ExtJS 4.1 MVC: How to apply LoadMask for application?
===

How to apply a [LoadMask](http://docs.sencha.com/ext-js/4-1/#!/api/Ext.LoadMask) for a [standard ExtJS MVC application](http://docs.sencha.com/ext-js/4-1/#!/guide/application_architecture) while it is loading the required files?

An example of such MVC application is the following snippet for `app.js`:

    Ext.Loader.setConfig({enabled:true});
    
    Ext.application({
        requires: [
           'Ext.container.Viewport',
        ],
        
        name: 'APP',
        appFolder: 'app',
        
        controllers: [
            'Main'
        ],
    
        launch: function() {
        	
        	Ext.create('Ext.container.Viewport', {
                layout: 'fit',
                items: [
                    {
                    	xtype: 'main'
                    }				
                ]
            });
        }
    });

where `main` above is an `xtype` for an MVC view, that might extend an ExtJS `Panel` etc.

Does a standard approach for this *ubiquitous* requirement exist?