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

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

browser/components/tabview/items.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: items.js
 // ##########
 // Class: Item
 // Superclass for all visible objects (<TabItem>s and <GroupItem>s).
 //
 // If you subclass, in addition to the things Item provides, you need to also provide these methods:
 //   setBounds - function(rect, immediately, options)
 //   setZ - function(value)
 //   close - function()
 //   save - function()
 //
 // Subclasses of Item must also provide the <Subscribable> interface.
 //
 // Make sure to call _init() from your subclass's constructor.
 function Item() {
   // Variable: isAnItem
   // Always true for Items
   this.isAnItem = true;
   // Variable: bounds
   // The position and size of this Item, represented as a <Rect>.
   // This should never be modified without using setBounds()
   this.bounds = null;
   // Variable: zIndex
   // The z-index for this item.
   this.zIndex = 0;
   // Variable: container
   // The outermost DOM element that describes this item on screen.
   this.container = null;
   // Variable: parent
   // The groupItem that this item is a child of
   this.parent = null;
   // Variable: userSize
   // A <Point> that describes the last size specifically chosen by the user.
   // Used by unsquish.
   this.userSize = null;
   // Variable: dragOptions
   // Used by <draggable>
   //
   // Possible properties:
   //   cancelClass - A space-delimited list of classes that should cancel a drag
   //   start - A function to be called when a drag starts
   //   drag - A function to be called each time the mouse moves during drag
   //   stop - A function to be called when the drag is done
   this.dragOptions = null;
   // Variable: dropOptions
   // Used by <draggable> if the item is set to droppable.
   //
   // Possible properties:
   //   accept - A function to determine if a particular item should be accepted for dropping
   //   over - A function to be called when an item is over this item
   //   out - A function to be called when an item leaves this item
   //   drop - A function to be called when an item is dropped in this item
   this.dropOptions = null;
   // Variable: resizeOptions
   // Used by <resizable>
   //
   // Possible properties:
   //   minWidth - Minimum width allowable during resize
   //   minHeight - Minimum height allowable during resize
   //   aspectRatio - true if we should respect aspect ratio; default false
   //   start - A function to be called when resizing starts
   //   resize - A function to be called each time the mouse moves during resize
   //   stop - A function to be called when the resize is done
   this.resizeOptions = null;
   // Variable: isDragging
   // Boolean for whether the item is currently being dragged or not.
   this.isDragging = false;
 };
 Item.prototype = {
   // ----------
   // Function: _init
   // Initializes the object. To be called from the subclass's intialization function.
   //
   // Parameters:
   //   container - the outermost DOM element that describes this item onscreen.
   _init: function Item__init(container) {
     Utils.assert(typeof this.addSubscriber == 'function' &&
         typeof this.removeSubscriber == 'function' &&
         typeof this._sendToSubscribers == 'function',
         'Subclass must implement the Subscribable interface');
     Utils.assert(Utils.isDOMElement(container), 'container must be a DOM element');
     Utils.assert(typeof this.setBounds == 'function', 'Subclass must provide setBounds');
     Utils.assert(typeof this.setZ == 'function', 'Subclass must provide setZ');
     Utils.assert(typeof this.close == 'function', 'Subclass must provide close');
     Utils.assert(typeof this.save == 'function', 'Subclass must provide save');
     Utils.assert(Utils.isRect(this.bounds), 'Subclass must provide bounds');
     this.container = container;
     this.$container = iQ(container);
     iQ(this.container).data('item', this);
     // ___ drag
     this.dragOptions = {
       cancelClass: 'close stackExpander',
       start: function(e, ui) {
         UI.setActive(this);
         if (this.isAGroupItem)
           this._unfreezeItemSize();
         // if we start dragging a tab within a group, start with dropSpace on.
         else if (this.parent != null)
           this.parent._dropSpaceActive = true;
         drag.info = new Drag(this, e);
       },
       drag: function(e) {
         drag.info.drag(e);
       },
       stop: function() {
         drag.info.stop();
         if (!this.isAGroupItem && !this.parent) {
           new GroupItem([drag.info.$el], {focusTitle: true});
           gTabView.firstUseExperienced = true;
         }
         drag.info = null;
       },
       // The minimum the mouse must move after mouseDown in order to move an
       // item
       minDragDistance: 3
     };
     // ___ drop
     this.dropOptions = {
       over: function() {},
       out: function() {
         let groupItem = drag.info.item.parent;
         if (groupItem)
           groupItem.remove(drag.info.$el, {dontClose: true});
         iQ(this.container).removeClass("acceptsDrop");
       },
       drop: function(event) {
         iQ(this.container).removeClass("acceptsDrop");
       },
       // Function: dropAcceptFunction
       // Given a DOM element, returns true if it should accept tabs being dropped on it.
       // Private to this file.
       accept: function dropAcceptFunction(item) {
         return (item && item.isATabItem && (!item.parent || !item.parent.expanded));
       }
     };
     // ___ resize
     var self = this;
     this.resizeOptions = {
       aspectRatio: self.keepProportional,
       minWidth: 90,
       minHeight: 90,
       start: function(e,ui) {
         UI.setActive(this);
         resize.info = new Drag(this, e);
       },
       resize: function(e,ui) {
         resize.info.snap(UI.rtl ? 'topright' : 'topleft', false, self.keepProportional);
       },
       stop: function() {
         self.setUserSize();
         self.pushAway();
         resize.info.stop();
         resize.info = null;
       }
     };
   },
   // ----------
   // Function: getBounds
   // Returns a copy of the Item's bounds as a <Rect>.
   getBounds: function Item_getBounds() {
     Utils.assert(Utils.isRect(this.bounds), 'this.bounds should be a rect');
     return new Rect(this.bounds);
   },
   // ----------
   // Function: overlapsWithOtherItems
   // Returns true if this Item overlaps with any other Item on the screen.
   overlapsWithOtherItems: function Item_overlapsWithOtherItems() {
     var self = this;
     var items = Items.getTopLevelItems();
     var bounds = this.getBounds();
     return items.some(function(item) {
       if (item == self) // can't overlap with yourself.
         return false;
       var myBounds = item.getBounds();
       return myBounds.intersects(bounds);
     } );
   },
   // ----------
   // Function: setPosition
   // Moves the Item to the specified location.
   //
   // Parameters:
   //   left - the new left coordinate relative to the window
   //   top - the new top coordinate relative to the window
   //   immediately - if false or omitted, animates to the new position;
   //   otherwise goes there immediately
   setPosition: function Item_setPosition(left, top, immediately) {
     Utils.assert(Utils.isRect(this.bounds), 'this.bounds');
     this.setBounds(new Rect(left, top, this.bounds.width, this.bounds.height), immediately);
   },
   // ----------
   // Function: setSize
   // Resizes the Item to the specified size.
   //
   // Parameters:
   //   width - the new width in pixels
   //   height - the new height in pixels
   //   immediately - if false or omitted, animates to the new size;
   //   otherwise resizes immediately
   setSize: function Item_setSize(width, height, immediately) {
     Utils.assert(Utils.isRect(this.bounds), 'this.bounds');
     this.setBounds(new Rect(this.bounds.left, this.bounds.top, width, height), immediately);
   },
   // ----------
   // Function: setUserSize
   // Remembers the current size as one the user has chosen.
   setUserSize: function Item_setUserSize() {
     Utils.assert(Utils.isRect(this.bounds), 'this.bounds');
     this.userSize = new Point(this.bounds.width, this.bounds.height);
     this.save();
   },
   // ----------
   // Function: getZ
   // Returns the zIndex of the Item.
   getZ: function Item_getZ() {
     return this.zIndex;
   },
   // ----------
   // Function: setRotation
   // Rotates the object to the given number of degrees.
   setRotation: function Item_setRotation(degrees) {
     var value = degrees ? "rotate(%deg)".replace(/%/, degrees) : null;
     iQ(this.container).css({"transform": value});
   },
   // ----------
   // Function: setParent
   // Sets the receiver's parent to the given <Item>.
   setParent: function Item_setParent(parent) {
     this.parent = parent;
     this.removeTrenches();
     this.save();
   },
   // ----------
   // Function: pushAway
   // Pushes all other items away so none overlap this Item.
   //
   // Parameters:
   //  immediately - boolean for doing the pushAway without animation
   pushAway: function Item_pushAway(immediately) {
     var items = Items.getTopLevelItems();
     // we need at least two top-level items to push something away
     if (items.length < 2)
       return;
     var buffer = Math.floor(Items.defaultGutter / 2);
     // setup each Item's pushAwayData attribute:
     items.forEach(function pushAway_setupPushAwayData(item) {
       var data = {};
       data.bounds = item.getBounds();
       data.startBounds = new Rect(data.bounds);
       // Infinity = (as yet) unaffected
       data.generation = Infinity;
       item.pushAwayData = data;
     });
     // The first item is a 0-generation pushed item. It all starts here.
     var itemsToPush = [this];
     this.pushAwayData.generation = 0;
     var pushOne = function Item_pushAway_pushOne(baseItem) {
       // the baseItem is an n-generation pushed item. (n could be 0)
       var baseData = baseItem.pushAwayData;
       var bb = new Rect(baseData.bounds);
       // make the bounds larger, adding a +buffer margin to each side.
       bb.inset(-buffer, -buffer);
       // bbc = center of the base's bounds
       var bbc = bb.center();
       items.forEach(function Item_pushAway_pushOne_pushEach(item) {
         if (item == baseItem)
           return;
         var data = item.pushAwayData;
         // if the item under consideration has already been pushed, or has a lower
         // "generation" (and thus an implictly greater placement priority) then don't move it.
         if (data.generation <= baseData.generation)
           return;
         // box = this item's current bounds, with a +buffer margin.
         var bounds = data.bounds;
         var box = new Rect(bounds);
         box.inset(-buffer, -buffer);
         // if the item under consideration overlaps with the base item...
         if (box.intersects(bb)) {
           // Let's push it a little.
           // First, decide in which direction and how far to push. This is the offset.
           var offset = new Point();
           // center = the current item's center.
           var center = box.center();
           // Consider the relationship between the current item (box) + the base item.
           // If it's more vertically stacked than "side by side"...
           if (Math.abs(center.x - bbc.x) < Math.abs(center.y - bbc.y)) {
             // push vertically.
             if (center.y > bbc.y)
               offset.y = bb.bottom - box.top;
             else
               offset.y = bb.top - box.bottom;
           } else { // if they're more "side by side" than stacked vertically...
             // push horizontally.
             if (center.x > bbc.x)
               offset.x = bb.right - box.left;
             else
               offset.x = bb.left - box.right;
           }
           // Actually push the Item.
           bounds.offset(offset);
           // This item now becomes an (n+1)-generation pushed item.
           data.generation = baseData.generation + 1;
           // keep track of who pushed this item.
           data.pusher = baseItem;
           // add this item to the queue, so that it, in turn, can push some other things.
           itemsToPush.push(item);
         }
       });
     };
     // push each of the itemsToPush, one at a time.
     // itemsToPush starts with just [this], but pushOne can add more items to the stack.
     // Maximally, this could run through all Items on the screen.
     while (itemsToPush.length)
       pushOne(itemsToPush.shift());
     // ___ Squish!
     var pageBounds = Items.getSafeWindowBounds();
     items.forEach(function Item_pushAway_squish(item) {
       var data = item.pushAwayData;
       if (data.generation == 0)
         return;
       let apply = function Item_pushAway_squish_apply(item, posStep, posStep2, sizeStep) {
         var data = item.pushAwayData;
         if (data.generation == 0)
           return;
         var bounds = data.bounds;
         bounds.width -= sizeStep.x;
         bounds.height -= sizeStep.y;
         bounds.left += posStep.x;
         bounds.top += posStep.y;
         let validSize;
         if (item.isAGroupItem) {
           validSize = GroupItems.calcValidSize(
             new Point(bounds.width, bounds.height));
           bounds.width = validSize.x;
           bounds.height = validSize.y;
         } else {
           if (sizeStep.y > sizeStep.x) {
             validSize = TabItems.calcValidSize(new Point(-1, bounds.height));
             bounds.left += (bounds.width - validSize.x) / 2;
             bounds.width = validSize.x;
           } else {
             validSize = TabItems.calcValidSize(new Point(bounds.width, -1));
             bounds.top += (bounds.height - validSize.y) / 2;
             bounds.height = validSize.y;
           }
         }
         var pusher = data.pusher;
         if (pusher) {
           var newPosStep = new Point(posStep.x + posStep2.x, posStep.y + posStep2.y);
           apply(pusher, newPosStep, posStep2, sizeStep);
         }
       }
       var bounds = data.bounds;
       var posStep = new Point();
       var posStep2 = new Point();
       var sizeStep = new Point();
       if (bounds.left < pageBounds.left) {
         posStep.x = pageBounds.left - bounds.left;
         sizeStep.x = posStep.x / data.generation;
         posStep2.x = -sizeStep.x;
       } else if (bounds.right > pageBounds.right) { // this may be less of a problem post-601534
         posStep.x = pageBounds.right - bounds.right;
         sizeStep.x = -posStep.x / data.generation;
         posStep.x += sizeStep.x;
         posStep2.x = sizeStep.x;
       }
       if (bounds.top < pageBounds.top) {
         posStep.y = pageBounds.top - bounds.top;
         sizeStep.y = posStep.y / data.generation;
         posStep2.y = -sizeStep.y;
       } else if (bounds.bottom > pageBounds.bottom) { // this may be less of a problem post-601534
         posStep.y = pageBounds.bottom - bounds.bottom;
         sizeStep.y = -posStep.y / data.generation;
         posStep.y += sizeStep.y;
         posStep2.y = sizeStep.y;
       }
       if (posStep.x || posStep.y || sizeStep.x || sizeStep.y)
         apply(item, posStep, posStep2, sizeStep);
     });
     // ___ Unsquish
     var pairs = [];
     items.forEach(function Item_pushAway_setupUnsquish(item) {
       var data = item.pushAwayData;
       pairs.push({
         item: item,
         bounds: data.bounds
       });
     });
     Items.unsquish(pairs);
     // ___ Apply changes
     items.forEach(function Item_pushAway_setBounds(item) {
       var data = item.pushAwayData;
       var bounds = data.bounds;
       if (!bounds.equals(data.startBounds)) {
         item.setBounds(bounds, immediately);
       }
     });
   },
   // ----------
   // Function: setTrenches
   // Sets up/moves the trenches for snapping to this item.
   setTrenches: function Item_setTrenches(rect) {
     if (this.parent !== null)
       return;
     if (!this.borderTrenches)
       this.borderTrenches = Trenches.registerWithItem(this,"border");
     var bT = this.borderTrenches;
     Trenches.getById(bT.left).setWithRect(rect);
     Trenches.getById(bT.right).setWithRect(rect);
     Trenches.getById(bT.top).setWithRect(rect);
     Trenches.getById(bT.bottom).setWithRect(rect);
     if (!this.guideTrenches)
       this.guideTrenches = Trenches.registerWithItem(this,"guide");
     var gT = this.guideTrenches;
     Trenches.getById(gT.left).setWithRect(rect);
     Trenches.getById(gT.right).setWithRect(rect);
     Trenches.getById(gT.top).setWithRect(rect);
     Trenches.getById(gT.bottom).setWithRect(rect);
   },
   // ----------
   // Function: removeTrenches
   // Removes the trenches for snapping to this item.
   removeTrenches: function Item_removeTrenches() {
     for (var edge in this.borderTrenches) {
       Trenches.unregister(this.borderTrenches[edge]); // unregister can take an array
     }
     this.borderTrenches = null;
     for (var edge in this.guideTrenches) {
       Trenches.unregister(this.guideTrenches[edge]); // unregister can take an array
     }
     this.guideTrenches = null;
   },
   // ----------
   // Function: snap
   // The snap function used during groupItem creation via drag-out
   //
   // Parameters:
   //  immediately - bool for having the drag do the final positioning without animation
   snap: function Item_snap(immediately) {
     // make the snapping work with a wider range!
     var defaultRadius = Trenches.defaultRadius;
     Trenches.defaultRadius = 2 * defaultRadius; // bump up from 10 to 20!
     var FauxDragInfo = new Drag(this, {});
     FauxDragInfo.snap('none', false);
     FauxDragInfo.stop(immediately);
     Trenches.defaultRadius = defaultRadius;
   },
   // ----------
   // Function: draggable
   // Enables dragging on this item. Note: not to be called multiple times on the same item!
   draggable: function Item_draggable() {
     try {
       Utils.assert(this.dragOptions, 'dragOptions');
       var cancelClasses = [];
       if (typeof this.dragOptions.cancelClass == 'string')
         cancelClasses = this.dragOptions.cancelClass.split(' ');
       var self = this;
       var $container = iQ(this.container);
       var startMouse;
       var startPos;
       var startSent;
       var startEvent;
       var droppables;
       var dropTarget;
       // determine the best drop target based on the current mouse coordinates
       let determineBestDropTarget = function (e, box) {
         // drop events
         var best = {
           dropTarget: null,
           score: 0
         };
         droppables.forEach(function(droppable) {
           var intersection = box.intersection(droppable.bounds);
           if (intersection && intersection.area() > best.score) {
             var possibleDropTarget = droppable.item;
             var accept = true;
             if (possibleDropTarget != dropTarget) {
               var dropOptions = possibleDropTarget.dropOptions;
               if (dropOptions && typeof dropOptions.accept == "function")
                 accept = dropOptions.accept.apply(possibleDropTarget, [self]);
             }
             if (accept) {
               best.dropTarget = possibleDropTarget;
               best.score = intersection.area();
             }
           }
         });
         return best.dropTarget;
       }
       // ___ mousemove
       var handleMouseMove = function(e) {
         // global drag tracking
         drag.lastMoveTime = Date.now();
         // positioning
         var mouse = new Point(e.pageX, e.pageY);
         if (!startSent) {
           if(Math.abs(mouse.x - startMouse.x) > self.dragOptions.minDragDistance ||
              Math.abs(mouse.y - startMouse.y) > self.dragOptions.minDragDistance) {
             if (typeof self.dragOptions.start == "function")
               self.dragOptions.start.apply(self,
                   [startEvent, {position: {left: startPos.x, top: startPos.y}}]);
             startSent = true;
           }
         }
         if (startSent) {
           // drag events
           var box = self.getBounds();
           box.left = startPos.x + (mouse.x - startMouse.x);
           box.top = startPos.y + (mouse.y - startMouse.y);
           self.setBounds(box, true);
           if (typeof self.dragOptions.drag == "function")
             self.dragOptions.drag.apply(self, [e]);
           let bestDropTarget = determineBestDropTarget(e, box);
           if (bestDropTarget != dropTarget) {
             var dropOptions;
             if (dropTarget) {
               dropOptions = dropTarget.dropOptions;
               if (dropOptions && typeof dropOptions.out == "function")
                 dropOptions.out.apply(dropTarget, [e]);
             }
             dropTarget = bestDropTarget;
             if (dropTarget) {
               dropOptions = dropTarget.dropOptions;
               if (dropOptions && typeof dropOptions.over == "function")
                 dropOptions.over.apply(dropTarget, [e]);
             }
           }
           if (dropTarget) {
             dropOptions = dropTarget.dropOptions;
             if (dropOptions && typeof dropOptions.move == "function")
               dropOptions.move.apply(dropTarget, [e]);
           }
         }
         e.preventDefault();
       };
       // ___ mouseup
       var handleMouseUp = function(e) {
         iQ(gWindow)
           .unbind('mousemove', handleMouseMove)
           .unbind('mouseup', handleMouseUp);
         if (startSent && dropTarget) {
           var dropOptions = dropTarget.dropOptions;
           if (dropOptions && typeof dropOptions.drop == "function")
             dropOptions.drop.apply(dropTarget, [e]);
         }
         if (startSent && typeof self.dragOptions.stop == "function")
           self.dragOptions.stop.apply(self, [e]);
         e.preventDefault();
       };
       // ___ mousedown
       $container.mousedown(function(e) {
         if (!Utils.isLeftClick(e))
           return;
         var cancel = false;
         var $target = iQ(e.target);
         cancelClasses.forEach(function(className) {
           if ($target.hasClass(className))
             cancel = true;
         });
         if (cancel) {
           e.preventDefault();
           return;
         }
         startMouse = new Point(e.pageX, e.pageY);
         let bounds = self.getBounds();
         startPos = bounds.position();
         startEvent = e;
         startSent = false;
         droppables = [];
         iQ('.iq-droppable').each(function(elem) {
           if (elem != self.container) {
             var item = Items.item(elem);
             droppables.push({
               item: item,
               bounds: item.getBounds()
             });
           }
         });
         dropTarget = determineBestDropTarget(e, bounds);
         iQ(gWindow)
           .mousemove(handleMouseMove)
           .mouseup(handleMouseUp);
         e.preventDefault();
       });
     } catch(e) {
       Utils.log(e);
     }
   },
   // ----------
   // Function: droppable
   // Enables or disables dropping on this item.
   droppable: function Item_droppable(value) {
     try {
       var $container = iQ(this.container);
       if (value) {
         Utils.assert(this.dropOptions, 'dropOptions');
         $container.addClass('iq-droppable');
       } else
         $container.removeClass('iq-droppable');
     } catch(e) {
       Utils.log(e);
     }
   },
   // ----------
   // Function: resizable
   // Enables or disables resizing of this item.
   resizable: function Item_resizable(value) {
     try {
       var $container = iQ(this.container);
       iQ('.iq-resizable-handle', $container).remove();
       if (!value) {
         $container.removeClass('iq-resizable');
       } else {
         Utils.assert(this.resizeOptions, 'resizeOptions');
         $container.addClass('iq-resizable');
         var self = this;
         var startMouse;
         var startSize;
         var startAspect;
         // ___ mousemove
         var handleMouseMove = function(e) {
           // global resize tracking
           resize.lastMoveTime = Date.now();
           var mouse = new Point(e.pageX, e.pageY);
           var box = self.getBounds();
           if (UI.rtl) {
             var minWidth = (self.resizeOptions.minWidth || 0);
             var oldWidth = box.width;
             if (minWidth != oldWidth || mouse.x < startMouse.x) {
               box.width = Math.max(minWidth, startSize.x - (mouse.x - startMouse.x));
               box.left -= box.width - oldWidth;
             }
           } else {
             box.width = Math.max(self.resizeOptions.minWidth || 0, startSize.x + (mouse.x - startMouse.x));
           }
           box.height = Math.max(self.resizeOptions.minHeight || 0, startSize.y + (mouse.y - startMouse.y));
           if (self.resizeOptions.aspectRatio) {
             if (startAspect < 1)
               box.height = box.width * startAspect;
             else
               box.width = box.height / startAspect;
           }
           self.setBounds(box, true);
           if (typeof self.resizeOptions.resize == "function")
             self.resizeOptions.resize.apply(self, [e]);
           e.preventDefault();
           e.stopPropagation();
         };
         // ___ mouseup
         var handleMouseUp = function(e) {
           iQ(gWindow)
             .unbind('mousemove', handleMouseMove)
             .unbind('mouseup', handleMouseUp);
           if (typeof self.resizeOptions.stop == "function")
             self.resizeOptions.stop.apply(self, [e]);
           e.preventDefault();
           e.stopPropagation();
         };
         // ___ handle + mousedown
         iQ('<div>')
           .addClass('iq-resizable-handle iq-resizable-se')
           .appendTo($container)
           .mousedown(function(e) {
             if (!Utils.isLeftClick(e))
               return;
             startMouse = new Point(e.pageX, e.pageY);
             startSize = self.getBounds().size();
             startAspect = startSize.y / startSize.x;
             if (typeof self.resizeOptions.start == "function")
               self.resizeOptions.start.apply(self, [e]);
             iQ(gWindow)
               .mousemove(handleMouseMove)
               .mouseup(handleMouseUp);
             e.preventDefault();
             e.stopPropagation();
           });
         }
     } catch(e) {
       Utils.log(e);
     }
   }
 };
 // ##########
 // Class: Items
 // Keeps track of all Items.
 let Items = {
   // ----------
   // Function: toString
   // Prints [Items] for debug use
   toString: function Items_toString() {
     return "[Items]";
   },
   // ----------
   // Variable: defaultGutter
   // How far apart Items should be from each other and from bounds
   defaultGutter: 15,
   // ----------
   // Function: item
   // Given a DOM element representing an Item, returns the Item.
   item: function Items_item(el) {
     return iQ(el).data('item');
   },
   // ----------
   // Function: getTopLevelItems
   // Returns an array of all Items not grouped into groupItems.
   getTopLevelItems: function Items_getTopLevelItems() {
     var items = [];
     iQ('.tab, .groupItem').each(function(elem) {
       var $this = iQ(elem);
       var item = $this.data('item');
       if (item && !item.parent && !$this.hasClass('phantom'))
         items.push(item);
     });
     return items;
   },
   // ----------
   // Function: getPageBounds
   // Returns a <Rect> defining the area of the page <Item>s should stay within.
   getPageBounds: function Items_getPageBounds() {
     var width = Math.max(100, window.innerWidth);
     var height = Math.max(100, window.innerHeight);
     return new Rect(0, 0, width, height);
   },
   // ----------
   // Function: getSafeWindowBounds
   // Returns the bounds within which it is safe to place all non-stationary <Item>s.
   getSafeWindowBounds: function Items_getSafeWindowBounds() {
     // the safe bounds that would keep it "in the window"
     var gutter = Items.defaultGutter;
     // Here, I've set the top gutter separately, as the top of the window has its own
     // extra chrome which makes a large top gutter unnecessary.
     // TODO: set top gutter separately, elsewhere.
     var topGutter = 5;
     return new Rect(gutter, topGutter,
         window.innerWidth - 2 * gutter, window.innerHeight - gutter - topGutter);
   },
   // ----------
   // Function: arrange
   // Arranges the given items in a grid within the given bounds,
   // maximizing item size but maintaining standard tab aspect ratio for each
   //
   // Parameters:
   //   items - an array of <Item>s. Can be null, in which case we won't
   //     actually move anything.
   //   bounds - a <Rect> defining the space to arrange within
   //   options - an object with various properites (see below)
   //
   // Possible "options" properties:
   //   animate - whether to animate; default: true.
   //   z - the z index to set all the items; default: don't change z.
   //   return - if set to 'widthAndColumns', it'll return an object with the
   //     width of children and the columns.
   //   count - overrides the item count for layout purposes;
   //     default: the actual item count
   //   columns - (int) a preset number of columns to use
   //   dropPos - a <Point> which should have a one-tab space left open, used
   //             when a tab is dragged over.
   //
   // Returns:
   //   By default, an object with three properties: `rects`, the list of <Rect>s,
   //   `dropIndex`, the index which a dragged tab should have if dropped
   //   (null if no `dropPos` was specified), and the number of columns (`columns`).
   //   If the `return` option is set to 'widthAndColumns', an object with the
   //   width value of the child items (`childWidth`) and the number of columns
   //   (`columns`) is returned.
   arrange: function Items_arrange(items, bounds, options) {
     if (!options)
       options = {};
     var animate = "animate" in options ? options.animate : true;
     var immediately = !animate;
     var rects = [];
     var count = options.count || (items ? items.length : 0);
     if (options.addTab)
       count++;
     if (!count) {
       let dropIndex = (Utils.isPoint(options.dropPos)) ? 0 : null;
       return {rects: rects, dropIndex: dropIndex};
     }
     var columns = options.columns || 1;
     // We'll assume for the time being that all the items have the same styling
     // and that the margin is the same width around.
     var itemMargin = items && items.length ?
                        parseInt(iQ(items[0].container).css('margin-left')) : 0;
     var padding = itemMargin * 2;
     var rows;
     var tabWidth;
     var tabHeight;
     var totalHeight;
     function figure() {
       rows = Math.ceil(count / columns);
       let validSize = TabItems.calcValidSize(
         new Point((bounds.width - (padding * columns)) / columns, -1),
         options);
       tabWidth = validSize.x;
       tabHeight = validSize.y;
       totalHeight = (tabHeight * rows) + (padding * rows);
     }
     figure();
     while (rows > 1 && totalHeight > bounds.height) {
       columns++;
       figure();
     }
     if (rows == 1) {
       let validSize = TabItems.calcValidSize(new Point(tabWidth,
         bounds.height - 2 * itemMargin), options);
       tabWidth = validSize.x;
       tabHeight = validSize.y;
     }
     if (options.return == 'widthAndColumns')
       return {childWidth: tabWidth, columns: columns};
     let initialOffset = 0;
     if (UI.rtl) {
       initialOffset = bounds.width - tabWidth - padding;
     }
     var box = new Rect(bounds.left + initialOffset, bounds.top, tabWidth, tabHeight);
     var column = 0;
     var dropIndex = false;
     var dropRect = false;
     if (Utils.isPoint(options.dropPos))
       dropRect = new Rect(options.dropPos.x, options.dropPos.y, 1, 1);
     for (let a = 0; a < count; a++) {
       // If we had a dropPos, see if this is where we should place it
       if (dropRect) {
         let activeBox = new Rect(box);
         activeBox.inset(-itemMargin - 1, -itemMargin - 1);
         // if the designated position (dropRect) is within the active box,
         // this is where, if we drop the tab being dragged, it should land!
         if (activeBox.contains(dropRect))
           dropIndex = a;
       }
       // record the box.
       rects.push(new Rect(box));
       box.left += (UI.rtl ? -1 : 1) * (box.width + padding);
       column++;
       if (column == columns) {
         box.left = bounds.left + initialOffset;
         box.top += box.height + padding;
         column = 0;
       }
     }
     return {rects: rects, dropIndex: dropIndex, columns: columns};
   },
   // ----------
   // Function: unsquish
   // Checks to see which items can now be unsquished.
   //
   // Parameters:
   //   pairs - an array of objects, each with two properties: item and bounds. The bounds are
   //     modified as appropriate, but the items are not changed. If pairs is null, the
   //     operation is performed directly on all of the top level items.
   //   ignore - an <Item> to not include in calculations (because it's about to be closed, for instance)
   unsquish: function Items_unsquish(pairs, ignore) {
     var pairsProvided = (pairs ? true : false);
     if (!pairsProvided) {
       var items = Items.getTopLevelItems();
       pairs = [];
       items.forEach(function(item) {
         pairs.push({
           item: item,
           bounds: item.getBounds()
         });
       });
     }
     var pageBounds = Items.getSafeWindowBounds();
     pairs.forEach(function(pair) {
       var item = pair.item;
       if (item == ignore)
         return;
       var bounds = pair.bounds;
       var newBounds = new Rect(bounds);
       var newSize;
       if (Utils.isPoint(item.userSize))
         newSize = new Point(item.userSize);
       else if (item.isAGroupItem)
         newSize = GroupItems.calcValidSize(
           new Point(GroupItems.minGroupWidth, -1));
       else
         newSize = TabItems.calcValidSize(
           new Point(TabItems.tabWidth, -1));
       if (item.isAGroupItem) {
           newBounds.width = Math.max(newBounds.width, newSize.x);
           newBounds.height = Math.max(newBounds.height, newSize.y);
       } else {
         if (bounds.width < newSize.x) {
           newBounds.width = newSize.x;
           newBounds.height = newSize.y;
         }
       }
       newBounds.left -= (newBounds.width - bounds.width) / 2;
       newBounds.top -= (newBounds.height - bounds.height) / 2;
       var offset = new Point();
       if (newBounds.left < pageBounds.left)
         offset.x = pageBounds.left - newBounds.left;
       else if (newBounds.right > pageBounds.right)
         offset.x = pageBounds.right - newBounds.right;
       if (newBounds.top < pageBounds.top)
         offset.y = pageBounds.top - newBounds.top;
       else if (newBounds.bottom > pageBounds.bottom)
         offset.y = pageBounds.bottom - newBounds.bottom;
       newBounds.offset(offset);
       if (!bounds.equals(newBounds)) {
         var blocked = false;
         pairs.forEach(function(pair2) {
           if (pair2 == pair || pair2.item == ignore)
             return;
           var bounds2 = pair2.bounds;
           if (bounds2.intersects(newBounds))
             blocked = true;
           return;
         });
         if (!blocked) {
           pair.bounds.copy(newBounds);
         }
       }
       return;
     });
     if (!pairsProvided) {
       pairs.forEach(function(pair) {
         pair.item.setBounds(pair.bounds);
       });
     }
   }
 };