+ Trying -moz-crisp-edges… doesn't seem to improve speed much on 3.6, and looks worse

+ Created Utils.copy to make duplicating objects cleaner
+ Fixed a number of issues with pulling tabs out of a tray. Temporarily disabled the delay on drag as well.
+ Improved the threshold for switching from grid to stack; only happens when the grid fills up.
+ No longer announcing "bad storage data" when there is in fact no storage data (fresh start)
+ A couple more asserts

browser/base/content/tabcandy/app/groups.js

@@ -41,7 +41,7 @@ window.Group = function(listOfEls, options) {
   this._isStacked = false;
   this._stackAngles = [0];
   this.expanded = null;
-  this.locked = (options.locked ? $.extend({}, options.locked) : {});
+  this.locked = (options.locked ? Utils.copy(options.locked) : {});
   
   if(isPoint(options.userSize))  
     this.userSize = new Point(options.userSize);
@@ -232,7 +232,7 @@ window.Group.prototype = $.extend(new Item(), new Subscribable(), {
     var data = {
       bounds: this.getBounds(), 
       userSize: null,
-      locked: $.extend({}, this.locked), 
+      locked: Utils.copy(this.locked), 
       title: this.getTitle(),
       id: this.id
     };
@@ -543,8 +543,10 @@ window.Group.prototype = $.extend(new Item(), new Subscribable(), {
       this._children.splice(index, 1); 
     
     item.parent = null;
-    $el.removeClass("tabInGroup");
-    
+    item.removeClass("tabInGroup");
+    item.removeClass("stacked");
+    item.removeClass("stack-trayed");
+    item.setRotation(0);
     item.setSize(item.defaultSize.x, item.defaultSize.y);
 
     $el.droppable("enable");    
@@ -571,30 +573,41 @@ window.Group.prototype = $.extend(new Item(), new Subscribable(), {
     
   // ----------  
   shouldStack: function(count) {
+    if(count <= 1)
+      return false;
+      
     var bb = this.getContentBounds();
-    var result = !(count == 1 || (bb.width * bb.height) / count > 7000);          
-    return result;
+    var options = {
+      pretend: true,
+      count: count
+    };
+    
+    var rects = Items.arrange(null, bb, options);
+    return (rects[0].width < TabItems.minTabWidth * 1.5);
   },
 
   // ----------  
   arrange: function(options) {
-    if(this.expanded)
-      return;
-      
-    var count = this._children.length;
-    if(!count)
-      return;
-
-    var bb = this.getContentBounds();
-    if(!this.shouldStack(count)) {
-      this._children.forEach(function(child){
-          child.removeClass("stacked")
-      });
-
-      Items.arrange(this._children, bb, options);
-      this._isStacked = false;
-    } else
-      this._stackArrange(bb, options);
+    if(this.expanded) {
+      var box = new Rect(this.expanded.bounds);
+      box.inset(8, 8);
+      Items.arrange(this._children, box, $.extend({}, options, {padding: 8, z: 99999}));
+    } else {
+      var count = this._children.length;
+      if(!count)
+        return;
+  
+      var bb = this.getContentBounds();
+      if(!this.shouldStack(count)) {
+        this._children.forEach(function(child){
+            child.removeClass("stacked")
+        });
+  
+        Items.arrange(this._children, bb, options);
+        this._isStacked = false;
+      } else
+        this._stackArrange(bb, options);
+    }
   },
   
   // ----------
@@ -716,10 +729,6 @@ window.Group.prototype = $.extend(new Item(), new Subscribable(), {
       child.addClass("stack-trayed");
     });
 
-    var box = new Rect(pos.left, pos.top, overlayWidth, overlayHeight);
-    box.inset(8, 8);
-    Items.arrange(this._children, box, {padding: 8, z: 99999});
-    
     var $shield = $('<div />')
       .css({
         left: 0,
@@ -739,8 +748,11 @@ window.Group.prototype = $.extend(new Item(), new Subscribable(), {
       
     this.expanded = {
       $tray: $tray,
-      $shield: $shield
+      $shield: $shield,
+      bounds: new Rect(pos.left, pos.top, overlayWidth, overlayHeight)
     };
+    
+    this.arrange();
 
     return {};
   },
@@ -972,10 +984,9 @@ DragInfo.prototype = {
     if(this.parent && this.parent.expanded) {
       var now = Utils.getMilliseconds();
       var distance = this.startPosition.distance(new Point(event.clientX, event.clientY));
-      if(now - this.startTime > 500 && distance > 100) {
-        this.item.locked.bounds = true;
+      if(true) { //now - this.startTime > 500 && distance > 100) {
+        this.parent.remove(this.item);
         this.parent.collapse();
-        this.item.locked.bounds = false;
       }
     }
   },
@@ -993,6 +1004,9 @@ DragInfo.prototype = {
       this.parent.remove(this.parent._children[0]);
     }*/
      
+    if(this.parent && this.parent.expanded)
+      this.parent.arrange();
+      
     if(this.item && !this.$el.hasClass('willGroup') && !this.item.parent) {
       this.item.setZ(drag.zIndex);
       drag.zIndex++;

browser/base/content/tabcandy/app/storage.js

@@ -1,3 +1,5 @@
+// Title: storage.js (revision-a)
+
 // ##########
 Storage = {
   // ----------

browser/base/content/tabcandy/app/tabitems.js

@@ -1,3 +1,5 @@
+// Title: tabitems.js (revision-a)
+
 // ##########
 window.TabItem = function(container, tab) {
   this.defaultSize = new Point(TabItems.tabWidth, TabItems.tabHeight);
@@ -63,6 +65,11 @@ window.TabItem.prototype = $.extend(new Item(), {
   
   // ----------  
   setBounds: function(rect, immediately) {
+    if(!isRect(rect)) {
+      Utils.trace('TabItem.setBounds: rect is not a real rectangle!', rect);
+      return;
+    }
+
     var $container = $(this.container);
     var $title = $('.tab-title', $container);
     var $thumb = $('.thumb', $container);
@@ -97,6 +104,7 @@ window.TabItem.prototype = $.extend(new Item(), {
       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.
@@ -131,6 +139,9 @@ window.TabItem.prototype = $.extend(new Item(), {
 
     this._updateDebugBounds();
     this._hasBeenDrawn = true;
+    
+    if(!isRect(this.bounds))
+      Utils.trace('TabItem.setBounds: this.bounds is not a real rectangle!', this.bounds);
   },
 
   // ----------

browser/base/content/tabcandy/app/ui.js

@@ -1,3 +1,5 @@
+// Title: ui.js (revision-a)
+
 (function(){
 
 // ##########
@@ -516,17 +518,18 @@ UIClass.prototype = {
 
   // ----------
   storageSanity: function(data) {
-    var sane = true;
-    if(data) {
-      sane = sane && typeof(data.dataVersion) == 'number';
-      sane = sane && isRect(data.pageBounds);
+    if($.isEmptyObject(data))
+      return true;
       
-      if(data.tabs)
-        sane = sane && TabItems.storageSanity(data.tabs);
-        
-      if(data.groups)
-        sane = sane && Groups.storageSanity(data.groups);
-    }
+    var sane = true;
+    sane = sane && typeof(data.dataVersion) == 'number';
+    sane = sane && isRect(data.pageBounds);
+    
+    if(data.tabs)
+      sane = sane && TabItems.storageSanity(data.tabs);
+      
+    if(data.groups)
+      sane = sane && Groups.storageSanity(data.groups);
     
     return sane;
   },

browser/base/content/tabcandy/core/tabs.js

@@ -1,3 +1,4 @@
+// Title: tabs.js
 (function(){
 
 

browser/base/content/tabcandy/core/utils.js

@@ -309,6 +309,8 @@ window.Subscribable.prototype = {
 };
 
 // ##########
+// Class: Utils
+// Singelton with common utility functions.
 var Utils = {
   // ___ Windows and Tabs
   get activeWindow(){
@@ -527,8 +529,21 @@ var Utils = {
   },
  
   // ----------
+  // Function: isNumber
+  // Returns true if the argument is a valid number. 
   isNumber: function(n) {
     return (typeof(n) == 'number' && !isNaN(n));
+  },
+  
+  // ----------
+  // Function: copy
+  // Returns a copy of the argument. Note that this is a shallow copy; if the argument
+  // has properties that are themselves objects, those properties will be copied by reference.
+  copy: function(value) {
+    if(value && typeof(value) == 'object') 
+      return $.extend({}, value);
+      
+    return value;
   }
 };
 

browser/themes/pinstripe/browser/tabcandy/tabcandy.css

@@ -1,5 +1,6 @@
 html {
   overflow: hidden;
+  image-rendering: -moz-crisp-edges;
 }
 
 body {