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  <tmdoc-title|Example of a plug-in with <scheme> code>

  <paragraph*|The <verbatim|world> plug-in>

  Consider the <verbatim|world> plug-in in the directory

  <\verbatim>
    \ \ \ \ $TEXMACS_PATH/examples/plugins
  </verbatim>

  This plug-in shows how to extend <TeXmacs> with some additional <scheme>
  code in the file

  <\verbatim>
    \ \ \ \ <example-plugin-link|world/progs/init-world.scm>
  </verbatim>

  In order to test the <verbatim|world> plug-in, you should recursively copy
  the directory

  <\verbatim>
    \ \ \ \ $TEXMACS_PATH/examples/plugins/world
  </verbatim>

  to <verbatim|$TEXMACS_PATH/plugins> or <verbatim|$TEXMACS_HOME_PATH/plugins>.
  When relaunching <TeXmacs>, the plug-in should now be automatically
  recognized (a <menu|World> menu should appear in the menu bar).

  <paragraph*|How it works>

  The file <verbatim|init-world.scm> essentially contains the following code:

  <\scm-code>
    (define (world-initialize)

    \ \ (display* "Using world plug-in!\\n"))

    \;

    (plugin-configure world

    \ \ (:require #t)

    \ \ (:initialize (world-initialize)))
  </scm-code>

  The configuration option <scm|:require> specifies a condition which needs
  to be satisfied for the plug-in to be detected by <TeXmacs> (later on, this
  will for instance allow us to check whether certain programs exist on the
  system). The configuration is aborted if the requirement is not fulfilled.

  The option <scm|:initialize> specifies an instruction which will be
  executed during the initialization (modulo the fulfillment of the
  requirement). In our example, we just send a message to the standard output
  that we are using our plug-in. In general, the initialization routine
  should be very short and rather load a module which takes care of the real
  initialization. Indeed, keeping the <verbatim|init-<em|myplugin>.scm> files
  simple will reduce the startup time of <TeXmacs>.

  <tmdoc-copyright|1998--2002|Joris van der Hoeven>

  <tmdoc-license|Permission is granted to copy, distribute and/or modify this
  document under the terms of the GNU Free Documentation License, Version 1.1
  or any later version published by the Free Software Foundation; with no
  Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
  Texts. A copy of the license is included in the section entitled "GNU Free
  Documentation License".>

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  <\collection>
    <associate|language|english>
  </collection>
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