2002 FREENIX Track Technical Program - Abstract
The Future is Coming: Where the X Window System Should Go
Cambridge Research Laboratory, Compaq Computer Corporation
The X Window System was developed as a desktop window system, in a
large (for its time) campus scale network environment. In the
last few years, it has escaped the desktop and appeared in laptop,
handheld and other mobile network devices. X from its inception has
been a network transparent window system, and should thrive in this
environment. Mobility forces a set of issues to surface that were only
partially foreseen in X's design. For one reason or other, the hopes
for the design were not entirely realized.
Our original view of X's use included highly mobile individuals
(students moving between classes), and a hope, never generally
realized for X, was the migration of applications between X servers.
Toolkit implementers typically did not understand and share this
poorly enunciated vision and were primarily driven by pressing
immediate needs, and X's design and implementation made migration or
replication difficult to implement as an afterthought. As a result,
migration (and replication) was seldom implemented, and early toolkits
such as Xt made it very difficult. Emacs is about the
only widespread application capable of both migration and replication,
and it avoided using any toolkit.
You should be able to travel between work and home or between systems
running X at work and retrieve your running applications (with
suitable authentication and authorization). You should be able to log
out and ``park'' your applications somewhere until you retrieve them
later, either on the same display, or somewhere else. You should be
able to migrate your application's display from a handheld to a wall
projector (for example, your presentation), and back again.
Applications should be able to easily survive the loss of the X server
(most commonly caused by the loss of the underlying TCP connection,
when running remotely).
There are challenges not fully foreseen: applications must be able to
adapt between highly variable display architectures. Changes to the X
infrastructure in recent work make this retrofit into modern toolkits
appear feasible, enabling a much more dynamic view of
applications. Also, applications must be able to adapt between very
different resolution displays (more than an order of magnitude) and
differing pointing devices.
I cover the changes and infrastructure required to
realize this vision, and hope to demonstrate a compelling part of this
vision in action.
This vision provides a much more compelling vision of what
it means for applications to work in your network. With the advent
of high speed metropolitan and wide area networks, and PDA's with high
speed wireless networks, this vision will provide a key element of the coming
pervasive computing system.
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