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ALERT! NOTE: This is a DistributionDocument. Please help maintain high quality documentation: This is a wiki, please fix the documentation if you find errors or incomplete content. Put questions and suggestions concerning the documentation of this topic in the comments section below. Use the Support web for problems you are having using TWiki.

TWiki Plugins

Add functionality to TWiki with readily available plugins; create plugins based on APIs

Overview

You can add plugins to extend TWiki functionality, without altering the core code. A plug-in approach lets you:

  • 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;
  • rapidly develop new TWiki functions in Perl using the plugin API.

Everything to do with TWiki plugins - demos, new releases, downloads, development, general discussion - is available at TWiki.org, in the TWiki:Plugins web.

TWiki plugins are developed and contributed by interested members of the community. Plugins are provided on an 'as is' basis; they are not a part of TWiki, but are independently developed and maintained.

Relevant links on TWiki.org:

See other types of extensions: TWikiAddOns, TWikiContribs, TWikiSkins

Installing Plugins

The TWiki:Plugins web on TWiki.org is the repository for TWiki plugins. Each plugin such as the TWiki:Plugins.ChartPlugin has a topic with user guide, step-by-step installation instructions, a detailed description of any special requirements, version details, and a working example for testing. There's usually a number of other related topics, such as a developers page, and an appraisal page.

Most TWiki plugins are packaged so that they can be installed and upgraded using the configure script. To install a plugin, open up the Extensions tab, follow the "Find More Extensions" link, and follow the instructions. A plugin needs to be enabled after installation.

Plugins can also be installed manually: Download the zip or tgz package of a TWiki plugin from the TWiki.org repository, upload it to the TWiki server, unpack it, and follow the installation instructions found in the plugin topic on TWiki.org.

Special Requirements: Some plugins need certain Perl modules to be pre-installed 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. Use the package manager of the server OS (yum, apt-get, rpm, etc) to install dependent libraries.

If available, install CPAN (Comprehensive Perl Archive Network) libraries with the OS package manager. For example, to install IO::Socket::SSL on Fedora/RedHat/CentOS, run yum install perl-IO-Socket-SSL. CPAN modules can also be installed natively, see TWiki:TWiki.HowToInstallCpanModules.

On-Site Pretesting

If you have a mission critical TWiki installation and you are concerned about installing new plugins, you can test new plugins before making them available by creating a second test TWiki installation, and test the plugin there. It is also possible to configure this test TWiki to use the live data. You can allow selected users access to the test area. Once you are satisfied that it won't compromise your primary 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 Performance

The 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 Apache ab utility. Example on Unix:
time wget -qO /dev/null /cgi-bin/view/TWiki06x00/AbcPlugin

TIP 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 Plugins

Some 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/Disabling Plugins

Plugins can be enabled and disabled with the configure script in the Plugins section. An installed plugin needs to be enabled before it can be used.

Plugin Evaluation Order

By 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 spreadsheet CALCs. This can be done with {PluginsOrder} in the plugins section of configure.

Plugin-Specific Settings

Plugins can be configured with 1. preferences settings and/or 2. with configure settings. Older plugins use plugin preferences settings defined in the plugin topic, which is no longer recommended.

1. Use preferences settings:

Adinistrators can set plugin-specific settings in the local site preferences at Main.TWikiPreferences and users can overload them at the web level and page level. This approach is recommended if users should be able to overload settings. For security this is not recommended for system settings, such as a path to an executable. By convention, preferences setting names start with the plugin name in all caps, and an underscore. For example, to set the cache refresh period of the TWiki:Plugins.VarCachePlugin, add this bullet in Main.TWikiPreferences

  • Set VARCACHEPLUGIN_REFRESH = 24

Preferences settings that have been defined in Main.TWikiPreferences can be retrieved anywhere in TWiki with %<pluginname>_<setting>%, such as %VARCACHEPLUGIN_REFRESH%.

To learn how this is done, use the TWiki:Plugins.VarCachePlugin documentation and Perl plugin code as a reference.

2. Use configure settings:

The administrator can set plugin settings in the configure interface. Recommended if only site administrators should be able to change settings. Chose this option to set sensitive or dangerous system settings, such as passwords or path to executables. To define plugin-specific configure settings,

  • Create a Config.spec file in lib/TWiki/Plugins/YourPlugin/ with variables, such as
    $TWiki::cfg{Plugins}{RecentVisitorPlugin}{ShowIP} = 0;
  • In the plugin, use those those variables, such as
    $showIP = $TWiki::cfg{Plugins}{RecentVisitorPlugin}{ShowIP} || 0;

To learn how this is done, use the TWiki:Plugins.RecentVisitorPlugin documentation and Perl plugin code as a reference.

In either case, define a SHORTDESCRIPTION setting in two places:

  • As a setting in the plugin documentation, which is needed for the extension reports on twiki.org. Example:
    • Set SHORTDESCRIPTION = Show recent visitors to a TWiki site
  • As a global Perl package variable in the plugin package, which is needed by TWiki to show info on installed plugins. Example:
    our $SHORTDESCRIPTION = 'Show recent visitors to a TWiki site';

For better performance, make sure you define this in the plugin package:
our $NO_PREFS_IN_TOPIC = 1;

Listing Active Plugins

Plugin status variables let you list all active plugins wherever needed.

This site is running TWiki version TWiki-6.0.0, Mon, 14 Oct 2013, build 26523, plugin API version 6.00

%ACTIVATEDPLUGINS%

On this TWiki site, the enabled plugins are: SpreadSheetPlugin, AutoSectionsPlugin, BackupRestorePlugin, BlackListPlugin, CalendarPlugin, ChartPlugin, ColorPickerPlugin, CommentPlugin, DatePickerPlugin, EditTablePlugin, GaugePlugin, GeoLookupPlugin, HeadlinesPlugin, InterwikiPlugin, JQueryPlugin, LocalCityTimePlugin, PercentCompletePlugin, PreferencesPlugin, QRCodePlugin, RecentVisitorPlugin, RenderListPlugin, SetGetPlugin, ShareMePlugin, SlideShowPlugin, SmiliesPlugin, TWikiDrawPlugin, TWikiOrgPlugin, TablePlugin, TagMePlugin, TinyMCEPlugin, TwistyPlugin, VarCachePlugin, WatchlistPlugin, WysiwygPlugin.

%PLUGINDESCRIPTIONS%

  • SpreadSheetPlugin (2014-09-23, $Rev: 28085 (2014-09-23) $): Add spreadsheet calculation like "$SUM( $ABOVE() )" to TWiki tables or anywhere in topic text
  • AutoSectionsPlugin (2013-10-30, $Rev: 27286 (2014-04-16) $): Automatically make editable sections based on headings
  • BackupRestorePlugin (2013-02-16, $Rev: 25448 (2013-10-14) $): Administrator utility to backup, restore and upgrade a TWiki site
  • BlackListPlugin (2013-02-28, $Rev$): Utility to keep malicious users away from a public TWiki site
  • CalendarPlugin (2012-12-03, 26864): Show a monthly calendar with highlighted events
  • ChartPlugin (2013-05-23, $Rev: 25974 (2013-05-23) $): Visualize TWiki tables with area charts, bar charts, line graphs, scatter charts and sparklines
  • ColorPickerPlugin (2013-02-15, $Rev: 25074 (2013-10-14) $): Color picker, packaged for use in TWiki forms and TWiki applications
  • CommentPlugin (2013-02-10, $Rev: 24977 (2013-10-14) $): Quickly post comments to a page without an edit/preview/save cycle
  • DatePickerPlugin (2013-09-04, $Rev: 26272 (2013-10-14) $): Pop-up calendar with date picker, for use in TWiki forms, HTML forms and TWiki plugins
  • EditTablePlugin (2013-12-03, $Rev: 26647 (2013-12-03) $): Edit TWiki tables using edit fields, date pickers and drop down boxes
  • GaugePlugin (2013-05-16, $Rev: 25944 (2013-05-16) $): Create gauges (graphical or not), typically used for dashboards
  • GeoLookupPlugin (2012-11-21, $Rev: 24174 (2012-11-21) $): Lookup geolocation by IP address or domain name
  • HeadlinesPlugin (2013-11-18, 26619): Show headline news in TWiki pages based on RSS and ATOM news feeds from external sites
  • InterwikiPlugin (2013-02-12, $Rev: 25126 (2013-10-14) $): Text ExternalSite:Page links to a page on an external site based on aliases defined in a rules topic
  • JQueryPlugin (2013-09-28, $Rev: 26439 (2013-10-14) $): jQuery JavaScript library for TWiki
  • LocalCityTimePlugin (2011-07-13, $Rev: 21742 (2011-07-13) $): Shows the local time of a city embedded in a TWiki topic.
  • PercentCompletePlugin (2012-12-05, $Rev: 24337 (2012-12-06) $): Percent complete selector, for use in TWiki forms and TWiki applications
  • PreferencesPlugin (2013-09-08, $Rev: 26286 (2013-10-14) $): Allows editing of preferences using fields predefined in a form
  • QRCodePlugin (2012-11-14, $Rev: 24045 (2012-11-15) $): Create QR Code (a matrix barcode) in TWiki pages, useful for mobile applications
  • RecentVisitorPlugin (2012-12-22, $Rev: 24176 (2012-11-22) $): Show recent visitors to a TWiki site
  • RenderListPlugin (2013-01-28, $Rev: 24820 (2013-10-14) $): Render bullet lists in a variety of formats
  • SetGetPlugin (2013-01-28, $Rev: 24822 (2013-10-14) $): Set and get variables in topics, optionally persistently across topic views
  • ShareMePlugin (2012-12-01, $Rev: 24254 (2012-12-01) $): Icon bar to share a TWiki page on popular social media sites such as Facebook, StumbleUpon, Twitter
  • SlideShowPlugin (2013-04-07, $Rev: 25715 (2013-10-14) $): Create web based presentations based on topics with headings.
  • SmiliesPlugin (2013-01-13, $Rev: 24784 (2013-10-14) $): Render smilies as icons, like  :-)  as smile or  :eek:  as eek!
  • TWikiDrawPlugin (2013-05-17, $Rev: 25952 (2013-05-17) $): Vector drawing editor and clickable maps for diagrams and workflows
  • TWikiOrgPlugin (1.001): TWiki.org specific extensions
  • TablePlugin (2013-09-25, $Rev: 26425 (2013-10-14) $): Control attributes of tables and sorting of table columns
  • TagMePlugin (2014-05-15, $Rev: 27384 (2014-05-15) $): Tag wiki content collectively or authoritatively to find content by keywords
  • TinyMCEPlugin (2013-09-18, $Rev: 26397 (2013-10-14) $): Integration of the Tiny MCE WYSIWYG Editor
  • TwistyPlugin (2013-03-22, $Rev: 25508 (2013-10-14) $): Twisty section JavaScript library to open/close content dynamically
  • VarCachePlugin (2012-11-14, $Rev: 24077 (2012-11-15) $): Cache TWiki variables in selected topics for faster page rendering
  • WatchlistPlugin (2014-05-19, $Rev: 27396 (2014-05-19) $): Watch topics of interest and get notified of changes by e-mail
  • WysiwygPlugin (2013-09-18, $Rev: 26391 (2013-10-14) $): Translator framework for WYSIWYG editors

%FAILEDPLUGINS%

PluginErrors
SpreadSheetPlugin none
AutoSectionsPlugin none
BackupRestorePlugin none
BlackListPlugin none
CalendarPlugin none
ChartPlugin none
ColorPickerPlugin none
CommentPlugin none
DatePickerPlugin none
EditTablePlugin none
GaugePlugin none
GeoLookupPlugin none
HeadlinesPlugin none
InterwikiPlugin none
JQueryPlugin none
LocalCityTimePlugin none
PercentCompletePlugin none
PreferencesPlugin none
QRCodePlugin none
RecentVisitorPlugin none
RenderListPlugin none
SetGetPlugin none
ShareMePlugin none
SlideShowPlugin none
SmiliesPlugin none
TWikiDrawPlugin none
TWikiOrgPlugin none
TablePlugin none
TagMePlugin none
TinyMCEPlugin none
TwistyPlugin none
VarCachePlugin none
WatchlistPlugin none
WysiwygPlugin none
HandlerPlugins
afterCommonTagsHandlerVarCachePlugin
afterEditHandlerWysiwygPlugin
afterRenameHandlerTagMePlugin
WatchlistPlugin
afterSaveHandlerTagMePlugin
WatchlistPlugin
beforeAttachmentSaveHandlerBlackListPlugin
beforeCommonTagsHandlerAutoSectionsPlugin
EditTablePlugin
PreferencesPlugin
TwistyPlugin
VarCachePlugin
WysiwygPlugin
beforeEditHandlerAutoSectionsPlugin
TinyMCEPlugin
WysiwygPlugin
beforeMergeHandlerWysiwygPlugin
beforeSaveHandlerAutoSectionsPlugin
BlackListPlugin
CommentPlugin
WatchlistPlugin
WysiwygPlugin
commonTagsHandlerSpreadSheetPlugin
BackupRestorePlugin
BlackListPlugin
CalendarPlugin
ChartPlugin
CommentPlugin
EditTablePlugin
JQueryPlugin
LocalCityTimePlugin
SlideShowPlugin
SmiliesPlugin
TWikiOrgPlugin
endRenderingHandlerBlackListPlugin
This handler is deprecated - please check for updated versions of the plugins that use it!
initPluginSpreadSheetPlugin
AutoSectionsPlugin
BackupRestorePlugin
BlackListPlugin
CalendarPlugin
ChartPlugin
ColorPickerPlugin
CommentPlugin
DatePickerPlugin
EditTablePlugin
GaugePlugin
GeoLookupPlugin
HeadlinesPlugin
InterwikiPlugin
JQueryPlugin
LocalCityTimePlugin
PercentCompletePlugin
PreferencesPlugin
QRCodePlugin
RecentVisitorPlugin
RenderListPlugin
SetGetPlugin
ShareMePlugin
SlideShowPlugin
SmiliesPlugin
TWikiDrawPlugin
TWikiOrgPlugin
TablePlugin
TagMePlugin
TinyMCEPlugin
TwistyPlugin
VarCachePlugin
WatchlistPlugin
WysiwygPlugin
modifyHeaderHandlerWysiwygPlugin
postRenderingHandlerBlackListPlugin
PreferencesPlugin
WysiwygPlugin
preRenderingHandlerAutoSectionsPlugin
InterwikiPlugin
SmiliesPlugin
TablePlugin
startRenderingHandlerRenderListPlugin
This handler is deprecated - please check for updated versions of the plugins that use it!
34 plugins

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.

ALERT! 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 the lib/TWiki/Plugins/EmptyPlugin.pm module.

  • All but the initPlugin are commented out. To enable a callback, remove the leading # from all lines of the callback.

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

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 eval block like this:
      eval { require IPC::Run }
      return "<font color=\"red\">SamplePlugin: Can't load required modules ($@)</font>" if $@;
  • Keep the main plugin package as small as possible; create other packages that are loaded if and only if they are used. For example, create sub-packages of BathPlugin in lib/TWiki/Plugins/BathPlugin/.
  • Avoid using preferences in the plugin topic; Define $NO_PREFS_IN_TOPIC in your plugin package as that will stop TWiki from reading the plugin topic for every page. Use Config.spec or preferences settings instead. (See details).
  • Use registered tag handlers.
  • Measure the performance to see the difference.

Version Detection

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

  • All plugin packages require a $VERSION variable. This should be an integer, or a subversion version id.

  • The initPlugin handler should check all dependencies and return 1 if the initialization is OK or 0 if something went wrong.
    • The plugin initialization code does not register a plugin that returns 0 (or that has no initPlugin handler).

  • $TWiki::Plugins::VERSION in the TWiki::Plugins module contains the TWiki plugin API version, currently 6.00.
    • You can also use the %PLUGINVERSION{}% variable to query the plugin API version or the version of installed plugins.

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::cfg hash than adding it as preferences in the plugin topic.
  • 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 provides the programming interface for TWiki. Understanding how TWiki is working at high level is beneficial for plugin development.

Anatomy of a Plugin

A (very) basic TWiki plugin consists of two files:

  • a Perl module, e.g. MyFirstPlugin.pm
  • a documentation topic, e.g. MyFirstPlugin.txt

The Perl module can be a block of code that talks to 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. In particular, files that should be web-accessible (graphics, Java applets ...) are best placed as attachments of the 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.

The TWiki:Plugins.BuildContrib module provides a lot of support for plugins development, including a plugin creator, automatic publishing support, and automatic installation script writer. If you plan on writing more than one plugin, you probably need it.

Creating the Perl Module

Copy file lib/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();

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:

  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
    • Cancel the edit
    • go back to your site to the TWiki06x00 web
    • In the JumpBox enter your plugin name, for example MyFirstPlugin, press enter and create the new topic
    • paste & save new plugin topic on your site
  2. 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.
  3. Document the performance data you gathered while measuring the performance
  4. 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.>"

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 in Plugin, ex: MyFirstPlugin.pm, and a documentation page with the same name(MyFirstPlugin.txt).

  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

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.

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:

  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
    • paste in the topic text from Writing the Documentation Topic and save
  2. Attach the distribution zip file to the topic, ex: MyFirstPlugin.zip
  3. 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.)
  4. Put the plugin into the SVN repository, see TWiki:Plugins/ReadmeFirst (optional)

NEW 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 smile

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 the TWiki::Func::getWorkArea() function, which gives you a persistent 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 the TWiki::Func::saveAttachment() function to store the data.

Recommendation for file name:

  • Prefix the filename with an underscore (the leading underscore avoids a name clash 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: _GaugePlugin_img123.gif

Web specific data can be stored in the plugin's attachment area, which is web accessible. Use the 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

Integrating with configure

Some TWiki extensions have setup requirements that are best integrated into configure rather than trying to use TWiki preferences variables. These extensions use Config.spec files to publish their configuration requirements.

Config.spec files are read during TWiki configuration. Once a Config.spec has defined a configuration item, it is available for edit through the standard configure interface. Config.spec files are stored in the 'plugin directory' e.g. lib/TWiki/Plugins/BathPlugin/Config.spec.

Structure of a Config.spec file

The Config.spec file for an extension starts with the extension announcing what it is:
# ---+ Extensions
# ---++ BathPlugin
# This plugin senses the level of water in your bath, and ensures the plug
# is not removed while the water is still warm.
This is followed by one or more configuration items. Each configuration item has a type, a description and a default. For example:
# **SELECT Plastic,Rubber,Metal**
# Select the plug type
$TWiki::cfg{BathPlugin}{PlugType} = 'Plastic';

# **NUMBER**
# Enter the chain length in cm
$TWiki::cfg{BathPlugin}{ChainLength} = 30;

# **BOOLEAN EXPERT**
# Set this option to 0 to disable the water temperature alarm
$TWiki::cfg{BathPlugin}{TempSensorEnabled} = 1;
The type (e.g. **SELECT** ) tells configure to how to prompt for the value. It also tells configure how to do some basic checking on the value you actually enter. All the comments between the type and the configuration item are taken as part of the description. The configuration item itself defines the default value for the configuration item. The above spec defines the configuration items $TWiki::cfg{BathPlugin}{PlugType}, $TWiki::cfg{BathPlugin}{ChainLength}, and $TWiki::cfg{BathPlugin}{TempSensorEnabled} for use in your plugin. For example,
if( $TWiki::cfg{BathPlugin}{TempSensorEnabled} && $curTemperature > 50 ) {
    die "The bathwater is too hot for comfort";
}

The Config.spec file is read by configure, which then writes LocalSite.cfg with the values chosen by the local site admin.

A range of types are available for use in Config.spec files:

BOOLEAN A true/false value, represented as a checkbox
COMMAND length A shell command
LANGUAGE A language (selected from {LocalesDir}
NUMBER A number
OCTAL An octal number
PASSWORD length A password (input is hidden)
PATH length A file path
PERL A perl structure, consisting of arrays and hashes
REGEX length A perl regular expression
SELECT choices Pick one of a range of choices
SELECTCLASS root Select a perl package (class)
STRING length A string
URL length A url
URLPATH length A relative URL path

All types can be followed by a comma-separated list of attributes.

EXPERT means this an expert option
M means the setting is mandatory (may not be empty)
H means the option is not visible in configure

See lib/TWiki.spec for many more examples.

Config.spec files for non-plugin extensions are stored under the Contrib directory instead of the Plugins directory.

Note that from TWiki 5.0 onwards, CGI scripts (in the TWiki bin directory) provided by extensions must also have an entry in the Config.spec file. This entry looks like this (example taken from PublishContrib)

# **PERL H**
# Bin script registration - do not modify
$TWiki::cfg{SwitchBoard}{publish} = [ "TWiki::Contrib::Publish", "publish", { publishing => 1 } ];
PERL specifies a perl data structure, and H a hidden setting (it won't appear in configure). The first field of the data value specifies the class where the function that implements the script can be found. The second field specifies the name of the function, which must be the same as the name of the script. The third parameter is a hash of initial context settings for the script.

TWiki:TWiki/SpecifyingConfigurationItemsForExtensions has supplemental documentation on configure settings.

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 in Dev, 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 plugin handlers) evolve over time. TWiki introduces new API functions to address the needs of plugin authors. Plugins using unofficial TWiki internal functions may no longer work on a TWiki upgrade.

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 fulfilled if plugins are maintained in a compatible manner.

TIP 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. Here is an example; the TWiki:TWiki.TWikiPluginsSupplement#MaintainPlugins has more details.

    if( $TWiki::Plugins::VERSION >= 1.1 ) {
        @webs = TWiki::Func::getListOfWebs( 'user,public' );
    } else {
        @webs = TWiki::Func::getPublicWebList( );
    }

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 the TWiki::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:Main.MikeMannix, TWiki:Main.CrawfordCurrie, TWiki:Main.ArthurClemens, TWiki:Main.WillNorris



Comments & Questions about this Distribution Document Topic

Please add this blurb (or something like it) to the documentation.

If your plugin uses its own modules and objects, you must include the name of the plugin in the package name. E.G. do not do:
package Attrs;
sub new {...}
Instead use:
Package Myplugin::Attrs;
sub new {...}
Then call it using:
   use TWiki::Plugins::Myplugin::Attrs;
  $var = Myplugin::Attrs->new();
rather than:
   use TWiki::Plugins::Myplugin::Attrs;
   $var = Attrs->new();

If you don't do this it will cause lots of warning messages about the module functions being redefined especially in mod_perl environments, and can cause your plugin to work incorrectly if a later plugin overrides your definitions.

We have this problem right now with the ActionTracker and TOC plugins.

-- JohnRouillard - 27 Aug 2002

Thanks John, I added a shortened version.

-- PeterThoeny - 29 Jan 2003

Shouldn't Codev.StepByStepRenderingOrder be moved to the TWiki web if it's going to be linked to from here? (I'm thinking of when this page is included in a distribution)

-- SamHasler - 26 Nov 2003

Correct. It needs to be updated as well to the latest version. For now I changed it into a Interwiki link. I made some more changes to the text, mainly to improve the flow of the text.

-- PeterThoeny - 12 Dec 2003

Crawford, I reverted "If you use a subdirectory, then name it the same as the plugin with a leading underscore; for example, _MyPlugin" back to "Do not use subdirectories (rename and delete would fail)". This spec change should be agreed on before in Codev and it needs to be investiated if it does not break existing functionality (like rename)

-- PeterThoeny - 28 Mar 2004

Looks like this comment area hasn't been used in awhile. Here goes:

Working on a new plugin, we discovered that blanks are converted into tabs, then from tabs back to blanks -- which really threw us off. The only place I found reference to this is in StepByStepRenderingOrder. QUESTIONS:

  • Why is this?
  • Why is it necessary to go to tabs, then back again?
  • Is there a way to supress this behavior from a plugin level?

Thanks!

-- SteveRJones - 09 Jun 2005

How can I remove an installed plugin?

-- BaoguiHuang - 27 Sep 2005

Please ask support questions in the Support web. To remove a Plugin, delete XyzPlugin.pm (and possibly =XyzPlugin subdirectory) in lib/TWiki/Plugins and delete the Plugin topic.

-- PeterThoeny - 27 Sep 2005

According to TWikiPreferences, DISABLEDPLUGINS and ENABLEDPLUGINS are no longer supported, and the way to test plugins is to use the debugenableplugins URL parameter. This document should probably be updated to reflect that. I'm only just trying to write my first plugin, so I don't really feel qualified to rewrite the document at this point.

-- DougClaar - 09 May 2006

I just updated the doc to the TWiki 4 version.

-- PeterThoeny - 13 May 2006

Since not all platforms have .zip support, it would be nice to at least suggest that plugin developers provide both .zip and .tgz versions of their plugins. It would be even nicer if this website provided a means to convert between the two when attaching a plugin as well, to simplify the lives of plugin developers.

-- JamesParker - 22 Sep 2006

.zip and .tgz are attached if the build script is used to upload a plugin. See BuildContrib.

-- PeterThoeny - 23 Sep 2006

Is TWiki:Codev/StepByStepRenderingOrder for T4? I am looking at upgrading a plugin from T3 and T4 and it seems like that the order is no longer accurate.

Specifically, I am seeing the handle called for the Template before the topic, which I can't populate, since I haven't been given the topic text yet.

Does anyone have any current information? Thanks.

-- EricHanson - 09 Oct 2006

The referenced topic is out of date, it applies to BeijingRelease. I suggest to open a Support question.

-- PeterThoeny - 09 Oct 2006

It would be nice if NewPluginTemplate made use of the TopicCreatePlugin to create the Dev and the Appraisal topics at the same time.

If the TopicCreatePlugin was enabled on twiki.org (or just the Plugins web), then I would be happy to do this.

-- AndrewRJones - 05 Jun 2007

Thanks for the offer. I installed and enabled this plugin on TWiki.org, please go ahead.

-- PeterThoeny - 23 Jun 2007

This document mentions several times the topic SpecifyingConfigurationItemsForExtensions for specifying configuration settings for a plugin. Apparently, this topic does not exist, yet. Is there any other place where the structure of a Config.spec file is documented?

-- LutzGehlen - 28 Jan 2008

Ah, I saw now that only the links where not working. I removed the %TWIKIWEB% from all links to SpecifyingConfigurationItemsForExtensions, now the links work. Hope this was indeed improving and not messing up the document.

-- LutzGehlen - 28 Jan 2008

I merged the changes from svn with changes on this topic.

-- PeterThoeny - 20 Apr 2008

Please use the Support forum if you have questions about TWiki features. This comment section is about the documentation of this topic.
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