title: How can I keep an NSPopUpButton open after the user selects a menu item?
body: <p>I have an NSPopUpButton providing the NSMenu for a status item with a custom view.  The popup button displays a list of links.  When the user selects a link from the list, the link is displayed in the user's browser (in the background).</p>
  
  <p>Naturally, the menu closes every time the user selects a link.</p>
  
  <p>I would like to change this: I want the menu to stay open while the user clicks on various links, all of which can be opened in the background.  The menu can then go away when the user clicks elsewhere.</p>
  
  <p>How can this be accomplished?  Should I subclass NSMenuItem and intercept the mouse clicks somehow?  Overlay a transparent NSView on the popped-up menu and, again, intercept the clicks somehow?  I make these suggestions blithely, but I would have trouble implementing either of these...pointers to the right methods for override would be appreciated.</p>