+ If a dragged item overlaps more than one droppable, the largest intersection wins

+ Added intersection and area to Rect
+ Cleaned out a little debug code

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

@@ -1035,9 +1035,7 @@ window.Group.prototype = iQ.extend(new Item(), new Subscribable(), {
       Groups.setActiveGroup(self);
       return { shouldZoom: true };      
     }*/
-    
-    Utils.log("SHOULD EXPAND?", child)    
-    
+        
     Groups.setActiveGroup(self);
     return { shouldZoom: true };    
     

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

@@ -597,9 +597,14 @@ window.Item.prototype = {
           self.dragOptions.drag.apply(self, [e, {position: box.position()}]);
           
         // drop events
-        var newDropTarget = null;
+        var best = {
+          dropTarget: null,
+          score: 0
+        };
+        
         iQ.each(droppables, function(index, droppable) {
-          if(box.intersects(droppable.bounds)) {
+          var intersection = box.intersection(droppable.bounds);
+          if(intersection && intersection.area() > best.score) {
             var possibleDropTarget = droppable.item;
             var accept = true;
             if(possibleDropTarget != dropTarget) {
@@ -609,13 +614,13 @@ window.Item.prototype = {
             }
             
             if(accept) {
-              newDropTarget = possibleDropTarget;
-              return false;
+              best.dropTarget = possibleDropTarget;
+              best.score = intersection.area();
             }
           }
         });
 
-        if(newDropTarget != dropTarget) {
+        if(best.dropTarget != dropTarget) {
           var dropOptions;
           if(dropTarget) {
             dropOptions = dropTarget.dropOptions;
@@ -623,7 +628,7 @@ window.Item.prototype = {
               dropOptions.out.apply(dropTarget, [e]);
           }
           
-          dropTarget = newDropTarget; 
+          dropTarget = best.dropTarget; 
 
           if(dropTarget) {
             dropOptions = dropTarget.dropOptions;

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

@@ -144,10 +144,12 @@ window.Rect.prototype = {
 		this.height = value - this.top;
   },
 
+  // ----------
   get xRange() {
 		return new Range(this.left,this.right);
   },
   
+  // ----------
   get yRange() {
 		return new Range(this.top,this.bottom);
   },
@@ -160,6 +162,17 @@ window.Rect.prototype = {
         && rect.top < this.bottom);      
   },
   
+  // ----------
+  intersection: function(rect) {
+    var box = new Rect(Math.max(rect.left, this.left), Math.max(rect.top, this.top), 0, 0);
+    box.right = Math.min(rect.right, this.right);
+    box.bottom = Math.min(rect.bottom, this.bottom);
+    if(box.width > 0 && box.height > 0)
+      return box;
+      
+    return null;
+  },
+  
   // ----------
   // Function: containsPoint
   // Returns a boolean denoting if the <Point> is inside of
@@ -193,6 +206,7 @@ window.Rect.prototype = {
     return new Point(this.left + (this.width / 2), this.top + (this.height / 2));
   },
   
+  // ----------
   size: function() {
     return new Point(this.width, this.height);
   },
@@ -202,6 +216,11 @@ window.Rect.prototype = {
     return new Point(this.left, this.top);
   },
   
+  // ----------
+  area: function() {
+    return this.width * this.height;
+  },
+  
   // ----------
   // Function: inset
   // Makes the rect smaller (if the arguments are positive) as if a margin is added all around