Windoids: Windows Within Windows...
Measurement in Motion 1.0 had an interesting interface. A document contained a set of measurements, and various objects that could display and modify those measurements. The objects were represented as 'windoids', windows within the document window. MiM 1.0 was a Mac application, so the windoids could depend only on ZooLib's graphics API, with no help from the OS. When demand for a Windows version became overwhelming I implemented a full windowing system that conformed to ZooLib's ZOSWindow API, so that any code that worked within a regular OS window could instead be hosted in a windoid. QuickTime by this point was writing to the screen buffer asynchronously, so any change in the visible region of a windoid is notified before it happens and after its completed, somewhat like the BeOS BDirectWindow mechanism.