Graphical techniques in a spreadsheet for specifying user interfaces

Many modem user interface development environments use constraints to connect graphical objects. Constraints are relationships that are de&red once and then maintained by the system. Often, systems provide graphical, iconic, or demonstrational techniques for specifying some constraints, but these are incapable of expressing all desired relationships, and it is always necessary to allow the user interface designer to write code to specify complex constraints. The spreadsheet interface described here, called C32, provides the programmer with the full power of writing constraint code in the underlying programming language, but it is significantly easier to use. Unlike other spreadsheets tools for gmphics, C32 automatically generates appropriate object references from mouse clicks in graphics windows and uses inferencing and demonstrational techniques to make constructing and copying constraints easier. In addition, C32 also supports monitoring and debugging interfaces by watching values in the spreadsheet while the user interface is running.