OVERVIEW OF X INTERFACES
R. Evans, Adrian Howard Feb 1992 Revised John Gibson May 1993
COPYRIGHT University of Sussex 1993. All Rights Reserved.
X is a large and complicated emerging standard for user interface software on high resolution displays. From V14, Poplog provides specific support for operation under X, in particular (but not only) an application programmer's interface to the X Toolkit. This file discusses the overall organisation of X facilities, and provides cross-references to more specific documentation of individual packages.
Select headings to return to index
Many of the documentation cross-references in this file refer to X-specific REF files. These will only be easily accessible after you have loaded LIB * POPXLIB. If you are reading this file from Ved, you are therefore advised to load this library now, even if you are only browsing the documentation. Simply type
<ENTER> uses popxlib
Note also that the addition of X-related facilities to Poplog have increased the need for mixed-case library and documentation filenames. This is somewhat at odds with previous conventions for filename references, which have used all-uppercase (for prominence in the text) to refer to all-lowercase actual filenames. To retain compatibility, text references in all-uppercase refer to all-lowercase files, but mixed-case references should be taken as verbatim. This strategy does not cope with all-uppercase filenames, and for this reason such filenames have been (and should be by users) avoided.
X is a specification for the user-interface component of programs which wish to use typical workstation hardware (high resolution screen, keyboard and mouse.) The idea is to provide facilities for many programs to use the same screen, keyboard and mouse simultaneously, and the standardisation required to offer a high degree of portability between different hardware.
An implementation of X is a software package typically comprising two main parts. Firstly, software for a self-contained program called an 'X server' which maintains complete control over the screen, keyboard and mouse. Secondly software libraries designed to form part of programs, called 'X clients', which wish to make use of these user-interface facilities. It is largely this latter component that is of interest here. The facilities discussed below allow Poplog to operate as an X client of an X server which is managing the actual user-interface hardware.
X was originally developed in a research project based at MIT. However development involved a number of major computer manufacturers, and the system is rapidly becoming a standard for user-interface software. It is supported by many of the main workstation producers and in particular, most of the main Poplog platforms (including Sun, Hewlett-Packard and DEC workstations). Hence from V14 Poplog includes a range of facilities for interfacing to X at different levels.
The basis of X Windows operation is that all access to user-interface hardware by 'ordinary' user programs is mediated by the X server. So any program desiring user-interface facilities obtains them by becoming an X client, that is, establishing a communication link (called a 'connection') to an X server (or possibly more than one, an X client can use more than one screen.) X servers and clients communicate using a byte-stream protocol: messages between them consist of sequences of bytes, coded to represent commands, requests and replies. Examples of messages from client to server include "Create a new window on the screen", "Tell me what fonts are available", "Write text at this location in this window", "Display this bitmap image". Examples of messages from server to client include "The user just pressed the 'A' key in this window", "This window has just become visible - please refresh it", "The mouse cursor just entered this window".
In principal, an X client can operate directly at this level, by simply opening a connection to a server, and talking in terms of the low level protocol. The advantage of this level of interface is complete independence of all the design assumptions, restrictions and possible bugs of the higher level support. The disadvantage is that all the client software must be written from scratch, and common ground with other X software is minimal. An example of such an interface is the CLX package, which provides Common Lisp functions for controlling the user-interface, and converts them directly into X server messages. CLX is available under Poplog Common Lisp (see 'Poplog and CLX' below), and so using these facilities Poplog can operate as a low level X client of this sort.
X offers two layers of higher level support as part of the standard. Both are provided in the form of C libraries which can be incorporated into other programs.
The lower of these two levels is called 'Xlib', and consists of a large number of procedures, each roughly corresponding to the sending of a protocol message to the server. This level avoids the need to explicitly code up and dispatch protocol messages, and supports decoding and queuing of incoming messages from the server. It provides a purely procedural interface, but at about the same level of functionality as the protocol language itself. Thus it offers flexible and portable support for application programs, but still requires substantial low level user-interface programming, even for quite simple applications. The Poplog library LIB * XLIB (see Poplog and Xlib below) provides a basic interface to this level, implemented via LIB * NEWEXTERNAL.
In fact, the X Toolkit level itself divides into two parts. It provides facilities for creating new classes of user-interface object (called widget classes) --- for example, defining a new kind of scrollbar. This is generally called 'widget class programming' and currently there is no specific support for it in Poplog. The Toolkit also provides facilities for using and customising predefined user-interface objects, for example setting up a menu. This is generally called 'application programming' and is supported in Poplog, and indeed is the primary component of Poplog's current X Windows support (see Poplog and the X Toolkit below).
However, application programming using the X Toolkit clearly needs some predefined widget class definitions to be available to the programmer. The X Toolkit standard itself includes only a few very basic widget class definitions, solely to support more sophisticated definitions supplied independently by widget class programmers. Widget class definitions tend to be grouped into sets (called widget sets), and a particular software supplier will supply a widget set (generally in the form of a C library) providing user-interface objects conforming to that supplier's look and feel (that is, visual appearance and conventions about keyboard and mouse button usage etc.) Poplog provides support for accessing such externally defined widget sets generally, and detailed support for a number of available widget sets (see Widget Set Interfaces below.)
In addition, Poplog includes a widget set specifically designed to cover some basic interface needs for Poplog applications. This widget set, called Xpw, takes the form of a C library archive (included with Poplog), and provides simple text and graphics facilities under X Windows (see The Poplog Widget Set: Xpw below). These facilities are sufficient for a wide range of common requirements, allowing Poplog applications to be constructed without any externally supplied widget set definitions (see TEACH * RC_GRAPHIC for examples using the Poplog widget set).
Finally, in addition to these various direct interfaces to an X server, Poplog can be run 'inside X', but without actually being an X client. Most X implementations include programs which act as terminal emulators. That is, they are X client programs which create a single window on the screen which functions just as if it were an ordinary terminal. Examples of such programs include 'xterm', 'cmdtool', 'shelltool' and 'hpterm'. Such programs allow Poplog to be run just as if it was run from a terminal. Nevertheless, some aspects of Poplog's operation, most notably Ved customisation, need to be sensitive to the fact that Poplog is running under X. To accommodate this, Poplog includes support for this aspect of interaction with X (see Ved and X below).
It will be clear from the preceding discussion, that there are a number of ways a Poplog system might operate as an X client. Indeed as well as the standard interface layers discussed above, there are already other defined interfaces and toolkits (such as Sun's 'XView' library) which might be candidates for a Poplog interface, and doubtless more possibilities will emerge in the future. It is important, therefore, to distinguish between generic aspects of Poplog's X interface (that is, the small number of facilities intended to accommodate any chosen X interface package), and aspects which are specific to a particular chosen interface. This is particularly relevant to discussion of the X Toolkit interface, this is the primary supported interface in Poplog and some system hooks (eg sysxsetup, see REF * SYSTEM) assume it by default. But it is just one possible interface, and ultimately the generic X support does not favour it over any other.
Generally speaking, the identifiers associated with the generic facilities contain a lower case 'x' in their name. This distinguishes them from other X facilities, for example the X Toolkit identifiers have 'Xt' or 'Xpt' as a prefix. (REF * XTOOLKIT has a section describing the naming conventions used by the toolkit interface.)
The first of the generic X facilities provided in Poplog is a mechanism for specifying that X is present (and hence that an X interface can sensibly be activated), and for passing parameters to that interface, for example from the command line. This mechanism centres on the system variable popunderx, and is described fully in REF * SYSTEM. The variable popunderx is initially false, but if set to a non-false value, it indicates that Poplog is running under X, and various system hooks (described below) use this to compile X-specific initialisation files, run X-specific startup routines, and so forth. Furthermore, the value of popunderx (when non-false) may be used to provide initialisation parameters for X interface startup.
popunderx can be set in one of two ways:
(1) From the command line: Invoking Poplog with the %x flag (for details see REF * SYSTEM). In this case its value can be set to a list of string parameters, using the "( ... )" syntax described in REF * SYSTEM. For example the Unix shell command:
% pop11 %x \( -display mysun -font 6x10 \)
will cause Poplog to start up in pop11 with popunderx set to
['-display' 'mysun' '-font' '6x10']
If no parenthesised arguments are specified, popunderx is set to , indicating the presence of X, but with no initial parameters. Note that all the standard Poplog startup commands, ved, prolog, clisp etc.., respect the %x flag in this way.
(2) By a user or library program: popunderx is a perfectly ordinary variable which can be set manually to influence X startup. Of course, the value assigned must make sense to the X interface package in use. For example the X Toolkit interface expects a (possibly empty) list of strings as would have been passed on the command line as above. Also the assignment must occur before any X-related system hooks are run if it is to have its proper effect. (Note: the user's init.p file is compiled before any such X-related hooks are encountered, so manual setting of popunderx in init.p will catch them all correctly).
It is worth noting that it is not possible for Poplog to automatically determine that X support is required: X clients can be run on machines with no local X server support at all, communicating with a remote server over a network, and conversely a user running X might want to run Poplog without any X features.
Also X interfaces themselves should generally not depend on popunderx being set: if it is set then they may use its value for initialisation information, but they should work if initialised directly even if popunderx is false.
While setting popunderx is an indication that X support is required, it does not itself cause any X-related activity. It merely causes some standard Poplog system hooks to run X-specific variants (thus syssetup will run sysxsetup etc.). This section describes those X-specific variants and the contexts in which they are called.
initx.p [file] If popunderx is non-false, and the %noinit flag (for details see REF * SYSTEM) is not specified, then sysinitcomp will look for the file '$popsys/initx.p' and compile it if found, and then '$poplib/initx.p' and compile it if found. If the latter file is not found, it will look for 'initx.p' in the current directory and compile it if found. This process takes place after compilation of the corresponding 'init.p' files.
xpopexit [procedure variable]
If popunderx is non-false, this procedure is called by sysexit, just after popexit.
A single library in the main Pop-11 library directory is intended to provide the initial access point for all Poplog X facilities. This library is called LIB * POPXLIB (ie '$usepop/pop/lib/lib/popxlib.p') and will need to be compiled by almost any user of any of the X facilities discussed here.
LIB * POPXLIB extends Poplog's various search paths with additional directories containing X-specific files. Thus the X autoloadable directory is added to popautolist, the X library directory to popuseslist, the X help directory to vedhelplist etc.. Once this has been done, most of the X facilities become directly accessible. (Note: many of the REF files referred to in this file are X-specific, and so will only be found after
has been run. So even if you are just browsing the X documentation, you will need to have loaded this library.)
LIB * POPXLIB obtains all of the potentially site-specific information it needs from the include file INCLUDE * XDEFS. The default INCLUDE * XDEFS file defines a set of constants giving the location of X facilities within Poplog, and probably will not need alteration in most cases. If needed, it can be customised to the local site requirements; the recommended way to achieve this it to make a copy of $usepop/pop/lib/include/xdefs.ph called $poplocal/local/include/xdefs.ph (which will then override the system one), and then edit in appropriate local changes.
XPOP -> filename [constant]
The directory contain all the X-specific files within the main Poplog tree. Default '$usepop/pop/x'.
XPOPSTB -> filename_or_false [constant]
If non-false, this is the name of the 'stb' file to be used with Poplog when running under X. By default the X code is linked into the standard Poplog image, and the standard stb file can be used. However some sites may wish to have two separate Poplog executables, one without X (and hence smaller) and one with X. This can be achieved by renaming the executable linked WITH X to a new name (say 'xpop11'), and defining this constant to be the FULL-PATHNAME of the .stb file (say 'xpop11.stb') created by the link process. Running LIB * POPXLIB will then set $popexlinkbase to the correct stb file for external loading (see REF * EXTERNAL).
XPOPBIN -> filename [constant]
The directory containing X-specific binaries (the Xpw archive, etc.). Default <XPOP>/bin.
XPOPAUTO -> filename [constant]
The directory containing X-specific Pop-11 autoloadable libraries. Default <XPOP>/pop/auto.
XPOPLIB -> filename [constant]
The directory containing X-specific Pop-11 non-autoloadable libraries. Default <XPOP>/pop/lib.
XPOPXLIB -> filename [constant]
The directory containing the 'Xlib' libraries. Default <XPOPLIB>/xlib.
XPOPINCLUDE -> filename [constant]
The directory containing X-specific Pop-11 include files (but NOT INCLUDE *XDEFS !). Default <XPOP>/pop/include.
XPOPHELP -> filename [constant]
The directory containing X-specific Pop-11 HELP files. Default <XPOP>/pop/help.
XPOPTEACH -> filename [constant]
The directory containing X-specific Pop-11 TEACH files. Default <XPOP>/pop/teach.
XPOPDOC -> filename [constant]
The directory containing X-specific Pop-11 DOC files. Default <XPOP>/pop/doc.
XPOPREF -> filename [constant]
The directory containing X-specific Pop-11 REF files. Default <XPOP>/pop/ref.
XPOPSRC -> filename [constant]
The directory containing X Toolkit interface source files (not available on all systems). Default <XPOP>/pop/src.
XPOPDEMO -> filename [constant]
The directory containing X-specific Pop-11 demos. Default <XPOP>/pop/demo.
The standard Poplog image (e.g. as created by the * NEWPOP link step) will include support for X (unless you override it with the NEWPOP nox option, for example). Linking for X requires access to your system's X Toolkit and Xlib archive libraries.
Because the names and locations of these libraries are highly system-dependent, the way in which a Poplog image is linked for X is controlled by Unix environment variable settings (logical name translations in VMS), containing specifications of the form
x= xtype / xversion : library-arguments
(the information in these specifications is described more fully under * sys_translate_exlibs below). For example, in Unix:
setenv POP_XOL_EXLIBS \ "x=openlook/3000: -L$OPENWINHOME/lib -lXol -lXt -lX11"
and in VMS:
define POP_XM_EXLIBS - "x=motif/1001: sys$share:decw$xmlibshr/shareable"
As the examples illustrate, the variable names have the form
where XPREFIX is a short prefix corresponding to the X link type. NEWPOP may be given an argument -xprefix (i.e. the same in lowercase) to specify that the X link type should be taken from the corresponding variable.
The default used by NEWPOP (and other parts of the system) is the variable POP_XLINK_EXLIBS (i.e. -xlink): this may specify the information explicitly, but more usually `dereferences' to another variable, by having a translation starting with "==", e.g.
setenv POP_XLINK_EXLIBS "==POP_XOL_EXLIBS" (Unix) define POP_XLINK_EXLIBS "==POP_XM_EXLIBS" (VMS)
The Poplog login shell script files
$popcom/popenv (Unix) popcom:popenv.com (VMS)
(which are sourced automatically by $popcom/poplog etc) provide default host-specific definitions for the following variables:
POP_XM_EXLIBS (Motif) POP_XOL_EXLIBS (OpenLook) POP_XT_EXLIBS (MIT) POP_XLINK_EXLIBS (== default)
Note that while POP_XM_EXLIBS and POP_XOL_EXLIBS may be set to something on a particular system, this does not imply that Motif or OpenLook, etc is actually available on that system. POP_XLINK_EXLIBS is always set for the appropriate host system default. If required, you can override any of these settings in your own local files, i.e.
$poplocal/local/com/popenv (Unix) poplocal:[local.com]popenv.com (VMS)
The information from the X link specification is made available in the run-time system by the following identifiers:
XLINK_TYPE -> string [constant]
popxlink_motif -> true [constant]
popxlink_openlook -> true [constant]
popxlink_mit -> true [constant]
These constants are defined if and only if the Poplog image was linked with the X part of the system.
XLINK_TYPE contains a string describing which X system the image was linked against (i.e. relating to the value of XLINK_EXLIBS, see below). At the same time, the constant
is also defined, with value true.
Standard values for XLINK_TYPE include:
'motif' XLINK_EXLIBS includes the Motif widget set library.
'openlook' XLINK_EXLIBS includes the OpenLook widget set library.
'mit' XLINK_EXLIBS contains only the standard MIT X Toolkit libraries.
XLINK_VERSION -> int [constant]
This constant is defined only if the Poplog image was linked with the X part of the system (and then only if the X link specification supplied it). It represents the version of the libraries specified in XLINK_EXLIBDIRS/XLINK_EXLIBFILES.
It usually has the form
(major-release-number * 1000) + minor-release-number
However, being X implementation-specific, this is meaningful only in relation to XLINK_TYPE; you should therefore NOT use XLINK_VERSION directly, but instead use the corresponding widgetset identifier, e.g. XOL_VERSION, XM_VERSION, etc.
XLINK_EXLIBDIRS -> string_list [variable]
XLINK_EXLIBFILES -> string_list [variable]
XLINK_EXLIBS -> string_list [variable]
These variables are only defined in a Poplog image linked with X, and contain lists of strings describing the X Toolkit and Xlib library archives against which the image was linked. Their contents are system-dependent.
XLINK_EXLIBDIRS contains any preceding Unix '-L' directory specifications, e.g.
[ '-L/usr/openwin' ]
This is always  in VMS.
XLINK_EXLIBFILES contains the actually library file arguments, e.g.
[ '-lXol' '-lXt' '-lX11' ]
in Unix, or
[ 'sys$share:decw$xmlibshr/share' ]
XLINK_EXLIBS is an autoloadable variable which is a concatention of the other two via their identifiers, i.e.
[% ident XLINK_EXLIBDIRS, ident XLINK_EXLIBFILES %]
Thus when used as an external library list to exload, XptLoadProcedures, etc, the identifiers are dereferenced to produce the composite list, and will automatically include any additions you might have made to XLINK_EXLIBDIRS or XLINK_EXLIBFILES after system startup.
XLINK_EXT_EXLIBS -> string_list [variable]
This is an autoloadable list of additional external libraries to be used (in exload, XptLoadProcedures, etc) when externally loading MIT toolkit extensions. Its default value for Unix systems is
[ '-lXmu' '-lXext' ]
[ 'decw$xmulibshr/share' 'decw$xextlibshr/share' ]
sys_translate_exlibs(varname) -> (xtype, xversion, exlibs) [procedure]
This procedure takes a Unix environment variable or VMS logical name varname (a string), and returns its translation from systranslate as a list of external library file strings. In addition, if the translation is a Poplog X link specification, the type and version from that are returned as well.
First, if the translation string trans begins with '==', the remainder of trans is assumed to be another environment variable/logical name, and the results are the recursive translation of that variable with sys_translate_exlibs.
Otherwise, if trans does not begin with 'x=', the xtype and xversion results are both false, and the exlibs result is
i.e. the list of strings got by splitting trans at whitespace boundaries.
X Link Specification -------------------- However, if trans begins with 'x=', it is taken to be a Poplog X link specification of the form
x= xtype / xversion : library-arguments
(where the '/ xversion' and ': library-arguments' parts, and spaces between the parts, are optional).
xtype This field is a single keyword used to identify the particular X implementation against which the image was linked, and is returned as the xtype result (a string).
(When used by the Poplog linker, this information is made available in the running image as the string value of the constant XLINK_TYPE. In addition, the constant popxlink_xtype is also defined, with value true.)
xversion This field gives the version number of the X implementation, usually defined as:
(major-release-number * 1000) + minor-release-number
This information can be omitted; if present, it is returned as the xversion result (an integer), otherwise false.
(When used by the Poplog linker, this information if present is made available in the running image as the value of the constant XLINK_VERSION.)
library-arguments This field is some arbitrary sequence of arguments, returned in the exlibs result as
i.e. the list of strings got by splitting it at whitespace boundaries.
(When used by the Poplog linker, this information is passed to the operating-system linker, and identifies the particular X libraries to use. The information is also made available in the running image as the value of the variables XLINK_EXLIBDIRS and XLINK_EXLIBFILES -- see above.)
Examples -------- See the introduction to this section above for a description of the naming conventions for X link environment variables, and other example settings.
The most basic X configuration would be:
x= mit : -lXt -lX11 (Unix) x= mit : sys$share:decw$xtshr/shareable (VMS)
The xtype and xversion fields can have any values; however, there are three xtypes for which the corresponding popxlink_xtype identifier is tested for in the Poplog X libraries:
motif implies use of the Motif Widget Set and Toolkit
openlook implies use of Sun's OLIT
mit implies use of a standard MIT distribution
The :library-arguments part is optional: In Unix, omitting this is only meaningful if all the relevant X libraries are in the standard directories (/lib, /usr/lib, and /usr/local/lib), or the LD_LIBRARY_PATH environment variable is set appropriately. It is usually more reliable to supply specific -L directory qualifiers, e.g. to use Version 2.5 of OLIT without necessarily running in the OpenWindows environment:
x= openlook/2005: -L/usr/openwin/lib -lXol -lXt -lX11
In VMS, you should always supply :library-arguments giving the relevant DECwindows shareable image(s).
It is expected that most Poplog applications will make use of the X Toolkit to implement X based user interfaces. For this reason, Poplog provides an extensive application programmer's interface to the X Toolkit. The entry point into reference documentation for this interface is REF * XTOOLKIT. Tutorial introductions to some of the facilities can be found in TEACH * XTOOLKIT, TEACH * Xpw, TEACH * RC_GRAPHIC (which use the Poplog widget set, available on all systems), TEACH * MOTIF (for those with access to the Motif widget set), and TEACH * OPENLOOK (for those with access to the OLIT widget set, available under Sun's OpenWindows system).
No explicit support for widget class programming is available yet, although all of the low-level primitives required are present in Poplog V14.
Predefined C widget classes can be externally loaded like any other external data. However, Poplog provides direct support for the Poplog, Motif, OLIT and Athena widget sets -- see Widget Set Interfaces in REF * XT_LIBS for more details, as well as
The Poplog widget set is a small collection of simple widget classes provided with Poplog (although written in C). It includes general purposes graphics and text handling widgets, aimed to support simple graphics and bitmap operations, and multi-window Ved.
The Poplog widget set is available on all X-supported platforms, and is self-contained (aside from the standard toolkit facilities), allowing a range of applications to be constructed (see TEACH * RC_GRAPHIC for examples of use).
The Xpw documentation presupposes knowledge of the general X toolkit interface, and the entry point is HELP * Xpw. A tutorial introduction can be found in TEACH * Xpw.
LIB * XLIB (see HELP * XLIB) provides access to a collection of libraries which externally load the Xlib interface layer to X Windows. This provides a full interface to Xlib, defined in terms of LIB * NEWEXTERNAL (see HELP * NEWEXTERNAL). This interface is not integrated into Poplog to the same extent as the Toolkit interface --- for example the data structure management is purely as provided by LIB * NEWEXTERNAL and event handling must be catered for explicitly.
Nevertheless there is a degree of interchangeability between the two. The external-class data structures of either will be acceptable for the other, IF type checks are bypassed. Thus it is quite feasible to use this Xlib interface with care to augment Toolkit functionality if desired.
It is anticipated that the Xlib and Xt interfaces will be more closely integrated in future releases of Poplog.
From Version 14.1, Poplog includes a multi window X based version of the Ved editor called XVed. See TEACH * XVED for details.
Use of terminal Ved under X operates largely independently of other notions of running Poplog as an X client. That is, if X terminal emulators are available (as they are in most X implementations), Poplog can be run within X just as it would be on a terminal, and this is quite independent of whether such a Poplog instance is itself an X client. Nevertheless, Ved needs to be customised to operate in this scenario, and such customisation is X-dependent in the sense that the terminal emulator in use will generally be part of the X system.
A Ved customisation for the most common of such X terminal emulators, 'xterm' is currently available. (Customisations for other terminal emulators will be provided in the near future.) This customisation is contained in LIB * VEDXTERM and documented in HELP * VEDXTERM.
An additional library for use with LIB * VEDXTERM which allows the mouse buttons to act like function keys is provided by LIB * VEDXGOTOMOUSE (See SHOWLIB * VEDXGOTOMOUSE).
(1) To take full advantage of these terminal emulators, in particular of the function keys available on the range of possible keyboards, some site-specific customisation of the X system is desirable. These are discussed in HELP * VEDXTERM.
(2) xterm is unfortunately not available under all X systems. It is present in the MIT distribution, and exists in the 'demo' directory of the OpenWindows 2.0 (SunOS 4.1.1) system. Users of other terminal emulators may find suitable 'generic' Ved customisations work (VT100 emulations are common, for example - see HELP * VT100, HELP * VEDVT100).
CLX (see HELP * CLX from within Common Lisp) is essentially a stand-alone Common-Lisp interface to X Windows, with probably no overlap with the other X facilities described here. It establishes its own connection to the server, has its own data structures and procedures and is completely Lisp oriented. It is available to Poplog users as a package in the 'contrib' area (see HELP * CONTRIB)
Poplog V14 does not provide any explicit support for a Prolog interface to X Windows. However a prototype of a package offering a Prolog interface to the Poplog Widget Set can be found in the contrib area, see '$popcontrib/x/prolog/xpw/README' for more information.
The Poplog X interfaces are just that - interfaces to code produced by third parties. Some of this code is public domain, some of it is proprietary. Almost all of it is covered by copyrights, warranty and liability limitations and sometimes restrictions on use. It is the user's responsibility to ensure that their use of such software in conjunction with Poplog does not violate any of these restrictions. The University of Sussex, Integral Solutions Ltd., and their appointed agents offer no warranty and accept no liability for the use of such third party code. The provision of interface support within Poplog should not be taken as an indication that the relevant third party software is present, supported or legally available for use.
Much of the documentation on the Poplog/X interface is based on the following documentation:
Xlib - C Language X Interface, MIT X Consortium Standard, X Version 11, Release 4 Copyright (C) 1985, 1986, 1987, 1988, 1989 Massachusetts Institute of Technology, Cambridge, Massachusetts, and Digital Equipment Corporation, Maynard, Massachusetts.
X Toolkit Intrinsics - C Language Interface X Window System X Version 11, Release 4 Copyright (C) 1985, 1986, 1987, 1988, Massachusetts Institute of Technology, Cambridge, Massachusetts, and Digital Equipment Corporation, Maynard, Massachusetts.
We have used this material under the terms of its copyright which grants free use under the following conditions:
"Permission to use, copy, modify and distribute this documentation [ie. those volumes listed above] for any purpose and without fee is hereby granted, provided that the above copyright notice appears in all copies and that both the copyright notice and this permission notice appear in supporting documentation, and that the name of M.I.T. or Digital not be used in advertising or publicity pertaining to distribution of the software without specific, written, prior permission. M.I.T. and Digital makes no representations about the suitability of the software described herin for any purpose. It is provided "as is" without express of implied warranty."
DOC * XBIBLIOGRAPHY A comprehensive list of X publications HELP * X General pointers for the Poplog/X interface
--- C.all/ref/x --- Copyright University of Sussex 1993. All rights reserved.