This is an example of a Gyoto plug-in.

To make your own,

1- choose a cool name;
2- copy this directory (plugins/null/) somewhere;
3- enter into this directory;
4- edit configure.ac, lib/Makefile.am and lib/InitPlug.C: replace any
   occurrence of "null" with your cool name;
5- add new metrics and astrobjs as needed in lib/ and include/, the
   gyoto source code is also full of examples;
6- edit lib/InitPlug.C to register your new classes (rename it to
   CoolPlug.C if you wish);
7- add the name of the required C++ source files to the
   libgyoto_null_la_SOURCES variable in lib/Makefile.am (this variable
   should have been renamed to libgyoto_<cool-name>_la_SOURCES by
   now);
8- run autoreconf (whenever you edit any configure.ac or Makefile.am
   file), then ./configure, make, make install...
9- if installing to default directories (/usr/local/lib), you may need
   to run 'sudo ldconfig'
10- You can now start using your plug-in by loading it with any of the
   available methods:
     - In XML: <Astrobj plugin="null" kind="null"/>
     - On the command line: gyoto -pstdplug,null ...
     - In Python:
          gyoto.requirePlugin('null')
     - In all cases: export GYOTO_PLUGINS="stdplug,null".

For further details, refer to the Gyoto user manual, section entitled
`Writing a C++ plug-in' (as of writing, Sect. 8.2).
