The X PaperLikeInterface extension (xpli)


This extension to the X11R5 system provides protocol, server, and
library extensions for pen-based (or notepad) user interfaces. The user
holds an electronic pen, and uses it to write directly on the face of
a display, seeing a trail of ink where the pen contacts the display
surface. Typically, the pen digitizer is electromagnetic, and the
display is a monochrome LCD.

Sample code is supplied for the IBM RS-6000, using a pen digitizer 
and display configuration built by the IBM Thomas J. Watson Research
Center. However, it should not be very difficult to modify the
sample code for other notepad hardware, as the digitizer attaches
via a serial RS-232C port, and the display is an extension of the
IBM VGA display interface.

The compressed tar file will unload into the extensions directory
of an X tree; in particular, it will create subdirectories named
"xpli" in the server, lib, include, and test subdirectories of
extensions. In extensions/server/xpli/xplipatch is a set of patches
which need to be applied from the top directory of the mit tree.
These patches affect the ibm.cf configuration file, and various
Imakefiles in the tree, and alter some of the dix modules.

In addition, on the IBM RS-6000, it is necessary to add an
extension to the AIX 3 kernel that allows the X server to access the
VGA/LCD display engine over the I/O bus. This kernel extension
will be found in extensions/test/xpli/plikext/plikext. It is
added to the kernel using addplikext, and deleted from the kernel
using delplikext programs found in this same directory. We apologise
for not providing source for this kernel extension at this time,
but have not yet received permission to release it. See the README
file in this directory for additional explanation about the function
of the kernel extension.

The X11R5 implementation is based in previous implementations
on R2, R3, and R4 and on the IBM RT/PC and PS/2. Many have
contributed to this effort, particularly Michael Sacks,
Erb Cooper, Howard Page, John Gerth, Haakan Winbom, and P. R. Kumar.
Without the work of the X Consortium and X contributors, our
project would have been difficult and our solutions incomplete.

We are very interested in suggestions, contributions, and assistance
from the X community on the protocol and sample implementation.
Please address correspondence to 
	Jim Rhyne  or  Doris Chow
	IBM T. J. Watson Research Center
	P.O. Box 704 
	Yorktown Hgts, NY 10598
	jrhyne@watson.ibm.com
	dychin@watson.ibm.com

We expect to release future developments to the X11R5 implementation
via patches. Watch this space.

We are planning to add to the protocol and implementation
to support stroke recognition in the server environment, but do not
plan to contribute recognizer implementations. The paper in the 1991
SIGGRAPH Proceedings by Dean Rubine has a nice algorithm for
single stroke gesture recognition. We anticipate supporting
recognition code which is a part of the server, as well as
recognition services provided by recognition server processes.

Status: 10/2/91
	Against the X tree with public patches 1-3 applied,
	the server and libraries build without error. The server
	crashes with a variety of problems. The library functions
	do not completely cover the defined protocol. The server
	does not correctly implement the screen switch when used 
	in a multihead configuration. Expect patches around the
	first of December, 1991.