Add functionality to TWiki with readily available Plugins; create Plugins based on APIs
You can add Plugins to extend TWiki functionality, without altering the core code. A plug-in approach lets you:
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.
Tip: TWiki:TWiki.TWikiPluginsSupplement
on TWiki.org has supplemental documentation on TWiki Plugins.
Each 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.
The 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.
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 /twiki/bin/view/TWiki/AbcPlugin
If 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.)
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:
Plugins can be enabled and disabled with the configure script. An installed Plugin needs to be enabled before it can be used.
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 speadsheet CALCs. This can be done with {PluginsOrder}
in the Plugins section of configure.
Plugin-specific settings are done in individual Plugin topics. Two settings are standard for each Plugin:
Set SHORTDESCRIPTION = Create dynamic foo bar reports
data/debug.txt
. Set to 0=off or 1=on: Set DEBUG = 0
%<pluginname>_<var>%
. For example, %DEFAULTPLUGIN_SHORTDESCRIPTION%
shows the description of the DefaultPlugin.
Plugin status variables let you list all active Plugins wherever needed.
%ACTIVATEDPLUGINS%
%PLUGINDESCRIPTIONS%
"$SUM( $ABOVE() )"
to TWiki tables or anywhere in topic text ExternalSite:Page
links to a page on an external site based on aliases defined in a rules topic :-)
as :eek:
as
%FAILEDPLUGINS%
Plugin | Errors |
---|---|
SpreadSheetPlugin | none |
BackupRestorePlugin | none |
ColorPickerPlugin | none |
CommentPlugin | none |
DatePickerPlugin | none |
EditTablePlugin | none |
HeadlinesPlugin | none |
InterwikiPlugin | none |
JQueryPlugin | none |
PreferencesPlugin | none |
SetGetPlugin | none |
SlideShowPlugin | none |
SmiliesPlugin | none |
TablePlugin | none |
TagMePlugin | none |
TinyMCEPlugin | none |
TwistyPlugin | none |
WysiwygPlugin | none |
Handler | Plugins |
---|---|
afterEditHandler | WysiwygPlugin |
afterRenameHandler | TagMePlugin |
afterSaveHandler | TagMePlugin |
beforeCommonTagsHandler | EditTablePlugin PreferencesPlugin TwistyPlugin WysiwygPlugin |
beforeEditHandler | TinyMCEPlugin WysiwygPlugin |
beforeMergeHandler | WysiwygPlugin |
beforeSaveHandler | CommentPlugin WysiwygPlugin |
commonTagsHandler | SpreadSheetPlugin BackupRestorePlugin CommentPlugin EditTablePlugin HeadlinesPlugin JQueryPlugin SlideShowPlugin SmiliesPlugin |
initPlugin | SpreadSheetPlugin BackupRestorePlugin ColorPickerPlugin CommentPlugin DatePickerPlugin EditTablePlugin HeadlinesPlugin InterwikiPlugin JQueryPlugin PreferencesPlugin SetGetPlugin SlideShowPlugin SmiliesPlugin TablePlugin TagMePlugin TinyMCEPlugin TwistyPlugin WysiwygPlugin |
modifyHeaderHandler | WysiwygPlugin |
postRenderingHandler | EditTablePlugin PreferencesPlugin WysiwygPlugin |
preRenderingHandler | InterwikiPlugin SmiliesPlugin TablePlugin |
The Application Programming Interface (API) for TWiki Plugins provides the specifications for hooking into the core TWiki code from your external Perl Plugin module.
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.
In addition to TWiki core functions, Plugins can use predefined hooks, or callbacks, as described in the lib/TWiki/Plugins/EmptyPlugin.pm
module.
DISABLE_
from the function name.
TWiki:Codev/StepByStepRenderingOrder helps you decide which rendering handler to use.
eval
block like this:eval { require IPC::Run }
return "<font color=\"red\">SamplePlugin: Can't load required modules ($@)</font>" if $@;
To eliminate the incompatibility problems bound to arise from active open Plugin development, a Plugin versioning system is provided for automatic compatibility checking.
$VERSION='0.000'
variable, beginning at 1.000
.
initPlugin
handler should check all dependencies and return TRUE if the initialization is OK or FALSE if something went wrong. initPlugin
handler).
$TWiki::Plugins::VERSION
in the TWiki::Plugins
module contains the TWiki Plugin API version, currently 6.00. %PLUGINVERSION{}%
variable to query the Plugin API version or the version of installed Plugins.
%TWiki::cfg
hash than adding it as preferences in the Plugin topic 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.
A basic TWiki Plugin consists of two elements:
MyFirstPlugin.pm
MyFirstPlugin.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.
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.
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();
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.
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:
MyFirstPlugin
, press enter and create the new topic
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.>"
- 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>
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.>"
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
).
lib/TWiki/Plugins/MyFirstPlugin.pm
data/TWiki/MyFirstPlugin.txt
pub/TWiki/MyFirstPlugin/uparrow.gif
[a required graphic]
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
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:
MyFirstPlugin
MyFirstPlugin.zip
Dev
, ex: MyFirstPluginDev
. This is the discussion page for future development. (User support for Plugins is handled in TWiki:Support
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
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.
You can create a Plugin "work area" using the TWiki::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.
Topic-specific data such as generated images can be stored in the topics attachment area, which is web accessible. Use the TWiki::Func::saveAttachment()
function to store the data.
Recommendation for file name:
_FooBarPlugin_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:
_Main_roundedge-ul.gif
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.
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.
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:MainMikeMannix
, TWiki:CrawfordCurrie