xscreensaver - extensible screen saver framework, plus locking

xscreensaver [-display host:display.screen] [-verbose] [-no-capture-stderr] [-no-splash]

The xscreensaver program waits until the keyboard and mouse have been idle for a period, and then runs a graphics demo chosen at random. It turns off as soon as there is any mouse or keyboard activity.

This program can lock your terminal in order to prevent others from using it, though its default mode of operation is merely to display pretty pictures on your screen when it is not in use.

It also provides configuration and control of your monitor's power-saving features.

For the impatient, try this: xscreensaver & xscreensaver-demo The xscreensaver-demo(1) program pops up a dialog box that lets you configure the screen saver, and experiment with the various display modes.

Note: unlike xlock(1), xscreensaver has a client-server model: the xscreensaver program is a daemon that runs in the background; it is controlled by the foreground xscreensaver-demo(1) and xscreensaver-command(1) programs.

The easiest way to configure xscreensaver is to simply run the xscreensaver-demo(1) program, and change the settings through the GUI. The rest of this manual page describes lower level ways of changing settings.

I'll repeat that because it's important:

The easy way to configure xscreensaver is to run the xscreensaver-demo(1) program. You shouldn't need to know any of the stuff described in this manual unless you are trying to do something tricky, like customize xscreensaver for site-wide use or something.

Options to xscreensaver are stored in one of two places: in a .xscreensaver file 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 paramter in the .xscreensaver file, you would write the following: timeout: 5 whereas, in the .Xdefaults file, you would write xscreensaver.timeout: 5 If you change a setting in the .xscreensaver file while xscreensaver is already running, it will notice this, and reload the file. (The file will be reloaded the next time the screen saver needs to take some action, such as blanking or unblanking the screen, or picking a new graphics mode.)

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: xrdb < ~/.Xdefaults xscreensaver-command -restart 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 /usr/lib/X11/app-defaults/XScreenSaver, but different systems might keep it in a different place (for example, /usr/openwin/lib/app-defaults/XScreenSaver on Solaris.)

When settings are changed in the Preferences dialog box (see above) the current settings will be written to the .xscreensaver file. (The .Xdefaults file and the app-defaults file will never be written by xscreensaver itself.)

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.

lock (class Boolean)

Enable locking: before the screensaver will turn off, it will require you to type the password of the logged-in user (really, the person who ran xscreensaver), or the root password. (Note: this doesn't work if the screensaver is launched by xdm(1) because it can't know the user-id of the logged-in user. See the ``Using XDM(1)'' section, below.

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, -lock-timeout 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.) This should not be too large: the X server is grabbed for the duration that the password dialog box is up (for security purposes) and leaving the server grabbed for too long can cause problems.

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.

visualID (class VisualID)

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.)

Legal 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.

number

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, below.

installColormap (class Boolean)

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.

verbose (class Boolean)

Whether to print diagnostics. Default false.

timestamp (class Boolean)

Whether to print the time of day along with any other diagnostic messages. Default true.

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.

quad (class Boolean)

If true, then four screensavers will be run on each monitor. Use at your own risk!

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-demo(1).

prefsCommand (class PrefsCommand)

This is the shell command run when the Prefs button on the splash window is pressed. It defaults to xscreensaver-demo -prefs.

nice (class Nice)

The sub-processes created 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. This only works on certain systems. A fade will also be done when switching graphics hacks (when the cycle timer expires.) 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 only works on certain systems, and if fade is true as well. Default false.

fadeSeconds (class Time)

If fade is true, this is how long the fade will be in seconds (default 3 seconds.)

fadeTicks (class Integer)

If fade is true, this is how many times a second the colormap will be changed to effect a fade. Higher numbers yield smoother fades, but may make the fades take longer than the specified fadeSeconds if your server isn't fast enough to keep up. Default 20.

captureStderr (class Boolean)

Whether xscreensaver should redirect its stdout and stderr streams to the window itself. Since its nature is to take over the screen, you would not normally see error messages generated by xscreensaver or the sub-programs it runs; this resource will cause the output of all relevant programs to be drawn on the screensaver window itself, as well as being written to the controlling terminal of the screensaver driver process. Default true.

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-demo(1) program will suppress the non-existent programs from the list if this is true. Default: false.

GetViewPortIsFullOfLies (class Boolean)

Set this to true if the xscreensaver window doesn't cover the whole screen. This works around a longstanding XFree86 bug #421. See the xscreensaver FAQ for details.

font (class Font)

The font used for the stdout/stderr text, if captureStderr is true. Default *-medium-r-*-140-*-m-* (a 14 point fixed-width font.)

mode (class Mode)

Controls the behavior of xscreensaver. Legal 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-demo(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-demo(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 Make sure your $PATH environment variable is set up correctly before xscreensaver is launched, or it won't be able to find the programs listed in the programs resource.

To use a program as a screensaver, two things are required: that that program draw on the root window (or be able to be configured to draw on the root window); and that that program understand ``virtual root'' windows, as used by virtual window managers such as tvtwm(1). (Generally, this is accomplished by just including the "vroot.h" header file in the program's source.)

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. (That is, it behaves as if the -no-install command-line option was specified, but only for this particular hack.) This is provided because some third-party programs that draw on the root window (notably: xv(1), and xearth(1)) make assumptions about the visual and colormap of the root window: assumptions which xscreensaver can violate.

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.

You shouldn't ever need to change the following resources:

pointerPollTime (class Time)

When server extensions are not in use, this controls how frequently xscreensaver checks to see if the mouse position or buttons have changed. Default 5 seconds.

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.

windowCreationTimeout (class Time)

When server extensions are not in use, this controls the delay between when windows are created and when xscreensaver selects events on them. Default 30 seconds.

initialDelay (class Time)

When server extensions are not in use, xscreensaver will wait this many seconds before selecting events on existing windows, under the assumption that xscreensaver is started during your login procedure, and the window state may be in flux. Default 0. (This used to default to 30, but that was back in the days when slow machines and X terminals were more common...)

There are a number of different X server extensions which can make xscreensaver's job easier. The next few resources specify whether these extensions should be utilized if they are available.

sgiSaverExtension (class Boolean)

This resource controls whether the SGI SCREEN_SAVER server extension will be used to decide whether the user is idle. This is the default if xscreensaver has been compiled with support for this extension (which is the default on SGI systems.). If it is available, the SCREEN_SAVER method is faster and more reliable than what will be done otherwise, so use it if you can. (This extension is only available on Silicon Graphics systems, unfortunately.)

mitSaverExtension (class Boolean)

This resource controls whether the MIT-SCREEN-SAVER server extension will be used to decide whether the user is idle. However, the default for this resource is false, because even if this extension is available, it is flaky (and it also makes the fade option not work properly.) Use of this extension is strongly discouraged. Support for it will probably be removed eventually.

xidleExtension (class Boolean)

This resource controls whether the XIDLE server extension will be used to decide whether the user is idle. This is the default if xscreensaver has been compiled with support for this extension. (This extension is only available for X11R4 and X11R5 systems, unfortunately.)

procInterrupts (class Boolean)

This resource controls whether the /proc/interrupts file should be consulted to decide whether the user is idle. This is the default if xscreensaver has been compiled on a system which supports this mechanism (i.e., Linux systems.)

The benefit to doing this is that xscreensaver can note that the user is active even when the X console is not the active one: if the user is typing in another virtual console, xscreensaver will notice that and will fail to activate. For example, if you're playing Quake in VGA-mode, xscreensaver won't wake up in the middle of your game and start competing for CPU.

The drawback to doing this is that perhaps you really do want idleness on the X console to cause the X display to lock, even if there is activity on other virtual consoles. If you want that, then set this option to False. (Or just lock the X console manually.)

The default value for this resource is True, on systems where it works.

overlayStderr (class Boolean)

If captureStderr is True, and your server supports ``overlay'' visuals, then the text will be written into one of the higher layers instead of into the same layer as the running screenhack. Set this to False to disable that (though you shouldn't need to.)

overlayTextForeground (class Foreground)

The foreground color used for the stdout/stderr text, if captureStderr is true. Default: Yellow.

overlayTextBackground (class Background)

The background color used for the stdout/stderr text, if captureStderr is true. Default: Black.

bourneShell (class BourneShell)

The pathname of the shell that xscreensaver uses to start subprocesses. This must be whatever your local variant of /bin/sh is: in particular, it must not be csh.

xscreensaver also accepts a few command-line options, mostly for use when debugging: for normal operation, you should configure things via the ~/.xscreensaver file.

-display host:display.screen

The X display to use. For displays with multiple screens, XScreenSaver will manage all screens on the display simultaniously.

-verbose

Same as setting the verbose resource to true: print diagnostics on stderr and on the xscreensaver window.

-no-capture-stderr

Same as setting the captureStderr resource to false: do not redirect the stdout and stderr streams to the xscreensaver window itself. If xscreensaver is crashing, you might need to do this in order to see the error message.

When it is time to activate the screensaver, a full-screen black window is created on each screen of the display. Each window is created in such a way that, to any subsequently-created programs, it will appear to be a ``virtual root'' window. Because of this, any program which draws on the root window (and which understands virtual roots) can be used as a screensaver.

When the user becomes active again, the screensaver windows are unmapped, and the running subprocesses are killed by sending them SIGTERM. This is also how the subprocesses are killed when the screensaver decides that it's time to run a different demo: the old one is killed and a new one is launched.

Before launching a subprocess, xscreensaver stores an appropriate value for $DISPLAY in the environment that the child will receive. (This is so that if you start xscreensaver with a -display argument, the programs which xscreensaver launches will draw on the same display; and so that the child will end up drawing on the appropriate screen of a multi-headed display.)

When the screensaver turns off, or is killed, care is taken to restore the ``real'' virtual root window if there is one. Because of this, it is important that you not kill the screensaver process with kill -9 if you are running a virtual-root window manager. If you kill it with -9, you may need to restart your window manager to repair the damage. This isn't an issue if you aren't running a virtual-root window manager.

For all the gory details, see the commentary at the top of xscreensaver.c.

You can control a running screensaver process by using the xscreensaver-command(1) program (which see.)

Modern X servers contain support to power down the monitor after an idle period. If the monitor has powered down, then xscreensaver will notice this (after a few minutes), and will not waste CPU by drawing graphics demos on a black screen. An attempt will also be made to explicitly power the monitor back up as soon as user activity is detected.

As of version 3.28 (Feb 2001), the ~/.xscreensaver file controls the configuration of your display's power management settings: if you have used xset(1) to change your power management settings, then xscreensaver will override those changes with the values specified in ~/.xscreensaver (or with its built-in defaults, if there is no ~/.xscreensaver file yet.)

To change your power management settings, run xscreensaver-demo(1) and change the various timeouts through the user interface. Alternately, you can edit the ~/.xscreensaver file directly.

If the power management section is grayed out in the xscreensaver-demo(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.

If you're using a laptop, don't be surprised if changing the DPMS settings has no effect: many laptops have monitor power-saving behavior built in at a very low level that is invisible to Unix and X. On such systems, you can typically adjust the power-saving delays only by changing settings in the BIOS in some hardware-specific way.

If DPMS seems not to be working with XFree86, make sure the "DPMS" option is set in your /etc/X11/XF86Config file. See the XF86Config(5) manual for details.

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

The trick to using xscreensaver with xdm is this: keep in mind the two very different states in which xscreensaver will be running:

1: Nobody logged in.

If you're thinking of running xscreensaver from XDM at all, then it's probably because you want graphics demos to be running on the console when nobody is logged in there. In this case, xscreensaver will function only as a screen saver, not a screen locker: it doesn't make sense for xscreensaver to lock the screen, since nobody is logged in yet! The only thing on the screen is the XDM login prompt.

2: Somebody logged in.

Once someone has logged in through the XDM login window, the situation is very different. For example: now it makes sense to lock the screen (and prompt for the logged in user's password); and now xscreensaver should consult that user's ~/.xscreensaver file; and so on.

The difference between these two states comes down to a question of, which user is the xscreensaver process running as? For the first state, it doesn't matter. If you start xscreensaver in the usual XDM way, then xscreensaver will probably end up running as root, which is fine for the first case (the ``nobody logged in'' case.)

However, once someone is logged in, running as root is no longer fine: because xscreensaver will be consulting root's .xscreensaver file instead of that of the logged in user, and won't be prompting for the logged in user's password, and so on. (This is not a security problem, it's just not what you want.)

So, once someone has logged in, you want xscreensaver to be running as that user. The way to accomplish this is to kill the old xscreensaver process and start a new one (as the new user.)

The simplest way to accomplish all of this is as follows:

1: Launch xscreensaver before anyone logs in.

To the file /usr/lib/X11/xdm/Xsetup, add the lines xhost +localhost xscreensaver-command -exit xscreensaver & This will run xscreensaver as root, over the XDM login window. Moving the mouse will cause the screen to un-blank, and allow the user to type their password at XDM to log in.

2: Restart xscreensaver when someone logs in.

Near the top of the file /usr/lib/X11/xdm/Xsession, add those same lines: xscreensaver-command -exit xscreensaver & When someone logs in, this will kill off the existing (root) xscreensaver process, and start a new one, running as the user who has just logged in. If the user's .xscreensaver file requests locking, they'll get it. They will also get their own choice of timeouts, and graphics demos, and so on.

Alternately, each user could just put those lines in their personal ~/.xsession files.

Make sure you have $PATH set up correctly in the Xsetup and Xsession scripts, or xdm won't be able to find xscreensaver, and/or xscreensaver won't be able to find its graphics demos.

(If your system does not seem to be executing the Xsetup file, you may need to configure it to do so: the traditional way to do this is to make that file the value of the DisplayManager*setup resource in the /usr/lib/X11/xdm/xdm-config file. See the man page for xdm(1) for more details.)

It is safe to run xscreensaver as root (as xdm is likely to 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 xdm, then this probably means that you have xauth(1) or some other security mechanism turned on. One way around this is to add "xhost +localhost" to Xsetup, just before xscreensaver is launched.

Note that this will give access to the X server to anyone capable of logging in to the local machine, so in some environments, this might not be appropriate. If turning off file-system-based access control is not acceptable, then running xscreensaver from the Xsetup file might not be possible, and xscreensaver will only work when running as a normal, unprivileged user.

For more information on the X server's access control mechanisms, see the man pages for X(1), Xsecurity(1), xauth(1), and xhost(1).

Using xscreensaver with gdm(1) is easy, because gdm has a configuration tool. Just fire up gdmconfig(1) and on the Background page, type "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.)

Another way to accomplish the same thing is to edit the file /etc/X11/gdm/gdm.conf to include: BackgroundProgram=xscreensaver -nosplash RunBackgroundProgramAlways=true In this situation, the xscreensaver process will probably be running as user gdm instead of root. You can configure the settings for this nobody-logged-in state (timeouts, DPMS, etc.) by editing the ~gdm/.xscreensaver file.

To get gdm to run the BackgroundProgram, you may need to switch it from the "Graphical Greeter" to the "Standard Greeter".

I understand that KDE has invented their own wrapper around xscreensaver, that is inferior to xscreensaver-demo(1) in any number of ways. I've never actually seen it, but I'm told that this is the way you disable it:

1: Switch off KDE's screen saver.

Open the ``Control Center'' and select the ``Look and Feel / Screensaver'' page. Turn off the ``Enable Screensaver'' checkbox.

2: Find your Autostart directory.

Open the ``Look and Feel / Desktop / Paths'' page, and see what your ``Autostart'' directory is set to: it will probably be ~/.kde3/Autostart/ or something similar.

3: Make xscreensaver be an Autostart program.

Create a file in your autostart directory called xscreensaver.desktop that contains the following five lines: [Desktop Entry] Exec=xscreensaver Name=XScreensaver Type=Application X-KDE-StartupNotify=false

4: Make the various "lock session" buttons call xscreensaver.

Replace the file /usr/bin/kdesktop_lock with these two lines: #!/bin/sh xscreensaver-command -lock Make sure the file is executable (chmod a+x).

Now use xscreensaver normally, controlling it via the usual xscreensaver-demo(1) and xscreensaver-command(1) mechanisms.

The easiest way to use xscreensaver on a system with CDE is to simply switch off the built-in CDE screensaver, and use xscreensaver instead; and second, to tell the front panel to run xscreensaver-command(1) with the -lock option when the Lock icon is clicked.

To accomplish this involves five steps:

1: Switch off CDE's locker

Do this by turning off ``Screen Saver and Screen Lock'' in the Screen section of the Style Manager.

2: Edit sessionetc

Edit the file ~/.dt/sessions/sessionetc and add to it the line xscreensaver & And make sure the sessionetc file is executable. This will cause xscreensaver to be launched when you log in. (As always, make sure that xscreensaver and the graphics demos are on your $PATH; the path needs to be set in .cshrc and/or .dtprofile, not .login.)

3: Create XScreenSaver.dt

Create a file called ~/.dt/types/XScreenSaver.dt with the following contents: ACTION XScreenSaver { LABEL XScreenSaver TYPE COMMAND EXEC_STRING xscreensaver-command -lock ICON Dtkey WINDOW_TYPE NO_STDIO } This defines a ``lock'' command for the CDE front panel, that knows how to talk to xscreensaver.

4: Create Lock.fp

Create a file called ~/.dt/types/Lock.fp with the following contents: CONTROL Lock { TYPE icon CONTAINER_NAME Switch CONTAINER_TYPE SWITCH POSITION_HINTS 1 ICON Fplock LABEL Lock PUSH_ACTION XScreenSaver HELP_TOPIC FPOnItemLock HELP_VOLUME FPanel } This associates the CDE front panel ``Lock'' icon with the lock command we just defined in step 3.

5: Restart

Select ``Restart Workspace Manager'' from the popup menu to make your changes take effect. If things seem not to be working, check the file ~/.dt/errorlog for error messages.

Since CDE is a descendant of VUE, the instructions for using xscreensaver under VUE are similar to the above:

1: Switch off VUE's locker

Open the ``Style Manager'' and select ``Screen.'' Turn off ``Screen Saver and Screen Lock'' option.

2: Make sure you have a Session

Next, go to the Style Manager's, ``Startup'' page. Click on ``Set Home Session'' to create a session, then on ``Return to Home Session'' to select this session each time you log in.

3: Edit vue.session

Edit the file ~/.vue/sessions/home/vue.session and add to it the line vuesmcmd -screen 0 -cmd "xscreensaver" This will cause xscreensaver to be launched when you log in. (As always, make sure that xscreensaver and the graphics demos are on your $PATH; the path needs to be set in .cshrc and/or .profile, not .login.)

3: Edit vuewmrc

Edit the file ~/.vue/vuewmrc and add (or change) the Lock control: CONTROL Lock { TYPE button IMAGE lock PUSH_ACTION f.exec "xscreensaver-command -lock" HELP_TOPIC FPLock } This associates the VUE front panel ``Lock'' icon with the xscreensaver lock command.

Bugs? There are no bugs. Ok, well, maybe. If you find one, please let me know. http://www.jwz.org/xscreensaver/bugs.html explains how to construct the most useful bug reports.

Locking and XDM

If xscreensaver has been launched from xdm(1) before anyone has logged in, you will need to kill and then restart the xscreensaver daemon after you have logged in, or you will be confused by the results. (For example, locking won't work, and your ~/.xscreensaver file will be ignored.)

When you are logged in, you want the xscreensaver daemon to be running under your user id, not as root or some other user.

If it has already been started by xdm, you can kill it by sending it the exit command, and then re-launching it as you, by putting something like the following in your personal X startup script: xscreensaver-command -exit xscreensaver & The ``Using XDM(1)'' section, above, goes into more detail, and explains how to configure the system to do this for all users automatically.

Locking and root logins

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.)

The solution to this is simple: you shouldn't be logging in on the console as root in the first place! (What, are you crazy or something?)

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

XAUTH and XDM

For xscreensaver to work when launched by xdm(1), programs running on the local machine as user "nobody" must be able to connect to the X server. This means that if you want to run xscreensaver on the console while nobody is logged in, you may need to disable cookie-based access control (and allow all users who can log in to the local machine to connect to the display.)

You should be sure that this is an acceptable thing to do in your environment before doing it. See the ``Using XDM(1)'' section, above, for more details.

Passwords

If you get an error message at startup like ``couldn't get password of user'' then this probably means that you're on a system in which the getpwent(3) library routine can only be effectively used by root. If this is the case, then xscreensaver must be installed as setuid to root in order for locking to work. Care has been taken to make this a safe thing to do.

It also may mean that your system uses shadow passwords instead of the standard getpwent(3) interface; in that case, you may need to change some options with configure and recompile.

If you change your password after xscreensaver has been launched, it will continue using your old password to unlock the screen until xscreensaver is restarted. On some systems, it may accept both your old and new passwords. So, after you change your password, you'll have to do xscreensaver-command -restart to make xscreensaver notice.

PAM Passwords

If your system uses PAM (Pluggable Authentication Modules), then in order for xscreensaver to use PAM properly, PAM must be told about xscreensaver. The xscreensaver installation process should update the PAM data (on Linux, by creating the file /etc/pam.d/xscreensaver for you, and on Solaris, by telling you what lines to add to the /etc/pam.conf file.)

If the PAM configuration files do not know about xscreensaver, then you might be in a situation where xscreensaver will refuse to ever unlock the screen.

This is a design flaw in PAM (there is no way for a client to tell the difference between PAM responding ``I have never heard of your module,'' and responding, ``you typed the wrong password.'') As far as I can tell, there is no way for xscreensaver to automatically work around this, or detect the problem in advance, so if you have PAM, make sure it is configured correctly!

Colormap lossage: TWM

The installColormap option doesn't work very well with the twm(1) window manager and its descendants, on 8-bit screens.

There is a race condition between the screensaver and this window manager, which can result in the screensaver's colormap not getting installed properly, meaning the graphics hacks will appear in essentially random colors. (If the screen goes white instead of black, this is probably why.)

The mwm(1) and olwm(1) window managers don't have this problem. The race condition exists because X (really, ICCCM) does not provide a way for an OverrideRedirect window to have its own colormap, short of grabbing the server (which is neither a good idea, nor really possible with the current design.) What happens is that, as soon as xscreensaver installs its colormap, twm responds to the resultant ColormapNotify event by re-installing the default colormap. Apparently, twm doesn't always do this; it seems to do it regularly if the screensaver is activated from a menu item, but seems to not do it if the screensaver comes on of its own volition, or is activated from another console.

Attention, window manager authors!

You should only call XInstallColormap(3) in response to user events. That is, it is appropriate to install a colormap in response to FocusIn, FocusOut, EnterNotify, and LeaveNotify events; but it is not appropriate to call it in response to ColormapNotify events. If you install colormaps in response to application actions as well as in response to user actions, then you create the situation where it is impossible for override-redirect applications (such as xscreensaver) to display their windows in the proper colors.

Colormap lossage: XV, XAnim, XEarth

Some programs don't operate properly on visuals other than the default one, or with colormaps other than the default one. See the discussion of the magic "default-n" visual name in the description of the programs resource in the Configuration section. When programs only work with the default colormap, you need to use a syntax like this: default-n: xv -root image-1.gif -quit \n\ default-n: xearth -nostars -wait 0 \n\ It would also work to turn off the installColormap option altogether, but that would deny extra colors to those programs that can take advantage of them.

Machine Load

Although this program ``nices'' the subprocesses that it starts, graphics-intensive subprograms can still overload the machine by causing the X server process itself (which is not ``niced'') to consume many cycles. Care has been taken in all the modules shipped with xscreensaver to sleep periodically, and not run full tilt, so as not to cause appreciable load.

However, if you are running the OpenGL-based screen savers on a machine that does not have a video card with 3D acceleration, they will make your machine slow, despite nice(1).

Your options are: don't use the OpenGL display modes; or, collect the spare change hidden under the cushions of your couch, and use it to buy a video card manufactured after 1998. (It doesn't even need to be fast 3D hardware: the problem will be fixed if there is any 3D hardware at all.)

XFree86's Magic Keystrokes

The XFree86 X server traps certain magic keystrokes before client programs ever see them. Two that are of note are Ctrl+Alt+Backspace, which causes the X server to exit; and Ctrl+Alt+Fn, which switches virtual consoles. The X server will respond to these keystrokes even if xscreensaver has the screen locked. Depending on your setup, you might consider this a problem.

Unfortunately, there is no way for xscreensaver itself to override the interpretation of these keys. If you want to disable Ctrl+Alt+Backspace globally, you need to set the DontZap flag in your /etc/X11/XF86Config file. To globally disable VT switching, you can set the DontVTSwitch flag. See the XF86Config(5) manual for details.

MIT Extension and Fading

The MIT-SCREEN-SAVER extension is junk. Don't use it.

When using the MIT-SCREEN-SAVER extension in conjunction with the fade option, you'll notice an unattractive flicker just before the fade begins. This is because the server maps a black window just before it tells the xscreensaver process to activate. The xscreensaver process immediately unmaps that window, but this results in a flicker. I haven't figured a way to get around this; it seems to be a fundamental property of the (mis-) design of this server extension.

It sure would be nice if someone would implement the SGI SCREEN_SAVER extension in XFree86; it's dead simple, and works far better than the over-engineered and broken MIT-SCREEN-SAVER extension.

Keyboard LEDs

If procInterrupts is on (which is the default on Linux systems) and you're using some program that toggles the state of your keyboard LEDs, xscreensaver won't work right: turning those LEDs on or off causes a keyboard interrupt, which xscreensaver will interpret as user activity. So if you're using such a program, set the procInterrupts resource to False.

Extensions

If you are not making use of one of the server extensions (XIDLE, SGI SCREEN_SAVER, or MIT-SCREEN-SAVER), then it is possible, in rare situations, for xscreensaver to interfere with event propagation and make another X program malfunction. For this to occur, that other application would need to not select KeyPress events on its non-leaf windows within the first 30 seconds of their existence, but then select for them later. In this case, that client might fail to receive those events. This isn't very likely, since programs generally select a constant set of events immediately after creating their windows and then don't change them, but this is the reason that it's a good idea to install and use one of the server extensions instead, to work around this shortcoming in the X protocol.

In all these years, I've not heard of even a single case of this happening, but it is theoretically possible, so I'm mentioning it for completeness...

DISPLAY

to get the default host and display number, and to inform the sub-programs of the screen on which to draw.

PATH

to find the sub-programs to run.

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.

The latest version of xscreensaver, an online version of this manual, and a FAQ can always be found at http://www.jwz.org/xscreensaver/

X(1), Xsecurity(1), xauth(1), xdm(1), gdm(1), xhost(1), xscreensaver-demo(1), xscreensaver-command(1), xscreensaver-gl-helper(1), xscreensaver-getimage(1), xscreensaver-text(1).

Copyright © 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 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.

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.

Thanks to Angela Goodman for the XScreenSaver logo.

Thanks to the many people who have contributed graphics demos to the package.

Thanks to David Wojtowicz for implementing lockTimeout.

Thanks to Martin Kraemer for adding support for shadow passwords and locking-disabled diagnostics.

Thanks to Patrick Moreau for the VMS port.

Thanks to Nat Lanza for the Kerberos support.

Thanks to Bill Nottingham for the initial PAM support.

And thanks to Jon A. Christopher for implementing the Athena dialog support, back in the days before Lesstif or Gtk were viable alternatives to Motif.