title: How to apply blur effect to nsview / nswindow?
body: <p>I'm creating an application to the new OS X Yosemite. I want to create an effect that is very common in this new version, opacity. As an example, the effect that I want, is like the one that exists in the "Mail" application. The left view (where we have "Inbox", "Flagged", "Sent", etc.) have a background blur effect.</p>
  
  <p>How can I apply this effect to my application? This effect is applied to NSView or NSWindow?</p>
  
  <p>Thank you!</p>