X(X)

Syntax

• Ultrix 3.1 (Digital)

• SunOS 4.0.3 (Sun)

• HP-UX 6.5 (Hewlett-Packard)

• Domain/OS 10.1 (HP/Apollo)

• A/UX 1.1 (Apple)

• AIX RT-2.2 and PS/2-1.1 (IBM)

• AOS-4.3 (IBM)

• UTEK 4.0 (Tektronix)

• NEWS-OS 3.2 (Sony; client only)

• UNICOS 5.0.1 (Cray; client only)

• UNIX System V, Release 3.2 (AT&T 6386 WGS; client only)

It should be relatively easy to build the client-side software on a variety of other systems. Commercial implementations are also available for a wide range of platforms.

The X Consortium requests that the following names be used when referring to this software:

• X

• X Window System

• X Version 11

• X Window System, Version 11

• X11

``X Window System'' is a trademark of the Massachusetts Institute of Technology.

Description

Although the most common case is for the client programs to be running on the same machine as the server, clients can be run transparently from other machines (including machines with different architectures and operating systems) as well.

X supports overlapping hierarchical subwindows and text and graphics operations, on both monochrome and color displays. For a full explanation of the functions that are available, see the Xlib -- C Language X Interface manual, the X Window System Protocol specification, the X Toolkit Intrinsics -- C Language Interface manual, and various toolkit documents.

The number of programs that use X is growing rapidly. Of particular interest are: a terminal emulator (scoterm), a window manager (pmwm), a display manager (scologin), a session manager (scosession), mail managing utilities (scomail and xbiff), a bitmap editor (bitmap, scopaint), access control programs (xauth and xhost), user preference setting programs (xrdb, xset, xsetroot), and xmodmap), a load monitor (xload), clocks (dclock,xclock and oclock), a font displayer (xfd), utilities for listing information about fonts, windows, and displays (xlsfonts, xfontsel, xlswins, xwininfo, xlsclients, xdpyinfo, and xprop), a diagnostic for seeing what events are generated and when (xev), screen image manipulation utilities (xwd, xwud, xpr, and xmag), and various demos (xeyes and ico).

Many other utilities, window managers, games, toolkits, etc. are available from the user-contributed software. See your site administrator for details.

Starting up

X display manager

If you want to always have X running on your display, your site administrator can set your machine up to use an X display manager program, such as scologin(XC). An X display manager program is typically started by the system at boot time and takes care of keeping the server running and getting users logged in. If you run an X display manager, you see a window on the screen welcoming you to the system and asking for your username and password. Simply type them in as you would at a normal terminal, pressing the <Return> key after each. If you make a mistake, an error message appears and you are asked to try again. After you have successfully logged in, the display manager starts up your X environment. By default, if you have an executable file named .startxrc in your home directory, the display manager treats it as a program (or shell script) to run to start up your initial clients (such as terminal emulators, clocks, a window manager, user settings for things such as the background, the speed of the pointer, etc.). Your site administrator can provide details.

xinit (run manually from the shell)

Sites that support more than one window system might choose to use the xinit program for starting X manually. If this is true for your machine, your site administrator will probably have provided a program named x11, startx, or xstart that does site-specific initialization (such as loading convenient default resources, running a window manager, displaying a clock, and starting several terminal emulators) in a nice way. If not, you can build such a script using the xinit program. This utility simply runs one user-specified program to start the server, runs another to start up any desired clients, and then waits for either to finish. Since either or both of the user-specified programs may be a shell script, this gives substantial flexibility at the expense of a nice interface. For this reason, xinit is not intended for end users.

Display names

This information is used by the application to determine how it should connect to the server and, on displays with multiple monitors, which screen it should use by default.

hostname

hostname specifies the name of the machine to which the display is physically connected. If the hostname is not given, the most efficient way of communicating to a server on the same machine will be used.

displaynumber

The phrase ``display'' is usually used to refer to a collection of monitors that share a common keyboard and pointer (mouse, tablet, etc.). Most workstations tend to only have one keyboard, and therefore, only one display. Larger, multi-user systems, however, will frequently have several displays so that more than one person can be doing graphics work at once. To avoid confusion, each display on a machine is assigned a display number (beginning at 0) when the X server for that display is started. The display number must always be given in a display name.

screennumber

Some displays share a single keyboard and pointer among two or more monitors. Since each monitor has its own set of windows, each screen is assigned a screen number (beginning at 0) when the X server for that display is started. If the screen number is not given, then screen 0 will be used.

On POSIX systems, the default display name is stored in your DISPLAY environment variable. This variable is set automatically by the scoterm terminal emulator. However, when you log into another machine on a network, you'll need to set DISPLAY by hand to point to your display as in the following examples:

% setenv DISPLAY myws:0
$ DISPLAY=myws:0; export DISPLAY

Finally, most X programs accept a command line option of -display displayname to temporarily override the contents of DISPLAY. This is most commonly used to pop windows on another person's screen or as part of a ``remote shell'' command to start a scoterm pointing back to your display as in the following examples:

% xeyes -display joesws:0 -geometry 1000x1000+0+0
% rcmd big /usr/bin/X11/scoterm -display myws:0 -ls </dev/null &

X servers listen for connections on a variety of different communications channels (network byte streams, shared memory, etc.). Because there can be more than one way of contacting a given server, the hostname part of the display name determines the type of channel (also called a transport layer) to be used. The sample servers from MIT support the following types of connections:

local

The hostname part of the display name should be the empty string. For example: ``:0'', ``:1'', and ``:0.1'' indicate local displays. The most efficient local transport is chosen.

TCP/IP

The hostname part of the display name should be the server machine's IP address name. Full Internet names, abbreviated names, and IP addresses are all allowed. For example, ``expo.lcs.mit.edu:0'', ``expo:0'', ``18.30.0.212:0'', ``bigmachine:1'', and ``hydra:0.1'' indicate displays on specific machines.

DECnet

The hostname part of the display name should be the server machine's nodename followed by two colons instead of one. For example: ``myws::0'', ``big::1'', and ``hydra::0.1''.

Access control

The file for authorization used by Xlib and X display managers can be specified with the environment variable XAUTHORITY, and defaults to the file .Xauthority in the home directory.

To manage a collection of authorization files containing a collection of authorization records use xauth. This program allows you to extract records and insert them into other files. Using this, you can send authorization to remote machines when you login. As the files are machine-independent, you can also simply copy the files or use NFS to share them. If you use several machines, and share a common home directory with NFS, then you never really have to worry about authorization files, the system should work correctly by default. Note that magic cookies transmitted ``in the clear'' over NFS or using ftp or rcp can be ``stolen'' by a network eavesdropper, and as such may enable unauthorized access. In many environments this level of security is not a concern, but if it is, you need to know the exact semantics of the particular magic cookie to know if this is actually a problem.

Geometry specifications

(where width, height, xoff, and yoff are numbers) for specifying a preferred size and location for this application's main window.

The width and height parts of the geometry specification are usually measured in either pixels or characters, depending on the application. The xoff and yoff parts are measured in pixels and are used to specify the distance of the window from the left or right and top and bottom edges of the screen, respectively. Both types of offsets are measured from the indicated edge of the screen to the corresponding edge of the window. The X offset may be specified in the following ways:

+xoff

The left edge of the window is to be placed xoff pixels in from the left edge of the screen (that is, the X coordinate of the window's origin will be xoff). xoff may be negative, in which case the window's left edge will be off the screen.

-xoff

The right edge of the window is to be placed xoff pixels in from the right edge of the screen. xoff may be negative, in which case the window's right edge will be off the screen.

The Y offset has similar meanings:

+yoff

The top edge of the window is to be yoff pixels below the top edge of the screen (that is, the Y coordinate of the window's origin will be yoff). yoff may be negative, in which case the window's top edge will be off the screen.

-yoff

The bottom edge of the window is to be yoff pixels above the bottom edge of the screen. yoff may be negative, in which case the window's bottom edge will be off the screen.

Offsets must be given as pairs; in other words, in order to specify either xoff or yoff both must be present. Windows can be placed in the four corners of the screen using the following specifications:

+0+0

upper left hand corner.

-0+0

upper right hand corner.

-0-0

lower right hand corner.

+0-0

lower left hand corner.

In the following examples, a terminal emulator will be placed in roughly the center of the screen and a load average monitor, mailbox, and clock will be placed in the upper right hand corner:

scoterm -fn 6x10 -geometry 80x24+30+200 &
dclock -geometry 48x48-0+0 &
xload -geometry 48x48-96+0 &
xbiff -geometry 48x48-48+0 &

Window managers

Since window managers are regular (albeit complex) client programs, a variety of different user interfaces can be built. The core distribution comes with a window manager named twm which supports overlapping windows, popup menus, point-and-click or click-to-type input models, title bars, nice icons (and an icon manager for those who do not like separate icon windows).

Several other window managers are available in the user-contributed software: gwm, m_swm, olwm, mwm, and tekwm. SCO OpenServer uses SCO Panner, pmwm, an enhanced version of the OSF/Motif Window Manager.

Font names

Sets of font families of the same resolution (usually measured in dots per inch) are further grouped into directories (so named because they were initially stored in file system directories). Each directory contains a database which lists the name of the font and information on how to find the font. The server uses these databases to translate font names (which have nothing to do with file names) into font data.

The list of font directories in which the server looks when trying to find a font is controlled by the font path. Although most installations will choose to have the server start up with all of the commonly used font directories, the font path can be changed at any time with the xset program. However, it is important to remember that the directory names are on the server's machine, not on the application's.

The default font path for the X server contains five directories:

/usr/lib/X11/fonts/misc

This directory contains many miscellaneous fonts that are useful on all systems. It contains a small family of fixed-width fonts in pixel heights 5 through 10, a family of fixed-width fonts from Dale Schumacher in similar pixel heights, several Kana fonts from Sony Corporation, a Kanji font, the standard cursor font, two cursor fonts from Digital Equipment Corporation, and OPEN LOOK cursor and glyph fonts from Sun Microsystems. It also has font name aliases for the font names fixed and variable.

/usr/lib/X11/fonts/75dpi

This directory contains fonts contributed by Adobe Systems, Inc., Digital Equipment Corporation, Bitstream, Inc., Bigelow and Holmes, and Sun Microsystems, Inc. for 75 dots per inch displays. An integrated selection of sizes, styles, and weights are provided for each family.

/usr/lib/X11/fonts/100dpi

This directory contains 100 dots per inch versions of some of the fonts in the 75dpi directory.

/usr/lib/X11/fonts/Type

contains IBM^®-Adobe scaled fonts.

/usr/lib/X11/fonts/Speedo

contains outline fonts for the Bitstream^® Speedo rasterizer. A single font face, in normal, bold, italic, and bold italic, is provided, contributed by Bitstream, Inc.

Font databases are created by running the mkfontdir program in the directory containing the source or compiled versions of the fonts (in both compressed and uncompressed formats). Whenever fonts are added to a directory, mkfontdir should be rerun so that the server can find the new fonts. To make the server reread the font database, reset the font path with the xset program.
For example, to add a font to a private directory, the following commands could be used:

% cp newfont.snf ~/myfonts
% mkfontdir ~/myfonts
% xset fp rehash

The xlsfonts program can be used to list all of the fonts that are found in font databases in the current font path. Font names tend to be fairly long as they contain all of the information needed to uniquely identify individual fonts.
However, the server supports wildcard searches on font names, so the full specification

   -adobe-courier-medium-r-normal--10-100-75-75-m-60-iso8859-1

   -*-courier-medium-r-normal--*-100-*-*-*-*-*-*

   *-courier-medium-r-normal--*-100-*

If more than one font in a given directory in the font path matches a wildcarded font name, the choice of which particular font to return is left to the server. However, if fonts from more than one directory match a name, the returned font will always be from the first such directory in the font path. The example given above will match fonts in both the 75dpi and 100dpi directories; if the 75dpi directory is ahead of the 100dpi directory in the font path, the smaller version of the font will be used.

Color names

Colors are usually specified by their commonly-used names (for example, red, white, or medium slate blue). The server translates these names into appropriate screen colors using a color database that can usually be found in /usr/lib/X11/rgb.txt. Color names are case-insensitive, meaning that red, Red, and RED all refer to the same color.

Many applications also accept color specifications of the following form:

#rgb
#rrggbb
#rrrgggbbb
#rrrrggggbbbb

where ``r'', ``g'', and ``b'' are hexadecimal numbers indicating how much red, green, and blue should be displayed (zero being none and ffff being on full). Each field in the specification must have the same number of digits (for example, #rrgb or #gbb are not allowed). Fields that have fewer than four digits (for example, #rgb) are padded out with zeroes following each digit (for example, #r000g000b000). The eight primary colors can be represented as:

black

#000000000000 (no color at all)

red

#ffff00000000

green

#0000ffff0000

blue

#00000000ffff

yellow

#ffffffff0000 (full red and green, no blue)

magenta

#ffff0000ffff

cyan

#0000ffffffff

white

#ffffffffffff (full red, green, and blue)

Unfortunately, RGB color specifications are highly unportable since different monitors produce different shades when given the same inputs. Similarly, color names are not portable because there is no standard naming scheme and because the color database needs to be tuned for each monitor. Application developers should take care to make their colors tailorable.

Keys

modifier list

Some keys (such as <Shift>, <Ctrl>, and <Caps Lock>) are known as modifiers and are used to select different symbols that are attached to a single key. For example, <Shift>A generates a capital A, and <Ctrl>L generates a formfeed character ^L. The server keeps a list of keycodes corresponding to the various modifier keys. Whenever a key is pressed or released, the server generates an event that contains the keycode of the indicated key as well as a mask that specifies which of the modifier keys are currently pressed. Most servers set up this list to initially contain the various <Shift>, <Ctrl>, and <Shift Lock> keys on the keyboard.

keymap table

Applications translate event keycodes and modifier masks into keysyms using a keymap table which contains one row for each keycode and columns for various modifier states. This table is initialized by the server to correspond to normal typewriter conventions, but it is only used by client programs.

Although most programs deal with keysyms directly (such as those written with the X Toolkit Intrinsics), most programming libraries provide routines for converting keysyms into the appropriate type of string (such as ISO Latin-1).

Options

-display display

specifies the name of the X server to use

-geometry geometry

specifies the initial size and location of the window

-bg color or -background color

specifies the color to use for the window background

-bd color or -bordercolor color

specifies the color to use for the window border

-bw number or -borderwidth number

specifies the width in pixels of the window border

-fg color or -foreground color

specifies the color to use for text or graphics

-fn font or -font font

specifies the font to use for displaying text

-iconic

indicates that the user would prefer that the application's windows initially not be visible as if the windows have been immediately iconified by the user. Window managers may choose not to honor the application's request.

-name

specifies the name under which resources for the application should be found. This option is useful in shell aliases to distinguish between invocations of an application, without resorting to creating links to alter the executable file name.

-rv or -reverse

indicates that the program should simulate reverse video if possible, often by swapping the foreground and background colors. Not all programs honor this or implement it correctly. It is usually only used on monochrome displays.

+rv

indicates that the program should not simulate reverse video. This is used to override any defaults since reverse video does not always work properly.

-selectionTimeout

specifies the timeout in milliseconds within which two communicating applications must respond to one another for a selection request

-synchronous

indicates that requests to the X server should be sent synchronously, instead of asynchronously. Since Xlib normally buffers requests to the server, errors do not necessarily get reported immediately after they occur. This option turns off the buffering so that the application can be debugged. It should never be used with a working program.

-title string

specifies the title to be used for this window. This information is sometimes used by a window manager to provide some sort of header identifying the window.

-xnllanguage language[_territory][.codeset]

specifies the language, territory, and codeset for use in resolving resource and other filenames

-xrm resourcestring

specifies a resource name and value to override any defaults. It is also very useful for setting resources that do not have explicit command line arguments.

Resources

that are read in from various places when an application is run. By convention, the application name is the same as the program name, but with the first letter capitalized (for example, Bitmap or Emacs) although some programs that begin with the letter ``x'' also capitalize the second letter for historical reasons. The precise syntax for resources is:

ResourceLine	= Comment | ResourceSpec
Comment	= ``!'' string | <empty line>
ResourceSpec	= WhiteSpace ResourceName WhiteSpace ``:'' WhiteSpace value
ResourceName	= [Binding] ComponentName {Binding ComponentName}
Binding	= ``.'' | ``*''
WhiteSpace	= {`` '' | ``\t''}
ComponentName	= {``a''-``z'' | ``A''-``Z'' | ``0''-``9'' | ``_'' | ``-''}
value	= string
string	= {<any character not including ``\n''>}

 +--------------+-------------------------------------------------------------+
 |ResourceLine  | = Comment | ResourceSpec                                    |
 +--------------+-------------------------------------------------------------+
 |Comment       | = ``!'' string | <empty line>                               |
 +--------------+-------------------------------------------------------------+
 |ResourceSpec  | = WhiteSpace ResourceName WhiteSpace ``:'' WhiteSpace value |
 +--------------+-------------------------------------------------------------+
 |ResourceName  | = [Binding] ComponentName {Binding ComponentName}           |
 +--------------+-------------------------------------------------------------+
 |Binding       | = ``.'' | ``*''                                             |
 +--------------+-------------------------------------------------------------+
 |WhiteSpace    | = {`` '' | ``\t''}                                          |
 +--------------+-------------------------------------------------------------+
 |ComponentName | = {``a''-``z'' | ``A''-``Z'' | ``0''-``9'' | ``_'' | ``-''} |
 +--------------+-------------------------------------------------------------+
 |value         | = string                                                    |
 +--------------+-------------------------------------------------------------+
 |string        | = {<any character not including ``\n''>}                    |
 +--------------+-------------------------------------------------------------+

To allow values to contain arbitrary octets, the 4-character sequence \nnn, where n is a digit in the range of 0-7, is recognized and replaced with a single byte that contains this sequence interpreted as an octal number. For example, a value containing a NULL byte can be stored by specifying ``\000.''

The Xlib routine XGetDefault and the resource utilities within Xlib and the X Toolkit Intrinsics obtain resources from the following sources:

RESOURCE_MANAGER root window property

Any global resources that should be available to clients on all machines should be stored in the RESOURCE_MANAGER property on the root window using the xrdb program. This is frequently taken care of when the user starts up X through the display manager or xinit.

application-specific files

Programs that use the X Toolkit Intrinsics will also look in the directories named by the XUSERFILESEARCHPATH and XAPPLRESDIR environment variables, plus directories in a standard place (usually under /usr/lib/X11/, but this can be overridden with the XFILESEARCHPATH environment variable) for application-specific resources. See the X Toolkit Intrinsics - C Language Interface manual for details.

XENVIRONMENT

Any user- and machine-specific resources may be specified by setting the XENVIRONMENT environment variable to the name of a resource file to be loaded by all applications. If this variable is not defined, a file named $HOME/.Xdefaults-hostname is looked for instead, where hostname is the name of the host where the application is executing.

-xrm resourcestring

Applications that use the X Toolkit Intrinsics can have resources specified from the command line. The resourcestring is a single resource name and value as shown above. Note that if the string contains characters interpreted by the shell (for example, asterisk), they must be quoted. Any number of -xrm arguments may be given on the command line.

Program resources are organized into groups called classes, so that collections of individual resources (each of which are called instances) can be set all at once. By convention, the instance name of a resource begins with a lowercase letter and class name with an uppercase letter. Multiple word resources are concatenated with the first letter of the succeeding words capitalized. Applications written with the X Toolkit Intrinsics will have at least the following resources:

background (class: Background)

specifies the color to use for the window background

borderWidth (class: BorderWidth)

specifies the width in pixels of the window border

borderColor (class: BorderColor)

specifies the color to use for the window border

Most applications using the X Toolkit Intrinsics also have the resource foreground (class: Foreground), specifying the color to use for text and graphics within the window.

By combining class and instance specifications, application preferences can be set quickly and easily. Users of color displays will frequently want to set Background and Foreground classes to particular defaults. Specific color instances such as text cursors can then be overridden without having to define all of the related resources. For example,

   bitmap*Dashed:  off
   XTerm*cursorColor:  gold
   XTerm*multiScroll:  on
   XTerm*jumpScroll:  on
   XTerm*reverseWrap:  on
   XTerm*curses:  on
   XTerm*Font:  6x10
   XTerm*scrollBar: on
   XTerm*scrollbar*thickness: 5
   XTerm*multiClickTime: 500
   XTerm*charClass:  33:48,37:48,45-47:48,64:48
   XTerm*cutNewline: off
   XTerm*cutToBeginningOfLine: off
   XTerm*titeInhibit:  on
   XTerm*ttyModes:  intr ^c erase ^? kill ^u
   XLoad*Background: gold
   XLoad*Foreground: red
   XLoad*highlight: black
   XLoad*borderWidth: 0
   emacs*Geometry:  80x65-0-0
   emacs*Background:  #5b7686
   emacs*Foreground:  white
   emacs*Cursor:  white
   emacs*BorderColor:  white
   emacs*Font:  6x10
   xmag*geometry: -0-0
   xmag*borderColor:  white

This is frequently how user-friendly startup scripts merge user-specific defaults into any site-wide defaults. All sites are encouraged to set up convenient ways of automatically loading resources. See the Xlib manual section ``Using the Resource Manager'' for more information.

Examples

Diagnostics

The default error handler in Xlib (also used by many toolkits) uses standard resources to construct diagnostic messages when errors occur. The defaults for these messages are usually stored in /usr/lib/X11/XErrorDB. If this file is not present, error messages will be rather terse and cryptic.

When the X Toolkit Intrinsics encounter errors converting resource strings to the appropriate internal format, no error messages are usually printed. This is convenient when it is desirable to have one set of resources across a variety of displays (for example, color vs. monochrome, lots of fonts vs. very few, etc.), although it can pose problems for trying to determine why an application might be failing. This behavior can be overridden by setting the StringConversionsWarning resource.

To force the X Toolkit Intrinsics to always print string conversion error messages, the following resource should be placed at the top of the file that gets loaded onto the RESOURCE_MANAGER property using the xrdb program (frequently called .Xresources or .Xres in the user's home directory):

   *StringConversionWarnings: on

   xterm*StringConversionWarnings: on

See also

Xlib -- C Language X Interface, X Toolkit Intrinsics -- C Language Interface and Using and Specifying X Resources