Add more docs and signals.

docs/plugins.rst

@@ -2,28 +2,85 @@
  Plugins
 =========
 
-Signals
--------
+How to use plugins
+------------------
 
-.. data:: sigal.signals.img_resized
-   :noindex:
+Plugins must be specified with the ``plugins`` setting:
 
-   Called after the image is resized.
+.. code-block:: python
+
+   from sigal.plugins import copyright
+   plugins = ['sigal.plugins.adjust', copyright]
+
+You can either specify the name of the module which contains the plugin, or
+import the plugin before adding it to the list. The ``plugin_paths`` setting
+can be used to specify paths to search for plugins (if they are not in the
+python path).
 
 Write a new plugin
 ------------------
 
-See an example with the copyright plugin:
+Plugins are based on signals with the blinker_ library. A plugin must
+subscribe to a signal (the list is given below). New signals can be added if
+need. See an example with the copyright plugin:
+
+.. _blinker: http://pythonhosted.org/blinker/
 
 .. literalinclude:: ../sigal/plugins/copyright.py
    :language: python
 
+Signals
+-------
+
+.. function:: sigal.signals.album_initialized(album)
+   :noindex:
+
+   Called after the :class:`~sigal.gallery.Album` is initialized.
+
+   :param album: the :class:`~sigal.gallery.Album` object.
+
+.. data:: sigal.signals.gallery_initialized(gallery)
+   :noindex:
+
+   Called after the gallery is initialized.
+
+   :param gallery: the :class:`Gallery` object.
+
+.. data:: sigal.signals.media_initialized(media)
+   :noindex:
+
+   Called after the :class:`~sigal.gallery.Media`
+   (:class:`~sigal.gallery.Image` or :class:`~sigal.gallery.Video`) is
+   initialized.
+
+   :param media: the media object.
+
+.. data:: sigal.signals.gallery_build(gallery)
+   :noindex:
+
+   Called after the gallery is build (after media are resized and html files
+   are written).
+
+   :param gallery: the :class:`Gallery` object.
+
+.. data:: sigal.signals.img_resized(img, settings=settings)
+   :noindex:
+
+   Called after the image is resized. This signal work differently, the
+   modified image object must be returned by the registered funtion.
+
+   :param img: the PIL image object.
+   :param settings: the settings dict.
+
+List of plugins
+---------------
+
 Adjust plugin
--------------
+=============
 
 .. automodule:: sigal.plugins.adjust
 
 Copyright plugin
-----------------
+================
 
 .. automodule:: sigal.plugins.copyright