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:
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 ikiwiki 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 => \&filter);
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 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 => \&dele);
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.
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.
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 htmllink() function in ikiwiki. 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.
