title: Capture Global Keydown Events (not simply observe)
body: <p>I've created some global hotkeys. However using <code>addGlobalMonitorForEventsMatchingMask</code> I can only observe keydown events. What if I want to capture the event and prevent other applications from receiving it? </p>
  
  <p>Here's what I have for <em>observing</em> keydown events:</p>
  
  <pre><code>    class AppDelegate: NSObject, NSApplicationDelegate {
          func applicationDidFinishLaunching(aNotification: NSNotification) {
              NSEvent.addGlobalMonitorForEventsMatchingMask(.KeyDownMask, handler: keyDown)
              NSEvent.addLocalMonitorForEventsMatchingMask(.KeyDownMask) { (event) -&gt; NSEvent! in
                  self.keyDown(event)
                  return event
              }
          }
          func keyDown(event : NSEvent) {
              if event.modifierFlags.contains(.ControlKeyMask) &amp;&amp; event.modifierFlags.contains(.AlternateKeyMask) &amp;&amp; event.modifierFlags.contains(.CommandKeyMask) &amp;&amp; event.keyCode == 126 {
                  print("⌃⌥⌘↑ pressed")
              }
          }
      }
  </code></pre>
  
  <p>I'm not sure where to start to <em>capture</em> keydown events. Any help would be great. Thanks.</p>