it's not really hard. This page is a complete reference to everything a
plugin might want to do. There is also a quick [[tutorial]].
-[[toc levels=2]]
+[[!toc levels=2]]
## Types of plugins
`IkiWiki::Plugin::pagecount` is another simple example. All perl plugins
should `use IkiWiki` to import the ikiwiki plugin interface. It's a good
idea to include the version number of the plugin interface that your plugin
-expects: `use IkiWiki 2.00`.
+expects: `use IkiWiki 3.00`.
An external plugin is an executable program. It can be written in any
language. Its interface to ikiwiki is via XML RPC, which it reads from
Plugins should, when imported, call `hook()` to hook into ikiwiki's
processing. The function uses named parameters, and use varies depending on
-the type of hook being registered -- see below. Note that a plugin can call
-the function more than once to register multiple hooks. All calls to
-`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 tells what function to call for the hook.
+the type of hook being registered -- see below. A plugin can call
+the function more than once to register multiple hooks.
+
+All calls to `hook()` should be passed a "type" parameter, which gives the
+type of hook, a "id" parameter, which should be a unique string for this
+plugin, and a "call" parameter, which tells what function to call for the
+hook.
An optional "last" parameter, if set to a true value, makes the hook run
-after all other hooks of its type. Useful if the hook depends on some other
-hook being run first.
+after all other hooks of its type, and an optional "first" parameter makes
+it run first. Useful if the hook depends on some other hook being run first.
## Types of hooks
array of pages that will be rebuilt, and can modify the array, either
adding or removing files from it.
+### scan
+
+ hook(type => "scan", id => "foo", call => \&scan);
+
+This hook is called early in the process of building the wiki, and is used
+as a first pass scan of the page, to collect metadata about the page. It's
+mostly used to scan the page for [[WikiLinks|ikiwiki/WikiLink]], and add them to `%links`.
+Present in IkiWiki 2.40 and later.
+
+The function is passed named parameters "page" and "content". Its return
+value is ignored.
+
### filter
hook(type => "filter", id => "foo", call => \&filter);
### preprocess
-Adding a [[ikiwiki/PreProcessorDirective]] is probably the most common use
+Adding a preprocessor [[ikiwiki/directive]] is probably the most common use
of a plugin.
hook(type => "preprocess", id => "foo", call => \&preprocess);
-Replace "foo" with the command name that will be used inside brackets 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 gives the name of the page the
-content is going to (different for inlined pages), and a "preview"
-parameter is set to a true value if the page is being previewed. 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
+Replace "foo" with the command name that will be used for the preprocessor
directive.
-An optional "scan" parameter, if set to a true value, makes the hook be
-called during the preliminary scan that ikiwiki makes of updated pages,
-before begining to render pages. This parameter should be set to true if
-the hook modifies data in `%links`. Note that doing so will make the hook
-be run twice per page build, so avoid doing it for expensive hooks. (As an
-optimisation, if your preprocessor hook is called in a void contets, you
-can assume it's being run in scan mode.)
+Each time the directive is processed, the referenced function (`preprocess`
+in the example above) is called. Whatever the function returns goes onto
+the page in place of the directive. Or, if the function aborts using
+`error()`, the directive will be replaced with the error message.
+
+The function is passed named parameters. First come the parameters set
+in the preprocessor directive. These are passed in the same order as
+they're in the directive, and if the preprocessor directive contains a bare
+parameter (example: `\[[!foo param]]`), that parameter will be passed with
+an empty value.
+
+After the parameters from the preprocessor directive some additional ones
+are passed: A "page" parameter gives the name of the page that embedded the
+preprocessor directive, while a "destpage" parameter gives the name of the
+page the content is going to (different for inlined pages), and a "preview"
+parameter is set to a true value if the page is being previewed.
+
+If `hook` is passed an optional "scan" parameter, set to a true value, this
+makes the hook be called during the preliminary scan that ikiwiki makes of
+updated pages, before begining to render pages. This should be done if the
+hook modifies data in `%links`. Note that doing so will make the hook be
+run twice per page build, so avoid doing it for expensive hooks. (As an
+optimisation, if your preprocessor hook is called in a void context, you
+can assume it's being run in scan mode, and avoid doing expensive things at
+that point.)
Note that if the [[htmlscrubber]] is enabled, html in
-[[ikiwiki/PreProcessorDirective]] output is sanitised, which may limit what
+preprocessor [[ikiwiki/directive]] 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 linkified and passed through markdown (or whatever engine is used to
htmlize the page) along with the rest of the page.
+### linkify
+
+ hook(type => "linkify", id => "foo", call => \&linkify);
+
+This hook is called to convert [[WikiLinks|ikiwiki/WikiLink]] on the page into html
+links. The function is passed named parameters "page", "destpage", and
+"content". It should return the linkified content. Present in IkiWiki 2.40
+and later.
+
+Plugins that implement linkify must also implement a scan hook, that scans
+for the links on the page and adds them to `%links`.
+
### htmlize
hook(type => "htmlize", id => "ext", call => \&htmlize);
-Runs on the raw source of a page and turns it into html. The id parameter
+Runs on the 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.
The function is passed named parameters: "page" and "content" and should
return the htmlized content.
+If `hook` is passed an optional "keepextension" parameter, set to a true
+value, then the extension will not be stripped from the source filename when
+generating the page.
+
+If `hook` is passed an optional "noextension" parameter, set to a true
+value, then the id parameter specifies not a filename extension, but
+a whole filename that can be htmlized. This is useful for files
+like `Makefile` that have no extension.
+
### pagetemplate
hook(type => "pagetemplate", id => "foo", call => \&pagetemplate);
a cgi. This hook allows modifying the variables available on those
templates. The function is passed named parameters. The "page" and
"destpage" parameters are the same as for a preprocess hook. The "template"
-parameter is a [[cpan HTML::Template]] object that is the template that
+parameter is a [[!cpan HTML::Template]] object that is the template that
will be used to generate the page. The function can manipulate that
template object.
Use this to implement html sanitization or anything else that needs to
modify the body of a page after it has been fully converted to html.
-The function is passed named parameters: "page" and "content", and
-should return the sanitized content.
+The function is passed named parameters: "page", "destpage", and "content",
+and should return the sanitized content.
+
+### postscan
+
+ hook(type => "postscan", id => "foo", call => \&postscan);
+
+This hook is called once the full page body is available (but before the
+format hook). The most common use is to update search indexes. Added in
+ikiwiki 2.54.
+
+The function is passed named parameters "page" and "content". Its return
+value is ignored.
### format
The difference between format and sanitize is that sanitize only acts on
the page body, while format can modify the entire html page including the
-header and footer inserted by ikiwiki, the html document type, etc.
+header and footer inserted by ikiwiki, the html document type, etc. (It
+should not rely on always being passed the entire page, as it won't be
+when the page is being previewed.)
The function is passed named parameters: "page" and "content", and
should return the formatted content.
hook(type => "auth", id => "foo", call => \&auth);
-This hook can be used to implement a different authentication method than
-the standard web form. When a user needs to be authenticated, each registered
-auth hook is called in turn, and passed a CGI object and a session object.
+This hook can be used to implement an authentication method. When a user
+needs to be authenticated, each registered auth hook is called in turn, and
+passed a CGI object and a session object.
If the hook is able to authenticate the user, it should set the session
object's "name" parameter to the authenticated user's name. Note that
### canedit
- hook(type => "canedit", id => "foo", call => \&pagelocked);
+ hook(type => "canedit", id => "foo", call => \&canedit);
This hook can be used to implement arbitrary access methods to control when
a page can be edited using the web interface (commits from revision control
since it's sometimes used to test to see which pages in a set of pages a
user can edit.
+### canremove
+
+ hook(type => "canremove", id => "foo", call => \&canremove);
+
+This hook can be used to implement arbitrary access methods to control
+when a page can be removed using the web interface (commits from
+revision control bypass it). It works exactly like the `canedit` hook,
+but is passed the named parameters `cgi` (a CGI object), `session`
+(a session object) and `page` (the page subject to deletion).
+
+### canrename
+
+ hook(type => "canrename", id => "foo", call => \&canrename);
+
+This hook can be used to implement arbitrary access methods to control when
+a page can be renamed using the web interface (commits from revision control
+bypass it). It works exactly like the `canedit` hook,
+but is passed the named parameters `cgi` (a CGI object), `session` (a
+session object), `src`, `srcfile`, `dest` and `destfile`.
+
+### checkcontent
+
+ hook(type => "checkcontent", id => "foo", call => \&checkcontent);
+
+This hook is called to check the content a user has entered on a page,
+before it is saved, and decide if it should be allowed.
+
+It is passed named parameters: `content`, `page`, `cgi`, and `session`. If
+the content the user has entered is a comment, it may also be passed some
+additional parameters: `author`, `url`, and `subject`. The `subject`
+parameter may also be filled with the user's comment about the change.
+
+Note: When the user edits an existing wiki page, this hook is also
+passed a `diff` named parameter, which will include only the lines
+that they added to the page, or modified.
+
+The hook should return `undef` on success. If the content is disallowed, it
+should return a message stating what the problem is, or a function
+that can be run to perform whatever action is necessary to allow the user
+to post the content.
+
### editcontent
hook(type => "editcontent", id => "foo", call => \&editcontent);
hook(type => "formbuilder_setup", id => "foo", call => \&formbuilder_setup);
hook(type => "formbuilder", id => "foo", call => \&formbuilder);
-These hooks allow tapping into the parts of ikiwiki that use [[cpan
+These hooks allow tapping into the parts of ikiwiki that use [[!cpan
CGI::FormBuilder]] to generate web forms. These hooks are passed named
parameters: `cgi`, `session`, `form`, and `buttons`. These are, respectively,
the `CGI` object, the user's `CGI::Session`, a `CGI::FormBuilder`, and a
hook(type => "savestate", id => "foo", call => \&savestate);
-This hook is called wheneven ikiwiki normally saves its state, just before
+This hook is called whenever ikiwiki normally saves its state, just before
the state is saved. The function can save other state, modify values before
they're saved, etc.
+### renamepage
+
+ hook(type => "renamepage", id => "foo", call => \&renamepage);
+
+This hook is called by the [[plugins/rename]] plugin when it renames
+something, once per page linking to the renamed page's old location.
+The hook is passed named parameters: `page`, `oldpage`, `newpage`, and
+`content`, and should try to modify the content of `page` to reflect
+the name change. For example, by converting links to point to the
+new page.
+
+### rename
+
+ hook(type => "rename", id => "foo", call => \&rename);
+
+When a page or set of pages is renamed, the referenced function is
+called for every page, and is passed named parameters:
+
+* `torename`: a reference to a hash with keys: `src`, `srcfile`,
+ `dest`, `destfile`, `required`.
+* `cgi`: a CGI object
+* `session`: a session object.
+
+Such a hook function returns any additional rename hashes it wants to
+add. This hook is applied recursively to returned additional rename
+hashes, so that it handles the case where two plugins use the hook:
+plugin A would see when plugin B adds a new file to be renamed.
+
+### getsetup
+
+ hook(type => "getsetup", id => "foo", call => \&getsetup);
+
+This hooks is not called during normal operation, but only when setting up
+the wiki, or generating a setup file. Plugins can use this hook to add
+configuration options.
+
+The hook is passed no parameters. It returns data about the configuration
+options added by the plugin. It can also check if the plugin is usable, and
+die if not, which will cause the plugin to not be offered in the configuration
+interface.
+
+The data returned is a list of `%config` options, followed by a hash
+describing the option. There can also be an item named "plugin", which
+describes the plugin as a whole. For example:
+
+ return
+ option_foo => {
+ type => "boolean",
+ description => "enable foo?",
+ advanced => 1,
+ safe => 1,
+ rebuild => 1,
+ },
+ option_bar => {
+ type => "string",
+ example => "hello",
+ description => "option bar",
+ safe => 1,
+ rebuild => 0,
+ },
+ plugin => {
+ description => "description of this plugin",
+ safe => 1,
+ rebuild => 1,
+ },
+
+* `type` can be "boolean", "string", "integer", "pagespec",
+ or "internal" (used for values that are not user-visible). The type is
+ the type of the leaf values; the `%config` option may be an array or
+ hash of these.
+* `example` can be set to an example value.
+* `description` is a short description of the option.
+* `link` is a link to further information about the option. This can either
+ be a [[ikiwiki/WikiLink]], or an url.
+* `advanced` can be set to true if the option is more suitable for advanced
+ users.
+* `safe` should be false if the option should not be displayed in unsafe
+ configuration methods, such as the web interface. Anything that specifies
+ a command to run, a path on disk, or a regexp should be marked as unsafe.
+ If a plugin is marked as unsafe, that prevents it from being
+ enabled/disabled.
+* `rebuild` should be true if changing the option (or enabling/disabling
+ the plugin) will require a wiki rebuild, false if no rebuild is needed,
+ and undef if a rebuild could be needed in some circumstances, but is not
+ strictly required.
+
## Plugin interface
To import the ikiwiki plugin interface:
- use IkiWiki '1.00';
+ use IkiWiki '3.00';
This will import several variables and functions into your plugin's
namespace. These variables and functions are the ones most plugins need,
A plugin can access the wiki's configuration via the `%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.
+your ikiwiki setup file, which sets the hash content to configure the wiki.
### %pagestate
The `%pagestate` hash can be used by plugins to save state that they will need
next time ikiwiki is run. The hash holds per-page state, so to set a value,
-use `%pagestate{$page}{$id}{$key}=$value`, and to retrieve the value,
-use `%pagestate{$page}{$id}{$key}`.
+use `$pagestate{$page}{$id}{$key}=$value`, and to retrieve the value,
+use `$pagestate{$page}{$id}{$key}`.
-`$key` can be any string you like, but `$id` must be the same as the "id"
-parameter passed to `hook()` when registering the plugin. This is so
-ikiwiki can know when to delete pagestate for plugins that are no longer
-used.
+The `$value` can be anything that perl's Storable module is capable of
+serializing. `$key` can be any string you like, but `$id` must be the same
+as the "id" parameter passed to `hook()` when registering the plugin. This
+is so ikiwiki can know when to delete pagestate for plugins that are no
+longer used.
When pages are deleted, ikiwiki automatically deletes their pagestate too.
Note that page state does not persist across wiki rebuilds, only across
wiki updates.
+### %wikistate
+
+The `%wikistate` hash can be used by a plugin to store persistant state
+that is not bound to any one page. To set a value, use
+`$wikistate{$id}{$key}=$value, where `$value` is anything Storable can
+serialize, `$key` is any string you like, and `$id` must be the same as the
+"id" parameter passed to `hook()` when registering the plugin, so that the
+state can be dropped if the plugin is no longer used.
+
### Other variables
If your plugin needs to access data about other pages in the wiki. It can
destination file.
* `%pagesources` contains the name of the source file for each page.
-Also, the %IkiWiki::version variable contains the version number for the
+Also, the `%IkiWiki::version` variable contains the version number for the
ikiwiki program.
### Library functions
function that is called after the error message is printed, to do any final
cleanup.
-Note that while any plugin can use this for a fatal error, plugins should
-try to avoid dying on bad input, as that will halt the entire wiki build
-and make the wiki unusable. So for example, if a
-[[ikiwiki/PreProcessorDirective]] is passed bad parameters, it's better to
-return an error message, which can appear on the wiki page, rather than
-calling error().
+If called inside a preprocess hook, error() does not abort the entire
+wiki build, but instead replaces the preprocessor [[ikiwiki/directive]] with
+a version containing the error message.
+
+In other hooks, error() is a fatal error, so use with care. Try to avoid
+dying on bad input when building a page, as that will halt
+the entire wiki build and make the wiki unusable.
#### `template($;@)`
-Creates and returns a [[cpan HTML::Template]] object. The first parameter
+Creates and returns a [[!cpan HTML::Template]] object. The first parameter
is the name of the file in the template directory. The optional remaining
parameters are passed to `HTML::Template->new`.
Passed a page name, returns the base name that will be used for a the html
page created from it. (Ie, it appends ".html".)
+Use this when constructing the filename of a html file. Use `urlto` when
+generating a link to a page.
+
#### `add_depends($$)`
Makes the specified page depend on the specified [[ikiwiki/PageSpec]].
If the destination directory doesn't exist, it will first be created.
+The filename and directory are separate parameters because of
+some security checks done to avoid symlink attacks. Before writing a file,
+it checks to make sure there's not a symlink with its name, to avoid
+following the symlink. If the filename parameter includes a subdirectory
+to put the file in, it also checks if that subdirectory is a symlink, etc.
+The directory parameter, however, is not checked for symlinks. So,
+generally the directory parameter is a trusted toplevel directory like
+the srcdir or destdir, and any subdirectories of this are included in the
+filename parameter.
+
#### `will_render($$)`
Given a page name and a destination file name (not including the base
called even if the file isn't going to be written to during the preview.
Ikiwiki uses this information to automatically clean up rendered files when
-the page that rendered them goes away or is changes to no longer render
+the page that rendered them goes away or is changed to no longer render
them. will_render also does a few important security checks.
#### `pagetype($)`
Given the name of a source file, returns the name of the wiki page
that corresponds to that file.
-#### `srcfile($)`
+#### `pagetitle($)`
+
+Give the name of a wiki page, returns a version suitable to be displayed as
+the page's title. This is accomplished by de-escaping escaped characters in
+the page name. "_" is replaced with a space, and '__NN__' is replaced by
+the UTF character with code NN.
+
+#### `titlepage($)`
+
+This performs the inverse of `pagetitle`, ie, it converts a page title into
+a wiki page name.
+
+#### `linkpage($)`
+
+This converts text that could have been entered by the user as a
+[[ikiwiki/WikiLink]] into a wiki page name.
+
+#### `srcfile($;$)`
Given the name of a source file in the wiki, searches for the file in
the source directory and the underlay directories (most recently added
underlays first), and returns the full path to the first file found.
+Normally srcfile will fail with an error message if the source file cannot
+be found. The second parameter can be set to a true value to make it return
+undef instead.
+
#### `add_underlay($)`
Adds a directory to the set of underlay directories that ikiwiki will
This is the standard gettext function, although slightly optimised.
-#### `urlto($$)`
+#### `urlto($$;$)`
Construct a relative url to the first parameter from the page named by the
second. The first parameter can be either a page name, or some other
destination file, as registered by `will_render`.
-#### `targetpage($$)`
+If the third parameter is passed and is true, an absolute url will be
+constructed instead of the default relative url.
+
+#### `newpagefile($$)`
+
+This can be called when creating a new page, to determine what filename
+to save the page to. It's passed a page name, and its type, and returns
+the name of the file to create, relative to the srcdir.
+
+#### `targetpage($$;$)`
Passed a page and an extension, returns the filename that page will be
rendered to.
-## Internal use pages
+Optionally, a third parameter can be passed, to specify the preferred
+filename of the page. For example, `targetpage("foo", "rss", "feed")`
+will yield something like `foo/feed.rss`.
+
+## Miscellaneous
+
+### Internal use pages
Sometimes it's useful to put pages in the wiki without the overhead of
having them be rendered to individual html files. Such internal use pages
To make an internal use page, register a filename extension that starts
with "_". Internal use pages cannot be edited with the web interface,
-generally shouldn't contain wikilinks or preprocessor directives (use
+generally shouldn't contain [[WikiLinks|ikiwiki/WikiLink]] or preprocessor directives (use
either on them with extreme caution), and are not matched by regular
PageSpecs glob patterns, but instead only by a special `internal()`
[[ikiwiki/PageSpec]].
-## RCS plugins
+### RCS plugins
+
+ikiwiki's support for [[revision_control_systems|rcs]] is also done via
+plugins. See [[RCS_details|rcs/details]] for some more info.
+
+RCS plugins must register a number of hooks. Each hook has type 'rcs',
+and the 'id' field is set to the name of the hook. For example:
+
+ hook(type => "rcs", id => "rcs_update", call => \&rcs_update);
+ hook(type => "rcs", id => "rcs_prepedit", call => \&rcs_prepedit);
+
+#### `rcs_update()`
+
+Updates the working directory with any remote changes.
+
+#### `rcs_prepedit($)`
-ikiwiki's support for [[revision_control_systems|rcs]] also uses pluggable
-perl modules. These are in the `IkiWiki::RCS` namespace, for example
-`IkiWiki::RCS::svn`.
+Is passed a file to prepare to edit. It can generate and return an arbitrary
+token, that will be passed into `rcs_commit` when committing. For example,
+it might return the current revision ID of the file, and use that
+information later when merging changes.
-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.
+#### `rcs_commit($$$;$$)`
-See [[RCS_details|rcs/details]] for some more info.
+Passed a file, message, token (from `rcs_prepedit`), user, and ip address.
+Should try to commit the file. Returns `undef` on *success* and a version
+of the page with the rcs's conflict markers on failure.
-## PageSpec plugins
+#### `rcs_commit_staged($$$)`
+
+Passed a message, user, and ip address. Should commit all staged changes.
+Returns undef on success, and an error message on failure.
+
+Changes can be staged by calls to `rcs_add, `rcs_remove`, and
+`rcs_rename`.
+
+#### `rcs_add($)`
+
+Adds the passed file to the archive. The filename is relative to the root
+of the srcdir.
+
+Note that this should not commit the new file, it should only
+prepare for it to be committed when rcs_commit (or `rcs_commit_staged`) is
+called. Note that the file may be in a new subdir that is not yet in
+to version control; the subdir can be added if so.
+
+#### `rcs_remove($)`
+
+Remove a file. The filename is relative to the root of the srcdir.
+
+Note that this should not commit the removal, it should only prepare for it
+to be committed when `rcs_commit` (or `rcs_commit_staged`) is called. Note
+that the new file may be in a new subdir that is not yet in version
+control; the subdir can be added if so.
+
+#### `rcs_rename($$)`
+
+Rename a file. The filenames are relative to the root of the srcdir.
+
+Note that this should not commit the rename, it should only
+prepare it for when `rcs_commit` (or `rcs_commit_staged`) is called.
+The new filename may be in a new subdir, that is not yet added to
+version control. If so, the subdir will exist already, and should
+be added to revision control.
+
+#### `rcs_recentchanges($)`
+
+Examine the RCS history and generate a list of recent changes.
+The parameter is how many changes to return.
+
+The data structure returned for each change is:
+
+ {
+ rev => # the RCSs id for this commit
+ user => # name of user who made the change,
+ committype => # either "web" or the name of the rcs,
+ when => # time when the change was made,
+ message => [
+ { line => "commit message line 1" },
+ { line => "commit message line 2" },
+ # etc,
+ ],
+ pages => [
+ {
+ page => # name of page changed,
+ diffurl => # optional url to a diff of changes
+ },
+ # repeat for each page changed in this commit,
+ ],
+ }
+
+#### `rcs_diff($)`
+
+The parameter is the rev from `rcs_recentchanges`.
+Should return a list of lines of the diff (including \n) in list
+context, and the whole diff in scalar context.
+
+#### `rcs_getctime($)`
+
+This is used to get the page creation time for a file from the RCS, by looking
+it up in the history.
+
+It's ok if this is not implemented, and throws an error.
+
+#### `rcs_receive()`
+
+This is called when ikiwiki is running as a pre-receive hook (or
+equivalent), and is testing if changes pushed into the RCS from an
+untrusted user should be accepted. This is optional, and doesn't make
+sense to implement for all RCSs.
+
+It should examine the incoming changes, and do any sanity
+checks that are appropriate for the RCS to limit changes to safe file adds,
+removes, and changes. If something bad is found, it should exit
+nonzero, to abort the push. Otherwise, it should return a list of
+files that were changed, in the form:
+
+ {
+ file => # name of file that was changed
+ action => # either "add", "change", or "remove"
+ path => # temp file containing the new file content, only
+ # needed for "add"/"change", and only if the file
+ # is an attachment, not a page
+ }
+
+The list will then be checked to make sure that each change is one that
+is allowed to be made via the web interface.
+
+### PageSpec plugins
It's also possible to write plugins that add new functions to
[[PageSpecs|ikiwiki/PageSpec]]. Such a plugin should add a function to the
against. It may also be passed additional, named parameters. It should return
a IkiWiki::SuccessReason object if the match succeeds, or an
IkiWiki::FailReason object if the match fails.
+
+### Setup plugins
+
+The ikiwiki setup file is loaded using a pluggable mechanism. If you look
+at the top of a setup file, it starts with 'use IkiWiki::Setup::Standard',
+and the rest of the file is passed to that module's import method.
+
+It's possible to write other modules in the `IkiWiki::Setup::` namespace that
+can be used to configure ikiwiki in different ways. These modules should,
+when imported, populate `$IkiWiki::Setup::raw_setup` with a reference
+to a hash containing all the config items. They should also implement a
+`gendump` function.
+
+By the way, to parse a ikiwiki setup file and populate `%config`, a
+program just needs to do something like:
+`use IkiWiki::Setup; IkiWiki::Setup::load($filename)`
+
+### Function overriding
+
+Sometimes using ikiwiki's pre-defined hooks is not enough. Your plugin
+may need to replace one of ikiwiki's own functions with a modified version,
+or wrap one of the functions.
+
+For example, your plugin might want to override `displaytime`, to change
+the html markup used when displaying a date. Or it might want to override
+`IkiWiki::formattime`, to change how a date is formatted. Or perhaps you
+want to override `bestlink` and change how ikiwiki deals with [[WikiLinks|ikiwiki/WikiLink]].
+
+By venturing into this territory, your plugin is becoming tightly tied to
+ikiwiki's internals. And it might break if those internals change. But
+don't let that stop you, if you're brave.
+
+Ikiwiki provides an `inject()` function, that is a powerful way to replace
+any function with one of your own. This even allows you to inject a
+replacement for an exported function, like `bestlink`. Everything that
+imports that function will get your version instead. Pass it the name of
+the function to replace, and a new function to call.
+
+For example, here's how to replace `displaytime` with a version using HTML 5
+markup:
+
+ inject(name => 'IkiWiki::displaytime', call => sub {
+ return "<time>".formattime(@_)."</time>";
+ });
+
+Here's how to wrap `bestlink` with a version that tries to handle
+plural words:
+
+ my $origbestlink=\&bestlink;
+ inject(name => 'IkiWiki::bestlink', call => \&mybestlink);
+
+ sub deplural ($) {
+ my $word=shift;
+ $word =~ s/e?s$//; # just an example :-)
+ return $word;
+ }
+
+ sub mybestlink ($$) {
+ my $page=shift;
+ my $link=shift;
+ my $ret=$origbestlink->($page, $link);
+ if (! length $ret) {
+ $ret=$origbestlink->($page, deplural($link));
+ }
+ return $ret;
+ }
+
+### Javascript
+
+Some plugins use javascript to make ikiwiki look a bit more web-2.0-ish.
+
+All javascript code should be put in `.js` files in the `javascript`
+underlay, and plugins using those files can enable use of the underlay by
+calling `add_underlay("javascript");` in their `import` function.
+
+You'll have to arrange for `<script>` tags to be added to the pages that
+use your javascript. This can be done using a `format` hook.
+
+Ikiwiki provides some utility functions in `ikiwiki.js`, for use by other
+javascript code. These include:
+
+#### `getElementsByClass(cls, node, tag)`
+
+Returns an array of elements with the given class. The node and tag are
+optional and define what document node and element names to search.
+
+#### `hook(name, call)`
+
+The function `call` will be run as part of the hook named `name`.
+
+Note that to hook into `window.onload`, you can use the `onload' hook.
+
+#### `run_hooks(name)`
+
+Runs the hooks with the specified name.