First this is not a tutorial for NSPopover . Just fix for an issue.
Apple introduced NSPopover in OS X v10.7
NSPopover class provides a means to display additional content related to existing content on the screen. The popover is positioned relative to the existing content.
An anchor is used to express the relation between these two units of content. A popover has an appearance that specifies its visual characteristics, as well as a behavior that determines which user interactions will cause the popover to close. …….
But it seems Apple never intended for the NSPopover to be used in a NSStatusBar menu item. Those are the little menu icons in you menu bar that when you click show you info or perform an action. This is probably why Apple has not fixed the bugs when using a popover in this way.