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/** @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 SVN. While we do NOT recomend this for

normal users, it makes sense for plugin developers to use SVN 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 SVN.

Gaim puts a lot of strain on SourceForge'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,

GAIM_PRIORITY_DEFAULT,

"core-hello_world",

"Hello World!",

VERSION,

"Hello World Plugin",

NULL,

"http://www.helloworld.tld",

plugin_load,

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?)

"http://www.helloworld.tld", /* 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.

pidgin/pidgin