TWiki Plugins

Overview

• add virtually unlimited features while keeping the main TWiki code compact and efficient;
• heavily customize an installation and still do clean updates to new versions of TWiki;

TWiki comes with a set of Plugins as part of the standard installation.

• EmptyPlugin: Is a fully functional module, minus active code; it does nothing and serves as a template for new Plugin development
• CommentPlugin: Allows users to quickly post comments to a page without an edit/preview/save cycle.
• InterwikiPlugin: Use it for shorthand linking to remote sites, ex: TWiki:Plugins expands to TWiki:Plugins on TWiki.org. You can edit the predefined set of of Wiki-related sites, and add your own

1. Download the zip file containing the Plugin, documentation, and any other required files, from TWiki:Plugins.
2. Distribute the files to their proper locations - unzip the zip archive in your TWiki installation directory - if have a standard TWiki installation, this will distribute automatically. Otherwise, place the files according to the directory paths listed on the Plugin top in TWiki:Plugins.

Special Requests: Some Plugins need certain Perl modules to be preinstalled on the host system. Plugins may also use other resources, like graphics, other modules, applications, templates. In these cases, detailed instructions are in the Plugin documentation.

• Doc page: Read all available info about the Plugin; download the attached distribution files.
• Dev page: Post feature requests, bug reports and general dev comments; topic title ends in Dev (SomePluginDev).
• User support: Post installation, how to use type questions (and answers, if you have them) in the TWiki:Support web.

• Method 1: Safely test on-the-fly by creating separate Production and Test branches in your live TWiki installation.
  • Duplicate the twiki/bin and twiki/lib directories for the Test version, and adjust the paths in the new lib/TWiki.cfg. The following directories are shared: twiki/data, twiki/templates and twiki/pub.

• • • If you modify topics using the new features, live users will likely see unfamiliar new META tags showing up on their pages - to avoid this, create and edit test-only topics to try out new features.

• Method 2: List the Plugin being tested in the DISABLEDPLUGINS variable in TWikiPreferences. Redefine the DISABLEDPLUGINS variable in the Sandbox web and do the testing there.

The performance of the system depends on the number of Plugins installed and on the Plugin implementation. Some Plugins impose no measurable performance decrease, some do. For example, outsidePREHandler is an expensive callback function, or a Plugin might use many Perl libraries that need to be initialized with each page view (unless you run mod_perl). It is recommended to measure the performance with and without a new Plugin. Example for Unix:
time wget -qO /dev/null http://www.auai.org/cgi-bin/twiki/view/TWiki/AbcPlugin

Managing Plugins

Setting Preferences

Most Plugins use either the commonTagsHandler or startRenderingHandler for rendering tasks:

• commonTagsHandler: Use it to expand %XYZPLUGIN% and %XYZPLUGIN{...}% variables

TWiki:Codev/StepByStepRenderingOrder helps you decide which rendering handler to use.

• Delay the Plugin initialization to the actual function which is handling the tag. This way all the expensive initialization is done only when needed.
• For example, use an eval block like:
  eval { require IPC::Run }
  

• You could return errors as strings to show what happened
• You can use a flag to avoid running the initialization twice

To eliminate the incompatibility problems bound to arise from active open Plugin development, a Plugin versioning system is provided for automatic compatibility checking.

• The initPlugin handler should check all dependencies and return TRUE if the initialization is OK or FALSE if something went wrong.
  • The Plugin initialization code does not register a Plugin that returns FALSE (or that has no initPlugin handler).

• $TWiki::Plugins::VERSION in the TWiki::Plugins module contains the TWiki Plugin API version, currently 1.025.

Creating Plugins

The DefaultPlugin Alternative

Creating the Perl Module

If your Plugin uses its own modules and objects, you must include the name of the Plugin in the package name. For example, write Package MyFirstPlugin::Attrs; instead of just Package Attrs;. Then call it using:

Writing the Documentation Topic

1. Copy the Plugin topic template from TWiki.org. To copy the text, go to TWiki:Plugins/PluginPackage and:
   • enter the Plugin name in the "How to Create a Plugin" section

• • paste & save new Plugin topic on your site

1. Customize your Plugin topic.
   • In case you plan to publish your Plugin at TWiki.org, use Interwiki names for author names, like TWiki:Main/TWikiGuest.

OUTLINE: Doc Topic Contents

Syntax Rules: <Describe any special text formatting that will be rendered.>"

1. Post the Plugin documentation topic in the TWiki:Plugins/PluginPackage:
   • enter the Plugin name in the "How to Create a Plugin" section, for example MyFirstPlugin

1. Attach the distribution zip file to the topic, ex: MyFirstPlugin.zip
2. Link from the doc page to a new, blank page named after the Plugin, and ending in Dev, ex: MyFirstPluginDev. This is the discussion page for future development. (User support for Plugins is handled in TWiki:Support.)
3. Put the Plugin into the CVS repository, see TWiki:Plugins/ReadmeFirst (optional)

Where to store Plugin Internal Data

• • Installweb refers to the name of the web where the Plugin is installed

• The filename should start with an underscore, followed by an identifier, e.g. _any_name.ext
  • The leading underscore avoids a nameclash with files attached to the Plugin topic
  • Use only alphanumeric characters, underscores and periods to avoid platform dependency issues and URL issues

Where to Store Data for Topics using the Plugin

• The filename should start with an underscore, followed by the Plugin name, an underscore and an identifier, e.g. _FooBarPlugin_any_name.ext
  • The leading underscore avoids a nameclash with files attached to the same topic
  • Use only alphanumeric characters, underscores and periods to avoid platform dependency issues and URL issues