<<O>>  Difference Topic TWikiPlugins (r1.30 - 02 Mar 2006 - DmitryNPopov?)

TWiki Plugins

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Overview

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You can add Plugins to extend TWiki's functionality, without altering the core program code. A plug-in approach lets you:
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You can add Plugins to extend TWiki"s functionality, without altering the core program 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;
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TWiki comes with a set of Plugins as part of the standard installation.

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  • 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.)
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  • DefaultPlugin: Optionally handles some legacy variables from older versions of TWiki. You can control this option from TWikiPreferences. (Perl programmers can also #DefaultPluginAltadd 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
  • 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
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Most Plugins can be installed in three easy steps, with no programming skills required:
  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.
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  1. Check the demo example on the Plugin topic: if it's working, the installation was fine!
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  1. Check the demo example on the Plugin topic: if it"s working, the installation was fine!

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

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Each Plugin has a standard release page, located in the TWiki:Plugins web at TWiki.org. In addition to the documentation topic (SomePlugin), there's a separate development page.
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Each Plugin has a standard release page, located in the TWiki:Plugins web at TWiki.org. In addition to the documentation topic (SomePlugin), there"s a separate development page.

  • Doc page: Read all available info about the Plugin; download the attached distribution files.
  • Dev page: Post feature requests, bug reports and general dev comments; topic title ends in Dev (SomePluginDev).
  • User support: Post installation, how to use type questions (and answers, if you have them) in the TWiki:Support web.
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  • Method 1: Safely test on-the-fly by creating separate Production and Test branches in your live TWiki installation.
    • Duplicate the twiki/bin and twiki/lib directories for the Test version, and adjust the paths in the new lib/TWiki.cfg. The following directories are shared: twiki/data, twiki/templates and twiki/pub.
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    • Test Plugins and other new features in the Test installation until you're satisfied.
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    • Test Plugins and other new features in the Test installation until you"re satisfied.

      • ALERT! 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.
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    • Copy the modified files to the Production installation. You can update a TWiki installation live and users won't even notice.
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    • Copy the modified files to the Production installation. You can update a TWiki installation live and users won"t even notice.

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

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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.)
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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.)

Managing Plugins

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When you finish installing a Plugin, you should be able to read the user instructions and go. In fact, 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.
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When you finish #InstallPlugininstalling a Plugin, you should be able to read the user instructions and go. In fact, 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.

Setting Preferences

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

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

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  • 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 }
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return "<font color=\"red\">SamplePlugin: Can't load required modules ($@)</font>" if $@;
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return "<font color=\"red\">SamplePlugin: Can"t load required modules ($@)</font>" if $@;

  • You could return errors as strings to show what happened
  • You can use a flag to avoid running the initialization twice
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To eliminate the incompatibility problems bound to arise from active open Plugin development, a Plugin versioning system is provided for automatic compatibility checking.

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

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

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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.
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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 #PluginAPITWiki Plugin API Plugins by providing a programming interface for TWiki.

The DefaultPlugin Alternative

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

Creating the Perl Module

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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.
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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 #PluginAPIPlugin 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:



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Writing the Documentation Topic

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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:
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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 #CreatePluginPackagedistribution 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
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    • 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.
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  1. Save your topic, for use in packaging and publishing your Plugin.
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  1. Save your topic, for use in #CreatePluginPackagepackaging and #PublishPluginpublishing your Plugin.

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

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  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
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    • paste in the topic text from #CreatePluginTopicCreating 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.)
  3. Put the Plugin into the CVS repository, see TWiki:Plugins/ReadmeFirst (optional)
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Where to store Plugin Internal Data

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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.
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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.

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  • The Plugin's attachment directory is pubdir/Installweb/FooBarPlugin
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  • The Plugin"s attachment directory is pubdir/Installweb/FooBarPlugin

    • Installweb refers to the name of the web where the Plugin is installed
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  • The Plugin's attachment URL is %PUBURL%/Installweb/FooBarPlugin
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  • 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
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Where to Store Data for Topics using the Plugin

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

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  • The topic's attachment directory is pubdir/Webname/TopicName
  • The topic's attachment URL is %PUBURL%/Webname/TopicName
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  • 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
Revision r1.29 - 14 Aug 2004 - 08:58 - PeterThoeny
Revision r1.30 - 02 Mar 2006 - 13:37 - DmitryNPopov?