path: root/driver/xscreensaver.man

.TH XScreenSaver 1 "6-Jan-2021 (6.00)" "X Version 11"
.SH NAME
xscreensaver - extensible screen saver and screen locking framework
.SH SYNOPSIS
.B xscreensaver
[\-\-display \fIhost:display.screen\fP] \
[\-\-verbose] \
[\-\-no\-splash] \
[\-\-log \fIfilename\fP]
.SH DESCRIPTION
XScreenSaver waits until the user is idle, and then runs graphics demos chosen
at random.  It can also lock your screen, and provides configuration and
control of display power management.

XScreenSaver is also available on macOS, iOS and Android.
.SH GETTING STARTED
XScreenSaver is a daemon that runs in the background.  You configure it
with the
.BR xscreensaver\-settings (1)
program.
.nf
.sp
	xscreensaver &
	xscreensaver-settings
.sp
.fi

.SH HOW IT WORKS
When it is time to activate the screensaver, a full-screen black window is
created that covers each monitor.  A sub-process is launched for each one
running a graphics demo, pointed at the appropriate window.  Because of this,
any program which can draw on a provided window can be used as a screensaver.
The various graphics demos are, in fact, just standalone programs that do
that.

When the user becomes active again, the screensaver windows are unmapped, and
the running subprocesses are killed.

The display modes are run at a low process priority, and spend most of their
time sleeping/idle by default, so they should not consume significant system
resources.

.SH COMMAND-LINE OPTIONS
.TP 8
.B \-\-display \fIhost:display.screen\fP
The X display to use.  For displays with multiple screens, XScreenSaver
will manage all screens on the display simultaneously.
.TP 8
.B \-\-verbose
Print diagnostics to stderr.
.TP 8
.B \-\-log \fIfilename\fP
Append all diagnostic output to the given file.  This also 
implies \fI\-\-verbose\fP.  Use this when reporting bugs.
.TP 8
.B \-\-no\-splash
Don't display the splash screen at startup.

.SH POWER MANAGEMENT
The
.BR xscreensaver\-settings (1)
program is where you configure if and when your monitor should power off.
It saves the settings in your \fI~/.xscreensaver\fP file.

If the power management section is grayed out in the
.BR xscreensaver\-settings (1)
window,  then that means that your X server does not support
the XDPMS extension, and so control over the monitor's power state
is not available.

When the monitor is powered down, the display hacks are stopped
(though it may take a minute or two for XScreenSaver to notice).

Note: if you use
.BR xset (1)
to change the power management settings, XScreenSaver will override those
changes.  Whatever is in the \fI~/.xscreensaver\fP file takes precedence.

.SH LAPTOP LIDS
If your system has
.BR systemd (1)
221 or newer, or
.BR elogind (8),
then closing the lid of your laptop will cause the screen to lock immediately.

If not, then the screen might not lock until a few seconds \fIafter\fP you
re-open the lid.  Which is less than ideal.  So if you don't 
use \fIsystemd\fP, you might want to get in the habit of
doing \fIxscreensaver-command --lock\fP before closing the lid.

.SH PLAYING VIDEOS
Likewise, if you have
.BR systemd (1)
221 or newer, or
.BR elogind (8),
then all of the popular video players and web browsers will
prevent XScreenSaver from blanking the screen while video is playing.

Both of these features require that
.BR xscreensaver\-systemd (MANSUFFIX)
be able connect to the systemd bus.  Parts of KDE and GNOME may need to be
disabled first for that to work; see below.

.SH INSTALLATION
Each desktop environment has its own system for launching long-running
daemons like XScreenSaver, and since many of them come bundled with
their own (buggy, insecure, inferior) screen-locking frameworks, it is
also necessary to disable those other frameworks before XScreenSaver
can work.

.SS INSTALLING XSCREENSAVER ON GNOME OR UNITY
For many years, GNOME shipped XScreenSaver as-is, and everything just worked.
In 2005, however, they decided to needlessly re-invent the wheel and ship
their own replacement for the \fIxscreensaver\fP daemon called
.BR gnome-screensaver (1)
rather than improving XScreenSaver and contributing their changes back.  As a
result, the \fIgnome-screensaver\fP program is insecure, bug-ridden, and
missing many features of XScreenSaver.  In fact, in 2011 it lost the ability
to run display modes at all.

In 2012 some distros forked and renamed it as both
.BR mate-screensaver (1)
and
.BR cinnamon-screensaver (1),
which seem to be basically the same.

To replace gnome-screensaver with XScreenSaver:
.RS 4
.TP 3
\fB1: Fully uninstall the other screen saver packages:\fP
.nf
.sp
	sudo apt-get remove gnome-screensaver
	sudo apt-get remove mate-screensaver
	sudo apt-get remove cinnamon-screensaver
or
	sudo rpm -e gnome-screensaver
	sudo rpm -e mate-screensaver
	sudo rpm -e cinnamon-screensaver
.sp
.fi
Be careful that it doesn't try to uninstall all of GNOME.

.TP 3
\fB2: Launch XScreenSaver at login.\fP

Select "\fIStartup Applications\fP" from the menu (or manually
launch "\fIgnome-session-properties\fP") and add "\fIxscreensaver\fP".

Do this as your normal user account, not as root.
(This should go without saying, because you should never, ever, ever
be logged in to the graphical desktop as user "root".)
.TP 3
\fB3: Make GNOME's "Lock Screen" use XScreenSaver.\fP
.nf
.sp
	sudo ln -sf /usr/bin/xscreensaver-command \\
            /usr/bin/gnome-screensaver-command
.sp
.fi
That doesn't work under Unity, though.  Apparently it has its own
built-in screen locker which is not gnome-screensaver, and cannot be
removed, and yet still manages to be bug-addled and insecure. 
Keep reinventing that wheel, guys!  (If you have figured out how to
replace Unity's locking "feature" with XScreenSaver, let me know.)

.TP 3
\fB4: Turn off Unity's built-in blanking.\fP

Open "\fISystem Settings / Brightness & Lock\fP";
.br
Un-check "\fIStart Automatically\fP";
.br
Set \fI"Turn screen off when inactive for"\fP to \fI"Never".\fP
.br
Or possibly that has been randomly renamed again:
.br
Set "\fISettings / Power / Power Settings\fP" to \fI"Never".\fP
.TP 3
\fB5: Stop GNOME from blocking XScreenSaver's "systemd" integration:\fP
.nf
.sp
	sudo systemctl \-\-user mask gsd\-screensaver\-proxy.service
.sp
.fi
Without the above, video players will not be able to tell XScreenSaver
not to blank the screen while videos are playing, and the screen will not
auto-lock when you close your laptop's lid.

After running that command, reboot.  Yes, you have to reboot; it won't let
you simply stop the service.  Logging out won't do it either.

.SS INSTALLING XSCREENSAVER ON KDE
Like GNOME, KDE also decided to invent their own screen saver framework
from scratch instead of simply using XScreenSaver.  To replace the KDE
screen saver with XScreenSaver, do the following:
.RS 4
.TP 3
\fB1: Turn off KDE's screen saver.\fP
Open the "\fIControl Center\fP" and
select the "\fIAppearance & Themes / Screensaver\fP" page.
Un-check "\fIStart Automatically\fP".

Or possibly:
Open "\fISystem Settings\fP" and
select "\fIScreen Locking\fP".
Un-check "\fILock Screen Automatically\fP".
.TP 3
\fB2: Find your Autostart directory.\fP
Open the "\fISystem Administration / Paths\fP" page,
and see what your "Autostart path" is set to: it will
probably be something like \fI~/.kde/Autostart/\fP
or \fI~/.config/autostart/\fP

If that doesn't work, then try this:

Open "\fISystem Settings / Startup/Shutdown / Autostart\fP", and then
add "\fI/usr/bin/xscreensaver\fP".

If you are lucky, that will create a \fI"xscreensaver.desktop"\fP file 
for you in \fI~/.config/autostart/\fP or \fI~/.kde/Autostart/\fP.
.TP 3
\fB3: Make XScreenSaver be an Autostart program.\fP
If it does not already exist, create a file in your autostart directory 
called \fIxscreensaver.desktop\fP that contains the following six lines:
.nf
.sp
	[Desktop Entry]
	Exec=xscreensaver
	Name=XScreenSaver
	Type=Application
	StartupNotify=false
	X-KDE-StartupNotify=false
.sp
.fi
.TP 3
\fB4: Make the various "lock session" buttons call XScreenSaver.\fP
The file you want to replace next has moved around over the years. It
might be called \fI/usr/libexec/kde4/kscreenlocker\fP,
or it might be called "\fIkdesktop_lock\fP" or "\fIkrunner_lock\fP"
or "\fIkscreenlocker_greet\fP", and
it might be in \fI/usr/lib/kde4/libexec/\fP
or in \fI/usr/kde/3.5/bin/\fP or even in \fI/usr/bin/\fP,
depending on the distro and phase of the moon.  Replace the contents
of that file with these two lines:
.nf
.sp
	#!/bin/sh
	xscreensaver-command \-\-lock
.sp
.fi
Make sure the file is executable (chmod a+x).
.TP 3
\fB5: Stop KDE from blocking XScreenSaver's "systemd" integration:\fP
You must arrange for KDE's
.BR ksmserver (1)
daemon to be launched with the command line switch \fI\-\-no\-lockscreen\fP.

One way to accomplish that is to edit the
.BR startkde (1)
script in \fI/usr/bin/\fP by hand, then log out and log back in.  Another
way would be to wrap the \fIksmserver\fP program:
.nf
.sp
	mv /usr/bin/ksmserver /usr/bin/ksmserver-orig
.sp
.fi
and replace \fI/usr/bin/ksmserver\fP with:
.nf
.sp
	#!/bin/sh
	ksmserver-orig \-\-no\-lockscreen
.sp
.fi
Either change will, of course, get blown away the next time your system
upgrades KDE.

Instead of being in \fI/usr/bin/\fP, the \fIksmserver\fP program might be
in \fI/usr/lib/\fP or \fIusr/lib*/libexec/\fP or \fIusr/lib/*/libexec/\fP
or somewhere else, depending on your distro.

But without this, video players will not be able to tell XScreenSaver not to
blank the screen while videos are playing, and the screen will not auto-lock
when you close your laptop's lid.

It seems that KDE 5.17 replaced \fIstartkde\fP with \fIstartplasma-x11\fP,
and I don't know how to change how \fIthat\fP launches \fIksmserver\fP.
Let me know if you figure it out.

.SS LAUNCHING XSCREENSAVER FROM SYSTEMD
If the above didn't do it, and your system has
.BR systemd (1),
maybe this is how it works:
.RS 4
.TP 3
\fB1: Create a service.\fP
Create the file \fI~/.config/systemd/user/xscreensaver.service\fP
containing:
.nf
.sp
	[Unit]
	Description=XScreenSaver
	[Service]
	ExecStart=/usr/bin/xscreensaver
	Restart=on-failure
	[Install]
	WantedBy=default.target
.sp
.fi
.TP 3
\fB2. Enable it.\fP
.nf
.sp
	systemctl \-\-user enable xscreensaver
.sp
.fi
.RE
Then restart X11.

.SS LAUNCHING XSCREENAVER FROM UPSTART
If your system has
.BR upstart (7)
instead of
.BR systemd (1),
maybe this will work: launch the \fI"Startup Applications"\fP applet,
click \fI"Add"\fP, enter these lines, then restart X11:
.nf
.sp
	Name: XScreenSaver
	Command: xscreensaver
	Comment: XScreenSaver
.sp
.fi

.SS LAUNCHING XSCREENSAVER FROM GDM
You can run \fIxscreensaver\fP from your 
.BR gdm (1)
session, so that the screensaver will run even when nobody is logged 
in on the console.  To do this, run
.BR gdmconfig (1).

On the \fIGeneral\fP page set the \fILocal Greeter\fP to
\fIStandard Greeter\fP.

On the \fIBackground\fP page, type the
command \fB"xscreensaver \-\-nosplash"\fP into the \fIBackground Program\fP
field.  That will cause gdm to run XScreenSaver while nobody is logged
in, and kill it as soon as someone does log in.  (The user will then
be responsible for starting XScreenSaver on their own, if they want.)

If that doesn't work, you can edit the config file directly. Edit
\fI/etc/X11/gdm/gdm.conf\fP to include:
.nf
.sp
	Greeter=/usr/bin/gdmlogin
	BackgroundProgram=xscreensaver \-\-nosplash
	RunBackgroundProgramAlways=true
.sp
.fi
In this situation, the \fIxscreensaver\fP process will probably be running
as user \fIgdm\fP instead of as \fIroot\fP.  You can configure the settings
for this nobody-logged-in state (timeouts, DPMS, etc.) by editing
the \fI~gdm/.xscreensaver\fP file.

It is safe to run \fIxscreensaver\fP as root (as \fIxdm\fP or \fIgdm\fP may do).
If run as root, \fIxscreensaver\fP changes its effective user and group ids 
to something safe (like \fI"nobody"\fP) before connecting to the X server
or launching user-specified programs.

An unfortunate side effect of this (important) security precaution is that
it may conflict with cookie-based authentication.

If you get "connection refused" errors when running \fIxscreensaver\fP
from \fIgdm\fP, then this probably means that you have
.BR xauth (1)
or some other security mechanism turned on.  For information on the
X server's access control mechanisms, see the man pages for
.BR X (1),
.BR Xsecurity (1),
.BR xauth (1),
and
.BR xhost (1).

.SS LAPTOP LIDS WITHOUT SYSTEMD
BSD systems or other systems without
.BR systemd (1)
or
.BR elogind (8)
might have luck by adding \fIxscreensaver\-command \-\-suspend\fP to
some appropriate spot in \fI/etc/acpi/events/anything\fP or in
\fI/etc/acpi/handler.sh\fP, if those files exist.

.SH SECURITY CONCERNS
XScreenSaver has a decades-long track record of securely locking your screen.
However, there are many things that can go wrong.  X11 is a very old system,
and has a number of design flaws that make it susceptible to foot-shooting.

.SS MAGIC BACKDOOR KEYSTROKES
The XFree86 and Xorg X servers, as well as the Linux kernel, both trap
certain magic keystrokes before X11 client programs ever see them.
If you care about keeping your screen locked, this is a big problem.

.TP 3
.B Ctrl+Alt+Backspace
This keystroke kills the X server, and on some systems, leaves you at
a text console.  If the user launched X11 manually, that text console
will still be logged in.  To disable this keystroke globally and
permanently, you need to set the \fBDontZap\fP flag in your
\fIxorg.conf\fP or \fIXF86Config\fP or \fIXF86Config-4\fP file,
depending which is in use on your system.  See
.BR XF86Config (5)
for details.

.TP 3
.B Ctrl-Alt-F1, Ctrl-Alt-F2, etc.
These keystrokes will switch to a different virtual console, while
leaving the console that X11 is running on locked.  If you left a
shell logged in on another virtual console, it is unprotected.  So
don't leave yourself logged in on other consoles.  You can disable VT
switching globally and permanently by setting \fBDontVTSwitch\fP in
your \fIxorg.conf\fP, but that might make your system harder to use,
since VT switching is an actual useful feature.

There is no way to disable VT switching only when the screen is
locked.  It's all or nothing.

.TP 3
.B Ctrl-Alt-KP_Multiply
This keystroke kills any X11 app that holds a lock, so typing this
will kill XScreenSaver and unlock the screen.  You can disable it by
turning off \fBAllowClosedownGrabs\fP in \fIxorg.conf\fP.

.TP 3
.B Alt-SysRq-F
This is the Linux kernel "OOM-killer" keystroke.  It shoots down random
long-running programs of its choosing, and so might target and kill
XScreenSaver.  You can disable this keystroke globally with:
.nf
.sp
	echo 176 > /proc/sys/kernel/sysrq
.sp
.fi
There's little that I can do to make the screen locker be secure so long
as the kernel and X11 developers are \fIactively\fP working against
security like this.  The strength of the lock on your front door
doesn't matter much so long as someone else in the house insists on
leaving a key under the welcome mat.
.SS THE OOM-KILLER
Even if you have disabled the \fBAlt-SysRq-F\fP OOM-killer keystroke, the
OOM-killer might still decide to assassinate XScreenSaver at random, which
will unlock your screen.  If the
.BR xscreensaver\-auth (MANSUFFIX)
program is installed setuid, it attempts to tell the OOM-killer to leave
the XScreenSaver daemon alone, but that may or may not work.

You would think that the OOM-killer would pick the process using the most
memory, but most of the time it seems to pick the process that would be most
comically inconvenient, such as your screen locker, or
.BR crond (8).
You can disable the OOM-killer entirely with:
.nf
.sp
	echo 2 > /proc/sys/vm/overcommit_memory
	echo vm.overcommit_memory = 2 >> /etc/sysctl.conf
.sp
.fi

.SS X SERVER ACCESS IS GAME OVER
X11's security model is all-or-nothing.  If a program can connect to your X
server at all, either locally or over the network, it can log all of your
keystrokes, simulate keystrokes, launch arbitrary programs, and change the
settings of other programs.  Assume that anything that can connect to your X
server can execute arbitrary code as the logged-in user.  See
.BR Xsecurity (1)
and 
.BR xauth (1).

.SS PAM PASSWORDS
If your system uses PAM (Pluggable Authentication Modules), then PAM must be
configured for XScreenSaver.  If it is not, then you \fImight\fP be in a
situation where you can't unlock.  Probably the file you need 
is \fI/etc/pam.d/xscreensaver\fP.

.SS DON'T LOG IN AS ROOT
In order for it to be safe for XScreenSaver to be launched by \fIxdm\fP,
certain precautions had to be taken, among them that XScreenSaver never
runs as \fIroot\fP.  In particular, if it is launched as root (as \fIxdm\fP
is likely to do), XScreenSaver will disavow its privileges, and switch 
itself to a safe user id (such as \fInobody\fP).

An implication of this is that if you log in as \fIroot\fP on the console, 
XScreenSaver will refuse to lock the screen (because it can't tell
the difference between \fIroot\fP being logged in on the console, and a
normal user being logged in on the console but XScreenSaver having been 
launched by the
.BR xdm (1)
.I Xsetup
file).

Proper Unix hygiene dictates that you should log in as yourself, and
.BR sudo (1)
to \fIroot\fP as necessary.  People who spend their day logged in
as \fIroot\fP are just begging for disaster.

.SH MULTI-USER OR SITE-WIDE CONFIGURATION
For a single user, the proper way to configure XScreenSaver is to simply
run the
.BR xscreensaver\-settings (1)
program, and change the settings through the GUI.  The rest of this manual
describes lower-level ways of changing settings.  You shouldn't need to
know any of the stuff described below unless you are trying to do something
complicated.

Options to XScreenSaver are stored in one of two places: in a file
called \fI.xscreensaver\fP  in your home directory; or in the X resource
database.  If the \fI.xscreensaver\fP file exists, it overrides any settings
in the resource database.  

The syntax of the \fI.xscreensaver\fP file is similar to that of
the \fI.Xdefaults\fP file; for example, to set the \fItimeout\fP parameter
n the \fI.xscreensaver\fP file, you would write the following:
.nf
.sp
	timeout: 5
.sp
.fi
whereas, in the \fI.Xdefaults\fP file, you would write
.nf
.sp
	xscreensaver.timeout: 5
.sp
.fi
If you change a setting in the \fI.xscreensaver\fP file while XScreenSaver
is already running, it will notice this, and reload the file as needed.

If you change a setting in your X resource database, or if you want
XScreenSaver to notice your changes immediately instead of the next time it
wakes up, then you will need to reload your \fI.Xdefaults\fP file, and then
tell the running \fIxscreensaver\fP process to restart itself, like so:
.nf
.sp
	xrdb < ~/.Xdefaults
	xscreensaver-command \-\-restart
.sp
.fi
If you want to set the system-wide defaults, then make your edits to
the XScreenSaver app-defaults file, which should have been installed
when XScreenSaver itself was installed.  The app-defaults file will
usually be named /etc/X11/app-defaults/XScreenSaver, but different
systems might keep it in a different place.

When settings are changed in the Preferences dialog box, those settings are
written to the \fI.xscreensaver\fP file.  The \fI.Xdefaults\fP file and the
app-defaults file will never be written by XScreenSaver itself.

.SH X RESOURCES
These are the X resources use by XScreenSaver program.  You probably won't
need to change these manually: that's what the
.BR xscreensaver\-settings (1)
program is for.

.TP 8
.B timeout\fP (class \fBTime\fP)
The screensaver will activate (blank the screen) after the keyboard and
mouse have been idle for this many minutes.  Default 10 minutes.

.TP 8
.B cycle\fP (class \fBTime\fP)
After the screensaver has been running for this many minutes, the currently
running graphics-hack sub-process will be killed (with \fBSIGTERM\fP), and a
new one started.  If this is 0, then the graphics hack will never be changed:
only one demo will run until the screensaver is deactivated by user activity.
Default 10 minutes.

If there are multiple screens, the savers are staggered slightly so
that while they all change every \fIcycle\fP minutes, they don't all
change at the same time.

.TP 8
.B lock\fP (class \fBBoolean\fP)
Enable locking: before the screensaver will turn off, it will require you 
to type the password of the logged-in user.

.TP 8
.B lockTimeout\fP (class \fBTime\fP)
If locking is enabled, this controls the length of the "grace period"
between when the screensaver activates, and when the screen becomes locked.
For example, if this is 5, and \fItimeout\fP is 10, then after 10 minutes,
the screen would blank.  If there was user activity at 12 minutes, no password
would be required to un-blank the screen.  But, if there was user activity
at 15 minutes or later (that is, \fIlockTimeout\fP minutes after 
activation) then a password would be required.  The default is 0, meaning
that if locking is enabled, then a password will be required as soon as the 
screen blanks.

.TP 8
.B passwdTimeout\fP (class \fBTime\fP)
If the screen is locked, then this is how many seconds the password dialog box
should be left on the screen before giving up (default 30 seconds).  A few
seconds are added each time you type a character.

.TP 8
.B dpmsEnabled\fP (class \fBBoolean\fP)
Whether power management is enabled.

.TP 8
.B dpmsStandby\fP (class \fBTime\fP)
If power management is enabled, how long until the monitor goes solid black.

.TP 8
.B dpmsSuspend\fP (class \fBTime\fP)
If power management is enabled, how long until the monitor goes into
power-saving mode.

.TP 8
.B dpmsOff\fP (class \fBTime\fP)
If power management is enabled, how long until the monitor powers down
completely.  Note that these settings will have no effect unless both
the X server and the display hardware support power management; not 
all do.  See the \fIPower Management\fP section, below, for more 
information.

.TP 8
.B dpmsQuickOff\fP (class \fBBoolean\fP)
If \fImode\fP is \fIblank\fP and this is true, then the screen will be
powered down immediately upon blanking, regardless of other
power-management settings.

.TP 8
.B verbose\fP (class \fBBoolean\fP)
Whether to print diagnostics.  Default false.

.TP 8
.B splash\fP (class \fBBoolean\fP)
Whether to display a splash screen at startup.  Default true.

.TP 8
.B splashDuration\fP (class \fBTime\fP)
How long the splash screen should remain visible; default 5 seconds.

.TP 8
.B helpURL\fP (class \fBURL\fP)
The splash screen has a \fIHelp\fP button on it.  When you press it, it will
display the web page indicated here in your web browser.

.TP 8
.B loadURL\fP (class \fBLoadURL\fP)
This is the shell command used to load a URL into your web browser.
The default setting will load it into Mozilla/Netscape if it is already
running, otherwise, will launch a new browser looking at the \fIhelpURL\fP.

.TP 8
.B demoCommand\fP (class \fBDemoCommand\fP)
This is the shell command run when the \fIDemo\fP button on the splash window
is pressed.  It defaults to
.BR xscreensaver\-settings (1).

.TP 8
.B newLoginCommand\fP (class \fBNewLoginCommand\fP)
If set, this is the shell command that is run when the "New Login" button
is pressed on the unlock dialog box, in order to create a new desktop
session without logging out the user who has locked the screen.
Typically this will be some variant of
.BR gdmflexiserver (1),
.BR kdmctl (1),
.BR lxdm (1)
or
.BR dm-tool (1).

.TP 8
.B nice\fP (class \fBNice\fP)
The sub-processes launched by XScreenSaver will be "niced" to this level, so
that they are given lower priority than other processes on the system, and
don't increase the load unnecessarily.  The default is 10.  (Higher numbers
mean lower priority; see
.BR nice (1)
for details.)

.TP 8
.B fade\fP (class \fBBoolean\fP)
If this is true, then when the screensaver activates, the current contents
of the screen will fade to black instead of simply winking out.
Default: true.  

.TP 8
.B unfade\fP (class \fBBoolean\fP)
If this is true, then when the screensaver deactivates, the original contents
of the screen will fade in from black instead of appearing immediately.  This
is only done if \fIfade\fP is true as well.  Default: true.

.TP 8
.B fadeSeconds\fP (class \fBTime\fP)
If \fIfade\fP is true, this is how long the fade will be in 
seconds. Default 3 seconds.

.TP 8
.B ignoreUninstalledPrograms\fP (class \fBBoolean\fP)
There may be programs in the list that are not installed on the system,
yet are marked as "enabled".  If this preference is true, then such 
programs will simply be ignored.  If false, then a warning will be printed
if an attempt is made to run the nonexistent program.  Also, the
.BR xscreensaver\-settings (1)
program will suppress the non-existent programs from the list if this
is true.  Default: false.

.TP 8
.B authWarningSlack\fP (class \fBInteger\fP)
After you successfully unlock the screen, a dialog may pop up informing
you of previous failed login attempts.  If all of those login attemps
were within this amount of time, they are ignored.  The assumption
is that incorrect passwords entered within a few seconds of a correct
one are user error, rather than hostile action.  Default 20 seconds.

.TP 8
.B mode\fP (class \fBMode\fP)
Controls the screen-saving behavior.  Valid values are:
.RS 8

.TP 8
.B random
When blanking the screen, select a random display mode from among those
that are enabled and applicable.  This is the default.

.TP 8
.B random-same
Like \fIrandom\fP, but if there are multiple screens, each screen
will run the \fIsame\fP random display mode, instead of each screen
running a different one.

.TP 8
.B one
When blanking the screen, only ever use one particular display mode (the
one indicated by the \fIselected\fP setting).

.TP 8
.B blank
When blanking the screen, just go black: don't run any graphics hacks.

.TP 8
.B off
Don't ever blank the screen, and don't ever allow the monitor to power down.
.RE

.TP 8
.B selected\fP (class \fBInteger\fP)
When \fImode\fP is set to \fIone\fP, this is the one, indicated by its
index in the \fIprograms\fP list.  You're crazy if you count them and
set this number by hand: let
.BR xscreensaver\-settings (1)
do it for you!

.TP 8
.B programs\fP (class \fBPrograms\fP)
The graphics hacks which XScreenSaver runs when the user is idle.
The value of this resource is a multi-line string, one \fIsh\fP-syntax
command per line.  Each line must contain exactly one command: no
semicolons, no ampersands.

When the screensaver starts up, one of these is selected (according to
the \fBmode\fP setting), and run.  After the \fIcycle\fP period
expires, it is killed, and another is selected and run.

If a line begins with a dash (-) then that particular program is
disabled: it won't be selected at random (though you can still select
it explicitly using the
.BR xscreensaver\-settings (1)
program).

If all programs are disabled, then the screen will just be made blank,
as when \fImode\fP is set to \fIblank\fP.

To disable a program, you must mark it as disabled with a dash instead
of removing it from the list.  This is because the system-wide (app-defaults)
and per-user (.xscreensaver) settings are merged together, and if a user
just \fIdeletes\fP an entry from their programs list, but that entry still
exists in the system-wide list, then it will come back.  However, if the
user \fIdisables\fP it, then their setting takes precedence.

If the display has multiple screens, then a different program will be run
for each screen.  (All screens are blanked and unblanked simultaneously.)

Note that you must escape the newlines; here is an example of how you
might set this in your \fI~/.xscreensaver\fP file:
.nf
.sp
	programs:  \\
	       qix -root                          \\n\\
	       ico -r -faces -sleep 1 -obj ico    \\n\\
	       xdaliclock -builtin2 -root         \\n\\
	       xv -root -rmode 5 image.gif -quit  \\n
.sp
.fi
.RS 8
Make sure your \fB$PATH\fP environment variable is set up correctly
\fIbefore\fP XScreenSaver is launched, or it won't be able to find the
programs listed in the \fIprograms\fP resource.

To use a program as a screensaver, it must be able to render onto
the window provided to it in the \fB$XSCREENSAVER_WINDOW\fP environment
variable.  If it creates and maps its own window instead, it won't work.
It must render onto the provided window.

.B Visuals:

Because XScreenSaver was created back when dinosaurs roamed the earth,
it still contains support for some things you've probably never seen,
such as 1-bit monochrome monitors, grayscale monitors, and monitors
capable of displaying only 8-bit colormapped images.

If there are some programs that you want to run only when using a color
display, and others that you want to run only when using a monochrome
display, you can specify that like this:
.nf
.sp
	mono:   mono-program  -root        \\n\\
	color:  color-program -root        \\n\\
.sp
.fi
More generally, you can specify the kind of visual that should be used for
the window on which the program will be drawing.  For example, if one 
program works best if it has a colormap, but another works best if it has
a 24-bit visual, both can be accommodated:
.nf
.sp
	PseudoColor: cmap-program  -root   \\n\\
	TrueColor:   24bit-program -root   \\n\\
.sp
.fi
In addition to the symbolic visual names described above (in the discussion
of the \fIvisualID\fP resource) one other visual name is supported in
the \fIprograms\fP list:
.RS 1
.TP 4
.B default-n
This is like \fBdefault\fP, but also requests the use of the default colormap,
instead of a private colormap.

.RE
If you specify a particular visual for a program, and that visual does not
exist on the screen, then that program will not be chosen to run.  This
means that on displays with multiple screens of different depths, you can
arrange for appropriate hacks to be run on each.  For example, if one screen
is color and the other is monochrome, hacks that look good in mono can be 
run on one, and hacks that only look good in color will show up on the other.
.RE

.TP 8
.B visualID\fP (class \fBVisualID\fP)
This is an historical artifact left over from when 8-bit
displays were still common.  You should probably ignore this.

Specify which X visual to use by default.  (Note carefully that this resource
is called \fBvisualID\fP, not merely \fBvisual\fP; if you set the \fBvisual\fP
resource instead, things will malfunction in obscure ways for obscure reasons.)

Valid values for the \fBVisualID\fP resource are:
.RS 8
.TP 8
.B default
Use the screen's default visual (the visual of the root window).  
This is the default.
.TP 8
.B best
Use the visual which supports the most colors.  Note, however, that the
visual with the most colors might be a TrueColor visual, which does not
support colormap animation.  Some programs have more interesting behavior
when run on PseudoColor visuals than on TrueColor.
.TP 8
.B mono
Use a monochrome visual, if there is one.
.TP 8
.B gray
Use a grayscale or staticgray visual, if there is one and it has more than
one plane (that is, it's not monochrome).
.TP 8
.B color
Use the best of the color visuals, if there are any.
.TP 8
.B GL
Use the visual that is best for OpenGL programs.  (OpenGL programs have
somewhat different requirements than other X programs.)
.TP 8
.I class
where \fIclass\fP is one of \fBStaticGray\fP, \fBStaticColor\fP, 
\fBTrueColor\fP, \fBGrayScale\fP, \fBPseudoColor\fP, or \fBDirectColor\fP.
Selects the deepest visual of the given class.
.TP 8
.I N
where \fInumber\fP (decimal or hex) is interpreted as a visual id number, 
as reported by the
.BR xdpyinfo (1)
program; in this way you can have finer control over exactly which visual
gets used, for example, to select a shallower one than would otherwise
have been chosen.

.RE
.RS 8
Note that this option specifies only the \fIdefault\fP visual that will
be used: the visual used may be overridden on a program-by-program basis.
See the description of the \fBprograms\fP resource, above.
.RE

.TP 8
.B installColormap\fP (class \fBBoolean\fP)
This is an historical artifact left over from when 8-bit displays were still
common.  On PseudoColor (8-bit) displays, install a private colormap while the
screensaver is active, so that the graphics hacks can get as many colors as
possible.  This is the default.  (This only applies when the screen's default
visual is being used, since non-default visuals get their own colormaps
automatically.)  This can also be overridden on a per-hack basis: see the
discussion of the \fBdefault\-n\fP name in the section about the
\fBprograms\fP resource.

This does nothing if you have a TrueColor (16-bit or deeper) display.
(Which, in this century, you do.)

.TP 8
.B pointerHysteresis\fP (class \fBInteger\fP)
If the mouse moves less than this-many pixels in a second, ignore it
(do not consider that to be "activity").  This is so that the screen
doesn't un-blank (or fail to blank) just because you bumped the desk.
Default: 10 pixels.

.SH BUGS
https://www.jwz.org/xscreensaver/bugs.html explains how to write the most
useful bug reports.  If you find a bug, please let me know!

.SH ENVIRONMENT
.PP
.TP 8
.B DISPLAY
to get the default host and display number, and to inform the sub-programs
of the screen on which to draw.
.TP 8
.B XSCREENSAVER_WINDOW
Passed to sub-programs to indicate the ID of the window on which they
should draw.  This is necessary on Xinerama/RANDR systems where
multiple physical monitors share a single X11 "Screen".
.TP 8
.B PATH
to find the sub-programs to run, including the display modes.
.TP 8
.B HOME
for the directory in which to read the \fI.xscreensaver\fP file.
.TP 8
.B XENVIRONMENT
to get the name of a resource file that overrides the global resources
stored in the RESOURCE_MANAGER property.
.SH UPGRADES
The latest version of XScreenSaver, an online version of this manual,
and a FAQ can always be found at https://www.jwz.org/xscreensaver/
.SH SEE ALSO
.BR X (1),
.BR Xsecurity (1),
.BR xauth (1),
.BR xdm (1),
.BR gdm (1),
.BR xhost (1),
.BR systemd (1),
.BR elogind (8),
.BR xscreensaver\-settings (1),
.BR xscreensaver\-command (1),
.BR xscreensaver\-systemd (MANSUFFIX),
.BR xscreensaver\-gl\-helper (MANSUFFIX),
.BR xscreensaver\-getimage (MANSUFFIX),
.BR xscreensaver\-text (MANSUFFIX).
.SH COPYRIGHT
Copyright \(co 1991-2021 by Jamie Zawinski.
Permission to use, copy, modify, distribute, and sell this software
and its documentation for any purpose is hereby granted without fee,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation.  No representations are made about the
suitability of this software for any purpose.  It is provided "as is"
without express or implied warranty.
.SH AUTHOR
Jamie Zawinski <jwz@jwz.org>.  Written in late 1991; version 1.0 posted
to comp.sources.x on 17-Aug-1992.

Please let me know if you find any bugs or make any improvements.

And a huge thank you to the hundreds of people who have contributed, in
large ways and small, to the XScreenSaver collection over the past
three decades!