doc/C-HOWTO.dox

/** @page c-howto C Plugin HOWTO

 @section Introduction
  C plugins are native plugins.  They have complete access to all of the api,
  and can do basically whatever they want.  All of the protocol plugins, as
  well as the perl and tcl loader plugins are written in C.

 @section getting_started Getting Started
  To develop a plugin you need to have the Gaim source code.  It is generally a
  good idea to compile against the same version of Gaim that you are running.
  You may also want to develop against CVS.  While we do NOT recomend this for
  normal users, it makes sense for plugin developers to use CVS to ensure their
  plugins works with the most recent changes in Gaim.  A lot tends to
  change between versions and it's much easier to fix your plugin as things
  change rather than waiting until the release.  But please do not abuse CVS.
  Gaim puts a lot of strain on Source Forge's servers, and we do not need to
  add anymore to it.

  If you choose not to head my warnings and develop against a version of Gaim
  that is different from what you're running, then your Gaim source must at
  the very least be configured.  Note that just running configure will
  generally set the prefix to /usr/local.  This shouldn't be a problem, except
  that most packages compile and install Gaim with /usr as the prefix.

  All plugins must have @c GAIM_PLUGINS defined.  You can choose to include
  @c internal.h to do this, but if you choose to do it this way it must be
  included before any other Gaim files.  Likewise, if you choose to manually
  define @c GAIM_PLUGINS, the definition must be before including any Gaim
  files.  Failure to do so will produce the 'plugin foo could not be loaded for
  an unknown reason'.  This is one of the hardest unknown reasons to track
  down, so let's try to avoid it at all costs ;)

 @section hello_world Hello World!
  I know every tutorial has a hello world, so why should Gaim be any different?

  @code
#define GAIM_PLUGINS

#include <glib.h>

#include "notify.h"
#include "plugin.h"
#include "version.h"

static gboolean
plugin_load(GaimPlugin *plugin) {
	gaim_notify_message(plugin, GAIM_NOTIFY_MSG_INFO, "Hello World!",
						"This is the Hello World! plugin :)", NULL, NULL, NULL);

	return TRUE;
}

static GaimPluginInfo info = {
	GAIM_PLUGIN_MAGIC,
	GAIM_MAJOR_VERSION,
	GAIM_MINOR_VERSION,
	GAIM_PLUGIN_STANDARD,
	NULL,
	0,
	NULL,
	GAIM_PRIORITY_DEFAULT,

	"core-hello_world",
	"Hello World!",
	VERSION,

	"Hello World Plugin",
	"Hello World Plugin",
	NULL,
	GAIM_WEBSITE,

	plugin_load,
	NULL,
	NULL,

	NULL,
	NULL,
	NULL,
	NULL
};

static void
init_plugin(GaimPlugin *plugin) {
}

GAIM_INIT_PLUGIN(hello_world, init_plugin, info);

  @endcode

  Okay, so what does all this mean?  We start off by defining @c GAIM_PLUGINS
  like described before.  Next we include glib.h, mainly for gboolean and the
  glib wrappers of the standard c types.  We could just use stdio and use
  an int for the gboolean but since Gaim uses glib internally, we might as
  well do the same.

  Next, we include plugin.h which has all the plugin specific stuff that we
  need.  For example @c GaimPlugin, @c GaimPluginInfo, @c GAIM_PLUGIN_MAGIC,
  and @c GAIM_INIT_PLUGIN().

  Our last include is version.h which defines @c GAIM_MAJOR_VERSION, and
  @c GAIM_MINOR_VERSION.  There is not much you need to know about these,
  except that they are required and will stop your plugin from crashing Gaim
  when something has changed that you plugin does not know about yet.

  plugin_load is not required.  It is called when the plugin is loaded so that
  you can initialize any variables and so on.  But in this plugin we'll just
  use it to display a message.

  Next we have the @c GaimPluginInfo structure.  Every plugin MUST have one of
  these.  Below is a code snipet of the same struct used in @c hello_world with
  comments describing what each is.

  @code
static GaimPluginInfo info = {
	GAIM_PLUGIN_MAGIC,          /* Plugin magic, this should always be
                                   GAIM_PLUGIN_MAGIC.  This value gets
                                   incremented inside of Gaim so that plugins
                                   that haven't been updated yet will fail to
                                   load and avoid potential crashes while
                                   loading old plugins.
                                  */
	GAIM_MAJOR_VERSION,          /* This is also defined in Gaim.  It helps
                                    Gaim's plugin system determine what version
                                    of Gaim this plugin was compiled for, and
                                    whether loading it will cause problems.
                                  */
	GAIM_MINOR_VERSION,          /* See previous */
	GAIM_PLUGIN_STANDARD,        /* GaimPluginType, there are 4 different values
                                    for this field.  The first is
                                    GAIM_PLUGIN_UNKNOWN,  which should not be
                                    used.  The second is GAIM_PLUGIN_STANDARD,
                                    this is the value most plugins will use.
                                    Next we have GAIM_PLUGIN_LOADER,  this is
                                    the type you want to load if your plugin
                                    is going to make it possible to load non-
                                    native plugins.  For example, perl and tcl.
                                    Last, we have GAIM_PLUGIN_PROTOCOL.  If
                                    your plugin is going to allow the user to
                                    connect to another network, this is the
                                    type you'd want to use.
                                  */
	NULL,                         /* This field is the ui requirement.  This
                                     value should be a string.  If you're
                                     writing a core plugin, this should be NULL
                                     and the plugin should not contain any ui
                                     specific code.  If you're writing a gtk
                                     plugin, you can use the
                                     GAIM_GTK_PLUGIN_TYPE macro.  All other ui
                                     plugins are dependent on their ui
                                     implementation, and is outside the scope of
                                     this howto.
                                   */
	0,                            /* This field is for plugin flags.  Currently,
                                     the only flag available to plugins is
                                     invisible (GAIM_PLUGIN_FLAG_INVISIBLE).
                                     This plugin is currently used by the ssl
                                     plugin, the tcl loader, and the perl
                                     loaded.  It causes the plugin to NOT
                                     appear in the list of plugins in Gaim's
                                     preferences window.
                                   */
	NULL,                         /* This is a GList of plugin dependencies.  In
                                     other words, a GList of plugin id's that
                                     your plugin depends on.  If your plugin
                                     does not have any dependencies, set this
                                     value to NULL.
                                   */
	GAIM_PRIORITY_DEFAULT,        /* This is the priority Gaim with give your
                                     plugin.  There are three possible values
                                     for this field, GAIM_PRIORITY_DEFAULT,
                                     GAIM_PRIORITY_HIGHEST, and
                                     GAIM_PRIORITY_LOWEST
                                   */

	"core-hello_world",           /* This is your plugin's id.  There is a whole
                                     page dedicated to this in the
                                     'related-pages' section of Gaim's API docs.
                                   */
	"Hello World!",               /* This is your plugin name.  This is what
                                     will be displayed for your plugin in the ui.
                                   */
	1.1,                          /* This is the version of your plugin.  For
                                     the sake of simplicity, I'm using the Gaim
                                     version.
                                   */

	"Hello World Plugin",         /* This is the summary of your plugin.  It
                                     should be a short little blurb.  The ui
                                     determines where, if at all, to display
                                     this.
                                   */
	"Hello World Plugin",         /* This is the description of your plugin. It
                                     can be as long and as descriptive as you
                                     like.  And like the summary, it's up to the
                                     ui where, if at all, to display this.
                                   */
	NULL,                         /* This is where you can put your name and
                                     email address.  (You are the author right?)
                                   */
	GAIM_WEBSITE,                 /* This is the website for the plugin.  This
                                     is helpful if users find bugs in your
                                     plugin so they can help to bring them to
                                     your attention.
                                   */

	plugin_load,                  /* This is a pointer to a function for Gaim to
                                     call when it is loading your plugin.  It
                                     should be in the form of:

                                     gboolean function_name(GaimPlugin *plugin)

                                     Returning TRUE will tell Gaim to continue
                                     loading your plugin, while FALSE will tell
                                     Gaim to stop trying to load it.
                                   */
	NULL,                         /* Same as above except it is called when
                                     Gaim tries to unload your plugin.  It
                                     should be in the form of:

                                     gboolean function_name(GaimPlugin *plugin)

                                     Where returning TRUE will tell Gaim to
                                     continue unloading and false to not continue
                                     unloading your plugin.
                                   */
	NULL,                         /* Similar to the two above members, except
                                     this is called when Gaim tries to destory
                                     the plugin.  This is generally only called
                                     when for some reason or another the plugin
                                     fails to probe correctly.  It should be in
                                     the form of:

                                     void function_name(GaimPlugin *plugin)
                                   */

	NULL,                         /* This is a pointer to a ui specific struct.
                                     For a gtk plugin it will be a pointer to a
                                     GaimGtkPluginUiInfo struct.
                                   */
	NULL,                         /* This is a pointer to either a 
                                     GaimPluginLoaderInfo struct or a
                                     GaimPluginProtocolInfo struct, and is
                                     beyond the scope of this document.
                                   */
	NULL,                         /* This is a pointer to a GaimPluginUiInfo
                                     struct.  It is a core/ui split way for
                                     core plugins to have a ui configuration
                                     frame.  You can find an example of this
                                     code in plugins/pluginpref_example.c
                                   */
	NULL                          /* Finally the last member of the structure,
                                     is a function pointer where you can define
                                     menu entries for 'Tools->Plugin Actions'.
                                     It should be in the form of:

                                     GList *function_name(GaimPlugin *plugin, 
                                                          gpointer context)

                                     It should return a GList of
                                     GaimPluginActions.
                                   */
};
  @endcode

  Finally we have @c init_plugin and @c GAIM_INIT_PLUGIN.  @c init_plugin is a
  function that gets called when Gaim probes the plugin.  Most plugins will
  add their preferences to the pref tree here, more about that later.
  @c GAIM_INIT_PLUGIN is a macro that EVERY plugin MUST have.  @c GAIM_INIT_PLUGIN
  tells Gaim some very basic things about your plugin, like what name to use
  if the plugin is compiled staticly, the @c init_plugin function, and
  the name of the @c GaimPluginInfo structure.  As you may have guess this
  also gets read when Gaim is probing your plugin.  If this is missing you
  will get the infamous "plugin unloadable for unknown reasons", so do not
  forget it.
 */