README file for Xvan 1.2 (X11/R6 multiple screen server)
	Peter C. Jones, Sun Microsystems Laboratories, Chelmsford, MA
	last updated June 1995

This is the README file for the X11/R6 version of the Xvan server.
This latest release features a couple of bug fixes and the necessary
updates to remain consistent with patch level 11 of the X11/R6
distribution.

Xvan is a modification of the X11/R6 sample server that allows
multiple physical screens to comprise one logical screen.  It is
currently only fully implemented for Sun workstations, so there is
only one machine-specific subdirectory, "sun", in the "hw" branch of
the source tree.  However, for any other machine that could use the
code in the standard "mfb" and "cfb*" directories, it should be rather
simple to port Xvan functionality.

Building Xvan
=============

The file Xvan-1.2.tar should be unpacked in the base directory of the
X11/R6 source tree (the one with the "xc" and "contrib" subdirectories
in it).  It will create a "Xvan" directory tree in the "xc/programs"
directory similar to the "Xserver" tree.

- In the Imakefile in the "xc/programs" directory, add "Xvan" to the
list of directories assigned to the "XSDIR" variable.  The line will
then probably look like this:

	XSDIR = Xserver Xvan

- To just build the Xvan server, enter the following commands from
within the "xc/programs/Xvan" directory:
	% xmkmf -a ../.. programs/Xvan
	% make
and the various executables will be generated both in that directory
and in the "xc/programs/Xvan/hw/sun" directory.  (Alternatively, to
rebuild the entire X11/R6 build tree, execute a "make World" or a
"make Everything", as appropriate, from the top level "xc" directory.)

- To install the executables and man pages in the binary target tree,
enter the following commands from within the "xc/programs/Xvan"
directory (as root):
	% make install
	% make install.man

On any Sun machine running SunOS 4.x or SunOS 5.x, you should be able
to build Xvan just like any other piece of the X11/R6 package.  The
sunGX graphics accelerator, used with cgsix* screen devices, is fully
supported.

Note that Xvan for X11/R6 requires a C++ compiler for some pieces of
the server.  It was tested with SPARCompiler C++ 4.0.1.

Starting Xvan
=============

The command line interface to the standard server has been slightly
enhanced to access Xvan's mutiple screen functionality.  The "-dev"
command line switch to the "Xvan" command allows you to use the plus
(+) operator to combine multiple screens into one logical screen.  A
comma (,) followed by an appropriate direction keyword indicates the
desired relative position of this screen to the previous one.  The
allowable direction keywords are "left", "right", "top", and "bottom".
If no direction keyword is specified for a screen device (other than
the first one), then that screen is placed logically to the right of
the previous one.  The colon (:) operator still serves to specify
using multiple screens the standard X way, i.e., multiple logical
screens.

For example, the following command will start up Xvan with two
screens, /dev/cgsix0 and /dev/cgsix1, side by side, with the latter
on the right:

% Xvan -dev /dev/cgsix0+/dev/cgsix1

This more complicated example illustrates a way to set up a 2x2
screen grid with cgsix0 and cgsix1 across the top row, and with
cgsix2 and cgsix3 across the bottom row:

% Xvan -dev /dev/cgsix1+/dev/cgsix3,bottom+/dev/cgsix2,left+/dev/cgsix0,top

Of course, the server will normally be started within another command,
such as "xinit", as shown in the following command (which assumes that
the default server "X" is linked to Xvan):

% xinit -- -dev /dev/cgsix0+/dev/cgsix1

The logical screen must be rectangular, but it is possible with the
command syntax to set up a non-rectangular combination of the
available physical screens (with three or more).  Xvan will create
the logical screen to be a rectangle enclosing all the specified
physical screens, but the behavior of windows that reside in the 
areas of the logical screen that are not physically mapped will be
incorrest.  Also, it is possible to use the same physical screen in
more than one place on the logical screen, with the resulting
behavior being erroneous as would be expected.

	Questions or comments can be sent to:
	Peter.C.Jones@East.Sun.COM