Aside from Jesse and Tim's attendance, the recent NetBeans Platform Certified Training in Boston was special in that the last 2 days (of 5 days) was spent with the students talking about their various Java applications and how those applications might be ported to the NetBeans Platform. One of the presentations was done by a group of developers from a big financial institution who had a JDesktopPane containing a number of JFrames. Each JFrame provides a different tool in the application suite. And, when a JFrame is chosen, the JDesktopPane's menubar (and other items) changes to provide exactly the content relevant for the current tool.
How would such a structure be ported to the NetBeans Platform? Obviously, each JFrame should become a TopComponent. However, what about the JDesktopPane behavior? Switching from one TopComponent to another should add/remove items to/from the menubar and toolbar. Fortunately, Jesse was in the room and he knocked together a solution on the spot.
Below, in the first screenshot, Win1 is selected: