Are tree panels/grid buffered by default ?

Hi guys,

I have a server request that returns me a json string.

The json cannot be used directly into a treeStore, so I have to format it first and then put it in my store like this:

Code:

var store = Ext.create('Ext.data.TreeStore', {
    root: parsedData
});

I use this store in a tree panel/grid setting its store property, defining 6~7 columns.

The json that I get from the server contains an array of parent objects (1200 items), and each parent contains around 5 items. The json file is around 8mo, but the problem is ot the json. The problem is that when I look in the html code (I'm using chrome debugger), every 1200 items of my store are rendered. Even if there are only 20 displayed.

I thougth that tree panel/grid were buffered by default, meaning that only the visible items are generated in the dom.

Am I missing something? Why do it get all items (1200) generated in the dom? (it makes the website very slow ^^")!

Thanks in advance !

PS: I can't call the result from the server in several parts/pages. I have to load all the 1200 items in one time.

Are tree panels/grid buffered by default ?