I've been wanting popovers for a while and decided to write something that works on Mac and Windows. I only started a couple of days ago so be kind if it sucks...I'd like to improve it. :) I've developed it on Mac and have tested it in Windows 7 running in Parallels. I'm especially curious to know how it works in other versions of Windows.
You can get the code (with sample project) here:
You design the popover as a "Plain Box" window type, set its super to GSPopoverWindow, make sure "Resizeable" is false if you're on Windows, and go. It does some basic automatic placement of where the pointer part goes so if you click in a corner of the screen your window is still visible. And the example I have uses AddHandler to connect TextAreas on the popover to controls on the main window, so as you type it updates the main window too. I'm sure there are other solutions and I'd love to hear them.
A quick screenshot (on mac, running in the IDE):
Also, I'm happy to have other contributors to it, I just don't know the best way to do that.
Let me know how it works for you...