Provided by: xscreensaver_6.08+dfsg1-1ubuntu3_amd64 bug

NAME

       xscreensaver - extensible screen saver and screen locking framework

SYNOPSIS

       xscreensaver [--display host:display.screen] [--verbose] [--version] [--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.

            xscreensaver &
            xscreensaver-settings

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.

       --version
               Print the version number and exit.

       --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.  Do not use xset(1) to manually change the power
       management settings, that won't work.

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

LAPTOP LIDS

       If  your  system uses systemd(1) 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  do not have systemd(1), you might want to get in the habit of manually locking your
       screen before closing the lid (xscreensaver-command --lock).

PLAYING VIDEOS

       Likewise, if you have systemd(1) 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 D-Bus.

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 included XScreenSaver as-is, and everything just worked.  Not any more!

           1: Fully uninstall the other screen saver packages:

                   sudo apt remove gnome-screensaver
                   sudo apt remove mate-screensaver
                   sudo apt remove cinnamon-screensaver
                   sudo apt remove light-locker
              or
                   sudo rpm -e gnome-screensaver
                   sudo rpm -e mate-screensaver
                   sudo rpm -e cinnamon-screensaver
                   sudo rpm -e light-locker

              Be careful that it doesn't try to uninstall all of GNOME.

           2: Turn off GNOME's built-in blanking.
              Set  all  of  the  following  settings  to  "Never"  or  "Off",  as  these  are  all controlled by
              xscreensaver-settings(1) now:

              "Settings / Privacy / Screen Lock / Blank Screen Delay"
              "Settings / Privacy / Screen Lock / Automatic Screen Lock"
              "Settings / Power / Blank Screen"
              "Settings / Power / Automatic Suspend"

           3: Launch XScreenSaver at login.
              Launch "Tweaks", select "Startup Applications", click the plus  sign,  and  select  "XScreenSaver"
              (not "XScreenSaver Settings") from the (very long) menu.

              Or, see the "LAUNCHING XSCREENSAVER FROM SYSTEMD" section below.  That works too.

           4: Make GNOME's "Lock" icon use XScreenSaver.
              This  used  to work, but no longer does with GNOME 3.38.  If you figure it out, let me know!  This
              still works for Cinnamon 4.8 and MATE 1.24:

                   sudo ln -sf /usr/bin/xscreensaver-command \
                          /usr/bin/gnome-screensaver-command
                   sudo ln -sf /usr/bin/xscreensaver-command \
                       /usr/bin/cinnamon-screensaver-command
                   sudo ln -sf /usr/bin/xscreensaver-command \
                           /usr/bin/mate-screensaver-command
                   sudo ln -sf /usr/bin/xscreensaver-command \
                          /usr/bin/xfce4-screensaver-command
                   sudo ln -sf /usr/bin/xscreensaver-command \
                               /usr/bin/light-locker-command

              This change will get blown away when you upgrade.

   INSTALLING XSCREENSAVER ON KDE
       Like GNOME, KDE also decided to re-invent the wheel.  To replace the KDE screen saver with  XScreenSaver,
       do the following:

           1: Turn off KDE's built-in blanking.
              In   System   Settings,   un-check   the   following   items,   as   these   are   controlled   by
              xscreensaver-settings(1) now:

              "Workspace Behavior / Screen Locking / Lock automatically"
              "Workspace Behavior / Screen Locking / After waking from sleep"
              "Workspace Behavior / Screen Locking / Keyboard shortcut"
              "Hardware / Power Management / Screen Energy Saving"
              "Hardware / Power Management / Suspend session"
              "Hardware / Power Management / Laptop lid closed" = Do Nothing

              If there are multiple tabs, you may need to change these settings on all three  of  them:  "On  AC
              power", "Battery" and "Low Battery".

           2: Launch XScreenSaver at login.
              Copy the file /usr/share/applications/xscreensaver.desktop into the directory ~/.config/autostart/

           3: Make KDE's "Lock" icon use XScreenSaver.
              Find  the  "kscreenlocker_greet"  program.   It  might be in "/usr/lib/*/libexec/", or it might be
              somewhere else.  Delete that file and replace it with a file containing these two lines.  Make  it
              executable (chmod a+x).

                   #!/bin/sh
                   xscreensaver-command --lock &

              This change will get blown away when you upgrade.

           4: Turn off KDE's built-in locking on suspend, even harder.
              Even  after  disabling  KDE's  screen  locking,  above, it is possible that KDE will still use its
              built-in locker when you close your laptop's lid.  If that is happening, double-check the settings
              above,  but  if  those  are correct, try the following.  First, ensure you are running KDE 5.21 or
              newer.  Next, enable "systemd user sessions" for KDE so that  you  can  edit  the  parameters  for
              ksmserver:

                   kwriteconfig5 --file startkderc --group General \
                     --key systemdBoot true

              Log out and back in.

              Next, edit the plasma-ksmserver service to change how ksmserver is launched:

                   systemctl edit --user plasma-ksmserver.service

              Replace the contents of the file that lets you edit with this:

                   [Service]
                   ExecStart=
                   ExecStart=/usr/bin/ksmserver --no-lockscreen

              Then log out and back in again.

   LAUNCHING XSCREENSAVER FROM LXDE
       Add the line @xscreensaver to /etc/xdg/lxsession/LXDE/autostart or /etc/xdg/lxsession/LXDE-pi/autostart.

   LAUNCHING XSCREENSAVER FROM SYSTEMD
       If you are not using GNOME, KDE or LXDE, the way to launch XScreenSaver at login is probably systemd(1).

       Copy  the  file  /usr/share/xscreensaver/xscreensaver.service into the directory ~/.config/systemd/user/.
       Create that directory first if it doesn't exist.  Then enable it with:

            systemctl --user enable xscreensaver

   LAUNCHING XSCREENAVER FROM UPSTART
       If you are not using GNOME, KDE or LXDE, and your system uses upstart(7) instead  of  systemd(1),  launch
       the "Startup Applications" applet, click "Add", and enter these lines:

            Name: XScreenSaver
            Command: xscreensaver
            Comment: XScreenSaver

   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.

   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 --no-splash" 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:

            Greeter=/usr/bin/gdmlogin
            BackgroundProgram=xscreensaver --no-splash
            RunBackgroundProgramAlways=true

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

       If  you get "connection refused" errors when running xscreensaver from gdm, then this probably means that
       you are having xauth(1) problems.  For information on the X server's access control mechanisms,  see  the
       man pages for X(1), Xsecurity(1), xauth(1), and xhost(1).

       There might be a way to accomplish this with other display managers.  It's a mystery!

THE WAYLAND PROBLEM

       Wayland  is  a  completely  different  window system that is intended to replace X11.  After 14+ 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:

            WaylandEnable=false

   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:

            SessionDir=/dev/null

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 Xorg and XFree86 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(5) or XF86Config(5) file.

       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(5), 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(5).

       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:

            echo 2 > /proc/sys/vm/overcommit_memory
            echo vm.overcommit_memory = 2 >> /etc/sysctl.conf

       In  addition  to the kernel's OOM-killer, systemd(1) has its own.  The included xscreensaver.service file
       attempts to evade it, but you may want to just turn it off anyway:

            sudo systemctl disable --now systemd-oomd
            sudo systemctl mask systemd-oomd

   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
       Never  log  in  as  root.  Log in as a normal user and use sudo(1) as necessary.  If you are logged in as
       root, XScreenSaver will not lock your screen or run display modes, for numerous good and proper reasons.

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.  Changes are written to the ~/.xscreensaver file.

       If  you  want to set the system-wide defaults, then make your edits to /etc/X11/app-defaults/XScreenSaver
       instead.  The two files have similar (but not identical) syntax.

       You can also make changes via the X Resource Database and xrdb(1), but that can be very confusing and  is
       not really recommended.

       Options in ~/.xscreensaver override any settings in the resource database or app-defaults file.

       If  you  change a setting in the .xscreensaver file while XScreenSaver is already running, it will notice
       this, and reload the file as needed.  But if you change a setting in the X Resource  Database,  you  will
       need to restart XScreenSaver for those changes to take effect:

            xrdb < ~/.Xdefaults
            xscreensaver-command --restart

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.

       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 desktop will fade to black  instead  of
               simply winking out.  Default: true.

       unfade (class Boolean)
               If  this  is  true,  then  when  the screensaver deactivates, desktop will fade back ininstead 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.

               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.

       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/

SEE ALSO

       X(1), Xsecurity(1), xauth(1), xdm(1), gdm(1), xhost(1), systemd(1), elogind(8), xscreensaver-settings(1),
       xscreensaver-command(1),  xscreensaver-systemd(6),  xscreensaver-gl-helper(6),  xscreensaver-getimage(6),
       xscreensaver-text(6).

COPYRIGHT

       Copyright © 1991-2022 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>

       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!