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ikiwiki [[plugins]] are written in perl. Each plugin is a perl module, in the IkiWiki::Plugin namespace. The name of the plugin is typically in lowercase, such as IkiWiki::Plugin::inline. Ikiwiki includes a IkiWiki::Plugin::skeleton that can be fleshed out to make a useful plugin. IkiWiki::Plugin::pagecount is another simple example.

Note

One thing to keep in mind when writing a plugin is that ikiwiki is a wiki compiler. So plugins influence pages when they are built, not when they are loaded. A plugin that inserts the current time into a page, for example, will insert the build time. Also, as a compiler, ikiwiki avoids rebuilding pages unless they have changed, so a plugin that prints some random or changing thing on a page will generate a static page that won't change until ikiwiki rebuilds the page for some other reason, like the page being edited.

Registering plugins

Plugins should, when imported, call IkiWiki::hook to hook into ikiwiki's processing. The function uses named parameters, and use varies depending on the type of plugin being registered. Note that a plugin can call the function more than once to register multiple hooks. All calls to IkiWiki::hook should be passed a "type" parameter, which gives the type of hook, a "id" paramter, which should be a unique string for this plugin, and a "call" parameter, which is a reference to a function to call for the hook.

Writing a [[PreProcessorDirective]]

This is probably the most common use of a plugin.

    IkiWiki::hook(type => "preprocess", id => "foo", call => \&preprocess);

Replace "foo" with the command name that will be used inside brackers for the preprocessor directive.

Each time the directive is processed, the referenced function (preprocess in the example above) is called, and is passed named parameters. A "page" parameter gives the name of the page that embedded the preprocessor directive, while a "destpage" parameter gices the name of the page the content is going to (different for inlined pages). All parameters included in the directive are included as named parameters as well. Whatever the function returns goes onto the page in place of the directive.

Error handing

While a plugin can call ikiwiki's error routine for a fatal error, for errors that aren't intended to halt the entire wiki build, including bad parameters passed to a [[PreProcessorDirective]], etc, it's better to just return the error message as the output of the plugin.

Html issues

Note that if the [[htmlscrubber]] is enabled, html in [[PreProcessorDirective]] output is sanitised, which may limit what your plugin can do. Also, the rest of the page content is not in html format at preprocessor time. Text output by a preprocessor directive will be passed through markdown (or whatever engine is used to htmlize the page) along with the rest of the page.

Other types of hooks

Beyond PreProcessorDirectives, Other types of hooks that can be used by plugins include:

getopt

IkiWiki::hook(type => "getopt", id => "foo", call => \&getopt);

This allows for plugins to perform their own processing of command-line options and so add options to the ikiwiki command line. It's called during command line processing, with @ARGV full of any options that ikiwiki was not able to process on its own. The function should process any options it can, removing them from @ARGV, and probably recording the configuration settings in %IkiWiki::config. It should take care not to abort if it sees an option it cannot process, and should just skip over those options and leave them in @ARGV.

checkconfig

IkiWiki::hook(type => "checkconfig", id => "foo", call => \&checkconfig);

This is useful if the plugin needs to check for or modify ikiwiki's configuration. It's called early in the startup process. The function is passed no values. It's ok for the function to call IkiWiki::error if something isn't configured right.

filter

IkiWiki::hook(type => "filter", id => "foo", call => \&filter);

Runs on the raw source of a page, before anything else touches it, and can make arbitrary changes. The function is passed named parameters page and content and should return the filtered content.

htmlize

IkiWiki::hook(type => "htmlize", id => "ext", call => \&htmlize);

Runs on the raw source of a page and turns it into html. The id parameter specifies the filename extension that a file must have to be htmlized using this plugin. This is how you can add support for new and exciting markup languages to ikiwiki.

pagetemplate

IkiWiki::hook(type => "pagetemplate", id => "foo", call => \&pagetemplate);

Each time a page (or part of a blog page, or an rss feed) is rendered, a [[template|templates]] is filled out. This hook allows modifying that template. The function is passed named parameters. The "page" and "destpage" parameters are the same as for a preprocess hook. The "template" parameter is a HTML::Template object that is the template that will be used to generate the page. The function can manipulate that template object.

The most common thing to do is probably to call $template->param() to add a new custom parameter to the template. Note that in order to be robust, it's a good idea to check whether the template has a variable before trying to set it, as setting a variable that's not present is an error.

if ($template->query(name => 'foo')) {
	$template->param("foo" => "bar");
}

sanitize

IkiWiki::hook(type => "sanitize", id => "foo", call => \&sanitize);

Use this to implement html sanitization or anything else that needs to modify the content of a page after it has been fully converted to html. The function is passed the page content and should return the sanitized content.

delete

IkiWiki::hook(type => "delete", id => "foo", call => \&delete);

Each time a page or pages is removed from the wiki, the referenced function is called, and passed the names of the source files that were removed.

change

IkiWiki::hook(type => "change", id => "foo", call => \&render);

Each time ikiwiki renders a change or addition (but not deletion) to the wiki, the referenced function is called, and passed the names of the source files that were rendered.

cgi

IkiWiki::hook(type => "cgi", id => "foo", call => \&cgi);

Use this to hook into ikiwiki's cgi script. Each registered cgi hook is called in turn, and passed a CGI object. The hook should examine the parameters, and if it will handle this CGI request, output a page and terminate the program.

savestate

IkiWiki::hook(type => "savestate", id => "foo", call => \&savestate);

This hook is called wheneven ikiwiki normally saves its state, just before the state is saved. The function can save other state, modify values before they're saved, etc.

Wiki configuration

A plugin can access the wiki's configuration via the %IkiWiki::config hash. The best way to understand the contents of the hash is to look at [[ikiwiki.setup]], which sets the hash content to configure the wiki.

Wiki data

If your plugin needs to access data about other pages in the wiki. It can use the following hashes, using a page name as the key:

  • %IkiWiki::links lists the names of each page that a page links to, in an array reference.

  • %IkiWiki::pagemtime contains the last modification time of each page

  • %IkiWiki::pagectime contains the creation time of each page

  • %IkiWiki::renderedfiles contains the name of the file rendered by a page

  • %IkiWiki::pagesources contains the name of the source file for a page.

  • %IkiWiki::depends contains a [[GlobList]] that is used to specify other pages that a page depends on. If one of its dependencies is updated, the page will also get rebuilt.

    Many plugins will need to add dependencies to this hash; the best way to do it is by using the IkiWiki::add_depends function, which takes as its parameters the page name and a [[GlobList]] of dependencies to add.

  • %IkiWiki::forcerebuild any pages set as the keys to this hash will be treated as if they're modified and rebuilt.

A note on generating html links

Many plugins need to generate html links and add them to a page. This is done by using the IkiWiki::htmllink function. The usual way to call htmlllink is:

htmllink($page, $page, $link)

Why is $page repeated? Because if a page is inlined inside another, and a link is placed on it, the right way to make that link is actually:

htmllink($page, $destpage, $link)

Here $destpage is the inlining page. A destpage parameter is passed to some of the hook functions above; the ones that are not passed it are not used during inlining and don't need to worry about this issue.

RCS plugins

ikiwiki's support for revision control systems also uses pluggable perl modules. These are in the IkiWiki::RCS namespace, for example IkiWiki::RCS::svn.

Each RCS plugin must support all the IkiWiki::rcs_* functions. See IkiWiki::RCS::Stub for the full list of functions. It's ok if rcs_getctime does nothing except for throwing an error.

See [[about_RCS_backends]] for some more info.