Encapsulating interactive behaviors

Although there has been important progress in models and packages for the output of graphics to computer screens, there has been little change in the way that input from the mouse, keyboard and other input devices is handled. New graphics standards are still using a ten year old model even though it is widely accepted as inadequate, and most modern window managers simply return a stream of device-dependent input events. This paper presents a new model for how input devices can be handled for highly-interactive, direct manipulation, graphical user interfaces. This model encapsulates interactive behaviors into a few “interactor” object types. Application programs can then create instances of these interactor objects, and the details of the handling of the input devices are separated from the application and from the output graphics.