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

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

browser/components/tabview/tabitems.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: tabitems.js
 // ##########
 // Class: TabItem
 // An <Item> that represents a tab. Also implements the <Subscribable> interface.
 //
 // Parameters:
 //   tab - a xul:tab
 function TabItem(tab, options) {
   Utils.assert(tab, "tab");
   this.tab = tab;
   // register this as the tab's tabItem
   this.tab._tabViewTabItem = this;
   if (!options)
     options = {};
   // ___ set up div
   document.body.appendChild(TabItems.fragment().cloneNode(true));
   // The document fragment contains just one Node
   // As per DOM3 appendChild: it will then be the last child
   let div = document.body.lastChild;
   let $div = iQ(div);
   this._showsCachedData = false;
   this.canvasSizeForced = false;
   this.$thumb = iQ('.thumb', $div);
   this.$fav   = iQ('.favicon', $div);
   this.$tabTitle = iQ('.tab-title', $div);
   this.$canvas = iQ('.thumb canvas', $div);
   this.$cachedThumb = iQ('img.cached-thumb', $div);
   this.$favImage = iQ('.favicon>img', $div);
   this.$close = iQ('.close', $div);
   this.tabCanvas = new TabCanvas(this.tab, this.$canvas[0]);
   this._hidden = false;
   this.isATabItem = true;
   this.keepProportional = true;
   this._hasBeenDrawn = false;
   this._reconnected = false;
   this.isDragging = false;
   this.isStacked = false;
   // Read off the total vertical and horizontal padding on the tab container
   // and cache this value, as it must be the same for every TabItem.
   if (Utils.isEmptyObject(TabItems.tabItemPadding)) {
     TabItems.tabItemPadding.x = parseInt($div.css('padding-left'))
         + parseInt($div.css('padding-right'));
     TabItems.tabItemPadding.y = parseInt($div.css('padding-top'))
         + parseInt($div.css('padding-bottom'));
   }
   this.bounds = new Rect(0,0,1,1);
   this._lastTabUpdateTime = Date.now();
   // ___ superclass setup
   this._init(div);
   // ___ drag/drop
   // override dropOptions with custom tabitem methods
   this.dropOptions.drop = function(e) {
     let groupItem = drag.info.item.parent;
     groupItem.add(drag.info.$el);
   };
   this.draggable();
   let self = this;
   // ___ more div setup
   $div.mousedown(function(e) {
     if (!Utils.isRightClick(e))
       self.lastMouseDownTarget = e.target;
   });
   $div.mouseup(function(e) {
     var same = (e.target == self.lastMouseDownTarget);
     self.lastMouseDownTarget = null;
     if (!same)
       return;
     // press close button or middle mouse click
     if (iQ(e.target).hasClass("close") || Utils.isMiddleClick(e)) {
       self.closedManually = true;
       self.close();
     } else {
       if (!Items.item(this).isDragging)
         self.zoomIn();
     }
   });
   this.droppable(true);
   this.$close.attr("title", tabbrowserString("tabs.closeTab"));
   TabItems.register(this);
   // ___ reconnect to data from Storage
   if (!TabItems.reconnectingPaused())
     this._reconnect(options);
 };
 TabItem.prototype = Utils.extend(new Item(), new Subscribable(), {
   // ----------
   // Function: toString
   // Prints [TabItem (tab)] for debug use
   toString: function TabItem_toString() {
     return "[TabItem (" + this.tab + ")]";
   },
   // ----------
   // Function: forceCanvasSize
   // Repaints the thumbnail with the given resolution, and forces it
   // to stay that resolution until unforceCanvasSize is called.
   forceCanvasSize: function TabItem_forceCanvasSize(w, h) {
     this.canvasSizeForced = true;
     this.$canvas[0].width = w;
     this.$canvas[0].height = h;
     this.tabCanvas.paint();
   },
   // ----------
   // Function: unforceCanvasSize
   // Stops holding the thumbnail resolution; allows it to shift to the
   // size of thumbnail on screen. Note that this call does not nest, unlike
   // <TabItems.resumePainting>; if you call forceCanvasSize multiple
   // times, you just need a single unforce to clear them all.
   unforceCanvasSize: function TabItem_unforceCanvasSize() {
     this.canvasSizeForced = false;
   },
   // ----------
   // Function: isShowingCachedData
   // Returns a boolean indicates whether the cached data is being displayed or
   // not.
   isShowingCachedData: function TabItem_isShowingCachedData() {
     return this._showsCachedData;
   },
   // ----------
   // Function: showCachedData
   // Shows the cached data i.e. image and title.  Note: this method should only
   // be called at browser startup with the cached data avaliable.
   showCachedData: function TabItem_showCachedData() {
     let {title, url} = this.getTabState();
     let thumbnailURL = gPageThumbnails.getThumbnailURL(url);
     this.$cachedThumb.attr("src", thumbnailURL).show();
     this.$canvas.css({opacity: 0});
     let tooltip = (title && title != url ? title + "\n" + url : url);
     this.$tabTitle.text(title).attr("title", tooltip);
     this._showsCachedData = true;
   },
   // ----------
   // Function: hideCachedData
   // Hides the cached data i.e. image and title and show the canvas.
   hideCachedData: function TabItem_hideCachedData() {
     this.$cachedThumb.attr("src", "").hide();
     this.$canvas.css({opacity: 1.0});
     this._showsCachedData = false;
   },
   // ----------
   // Function: getStorageData
   // Get data to be used for persistent storage of this object.
   getStorageData: function TabItem_getStorageData() {
     let data = {
       groupID: (this.parent ? this.parent.id : 0)
     };
     if (this.parent && this.parent.getActiveTab() == this)
       data.active = true;
     return data;
   },
   // ----------
   // Function: save
   // Store persistent for this object.
   save: function TabItem_save() {
     try {
       if (!this.tab || !Utils.isValidXULTab(this.tab) || !this._reconnected) // too soon/late to save
         return;
       let data = this.getStorageData();
       if (TabItems.storageSanity(data))
         Storage.saveTab(this.tab, data);
     } catch(e) {
       Utils.log("Error in saving tab value: "+e);
     }
   },
   // ----------
   // Function: _getCurrentTabStateEntry
   // Returns the current tab state's active history entry.
   _getCurrentTabStateEntry: function TabItem__getCurrentTabStateEntry() {
     let tabState = Storage.getTabState(this.tab);
     if (tabState) {
       let index = (tabState.index || tabState.entries.length) - 1;
       if (index in tabState.entries)
         return tabState.entries[index];
     }
     return null;
   },
   // ----------
   // Function: getTabState
   // Returns the current tab state, i.e. the title and URL of the active
   // history entry.
   getTabState: function TabItem_getTabState() {
     let entry = this._getCurrentTabStateEntry();
     let title = "";
     let url = "";
     if (entry) {
       if (entry.title)
         title = entry.title;
       url = entry.url;
     } else {
       url = this.tab.linkedBrowser.currentURI.spec;
     }
     return {title: title, url: url};
   },
   // ----------
   // Function: _reconnect
   // Load the reciever's persistent data from storage. If there is none,
   // treats it as a new tab.
   //
   // Parameters:
   //   options - an object with additional parameters, see below
   //
   // Possible options:
   //   groupItemId - if the tab doesn't have any data associated with it and
   //                 groupItemId is available, add the tab to that group.
   _reconnect: function TabItem__reconnect(options) {
     Utils.assertThrow(!this._reconnected, "shouldn't already be reconnected");
     Utils.assertThrow(this.tab, "should have a xul:tab");
     let tabData = Storage.getTabData(this.tab);
     let groupItem;
     if (tabData && TabItems.storageSanity(tabData)) {
       // Show the cached data while we're waiting for the tabItem to be updated.
       // If the tab isn't restored yet this acts as a placeholder until it is.
       this.showCachedData();
       if (this.parent)
         this.parent.remove(this, {immediately: true});
       if (tabData.groupID)
         groupItem = GroupItems.groupItem(tabData.groupID);
       else
         groupItem = new GroupItem([], {immediately: true, bounds: tabData.bounds});
       if (groupItem) {
         groupItem.add(this, {immediately: true});
         // restore the active tab for each group between browser sessions
         if (tabData.active)
           groupItem.setActiveTab(this);
         // if it matches the selected tab or no active tab and the browser
         // tab is hidden, the active group item would be set.
         if (this.tab.selected ||
             (!GroupItems.getActiveGroupItem() && !this.tab.hidden))
           UI.setActive(this.parent);
       }
     } else {
       if (options && options.groupItemId)
         groupItem = GroupItems.groupItem(options.groupItemId);
       if (groupItem) {
         groupItem.add(this, {immediately: true});
       } else {
         // create tab group by double click is handled in UI_init().
         GroupItems.newTab(this, {immediately: true});
       }
     }
     this._reconnected = true;
     this.save();
     this._sendToSubscribers("reconnected");
   },
   // ----------
   // Function: setHidden
   // Hide/unhide this item
   setHidden: function TabItem_setHidden(val) {
     if (val)
       this.addClass("tabHidden");
     else
       this.removeClass("tabHidden");
     this._hidden = val;
   },
   // ----------
   // Function: getHidden
   // Return hide state of item
   getHidden: function TabItem_getHidden() {
     return this._hidden;
   },
   // ----------
   // Function: setBounds
   // Moves this item to the specified location and size.
   //
   // Parameters:
   //   rect - 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 TabItem_setBounds(inRect, immediately, options) {
     Utils.assert(Utils.isRect(inRect), 'TabItem.setBounds: rect is not a real rectangle!');
     if (!options)
       options = {};
     // force the input size to be valid
     let validSize = TabItems.calcValidSize(
       new Point(inRect.width, inRect.height),
       {hideTitle: (this.isStacked || options.hideTitle === true)});
     let rect = new Rect(inRect.left, inRect.top,
       validSize.x, validSize.y);
     var css = {};
     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 - TabItems.tabItemPadding.x;
       css.fontSize = TabItems.getFontSizeFromWidth(rect.width);
       css.fontSize += 'px';
     }
     if (rect.height != this.bounds.height || options.force) {
       css.height = rect.height - TabItems.tabItemPadding.y;
       if (!this.isStacked)
         css.height -= TabItems.fontSizeRange.max;
     }
     if (Utils.isEmptyObject(css))
       return;
     this.bounds.copy(rect);
     // If this is a brand new tab don't animate it in from
     // a random location (i.e., from [0,0]). Instead, just
     // have it appear where it should be.
     if (immediately || (!this._hasBeenDrawn)) {
       this.$container.css(css);
     } else {
       TabItems.pausePainting();
       this.$container.animate(css, {
           duration: 200,
         easing: "tabviewBounce",
         complete: function() {
           TabItems.resumePainting();
         }
       });
     }
     if (css.fontSize && !(this.parent && this.parent.isStacked())) {
       if (css.fontSize < TabItems.fontSizeRange.min)
         immediately ? this.$tabTitle.hide() : this.$tabTitle.fadeOut();
       else
         immediately ? this.$tabTitle.show() : this.$tabTitle.fadeIn();
     }
     if (css.width) {
       TabItems.update(this.tab);
       let widthRange, proportion;
       if (this.parent && this.parent.isStacked()) {
         if (UI.rtl) {
           this.$fav.css({top:0, right:0});
         } else {
           this.$fav.css({top:0, left:0});
         }
         widthRange = new Range(70, 90);
         proportion = widthRange.proportion(css.width); // between 0 and 1
       } else {
         if (UI.rtl) {
           this.$fav.css({top:4, right:2});
         } else {
           this.$fav.css({top:4, left:4});
         }
         widthRange = new Range(40, 45);
         proportion = widthRange.proportion(css.width); // between 0 and 1
       }
       if (proportion <= .1)
         this.$close.hide();
       else
         this.$close.show().css({opacity:proportion});
       var pad = 1 + 5 * proportion;
       var alphaRange = new Range(0.1,0.2);
       this.$fav.css({
        "-moz-padding-start": pad + "px",
        "-moz-padding-end": pad + 2 + "px",
        "padding-top": pad + "px",
        "padding-bottom": pad + "px",
        "border-color": "rgba(0,0,0,"+ alphaRange.scale(proportion) +")",
       });
     }
     this._hasBeenDrawn = true;
     UI.clearShouldResizeItems();
     rect = this.getBounds(); // ensure that it's a <Rect>
     Utils.assert(Utils.isRect(this.bounds), 'TabItem.setBounds: this.bounds is not a real rectangle!');
     if (!this.parent && Utils.isValidXULTab(this.tab))
       this.setTrenches(rect);
     this.save();
   },
   // ----------
   // Function: setZ
   // Sets the z-index for this item.
   setZ: function TabItem_setZ(value) {
     this.zIndex = value;
     this.$container.css({zIndex: value});
   },
   // ----------
   // Function: close
   // Closes this item (actually closes the tab associated with it, which automatically
   // closes the item.
   // Parameters:
   //   groupClose - true if this method is called by group close action.
   // Returns true if this tab is removed.
   close: function TabItem_close(groupClose) {
     // When the last tab is closed, put a new tab into closing tab's group. If
     // closing tab doesn't belong to a group and no empty group, create a new
     // one for the new tab.
     if (!groupClose && gBrowser.tabs.length == 1) {
       let group = this.tab._tabViewTabItem.parent;
       group.newTab(null, { closedLastTab: true });
     }
     // when "TabClose" event is fired, the browser tab is about to close and our
     // item "close" is fired before the browser tab actually get closed.
     // Therefore, we need "tabRemoved" event below.
     gBrowser.removeTab(this.tab);
     let tabClosed = !this.tab;
     if (tabClosed)
       this._sendToSubscribers("tabRemoved");
     // No need to explicitly delete the tab data, becasue sessionstore data
     // associated with the tab will automatically go away
     return tabClosed;
   },
   // ----------
   // Function: addClass
   // Adds the specified CSS class to this item's container DOM element.
   addClass: function TabItem_addClass(className) {
     this.$container.addClass(className);
   },
   // ----------
   // Function: removeClass
   // Removes the specified CSS class from this item's container DOM element.
   removeClass: function TabItem_removeClass(className) {
     this.$container.removeClass(className);
   },
   // ----------
   // Function: makeActive
   // Updates this item to visually indicate that it's active.
   makeActive: function TabItem_makeActive() {
     this.$container.addClass("focus");
     if (this.parent)
       this.parent.setActiveTab(this);
   },
   // ----------
   // Function: makeDeactive
   // Updates this item to visually indicate that it's not active.
   makeDeactive: function TabItem_makeDeactive() {
     this.$container.removeClass("focus");
   },
   // ----------
   // Function: zoomIn
   // Allows you to select the tab and zoom in on it, thereby bringing you
   // to the tab in Firefox to interact with.
   // Parameters:
   //   isNewBlankTab - boolean indicates whether it is a newly opened blank tab.
   zoomIn: function TabItem_zoomIn(isNewBlankTab) {
     // don't allow zoom in if its group is hidden
     if (this.parent && this.parent.hidden)
       return;
     let self = this;
     let $tabEl = this.$container;
     let $canvas = this.$canvas;
     Search.hide();
     UI.setActive(this);
     TabItems._update(this.tab, {force: true});
     // Zoom in!
     let tab = this.tab;
     function onZoomDone() {
       $canvas.css({ 'transform': null });
       $tabEl.removeClass("front");
       UI.goToTab(tab);
       // tab might not be selected because hideTabView() is invoked after
       // UI.goToTab() so we need to setup everything for the gBrowser.selectedTab
       if (!tab.selected) {
         UI.onTabSelect(gBrowser.selectedTab);
       } else {
         if (isNewBlankTab)
           gWindow.gURLBar.focus();
       }
       if (self.parent && self.parent.expanded)
         self.parent.collapse();
       self._sendToSubscribers("zoomedIn");
     }
     let animateZoom = gPrefBranch.getBoolPref("animate_zoom");
     if (animateZoom) {
       let transform = this.getZoomTransform();
       TabItems.pausePainting();
       if (this.parent && this.parent.expanded)
         $tabEl.removeClass("stack-trayed");
       $tabEl.addClass("front");
       $canvas
         .css({ 'transform-origin': transform.transformOrigin })
         .animate({ 'transform': transform.transform }, {
           duration: 230,
           easing: 'fast',
           complete: function() {
             onZoomDone();
             setTimeout(function() {
               TabItems.resumePainting();
             }, 0);
           }
         });
     } else {
       setTimeout(onZoomDone, 0);
     }
   },
   // ----------
   // Function: zoomOut
   // Handles the zoom down animation after returning to TabView.
   // It is expected that this routine will be called from the chrome thread
   //
   // Parameters:
   //   complete - a function to call after the zoom down animation
   zoomOut: function TabItem_zoomOut(complete) {
     let $tab = this.$container, $canvas = this.$canvas;
     var self = this;
     let onZoomDone = function onZoomDone() {
       $tab.removeClass("front");
       $canvas.css("transform", null);
       if (typeof complete == "function")
         complete();
     };
     UI.setActive(this);
     TabItems._update(this.tab, {force: true});
     $tab.addClass("front");
     let animateZoom = gPrefBranch.getBoolPref("animate_zoom");
     if (animateZoom) {
       // The scaleCheat of 2 here is a clever way to speed up the zoom-out
       // code. See getZoomTransform() below.
       let transform = this.getZoomTransform(2);
       TabItems.pausePainting();
       $canvas.css({
         'transform': transform.transform,
         'transform-origin': transform.transformOrigin
       });
       $canvas.animate({ "transform": "scale(1.0)" }, {
         duration: 300,
         easing: 'cubic-bezier', // note that this is legal easing, even without parameters
         complete: function() {
           TabItems.resumePainting();
           onZoomDone();
         }
       });
     } else {
       onZoomDone();
     }
   },
   // ----------
   // Function: getZoomTransform
   // Returns the transform function which represents the maximum bounds of the
   // tab thumbnail in the zoom animation.
   getZoomTransform: function TabItem_getZoomTransform(scaleCheat) {
     // Taking the bounds of the container (as opposed to the canvas) makes us
     // immune to any transformations applied to the canvas.
     let { left, top, width, height, right, bottom } = this.$container.bounds();
     let { innerWidth: windowWidth, innerHeight: windowHeight } = window;
     // The scaleCheat is a clever way to speed up the zoom-in code.
     // Because image scaling is slowest on big images, we cheat and stop
     // the image at scaled-down size and placed accordingly. Because the
     // animation is fast, you can't see the difference but it feels a lot
     // zippier. The only trick is choosing the right animation function so
     // that you don't see a change in percieved animation speed from frame #1
     // (the tab) to frame #2 (the half-size image) to frame #3 (the first frame
     // of real animation). Choosing an animation that starts fast is key.
     if (!scaleCheat)
       scaleCheat = 1.7;
     let zoomWidth = width + (window.innerWidth - width) / scaleCheat;
     let zoomScaleFactor = zoomWidth / width;
     let zoomHeight = height * zoomScaleFactor;
     let zoomTop = top * (1 - 1/scaleCheat);
     let zoomLeft = left * (1 - 1/scaleCheat);
     let xOrigin = (left - zoomLeft) / ((left - zoomLeft) + (zoomLeft + zoomWidth - right)) * 100;
     let yOrigin = (top - zoomTop) / ((top - zoomTop) + (zoomTop + zoomHeight - bottom)) * 100;
     return {
       transformOrigin: xOrigin + "% " + yOrigin + "%",
       transform: "scale(" + zoomScaleFactor + ")"
     };
   },
   // ----------
   // Function: updateCanvas
   // Updates the tabitem's canvas.
   updateCanvas: function TabItem_updateCanvas() {
     // ___ thumbnail
     let $canvas = this.$canvas;
     if (!this.canvasSizeForced) {
       let w = $canvas.width();
       let h = $canvas.height();
       if (w != $canvas[0].width || h != $canvas[0].height) {
         $canvas[0].width = w;
         $canvas[0].height = h;
       }
     }
     TabItems._lastUpdateTime = Date.now();
     this._lastTabUpdateTime = TabItems._lastUpdateTime;
     if (this.tabCanvas)
       this.tabCanvas.paint();
     // ___ cache
     if (this.isShowingCachedData())
       this.hideCachedData();
   }
 });
 // ##########
 // Class: TabItems
 // Singleton for managing <TabItem>s
 let TabItems = {
   minTabWidth: 40,
   tabWidth: 160,
   tabHeight: 120,
   tabAspect: 0, // set in init
   invTabAspect: 0, // set in init
   fontSize: 9,
   fontSizeRange: new Range(8,15),
   _fragment: null,
   items: [],
   paintingPaused: 0,
   _tabsWaitingForUpdate: null,
   _heartbeat: null, // see explanation at startHeartbeat() below
   _heartbeatTiming: 200, // milliseconds between calls
   _maxTimeForUpdating: 200, // milliseconds that consecutive updates can take
   _lastUpdateTime: Date.now(),
   _eventListeners: [],
   _pauseUpdateForTest: false,
   _reconnectingPaused: false,
   tabItemPadding: {},
   _mozAfterPaintHandler: null,
   // ----------
   // Function: toString
   // Prints [TabItems count=count] for debug use
   toString: function TabItems_toString() {
     return "[TabItems count=" + this.items.length + "]";
   },
   // ----------
   // Function: init
   // Set up the necessary tracking to maintain the <TabItems>s.
   init: function TabItems_init() {
     Utils.assert(window.AllTabs, "AllTabs must be initialized first");
     let self = this;
     // Set up tab priority queue
     this._tabsWaitingForUpdate = new TabPriorityQueue();
     this.minTabHeight = this.minTabWidth * this.tabHeight / this.tabWidth;
     this.tabAspect = this.tabHeight / this.tabWidth;
     this.invTabAspect = 1 / this.tabAspect;
     let $canvas = iQ("<canvas>")
       .attr('moz-opaque', '');
     $canvas.appendTo(iQ("body"));
     $canvas.hide();
     let mm = gWindow.messageManager;
     this._mozAfterPaintHandler = this.onMozAfterPaint.bind(this);
     mm.addMessageListener("Panorama:MozAfterPaint", this._mozAfterPaintHandler);
     // When a tab is opened, create the TabItem
     this._eventListeners.open = function (event) {
       let tab = event.target;
       if (!tab.pinned)
         self.link(tab);
     }
     // When a tab's content is loaded, show the canvas and hide the cached data
     // if necessary.
     this._eventListeners.attrModified = function (event) {
       let tab = event.target;
       if (!tab.pinned)
         self.update(tab);
     }
     // When a tab is closed, unlink.
     this._eventListeners.close = function (event) {
       let tab = event.target;
       // XXX bug #635975 - don't unlink the tab if the dom window is closing.
       if (!tab.pinned && !UI.isDOMWindowClosing)
         self.unlink(tab);
     }
     for (let name in this._eventListeners) {
       AllTabs.register(name, this._eventListeners[name]);
     }
     let activeGroupItem = GroupItems.getActiveGroupItem();
     let activeGroupItemId = activeGroupItem ? activeGroupItem.id : null;
     // For each tab, create the link.
     AllTabs.tabs.forEach(function (tab) {
       if (tab.pinned)
         return;
       let options = {immediately: true};
       // if tab is visible in the tabstrip and doesn't have any data stored in
       // the session store (see TabItem__reconnect), it implies that it is a
       // new tab which is created before Panorama is initialized. Therefore,
       // passing the active group id to the link() method for setting it up.
       if (!tab.hidden && activeGroupItemId)
          options.groupItemId = activeGroupItemId;
       self.link(tab, options);
       self.update(tab);
     });
   },
   // ----------
   // Function: uninit
   uninit: function TabItems_uninit() {
     let mm = gWindow.messageManager;
     mm.removeMessageListener("Panorama:MozAfterPaint", this._mozAfterPaintHandler);
     for (let name in this._eventListeners) {
       AllTabs.unregister(name, this._eventListeners[name]);
     }
     this.items.forEach(function(tabItem) {
       delete tabItem.tab._tabViewTabItem;
       for (let x in tabItem) {
         if (typeof tabItem[x] == "object")
           tabItem[x] = null;
       }
     });
     this.items = null;
     this._eventListeners = null;
     this._lastUpdateTime = null;
     this._tabsWaitingForUpdate.clear();
   },
   // ----------
   // Function: fragment
   // Return a DocumentFragment which has a single <div> child. This child node
   // will act as a template for all TabItem containers.
   // The first call of this function caches the DocumentFragment in _fragment.
   fragment: function TabItems_fragment() {
     if (this._fragment)
       return this._fragment;
     let div = document.createElement("div");
     div.classList.add("tab");
     div.innerHTML = "<div class='thumb'>" +
             "<img class='cached-thumb' style='display:none'/><canvas moz-opaque/></div>" +
             "<div class='favicon'><img/></div>" +
             "<span class='tab-title'>&nbsp;</span>" +
             "<div class='close'></div>";
     this._fragment = document.createDocumentFragment();
     this._fragment.appendChild(div);
     return this._fragment;
   },
   // Function: _isComplete
   // Checks whether the xul:tab has fully loaded and calls a callback with a
   // boolean indicates whether the tab is loaded or not.
   _isComplete: function TabItems__isComplete(tab, callback) {
     Utils.assertThrow(tab, "tab");
     // A pending tab can't be complete, yet.
     if (tab.hasAttribute("pending")) {
       setTimeout(() => callback(false));
       return;
     }
     let mm = tab.linkedBrowser.messageManager;
     let message = "Panorama:isDocumentLoaded";
     mm.addMessageListener(message, function onMessage(cx) {
       mm.removeMessageListener(cx.name, onMessage);
       callback(cx.json.isLoaded);
     });
     mm.sendAsyncMessage(message);
   },
   // ----------
   // Function: onMozAfterPaint
   // Called when a web page is painted.
   onMozAfterPaint: function TabItems_onMozAfterPaint(cx) {
     let index = gBrowser.browsers.indexOf(cx.target);
     if (index == -1)
       return;
     let tab = gBrowser.tabs[index];
     if (!tab.pinned)
       this.update(tab);
   },
   // ----------
   // Function: update
   // Takes in a xul:tab.
   update: function TabItems_update(tab) {
     try {
       Utils.assertThrow(tab, "tab");
       Utils.assertThrow(!tab.pinned, "shouldn't be an app tab");
       Utils.assertThrow(tab._tabViewTabItem, "should already be linked");
       let shouldDefer = (
         this.isPaintingPaused() ||
         this._tabsWaitingForUpdate.hasItems() ||
         Date.now() - this._lastUpdateTime < this._heartbeatTiming
       );
       if (shouldDefer) {
         this._tabsWaitingForUpdate.push(tab);
         this.startHeartbeat();
       } else
         this._update(tab);
     } catch(e) {
       Utils.log(e);
     }
   },
   // ----------
   // Function: _update
   // Takes in a xul:tab.
   //
   // Parameters:
   //   tab - a xul tab to update
   //   options - an object with additional parameters, see below
   //
   // Possible options:
   //   force - true to always update the tab item even if it's incomplete
   _update: function TabItems__update(tab, options) {
     try {
       if (this._pauseUpdateForTest)
         return;
       Utils.assertThrow(tab, "tab");
       // ___ get the TabItem
       Utils.assertThrow(tab._tabViewTabItem, "must already be linked");
       let tabItem = tab._tabViewTabItem;
       // Even if the page hasn't loaded, display the favicon and title
       // ___ icon
       FavIcons.getFavIconUrlForTab(tab, function TabItems__update_getFavIconUrlCallback(iconUrl) {
         let favImage = tabItem.$favImage[0];
         let fav = tabItem.$fav;
         if (iconUrl) {
           if (favImage.src != iconUrl)
             favImage.src = iconUrl;
           fav.show();
         } else {
           if (favImage.hasAttribute("src"))
             favImage.removeAttribute("src");
           fav.hide();
         }
         tabItem._sendToSubscribers("iconUpdated");
       });
       // ___ label
       let label = tab.label;
       let $name = tabItem.$tabTitle;
       if ($name.text() != label)
         $name.text(label);
       // ___ remove from waiting list now that we have no other
       // early returns
       this._tabsWaitingForUpdate.remove(tab);
       // ___ URL
       let tabUrl = tab.linkedBrowser.currentURI.spec;
       let tooltip = (label == tabUrl ? label : label + "\n" + tabUrl);
       tabItem.$container.attr("title", tooltip);
       // ___ Make sure the tab is complete and ready for updating.
       if (options && options.force) {
         tabItem.updateCanvas();
         tabItem._sendToSubscribers("updated");
       } else {
         this._isComplete(tab, function TabItems__update_isComplete(isComplete) {
           if (!Utils.isValidXULTab(tab) || tab.pinned)
             return;
           if (isComplete) {
             tabItem.updateCanvas();
             tabItem._sendToSubscribers("updated");
           } else {
             this._tabsWaitingForUpdate.push(tab);
           }
         }.bind(this));
       }
     } catch(e) {
       Utils.log(e);
     }
   },
   // ----------
   // Function: link
   // Takes in a xul:tab, creates a TabItem for it and adds it to the scene.
   link: function TabItems_link(tab, options) {
     try {
       Utils.assertThrow(tab, "tab");
       Utils.assertThrow(!tab.pinned, "shouldn't be an app tab");
       Utils.assertThrow(!tab._tabViewTabItem, "shouldn't already be linked");
       new TabItem(tab, options); // sets tab._tabViewTabItem to itself
     } catch(e) {
       Utils.log(e);
     }
   },
   // ----------
   // Function: unlink
   // Takes in a xul:tab and destroys the TabItem associated with it.
   unlink: function TabItems_unlink(tab) {
     try {
       Utils.assertThrow(tab, "tab");
       Utils.assertThrow(tab._tabViewTabItem, "should already be linked");
       // note that it's ok to unlink an app tab; see .handleTabUnpin
       this.unregister(tab._tabViewTabItem);
       tab._tabViewTabItem._sendToSubscribers("close");
       tab._tabViewTabItem.$container.remove();
       tab._tabViewTabItem.removeTrenches();
       Items.unsquish(null, tab._tabViewTabItem);
       tab._tabViewTabItem.tab = null;
       tab._tabViewTabItem.tabCanvas.tab = null;
       tab._tabViewTabItem.tabCanvas = null;
       tab._tabViewTabItem = null;
       Storage.saveTab(tab, null);
       this._tabsWaitingForUpdate.remove(tab);
     } catch(e) {
       Utils.log(e);
     }
   },
   // ----------
   // when a tab becomes pinned, destroy its TabItem
   handleTabPin: function TabItems_handleTabPin(xulTab) {
     this.unlink(xulTab);
   },
   // ----------
   // when a tab becomes unpinned, create a TabItem for it
   handleTabUnpin: function TabItems_handleTabUnpin(xulTab) {
     this.link(xulTab);
     this.update(xulTab);
   },
   // ----------
   // Function: startHeartbeat
   // Start a new heartbeat if there isn't one already started.
   // The heartbeat is a chain of setTimeout calls that allows us to spread
   // out update calls over a period of time.
   // _heartbeat is used to make sure that we don't add multiple
   // setTimeout chains.
   startHeartbeat: function TabItems_startHeartbeat() {
     if (!this._heartbeat) {
       let self = this;
       this._heartbeat = setTimeout(function() {
         self._checkHeartbeat();
       }, this._heartbeatTiming);
     }
   },
   // ----------
   // Function: _checkHeartbeat
   // This periodically checks for tabs waiting to be updated, and calls
   // _update on them.
   // Should only be called by startHeartbeat and resumePainting.
   _checkHeartbeat: function TabItems__checkHeartbeat() {
     this._heartbeat = null;
     if (this.isPaintingPaused())
       return;
     // restart the heartbeat to update all waiting tabs once the UI becomes idle
     if (!UI.isIdle()) {
       this.startHeartbeat();
       return;
     }
     let accumTime = 0;
     let items = this._tabsWaitingForUpdate.getItems();
     // Do as many updates as we can fit into a "perceived" amount
     // of time, which is tunable.
     while (accumTime < this._maxTimeForUpdating && items.length) {
       let updateBegin = Date.now();
       this._update(items.pop());
       let updateEnd = Date.now();
       // Maintain a simple average of time for each tabitem update
       // We can use this as a base by which to delay things like
       // tab zooming, so there aren't any hitches.
       let deltaTime = updateEnd - updateBegin;
       accumTime += deltaTime;
     }
     if (this._tabsWaitingForUpdate.hasItems())
       this.startHeartbeat();
   },
   // ----------
   // Function: pausePainting
   // Tells TabItems to stop updating thumbnails (so you can do
   // animations without thumbnail paints causing stutters).
   // pausePainting can be called multiple times, but every call to
   // pausePainting needs to be mirrored with a call to <resumePainting>.
   pausePainting: function TabItems_pausePainting() {
     this.paintingPaused++;
     if (this._heartbeat) {
       clearTimeout(this._heartbeat);
       this._heartbeat = null;
     }
   },
   // ----------
   // Function: resumePainting
   // Undoes a call to <pausePainting>. For instance, if you called
   // pausePainting three times in a row, you'll need to call resumePainting
   // three times before TabItems will start updating thumbnails again.
   resumePainting: function TabItems_resumePainting() {
     this.paintingPaused--;
     Utils.assert(this.paintingPaused > -1, "paintingPaused should not go below zero");
     if (!this.isPaintingPaused())
       this.startHeartbeat();
   },
   // ----------
   // Function: isPaintingPaused
   // Returns a boolean indicating whether painting
   // is paused or not.
   isPaintingPaused: function TabItems_isPaintingPaused() {
     return this.paintingPaused > 0;
   },
   // ----------
   // Function: pauseReconnecting
   // Don't reconnect any new tabs until resume is called.
   pauseReconnecting: function TabItems_pauseReconnecting() {
     Utils.assertThrow(!this._reconnectingPaused, "shouldn't already be paused");
     this._reconnectingPaused = true;
   },
   // ----------
   // Function: resumeReconnecting
   // Reconnect all of the tabs that were created since we paused.
   resumeReconnecting: function TabItems_resumeReconnecting() {
     Utils.assertThrow(this._reconnectingPaused, "should already be paused");
     this._reconnectingPaused = false;
     this.items.forEach(function(item) {
       if (!item._reconnected)
         item._reconnect();
     });
   },
   // ----------
   // Function: reconnectingPaused
   // Returns true if reconnecting is paused.
   reconnectingPaused: function TabItems_reconnectingPaused() {
     return this._reconnectingPaused;
   },
   // ----------
   // Function: register
   // Adds the given <TabItem> to the master list.
   register: function TabItems_register(item) {
     Utils.assert(item && item.isAnItem, 'item must be a TabItem');
     Utils.assert(this.items.indexOf(item) == -1, 'only register once per item');
     this.items.push(item);
   },
   // ----------
   // Function: unregister
   // Removes the given <TabItem> from the master list.
   unregister: function TabItems_unregister(item) {
     var index = this.items.indexOf(item);
     if (index != -1)
       this.items.splice(index, 1);
   },
   // ----------
   // Function: getItems
   // Returns a copy of the master array of <TabItem>s.
   getItems: function TabItems_getItems() {
     return Utils.copy(this.items);
   },
   // ----------
   // Function: saveAll
   // Saves all open <TabItem>s.
   saveAll: function TabItems_saveAll() {
     let tabItems = this.getItems();
     tabItems.forEach(function TabItems_saveAll_forEach(tabItem) {
       tabItem.save();
     });
   },
   // ----------
   // Function: storageSanity
   // Checks the specified data (as returned by TabItem.getStorageData or loaded from storage)
   // and returns true if it looks valid.
   // TODO: this is a stub, please implement
   storageSanity: function TabItems_storageSanity(data) {
     return true;
   },
   // ----------
   // Function: getFontSizeFromWidth
   // Private method that returns the fontsize to use given the tab's width
   getFontSizeFromWidth: function TabItem_getFontSizeFromWidth(width) {
     let widthRange = new Range(0, TabItems.tabWidth);
     let proportion = widthRange.proportion(width - TabItems.tabItemPadding.x, true);
     // proportion is in [0,1]
     return TabItems.fontSizeRange.scale(proportion);
   },
   // ----------
   // Function: _getWidthForHeight
   // Private method that returns the tabitem width given a height.
   _getWidthForHeight: function TabItems__getWidthForHeight(height) {
     return height * TabItems.invTabAspect;
   },
   // ----------
   // Function: _getHeightForWidth
   // Private method that returns the tabitem height given a width.
   _getHeightForWidth: function TabItems__getHeightForWidth(width) {
     return width * TabItems.tabAspect;
   },
   // ----------
   // Function: calcValidSize
   // Pass in a desired size, and receive a size based on proper title
   // size and aspect ratio.
   calcValidSize: function TabItems_calcValidSize(size, options) {
     Utils.assert(Utils.isPoint(size), 'input is a Point');
     let width = Math.max(TabItems.minTabWidth, size.x);
     let showTitle = !options || !options.hideTitle;
     let titleSize = showTitle ? TabItems.fontSizeRange.max : 0;
     let height = Math.max(TabItems.minTabHeight, size.y - titleSize);
     let retSize = new Point(width, height);
     if (size.x > -1)
       retSize.y = this._getHeightForWidth(width);
     if (size.y > -1)
       retSize.x = this._getWidthForHeight(height);
     if (size.x > -1 && size.y > -1) {
       if (retSize.x < size.x)
         retSize.y = this._getHeightForWidth(retSize.x);
       else
         retSize.x = this._getWidthForHeight(retSize.y);
     }
     if (showTitle)
       retSize.y += titleSize;
     return retSize;
   }
 };
 // ##########
 // Class: TabPriorityQueue
 // Container that returns tab items in a priority order
 // Current implementation assigns tab to either a high priority
 // or low priority queue, and toggles which queue items are popped
 // from. This guarantees that high priority items which are constantly
 // being added will not eclipse changes for lower priority items.
 function TabPriorityQueue() {
 };
 TabPriorityQueue.prototype = {
   _low: [], // low priority queue
   _high: [], // high priority queue
   // ----------
   // Function: toString
   // Prints [TabPriorityQueue count=count] for debug use
   toString: function TabPriorityQueue_toString() {
     return "[TabPriorityQueue count=" + (this._low.length + this._high.length) + "]";
   },
   // ----------
   // Function: clear
   // Empty the update queue
   clear: function TabPriorityQueue_clear() {
     this._low = [];
     this._high = [];
   },
   // ----------
   // Function: hasItems
   // Return whether pending items exist
   hasItems: function TabPriorityQueue_hasItems() {
     return (this._low.length > 0) || (this._high.length > 0);
   },
   // ----------
   // Function: getItems
   // Returns all queued items, ordered from low to high priority
   getItems: function TabPriorityQueue_getItems() {
     return this._low.concat(this._high);
   },
   // ----------
   // Function: push
   // Add an item to be prioritized
   push: function TabPriorityQueue_push(tab) {
     // Push onto correct priority queue.
     // It's only low priority if it's in a stack, and isn't the top,
     // and the stack isn't expanded.
     // If it already exists in the destination queue,
     // leave it. If it exists in a different queue, remove it first and push
     // onto new queue.
     let item = tab._tabViewTabItem;
     if (item.parent && (item.parent.isStacked() &&
       !item.parent.isTopOfStack(item) &&
       !item.parent.expanded)) {
       let idx = this._high.indexOf(tab);
       if (idx != -1) {
         this._high.splice(idx, 1);
         this._low.unshift(tab);
       } else if (this._low.indexOf(tab) == -1)
         this._low.unshift(tab);
     } else {
       let idx = this._low.indexOf(tab);
       if (idx != -1) {
         this._low.splice(idx, 1);
         this._high.unshift(tab);
       } else if (this._high.indexOf(tab) == -1)
         this._high.unshift(tab);
     }
   },
   // ----------
   // Function: pop
   // Remove and return the next item in priority order
   pop: function TabPriorityQueue_pop() {
     let ret = null;
     if (this._high.length)
       ret = this._high.pop();
     else if (this._low.length)
       ret = this._low.pop();
     return ret;
   },
   // ----------
   // Function: peek
   // Return the next item in priority order, without removing it
   peek: function TabPriorityQueue_peek() {
     let ret = null;
     if (this._high.length)
       ret = this._high[this._high.length-1];
     else if (this._low.length)
       ret = this._low[this._low.length-1];
     return ret;
   },
   // ----------
   // Function: remove
   // Remove the passed item
   remove: function TabPriorityQueue_remove(tab) {
     let index = this._high.indexOf(tab);
     if (index != -1)
       this._high.splice(index, 1);
     else {
       index = this._low.indexOf(tab);
       if (index != -1)
         this._low.splice(index, 1);
     }
   }
 };
 // ##########
 // Class: TabCanvas
 // Takes care of the actual canvas for the tab thumbnail
 // Does not need to be accessed from outside of tabitems.js
 function TabCanvas(tab, canvas) {
   this.tab = tab;
   this.canvas = canvas;
 };
 TabCanvas.prototype = Utils.extend(new Subscribable(), {
   // ----------
   // Function: toString
   // Prints [TabCanvas (tab)] for debug use
   toString: function TabCanvas_toString() {
     return "[TabCanvas (" + this.tab + ")]";
   },
   // ----------
   // Function: paint
   paint: function TabCanvas_paint(evt) {
     var w = this.canvas.width;
     var h = this.canvas.height;
     if (!w || !h)
       return;
     if (!this.tab.linkedBrowser.contentWindow) {
       Utils.log('no tab.linkedBrowser.contentWindow in TabCanvas.paint()');
       return;
     }
     let win = this.tab.linkedBrowser.contentWindow;
     gPageThumbnails.captureToCanvas(win, this.canvas);
     this._sendToSubscribers("painted");
   },
   // ----------
   // Function: toImageData
   toImageData: function TabCanvas_toImageData() {
     return this.canvas.toDataURL("image/png");
   }
 });