This directory contains plug-in examples in various languages.  All source
files here are in the public domain.

In order to be found by the plugin-proxy module, they would be installed under
$(libexecdir)/gwyddion/plugins.  However, they are only distributed as
documentation because (a) the plug-in mechanism has been deprecated for more
than a decade (b) registering all the stuff with plugin-proxy would be one of
the slowest things doing during Gwyddion startup, despite also being almost
entirely useless.

All plug-ins implement the same simple Value Invert function for easy
comparison and cross reference.  They all appear in
    Data Proces -> Plug-Ins -> Test -> Value Invert (LANGUAGE_NAME)
menu in Gwyddion.

All also implement it the same way, if possible: a class/module/unit reading
and writing plug-in proxy dump files is defined separately from the plug-in.
This makes the plug-ins really simple and allows to reuse the module as is.

For languages where it seemed useful, a plug-in helper function/method
encapsulating the command line argument handling is defined too.

C++
    Note it doesn't resemble Gwyddion C implementation much, it's full of STL
    stuff, a really different implementation.

    It is only distributed but never built.  It seems a proper configure check
    for *optional* C++ is next to impossible.

    Files:
    dump.cc, dump.hh: Dump format implementation (a really simple class).
    plugin-helper.hh: Plug-in helper simplifying command line processing.
    invert_cpp.cc: The plug-in itself.

Pascal
    Uses Delphi dialect (namely for dynamic arrays), should be compilable
    with FreePascal >= 1.9 and Delphi.

    Files:
    GwyddionDump.pas: Dump format and plug-in helper.
    invert_pascal.pas: The plug-in itself.

Perl
    Files:
    invert_perl.pl: The plug-in itself.

    The dump format in implemented in Gwyddion::dump module in
    ../../perl/Gwyddion/dump.pm, installed with Gwyddion by default.

Python
    Files:
    invert_python.py: The plug-in itself.

    The dump format in implemented in Gwyddion.dump module in
    ../../python/Gwyddion/dump.py, installed with Gwyddion by default.


Beside that, a one extraodrinary plug-in is present:

yellow.sh
    A shell plug-in demostrating a property of plug-in proxy: it remembers
    EVERYTHING and only updates it with data obtained from the plug-in.
    So this plug-in only writes a single line of metadata and does not
    deal with the data itself at all.

