFadeAwayUndoButtonTimer();
     });
     this.$undoContainer.mouseout(function() {
       self.setupFadeAwayUndoButtonTimer();
     });
     GroupItems.updateGroupCloseButtons();
   },
   // ----------
   // Sets up fade away undo button timeout.
   setupFadeAwayUndoButtonTimer: function GroupItem_setupFadeAwayUndoButtonTimer() {
     let self = this;
     if (!this._undoButtonTimeoutId) {
       this._undoButtonTimeoutId = setTimeout(function() {
         self._fadeAwayUndoButton();
       }, this.fadeAwayUndoButtonDelay);
     }
   },
   // ----------
   // Cancels the fade away undo button timeout.
   _cancelFadeAwayUndoButtonTimer: function GroupItem__cancelFadeAwayUndoButtonTimer() {
     clearTimeout(this._undoButtonTimeoutId);
     this._undoButtonTimeoutId = null;
   },
   // ----------
   // Function: add
   // Adds an item to the groupItem.
   // Parameters:
   //
   //   a - The item to add. Can be an <Item>, a DOM element or an iQ object.
   //       The latter two must refer to the container of an <Item>.
   //   options - An object with optional settings for this call.
   //
   // Options:
   //
   //   index - (int) if set, add this tab at this index
   //   immediately - (bool) if true, no animation will be used
   //   dontArrange - (bool) if true, will not trigger an arrange on the group
   add: function GroupItem_add(a, options) {
     try {
       var item;
       var $el;
       if (a.isAnItem) {
         item = a;
         $el = iQ(a.container);
       } else {
         $el = iQ(a);
         item = Items.item($el);
       }
       // safeguard to remove the item from its previous group
       if (item.parent && item.parent !== this)
         item.parent.remove(item);
       item.removeTrenches();
       if (!options)
         options = {};
       var self = this;
       var wasAlreadyInThisGroupItem = false;
       var oldIndex = this._children.indexOf(item);
       if (oldIndex != -1) {
         this._children.splice(oldIndex, 1);
         wasAlreadyInThisGroupItem = true;
       }
       // Insert the tab into the right position.
       var index = ("index" in options) ? options.index : this._children.length;
       this._children.splice(index, 0, item);
       item.setZ(this.getZ() + 1);
       if (!wasAlreadyInThisGroupItem) {
         item.droppable(false);
         item.groupItemData = {};
         item.addSubscriber("close", this._onChildClose);
         item.setParent(this);
         $el.attr("data-group-id", this.id);
         if (typeof item.setResizable == 'function')
           item.setResizable(false, options.immediately);
         if (item == UI.getActiveTab() || !this._activeTab)
           this.setActiveTab(item);
         // if it matches the selected tab or no active tab and the browser
         // tab is hidden, the active group item would be set.
         if (item.tab.selected ||
             (!GroupItems.getActiveGroupItem() && !item.tab.hidden))
           UI.setActive(this);
       }
       if (!options.dontArrange)
         this.arrange({animate: !options.immediately});
       this._unfreezeItemSize({dontArrange: true});
       this._sendToSubscribers("childAdded", { item: item });
       UI.setReorderTabsOnHide(this);
     } catch(e) {
       Utils.log('GroupItem.add error', e);
     }
   },
   // ----------
   // Function: _onChildClose
   // Handles "close" events from the group's children.
   //
   // Parameters:
   //   tabItem - The tabItem that is closed.
   _onChildClose: function GroupItem__onChildClose(tabItem) {
     let count = this._children.length;
     let dontArrange = tabItem.closedManually &&
                       (this.expanded || !this.shouldStack(count));
     let dontClose = !tabItem.closedManually && gBrowser._numPinnedTabs > 0;
     this.remove(tabItem, {dontArrange: dontArrange, dontClose: dontClose});
     if (dontArrange)
       this._freezeItemSize(count);
     if (this._children.length > 0 && this._activeTab && tabItem.closedManually)
       UI.setActive(this);
   },
   // ----------
   // Function: remove
   // Removes an item from the groupItem.
   // Parameters:
   //
   //   a - The item to remove. Can be an <Item>, a DOM element or an iQ object.
   //       The latter two must refer to the container of an <Item>.
   //   options - An optional object with settings for this call. See below.
   //
   // Possible options:
   //   dontArrange - don't rearrange the remaining items
   //   dontClose - don't close the group even if it normally would
   //   immediately - don't animate
   remove: function GroupItem_remove(a, options) {
     try {
       let $el;
       let item;
       if (a.isAnItem) {
         item = a;
         $el = iQ(item.container);
       } else {
         $el = iQ(a);
         item = Items.item($el);
       }
       if (!options)
         options = {};
       let index = this._children.indexOf(item);
       if (index != -1)
         this._children.splice(index, 1);
       if (item == this._activeTab || !this._activeTab) {
         if (this._children.length > 0)
           this._activeTab = this._children[0];
         else
           this._activeTab = null;
       }
       $el[0].removeAttribute("data-group-id");
       item.setParent(null);
       item.removeClass("stacked");
       item.isStacked = false;
       item.setHidden(false);
       item.removeClass("stack-trayed");
       item.setRotation(0);
       // Force tabItem resize if it's dragged out of a stacked groupItem.
       // The tabItems's title will be visible and that's why we need to
       // recalculate its height.
       if (item.isDragging && this.isStacked())
         item.setBounds(item.getBounds(), true, {force: true});
       item.droppable(true);
       item.removeSubscriber("close", this._onChildClose);
       if (typeof item.setResizable == 'function')
         item.setResizable(true, options.immediately);
       // if a blank tab is selected while restoring a tab the blank tab gets
       // removed. we need to keep the group alive for the restored tab.
       if (item.isRemovedAfterRestore)
         options.dontClose = true;
       let closed = options.dontClose ? false : this.closeIfEmpty();
       if (closed ||
           (this._children.length == 0 && !gBrowser._numPinnedTabs &&
            !item.isDragging)) {
         this._makeLastActiveGroupItemActive();
       } else if (!options.dontArrange) {
         this.arrange({animate: !options.immediately});
         this._unfreezeItemSize({dontArrange: true});
       }
       this._sendToSubscribers("childRemoved", { item: item });
     } catch(e) {
       Utils.log(e);
     }
   },
   // ----------
   // Function: removeAll
   // Removes all of the groupItem's children.
   // The optional "options" param is passed to each remove call.
   removeAll: function GroupItem_removeAll(options) {
     let self = this;
     let newOptions = {dontArrange: true};
     if (options)
       Utils.extend(newOptions, options);
     let toRemove = this._children.concat();
     toRemove.forEach(function(child) {
       self.remove(child, newOptions);
     });
   },
   // ----------
   // Adds the given xul:tab as an app tab in this group's apptab tray
   //
   // Parameters:
   //   xulTab - the xul:tab.
   //   options - change how the app tab is added.
   //
   // Options:
   //   position - the position of the app tab should be added to.
   //   dontAdjustTray - (boolean) if true, do not adjust the tray.
   addAppTab: function GroupItem_addAppTab(xulTab, options) {
     GroupItems.getAppTabFavIconUrl(xulTab, function(iconUrl) {
       // The tab might have been removed or unpinned while waiting.
       if (!Utils.isValidXULTab(xulTab) || !xulTab.pinned)
         return;
       let self = this;
       let $appTab = iQ("<img>")
         .addClass("appTabIcon")
         .attr("src", iconUrl)
         .data("xulTab", xulTab)
         .mousedown(function GroupItem_addAppTab_onAppTabMousedown(event) {
           // stop mousedown propagation to disable group dragging on app tabs
           event.stopPropagation();
         })
         .click(function GroupItem_addAppTab_onAppTabClick(event) {
           if (!Utils.isLeftClick(event))
             return;
           UI.setActive(self, { dontSetActiveTabInGroup: true });
           UI.goToTab(iQ(this).data("xulTab"));
         });
       if (options && "position" in options) {
         let children = this.$appTabTray[0].childNodes;
         if (options.position >= children.length)
           $appTab.appendTo(this.$appTabTray);
         else
           this.$appTabTray[0].insertBefore($appTab[0], children[options.position]);
       } else {
         $appTab.appendTo(this.$appTabTray);
       }
       if (!options || !options.dontAdjustTray)
         this.adjustAppTabTray(true);
       this._sendToSubscribers("appTabIconAdded", { item: $appTab });
     }.bind(this));
   },
   // ----------
   // Removes the given xul:tab as an app tab in this group's apptab tray
   removeAppTab: function GroupItem_removeAppTab(xulTab) {
     // remove the icon
     iQ(".appTabIcon", this.$appTabTray).each(function(icon) {
       let $icon = iQ(icon);
       if ($icon.data("xulTab") != xulTab)
         return true;
       $icon.remove();
       return false;
     });
     // adjust the tray
     this.adjustAppTabTray(true);
   },
   // ----------
   // Arranges the given xul:tab as an app tab in the group's apptab tray
   arrangeAppTab: function GroupItem_arrangeAppTab(xulTab) {
     let self = this;
     let elements = iQ(".appTabIcon", this.$appTabTray);
     let length = elements.length;
     elements.each(function(icon) {
       let $icon = iQ(icon);
       if ($icon.data("xulTab") != xulTab)
         return true;
       let targetIndex = xulTab._tPos;
       $icon.remove({ preserveEventHandlers: true });
       if (targetIndex < (length - 1))
         self.$appTabTray[0].insertBefore(
           icon,
           iQ(".appTabIcon:nth-child(" + (targetIndex + 1) + ")", self.$appTabTray)[0]);
       else
         $icon.appendTo(self.$appTabTray);
       return false;
     });
   },
   // ----------
   // Function: hideExpandControl
   // Hide the control which expands a stacked groupItem into a quick-look view.
   hideExpandControl: function GroupItem_hideExpandControl() {
     this.$expander.hide();
   },
   // ----------
   // Function: showExpandControl
   // Show the control which expands a stacked groupItem into a quick-look view.
   showExpandControl: function GroupItem_showExpandControl() {
     let parentBB = this.getBounds();
     let childBB = this.getChild(0).getBounds();
     this.$expander
         .show()
         .css({
           left: parentBB.width/2 - this.$expander.width()/2
         });
   },
   // ----------
   // Function: shouldStack
   // Returns true if the groupItem, given "count", should stack (instead of
   // grid).
   shouldStack: function GroupItem_shouldStack(count) {
     let bb = this.getContentBounds();
     let options = {
       return: 'widthAndColumns',
       count: count || this._children.length,
       hideTitle: false
     };
     let arrObj = Items.arrange(this._children, bb, options);
     let shouldStack = arrObj.childWidth < TabItems.minTabWidth * 1.35;
     this._columns = shouldStack ? null : arrObj.columns;
     return shouldStack;
   },
   // ----------
   // Function: _freezeItemSize
   // Freezes current item size (when removing a child).
   //
   // Parameters:
   //   itemCount - the number of children before the last one was removed
   _freezeItemSize: function GroupItem__freezeItemSize(itemCount) {
     let data = this._frozenItemSizeData;
     if (!data.lastItemCount) {
       let self = this;
       data.lastItemCount = itemCount;
       // unfreeze item size when tabview is hidden
       data.onTabViewHidden = function () self._unfreezeItemSize();
       window.addEventListener('tabviewhidden', data.onTabViewHidden, false);
       // we don't need to observe mouse movement when expanded because the
       // tray is closed when we leave it and collapse causes unfreezing
       if (!self.expanded) {
         // unfreeze item size when cursor is moved out of group bounds
         data.onMouseMove = function (e) {
           let cursor = new Point(e.pageX, e.pageY);
           if (!self.bounds.contains(cursor))
             self._unfreezeItemSize();
         }
         iQ(window).mousemove(data.onMouseMove);
       }
     }
     this.arrange({animate: true, count: data.lastItemCount});
   },
   // ----------
   // Function: _unfreezeItemSize
   // Unfreezes and updates item size.
   //
   // Parameters:
   //   options - various options (see below)
   //
   // Possible options:
   //   dontArrange - do not arrange items when unfreezing
   _unfreezeItemSize: function GroupItem__unfreezeItemSize(options) {
     let data = this._frozenItemSizeData;
     if (!data.lastItemCount)
       return;
     if (!options || !options.dontArrange)
       this.arrange({animate: true});
     // unbind event listeners
     window.removeEventListener('tabviewhidden', data.onTabViewHidden, false);
     if (data.onMouseMove)
       iQ(window).unbind('mousemove', data.onMouseMove);
     // reset freeze status
     this._frozenItemSizeData = {};
   },
   // ----------
   // Function: arrange
   // Lays out all of the children.
   //
   // Parameters:
   //   options - passed to <Items.arrange> or <_stackArrange>, except those below
   //
   // Options:
   //   addTab - (boolean) if true, we add one to the child count
   //   oldDropIndex - if set, we will only set any bounds if the dropIndex has
   //                  changed
   //   dropPos - (<Point>) a position where a tab is currently positioned, above
   //             this group.
   //   animate - (boolean) if true, movement of children will be animated.
   //
   // Returns:
   //   dropIndex - an index value for where an item would be dropped, if
   //               options.dropPos is given.
   arrange: function GroupItem_arrange(options) {
     if (!options)
       options = {};
     let childrenToArrange = [];
     this._children.forEach(function(child) {
       if (child.isDragging)
         options.addTab = true;
       else
         childrenToArrange.push(child);
     });
     if (GroupItems._arrangePaused) {
       GroupItems.pushArrange(this, options);
       return false;
     }
     let shouldStack = this.shouldStack(childrenToArrange.length + (options.addTab ? 1 : 0));
     let shouldStackArrange = (shouldStack && !this.expanded);
     let box;
     // if we should stack and we're not expanded
     if (shouldStackArrange) {
       this.showExpandControl();
       box = this.getContentBounds({stacked: true});
       this._stackArrange(childrenToArrange, box, options);
       return false;
     } else {
       this.hideExpandControl();
       box = this.getContentBounds();
       // a dropIndex is returned
       return this._gridArrange(childrenToArrange, box, options);
     }
   },
   // ----------
   // Function: _stackArrange
   // Arranges the children in a stack.
   //
   // Parameters:
   //   childrenToArrange - array of <TabItem> children
   //   bb - <Rect> to arrange within
   //   options - see below
   //
   // Possible "options" properties:
   //   animate - whether to animate; default: true.
   _stackArrange: function GroupItem__stackArrange(childrenToArrange, bb, options) {
     if (!options)
       options = {};
     var animate = "animate" in options ? options.animate : true;
     var count = childrenToArrange.length;
     if (!count)
       return;
     let itemAspect = TabItems.tabHeight / TabItems.tabWidth;
     let zIndex = this.getZ() + count + 1;
     let maxRotation = 35; // degress
     let scale = 0.7;
     let newTabsPad = 10;
     let bbAspect = bb.height / bb.width;
     let numInPile = 6;
     let angleDelta = 3.5; // degrees
     // compute size of the entire stack, modulo rotation.
     let size;
     if (bbAspect > itemAspect) { // Tall, thin groupItem
       size = TabItems.calcValidSize(new Point(bb.width * scale, -1),
         {hideTitle:true});
      } else { // Short, wide groupItem
       size = TabItems.calcValidSize(new Point(-1, bb.height * scale),
         {hideTitle:true});
      }
     // x is the left margin that the stack will have, within the content area (bb)
     // y is the vertical margin
     var x = (bb.width - size.x) / 2;
     var y = Math.min(size.x, (bb.height - size.y) / 2);
     var box = new Rect(bb.left + x, bb.top + y, size.x, size.y);
     var self = this;
     var children = [];
     // ensure topChild is the first item in childrenToArrange
     let topChild = this.getTopChild();
     let topChildPos = childrenToArrange.indexOf(topChild);
     if (topChildPos > 0) {
       childrenToArrange.splice(topChildPos, 1);
       childrenToArrange.unshift(topChild);
     }
     childrenToArrange.forEach(function GroupItem__stackArrange_order(child) {
       // Children are still considered stacked even if they're hidden later.
       child.addClass("stacked");
       child.isStacked = true;
       if (numInPile-- > 0) {
         children.push(child);
       } else {
         child.setHidden(true);
       }
     });
     self._isStacked = true;
     let angleAccum = 0;
     children.forEach(function GroupItem__stackArrange_apply(child, index) {
       child.setZ(zIndex);
       zIndex--;
       // Force a recalculation of height because we've changed how the title
       // is shown.
       child.setBounds(box, !animate || child.getHidden(), {force:true});
       child.setRotation((UI.rtl ? -1 : 1) * angleAccum);
       child.setHidden(false);
       angleAccum += angleDelta;
     });
   },
   // ----------
   // Function: _gridArrange
   // Arranges the children into a grid.
   //
   // Parameters:
   //   childrenToArrange - array of <TabItem> children
   //   box - <Rect> to arrange within
   //   options - see below
   //
   // Possible "options" properties:
   //   animate - whether to animate; default: true.
   //   z - (int) a z-index to assign the children
   //   columns - the number of columns to use in the layout, if known in advance
   //
   // Returns:
   //   dropIndex - (int) the index at which a dragged item (if there is one) should be added
   //               if it is dropped. Otherwise (boolean) false.
   _gridArrange: function GroupItem__gridArrange(childrenToArrange, box, options) {
     let arrangeOptions;
     if (this.expanded) {
       // if we're expanded, we actually want to use the expanded tray's bounds.
       box = new Rect(this.expanded.bounds);
       box.inset(8, 8);
       arrangeOptions = Utils.extend({}, options, {z: 99999});
     } else {
       this._isStacked = false;
       arrangeOptions = Utils.extend({}, options, {
         columns: this._columns
       });
       childrenToArrange.forEach(function(child) {
         child.removeClass("stacked");
         child.isStacked = false;
         child.setHidden(false);
       });
     }
     if (!childrenToArrange.length)
       return false;
     // Items.arrange will determine where/how the child items should be
     // placed, but will *not* actually move them for us. This is our job.
     let result = Items.arrange(childrenToArrange, box, arrangeOptions);
     let {dropIndex, rects, columns} = result;
     if ("oldDropIndex" in options && options.oldDropIndex === dropIndex)
       return dropIndex;
     this._columns = columns;
     let index = 0;
     let self = this;
     childrenToArrange.forEach(function GroupItem_arrange_children_each(child, i) {
       // If dropIndex spacing is active and this is a child after index,
       // bump it up one so we actually use the correct rect
       // (and skip one for the dropPos)
       if (self._dropSpaceActive && index === dropIndex)
         index++;
       child.setBounds(rects[index], !options.animate);
       child.setRotation(0);
       if (arrangeOptions.z)
         child.setZ(arrangeOptions.z);
       index++;
     });
     return dropIndex;
   },
   expand: function GroupItem_expand() {
     var self = this;
     // ___ we're stacked, and command is held down so expand
     UI.setActive(this.getTopChild());
     var startBounds = this.getChild(0).getBounds();
     var $tray = iQ("<div>").css({
       top: startBounds.top,
       left: startBounds.left,
       width: startBounds.width,
       height: startBounds.height,
       position: "absolute",
       zIndex: 99998
     }).appendTo("body");
     $tray[0].id = "expandedTray";
     var w = 180;
     var h = w * (TabItems.tabHeight / TabItems.tabWidth) * 1.1;
     var padding = 20;
     var col = Math.ceil(Math.sqrt(this._children.length));
     var row = Math.ceil(this._children.length/col);
     var overlayWidth = Math.min(window.innerWidth - (padding * 2), w*col + padding*(col+1));
     var overlayHeight = Math.min(window.innerHeight - (padding * 2), h*row + padding*(row+1));
     var pos = {left: startBounds.left, top: startBounds.top};
     pos.left -= overlayWidth / 3;
     pos.top  -= overlayHeight / 3;
     if (pos.top < 0)
       pos.top = 20;
     if (pos.left < 0)
       pos.left = 20;
     if (pos.top + overlayHeight > window.innerHeight)
       pos.top = window.innerHeight - overlayHeight - 20;
     if (pos.left + overlayWidth > window.innerWidth)
       pos.left = window.innerWidth - overlayWidth - 20;
     $tray
       .animate({
         width:  overlayWidth,
         height: overlayHeight,
         top: pos.top,
         left: pos.left
       }, {
         duration: 200,
         easing: "tabviewBounce",
         complete: function GroupItem_expand_animate_complete() {
           self._sendToSubscribers("expanded");
         }
       })
       .addClass("overlay");
     this._children.forEach(function(child) {
       child.addClass("stack-trayed");
       child.setHidden(false);
     });
     var $shield = iQ('<div>')
       .addClass('shield')
       .css({
         zIndex: 99997
       })
       .appendTo('body')
       .click(function() { // just in case
         self.collapse();
       });
     // There is a race-condition here. If there is
     // a mouse-move while the shield is coming up
     // it will collapse, which we don't want. Thus,
     // we wait a little bit before adding this event
     // handler.
     setTimeout(function() {
       $shield.mouseover(function() {
         self.collapse();
       });
     }, 200);
     this.expanded = {
       $tray: $tray,
       $shield: $shield,
       bounds: new Rect(pos.left, pos.top, overlayWidth, overlayHeight)
     };
     this.arrange();
   },
   // ----------
   // Function: collapse
   // Collapses the groupItem from the expanded "tray" mode.
   collapse: function GroupItem_collapse() {
     if (this.expanded) {
       var z = this.getZ();
       var box = this.getBounds();
       let self = this;
       this.expanded.$tray
         .css({
           zIndex: z + 1
         })
         .animate({
           width:  box.width,
           height: box.height,
           top: box.top,
           left: box.left,
           opacity: 0
         }, {
           duration: 350,
           easing: "tabviewBounce",
           complete: function GroupItem_collapse_animate_complete() {
             iQ(this).remove();
             self._sendToSubscribers("collapsed");
           }
         });
       this.expanded.$shield.remove();
       this.expanded = null;
       this._children.forEach(function(child) {
         child.removeClass("stack-trayed");
       });
       this.arrange({z: z + 2});
       this._unfreezeItemSize({dontArrange: true});
     }
   },
   // ----------
   // Function: _addHandlers
   // Helper routine for the constructor; adds various event handlers to the container.
   _addHandlers: function GroupItem__addHandlers(container) {
     let self = this;
     let lastMouseDownTarget;
     container.mousedown(function(e) {
       let target = e.target;
       // only set the last mouse down target if it is a left click, not on the
       // close button, not on the expand button, not on the title bar and its
       // elements
       if (Utils.isLeftClick(e) &&
           self.$closeButton[0] != target &&
           self.$titlebar[0] != target &&
           self.$expander[0] != target &&
           !self.$titlebar.contains(target) &&
           !self.$appTabTray.contains(target)) {
         lastMouseDownTarget = target;
       } else {
         lastMouseDownTarget = null;
       }
     });
     container.mouseup(function(e) {
       let same = (e.target == lastMouseDownTarget);
       lastMouseDownTarget = null;
       if (same && !self.isDragging) {
         if (gBrowser.selectedTab.pinned &&
             UI.getActiveTab() != self.getActiveTab() &&
             self.getChildren().length > 0) {
           UI.setActive(self, { dontSetActiveTabInGroup: true });
           UI.goToTab(gBrowser.selectedTab);
         } else {
           let tabItem = self.getTopChild();
           if (tabItem)
             tabItem.zoomIn();
           else
             self.newTab();
         }
       }
     });
     let dropIndex = false;
     let dropSpaceTimer = null;
     // When the _dropSpaceActive flag is turned on on a group, and a tab is
     // dragged on top, a space will open up.
     this._dropSpaceActive = false;
     this.dropOptions.over = function GroupItem_dropOptions_over(event) {
       iQ(this.container).addClass("acceptsDrop");
     };
     this.dropOptions.move = function GroupItem_dropOptions_move(event) {
       let oldDropIndex = dropIndex;
       let dropPos = drag.info.item.getBounds().center();
       let options = {dropPos: dropPos,
                      addTab: self._dropSpaceActive && drag.info.item.parent != self,
                      oldDropIndex: oldDropIndex};
       let newDropIndex = self.arrange(options);
       // If this is a new drop index, start a timer!
       if (newDropIndex !== oldDropIndex) {
         dropIndex = newDropIndex;
         if (this._dropSpaceActive)
           return;
         if (dropSpaceTimer) {
           clearTimeout(dropSpaceTimer);
           dropSpaceTimer = null;
         }
         dropSpaceTimer = setTimeout(function GroupItem_arrange_evaluateDropSpace() {
           // Note that dropIndex's scope is GroupItem__addHandlers, but
           // newDropIndex's scope is GroupItem_dropOptions_move. Thus,
           // dropIndex may change with other movement events before we come
           // back and check this. If it's still the same dropIndex, activate
           // drop space display!
           if (dropIndex === newDropIndex) {
             self._dropSpaceActive = true;
             dropIndex = self.arrange({dropPos: dropPos,
                                       addTab: drag.info.item.parent != self,
                                       animate: true});
           }
           dropSpaceTimer = null;
         }, 250);
       }
     };
     this.dropOptions.drop = function GroupItem_dropOptions_drop(event) {
       iQ(this.container).removeClass("acceptsDrop");
       let options = {};
       if (this._dropSpaceActive)
         this._dropSpaceActive = false;
       if (dropSpaceTimer) {
         clearTimeout(dropSpaceTimer);
         dropSpaceTimer = null;
         // If we drop this item before the timed rearrange was executed,
         // we won't have an accurate dropIndex value. Get that now.
         let dropPos = drag.info.item.getBounds().center();
         dropIndex = self.arrange({dropPos: dropPos,
                                   addTab: drag.info.item.parent != self,
                                   animate: true});
       }
       if (dropIndex !== false)
         options = {index: dropIndex};
       this.add(drag.info.$el, options);
       UI.setActive(this);
       dropIndex = false;
     };
     this.dropOptions.out = function GroupItem_dropOptions_out(event) {
       dropIndex = false;
       if (this._dropSpaceActive)
         this._dropSpaceActive = false;
       if (dropSpaceTimer) {
         clearTimeout(dropSpaceTimer);
         dropSpaceTimer = null;
       }
       self.arrange();
       var groupItem = drag.info.item.parent;
       if (groupItem)
         groupItem.remove(drag.info.$el, {dontClose: true});
       iQ(this.container).removeClass("acceptsDrop");
     }
     this.draggable();
     this.droppable(true);
     this.$expander.click(function() {
       self.expand();
     });
   },
   // ----------
   // Function: setResizable
   // Sets whether the groupItem is resizable and updates the UI accordingly.
   setResizable: function GroupItem_setResizable(value, immediately) {
     var self = this;
     this.resizeOptions.minWidth = GroupItems.minGroupWidth;
     this.resizeOptions.minHeight = GroupItems.minGroupHeight;
     let start = this.resizeOptions.start;
     this.resizeOptions.start = function (event) {
       start.call(self, event);
       self._unfreezeItemSize();
     }
     if (value) {
       immediately ? this.$resizer.show() : this.$resizer.fadeIn();
       this.resizable(true);
     } else {
       immediately ? this.$resizer.hide() : this.$resizer.fadeOut();
       this.resizable(false);
     }
   },
   // ----------
   // Function: newTab
   // Creates a new tab within this groupItem.
   // Parameters:
   //  url - the new tab should open this url as well
   //  options - the options object
   //    dontZoomIn - set to true to not zoom into the newly created tab
   //    closedLastTab - boolean indicates the last tab has just been closed
   newTab: function GroupItem_newTab(url, options) {
     if (options && options.closedLastTab)
       UI.closedLastTabInTabView = true;
     UI.setActive(this, { dontSetActiveTabInGroup: true });
     let dontZoomIn = !!(options && options.dontZoomIn);
     return gBrowser.loadOneTab(url || gWindow.BROWSER_NEW_TAB_URL, { inBackground: dontZoomIn });
   },
   // ----------
   // Function: reorderTabItemsBasedOnTabOrder
   // Reorders the tabs in a groupItem based on the arrangment of the tabs
   // shown in the tab bar. It does it by sorting the children
   // of the groupItem by the positions of their respective tabs in the
   // tab bar.
   reorderTabItemsBasedOnTabOrder: function GroupItem_reorderTabItemsBasedOnTabOrder() {
     this._children.sort(function(a,b) a.tab._tPos - b.tab._tPos);
     this.arrange({animate: false});
     // this.arrange calls this.save for us
   },
   // Function: reorderTabsBasedOnTabItemOrder
   // Reorders the tabs in the tab bar based on the arrangment of the tabs
   // shown in the groupItem.
   reorderTabsBasedOnTabItemOrder: function GroupItem_reorderTabsBasedOnTabItemOrder() {
     let indices;
     let tabs = this._children.map(function (tabItem) tabItem.tab);
     tabs.forEach(function (tab, index) {
       if (!indices)
         indices = tabs.map(function (tab) tab._tPos);
       let start = index ? indices[index - 1] + 1 : 0;
       let end = index + 1 < indices.length ? indices[index + 1] - 1 : Infinity;
       let targetRange = new Range(start, end);
       if (!targetRange.contains(tab._tPos)) {
         gBrowser.moveTabTo(tab, start);
         indices = null;
       }
     });
   },
   // ----------
   // Function: getTopChild
   // Gets the <Item> that should be displayed on top when in stack mode.
   getTopChild: function GroupItem_getTopChild() {
     if (!this.getChildren().length) {
       return null;
     }
     return this.getActiveTab() || this.getChild(0);
   },
   // ----------
   // Function: getChild
   // Returns the nth child tab or null if index is out of range.
   //
   // Parameters:
   //  index - the index of the child tab to return, use negative
   //          numbers to index from the end (-1 is the last child)
   getChild: function GroupItem_getChild(index) {
     if (index < 0)
       index = this._children.length + index;
     if (index >= this._children.length || index < 0)
       return null;
     return this._children[index];
   },
   // ----------
   // Function: getChildren
   // Returns all children.
   getChildren: function GroupItem_getChildren() {
     return this._children;
   }
 });
 // ##########
 // Class: GroupItems
 // Singleton for managing all <GroupItem>s.
 let GroupItems = {
   groupItems: [],
   nextID: 1,
   _inited: false,
   _activeGroupItem: null,
   _cleanupFunctions: [],
   _arrangePaused: false,
   _arrangesPending: [],
   _removingHiddenGroups: false,
   _delayedModUpdates: [],
   _autoclosePaused: false,
   minGroupHeight: 110,
   minGroupWidth: 125,
   _lastActiveList: null,
   // ----------
   // Function: toString
   // Prints [GroupItems] for debug use
   toString: function GroupItems_toString() {
     return "[GroupItems count=" + this.groupItems.length + "]";
   },
   // ----------
   // Function: init
   init: function GroupItems_init() {
     let self = this;
     // setup attr modified handler, and prepare for its uninit
     function handleAttrModified(event) {
       self._handleAttrModified(event.target);
     }
     // make sure any closed tabs are removed from the delay update list
     function handleClose(event) {
       let idx = self._delayedModUpdates.indexOf(event.target);
       if (idx != -1)
         self._delayedModUpdates.splice(idx, 1);
     }
     this._lastActiveList = new MRUList();
     AllTabs.register("attrModified", handleAttrModified);
     AllTabs.register("close", handleClose);
     this._cleanupFunctions.push(function() {
       AllTabs.unregister("attrModified", handleAttrModified);
       AllTabs.unregister("close", handleClose);
     });
   },
   // ----------
   // Function: uninit
   uninit: function GroupItems_uninit() {
     // call our cleanup functions
     this._cleanupFunctions.forEach(function(func) {
       func();
     });
     this._cleanupFunctions = [];
     // additional clean up
     this.groupItems = null;
   },
   // ----------
   // Function: newGroup
   // Creates a new empty group.
   newGroup: function GroupItems_newGroup() {
     let bounds = new Rect(20, 20, 250, 200);
     return new GroupItem([], {bounds: bounds, immediately: true});
   },
   // ----------
   // Function: pauseArrange
   // Bypass arrange() calls and collect for resolution in
   // resumeArrange()
   pauseArrange: function GroupItems_pauseArrange() {
     Utils.assert(this._arrangePaused == false,
       "pauseArrange has been called while already paused");
     Utils.assert(this._arrangesPending.length == 0,
       "There are bypassed arrange() calls that haven't been resolved");
     this._arrangePaused = true;
   },
   // ----------
   // Function: pushArrange
   // Push an arrange() call and its arguments onto an array
   // to be resolved in resumeArrange()
   pushArrange: function GroupItems_pushArrange(groupItem, options) {
     Utils.assert(this._arrangePaused,
       "Ensure pushArrange() called while arrange()s aren't paused");
     let i;
     for (i = 0; i < this._arrangesPending.length; i++)
       if (this._arrangesPending[i].groupItem === groupItem)
         break;
     let arrangeInfo = {
       groupItem: groupItem,
       options: options
     };
     if (i < this._arrangesPending.length)
       this._arrangesPending[i] = arrangeInfo;
     else
       this._arrangesPending.push(arrangeInfo);
   },
   // ----------
   // Function: resumeArrange
   // Resolve bypassed and collected arrange() calls
   resumeArrange: function GroupItems_resumeArrange() {
     this._arrangePaused = false;
     for (let i = 0; i < this._arrangesPending.length; i++) {
       let g = this._arrangesPending[i];
       g.groupItem.arrange(g.options);
     }
     this._arrangesPending = [];
   },
   // ----------
   // Function: _handleAttrModified
   // watch for icon changes on app tabs
   _handleAttrModified: function GroupItems__handleAttrModified(xulTab) {
     if (!UI.isTabViewVisible()) {
       if (this._delayedModUpdates.indexOf(xulTab) == -1) {
         this._delayedModUpdates.push(xulTab);
       }
     } else
       this._updateAppTabIcons(xulTab);
   },
   // ----------
   // Function: flushTabUpdates
   // Update apptab icons based on xulTabs which have been updated
   // while the TabView hasn't been visible
   flushAppTabUpdates: function GroupItems_flushAppTabUpdates() {
     let self = this;
     this._delayedModUpdates.forEach(function(xulTab) {
       self._updateAppTabIcons(xulTab);
     });
     this._delayedModUpdates = [];
   },
   // ----------
   // Function: _updateAppTabIcons
   // Update images of any apptab icons that point to passed in xultab
   _updateAppTabIcons: function GroupItems__updateAppTabIcons(xulTab) {
     if (!xulTab.pinned)
       return;
     this.getAppTabFavIconUrl(xulTab, function(iconUrl) {
       iQ(".appTabIcon").each(function GroupItems__updateAppTabIcons_forEach(icon) {
          let $icon = iQ(icon);
          if ($icon.data("xulTab") == xulTab && iconUrl != $icon.attr("src"))
            $icon.attr("src", iconUrl);
       });
     });
   },
   // ----------
   // Function: getAppTabFavIconUrl
   // Gets the fav icon url for app tab.
   getAppTabFavIconUrl: function GroupItems_getAppTabFavIconUrl(xulTab, callback) {
     FavIcons.getFavIconUrlForTab(xulTab, function GroupItems_getAppTabFavIconUrl_getFavIconUrlForTab(iconUrl) {
       callback(iconUrl || FavIcons.defaultFavicon);
     });
   },
   // ----------
   // Function: addAppTab
   // Adds the given xul:tab to the app tab tray in all groups
   addAppTab: function GroupItems_addAppTab(xulTab) {
     this.groupItems.forEach(function(groupItem) {
       groupItem.addAppTab(xulTab);
     });
     this.updateGroupCloseButtons();
   },
   // ----------
   // Function: removeAppTab
   // Removes the given xul:tab from the app tab tray in all groups
   removeAppTab: function GroupItems_removeAppTab(xulTab) {
     this.groupItems.forEach(function(groupItem) {
       groupItem.removeAppTab(xulTab);
     });
     this.updateGroupCloseButtons();
   },
   // ----------
   // Function: arrangeAppTab
   // Arranges the given xul:tab as an app tab from app tab tray in all groups
   arrangeAppTab: function GroupItems_arrangeAppTab(xulTab) {
     this.groupItems.forEach(function(groupItem) {
       groupItem.arrangeAppTab(xulTab);
     });
   },
   // ----------
   // Function: getNextID
   // Returns the next unused groupItem ID.
   getNextID: function GroupItems_getNextID() {
     var result = this.nextID;
     this.nextID++;
     this._save();
     return result;
   },
   // ----------
   // Function: saveAll
   // Saves GroupItems state, as well as the state of all of the groupItems.
   saveAll: function GroupItems_saveAll() {
     this._save();
     this.groupItems.forEach(function(groupItem) {
       groupItem.save();
     });
   },
   // ----------
   // Function: _save
   // Saves GroupItems state.
   _save: function GroupItems__save() {
     if (!this._inited) // too soon to save now
       return;
     let activeGroupId = this._activeGroupItem ? this._activeGroupItem.id : null;
     Storage.saveGroupItemsData(
       gWindow,
       { nextID: this.nextID, activeGroupId: activeGroupId,
         totalNumber: this.groupItems.length });
   },
   // ----------
   // Function: getBoundingBox
   // Given an array of DOM elements, returns a <Rect> with (roughly) the union of their locations.
   getBoundingBox: function GroupItems_getBoundingBox(els) {
     var bounds = [iQ(el).bounds() for each (el in els)];
     var left   = Math.min.apply({},[ b.left   for each (b in bounds) ]);
     var top    = Math.min.apply({},[ b.top    for each (b in bounds) ]);
     var right  = Math.max.apply({},[ b.right  for each (b in bounds) ]);
     var bottom = Math.max.apply({},[ b.bottom for each (b in bounds) ]);
     return new Rect(left, top, right-left, bottom-top);
   },
   // ----------
   // Function: reconstitute
   // Restores to stored state, creating groupItems as needed.
   reconstitute: function GroupItems_reconstitute(groupItemsData, groupItemData) {
     try {
       let activeGroupId;
       if (groupItemsData) {
         if (groupItemsData.nextID)
           this.nextID = Math.max(this.nextID, groupItemsData.nextID);
         if (groupItemsData.activeGroupId)
           activeGroupId = groupItemsData.activeGroupId;
       }
       if (groupItemData) {
         var toClose = this.groupItems.concat();
         for (var id in groupItemData) {
           let data = groupItemData[id];
           if (this.groupItemStorageSanity(data)) {
             let groupItem = this.groupItem(data.id);
             if (groupItem && !groupItem.hidden) {
               groupItem.userSize = data.userSize;
               groupItem.setTitle(data.title);
               groupItem.setBounds(data.bounds, true);
               let index = toClose.indexOf(groupItem);
               if (index != -1)
                 toClose.splice(index, 1);
             } else {
               var options = {
                 dontPush: true,
                 immediately: true
               };
               new GroupItem([], Utils.extend({}, data, options));
             }
           }
         }
         toClose.forEach(function(groupItem) {
           // all tabs still existing in closed groups will be moved to new
           // groups. prepare them to be reconnected later.
           groupItem.getChildren().forEach(function (tabItem) {
             if (tabItem.parent.hidden)
               iQ(tabItem.container).show();
             tabItem._reconnected = false;
             // sanity check the tab's groupID
             let tabData = Storage.getTabData(tabItem.tab);
             if (tabData) {
               let parentGroup = GroupItems.groupItem(tabData.groupID);
               // the tab's group id could be invalid or point to a non-existing
               // group. correct it by assigning the active group id or the first
               // group of the just restored session.
               if (!parentGroup || -1 < toClose.indexOf(parentGroup)) {
                 tabData.groupID = activeGroupId || Object.keys(groupItemData)[0];
                 Storage.saveTab(tabItem.tab, tabData);
               }
             }
           });
           // this closes the group but not its children
           groupItem.close({immediately: true});
         });
       }
       // set active group item
       if (activeGroupId) {
         let activeGroupItem = this.groupItem(activeGroupId);
         if (activeGroupItem)
           UI.setActive(activeGroupItem);
       }
       this._inited = true;
       this._save(); // for nextID
     } catch(e) {
       Utils.log("error in recons: "+e);
     }
   },
   // ----------
   // Function: load
   // Loads the storage data for groups.
   // Returns true if there was global group data.
   load: function GroupItems_load() {
     let groupItemsData = Storage.readGroupItemsData(gWindow);
     let groupItemData = Storage.readGroupItemData(gWindow);
     this.reconstitute(groupItemsData, groupItemData);
     return (groupItemsData && !Utils.isEmptyObject(groupItemsData));
   },
   // ----------
   // Function: groupItemStorageSanity
   // Given persistent storage data for a groupItem, returns true if it appears to not be damaged.
   groupItemStorageSanity: function GroupItems_groupItemStorageSanity(groupItemData) {
     let sane = true;
     if (!groupItemData.bounds || !Utils.isRect(groupItemData.bounds)) {
       Utils.log('GroupItems.groupItemStorageSanity: bad bounds', groupItemData.bounds);
       sane = false;
     } else if ((groupItemData.userSize &&
                !Utils.isPoint(groupItemData.userSize)) ||
                !groupItemData.id) {
       sane = false;
     }
     return sane;
   },
   // ----------
   // Function: register
   // Adds the given <GroupItem> to the list of groupItems we're tracking.
   register: function GroupItems_register(groupItem) {
     Utils.assert(groupItem, 'groupItem');
     Utils.assert(this.groupItems.indexOf(groupItem) == -1, 'only register once per groupItem');
     this.groupItems.push(groupItem);
     UI.updateTabButton();
   },
   // ----------
   // Function: unregister
   // Removes the given <GroupItem> from the list of groupItems we're tracking.
   unregister: function GroupItems_unregister(groupItem) {
     var index = this.groupItems.indexOf(groupItem);
     if (index != -1)
       this.groupItems.splice(index, 1);
     if (groupItem == this._activeGroupItem)
       this._activeGroupItem = null;
     this._arrangesPending = this._arrangesPending.filter(function (pending) {
       return groupItem != pending.groupItem;
     });
     this._lastActiveList.remove(groupItem);
     UI.updateTabButton();
   },
   // ----------
   // Function: groupItem
   // Given some sort of identifier, returns the appropriate groupItem.
   // Currently only supports groupItem ids.
   groupItem: function GroupItems_groupItem(a) {
     if (!this.groupItems) {
       // uninit has been called
       return null;
     }
     var result = null;
     this.groupItems.forEach(function(candidate) {
       if (candidate.id == a)
         result = candidate;
     });
     return result;
   },
   // ----------
   // Function: removeAll
   // Removes all tabs from all groupItems (which automatically closes all unnamed groupItems).
   removeAll: function GroupItems_removeAll() {
     var toRemove = this.groupItems.concat();
     toRemove.forEach(function(groupItem) {
       groupItem.removeAll();
     });
   },
   // ----------
   // Function: newTab
   // Given a <TabItem>, files it in the appropriate groupItem.
   newTab: function GroupItems_newTab(tabItem, options) {
     let activeGroupItem = this.getActiveGroupItem();
     // 1. Active group
     // 2. First visible non-app tab (that's not the tab in question)
     // 3. First group
     // 4. At this point there should be no groups or tabs (except for app tabs and the
     // tab in question): make a new group
     if (activeGroupItem && !activeGroupItem.hidden) {
       activeGroupItem.add(tabItem, options);
       return;
     }
     let targetGroupItem;
     // find first non-app visible tab belongs a group, and add the new tabItem
     // to that group
     gBrowser.visibleTabs.some(function(tab) {
       if (!tab.pinned && tab != tabItem.tab) {
         if (tab._tabViewTabItem && tab._tabViewTabItem.parent &&
             !tab._tabViewTabItem.parent.hidden) {
           targetGroupItem = tab._tabViewTabItem.parent;
         }
         return true;
       }
       return false;
     });
     let visibleGroupItems;
     if (targetGroupItem) {
       // add the new tabItem to the first group item
       targetGroupItem.add(tabItem);
       UI.setActive(targetGroupItem);
       return;
     } else {
       // find the first visible group item
       visibleGroupItems = this.groupItems.filter(function(groupItem) {
         return (!groupItem.hidden);
       });
       if (visibleGroupItems.length > 0) {
         visibleGroupItems[0].add(tabItem);
         UI.setActive(visibleGroupItems[0]);
         return;
       }
     }
     // create new group for the new tabItem
     tabItem.setPosition(60, 60, true);
     let newGroupItemBounds = tabItem.getBounds();
     newGroupItemBounds.inset(-40,-40);
     let newGroupItem = new GroupItem([tabItem], { bounds: newGroupItemBounds });
     newGroupItem.snap();
     UI.setActive(newGroupItem);
   },
   // ----------
   // Function: getActiveGroupItem
   // Returns the active groupItem. Active means its tabs are
   // shown in the tab bar when not in the TabView interface.
   getActiveGroupItem: function GroupItems_getActiveGroupItem() {
     return this._activeGroupItem;
   },
   // ----------
   // Function: setActiveGroupItem
   // Sets the active groupItem, thereby showing only the relevant tabs and
   // setting the groupItem which will receive new tabs.
   //
   // Paramaters:
   //  groupItem - the active <GroupItem>
   setActiveGroupItem: function GroupItems_setActiveGroupItem(groupItem) {
     Utils.assert(groupItem, "groupItem must be given");
     if (this._activeGroupItem)
       iQ(this._activeGroupItem.container).removeClass('activeGroupItem');
     iQ(groupItem.container).addClass('activeGroupItem');
     this._lastActiveList.update(groupItem);
     this._activeGroupItem = groupItem;
     this._save();
   },
   // ----------
   // Function: getLastActiveGroupItem
   // Gets last active group item.
   // Returns the <groupItem>. If nothing is found, return null.
   getLastActiveGroupItem: function GroupItem_getLastActiveGroupItem() {
     return this._lastActiveList.peek(function(groupItem) {
       return (groupItem && !groupItem.hidden && groupItem.getChildren().length > 0)
     });
   },
   // ----------
   // Function: _updateTabBar
   // Hides and shows tabs in the tab bar based on the active groupItem
   _updateTabBar: function GroupItems__updateTabBar() {
     if (!window.UI)
       return; // called too soon
     Utils.assert(this._activeGroupItem, "There must be something to show in the tab bar!");
     let tabItems = this._activeGroupItem._children;
     gBrowser.showOnlyTheseTabs(tabItems.map(function(item) item.tab));
   },
   // ----------
   // Function: updateActiveGroupItemAndTabBar
   // Sets active TabItem and GroupItem, and updates tab bar appropriately.
   // Parameters:
   // tabItem - the tab item
   // options - is passed to UI.setActive() directly
   updateActiveGroupItemAndTabBar:
     function GroupItems_updateActiveGroupItemAndTabBar(tabItem, options) {
     Utils.assertThrow(tabItem && tabItem.isATabItem, "tabItem must be a TabItem");
     UI.setActive(tabItem, options);
     this._updateTabBar();
   },
   // ----------
   // Function: getNextGroupItemTab
   // Paramaters:
   //  reverse - the boolean indicates the direction to look for the next groupItem.
   // Returns the <tabItem>. If nothing is found, return null.
   getNextGroupItemTab: function GroupItems_getNextGroupItemTab(reverse) {
     var groupItems = Utils.copy(GroupItems.groupItems);
     var activeGroupItem = GroupItems.getActiveGroupItem();
     var tabItem = null;
     if (reverse)
       groupItems = groupItems.reverse();
     if (!activeGroupItem) {
       if (groupItems.length > 0) {
         groupItems.some(function(groupItem) {
           if (!groupItem.hidden) {
             // restore the last active tab in the group
             let activeTab = groupItem.getActiveTab();
             if (activeTab) {
               tabItem = activeTab;
               return true;
             }
             // if no tab is active, use the first one
             var child = groupItem.getChild(0);
             if (child) {
               tabItem = child;
               return true;
             }
           }
           return false;
         });
       }
     } else {
       var currentIndex;
       groupItems.some(function(groupItem, index) {
         if (!groupItem.hidden && groupItem == activeGroupItem) {
           currentIndex = index;
           return true;
         }
         return false;
       });
       var firstGroupItems = groupItems.slice(currentIndex + 1);
       firstGroupItems.some(function(groupItem) {
         if (!groupItem.hidden) {
           // restore the last active tab in the group
           let activeTab = groupItem.getActiveTab();
           if (activeTab) {
             tabItem = activeTab;
             return true;
           }
           // if no tab is active, use the first one
           var child = groupItem.getChild(0);
           if (child) {
             tabItem = child;
             return true;
           }
         }
         return false;
       });
       if (!tabItem) {
         var secondGroupItems = groupItems.slice(0, currentIndex);
         secondGroupItems.some(function(groupItem) {
           if (!groupItem.hidden) {
             // restore the last active tab in the group
             let activeTab = groupItem.getActiveTab();
             if (activeTab) {
               tabItem = activeTab;
               return true;
             }
             // if no tab is active, use the first one
             var child = groupItem.getChild(0);
             if (child) {
               tabItem = child;
               return true;
             }
           }
           return false;
         });
       }
     }
     return tabItem;
   },
   // ----------
   // Function: moveTabToGroupItem
   // Used for the right click menu in the tab strip; moves the given tab
   // into the given group. Does nothing if the tab is an app tab.
   // Paramaters:
   //  tab - the <xul:tab>.
   //  groupItemId - the <groupItem>'s id.  If nothing, create a new <groupItem>.
   moveTabToGroupItem : function GroupItems_moveTabToGroupItem(tab, groupItemId) {
     if (tab.pinned)
       return;
     Utils.assertThrow(tab._tabViewTabItem, "tab must be linked to a TabItem");
     // given tab is already contained in target group
     if (tab._tabViewTabItem.parent && tab._tabViewTabItem.parent.id == groupItemId)
       return;
     let shouldUpdateTabBar = false;
     let shouldShowTabView = false;
     let groupItem;
     // switch to the appropriate tab first.
     if (tab.selected) {
       if (gBrowser.visibleTabs.length > 1) {
         gBrowser._blurTab(tab);
         shouldUpdateTabBar = true;
       } else {
         shouldShowTabView = true;
       }
     } else {
       shouldUpdateTabBar = true
     }
     // remove tab item from a groupItem
     if (tab._tabViewTabItem.parent)
       tab._tabViewTabItem.parent.remove(tab._tabViewTabItem);
     // add tab item to a groupItem
     if (groupItemId) {
       groupItem = GroupItems.groupItem(groupItemId);
       groupItem.add(tab._tabViewTabItem);
       groupItem.reorderTabsBasedOnTabItemOrder()
     } else {
       let pageBounds = Items.getPageBounds();
       pageBounds.inset(20, 20);
       let box = new Rect(pageBounds);
       box.width = 250;
       box.height = 200;
       new GroupItem([ tab._tabViewTabItem ], { bounds: box, immediately: true });
     }
     if (shouldUpdateTabBar)
       this._updateTabBar();
     else if (shouldShowTabView)
       UI.showTabView();
   },
   // ----------
   // Function: removeHiddenGroups
   // Removes all hidden groups' data and its browser tabs.
   removeHiddenGroups: function GroupItems_removeHiddenGroups() {
     if (this._removingHiddenGroups)
       return;
     this._removingHiddenGroups = true;
     let groupItems = this.groupItems.concat();
     groupItems.forEach(function(groupItem) {
       if (groupItem.hidden)
         groupItem.closeHidden();
      });
     this._removingHiddenGroups = false;
   },
   // ----------
   // Function: getUnclosableGroupItemId
   // If there's only one (non-hidden) group, and there are app tabs present,
   // returns that group.
   // Return the <GroupItem>'s Id
   getUnclosableGroupItemId: function GroupItems_getUnclosableGroupItemId() {
     let unclosableGroupItemId = null;
     if (gBrowser._numPinnedTabs > 0) {
       let hiddenGroupItems =
         this.groupItems.concat().filter(function(groupItem) {
           return !groupItem.hidden;
         });
       if (hiddenGroupItems.length == 1)
         unclosableGroupItemId = hiddenGroupItems[0].id;
     }
     return unclosableGroupItemId;
   },
   // ----------
   // Function: updateGroupCloseButtons
   // Updates group close buttons.
   updateGroupCloseButtons: function GroupItems_updateGroupCloseButtons() {
     let unclosableGroupItemId = this.getUnclosableGroupItemId();
     if (unclosableGroupItemId) {
       let groupItem = this.groupItem(unclosableGroupItemId);
       if (groupItem) {
         groupItem.$closeButton.hide();
       }
     } else {
       this.groupItems.forEach(function(groupItem) {
         groupItem.$closeButton.show();
       });
     }
   },
   // ----------
   // Function: calcValidSize
   // Basic measure rules. Assures that item is a minimum size.
   calcValidSize: function GroupItems_calcValidSize(size, options) {
     Utils.assert(Utils.isPoint(size), 'input is a Point');
     Utils.assert((size.x>0 || size.y>0) && (size.x!=0 && size.y!=0),
       "dimensions are valid:"+size.x+","+size.y);
     return new Point(
       Math.max(size.x, GroupItems.minGroupWidth),
       Math.max(size.y, GroupItems.minGroupHeight));
   },
   // ----------
   // Function: pauseAutoclose()
   // Temporarily disable the behavior that closes groups when they become
   // empty. This is used when entering private browsing, to avoid trashing the
   // user's groups while private browsing is shuffling things around.
   pauseAutoclose: function GroupItems_pauseAutoclose() {
     this._autoclosePaused = true;
   },
   // ----------
   // Function: unpauseAutoclose()
   // Re-enables the auto-close behavior.
   resumeAutoclose: function GroupItems_resumeAutoclose() {
     this._autoclosePaused = false;
   }
 };