WIP: Some documentation of plugins

docs/plugins/developing.rst

@@ -9,10 +9,121 @@ Developing Plugins
    A section on how to develop plugins yourself, including a tutorial creating an exemplary plugin as well as
    a documentation of the plugin API, will be added in the near future.
 
-.. _sec-plugins-developing-types:
+.. note::
 
-Available plugin types
-======================
+   This section is still a heavy WIP, so take it with a bit of caution ;)
+
+OctoPrint Plugin Structure
+==========================
+
+OctoPrint plugins are simple `Python modules or packages <https://docs.python.org/2/tutorial/modules.html>`_ providing
+a couple of properties describing the module:
+
+``__plugin_name__``
+  Name of your plugin
+``__plugin_version__``
+  Version of your plugin
+``__plugin_description__``
+  Description of your plugin
+``__plugin_implementations__``
+  Instances of one or more of the various :ref:`plugin mixins <sec-plugins-developing-mixins>`
+``__plugin_hooks__``
+  Handlers for one or more of the various :ref:`plugin hooks <sec-plugins-developing-hooks>`
+``__plugin_check__``
+  Method called upon discovery of the plugin by the plugin subsystem, should return ``True`` if the
+  plugin can be instantiated later on, ``False`` if there are reasons why not, e.g. if dependencies
+  are missing.
+``__plugin_init__``
+  Method called upon initializing of the plugin by the plugin subsystem, can be used to instantiate
+  plugin implementations, connecting them to hooks etc.
+
+A very simple example plugin which only hooks into OctoPrint's startup sequence and prints out "Hello World" to stdout would
+be the following snippet:
+
+.. code-block:: python
+
+   # coding=utf-8
+   from __future__ import absolute_import
+
+   import octoprint.plugin
+
+   __plugin_name__ = "Example Plugin"
+   __plugin_version__ = "0.1"
+   __plugin_description__ = "Prints \"Hello World!\" to stdout upon OctoPrint's startup"
+
+   def __plugin_init__():
+       global __plugin_implementations__
+       __plugin_implementations__ = [HelloWorldPlugin()]
+
+   class HelloWorldPlugin(octoprint.plugin.StartupPlugin):
+       def on_startup(self, host, port):
+           print("Hello World!")
+
+Distributing your plugin
+========================
+
+You can distribute a plugin with OctoPrint via two ways:
+
+  - You can have your users copy it to OctoPrint's plugin folder (normally located at ``~/.octoprint/plugins`` under Linux,
+    ``%APPDATA%\OctoPrint\plugins`` on Windows and ... on Mac). In this case your plugin will be distributed directly
+    as a Python module (a single ``.py`` file containing all of your plugin's code directly and named
+    like your plugin) or a package (a folder named like your plugin + ``__init.py__`` contained within).
+  - You can have your users install it via ``pip`` and register it for the `entry point <https://pythonhosted.org/setuptools/setuptools.html#dynamic-discovery-of-services-and-plugins>`_ ``octoprint.plugin`` via
+    your plugin's ``setup.py``, this way it will be found automatically by OctoPrint upon initialization of the
+    plugin subsystem [#f1]_.
+
+    In this case you'll have a directory structure like the following:
+
+    .. code-block:: none
+
+       `-+ helloworld
+       | `-+ static
+       | | `-+ css
+       | |   `-- helloworld.css
+       | | `-+ js
+       | |   `-- helloworld.js
+       | | `-+ less
+       | |   `-- helloworld.less
+       | `-+ templates
+       | | `-- helloworld_settings_dialog.js
+       | `-- __init__.py
+       `-- setup.py
+
+    The plugin itself will be distributed as a Python package, which your ``setup.py`` will refer to via the entry point
+    like this:
+
+    .. code-block:: python
+
+       import setuptools
+
+       def params():
+           name = "OctoPrint-HelloWorld"
+           version = "0.1"
+           packages = ["helloworld"]
+           install_requires = open("requirements.txt").read().split("\n")
+
+           entry_points = {
+               "octoprint.plugin" = ["helloworld = octoprint_helloworld"]
+           }
+
+           return locals()
+
+       setuptools.setup(**params())
+
+    This variant is highly recommended for pretty much any plugin besides the most basic ones since it also allows
+    requirements management and pretty much any thing else that Python's setuptools provide to the developer.
+
+.. rubric:: Footnotes
+
+.. [#f1] The automatic registration will only work within the same Python installation (this also includes virtual
+         environments), so make sure to instruct your users to use the exact same Python installation for installing
+         the plugin that they also used for installing & running OctoPrint.
+
+
+.. _sec-plugins-developing-mixins:
+
+Available plugin mixins
+=======================
 
 .. automodule:: octoprint.plugin.types
    :members: