Treffer: Issues, Problems and Solutions in Sharing X Clients on Multiple Displays

This paper describes the salient problems that face the designers of X-based shared window systems and provides solutions and implementation principles for addressing the problems. The enumeration of issues and solutions is based on our experiences with XTV --- an X-based shared window system we have developed. KEY WORDS X protocol, Computer Conferencing, Computer Supported Collaborative Work, Internet Protocols, UNIX Network Programming, Client/Server Model, Distributed Systems. SHARED WINDOW SYSTEMS Growing interest in concurrent engineering and computer-supported cooperative work has led to the development of a number of computer conferencing systems that allow geographically distributed groups of individuals to (simultaneously) view and manipulate shared images, documents, or programs, while they communicate via audio and possibly video links [1-6]. There are two basic approaches to supporting such conferences. The first involves the development of so-called collaboration-aware applications --- specialpurpose applications, that directly support multiple, simultaneously active users. Alternatively, one can leverage the large base of existing single-user applications by augmenting a window system to support the sharing of application interfaces (e.g., windows) across multiple, distributed users. The resulting window system is typically called a shared window system. The X Window System has been a particularly popular vehicle for experimentation with, and development of, shared window systems [1,4,5]. Indeed, we have developed, and placed in the public domain, a shared window system, called XTV (X Teleconferencing and Viewing [1,2]), based on the X Window System. XTV allows a conference to be created around one or more arbitrary X applications. Conferees have the same .