C Plugin Tutorial
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 are also written in C.
Getting Started
To develop a plugin you need to have the libpurple and (for UI plugins) the Pidgin/Finch source code or development headers. It is generally a good idea to compile against the same version of Pidgin that you are running. You may also want to develop against the code in our Mercurial repository if you need to use a new feature. Please do not abuse our Mercurial repository, however.
An Example
I know every tutorial has a hello world, so why should libpurple be any different?
#include <purple.h>
static GPluginPluginInfo *
hello_world_query(GError **error)
{
const gchar * const authors[] = {
"Author Name <e@mail>",
NULL
};
/* For specific notes on the meanings of each of these members, consult the
C Plugin Howto on the website. */
return purple_plugin_info_new (
"name", "Hello World!",
"version", VERSION,
"category", "Example",
"summary", "Hello World Plugin",
"description", "Hello World Plugin",
"authors", authors,
"website", "http://helloworld.tld",
"abi-version", PURPLE_ABI_VERSION,
NULL
);
}
static gboolean
hello_world_load(GPluginPlugin *plugin, GError **error)
{
purple_notify_message(plugin, PURPLE_NOTIFY_MSG_INFO, "Hello World!",
"This is the Hello World! plugin :)",
NULL, NULL, NULL, NULL);
return TRUE;
}
static gboolean
hello_world_unload(GPluginPlugin *plugin, gboolean shutdown, GError **error)
{
return TRUE;
}
GPLUGIN_NATIVE_PLUGIN_DECLARE(hello_world)
Okay, so what does all this mean? We start off by including purple.h. This file includes all the libpurple header files.
hello_world_query
, hello_world_load
and hello_world_unload
are functions
that must be implemented in every plugin. These functions are named according
to the value passed to GPLUGIN_NATIVE_PLUGIN_DECLARE
which is described below.
hello_world_query
is called when the plugin is queried by the plugin system,
and returns various information about the plugin in form of a newly created
instance of GPluginPluginInfo
or a subclass. For a list of all available
properties, see purple_plugin_info_new()
.
If anything should go wrong during the query you can return an error by using
g_set_error()
on the error
argument.
hello_world_load
is called when the plugin is loaded. That is the user has
enabled the plugin or libpurple is loading a plugin that was previously loaded.
You can initialize any variables, register dynamic types, and so on in this
function. Plugins may also want to add their preferences to the pref
tree—more about that later. In this plugin we’ll just use it to display a
message. Just like hello_world_query
if there are any errors that arise, you
can call g_set_error()
on the error
argument and return FALSE
.
hello_world_unload
is called when the plugin is unloaded. That is, when the
user has manually unloaded the plugin or the program is shutting down. We can
use it to wrap up everything, and free our variables. If the program is shutting
down, the shutdown
argument will be TRUE
. Again, if there are any errors, you
can call g_set_error()
on the error
argument and return FALSE
.
Finally we have GPLUGIN_NATIVE_PLUGIN_DECLARE()
. It is a helper macro that
makes creating plugins easier. It has a single argument which is the prefix
used for the _query
, _load
, and _unload
functions.