Plug-ins

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Revision as of 23:06, 29 September 2009 by Xalendare (Talk | contribs) (Preparing a Linux BZFS)

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BZFS can be built to support the loading of external libraries as plug-ins. These plug-ins can alter or replace the logic applied by the server, as well as automate many common tasks.

Plug-ins are a simpler way to apply modifications to the game, as they do not require the server owner to modify or recompile his/her BZFS application. By using the BZFS API plug-ins are also able to be mixed and matched in an easy way.

Overview

Plug-ins are compile dynamic link libraries, that are built for the same OS/RuntimeEnvironment as the BZFS server that hosts them. On Microsoft Windows they are built as DLL files. On Linux and other Unix-like systems they are built as .so files.

Use

Plug-ins are loaded at startup by the -loadplugin option, or at run time with the /loadplugin command. If the full path to the plug-in is not specified, then BZFS will search a number of known sub directories for the plug-in as it attempts to load it. Using a valid path to the plug-in on load is highly recommended. While playing, all plug-ins loaded onto the server are visible with the /listplugins command.

Parameters

Some plug-ins take parameters that are passed to the plug-in on load. This is often a numeric value, or a path to a file. To pass a parameter to a plug-in, simply add a ',' after the plug-in name or path, and then add the parameter. Parameters can not have spaces, due to the way BZFS parses command line options and / commands.

On load, plug-ins install a number of callbacks and event handlers with the hosting BZFS that are called when specific events happen. This allows the plug-in to perform additional actions on these events, or if need be, alter the results of the default logic of the server.

Search Paths

BZFS searches for plug-ins in two standard locations: the config directory and the global plug-ins directory. The config directory is where the BZFlag config.cfg file is located, and the global plug-ins directory is $(prefix)/lib/bzflag/.

BZFS API

All plug-ins are linked to the BZFS API. This programing layer provides the interface to the BZFS application. All events and functions that a plug-in can call are in the BZFS API.

Standard plug-ins

The BZFlag Source distribution contains a number of plug-ins that are maintained by the project developers. These plug-ins are located in the /plugins directory.

As of August 2009, SVN TRUNK( version 2.99) contains the following plug-ins:

Third Party Plug-ins

A number of non-developers have created plug-ins for BZFS, and usually release them on the BZFlag Forums.

Here are the steps to compile a hypothetical third party plug-in named "Example":

  1. In the plugins directory of the BZFlag source tree run the command ./newplugin.sh Example
  2. Remove all of the files from the newly created plugins/Example directory (they were created by newplugin.sh)
  3. Copy all of the distributed Example files into the plugins/Example directory
  4. In the top-level BZFlag source directory, edit configure.ac, and add plugins/Example/Makefile to the list of AC_CONFIG_FILES
  5. In the top-level BZFlag source directory run autogen.sh, configure, and make as usual

When that finishes successfully the plug-in should be ready to use as described above.

Preparing a Linux BZFS

For becoming BZFS able to run plugins you need to recompile it with the --enable-shared option on the configure script.

$ ./configure --enable-shared --disable-client;
      make;
      make install;

Plug-in Development

Plywood hammer100x101.gif There is still documentation to be done here!! If you feel up to the task, please have a go at it. Specifically what needs to be added is:
Describe the basics of plug-in development.