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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html">
</head>
<body bgcolor="#FFFFFF" lang="en">
<h1>Cronos II Plugins Development</h1>
<h2>For version 0.2.0, 17 Feb 2001</h2>
<i>Pablo Fernndez Navarro</i> <a
href="mailto:cronosII@users.sourceforge.net"><cronosII@users.sourceforge.net></a>
<p><a
href="http://cronosII.sourceforge.net">http://cronosII.sourceforge.net</a></p>
<p></p>
<hr color="#000000" noshade="noshade">
<h1>Table of Contents</h1>
<ol>
<li><a href="#Introduction">Introduction</a>
<ol>
<li><a href="#What is a plugin">What is a plugin?</a></li>
</ol>
</li>
<li><a href="#Signals">Signals</a>
<ol>
<li><a href="#Theory of Signals and Callbacks">Theory of Signals and
Callbacks</a></li>
<li><a href="#Connecting">Connecting</a></li>
<li><a href="#Disconnecting">Disconnecting</a></li>
<li><a href="#Using the interface">Using the interface</a></li>
<li><a href="#Signal List">Signal List</a></li>
</ol>
</li>
<li><a href="#Required Functions">Required Functions</a>
<ol>
<li><a href="#module_init">module_init</a></li>
<li><a href="#module_cleanup">module_cleanup</a></li>
</ol>
</li>
<li><a href="#Optional Functions">Optional Functions</a>
<ol>
<li><a href="#Configure">Configure</a></li>
</ol>
</li>
<li><a href="#Tips for writing Cronos II Plugins">Tips for writing Cronos II
Plugins</a></li>
<li><a href="#Final words">Final words on...</a>
<ol>
<li><a href="#Final words on API">API</a></li>
<li><a href="#Final words on distributing">Distributing</a></li>
</ol>
</li>
</ol>
<p></p>
<hr noshade="noshade" color="#000000">
<h1><a name="Introduction">Introduction</a></h1>
<blockquote>
While you read this manual and code your plugin, I recommend you open the
<em>sample plugin</em> which comes in the source distribution of Cronos II.
( In the directory /plugins/sample/sample.c) Then you can see how plugins
are structured. When you code your own plugin you should code with that same
structure to avoid confusing errors.<br>
</blockquote>
<h3><a name="What is a plugin">What is a plugin?</a></h3>
<blockquote>
A plugin is a compiled module which can be loaded dynamically by a program,
in this case, Cronos II.<br>
The term <i>Dynamic Loading</i> means that the module can be loaded on the
fly, while the program is running.
<p>Plugins are designed to fulfill an specific task, like decoding incoming
messages and encoding outgoing messages (GnuPG plugin), randomly selecting a
signature, or any other thing you can think of, you can even make changes to
the UI (User Interface) of Cronos II.</p>
<p>Plugins development might sound like a really difficult thing if this is
your first attempt to do such a thing. Actually, the development of plugins
for Cronos II is a really simple task thanks to the API Cronos II brings to
you.</p>
</blockquote>
<hr noshade="noshade">
<h1><a name="Signals">Signals</a></h1>
<h3><a name="Theory of Signals and Callbacks">Theory of Signals and
Callbacks</a></h3>
<blockquote>
Cronos II Plugins Development is done through <i>signals</i>. (Note that
these signals are not the same as the Unix system signals, and are not
implemented using them, although the terminology is almost identical.) When
an event occurs, such as the downloading of a new message, the appropriate
signal will be <i>emitted</i> by Cronos II.
<p>When a signal is emitted, all functions <i>connected</i> to that signal
are called passing specific signal parameters.<br>
Plugins which don't connect to any signal are useless plugins, so you should
<b>always</b> connect your plugin to a signal.</p>
</blockquote>
<h3><a name="Connecting">Connecting</a></h3>
<blockquote>
<p>The way to connect to a signal is by calling a function in the
initialization function of the module, which will always be
<i>module_init</i>.</p>
<table border="0" cellpadding="5">
<tr>
<td bgcolor="#DDDDDD" align="right"><pre type=MACHINE>c2_dynamic_module_signal_connect (const char *module_name, C2DynamicModuleSignal signal,C2DynamicModuleSignalFunc func);</pre>
</td>
</tr>
</table>
<p>Where the first argument is the name of the module, the second argument
is the type of signal (View <a href="#Signal List">Signal List</a>). The
third argument is a function of type C2DynamicModuleSignalFunc which will be
called when this signal is emitted.</p>
The functions of type C2DynamicModuleSignalFunc look like this:
<table border="0" cellpadding="5">
<tbody>
<tr>
<td bgcolor="#DDDDDD" align="right"><pre type=MACHINE>void function (void *arg1, void *arg2, void *arg3, void *arg4, void *arg4, void *arg5);</pre>
</td>
</tr>
</tbody>
</table>
<p>Note that they may also ignore any or all of the arg* variables, ie:</p>
<table border="0" cellpadding="5">
<tbody>
<tr>
<td bgcolor="#DDDDDD" align="right"><pre type=MACHINE>void function (void *arg1, void *arg2);</pre>
</td>
</tr>
</tbody>
</table>
<p>When you connect to a signal, some data, of an specific type will be
passed to the function you connected (called a <i>function callback</i>),
thus you might want to specify the type of variable in the function
definition.</p>
<p>Ie. You might want to use a function callback of type:</p>
<table border="0" cellpadding="5">
<tbody>
<tr>
<td bgcolor="#DDDDDD" align="right"><pre type=MACHINE>void function (const char *message, const char *username);</pre>
</td>
</tr>
</tbody>
</table>
<p>for a signal that passes such arguments instead of:</p>
<table border="0" cellpadding="5">
<tbody>
<tr>
<td bgcolor="#DDDDDD" align="right"><pre type=MACHINE>void function (void *arg1, void *arg2);</pre>
</td>
</tr>
</tbody>
</table>
<p>This works just like GTK+ or GNOME.</p>
<p>Note that when you pass the third argument to the function
<i>c2_dynamic_module_signal_connect</i> you should always use the macro
<i>C2_DYNAMIC_MODULE_SIGNAL_FUNC (function)</i> to ensure the cast is
correctly done.</p>
</blockquote>
<h3><a name="Disconnecting">Disconnecting</a></h3>
<blockquote>
Connected signals can be disconnected, once you don't want to use them any
more or when the module is required to clean up <br>
(View <a href="#module_cleanup">module_cleanup</a>).The way to do this is
calling the function:
<table border="0" cellpadding="5">
<tbody>
<tr>
<td bgcolor="#DDDDDD" align="right"><pre type=MACHINE>void c2_dynamic_module_signal_disconnect (const char *module_name, C2DynamicModuleSignal signal);</pre>
</td>
</tr>
</tbody>
</table>
<p>Where the first argument is the name of the module and the second is the
type of signal.</p>
</blockquote>
<h3><a name="Using the interface">Using the interface</a></h3>
<blockquote>
Callback functions are called out of the main thread, outside of where the
gtk_main function is being executed. Thus if you want to do draw something
in the user interface (ie. a window) you must call two
functions.<i>gdk_threads_enter ()</i> is called <b>before</b> doing anything
that would update the interface, like calling gtk_widget_show or something
like that. <i>gdk_threads_leave ()</i> is called <b>after</b> updating the
interface.If you want to do a callback that draws a simple window you should
code something like this:
<table border="0" cellpadding="5">
<tbody>
<tr>
<td bgcolor="#DDDDDD"><pre type=MACHINE>void graphic_function (void) {
GtkWidget *window;
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_window_set_title (GTK_WINDOW (window), "Sample window");
gdk_threads_enter ();
gtk_widget_show (window);
gdk_threads_leave ();
}</pre>
</td>
</tr>
</tbody>
</table>
</blockquote>
<h3><a name="Signal List">Signal List</a></h3>
<blockquote>
<table border="0" cellpadding="5" bgcolor="#DDDDDD">
<tbody>
<tr>
<td><pre type=MACHINE>C2_DYNAMIC_MODULE_CHECK_NEW_SESSION</pre>
</td>
<td><pre type=MACHINE>(int length)</pre>
</td>
</tr>
<tr>
<td colspan="2"><pre type=MACHINE>@length: Number of accounts to be checked.</pre>
<pre type=MACHINE>Definition: This signal is emitted every time a checking session is about to start or some
account is added to the checking queue while active.<br>
</pre>
</td>
</tr>
<tr>
<td><pre type=MACHINE>C2_DYNAMIC_MODULE_CHECK_NEW_ACCOUNT</pre>
</td>
<td><pre type=MACHINE>(Account *account)</pre>
</td>
</tr>
<tr>
<td colspan="2"><pre type=MACHINE>@account: Account to be checked.</pre>
<pre type=MACHINE>Definition: This signal is emitted every time checking of an account is about to start.<br>
</pre>
</td>
</tr>
<tr>
<td><pre type=MACHINE>C2_DYNAMIC_MODULE_MESSAGE_DOWNLOAD_POP</pre>
</td>
<td><pre type=MACHINE>(Message *message)</pre>
</td>
</tr>
<tr>
<td colspan="2"><pre type=MACHINE>@message: Message downloaded.</pre>
<pre type=MACHINE>Definition: This signal is emitted every time a message is downloaded from a POP account.<br>
</pre>
</td>
</tr>
<tr>
<td><pre type=MACHINE>C2_DYNAMIC_MODULE_MESSAGE_DOWNLOAD_SPOOL</pre>
</td>
<td><pre type=MACHINE>(Message *message)</pre>
</td>
</tr>
<tr>
<td colspan="2"><pre type=MACHINE>@message: Message downloaded.</pre>
<pre type=MACHINE>Definition: This signal is emitted every time a message is downloaded from a SPOOL account.<br>
</pre>
</td>
</tr>
<tr>
<td><pre type=MACHINE>C2_DYNAMIC_MODULE_COMPOSER_SEND</pre>
</td>
<td><pre type=MACHINE>(Message *message)</pre>
</td>
</tr>
<tr>
<td colspan="2"><pre type=MACHINE>@message: Message to be sent.</pre>
<pre type=MACHINE>Definition: This signal is emitted every time a message is about to be sent.<br>
</pre>
</td>
</tr>
<tr>
<td><pre type=MACHINE>C2_DYNAMIC_MODULE_COMPOSER_INSERT_SIGNATURE</pre>
</td>
<td><pre type=MACHINE>(char **signature)</pre>
</td>
</tr>
<tr>
<td colspan="2"><pre type=MACHINE>@*signature: Signature to be added.</pre>
<pre type=MACHINE>Definition: This signal is emitted every time a signature is going to be appended to a
message in the composer window.<br>
</pre>
</td>
</tr>
<tr>
<td><pre type=MACHINE>C2_DYNAMIC_MODULE_WINDOW_FOCUS</pre>
</td>
<td><pre type=MACHINE>(const char *type)</pre>
</td>
</tr>
<tr>
<td colspan="2"><pre type=MACHINE>@type: Name of window. (ie. main, composer, checker)</pre>
<pre type=MACHINE>Definition: This signal is emitted every time a window gains focus.<br>
</pre>
</td>
</tr>
<tr>
<td><pre type=MACHINE>C2_DYNAMIC_MODULE_MESSAGE_OPEN</pre>
</td>
<td><pre type=MACHINE>(Message *message, const char *type)</pre>
</td>
</tr>
<tr>
<td colspan="2"><pre type=MACHINE>@message: Message to be opened.
@type: Type of opening. (preview, composer, message)</pre>
<pre type=MACHINE>Definition: This signal is emitted every time a message is opened in someway to take
some action on it.
<b>Note:</b> This signal is emitted from the gdk thread, so be careful how you use it!</pre>
</td>
</tr>
</tbody>
</table>
</blockquote>
<hr noshade="noshade">
<h1><a name="Required Functions">Required Functions</a></h1>
<h3><a name="module_init">module_init</a></h3>
<blockquote>
The function module_init is the first function called of any module. The
structure of this function is as follows:
<table border="0" cellpadding="5">
<tbody>
<tr>
<td bgcolor="#DDDDDD"><pre type=MACHINE>char *module_init (int major_version, int minor_version, int micro_version, C2DynamicModule *module);</pre>
</td>
</tr>
</tbody>
</table>
<p>This function should return NULL on success or an string describing why
the module hasn't been loaded.<br>
The first argument of this function is major version number of the Cronos II
running version, the second argument is the minor version and the third
argument is the micro version.<br>
The major version is the first number of the version (<b>0</b>.2.0).<br>
The minor version is the second number of the version (0.<b>2</b>.0).<br>
The micro version is the third number of the version (0.2.<b>0</b>).<br>
The fourth argument is a pointer to an allocated C2DynamicModule object that
this function should fill with valid information.</p>
This function should do the following things in this order (plus anything
else you require):
<ul>
<li>Check if the Cronos II version is better or equal to the version you
requite. This is done because your module might need some special API
provided by some version. For example, plugins are supported since
version 0.2.0, therefore you should always require, at least, this
version.</li>
<li>Check if this plugin is already loaded using the function <a
href="#Functions List-c2_dynamic_module_find">c2_dynamic_module_find</a>.</li>
<li>Set up module (some module information):
<ul>
<li><b>name:</b> Name of the plugin (eg. "GnuPG"),</li>
<li><b>version:</b> Version of the plugin (eg. "0.1"),</li>
<li><b>author:</b> Name and email of the author of the plugin (e.g.
"Pablo Fernndez Navarro
<cronosII@users.sourcefroge.net>"),</li>
<li><b>url:</b> URL where this plugin can be downloaded (e.g.
"http://cronosII.sourceforge.net"),</li>
<li><b>description:</b> A description of what this plugin does (ie.
"Decodes incoming encoded messages and encodes outgoing
messages"),</li>
<li><b>configure:</b> Pointer to a function that will be called when
the user wants to configure the plugin (View <a
href="#Configure">Configure</a>). If you don't want your users to
configure the plugin you should set it to NULL,</li>
<li><b>configfile:</b> This should be set to the return of the
function <a
href="#Functions List-c2_dynamic_module_get_config_file">c2_dynamic_module_get_config_file</a>.</li>
</ul>
</li>
<li>Load the configuration (if your plugin uses configuration).</li>
<li>Connect the signals (View <a href="#Connecting">Connecting</a>)</li>
</ul>
</blockquote>
<h3><a name="module_cleanup">module_cleanup</a></h3>
<blockquote>
The function module_cleanup is the function called when the user wants to
unload the plugin or when Cronos II is exiting.
<p>The typography of this function is as follows:</p>
<table border="0" cellpadding="5">
<tbody>
<tr>
<td bgcolor="#DDDDDD"><pre type=MACHINE>void module_cleanup (C2DynamicModule *module);</pre>
</td>
</tr>
</tbody>
</table>
<p>The first and unique argument is a pointer to the C2DynamicModule
containing the plugin information.</p>
This function should do the following things and anything else you require:
<ul>
<li>Disconnect <b>all</b> connected signals.</li>
</ul>
</blockquote>
<hr noshade="noshade">
<h1><a name="Optional Functions">Optional Functions</a></h1>
<h3><a name="Configure">Configure</a></h3>
<blockquote>
You may want the user to be able to configure the plugin.
<p>eg. The sample plugin does a simple task: when a mail <i>from a
specific address</i> arrives the user is notified with a simple
<b>gnome_ok_dialog</b>.<br>
The part that we will talk about in this section is the <i>from a specific
address</i>.<br>
How can you know which address should be waiting for notifying the user?
Simple, with a configuration window.</p>
<p>You might noticed that the Preferences dialog, in the section of
"Plug-Ins" is the one that handles the stuff related to the plugins. There's
a button named "Configure".<br>
When that button is pressed the function pointed by module->configure is
called unless you set module->configure to NULL.</p>
</blockquote>
<hr noshade="noshade">
<h1><a name="Tips for writing Cronos II Plugins">Tips for writing Cronos II
Plugins</a></h1>
<blockquote>
Cronos II gives you a tool for correctly installing the plugin, you should
really use it.
<p>This tool is called <i>cronosII-config</i>, it gets installed when you
install Cronos II. By using it you will know where to install the plugin
(`cronosII-config --datadir`/plugins) and what version is currently
installed.</p>
<p>You should always keep in mind that Cronos II is designed for GNOME, thus
you should always try to design interfaces with the look & feel of
GNOME, using gnome_stock_button and similar functions ( the libgnomeui
library).</p>
<p>Cronos II hasn't many signals (yet). If you need to work with a signal
that is currently not emitted (like a signal when a message is deleted), you
should just mail me asking for it at <a
href="mailto:cronosII@users.sourceforge.net">cronosII@users.sourceforge.net</a>.
I will add it for you as soon as I can do it.</p>
<p>(Please, include in your request how your plugin will use it.)</p>
</blockquote>
<hr noshade="noshade">
<h1><a name="Final words">Final words on...</a></h1>
<h3><a name="Final words on API">API</a></h3>
<blockquote>
Cronos II has an extended API which is getting larger and larger with each
new version. Having a list of the API is a hard job which would delay the
release of versions too much.
<p>At the time of programming your plugins you're probably going to need to
use this API, unless your plugin does a really simple task, such as showing
"Hello world" each time your module is loaded and "Ronnie was playing in the
field" each time the module is unloaded.<br>
The best way for you to understand the functions in Cronos II is to read
the source files. Most functions are documented in the .c files. Anyway,
functions in Cronos II are very intuitive and self describing.<br>
If you have any doubt about what a function, or a family of functions does,
or how you should work with them you could check some functions that use
them (you can locate them using the GNU <i>grep</i> tool) or you can mail
me at <a href="mailto:cronosII@users.sourceforge.net">
cronosII@users.sourceforge.net</a>.</p>
</blockquote>
<h3><a name="Final words on distributing">Distributing</a></h3>
<blockquote>
Once you finished writing the first version of your plugin, please, send the
URL for it (if you made a home page for it) or send me the tarball by mail
to <a
href="mailto:cronosII@users.sourceforge.net">cronosII@users.sourceforge.net</a>.<br>
</blockquote>
</body>
</html>
|
