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TWiki PluginsAdd functionality to TWiki with readily available Plugins; create Plugins based on APIsOverviewYou can add Plugins to extend TWiki functionality, without altering the core code. A plug-in approach lets you:
Installing PluginsEach TWiki Plugin comes with its own documentation: step-by-step installation instructions, a detailed description of any special requirements, version details, and a working example for testing. Many Plugins have an install script that automates these steps for you. Special Requirements: Some Plugins need certain Perl modules to be preinstalled on the host system. Plugins may also use other resources, like graphics, other modules, applications, and templates. You should be able to find detailed instructions in the Plugin's documentation. Each Plugin has a standard release topic, located in the TWiki:Plugins web at TWiki.org. There's usually a number of other related topics, such as a developers page, and an appraisal page.On-Site PretestingThe recommended approach to testing new Plugins before making them public is to create a second local TWiki installation, and test the Plugin there. You can allow selected users access to the test area. Once you are satisifed that it won't compromise your main installation, you can install it there as well. 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. The%FAILEDPLUGINS% variable can be used to debug failures. You may also want to check your webserver error log and the various TWiki log files.
Some Notes on Plugin PerformanceThe performance of the system depends to some extent on the number of Plugins installed and on the Plugin implementation. Some Plugins impose no measurable performance decrease, some do. For example, a Plugin might use many Perl libraries that need to be initialized with each page view (unless you run mod_perl). You can only really tell the performance impact by installing the Plugin and by measuring the performance with and without the new Plugin. Use the TWiki:Plugins.PluginBenchmarkAddOn, or test manually with the Apacheab utility. Example on Unix:time wget -qO /dev/null /twiki/bin/view/TWiki/AbcPlugin
 If you need to install an "expensive" Plugin, but you only need its functionality only in a subset of your data, you can disable it elsewhere by defining the %DISABLEDPLUGINS% TWiki variable.
Define DISABLEDPLUGINS to be a comma-separated list of names of plugins to disable. Define it in Main.TWikiPreferences to disable those plugins everywhere, in the WebPreferences topic to disable them in an individual web, or in a topic to disable them in that topic. For example,
* Set DISABLEDPLUGINS = SpreadSheetPlugin, EditTablePlugin Managing Installed PluginsSome Plugins require additional settings or offer extra options that you have to select. Also, you may want to make a Plugin available only in certain webs, or temporarily disable it. And may want to list all available Plugins in certain topics. You can handle all of these management tasks with simple procedures:Enabling PluginsPlugins can be enabled and disabled with the configure script. An installed Plugin needs to be enabled before it can be used.Plugin Evaluation OrderBy default, TWiki executes Plugins in alphabetical order on Plugin name. It is possible to change the order, for example to evaluate database variables before the speadsheet CALCs. This can be done with{PluginsOrder} in the Plugins section of configure.
Plugin-Specific SettingsPlugins are usually configured by variables accessible though the configure interface, but in some cases (usually older plugins) TWiki preferences are used. If a TWiki variable is defined in a Plugin topic e.g:
%<pluginname>_<var>%. For example, %RUBBERPLUGIN_SETTING% shows the value of SETTING in the RubberPlugin topic.
Listing Active PluginsPlugin status variables let you list all active Plugins wherever needed.
On this TWiki site, the enabled Plugins are: SpreadSheetPlugin, ActionTrackerPlugin, AttachmentListPlugin, BreadCrumbsPlugin, CalendarPlugin, CommentPlugin, CompareRevisionsAddonPlugin, EditTablePlugin, FilterPlugin, FlexWebListPlugin, FootNotePlugin, GluePlugin, IfDefinedPlugin, InterwikiPlugin, JQueryPlugin, NatSkinPlugin, PreferencesPlugin, RedDotPlugin, RenderListPlugin, SlideShowPlugin, SmiliesPlugin, TablePlugin, TreeBrowserPlugin, TreePlugin, TwistyPlugin, VotePlugin, WysiwygPlugin.
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for = :eek:=| Plugin | Errors |
|---|---|
| SpreadSheetPlugin | none |
| ActionTrackerPlugin | none |
| AttachmentListPlugin | none |
| BreadCrumbsPlugin | none |
| CalendarPlugin | none |
| CommentPlugin | none |
| CompareRevisionsAddonPlugin | none |
| EditTablePlugin | none |
| FilterPlugin | none |
| FlexWebListPlugin | none |
| FootNotePlugin | none |
| GluePlugin | none |
| IfDefinedPlugin | none |
| InterwikiPlugin | none |
| JQueryPlugin | none |
| NatSkinPlugin | none |
| PreferencesPlugin | none |
| RedDotPlugin | none |
| RenderListPlugin | none |
| SlideShowPlugin | none |
| SmiliesPlugin | none |
| TablePlugin | none |
| TreeBrowserPlugin | none |
| TreePlugin | none |
| TwistyPlugin | none |
| VotePlugin | none |
| WysiwygPlugin | none |
| Handler | Plugins |
|---|---|
| afterEditHandler | ActionTrackerPlugin |
| afterSaveHandler | TreePlugin |
| beforeCommonTagsHandler | PreferencesPlugin TwistyPlugin WysiwygPlugin |
| beforeEditHandler | ActionTrackerPlugin WysiwygPlugin |
| beforeSaveHandler | ActionTrackerPlugin CommentPlugin WysiwygPlugin |
| commonTagsHandler | SpreadSheetPlugin ActionTrackerPlugin CalendarPlugin CommentPlugin CompareRevisionsAddonPlugin EditTablePlugin FilterPlugin FootNotePlugin GluePlugin IfDefinedPlugin JQueryPlugin NatSkinPlugin RedDotPlugin SlideShowPlugin SmiliesPlugin |
| initPlugin | SpreadSheetPlugin ActionTrackerPlugin AttachmentListPlugin BreadCrumbsPlugin CalendarPlugin CommentPlugin CompareRevisionsAddonPlugin EditTablePlugin FilterPlugin FlexWebListPlugin FootNotePlugin GluePlugin IfDefinedPlugin InterwikiPlugin JQueryPlugin NatSkinPlugin PreferencesPlugin RedDotPlugin RenderListPlugin SlideShowPlugin SmiliesPlugin TablePlugin TreeBrowserPlugin TreePlugin TwistyPlugin VotePlugin WysiwygPlugin |
| modifyHeaderHandler | WysiwygPlugin |
| postRenderingHandler | EditTablePlugin FootNotePlugin NatSkinPlugin PreferencesPlugin RedDotPlugin TwistyPlugin WysiwygPlugin |
| preRenderingHandler | InterwikiPlugin SmiliesPlugin TablePlugin TreeBrowserPlugin |
| redirectCgiQueryHandler | RedDotPlugin |
| startRenderingHandler | RenderListPlugin This handler is deprecated - please check for updated versions of the plugins that use it! |
The TWiki Plugin API
The Application Programming Interface (API) for TWiki Plugins provides the specifications for hooking into the core TWiki code from your external Perl Plugin module.Available Core Functions
The TWikiFuncDotPm module (lib/TWiki/Func.pm) describes all the interfaces available to Plugins. Plugins should only use the interfaces described in this module.
Note: If you use other core functions not described 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.
Predefined Hooks
In addition to TWiki core functions, Plugins can use predefined hooks, or callbacks, as described in thelib/TWiki/Plugins/EmptyPlugin.pm module.
- All but the initPlugin are disabled. To enable a callback, remove
DISABLE_from the function name.
Hints on Writing Fast Plugins
- Delay initialization as late as possible. For example, if your Plugin is a simple syntax processor, you might delay loading extra Perl modules until you actually see the syntax in the text.
- For example, use an
evalblock like this:
eval { require IPC::Run }
return "<font color=\"red\">SamplePlugin: Can't load required modules ($@)</font>" if $@; - You can use a flag to avoid running the initialization twice
- The TWiki:Plugins.PluginBenchmarkAddOn comes in handy to measure and fine-tune the performance of your Plugin
Plugin Version Detection
To eliminate the incompatibility problems bound to arise from active open Plugin development, a Plugin versioning system is provided for automatic compatibility checking.- All modules require a
$VERSION='0.000'variable, beginning at1.000.
- The
initPluginhandler 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
initPluginhandler).
- The Plugin initialization code does not register a Plugin that returns FALSE (or that has no
-
$TWiki::Plugins::VERSIONin theTWiki::Pluginsmodule contains the TWiki Plugin API version, currently 1.11.- You can also use the
%PLUGINVERSION{}%variable to query the Plugin API version or the version of installed Plugins.
- You can also use the
Security
- Badly written Plugins can open huge security holes in TWiki. This is especially true if care isn't taken to prevent execution of arbitrary commands on the server.
- Don't allow sensitive configuration data to be edited by users. it is better to add sensitive configuration options to the
%TWiki::cfghash than adding it as preferences in the Plugin topic- See TWiki:Plugins.MailInContrib for an example of this
- TWiki:Plugins.BuildContrib can help you with this
- Always use the TWiki::Sandbox to execute commands.
- Always audit the Plugins you install, and make sure you are happy with the level of security provided. While every effort is made to monitor Plugin authors activities, at the end of the day they are uncontrolled user contributions.
Creating 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:
MyFirstPlugin.pm - a documentation topic, ex:
MyFirstPlugin.txt
MyFirstPlugin topic. Other needed Perl code is best placed in a lib/TWiki/Plugins/MyFirstPlugin/ directory.
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.
Creating the Perl Module
Copy filelib/TWiki/Plugins/EmptyPlugin.pm to <name>Plugin.pm. The EmptyPlugin.pm module contains mostly empty functions, so it does nothing, but it's ready to be used. Customize it. Refer to the Plugin API specs for more information.
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();
Measuring and Improving the Plugin Performance
A high quality Plugin performs well. You can use the TWiki:Plugins.PluginBenchmarkAddOn to measure your TWiki:Plugins.PluginBenchmarks. The data is needed as part of the Documentation Topic. See also Hints on Writing Fast Plugins.Writing the 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:- 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
- Cancel the edit
- 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
- Customize your Plugin topic.
- Important: In case you plan to publish your Plugin on TWiki.org, use Interwiki names for author names and links to TWiki.org topics, such as TWiki:Main/TWikiGuest. This is important because links should work properly in a Plugin topic installed on any TWiki, not just on TWiki.org.
- Document the performance data you gathered while measuring the performance
- Save your topic, for use in packaging and publishing your Plugin.
OUTLINE: Doc Topic Contents
Check the Plugins web on TWiki.org for the latest Plugin doc topic template. Here's a quick overview of what's covered: Syntax Rules: <Describe any special text formatting that will be rendered.>" Example: <Include an example of the Plugin in action. Possibly include a static HTML version of the example to compare if the installation was a success!>" Plugin Settings: <Description and settings for custom Plugin %VARIABLES%, and those required by TWiki.>"Plugin Installation Instructions: <Step-by-step set-up guide, user help, whatever it takes to install and run, goes here.>" 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.>"
- 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>
Packaging for Distribution
The TWiki:Plugins.BuildContrib is a powerful build environment that is used by the TWiki project to build TWiki itself, as well as many of the Plugins. You don't have to use it, but it is highly recommended! If you don't want (or can't) use the BuildContrib, then a minimum Plugin release consists of a Perl module with a WikiName that ends inPlugin, ex: MyFirstPlugin.pm, and a documentation page with the same name(MyFirstPlugin.txt).
- 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]
-
- 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
-
Publishing for Public Use
You can release your tested, packaged Plugin to the TWiki community through the TWiki:Plugins web. All Plugins submitted to TWiki.org are available for download and further development in TWiki:Plugins/PluginPackage. Publish your Plugin by following these steps:- 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 - paste in the topic text from Writing the Documentation Topic and save
- enter the Plugin name in the "How to Create a Plugin" section, for example
- Attach the distribution zip file to the topic, ex:
MyFirstPlugin.zip - 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.) - Put the Plugin into the SVN repository, see TWiki:Plugins/ReadmeFirst (optional)
Once you have done the above steps once, you can use the BuildContrib to upload updates to your Plugin.
Thank you very much for sharing your Plugin with the TWiki community 
Recommended Storage of Plugin Specific Data
Plugins sometimes need to store data. This can be Plugin internal data such as cache data, or data generated for browser consumption such as images. Plugins should store data using TWikiFuncDotPm functions that support saving and loading of topics and attachments.Plugin Internal Data
You can create a Plugin "work area" using theTWiki::Func::getWorkArea() function, which gives you a persistant directory where you can store data files. By default they will not be web accessible. The directory is guaranteed to exist, and to be writable by the webserver user. For convenience, TWiki::Func::storeFile() and TWiki::Func::readFile() are provided to persistently store and retrieve simple data in this area.
Web Accessible Data
Topic-specific data such as generated images can be stored in the topic's attachment area, which is web accessible. Use theTWiki::Func::saveAttachment() function to store the data.
Recommendation for file name: - Prefix the filename with an underscore (the leading underscore avoids a nameclash with files attached to the same topic)
- Identify where the attachment originated from, typically by including the Plugin name in the file name
- Use only alphanumeric characters, underscores, dashes and periods to avoid platform dependency issues and URL issues
- Example:
_FooBarPlugin_img123.gif
TWiki::Func::saveAttachment() function to store the data.
Recommendation for file names in Plugin attachment area: - Prefix the filename with an underscore
- Include the name of the web in the filename
- Use only alphanumeric characters, underscores, dashes and periods to avoid platform dependency issues and URL issues
- Example:
_Main_roundedge-ul.gif
Maintaining Plugins
Discussions and Feedback on Plugins
Each published Plugin has a Plugin development topic on TWiki.org. Plugin development topics are named after your Plugin and end inDev, such as MyFirstPluginDev. The Plugin development topic is a great resource to discuss feature enhancements and to get feedback from the TWiki community.
Maintaining Compatibility with Earlier TWiki Versions
The Plugin interface (TWikiFuncDotPm functions and handlers) evolve over time. TWiki 4.0 introduced new API functions to address the needs of Plugin authors. It also deprecated some functions. Some Plugins written for earlier TWiki releases using unofficial TWiki internal functions no longer work on the TWiki 4.0 codebase. All this means that some Plugins need to be updated to work on the TWiki 4.0 codebase. Organizations typically do not upgrade to the latest TWiki for many months. However, many administrators still would like to install the latest versions of a Plugin on their older TWiki installation. This need is fullfilled if Plugins are maintained in a compatible manner. Tip: Plugins can be written to be compatible with older and newer TWiki releases. This can be done also for Plugins using unofficial TWiki internal functions of an earlier release that no longer work on the latest TWiki codebase. TWiki:TWiki.TWikiPluginsSupplement#MaintainPlugins has more.
Handling deprecated functions
From time-to-time, the TWiki developers will add new functions to the interface (either to TWikiFuncDotPm, or new handlers). Sometimes these improvements mean that old functions have to be deprecated to keep the code manageable. When this happens, the deprecated functions will be supported in the interface for at least one more TWiki release, and probably longer, though this cannot be guaranteed. When a plugin defines deprecated handlers, a warning will be shown in the list generated by %FAILEDPLUGINS%. Admins who see these warnings should check TWiki.org and if necessary, contact the plugin author, for an updated version of the plugin. Updated plugins may still need to define deprecated handlers for compatibility with old TWiki versions. In this case, the plugin package that defines old handlers can suppress the warnings in %FAILEDPLUGINS%. This is done by defining a map from the handler name to theTWiki::Plugins version in which the handler was first deprecated. For example, if we need to define the endRenderingHandler for compatibility with TWiki::Plugins versions before 1.1, we would add this to the plugin:
package TWiki::Plugins::SinkPlugin;
use vars qw( %TWikiCompatibility );
$TWikiCompatibility{endRenderingHandler} = 1.1;
If the currently-running TWiki version is 1.1 or later, then the handler will not be called and the warning will not be issued. TWiki with versions of TWiki::Plugins before 1.1 will still call the handler as required.
Related Topics: DeveloperDocumentationCategory, AdminDocumentationCategory, TWiki:TWiki.TWikiPluginsSupplement
-- Contributors: TWiki:Main.PeterThoeny, TWiki:Main.AndreaSterbini, TWiki:MainMikeMannix, TWiki:CrawfordCurrie 
