The source code

    /*!
     * Ext JS Library 3.4.0
     * Copyright(c) 2006-2011 Sencha Inc.
     * licensing@sencha.com
     * http://www.sencha.com/license
     */
    Ext.tree.TreeEventModel = function(tree){
        this.tree = tree;
        this.tree.on('render', this.initEvents, this);
    };

    Ext.tree.TreeEventModel.prototype = {
        initEvents : function(){
            var t = this.tree;

            if(t.trackMouseOver !== false){
                t.mon(t.innerCt, {
                    scope: this,
                    mouseover: this.delegateOver,
                    mouseout: this.delegateOut
                });
            }
            t.mon(t.getTreeEl(), {
                scope: this,
                click: this.delegateClick,
                dblclick: this.delegateDblClick,
                contextmenu: this.delegateContextMenu
            });
        },

        getNode : function(e){
            var t;
            if(t = e.getTarget('.x-tree-node-el', 10)){
                var id = Ext.fly(t, '_treeEvents').getAttribute('tree-node-id', 'ext');
                if(id){
                    return this.tree.getNodeById(id);
                }
            }
            return null;
        },

        getNodeTarget : function(e){
            var t = e.getTarget('.x-tree-node-icon', 1);
            if(!t){
                t = e.getTarget('.x-tree-node-el', 6);
            }
            return t;
        },

        delegateOut : function(e, t){
            if(!this.beforeEvent(e)){
                return;
            }
            if(e.getTarget('.x-tree-ec-icon', 1)){
                var n = this.getNode(e);
                this.onIconOut(e, n);
                if(n == this.lastEcOver){
                    delete this.lastEcOver;
                }
            }
            if((t = this.getNodeTarget(e)) && !e.within(t, true)){
                this.onNodeOut(e, this.getNode(e));
            }
        },

        delegateOver : function(e, t){
            if(!this.beforeEvent(e)){
                return;
            }
            if(Ext.isGecko && !this.trackingDoc){ // prevent hanging in FF
                Ext.getBody().on('mouseover', this.trackExit, this);
                this.trackingDoc = true;
            }
            if(this.lastEcOver){ // prevent hung highlight
                this.onIconOut(e, this.lastEcOver);
                delete this.lastEcOver;
            }
            if(e.getTarget('.x-tree-ec-icon', 1)){
                this.lastEcOver = this.getNode(e);
                this.onIconOver(e, this.lastEcOver);
            }
            if(t = this.getNodeTarget(e)){
                this.onNodeOver(e, this.getNode(e));
            }
        },

        trackExit : function(e){
            if(this.lastOverNode){
                if(this.lastOverNode.ui && !e.within(this.lastOverNode.ui.getEl())){
                    this.onNodeOut(e, this.lastOverNode);
                }
                delete this.lastOverNode;
                Ext.getBody().un('mouseover', this.trackExit, this);
                this.trackingDoc = false;
            }

        },

        delegateClick : function(e, t){
            if(this.beforeEvent(e)){
                if(e.getTarget('input[type=checkbox]', 1)){
                    this.onCheckboxClick(e, this.getNode(e));
                }else if(e.getTarget('.x-tree-ec-icon', 1)){
                    this.onIconClick(e, this.getNode(e));
                }else if(this.getNodeTarget(e)){
                    this.onNodeClick(e, this.getNode(e));
                }
            }else{
                this.checkContainerEvent(e, 'click');
            }
        },

        delegateDblClick : function(e, t){
            if(this.beforeEvent(e)){
                if(this.getNodeTarget(e)){
                    this.onNodeDblClick(e, this.getNode(e));
                }
            }else{
                this.checkContainerEvent(e, 'dblclick');
            }
        },

        delegateContextMenu : function(e, t){
            if(this.beforeEvent(e)){
                if(this.getNodeTarget(e)){
                    this.onNodeContextMenu(e, this.getNode(e));
                }
            }else{
                this.checkContainerEvent(e, 'contextmenu');
            }
        },

        checkContainerEvent: function(e, type){
            if(this.disabled){
                e.stopEvent();
                return false;
            }
            this.onContainerEvent(e, type);
        },

        onContainerEvent: function(e, type){
            this.tree.fireEvent('container' + type, this.tree, e);
        },

        onNodeClick : function(e, node){
            node.ui.onClick(e);
        },

        onNodeOver : function(e, node){
            this.lastOverNode = node;
            node.ui.onOver(e);
        },

        onNodeOut : function(e, node){
            node.ui.onOut(e);
        },

        onIconOver : function(e, node){
            node.ui.addClass('x-tree-ec-over');
        },

        onIconOut : function(e, node){
            node.ui.removeClass('x-tree-ec-over');
        },

        onIconClick : function(e, node){
            node.ui.ecClick(e);
        },

        onCheckboxClick : function(e, node){
            node.ui.onCheckChange(e);
        },

        onNodeDblClick : function(e, node){
            node.ui.onDblClick(e);
        },

        onNodeContextMenu : function(e, node){
            node.ui.onContextMenu(e);
        },

        beforeEvent : function(e){
            var node = this.getNode(e);
            if(this.disabled || !node || !node.ui){
                e.stopEvent();
                return false;
            }
            return true;
        },

        disable: function(){
            this.disabled = true;
        },

        enable: function(){
            this.disabled = false;
        }
    };