XScreenSaver Manual


NAME
xscreensaver - extensible screen saver and screen locking framework

SYNOPSIS
xscreensaver [--display host:display.screen] [--verbose] [--no-splash] [--log filename]

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.

GETTING STARTED
XScreenSaver is a daemon that runs in the background. You configure it with the xscreensaver-settings (1) program.

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.

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

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

If the power management section is grayed out in the 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 xset (1) to change the power management settings, XScreenSaver will override those changes. Whatever is in the ~/.xscreensaver file takes precedence.

LAPTOP LIDS
If your system has systemd (1) 221 or newer, or 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 after you re-open the lid. Which is less than ideal. So if you don't use systemd, you might want to get in the habit of doing xscreensaver-command --lock before closing the lid.

PLAYING VIDEOS
Likewise, if you have systemd (1) 221 or newer, or 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 xscreensaver-systemd(6) be able connect to the systemd bus. Parts of KDE and GNOME may need to be disabled first for that to work; see below.

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.

    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 xscreensaver daemon called gnome-screensaver (1) rather than improving XScreenSaver and contributing their changes back. As a result, the gnome-screensaver 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 mate-screensaver (1) and cinnamon-screensaver (1), which seem to be basically the same.

To replace gnome-screensaver with XScreenSaver:

1: Fully uninstall the other screen saver packages:
 
    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
Be careful that it doesn't try to uninstall all of GNOME.

2: Launch XScreenSaver at login.
 

Select "Startup Applications" from the menu (or manually launch "gnome-session-properties") and add "xscreensaver". Do this as your normal user account, not as root.

3: Make GNOME's "Lock Screen" use XScreenSaver.
 
    sudo ln -sf /usr/bin/xscreensaver-command \
                /usr/bin/gnome-screensaver-command
4: Turn off Unity's built-in blanking.
 

Open "System Settings / Brightness & Lock";
Un-check "Start Automatically";
Set "Turn screen off when inactive for" to "Never".

Or possibly that has been randomly renamed again:
Set "Settings / Power / Power Settings" to "Never".

5: Stop GNOME from blocking XScreenSaver's "systemd" integration:
 
    sudo systemctl --user mask gsd-screensaver-proxy.service
    sudo systemctl --user mask \
      org.gnome.SettingsDaemon.ScreensaverProxy.service
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 those commands, reboot. Yes, you have to reboot; it won't let you simply stop the service. Logging out won't do it either.

    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:
1: Turn off KDE's screen saver.
  Open the "Control Center" and select the "Appearance & Themes / Screensaver" page. Un-check "Start Automatically".

Or possibly: Open "System Settings" and select "Screen Locking". Un-check "Lock Screen Automatically".

2: Find your Autostart directory.
  Open the "System Administration / Paths" page, and see what your "Autostart path" is set to: it will probably be something like ~/.kde/Autostart/ or ~/.config/autostart/

If that doesn't work, then try this:

Open "System Settings / Startup/Shutdown / Autostart", and then add "/usr/bin/xscreensaver".

If you are lucky, that will create an "xscreensaver.desktop" file for you in ~/.config/autostart/ or ~/.kde/Autostart/.

3: Make XScreenSaver be an Autostart program.
  If it does not already exist, create a file in your autostart directory called xscreensaver.desktop that contains the following six lines:
    [Desktop Entry]
    Exec=xscreensaver
    Name=XScreenSaver
    Type=Application
    StartupNotify=false
    X-KDE-StartupNotify=false
4: Make the various "lock session" buttons call XScreenSaver.
  The file you want to replace next has moved around over the years. It might be called /usr/libexec/kde4/kscreenlocker, or it might be called "kdesktop_lock" or "krunner_lock" or "kscreenlocker_greet", and it might be in /usr/lib/kde4/libexec/ or in /usr/kde/3.5/bin/ or even in /usr/bin/, depending on the distro and phase of the moon. Replace the contents of that file with these two lines:
    #!/bin/sh
    xscreensaver-command --lock
Make sure the file is executable (chmod a+x).

This change will probably get blown away the next time your system upgrades KDE.

5: Stop KDE from blocking XScreenSaver's "systemd" integration:
  You must arrange for KDE's ksmserver (1) daemon to be launched with the command line option --no-lockscreen.

Under KDE 5.00 through 5.16, you can accomplish that by editing the startkde (1) script in /usr/bin/ by hand, then logging out and back in again.

Under KDE 5.17 through 5.20, you must wrap ksmserver (1) instead:

    mv /usr/bin/ksmserver /usr/bin/ksmserver-orig
and replace /usr/bin/ksmserver with:
    #!/bin/sh
    ksmserver-orig --no-lockscreen
Either change will, of course, get blown away the next time your system upgrades KDE.

Instead of being in /usr/bin/, the ksmserver program might be in /usr/lib/ or /usr/lib*/libexec/ or usr/lib/*/libexec/ or somewhere else, depending on your distro.

Under KDE 5.21+ this might work instead, and might persist through upgrades:

    systemctl edit plasma-ksmserver.service
and then put this in the file you get to edit:
    [Service]
    ExecStart=/usr/bin/ksmserver --no-lockscreen
Regardless of which approach you need to use, if you do not force ksmserver (1) to stop squatting on the DBus endpoint, 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.

    LAUNCHING XSCREENSAVER FROM SYSTEMD

If the above didn't do it, and your system has systemd (1), maybe this is how it works:
1: Create a service.
  Create the file ~/.config/systemd/user/xscreensaver.service containing:
    [Unit]
    Description=XScreenSaver
    [Service]
    ExecStart=/usr/bin/xscreensaver
    Restart=on-failure
    [Install]
    WantedBy=default.target
2. Enable it.
 
    systemctl --user enable xscreensaver
Then restart X11.

    LAUNCHING XSCREENAVER FROM UPSTART

If your system has upstart (7) instead of systemd (1), maybe this will work: launch the "Startup Applications" applet, click "Add", enter these lines, then restart X11:

    LAUNCHING XSCREENSAVER FROM GDM

You can run xscreensaver from your gdm (1) session, so that the screensaver will run even when nobody is logged in on the console. To do this, run gdmconfig (1).

On the General page set the Local Greeter to Standard Greeter.

On the Background page, type the command "xscreensaver --nosplash" into the Background Program 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 /etc/X11/gdm/gdm.conf to include:

In this situation, the xscreensaver process will probably be running as user gdm instead of as root. You can configure the settings for this nobody-logged-in state (timeouts, DPMS, etc.) by editing the ~gdm/.xscreensaver file.

It is safe to run xscreensaver as root (as xdm or gdm may do). If run as root, xscreensaver changes its effective user and group ids to something safe (like "nobody") 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 xscreensaver from gdm, then this probably means that you have xauth (1) or some other security mechanism turned on. For information on the X server's access control mechanisms, see the man pages for X (1), Xsecurity (1), xauth (1), and xhost (1).

    LAPTOP LIDS WITHOUT SYSTEMD

BSD systems or other systems without systemd (1) or elogind (8) might have luck by adding xscreensaver-command --suspend to some appropriate spot in /etc/acpi/events/anything or in /etc/acpi/handler.sh, if those files exist.

THE WAYLAND PROBLEM
Wayland is a completely different window system that is intended to replace X11. After 13+ years of trying, some Linux distros have finally begun enabling it by default. Most deployments of it also include XWayland, which is a compatibility layer that allows some X11 programs to continue to work within a Wayland environment.

Unfortunately, XScreenSaver is not one of those programs.

If your system is running XWayland, XScreenSaver will malfunction in two ways:

1: It will be unable to detect user activity in non-X11 programs.
 

This means that while a native Wayland program is selected, XScreenSaver will think that you are idle, and may blank the screen prematurely.

2: It will be unable to lock the screen.
 

This is because X11 grabs don't work properly under XWayland, so there is no way for XScreenSaver to prevent the user from switching away from the screen locker to another application.

In short, for XScreenSaver to work properly, you will need to switch off Wayland and use the X Window System like in the "good old days".

    TO DISABLE WAYLAND UNDER GNOME

The login screen should have a gear-icon menu that lets you change the session type from "GNOME" (the Wayland session) to "GNOME on Xorg" (the X11 session).

Alternately, edit /etc/gdm/custom.conf and make sure it includes this line:

    TO DISABLE WAYLAND UNDER KDE

The login screen should have a menu that lets you change the session type to "Plasma (X11)".

Alternately, edit /etc/sddm.conf and change the SessionDir line under the [Wayland] section to say:

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.

    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.

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 DontZap flag in your xorg.conf or XF86Config or XF86Config-4 file, depending which is in use on your system. See XF86Config (5) for details.

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 DontVTSwitch in your xorg.conf, 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.

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 AllowClosedownGrabs in xorg.conf.

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:
    echo 176 > /proc/sys/kernel/sysrq
There's little that I can do to make the screen locker be secure so long as the kernel and X11 developers are actively 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.

    THE OOM-KILLER

Even if you have disabled the Alt-SysRq-F OOM-killer keystroke, the OOM-killer might still decide to assassinate XScreenSaver at random, which will unlock your screen. If the xscreensaver-auth(6) 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 crond (8). You can disable the OOM-killer entirely with:

    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 Xsecurity (1) and xauth (1).

    PAM PASSWORDS

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

    DON'T LOG IN AS ROOT

In order for it to be safe for XScreenSaver to be launched by xdm, certain precautions had to be taken, among them that XScreenSaver never runs as root. In particular, if it is launched as root (as xdm is likely to do), XScreenSaver will disavow its privileges, and switch itself to a safe user id (such as nobody).

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

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

MULTI-USER OR SITE-WIDE CONFIGURATION
For a single user, the proper way to configure XScreenSaver is to simply run the 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 .xscreensaver in your home directory; or in the X resource database. If the .xscreensaver file exists, it overrides any settings in the resource database.

The syntax of the .xscreensaver file is similar to that of the .Xdefaults file; for example, to set the timeout parameter n the .xscreensaver file, you would write the following:

whereas, in the .Xdefaults file, you would write If you change a setting in the .xscreensaver 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 .Xdefaults file, and then tell the running xscreensaver process to restart itself, like so:

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 .xscreensaver file. The .Xdefaults file and the app-defaults file will never be written by XScreenSaver itself.

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

timeout (class Time)
  The screensaver will activate (blank the screen) after the keyboard and mouse have been idle for this many minutes. Default 10 minutes.

cycle (class Time)
  After the screensaver has been running for this many minutes, the currently running graphics-hack sub-process will be killed (with SIGTERM), 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 cycle minutes, they don't all change at the same time.

lock (class Boolean)
  Enable locking: before the screensaver will turn off, it will require you to type the password of the logged-in user.

lockTimeout (class Time)
  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 timeout 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, lockTimeout 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.

passwdTimeout (class Time)
  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.

dpmsEnabled (class Boolean)
  Whether power management is enabled.

dpmsStandby (class Time)
  If power management is enabled, how long until the monitor goes solid black.

dpmsSuspend (class Time)
  If power management is enabled, how long until the monitor goes into power-saving mode.

dpmsOff (class Time)
  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 Power Management section, below, for more information.

dpmsQuickOff (class Boolean)
  If mode is blank and this is true, then the screen will be powered down immediately upon blanking, regardless of other power-management settings.

verbose (class Boolean)
  Whether to print diagnostics. Default false.

splash (class Boolean)
  Whether to display a splash screen at startup. Default true.

splashDuration (class Time)
  How long the splash screen should remain visible; default 5 seconds.

helpURL (class URL)
  The splash screen has a Help button on it. When you press it, it will display the web page indicated here in your web browser.

loadURL (class LoadURL)
  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 helpURL.

demoCommand (class DemoCommand)
  This is the shell command run when the Demo button on the splash window is pressed. It defaults to xscreensaver-settings (1).

newLoginCommand (class NewLoginCommand)
  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 gdmflexiserver (1), kdmctl (1), lxdm (1) or dm-tool (1).

nice (class Nice)
  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 nice (1) for details.)

fade (class Boolean)
  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.

unfade (class Boolean)
  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 fade is true as well. Default: true.

fadeSeconds (class Time)
  If fade is true, this is how long the fade will be in seconds. Default 3 seconds.

ignoreUninstalledPrograms (class Boolean)
  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 xscreensaver-settings (1) program will suppress the non-existent programs from the list if this is true. Default: false.

authWarningSlack (class Integer)
  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.

mode (class Mode)
  Controls the screen-saving behavior. Valid values are:

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

random-same
  Like random, but if there are multiple screens, each screen will run the same random display mode, instead of each screen running a different one.

one When blanking the screen, only ever use one particular display mode (the one indicated by the selected setting).

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

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

selected (class Integer)
  When mode is set to one, this is the one, indicated by its index in the programs list. You're crazy if you count them and set this number by hand: let xscreensaver-settings (1) do it for you!

programs (class Programs)
  The graphics hacks which XScreenSaver runs when the user is idle. The value of this resource is a multi-line string, one sh-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 mode setting), and run. After the cycle 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 xscreensaver-settings (1) program).

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

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 deletes 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 disables 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 ~/.xscreensaver file:

    programs:  \
           qix -root                          \n\
           ico -r -faces -sleep 1 -obj ico    \n\
           xdaliclock -builtin2 -root         \n\
           xv -root -rmode 5 image.gif -quit  \n
The default XScreenSaver hacks directory (typically /usr/libexec/xscreensaver/) is prepended to $PATH before searching for these programs.

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

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:

    mono:   mono-program  -root        \n\
    color:  color-program -root        \n\
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:
    PseudoColor: cmap-program  -root   \n\
    TrueColor:   24bit-program -root   \n\
In addition to the symbolic visual names described above (in the discussion of the visualID resource) one other visual name is supported in the programs list:
 
default-n
  This is like default, but also requests the use of the default colormap, instead of a private colormap.

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.

visualID (class VisualID)
  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 visualID, not merely visual; if you set the visual resource instead, things will malfunction in obscure ways for obscure reasons.)

Valid values for the VisualID resource are:

default Use the screen's default visual (the visual of the root window). This is the default.
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.
mono Use a monochrome visual, if there is one.
gray Use a grayscale or staticgray visual, if there is one and it has more than one plane (that is, it's not monochrome).
color Use the best of the color visuals, if there are any.
GL Use the visual that is best for OpenGL programs. (OpenGL programs have somewhat different requirements than other X programs.)
class where class is one of StaticGray, StaticColor, TrueColor, GrayScale, PseudoColor, or DirectColor. Selects the deepest visual of the given class.
N where number (decimal or hex) is interpreted as a visual id number, as reported by the 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.

Note that this option specifies only the default visual that will be used: the visual used may be overridden on a program-by-program basis. See the description of the programs resource, above.

installColormap (class Boolean)
  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 default-n name in the section about the programs resource.

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

pointerHysteresis (class Integer)
  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.

A single pixel of motion will still cause the monitor to power back on, but not un-blank. This is because the X11 server itself unfortunately handles power-management-related activity detection rather than XScreenSaver.

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!

ENVIRONMENT

DISPLAY to get the default host and display number, and to inform the sub-programs of the screen on which to draw.
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".
PATH to find the sub-programs to run, including the display modes.
HOME for the directory in which to read the .xscreensaver file.
XENVIRONMENT
  to get the name of a resource file that overrides the global resources stored in the RESOURCE_MANAGER property.

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/

COPYRIGHT
Copyright © 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.

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!