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. 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. ## Other types of hooks Beyond PreProcessorDirectives, Other types of hooks that can be used by plugins include: ### delete IkiWiki::hook(type => "delete", id => "foo", call => \&deletion); 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. ### render IkiWiki::hook(type => "render", id => "foo", call => \&update); Each time ikiwiki renders a change or addition (but not deletion) of a page to the wiki, the referenced function is called, and passed the name of the source file that was rendered. ## Error handing in plugins 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 [[HTMLSanitization]] 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 along with the rest of the page. ## 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. ## 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.