ExtJS - Pie Chart

Ext.onReady(function()  
{  
    var store = Ext.create('Ext.data.ArrayStore',   
    {  
        fields:   
        [  
            {name: 'os'},  					 // default for string  
            {name: 'visits', type: 'int'}  
        ],  
        data:   
        [  
            ['Windows','21548'],  
            ['Linux', '19864'],  
            ['Mac OS', '18459'],  
            ['Android','5762'],  
            ['iOS', '5635']  
        ]  
    });  
  
    Ext.create('Ext.window.Window',  
    {  
        title: 'Pie Chart',  
        width: 550,  
        height: 400,  
        layout: 'fit',  
        items:   
        {  
            xtype: 'chart',  
            animate: true,  
            shadow: true,  		 //  ？  ， 。  
            store: store,  
            legend: {position: 'right'},  
            series:   
            [  
                {  
                    type: 'pie',  
					angleField: 'visits', 		//   field
                    showInLegend: true,  
					insetPadding: 30,
                    highlightDuration: 200,     // the last time of animation  
                    colorSet: ['#4EEE94','#63B8FF','#836FFF','#8A2BE2','#7FFF00'],  	//  
                    label:   
                    {  
                        field: 'os',  
                        display: 'rotate',      //  ， API  
                        contrast: true,         //  ，   
                        font: '16px Arial',   
                    },  
                    tips:   
                    {  
                        trackMouse: true,  
                        width: 150,  
                        height: 30,   
                        renderer: function(storeItem, item) {  
                            var total = 0;  
                            store.each(function(rec) {  
                                total += rec.get('visits');  
                            });  
                            this.setTitle(storeItem.get('os') + ': ' + Math.round(storeItem.get('visits') / total * 100) + '%');  
                        }  
                    },  
                    highlight:   
                    {  
                        segment: { margin: 20 }     //    
                    },  
                    donut: 40 						//  40%  
                }  
            ]  
        }  
    }).show();  
});