title: How can I limit the "pop-up" size of NSPopUpButton?
body: <p>I have a large list - over 200 items - managed by an NSPopUpButton. When clicked, the list extends all the way to the top or bottom of the screen and beyond.</p>
  
  <p>How can I limit the open size, so that at most 20 or so items are shown at once?</p>