The GAP 4 package 'XGAP'
------------------------

XGAP provides a graphical user interface for GAP based on the X Window system.


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Installing XGAP

Installing XGAP should be easy once you have installed GAP itself. We
assume here that you want to install XGAP in its standard location,
which is in the ``pkg'' subdirectory of the main GAP4 installation.

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Overview

You have to perform the following steps to install XGAP:

-- Get the sources
-- Unpack the sources
-- Use the <configure> script to adjust everything to your specific system
-- Compile the C part of XGAP
-- Edit a certain startup script (if necessary) and install it in 
   an executable location in your system

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What you need to install XGAP

Being a graphical user interface to GAP, XGAP of course needs
graphics. At the moment this means that you need the X window system in the 
Version 11 Release 5 or newer. On the other hand the type of Unix you use 
should not matter. Please file an issue report on
  https://github.com/gap-packages/xgap/issues
if you encounter problems with certain system configurations.
Note that usage on 
a computer running Microsoft Windows is not officially supported. 
See the file `xgap/README.Windows' for a report how it could
still work on Windows. 

Because XGAP contains a C-part you need a C compiler.

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Getting and unpacking the sources

In most cases, the XGAP package will already be included in the main
distribution. However, you can also download the sources of the latest
version from

https://gap-packages.github.io/xgap/

You need only one file with the name `xgap-4.32.tar.gz`
which is in the subdirectory for the packages.
You now change your current directory to the `pkg' subdirectory of the 
location where you installed
GAP
Now you extract the sources for the XGAP package:

# tar xzvf xgap-4.32.tar.gz
...

The <tar> utility unpacks the files and stores them into the appropriate
subdirectories. XGAP resides completely in the following subdirectory
(assuming standard location):

gap4r8/pkg/xgap

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Configuring and Compiling the C part

You have to change your current working directory to the ``xgap''
subdirectory. You do this by

# cd xgap-4.32

if your current working directory is the one, where you used
<tar>. There you invoke the <configure> script by:

# ./configure
creating cache ./config.cache
checking for make... make
checking build system type... x86_64-unknown-linux-gnu
checking host system type... x86_64-unknown-linux-gnu
checking target system type... x86_64-unknown-linux-gnu
checking for gcc... gcc
checking whether the C compiler (gcc  ) works... yes
checking whether the C compiler (gcc  ) is a cross-compiler... no
checking whether we are using GNU C... yes
...
updating cache ./config.cache
creating ./config.status
creating Makefile
creating xgap.sh

$\ldots$ indicate omissions. 
This script tries to determine, which kind of operating system and
libraries you have installed and configures the source
accordingly. Normally this should produce some output but no error
messages. 

Note that you can add ``CONFIGNAME=default64'' after the <./configure>
command (with ``default64'' replaced by a configuration name you used
to compile GAP with) to compile for a different than the standard
configuration.

The last step of the script produces some makefiles which are
used to compile the code. You do this by typing

# make
mkdir -p bin/x86_64-unknown-linux-gnu-gcc
cp cnf/configure.out bin/x86_64-unknown-linux-gnu-gcc/configure
( cd bin/x86_64-unknown-linux-gnu-gcc ; CC=gcc ./configure  )
checking for gcc... gcc
checking whether the C compiler works... yes
...
creating ./config.status
creating Makefile
creating config.h
( cd bin/x86_64-unknown-linux-gnu-gcc ; make CC=gcc )
make[1]: Entering directory 
`/scratch/neunhoef/4.0/pkg/xgap/bin/x86_64-unknown-linux-gnu-gcc'
gcc -I. -g -O2   -o xcmds.o -c ../../src.x11/xcmds.c
...
make[1]: Leaving directory \                    # line broken for this manual!
     `/usr/local/lib/gap4/pkg/xgap/bin/i686-unknown-linux2.0.34-gcc'

(a few lines were broken for typesetting purposes in this manual, the
position is marked by a backslash) 

Now all C sources are compiled and a binary executable is built. It is
stored in a subdirectory of the ``bin'' subdirectory in your ``xgap''
directory. The name of this location has something to do with your
installation. It could for example be

bin/x86_64-unknown-linux-gnu-gcc/xgap

if you compile on a 64-bit Linux system using the GNU-C-Compiler.

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Installing the Startup Script

To make the startup of XGAP more convenient there is a startup script
which contains also some configuration information like the position of
your GAP installation. It is in the ``xgap'' directory
and is called ``xgap.sh''. This file is automatically generated
by the `configure' script and normally you should *not* have to change 
anything in it. Just copy it to some location that people have in their
``PATH'' environment variable, for example to ``/usr/local/bin''.
This completes the installation.

If you want to change anything in the installation, you
can also edit the script until the line

##  STOP EDITING HERE !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

You can specify the directory where GAP is installed (``GAP_DIR''), the
name of the GAP-executable (``GAP_PRG'') and the name of the
XGAP-executable (``XGAP_PRG''). The first three are exactly the same
things that you could edit in the main GAP startup script. After that
you have the possibility to control the behaviour of the XGAP startup
script. You can specify whether XGAP goes into the background
(``DAEMON'') and whether it prints out information about its parameters
(``VERBOSE''). Note that it is possible to combine ``DAEMON=YES'' and
``VERBOSE=YES'' because the script actually runs in the foreground and
only the C program is put into the background.


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Installing in a different than the standard location

It could happen that you do not want to install XGAP in its
standard location, perhaps because you do not want to bother your
system administrator and have no access to the GAP directory. In
this case you can unpack XGAP in any other location within a
``pkg'' directory with the <tar> command as described above. Let us
call this directory ``pkg'' for the moment. You get an ``xgap''
subdirectory with all the files of XGAP in it. You follow the
standard procedure with one exception:

In the ``./configure'' command, add the following option:

./configure --with-gaproot=/usr/local/lib/gap4r8

if ``/usr/local/lib/gap4r8'' is the location of the main GAP installation.

You can find out where the main GAP4 installation is by starting 
GAP as usual and looking at the variable `GAPInfo.RootPaths' 
within GAP.