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@@ -104,6 +104,9 @@
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 <script>
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   var tree = new SortableTree('tree', {
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+    droppable: {
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+      container: ':not(.file)'
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+    },
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     onDrop: function(drag, drop, event){
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       $('log').update($('log').innerHTML + "<p>" + drag.to_params() + "</p>")
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     }

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@@ -134,12 +134,23 @@ SortableTree.Node = Class.create({
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   },
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   onHover: function(drag, drop, overlap) {    
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-    this.dropPosition = overlap < 0.33 ? 'bottom' : overlap > 0.77 ? 'top' : 'insert';
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+		if(this.canContainChildren(drop)) {
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+		  this.dropPosition = overlap < 0.33 ? 'bottom' : overlap > 0.77 ? 'top' : 'insert';
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+		} else {
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+			this.dropPosition = overlap < 0.5 ? 'bottom' : 'top';
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+		}
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     this.mark(drop);
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     // $('log').update('hovering: ' + drop.tagName + ': ' + drop.id + "<br />" + 
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     //                 'classes: ' + drop.className + "<br />" + 
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     //                 'dropPosition: ' + this.dropPosition)
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-  },
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+  },	
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+
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+	canContainChildren: function(element) {
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+		if(this.options.droppable.container) {
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+			return element.match(this.options.droppable.container);
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+		}
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+		return true;
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+	},
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   onDrop: function(drag, drop, event) {
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     drag = this.tree.find(drag);