480 lines
20 KiB
ReStructuredText
480 lines
20 KiB
ReStructuredText
.. raw:: html
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<div id="banner"><a href="https://github.com/jcbrand/converse.js/blob/master/docs/source/theming.rst">Edit me on GitHub</a></div>
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.. _`writing-a-plugin`:
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Writing a plugin
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================
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Introduction
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------------
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Converse.js is exposes a plugin architecture which allows developers to modify
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and extend its functionality.
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Specifically, plugins enable developers to extend and override existing objects,
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functions and `Backbone <http://backbonejs.org/>`_ models and views that make up
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Converse.js, and also give them the ability to write new models and views.
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Various core features of Converse.js, such as
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`Message Archive Management <https://xmpp.org/extensions/xep-0313.html>`_ and
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`Group chats <https://xmpp.org/extensions/xep-0045.html>`_ are implemented
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as plugins, thereby showing their power and flexibility.
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Converse.js uses `pluggable.js <https://github.com/jcbrand/pluggable.js/>`_ as
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its plugin architecture.
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To more deeply understand how this plugin architecture works, please read the
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`pluggable.js documentation <https://jcbrand.github.io/pluggable.js/>`_
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and to understand its inner workins, please refer to the `annotated source code
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<https://jcbrand.github.io/pluggable.js/docs/pluggable.html>`_.
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.. note:: **Trying out a plugin in JSFiddle**
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Because Converse.js consists only of JavaScript, HTML and CSS (with no backend
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code required like PHP, Python or Ruby) it runs fine in JSFiddle.
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Here's a Fiddle with a Converse.js plugin that calls ``alert`` once it gets
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initialized and also when a chat message gets rendered: https://jsfiddle.net/4drfaok0/15/
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.. note:: **Generating a plugin with Yeoman**
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The rest of this document explains how to write a plugin for Converse.js and
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ends with a documented example of a plugin.
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There is a `Yeoman <http://yeoman.io/>`_ code generator, called
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`generator-conversejs <https://github.com/jcbrand/generator-conversejs>`_, which
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you can use to generate plugin scaffolding/boilerplate, which you can use as a
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starting point and basis for writing your plugin.
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Please refer to the `generator-conversejs <https://github.com/jcbrand/generator-conversejs>`_
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README for information on how to use it.
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Registering a plugin
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--------------------
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Plugins need to be registered (and whitelisted) before they can be loaded and
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initialized.
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You register a converse.js plugin by calling ``converse.plugins.add``.
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The plugin itself is a JavaScript object which usually has at least an
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``initialize`` method, which gets called at the end of the
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``converse.initialize`` method which is the top-level method that gets called
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by the website to configure and initialize Converse.js itself.
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Here's an example code snippet:
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.. code-block:: javascript
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converse.plugins.add('myplugin', {
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initialize: function () {
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// This method gets called once converse.initialize has been called
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// and the plugin itself has been loaded.
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// Inside this method, you have access to the closured
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// _converse object as an attribute on "this".
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// E.g. this._converse
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},
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});
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.. note:: It's important that `converse.plugins.add` is called **before**
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`converse.initialize` is called. Otherwise the plugin will never get
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registered and never get called.
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Whitelisting of plugins
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-----------------------
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As of converse.js 3.0.0 and higher, plugins need to be whitelisted before they
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can be used. This is because plugins have access to a powerful API. For
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example, they can read all messages and send messages on the user's behalf.
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To avoid malicious plugins being registered (i.e. by malware infected
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advertising networks) we now require whitelisting.
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To whitelist a plugin simply means to specify :ref:`whitelisted_plugins` when
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you call ``converse.initialize``.
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Security and access to the inner workings
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-----------------------------------------
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The globally available ``converse`` object, which exposes the API methods, such
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as ``initialize`` and ``plugins.add``, is a wrapper that encloses and protects
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a sensitive inner object, named ``_converse`` (not the underscore prefix).
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This inner ``_converse`` object contains all the Backbone models and views,
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as well as various other attributes and functions.
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Within a plugin, you will have access to this internal
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`"closured" <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures>`_
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``_converse`` object, which is normally not exposed in the global variable scope.
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The inner ``_converse`` object is made private in order to safely hide and
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encapsulate sensitive information and methods which should not be exposed
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to any 3rd-party scripts that might be running in the same page.
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Loading a plugin module
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-----------------------
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Converse.js uses the UMD (Universal Modules Definition) as its module syntax.
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This makes modules loadable via `require.js`, `webpack` or other module
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loaders, but also includable as old-school `<script>` tags in your HTML.
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Here's an example of the plugin shown above wrapped inside a UMD module:
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.. code-block:: javascript
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(function (root, factory) {
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if (typeof define === 'function' && define.amd) {
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// AMD. Register as a module called "myplugin"
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define("myplugin", ["converse"], factory);
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} else {
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// Browser globals. If you're not using a module loader such as require.js,
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// then this line below executes. Make sure that your plugin's <script> tag
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// appears after the one from converse.js.
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factory(converse);
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}
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}(this, function (converse) {
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converse.plugins.add('myplugin', {
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initialize: function () {
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// This method gets called once converse.initialize has been called
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// and the plugin itself has been loaded.
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// Inside this method, you have access to the closured
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// _converse object as an attribute on "this".
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// E.g. this._converse
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},
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});
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});
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Accessing 3rd party libraries
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Immediately inside the module shown above you can access 3rd party libraries (such
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moment, underscore and jQuery) via the ``converse.env`` map.
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The code for it would look something like this:
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.. code-block:: javascript
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// Commonly used utilities and variables can be found under the "env"
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// namespace of the "converse" global.
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var Strophe = converse.env.Strophe,
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$iq = converse.env.$iq,
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$msg = converse.env.$msg,
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$pres = converse.env.$pres,
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$build = converse.env.$build,
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b64_sha1 = converse.env.b64_sha1;
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$ = converse.env.jQuery,
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_ = converse.env._,
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moment = converse.env.moment;
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These dependencies are closured so that they don't pollute the global
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namespace, that's why you need to access them in such a way inside the module.
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Overrides
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---------
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Plugins can override core code or code from other plugins. Refer to the full
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example at the bottom for code details.
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Use the ``overrides`` functionality with caution. It basically resorts to
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monkey patching which pollutes the call stack and can make your code fragile
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and prone to bugs when Converse.js gets updated. Too much use of ``overrides``
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is therefore a "code smell" which should ideally be avoided.
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A better approach is to listen to the events emitted by Converse.js, and to add
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your code in event handlers. This is however not always possible, in which case
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the overrides are a powerful tool.
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.. _`optional_dependencies`:
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Optional plugin dependencies
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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When using ``overrides``, the code that you want to override (which is either
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in ``converse-core`` or in other plugins), needs to be loaded already by the
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type the ``overrides`` object is being parsed.
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So it's important to include overridden plugins in the AMD ``define`` statement
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at the top of the plugin module.
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However, sometimes you want to override parts of another plugin if it exists, but you
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don't want anything to break if it doesn't exist (for example when using a
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custom build which excludes that plugin). An example is the
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`converse-dragresize <https://github.com/jcbrand/converse.js/blob/master/src/converse-dragresize.js>`_
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plugin, which will add drag-resize handles to the headlines box (which shows
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messages of type ``headline``) but doesn't care if that particular plugin isn't
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actually loaded.
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In this case, you can't specify the plugin as a dependency in the ``define``
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statement at the top of the plugin, since it might not always be available,
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which would cause ``require.js`` to throw an error.
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To resolve this problem we have the ``optional_dependencies`` Array attribute.
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With this you can specify those dependencies which need to be loaded before
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your plugin, if they exist. If they don't exist, they won't be ignored.
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If the setting :ref:`strict_plugin_dependencies` is set to true,
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an error will be raised if the plugin is not found, thereby making them
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non-optional.
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Extending converse.js's configuration settings
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Converse.js comes with various :ref:`configuration-settings`_ that can be used to
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modify its functionality and behavior.
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All configuration settings have default values which can be overridden when
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`converse.initialize` (see :ref:`initialize`_) gets called.
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Plugins often need their own additional configuration settings and you can add
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these settings with the `_converse.api.settings.update` method (see
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:ref:`settings-update`_).
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Exposing promises
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~~~~~~~~~~~~~~~~~
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Converse.js has a ``waitUntil`` API method (see :ref:`waituntil-grouping`_)
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which allows you to wait for various promises to resolve before executing a
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piece of code.
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You can add new promises for your plugin by calling
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``_converse.api.promises.add`` (see :ref:`promises-grouping`_).
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Generally, your plugin will then also be responsible for making sure these
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promises are resolved. You do this by calling ``_converse.api.emit``, which not
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only resolves the plugin but will also emit an event with the same name.
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Dealing with asynchronicity
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---------------------------
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Due to the asynchronous nature of XMPP, many subroutines in Converse.js execute
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at different times and not necessarily in the same order.
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In many cases, when you want to execute a piece of code in a plugin, you first
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want to make sure that the supporting data-structures that your code might rely
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on have been created and populated with data.
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There are two ways of waiting for the right time before executing your code.
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You can either listen for certain events, or you can wait for promises to
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resolve.
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For example, in the ``Bookmarks`` plugin (in
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`src/converse-bookmarks.js <https://github.com/jcbrand/converse.js/blob/6c3aa34c23d97d679823a64376418cd0f40a8b94/src/converse-bookmarks.js#L528>`_),
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before bookmarks can be fetched and shown to the user, we first have to wait until
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the `"Rooms"` panel of the ``ControlBox`` has been rendered and inserted into
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the DOM. Otherwise we have no place to show the bookmarks yet.
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Therefore, there are the following lines of code in the ``initialize`` method of
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`converse-bookmarks.js <https://github.com/jcbrand/converse.js/blob/6c3aa34c23d97d679823a64376418cd0f40a8b94/src/converse-bookmarks.js#L528>`_:
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.. code-block:: javascript
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Promise.all([
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_converse.api.waitUntil('chatBoxesFetched'),
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_converse.api.waitUntil('roomsPanelRendered')
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]).then(initBookmarks);
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What this means, is that the plugin will wait until the ``chatBoxesFetched``
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and ``roomsPanelRendered`` promises have been resolved before it calls the
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``initBookmarks`` method (which is defined inside the plugin).
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This way, we know that we have everything in place and set up correctly before
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fetching the bookmarks.
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As another example, there is also the following code in the ``initialize``
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method of the plugin:
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.. code-block:: javascript
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_converse.on('chatBoxOpened', function renderMinimizeButton (view) {
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// Inserts a "minimize" button in the chatview's header
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// Implementation code removed for brevity
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// ...
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});
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In this case, the plugin waits for the ``chatBoxOpened`` event, before it then
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calls ``renderMinimizeButton``, which adds a new button to the chat box (which
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enables you to minimize it).
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Finding the right promises and/or events to listen to, can be a bit
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challenging, and sometimes it might be necessary to create new events or
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promises.
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Please refer to the :ref:`events-API` section of the documentation for an
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overview of what's available to you. If you need new events or promises, then
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`please open an issue or make a pull request on Github <https://github.com/jcbrand/converse.js>`_
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A full example plugin
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---------------------
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Below follows a documented example of a plugin. This is the same code that gets
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generated by `generator-conversejs <https://github.com/jcbrand/generator-conversejs>`_.
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.. code-block:: javascript
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(function (root, factory) {
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if (typeof define === 'function' && define.amd) {
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// AMD. Register as a module called "myplugin"
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define("<%= name %>", ["converse"], factory);
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} else {
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// Browser globals. If you're not using a module loader such as require.js,
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// then this line below executes. Make sure that your plugin's <script> tag
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// appears after the one from converse.js.
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factory(converse);
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}
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}(this, function (converse) {
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// Commonly used utilities and variables can be found under the "env"
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// namespace of the "converse" global.
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var Strophe = converse.env.Strophe,
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$iq = converse.env.$iq,
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$msg = converse.env.$msg,
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$pres = converse.env.$pres,
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$build = converse.env.$build,
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b64_sha1 = converse.env.b64_sha1;
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$ = converse.env.jQuery,
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_ = converse.env._,
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moment = converse.env.moment;
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// The following line registers your plugin.
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converse.plugins.add("<%= name %>", {
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/* Optional dependencies are other plugins which might be
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* overridden or relied upon, and therefore need to be loaded before
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* this plugin. They are called "optional" because they might not be
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* available, in which case any overrides applicable to them will be
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* ignored.
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*
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* NB: These plugins need to have already been loaded via require.js.
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*
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* It's possible to make optional dependencies non-optional.
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* If the setting "strict_plugin_dependencies" is set to true,
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* an error will be raised if the plugin is not found.
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*/
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'optional_dependencies': [],
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/* Converse.js's plugin mechanism will call the initialize
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* method on any plugin (if it exists) as soon as the plugin has
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* been loaded.
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*/
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'initialize': function () {
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/* Inside this method, you have access to the private
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* `_converse` object.
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*/
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var _converse = this._converse;
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_converse.log("The <%= name %> plugin is being initialized");
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/* From the `_converse` object you can get any configuration
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* options that the user might have passed in via
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* `converse.initialize`. These values are stored in the
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* "user_settings" attribute.
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*
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* You can also specify new configuration settings for this
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* plugin, or override the default values of existing
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* configuration settings. This is done like so:
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*/
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_converse.api.settings.update({
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'initialize_message': 'Initializing <%= name %>!'
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});
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/* The user can then pass in values for the configuration
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* settings when `converse.initialize` gets called.
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* For example:
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*
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* converse.initialize({
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* "initialize_message": "My plugin has been initialized"
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* });
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*
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* And the configuration setting is then available via the
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* `user_settings` attribute:
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*/
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alert(this._converse.user_settings.initialize_message);
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/* Besides `_converse.api.settings.update`, there is also a
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* `_converse.api.promises.add` method, which allows you to
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* add new promises that your plugin is obligated to fulfill.
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*
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* This method takes a string or a list of strings which
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* represent the promise names:
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*
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* _converse.api.promises.add('myPromise');
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*
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* Your plugin should then, when appropriate, resolve the
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* promise by calling `_converse.api.emit`, which will also
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* emit an event with the same name as the promise.
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* For example:
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*
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* _converse.api.emit('operationCompleted');
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*
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* Other plugins can then either listen for the event
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* `operationCompleted` like so:
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*
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* _converse.api.listen.on('operationCompleted', function { ... });
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*
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* or they can wait for the promise to be fulfilled like so:
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*
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* _converse.api.waitUntil('operationCompleted', function { ... });
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*/
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},
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/* If you want to override some function or a Backbone model or
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* view defined elsewhere in converse.js, then you do that under
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* the "overrides" namespace.
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*/
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'overrides': {
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/* For example, the private *_converse* object has a
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* method "onConnected". You can override that method as follows:
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*/
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'onConnected': function () {
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// Overrides the onConnected method in converse.js
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// Top-level functions in "overrides" are bound to the
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// inner "_converse" object.
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var _converse = this;
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// Your custom code can come here ...
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// You can access the original function being overridden
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// via the __super__ attribute.
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// Make sure to pass on the arguments supplied to this
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// function and also to apply the proper "this" object.
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_converse.__super__.onConnected.apply(this, arguments);
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// Your custom code can come here ...
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},
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/* Override converse.js's XMPPStatus Backbone model so that we can override the
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* function that sends out the presence stanza.
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*/
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'XMPPStatus': {
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'sendPresence': function (type, status_message, jid) {
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// The "_converse" object is available via the __super__
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// attribute.
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var _converse = this.__super__._converse;
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// Custom code can come here ...
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// You can call the original overridden method, by
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// accessing it via the __super__ attribute.
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// When calling it, you need to apply the proper
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// context as reference by the "this" variable.
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this.__super__.sendPresence.apply(this, arguments);
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// Custom code can come here ...
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}
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}
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}
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});
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}));
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