how to use arguments of summaryRenderer method?

[leons1220]

hey,guys! I use Ext.grid.GroupSummary class in my page,like below:
columns: [
{id:'product',
name:'product',
header:"Product",
width:60,
dataIndex:'product',
renderer:productName,
summaryType:'count',
summaryRenderer: function(v, params, data){return "<div style='font-family: Arial, Helvetica,sans-serif;font-size: 12px;color: #FFFFFF;background-color: #DC241F;'>Total</div>";}}

and now,I want to get record datas in function(v, params, data) method by using params and data arguments,I know that the first arguments "v" is return the value of each row,then how to use the second argument "params" and the third argument "data",what do they return ?

[devnull]

Inspect them in firebug.