Masking components, views

I am looking to add functionality to mask elements of my UI similar to sencha’s implementation of .mask.

I have found the following snippet (http://webix.com/snippet/12c87361), this however masks the whole interface.

I have a popup window and am looking to mask everything behind it. If I could target a element by ID and mask it this would work as well.

You may consider the ProgressBar functionality that is applicable to both views and layouts: http://docs.webix.com/samples/19_api/05_progress_app.html