• $TWiki::Plugins::VERSION in the TWiki::Plugins module contains the TWiki Plugin API version, currently 1.025.
  • You can also use the %PLUGINVERSION{}% variable to query the Plugin API version or the version of installed Plugins.

• 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

Checking that Plugins are Working on a Live Server

InstalledPlugins shows which Plugins are: 1) installed, 2) loading properly and 3) what TWiki:Codev.PluginHandlers they invoke. Any failures are shown in the Errors section.

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. Put the Plugin into the CVS repository, see TWiki:Plugins/ReadmeFirst (optional)

Recommended Storage of Plugin Data

Plugins sometimes need to store data. This can be Plugin internal data like cache data, or generated data for the browser like images. The following is a recommendation where to store the data.

Where to store Plugin Internal Data

In case the Plugin generates data just for internal use, or data which is not specific to a topic, store it in the Plugin's attachment directory.

• The Plugin's attachment directory is pubdir/Installweb/FooBarPlugin
  • Installweb refers to the name of the web where the Plugin is installed
• The Plugin's attachment URL is %PUBURL%/Installweb/FooBarPlugin
• 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
  • Do not use subdirectories (rename and delete would fail)
• Use Plugin API functions documented in TWikiFuncModule to ensure portability:
  • Use getPubDir() to get the attachment root directory
  • Use getUrlHost() and getPubUrlPath() to build the URL in case you create content for the browser
  • Use $installWeb to get the name of the web where the Plugin is installed
  • Create the web directory and topic attachment directory if needed
• Hint: Package the Plugin at least with one file attachment. This ensures that the attachment directory already exists

Where to Store Data for Topics using the Plugin

In case the Plugin generates data which is specific to a topic, store it in the topic's attachment directory.

• The topic's attachment directory is pubdir/Webname/TopicName
• The topic's attachment URL is %PUBURL%/Webname/TopicName
• 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
  • Do not use subdirectories (rename and delete would fail)
• Use Plugin API functions documented in TWikiFuncModule to ensure portability:
  • Use getPubDir() to get the attachment root directory
  • Use getUrlHost() and getPubUrlPath() to build the URL in case you create content for the browser

Example code to build the file name:

sub _make_filename
{
    my ( $web, $topic, $name ) = @_;

    # Create web directory "pub/$web" if needed
    my $dir = TWiki::Func::getPubDir() . "/$web";
    unless( -e "$dir" ) {
        umask( 002 );
        mkdir( $dir, 0775 );
    }
    # Create topic directory "pub/$web/$topic" if needed
    $dir .= "/$topic";
    unless( -e "$dir" ) {
        umask( 002 );
        mkdir( $dir, 0775 );
    }
    return "$dir/_FooBarPlugin_$name";
}

-- TWiki:Main/PeterThoeny - 11 Dec 2003
-- TWiki:Main/AndreaSterbini - 29 May 2001
-- TWiki:Main/MikeMannix - 03 Dec 2001

• DefaultPlugin: Optionally handles some legacy variables from older versions of TWiki. You can control this option from TWikiPreferences. (Perl programmers can also add rules for simple custom processing.)
• EmptyPlugin: Is a fully functional module, minus active code; it does nothing and serves as a template for new Plugin development.
• 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.
• EditTablePlugin: Edit TWiki tables using edit fields, date pickers and drop down boxes
• RenderListPlugin: Render bullet lists in a variety of formats
• SlideShowPlugin: Create web based presentations based on topics with headings.
• SmiliesPlugin: Render smilies as icons, like  :-) for or  :cool: for
• SpreadSheetPlugin: Add spreadsheet calculation like "$SUM( $ABOVE() )" to tables located in TWiki topics.
• TablePlugin: Control attributes of tables and sorting of table columns

A Note on Plugin Performance

• commonTagsHandler: Use it to expand %XYZPLUGIN% and %XYZPLUGIN{...}% variables
• startRenderingHandler: Use it for your own rendering rules or to overload TWiki's internal rendering like [[links]]

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

Hints on Writing Fast Plugins

• 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 }
return "<font color=\"red\">SamplePlugin: Can't load required modules ($@)</font>" if $@;
• You could return errors as strings to show what happened
• You can use a flag to avoid running the initialization twice

A Note on Performance

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 needs 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.

In case you need to install an "expensive" Plugin and you need its functionality only in one web you can place the Plugin topic into that web. TWiki will initialize the Plugin only if the Plugin topic is found (which won't be the case for other webs.)

• • 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.

• For best performance, enable only the functions you really need. NOTE: outsidePREHandler and insidePREHandler are particularly expensive.

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:

  use TWiki::Plugins::MyFirstPlugin::Attrs;
  $var = MyFirstPlugin::Attrs->new();

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
   • click Create
   • select all in the Edit box & copy

• • go back to your site to the TWiki web
  • In the GoBox enter your Plugin name, for example MyFirstPlugin, press enter and create the new topic
  • 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.
2. Save your topic, for use in packaging and publishing your Plugin.

• Plugins Preferences <If user settings are needed, explain... Entering values works exactly like TWikiPreferences and WebPreferences: six (6) spaces and then:>"
  • Set <EXAMPLE = value added>

• For best performance, enable only the functions you really need. NOTE: outsidePREHandler and insidePREHandler are particularly expensive.

• 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.

• Plugins Preferences <If user settings are needed, explain... Entering valuse works exactly like TWikiPreferences and WebPreferences: six (6) spaces and then:>"

• 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, adjusting the paths in the new lib/TWiki.cfg, the twiki/data; the twiki/templates and twiki/pub directories are shared.
  • Test Plugins and other new features in the Test installation until you're satisfied.
    • 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.
  • Copy the modified files to the Production installation. You can update a TWiki installation live and users won't even notice.

• DefaultPlugin optionally handles some legacy variables from older versions of TWiki. You can control this option from TWikiPreferences. (Perl programmers can also add rules for simple custom processing.)

• EmptyPlugin is a fully functional module, minus active code; it does nothing and serves as a template for new Plugin development.

• InterwikiPlugin is preinstalled but can be disabled or removed. 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.

• Method 2: List the Plugin under Test in the DISABLEDPLUGINS variable in TWikiPreferences. Redefine the DISABLEDPLUGINS variable in the Test web and do the testing there.

• • Set <EXAMPLE = value added>

OUTLINE: Doc Topic Contents

• InterwikiPlugin is preinstalled but can be disabled or removed. Use it for quick linking to to remote sites: TWiki:Plugins expands to TWiki:Plugins on TWiki.org. You can add your own shortcuts and URLs to the existing directory of Wiki-related and other probably useful sites.

• Dev page: Post feature requests, bug reports and general dev comments; topic title ends in Dev (SomePluginDev).

• • Duplicate the twiki/bin and twiki/lib directories for the Test version, adjusting the paths in the new lib/TWiki.cfg, the twiki/data; the twiki/templates and twiki/pub directories are shared.

• Method 2: List the Plugin under Test in the DISABLEDPLUGINS variable in TWikiPreferences. Redefine the DISABLEDPLUGINS variable in the Test web and do the testing there.

• All Plugin modules present in the lib/TWiki/Plugins directory are activated automatically unless disabled by the DISABLEDPLUGINS Preferences variable in TWikiPreferences. You can optionally list the installed Plugins in the INSTALLEDPLUGINS Preferences variable. This is useful to define the sequence of Plugin execution, or to specify other webs than the TWiki web for the Plugin topics. Settings in TWikiPreferences are:
  • Set INSTALLEDPLUGINS = DefaultPlugin, ...
  • Set DISABLEDPLUGINS = EmptyPlugin, ...

• • Set SHORTDESCRIPTION = Blah blah woof woof.

1. Debug Plugin, output can be seen in data/debug.txt. Set to 0=off or 1=on:
   • Set DEBUG = 0

• The settings can be retrieved as Preferences variables like %<pluginname>_<var>%, ex: %DEFAULTPLUGIN_SHORTDESCRIPTION% shows the description of the DefaultPlugin.

• The %ACTIVATEDPLUGINS% variable lists activated Plugins by name. (This variable is displayed in TWikiPreferences for debugging use.)
• The %PLUGINDESCRIPTIONS% variable displays a bullet list with a one-line description of each active Plugins. This variable is based on the %<plugin>_SHORTDESCRIPTION% Preferences variables of individual topics and is shown in TextFormattingRules.

• For best performance, enable only the functions you really need. NOTE: outsidePREHandler and insidePREHandler are particularly expensive.

• All but the initPlugin are disabled. To enable a call back, remove DISABLE_ from the function name.

• All modules require a $VERSION='0.000' variable, beginning at 1.000.

• 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).

• $VERSION='1.000' is the current setting in TWiki::Plugins.pm and in the preinstalled system Plugins (DefaultPlugin, EmptyPlugin, InterwikiPlugin).

• a Perl module, ex: MyFirstPlugin.pm
• a documentation topic, ex: MyFirstPlugin.txt

• • lib/TWiki/Plugins/MyFirstPlugin.pm
  • data/TWiki/MyFirstPlugin.txt
  • pub/TWiki/MyFirstPlugin/uparrow.gif [a required graphic]

1. Create a zip archive with the Plugin name (MyFirstPlugin.zip) and add the entire directory structure from Step 1. The archive should look like this:
   • lib/TWiki/Plugins/MyFirstPlugin.pm
   • data/TWiki/MyFirstPlugin.txt
   • pub/TWiki/MyFirstPlugin/uparrow.gif

• • create a new topic using the Plugin name, ex: MyFirstPlugin.txt
  • paste in the topic text from Creating Plugin Documentation and save

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.)

• EmptyPlugin is a fully functional module, minus active code; it does nothing and serves as a template for new Plugin development.

• DefaultPlugin can handle some outdated TWiki variables, found, for example, in sites recently updated from an old version. Settings are in DefaultPlugin topic. You can also add your own simple custom processing rules here, though in all but very simple cases, writing a new Plugin is preferable.

• a Perl module, ex: MyFirstPlugin.pm
• a documentation topic, ex: MyFirstPlugin.txt

1. Copy the Plugin topic template from EmptyPlugin. To copy the text, go to the page and:

1. Distribute the Plugin files in a directory structure that mirrors TWiki. If your Plugin uses additional files, include them ALL:
   • lib/TWiki/Plugins/MyFirstPlugin.pm
   • data/TWiki/MyFirstPlugin.txt
   • pub/TWiki/MyFirstPlugin/uparrow.gif [a required graphic]
2. Create a zip archive with the Plugin name (MyFirstPlugin.zip) and add the entire directory structure from Step 1. The archive should look like this:
   • lib/TWiki/Plugins/MyFirstPlugin.pm
   • data/TWiki/MyFirstPlugin.txt
   • pub/TWiki/MyFirstPlugin/uparrow.gif

• • create a new topic using the Plugin name, ex: MyFirstPlugin.txt;

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.)

TWiki Plugins

Overview

Preinstalled Plugins

Installing Plugins

On-Site Pretesting

Managing Plugins

Setting Preferences

Listing Active Plugins

The TWiki Plugin API

Available Core Functions

Predefined Hooks

Plugin Version Detection

Creating Plugins

The DefaultPlugin Alternative

Anatomy of a Plugin

Creating the Perl Module

Writing the Documentation Topic

Packaging for Distribution

Publishing for Public Use

• The initPlugin handler should check all dependencies and return TRUE if the initialization is OK or FALSE if something went wrong.

Overview

You can add Plugins to greatly extend TWiki's functionality, without alering the program core. With a plug-in approach, you can:

• add virtually unlimited features while keeping the main TWiki code compact and efficient;

Preinstalled Plugins

TWiki comes with three Plugins as part of the standard installation.

• DefaultPlugin handles some legacy TWiki variables that may be present in long-established sites. This option can be controlled from TWikiPreferences. (Perl programmers can also add rules for simple custom processing.)

• EmptyPlug is a fully functional module, minus active code; it does nothing and serves as a template for new Plugin development.

• InterwikiPlugin is preinstalled but can be disabled or removed. Use it for quick linking to to remote sites: TWiki:Plugins expands to TWiki:Plugins on TWiki.org. You can add your own shortcuts and URLs to the existing directory of Wiki-related and other probably useful sites.

• Dev page: Post feature requests, bug reports and general dev comments; topic title ends in Dev (SomePluginDev).

On-Site Pretesting

• Method 1: Create Production and a Test installation of TWiki.
  • Duplicate the twiki/bin and twiki/lib directories for the Test version, adjusting the paths in the new lib/TWiki.cfg, the twiki/data; the twiki/templates and twiki/pub directories are shared.
  • Test Plugins and other new features in the Test installation until you're satisfied.
  • Copy the modified files to the Production installation. You can update a live TWiki installation and users won't even notice.

• Method 2: List the Plugin under Test in the DISABLEDPLUGINS variable in TWikiPreferences. Redefine the DISABLEDPLUGINS variable in the Test web and do the testing there.

The TWiki Plugin API

Available Core Functions

• For best performance, enable only the functions you really need. NOTE: outsidePREHandler and insidePREHandler are particularly expensive.

Predefined Hooks

• All but the initPlugin are disabled. To enable a call back, remove DISABLE_ from the function name.

Plugin Version Detection

• All modules require a $VERSION='0.000' variable, beginning at 1.000.

• The initPlugin handler checks all dependencies and returns 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).

• $VERSION='1.000' is the current setting in TWiki::Plugins.pm and in the preinstalled system Plugins (DefaultPlugin, EmptyPlugin, InterwikiPlugin).

Creating Plugins

Anatomy of a Plugin

A basic TWiki Plugin consists of two elements:

• a Perl module, ex: YourPlugin.pm
• a documentation topic, ex: YourPlugin.txt

The Perl module can be a block of code that connects with TWiki alone, or it can include other elements, like other Perl modules (including other Plugins), graphics, TWiki templates, external applications (ex: a Java applet), or just about anything else it can call.

The Plugin API handles the details of connecting your Perl module with main TWiki code. When you're familiar with the Plugin API, you're ready to develop Plugins.

Preinstalled Plugins

Managing Plugins

Setting Preferences

Listing Active Plugins

Creating Plugins

The DefaultPlugin Alternative

Creating the Perl Module

Writing the Documentation Topic

Packaging for Distribution

Publishing for Public Use

• All Plugin modules present in the lib/TWiki/Plugins directory are activated automatically unless disabled by the DISABLEDPLUGINS Preferences variable in TWikiPreferences. You can optionally list the installed Plugins in the INSTALLEDPLUGINS Preferences variable. This is useful to define the sequence of Plugin execution, or to specify other webs than the TWiki web for the Plugin topics. Settings in TWikiPreferences are:

• The %ACTIVATEDPLUGINS% variable lists activated Plugins by name. (This variable is displayed in TWikiPreferences for debugging use.)
• The %PLUGINDESCRIPTIONS% variable displays a bullet list with a one-line description of each active Plugins. This variable is based on the %<plugin>_SHORTDESCRIPTION% Preferences variables of individual topics and is shown in TextFormattingRules.

• Method 2: List the Plugin under test in the DISABLEDPLUGINS variable in TWikiPreferences. Redefine the DISABLEDPLUGINS variable in the test web and do the testing there.

• • paste in the topic text from Creating Plugin Documentation and Save.

TWiki Plugins

About Plugins

• add virtually unlimited features while keeping the main TWiki program compact and efficient;
• heavily customize an installation and still do clean updates to new versions of TWiki;
• rapidly develop new TWiki functions in Perl using the Plugin API.

Installing Plugins

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.
3. Check the demo example on the Plugin topic: if it's working, the installation was fine!

• 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 (ex: SomePluginDev).
• User support: Post installation, how to use type questions (and answers, if you have them) in the TWiki:Support web.

Pre-Installed Plugins

• DefaultPlugin handles some legacy TWiki variables that may be present in long-established sites. This option can be controlled from TWikiPreferences. (Perl programmers can also add rules for simple custom processing.)

• EmptyPlug is a fully functional Plugin module, minus any active code; it does nothing but serve as a template on demand.

• InterwikiPlugin is included but can be disabled or removed. Use it for quick linking to frequently linked to remote sites. Ex: TWiki:Plugins expands to TWiki:Plugins - on TWiki.org. You can add your own shortcuts and URLs to the existing directory of Wiki-related sites.

Managing Installed Plugins

Ideally, after you've installed a Plugin, just read the instructions and you're set. In fact, some Plugins require additional settings or offer extra options that you can modify on Preferences pages. You may want to make a Plugin available only in certain webs, or temporarily disable it. And having to list all available Plugins will probably come up. You can handle all of these with simple procedures.

Set Preferences for Individual Plugins

Installed Plugins can be toggled on or off, site-wide or by web, through TWikiPreferences and individual WebPreferences:

• All Plugin modules present in the lib/TWiki/Plugins directory are activated automatically unless disabled by the DISABLEDPLUGINS Preferences variable in TWikiPreferences. You can optionally list the installed Plugins in the INSTALLEDPLUGINS Preferences variable. This is useful to define the sequence of Plugin execution, or to specify other webs than the TWiki web for the Plugin topics. Settings in TWikiPreferences are:
  • Set INSTALLEDPLUGINS = DefaultPlugin, ...
  • Set DISABLEDPLUGINS = EmptyPlugin, ...

Plugin execution order in TWiki is determined by searching Plugin topics in a specific sequence: First, full web.topicname name, if specified in INSTALLEDPLUGINS; next, the TWiki web is searched; and finally, the current web.

Plugin-specific settings are done in individual Plugin topics. Two settings are standard for each Plugin:

1. One line description, used to form the bullets describing the Plugins in the TextFormattingRules topic:
   • Set SHORTDESCRIPTION = Blah blah woof woof.
2. Debug Plugin, output can be seen in data/debug.txt. Set to 0=off or 1=on:
   • Set DEBUG = 0

• The settings can be retrieved as Preferences variables like %<pluginname>_<var>%, ex: %DEFAULTPLUGIN_SHORTDESCRIPTION% shows the description of the DefaultPlugin.

List Active Plugins Automatically

Plugin status variables let you list all active Plugins wherever needed. There are two list formats:

• The %ACTIVATEDPLUGINS% variable lists activated Plugins by name. (This variable is displayed in TWikiPreferences for debugging use.)
• The %PLUGINDESCRIPTIONS% variable displays a bullet list with a one-line description of each active Plugins. This variable is based on the %<plugin>_SHORTDESCRIPTION% Preferences variables of individual topics and is shown in TextFormattingRules.

DEMO: Active Plugin Variables

%ACTIVATEDPLUGINS%
On this TWiki site, the active Plugins are: DefaultPlugin, SpreadSheetPlugin, CommentPlugin, EditTablePlugin, InterwikiPlugin, RenderListPlugin, SlideShowPlugin, SmiliesPlugin, TablePlugin.

%PLUGINDESCRIPTIONS%
You can use any of these active TWiki Plugins:

• DefaultPlugin: This plugin can be used to specify some simple custom rendering rules. It also renders depreciated *_text_* as bold italic text.
• SpreadSheetPlugin: Add spreadsheet calculation like "$SUM( $ABOVE() )" to tables located in TWiki topics.
• CommentPlugin: Allows users to quickly post comments to a page without an edit/preview/save cycle.
• EditTablePlugin: Edit TWiki tables using edit fields, date pickers and drop down boxes
• InterwikiPlugin: Link ExternalSite:Page text to external sites based on aliases defined in the InterWikis topic
• RenderListPlugin: Render bullet lists in a variety of formats
• SlideShowPlugin: Create web based presentations based on topics with headings.
• SmiliesPlugin: Render smilies as icons, like  :-) for or  :cool: for
• TablePlugin: Control attributes of tables and sorting of table columns

TIP! To test new Plugins on your installation before making them public, you may want to use one of these two approaches:

• Method 1: Create a Production and a Test installation of TWiki. The twiki/data, twiki/templates and twiki/pub directories are shared, and the twiki/bin and twiki/lib directories are separate. Do all tests of Plugins and other new features in the Test installation. When everything works, copy the modified files over to the Production installation. This way, you can update a live TWiki installation and users won't even notice.

• Method 2: List the Plugin under test in the DISABLEDPLUGINS variable in TWikiPreferences. Redefine the DISABLEDPLUGINS variable in the test web and do the testing there.

Creating New Plugins

With a reasonable knowledge of the Perl scripting language, you can create new Plugins or modify and extend existing ones. Basic plug-in architecture uses an Application Programming Interface (API), a set of software instructions that allow external code to interact with the main program. The TWiki Plugin API Plugins by providing a programming interface for TWiki.

Anatomy of a Plugin

A basic TWiki Plugin consists of two elements:

• a Perl module, ex: YourPlugin.pm
• a documentation topic, ex: YourPlugin.txt

The Perl module can be a block of code that connects with TWiki alone, or it can include other elements, like other Perl modules (including other Plugins), graphics, TWiki templates, external applications (ex: a Java applet), or just about anything else it can call.

The Plugin API handles the details of connecting your Perl module with main TWiki code. When you're familiar with the Plugin API, you're ready to develop Plugins.

TWiki Plugin API

The Application Programming Interface (API) for TWikiPlugins provides the specifications for hooking into the core TWiki code from your external Perl Plugin module. The Plugin API is new to the Production version of TWiki with the TWikiReleaseSpring2001.

The lib/TWiki/Func.pm implements ALL official Plugin functions. Plugins should ONLY use functions published in this module.

DevALERT: If you use functions not in Func.pm, you run the risk of creating security holes. Also, your Plugin will likely break and require updating when you upgrade to a new version of TWiki.

In addition to TWiki core functions, Plugins can use predefined hooks, or call backs, listed in the lib/TWiki/Plugins/EmptyPlugin.pm module.

• All but the initPlugin are disabled. To enable a call back, remove DISABLE_ from the function name.

• For improve performance, enable only the functions you really need. NOTE: outsidePREHandler and insidePREHandler are particularly expensive.

Customize the DefaultPlugin

• DefaultPlugin can handle some outdated TWiki variables, found, for example, in sites recently updated from an old version. Settings are in TWikiPreferences. You can also add your own simple custom processing rules here, though in all but very simple cases, writing a new Plugin is preferable.

Create a Plugin Module in Perl

Copy file (EmptyPlugin.pm to <name>Plugin.pm =EmptyPlugin.pm= contains no executable code, so it does nothing, but it's ready to be used. Customize it. Refer to the Plugin API specs for more information.

Create a Plugin Documentation Topic

The Plugin documentation topic contains usage instructions and version details. It serves the Plugin files as FileAttachments for downloading. (The doc topic is also included in the distribution package.) To create a documentation topic:

1. Copy the Plugin topic template from http://TWiki.org/cgi-bin/view/TWiki/EmptyPlugin. To copy the text, go to the page and:
   • click Edit
   • select all in the Edit box & copy
   • Cancel the edit
   • paste & save as a text file or new topic on your site
2. Customize the template for your Plugin; you'll probably want to post a working version on your local TWiki site.
3. Save your topic as a text file, for use in packaging and publishing your Plugin.

OUTLINE: Doc Topic Contents
Check EmptyPlugin on TWiki.org for the latest Plugin doc topic template. Here's a quick overview of what's covered:

Syntax Rules: explanation coming up

YourPlugin Settings: Description and settings for your custom Plugin %VARIABLES%, and those required by TWiki.

Plugins Preferences work exactly like TWikiPreferences and WebPreferences: six (6) spaces and then:

• • Set EXAMPLE = got it!

How-to Instructions: Step-by-step set-up guide, user help, whatever it takes to install and run, goes here.

Test Example: Include an example of the Plugin in action: if it works, the installation was a success!

Plugin Info: Version, credits, history, requirements - entered in a form, displayed as a table. Both are automatically generated when you create or edit a page in the TWiki:Plugins web.

Package a Plugin for Distribution

A minimum Plugin release consists of a Perl module with a WikiName that ends in Plugin, ex: YourPlugin.pm, and a documentation page with the same name(YourPlugin.txt).

1. Distribute your Plugin files in a directory structure that mirrors TWiki. If your Plugin uses additional files, include them ALL:
   • lib/TWiki/Plugins/YourPlugin.pm
   • data/TWiki/YourPlugin.txt
   • pub/TWiki/YourPlugin/uparrow.gif [a required graphic]
2. Create a zip archive with the Plugin name (YourPlugin.zip) and add the entire directory structure from Step 1. Your archive should look like this:
   • lib/TWiki/Plugins/YourPlugin.pm
   • data/TWiki/YourPlugin.txt
   • pub/TWiki/YourPlugin/uparrow.gif

Publish a Plugin for General Use

You can release your tested, packaged Plugin to the TWiki community through the TWiki:Plugins web, where all Plugins submitted to TWiki.org are available for download and further development discussion. Publish your Plugin in three steps:

1. Post the Plugin documentation topic in the TWiki:Plugins web:
   • create a new topic using the Plugin name, ex: YourPlugin.txt;
   • paste in the topic text from How to Create the Plugin Documentation Topic and Save.
2. Attach the distribution zip file to the topic, ex: YourPlugin.zip.
3. Link from the doc page to a new, blank page named after the Plugin, and ending in Dev, ex: YourPluginDev. This is the discussion page for future development. (User support for Plugins is handled in TWiki:Support.)

-- MikeMannix^? - 26 Aug 2001

Plugins under the hood

• All plugin modules that exist in the lib/TWiki/Plugins directory are activated automatically unless disabled by the DISABLEDPLUGINS preferences variable in TWikiPreferences. You can optionally list the installed plugins in the INSTALLEDPLUGINS preferences variable. This is useful to define the sequence of plugin execution, or to specify other webs then the TWiki web for the plugin topics. Settings in TWikiPreferences:
  • Set INSTALLEDPLUGINS = DefaultPlugin, ...
  • Set DISABLEDPLUGINS = EmptyPlugin, ...

• The %ACTIVATEDPLUGINS% variable shows all currently activated plugins. This variable is shown in TWikiPreferences for debug reasons.

• Search order for plugin topics: Full web.topicname name is used if specified in INSTALLEDPLUGINS, then the TWiki web is searched, then the current web.

• Plugin specific settings are done in individual plugin topics. Two settings are standard for each plugin:
  • One line description, used to form the bullets describing the plugins in the TextFormattingRules topic:
    • Set SHORTDESCRIPTION = Blah blah.
  • Debug plugin, output can be seen in data/debug.txt: (Se to 0 or 1)
    • Set DEBUG = 0
  • The settings can be retrieved as preferences variables like %<pluginname>_<var>%, i.e. %DEFAULTPLUGIN_SHORTDESCRIPTION% shows the description of the DefaultPlugin.

• The %PLUGINDESCRIPTIONS% variable shows a bullet list with descriptions of all currently activated plugins. This variable is based on %<plugin>_SHORTDESCRIPTION% preferences variables of individual topics and is shown in TextFormattingRules.

-- PeterThoeny - 14 Jul 2001

TWiki Plugins

How to Create a Plugin

How to Install a Plugin

How to Create a Plugin

under construction... ( check back at http://TWiki.org/cgi-bin/view/TWiki/TWikiPlugins )

How to Install a Plugin

under construction... ( check back at http://TWiki.org/cgi-bin/view/TWiki/TWikiPlugins )

-- PeterThoeny - 17 Feb 2001