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.\" $XFree86: xc/programs/Xserver/hw/xnest/Xnest.man,v 1.6 2001/01/27 18:21:00 dawes Exp $
.\"
.TH Xnest 1 "xorg-server 21.1.14" "X Version 11"
.SH NAME
Xnest \- a nested X server
.SH SYNOPSIS
.B Xnest
[
.I options
]
.SH DESCRIPTION
.B Xnest
is both an X client and an X server.
.B Xnest
is a client of the real server which manages windows and graphics requests on
its behalf.
.B Xnest
is a server to its own clients.
.B Xnest
manages windows and graphics requests on their behalf.
To these clients,
.B Xnest
appears to be a conventional server.
.SH OPTIONS
.B Xnest
supports all standard options of the sample server implementation.
For more details, please see
.BR Xserver (1).
The following additional arguments are supported as well.
.TP
.BI "\-display " string
This option specifies the display name of the real server that
.B Xnest
should try to connect to.
If it is not provided on the command line,
.B Xnest
will read the
.I DISPLAY
environment variable in order to find out this information.
.TP
.B \-sync
This option tells
.B Xnest
to synchronize its window and graphics operations with the real server.
This is a useful option for debugging, but it will slow down
.BR Xnest 's
performance considerably.
It should not be used unless absolutely necessary.
.TP
.B \-full
This option tells
.B Xnest
to utilize full regeneration of real server objects and reopen a new connection
to the real server each time the nested server regenerates.
The sample server implementation regenerates all objects in the server when the
last client of this server terminates.
When this happens,
.B Xnest
by default maintains the same top-level window and the same real server
connection in each new generation.
If the user selects full regeneration, even the top-level window and the
connection to the real server will be regenerated for each server generation.
.TP
.BI "\-class " string
This option specifies the default visual class of the nested server.
It is similar to the
.B \-cc
option from the set of standard options except that it will accept a string
rather than a number for the visual class specification.
The
.I string
must be one of the following six values:
.BR StaticGray ,
.BR GrayScale ,
.BR StaticColor ,
.BR PseudoColor ,
.BR TrueColor ,
or
.BR DirectColor .
If both the
.B \-class
and
.B \-cc
options are specified, the last instance of either option takes precedence.
The class of the default visual of the nested server need not be the same as the
class of the default visual of the real server, but it must be supported by the
real server.
Use
.BR xdpyinfo (1)
to obtain a list of supported visual classes on the real server before starting
.BR Xnest .
If the user chooses a static class, all the colors in the default color map will
be preallocated.
If the user chooses a dynamic class, colors in the default color map will be
available to individual clients for allocation.
.TP
.BI "\-depth " int
This option specifies the default visual depth of the nested server.
The depth of the default visual of the nested server need not be the same as the
depth of the default visual of the real server, but it must be supported by the
real server.
Use
.BR xdpyinfo (1)
to obtain a list of supported visual depths on the real server before starting
.BR Xnest .
.TP
.B \-sss
This option tells
.B Xnest
to use the software screen saver.
By default,
.B Xnest
will use the screen saver that corresponds to the hardware screen saver in the
real server.
Of course, even this screen saver is software-generated since
.B Xnest
does not control any actual hardware.
However, it is treated as a hardware screen saver within the sample server code.
.TP
.B \-geometry \fIW\fBx\fIH\fB+\fIX\fB+\fIY\fP
This option specifies the geometry parameters for the top-level
.B Xnest
window.
See \(lqGEOMETRY SPECIFICATIONS\(rq in
.BR X (7)
for a discussion of this option's syntax.
This window corresponds to the root window of the nested server.
The width
.I W
and height
.I H
specified with this option will be the maximum width and height of each
top-level
.B Xnest
window.
.B Xnest
will allow the user to make any top-level window smaller, but it will not
actually change the size of the nested server root window.
.B Xnest
does not yet support the RANDR extension for resizing, rotation, and reflection
of the root window.
If this option is not specified,
.B Xnest
will choose
.I W
and
.I H
to be 3/4ths the dimensions of the root window of the real server.
.TP
.BI "\-bw " int
This option specifies the border width of the top-level
.B Xnest
window.
The integer parameter
.I int
must be positive.
The default border width is 1.
.TP
.BI "\-name " string
This option specifies the name of the top-level
.B Xnest
window as
.IR string .
The default value is the program name.
.TP
.BI "\-scrns " int
This option specifies the number of screens to create in the nested server.
For each screen,
.B Xnest
will create a separate top-level window.
Each screen is referenced by the number after the dot in the client display name
specification.
For example,
.B xterm \-display :1.1
will open an
.BR xterm (1)
client in the nested server with the display number
.B :1
on the second screen.
The number of screens is limited by the hard-coded constant in the server sample
code, which is usually 3.
.TP
.B \-install
This option tells
.B Xnest
to do its own color map installation by bypassing the real window manager.
For it to work properly, the user will probably have to temporarily quit the
real window manager.
By default,
.B Xnest
will keep the nested client window whose color map should be installed in the
real server in the
.I WM_COLORMAP_WINDOWS
property of the top-level
.B Xnest
window.
If this color map is of the same visual type as the root window of the nested
server,
.B Xnest
will associate this color map with the top-level
.B Xnest
window as well.
Since this does not have to be the case, window managers should look primarily
at the
.I WM_COLORMAP_WINDOWS
property rather than the color map associated with the top-level
.B Xnest
window.
.\" Is the following still true?  This sentence is several years old.
Unfortunately, window managers are not very good at doing that yet so this
option might come in handy.
.TP
.BI "\-parent " window_id
This option tells
.B Xnest
to use
.I window_id
as the root window instead of creating a window.
.\" XRX is dead, dead, dead.
.\" This option is used by the xrx xnestplugin.
.SH "EXTENDED DESCRIPTION"
Starting up
.B Xnest
is just as simple as starting up
.BR xclock (1)
from a terminal emulator.
If a user wishes to run
.B Xnest
on the same
workstation as the real server, it is important that the nested server is given
its own listening socket address.
Therefore, if there is a server already running on the user's workstation,
.B Xnest
will have to be started up with a new display number.
Since there is usually no more than one server running on a workstation,
specifying
.RB \(oq "Xnest :1" \(cq
on the command line will be sufficient for most users.
For each server running on the workstation, the display number needs to be
incremented by one.
Thus, if you wish to start another
.BR Xnest ,
you will need to type
.RB \(oq "Xnest :2" \(cq
on the command line.
.PP
To run clients in the nested server, each client needs to be given the same
display number as the nested server.
For example,
.RB \(oq "xterm \-display :1" \(cq
will start up an
.B xterm
process in the first nested server
and
.RB \(oq "xterm \-display :2" \(cq
will start an
.B xterm
in the second nested server from the example above.
Additional clients can be started from these
.BR xterm s
in each nested server.
.SS "Xnest as a client"
.B Xnest
behaves and looks to the real server and other real clients as another real
client.
It is a rather demanding client, however, since almost any window or graphics
request from a nested client will result in a window or graphics request from
.B Xnest
to the real server.
Therefore, it is desirable that
.B Xnest
and the real server are on a local network, or even better, on the same machine.
.B Xnest
assumes that the real server supports the SHAPE extension.
There is no way to turn off this assumption dynamically.
.B Xnest
can be compiled without the SHAPE extension built in, in which case the real
server need not support it.
Dynamic SHAPE extension selection support may be considered in further
development of
.BR Xnest .
.PP
Since
.B Xnest
need not use the same default visual as the the real server, the top-level
window of the
.B Xnest
client always has its own color map.
This implies that other windows' colors will not be displayed properly while the
keyboard or pointer focus is in the
.B Xnest
window, unless the real server has support for more than one installed color map
at any time.
The color map associated with the top window of the
.B Xnest
client need not be the appropriate color map that the nested server wants
installed in the real server.
In the case that a nested client attempts to install a color map of a different
visual from the default visual of the nested server,
.B Xnest
will put the top window of this nested client and all other top windows of the
nested clients that use the same color map into the
.I WM_COLORMAP_WINDOWS
property of the top-level
.B Xnest
window on the real server.
Thus, it is important that the real window manager that manages the
.B Xnest
top-level window looks at the
.I WM_COLORMAP_WINDOWS
property rather than the color map associated with the top-level
.B Xnest
window.
Since most window managers don't yet appear to implement this convention
properly,
.B Xnest
can optionally do direct installation of color maps into the real server
bypassing the real window manager.
If the user chooses this option, it is usually necessary to temporarily disable
the real window manager since it will interfere with the
.B Xnest
scheme of color map installation.
.PP
Keyboard and pointer control procedures of the nested server change the keyboard
and pointer control parameters of the real server.
Therefore, after
.B Xnest
is started up, it will change the keyboard and pointer controls of the real
server to its own internal defaults.
.SS "Xnest as a server"
.B Xnest
as a server looks exactly like a real server to its own clients.
For the clients, there is no way of telling if they are running on a real or a
nested server.
.PP
As already mentioned,
.B Xnest
is a very user-friendly server when it comes to customization.
.B Xnest
will pick up a number of command-line arguments that can configure its default
visual class and depth, number of screens, etc.
.PP
The only apparent intricacy from the users' perspective about using
.B Xnest
as a server is the selection of fonts.
.B Xnest
manages fonts by loading them locally and then passing the font name to the real
server and asking it to load that font remotely.
This approach avoids the overload of sending the glyph bits across the network
for every text operation, although it is really a bug.
The consequence of this approach is that the user will have to worry about two
different font paths \(em a local one for the nested server and a remote one for
the real server \(em since
.B Xnest
does not propagate its font path to the real server.
The reason for this is because real and nested servers need not run on the same
file system which makes the two font paths mutually incompatible.
Thus, if there is a font in the local font path of the nested server, there is
no guarantee that this font exists in the remote font path of the real server.
The
.BR xlsfonts (1)
client, if run on the nested server, will list fonts in the local font path and,
if run on the real server, will list fonts in the remote font path.
Before a font can be successfully opened by the nested server, it has to exist
in local and remote font paths.
It is the users' responsibility to make sure that this is the case.
.SH "FUTURE DIRECTIONS"
Make dynamic the requirement for the SHAPE extension in the real server, rather
than having to recompile
.B Xnest
to turn this requirement on and off.
.PP
Perhaps there should be a command-line option to tell
.B Xnest
to inherit the keyboard and pointer control parameters from the real server
rather than imposing its own.
.PP
.B Xnest
should read a customization input file to provide even greater freedom and
simplicity in selecting the desired layout.
.PP
There is no support for backing store and save unders, but this should also be
considered.
.PP
.\" Is the following still true now that client-side font rendering is
.\" considered the way to go?
The proper implementation of fonts should be moved into the
.I os
layer.
.SH BUGS
Doesn't run well on servers supporting different visual depths.
.PP
Still crashes randomly.
.PP
Probably has some memory leaks.
.SH AUTHOR
Davor Matic, MIT X Consortium
.SH "SEE ALSO"
.BR Xserver (1),
.BR xdpyinfo (1),
.BR X (7)