Example project showing usage of the NSPopover+Message category.
[NSPopover showRelativeToRect:[theInput frame] ofView:[theInput superview] preferredEdge:NSMaxXEdge // Show the popover on the right edge string:@"Once upon a time, in a land far, far away, there was a little cake. It didn't last long." maxWidth:250.0];
As described here: User Feedback & Simplifying the NSPopover.