title: Cocoa: enterFullScreenMode with transparent background
body: <p>Is there a possibility to have a NSView in fullscreen-mode with a transparent background window, like a transparent overlay over the underlying desktop?</p>
  
  <pre><code>view.enterFullScreenMode(view.window!.screen!, withOptions: nil )
  view.window!.backgroundColor = NSColor(calibratedRed: 1, green: 0, blue: 0, alpha: 0.01)
  </code></pre>
  
  <p>I can set the color of the view's window, but there always seems to be another black window behind it.</p>