The source code

    /**
     * @class Ext.tree.TreeNode
     * @extends Ext.data.Node
     * @cfg {String} text The text for this node
     * @cfg {Boolean} expanded true to start the node expanded
     * @cfg {Boolean} allowDrag False to make this node undraggable if {@link #draggable} = true (defaults to true)
     * @cfg {Boolean} allowDrop False if this node cannot have child nodes dropped on it (defaults to true)
     * @cfg {Boolean} disabled true to start the node disabled
     * @cfg {String} icon The path to an icon for the node. The preferred way to do this
     * is to use the cls or iconCls attributes and add the icon via a CSS background image.
     * @cfg {String} cls A css class to be added to the node
     * @cfg {String} iconCls A css class to be added to the nodes icon element for applying css background images
     * @cfg {String} href URL of the link used for the node (defaults to #)
     * @cfg {String} hrefTarget target frame for the link
     * @cfg {Boolean} hidden True to render hidden. (Defaults to false).
     * @cfg {String} qtip An Ext QuickTip for the node
     * @cfg {Boolean} expandable If set to true, the node will always show a plus/minus icon, even when empty
     * @cfg {String} qtipCfg An Ext QuickTip config for the node (used instead of qtip)
     * @cfg {Boolean} singleClickExpand True for single click expand on this node
     * @cfg {Function} uiProvider A UI <b>class</b> to use for this node (defaults to Ext.tree.TreeNodeUI)
     * @cfg {Boolean} checked True to render a checked checkbox for this node, false to render an unchecked checkbox
     * (defaults to undefined with no checkbox rendered)
     * @cfg {Boolean} draggable True to make this node draggable (defaults to false)
     * @cfg {Boolean} isTarget False to not allow this node to act as a drop target (defaults to true)
     * @cfg {Boolean} allowChildren False to not allow this node to have child nodes (defaults to true)
     * @cfg {Boolean} editable False to not allow this node to be edited by an {@link Ext.tree.TreeEditor} (defaults to true)
     * @constructor
     * @param {Object/String} attributes The attributes/config for the node or just a string with the text for the node
     */
    Ext.tree.TreeNode = Ext.extend(Ext.data.Node, {

        constructor : function(attributes){
            attributes = attributes || {};
            if(Ext.isString(attributes)){
                attributes = {text: attributes};
            }
            this.childrenRendered = false;
            this.rendered = false;
            Ext.tree.TreeNode.superclass.constructor.call(this, attributes);
            this.expanded = attributes.expanded === true;
            this.isTarget = attributes.isTarget !== false;
            this.draggable = attributes.draggable !== false && attributes.allowDrag !== false;
            this.allowChildren = attributes.allowChildren !== false && attributes.allowDrop !== false;

            /**
             * Read-only. The text for this node. To change it use <code>{@link #setText}</code>.
             * @type String
             */
            this.text = attributes.text;
            /**
             * True if this node is disabled.
             * @type Boolean
             */
            this.disabled = attributes.disabled === true;
            /**
             * True if this node is hidden.
             * @type Boolean
             */
            this.hidden = attributes.hidden === true;

            this.addEvents(
                /**
                * @event textchange
                * Fires when the text for this node is changed
                * @param {Node} this This node
                * @param {String} text The new text
                * @param {String} oldText The old text
                */
                'textchange',
                /**
                * @event beforeexpand
                * Fires before this node is expanded, return false to cancel.
                * @param {Node} this This node
                * @param {Boolean} deep
                * @param {Boolean} anim
                */
                'beforeexpand',
                /**
                * @event beforecollapse
                * Fires before this node is collapsed, return false to cancel.
                * @param {Node} this This node
                * @param {Boolean} deep
                * @param {Boolean} anim
                */
                'beforecollapse',
                /**
                * @event expand
                * Fires when this node is expanded
                * @param {Node} this This node
                */
                'expand',
                /**
                * @event disabledchange
                * Fires when the disabled status of this node changes
                * @param {Node} this This node
                * @param {Boolean} disabled
                */
                'disabledchange',
                /**
                * @event collapse
                * Fires when this node is collapsed
                * @param {Node} this This node
                */
                'collapse',
                /**
                * @event beforeclick
                * Fires before click processing. Return false to cancel the default action.
                * @param {Node} this This node
                * @param {Ext.EventObject} e The event object
                */
                'beforeclick',
                /**
                * @event click
                * Fires when this node is clicked
                * @param {Node} this This node
                * @param {Ext.EventObject} e The event object
                */
                'click',
                /**
                * @event checkchange
                * Fires when a node with a checkbox's checked property changes
                * @param {Node} this This node
                * @param {Boolean} checked
                */
                'checkchange',
                /**
                * @event beforedblclick
                * Fires before double click processing. Return false to cancel the default action.
                * @param {Node} this This node
                * @param {Ext.EventObject} e The event object
                */
                'beforedblclick',
                /**
                * @event dblclick
                * Fires when this node is double clicked
                * @param {Node} this This node
                * @param {Ext.EventObject} e The event object
                */
                'dblclick',
                /**
                * @event contextmenu
                * Fires when this node is right clicked
                * @param {Node} this This node
                * @param {Ext.EventObject} e The event object
                */
                'contextmenu',
                /**
                * @event beforechildrenrendered
                * Fires right before the child nodes for this node are rendered
                * @param {Node} this This node
                */
                'beforechildrenrendered'
            );

            var uiClass = this.attributes.uiProvider || this.defaultUI || Ext.tree.TreeNodeUI;

            /**
             * Read-only. The UI for this node
             * @type TreeNodeUI
             */
            this.ui = new uiClass(this);
        },

        preventHScroll : true,
        /**
         * Returns true if this node is expanded
         * @return {Boolean}
         */
        isExpanded : function(){
            return this.expanded;
        },

    /**
     * Returns the UI object for this node.
     * @return {TreeNodeUI} The object which is providing the user interface for this tree
     * node. Unless otherwise specified in the {@link #uiProvider}, this will be an instance
     * of {@link Ext.tree.TreeNodeUI}
     */
        getUI : function(){
            return this.ui;
        },

        getLoader : function(){
            var owner;
            return this.loader || ((owner = this.getOwnerTree()) && owner.loader ? owner.loader : (this.loader = new Ext.tree.TreeLoader()));
        },

        // private override
        setFirstChild : function(node){
            var of = this.firstChild;
            Ext.tree.TreeNode.superclass.setFirstChild.call(this, node);
            if(this.childrenRendered && of && node != of){
                of.renderIndent(true, true);
            }
            if(this.rendered){
                this.renderIndent(true, true);
            }
        },

        // private override
        setLastChild : function(node){
            var ol = this.lastChild;
            Ext.tree.TreeNode.superclass.setLastChild.call(this, node);
            if(this.childrenRendered && ol && node != ol){
                ol.renderIndent(true, true);
            }
            if(this.rendered){
                this.renderIndent(true, true);
            }
        },

        // these methods are overridden to provide lazy rendering support
        // private override
        appendChild : function(n){
            if(!n.render && !Ext.isArray(n)){
                n = this.getLoader().createNode(n);
            }
            var node = Ext.tree.TreeNode.superclass.appendChild.call(this, n);
            if(node && this.childrenRendered){
                node.render();
            }
            this.ui.updateExpandIcon();
            return node;
        },

        // private override
        removeChild : function(node, destroy){
            this.ownerTree.getSelectionModel().unselect(node);
            Ext.tree.TreeNode.superclass.removeChild.apply(this, arguments);
            // only update the ui if we're not destroying
            if(!destroy){
                var rendered = node.ui.rendered;
                // if it's been rendered remove dom node
                if(rendered){
                    node.ui.remove();
                }
                if(rendered && this.childNodes.length < 1){
                    this.collapse(false, false);
                }else{
                    this.ui.updateExpandIcon();
                }
                if(!this.firstChild && !this.isHiddenRoot()){
                    this.childrenRendered = false;
                }
            }
            return node;
        },

        // private override
        insertBefore : function(node, refNode){
            if(!node.render){
                node = this.getLoader().createNode(node);
            }
            var newNode = Ext.tree.TreeNode.superclass.insertBefore.call(this, node, refNode);
            if(newNode && refNode && this.childrenRendered){
                node.render();
            }
            this.ui.updateExpandIcon();
            return newNode;
        },

        /**
         * Sets the text for this node
         * @param {String} text
         */
        setText : function(text){
            var oldText = this.text;
            this.text = this.attributes.text = text;
            if(this.rendered){ // event without subscribing
                this.ui.onTextChange(this, text, oldText);
            }
            this.fireEvent('textchange', this, text, oldText);
        },

        /**
         * Sets the icon class for this node.
         * @param {String} cls
         */
        setIconCls : function(cls){
            var old = this.attributes.iconCls;
            this.attributes.iconCls = cls;
            if(this.rendered){
                this.ui.onIconClsChange(this, cls, old);
            }
        },

        /**
         * Sets the tooltip for this node.
         * @param {String} tip The text for the tip
         * @param {String} title (Optional) The title for the tip
         */
        setTooltip : function(tip, title){
            this.attributes.qtip = tip;
            this.attributes.qtipTitle = title;
            if(this.rendered){
                this.ui.onTipChange(this, tip, title);
            }
        },

        /**
         * Sets the icon for this node.
         * @param {String} icon
         */
        setIcon : function(icon){
            this.attributes.icon = icon;
            if(this.rendered){
                this.ui.onIconChange(this, icon);
            }
        },

        /**
         * Sets the href for the node.
         * @param {String} href The href to set
         * @param {String} (Optional) target The target of the href
         */
        setHref : function(href, target){
            this.attributes.href = href;
            this.attributes.hrefTarget = target;
            if(this.rendered){
                this.ui.onHrefChange(this, href, target);
            }
        },

        /**
         * Sets the class on this node.
         * @param {String} cls
         */
        setCls : function(cls){
            var old = this.attributes.cls;
            this.attributes.cls = cls;
            if(this.rendered){
                this.ui.onClsChange(this, cls, old);
            }
        },

        /**
         * Triggers selection of this node
         */
        select : function(){
            var t = this.getOwnerTree();
            if(t){
                t.getSelectionModel().select(this);
            }
        },

        /**
         * Triggers deselection of this node
         * @param {Boolean} silent (optional) True to stop selection change events from firing.
         */
        unselect : function(silent){
            var t = this.getOwnerTree();
            if(t){
                t.getSelectionModel().unselect(this, silent);
            }
        },

        /**
         * Returns true if this node is selected
         * @return {Boolean}
         */
        isSelected : function(){
            var t = this.getOwnerTree();
            return t ? t.getSelectionModel().isSelected(this) : false;
        },

        /**
         * Expand this node.
         * @param {Boolean} deep (optional) True to expand all children as well
         * @param {Boolean} anim (optional) false to cancel the default animation
         * @param {Function} callback (optional) A callback to be called when
         * expanding this node completes (does not wait for deep expand to complete).
         * Called with 1 parameter, this node.
         * @param {Object} scope (optional) The scope (<code>this</code> reference) in which the callback is executed. Defaults to this TreeNode.
         */
        expand : function(deep, anim, callback, scope){
            if(!this.expanded){
                if(this.fireEvent('beforeexpand', this, deep, anim) === false){
                    return;
                }
                if(!this.childrenRendered){
                    this.renderChildren();
                }
                this.expanded = true;
                if(!this.isHiddenRoot() && (this.getOwnerTree().animate && anim !== false) || anim){
                    this.ui.animExpand(function(){
                        this.fireEvent('expand', this);
                        this.runCallback(callback, scope || this, [this]);
                        if(deep === true){
                            this.expandChildNodes(true, true);
                        }
                    }.createDelegate(this));
                    return;
                }else{
                    this.ui.expand();
                    this.fireEvent('expand', this);
                    this.runCallback(callback, scope || this, [this]);
                }
            }else{
               this.runCallback(callback, scope || this, [this]);
            }
            if(deep === true){
                this.expandChildNodes(true);
            }
        },

        runCallback : function(cb, scope, args){
            if(Ext.isFunction(cb)){
                cb.apply(scope, args);
            }
        },

        isHiddenRoot : function(){
            return this.isRoot && !this.getOwnerTree().rootVisible;
        },

        /**
         * Collapse this node.
         * @param {Boolean} deep (optional) True to collapse all children as well
         * @param {Boolean} anim (optional) false to cancel the default animation
         * @param {Function} callback (optional) A callback to be called when
         * expanding this node completes (does not wait for deep expand to complete).
         * Called with 1 parameter, this node.
         * @param {Object} scope (optional) The scope (<code>this</code> reference) in which the callback is executed. Defaults to this TreeNode.
         */
        collapse : function(deep, anim, callback, scope){
            if(this.expanded && !this.isHiddenRoot()){
                if(this.fireEvent('beforecollapse', this, deep, anim) === false){
                    return;
                }
                this.expanded = false;
                if((this.getOwnerTree().animate && anim !== false) || anim){
                    this.ui.animCollapse(function(){
                        this.fireEvent('collapse', this);
                        this.runCallback(callback, scope || this, [this]);
                        if(deep === true){
                            this.collapseChildNodes(true);
                        }
                    }.createDelegate(this));
                    return;
                }else{
                    this.ui.collapse();
                    this.fireEvent('collapse', this);
                    this.runCallback(callback, scope || this, [this]);
                }
            }else if(!this.expanded){
                this.runCallback(callback, scope || this, [this]);
            }
            if(deep === true){
                var cs = this.childNodes;
                for(var i = 0, len = cs.length; i < len; i++) {
                	cs[i].collapse(true, false);
                }
            }
        },

        // private
        delayedExpand : function(delay){
            if(!this.expandProcId){
                this.expandProcId = this.expand.defer(delay, this);
            }
        },

        // private
        cancelExpand : function(){
            if(this.expandProcId){
                clearTimeout(this.expandProcId);
            }
            this.expandProcId = false;
        },

        /**
         * Toggles expanded/collapsed state of the node
         */
        toggle : function(){
            if(this.expanded){
                this.collapse();
            }else{
                this.expand();
            }
        },

        /**
         * Ensures all parent nodes are expanded, and if necessary, scrolls
         * the node into view.
         * @param {Function} callback (optional) A function to call when the node has been made visible.
         * @param {Object} scope (optional) The scope (<code>this</code> reference) in which the callback is executed. Defaults to this TreeNode.
         */
        ensureVisible : function(callback, scope){
            var tree = this.getOwnerTree();
            tree.expandPath(this.parentNode ? this.parentNode.getPath() : this.getPath(), false, function(){
                var node = tree.getNodeById(this.id);  // Somehow if we don't do this, we lose changes that happened to node in the meantime
                tree.getTreeEl().scrollChildIntoView(node.ui.anchor);
                this.runCallback(callback, scope || this, [this]);
            }.createDelegate(this));
        },

        /**
         * Expand all child nodes
         * @param {Boolean} deep (optional) true if the child nodes should also expand their child nodes
         */
        expandChildNodes : function(deep, anim) {
            var cs = this.childNodes,
                i,
                len = cs.length;
            for (i = 0; i < len; i++) {
            	cs[i].expand(deep, anim);
            }
        },

        /**
         * Collapse all child nodes
         * @param {Boolean} deep (optional) true if the child nodes should also collapse their child nodes
         */
        collapseChildNodes : function(deep){
            var cs = this.childNodes;
            for(var i = 0, len = cs.length; i < len; i++) {
            	cs[i].collapse(deep);
            }
        },

        /**
         * Disables this node
         */
        disable : function(){
            this.disabled = true;
            this.unselect();
            if(this.rendered && this.ui.onDisableChange){ // event without subscribing
                this.ui.onDisableChange(this, true);
            }
            this.fireEvent('disabledchange', this, true);
        },

        /**
         * Enables this node
         */
        enable : function(){
            this.disabled = false;
            if(this.rendered && this.ui.onDisableChange){ // event without subscribing
                this.ui.onDisableChange(this, false);
            }
            this.fireEvent('disabledchange', this, false);
        },

        // private
        renderChildren : function(suppressEvent){
            if(suppressEvent !== false){
                this.fireEvent('beforechildrenrendered', this);
            }
            var cs = this.childNodes;
            for(var i = 0, len = cs.length; i < len; i++){
                cs[i].render(true);
            }
            this.childrenRendered = true;
        },

        // private
        sort : function(fn, scope){
            Ext.tree.TreeNode.superclass.sort.apply(this, arguments);
            if(this.childrenRendered){
                var cs = this.childNodes;
                for(var i = 0, len = cs.length; i < len; i++){
                    cs[i].render(true);
                }
            }
        },

        // private
        render : function(bulkRender){
            this.ui.render(bulkRender);
            if(!this.rendered){
                // make sure it is registered
                this.getOwnerTree().registerNode(this);
                this.rendered = true;
                if(this.expanded){
                    this.expanded = false;
                    this.expand(false, false);
                }
            }
        },

        // private
        renderIndent : function(deep, refresh){
            if(refresh){
                this.ui.childIndent = null;
            }
            this.ui.renderIndent();
            if(deep === true && this.childrenRendered){
                var cs = this.childNodes;
                for(var i = 0, len = cs.length; i < len; i++){
                    cs[i].renderIndent(true, refresh);
                }
            }
        },

        beginUpdate : function(){
            this.childrenRendered = false;
        },

        endUpdate : function(){
            if(this.expanded && this.rendered){
                this.renderChildren();
            }
        },

        //inherit docs
        destroy : function(silent){
            if(silent === true){
                this.unselect(true);
            }
            Ext.tree.TreeNode.superclass.destroy.call(this, silent);
            Ext.destroy(this.ui, this.loader);
            this.ui = this.loader = null;
        },

        // private
        onIdChange : function(id){
            this.ui.onIdChange(id);
        }
    });

    Ext.tree.TreePanel.nodeTypes.node = Ext.tree.TreeNode;