How do I create a black-bordered bubble window in Cocoa?

I'm talking specifically about the kind you get if you click and hold on an app in the dock, or a folder if list view is enabled. Is it a menu style, or a window flag I can set like the brushed metal-style?

Lots of little free apps seem to use it. http://开发者_开发知识库bambooapps.com/free-stuff/ is a good example.

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Check out MAAttachedWindow.