What's the interest of the Viewport.js

[Sempre]

Hello,

My question is on the title : What's the interest of the Viewport.js?
I read "Architecting Your App in Ext JS 4" (http://www.sencha.com/learn/extjs/?4x) and they speak about the Viewport.js. Is this file really importante to have a good app or not? And mostly I have a html page in which I include chart, grid or whatever extjs things and I can't use viewport.js because it include all the view to make the page totaly with extjs and I juste want to have some part like a chart into a div who already are in the page.
If someone could help me It would be very helpful.

Thank you per advance.

PS : Excuse me for my bad English but i'm french

[scottmartin]

It is not required, but if you want to setup your viewport with specific options, you have the option.

If this is not a requirement, then do not create the file.

Scott.