rename plugin

[git.ikiwiki.info.git] / doc / plugins / write.mdwn

diff --git a/doc/plugins/write.mdwn b/doc/plugins/write.mdwn
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--- a/doc/plugins/write.mdwn
+++ b/doc/plugins/write.mdwn
@@ -1,10 +1,37 @@
-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.
+Ikiwiki's plugin interface allows all kinds of useful [[plugins]] to be
+written to extend ikiwiki in many ways. Despite the length of this page,
+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]].

 
 

-# Note
+[[!toc levels=2]]
+
+## Types of plugins
+
+Most ikiwiki [[plugins]] are written in perl, like ikiwiki. This gives the
+plugin full access to ikiwiki's internals, and is the most efficient.
+However, plugins can actually be written in any language that supports XML
+RPC. These are called [[external]] plugins.
+
+A plugin written in perl 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. 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`.
+
+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
+ikiwiki on its standard input, and writes to ikiwiki on its standard
+output. For more details on writing external plugins, see [[external]].
+
+Despite these two types of plugins having such different interfaces,
+they're the same as far as how they hook into ikiwiki. This document will
+explain how to write both sorts of plugins, albeit with an emphasis on perl
+plugins.
+
+## Considerations

 
 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
 
 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


@@ -15,148 +42,769 @@ 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.
 
 change until ikiwiki rebuilds the page for some other reason, like the page
 being edited.
 

-# Registering plugins
+## Registering plugins

 
 

-Plugins should, when imported, call IkiWiki::hook to hook into ikiwiki's
+Plugins should, when imported, call `hook()` to hook into ikiwiki's

 processing. The function uses named parameters, and use varies depending on
 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
+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.
 
 hook.
 

-# Writing a [[PreProcessorDirective]]
+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.

 
 

-This is probably the most common use of a plugin.
+## Types of hooks

 
 

-        IkiWiki::hook(type => "preprocess", id => "foo", call => \&preprocess);
+In roughly the order they are called.

 
 

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

 
 

-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.
+       hook(type => "getopt", id => "foo", call => \&getopt);

 
 

-## Error handing
+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 %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.

 
 

-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.
+### checkconfig

 
 

-## Html issues
+       hook(type => "checkconfig", id => "foo", call => \&checkconfig);

 
 

-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 along with the rest of the page.
+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
+`error()` if something isn't configured right.

 
 

-# Other types of hooks
+### refresh

 
 

-Beyond PreProcessorDirectives, Other types of hooks that can be used by
-plugins include:
+       hook(type => "refresh", id => "foo", call => \&refresh);

 
 

-## checkconfig
+This hook is called just before ikiwiki scans the wiki for changed files.
+It's useful for plugins that need to create or modify a source page. The
+function is passed no values.

 
 

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

 
 

-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.
+       hook(type => "needsbuild", id => "foo", call => \&needsbuild);

 
 

-## filter
+This allows a plugin to manipulate the list of files that need to be
+built when the wiki is refreshed. The function is passed a reference to an
+array of pages that will be rebuilt, and can modify the array, either
+adding or removing files from it.

 
 

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

 
 Runs on the raw source of a page, before anything else touches it, and can
 
 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.
+make arbitrary changes. The function is passed named parameters "page",
+"destpage", and "content". It should return the filtered content.
+
+### preprocess
+
+Adding a [[ikiwiki/PreProcessorDirective]] 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 for the preprocessor
+directive.
+
+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
+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|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 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.

 
 

-## pagetemplate
+### pagetemplate

 
 

-       IkiWiki::hook(type => "pagetemplate", id => "foo", call => \&pagetemplate);
+       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 the name
-of the page, and a `HTML::Template` object that is the template that will
-be used to generate the page. It can manipulate that template, the most
-common thing to do is probably to call $template->param() to add a new
-custom parameter to the template.

 
 

-## sanitize
+[[Templates|wikitemplates]] are filled out for many different things in
+ikiwiki, like generating a page, or part of a blog page, or an rss feed, or
+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
+will be used to generate the page. The function can manipulate that
+template object.

 
 

-       IkiWiki::hook(type => "sanitize", id => "foo", call => \&sanitize);
+The most common thing to do is probably to call `$template->param()` to add
+a new custom parameter to the template.
+
+### templatefile
+
+       hook(type => "templatefile", id => "foo", call => \&templatefile);
+
+This hook allows plugins to change the [[template|wikitemplates]] that is
+used for a page in the wiki. The hook is passed a "page" parameter, and
+should return the name of the template file to use, or undef if it doesn't
+want to change the default ("page.tmpl"). Template files are looked for in
+/usr/share/ikiwiki/templates by default.
+
+### sanitize
+
+       hook(type => "sanitize", id => "foo", call => \&sanitize);

 
 Use this to implement html sanitization or anything else that needs to
 
 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.
+modify the body of a page after it has been fully converted to html.
+
+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.

 
 

-## delete
+### format

 
 

-       IkiWiki::hook(type => "delete", id => "foo", call => \&dele);
+       hook(type => "format", id => "foo", call => \&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. (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.
+
+### delete
+
+       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.
 
 
 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
+### change

 
 

-       IkiWiki::hook(type => "change", id => "foo", call => \&render);
+       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.
 
 
 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
+### cgi

 
 

-       IkiWiki::hook(type => "cgi", id => "foo", call => \&cgi);
+       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
 
 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.
+parameters, and if it will handle this CGI request, output a page
+(including the http headers) and terminate the program.
+
+Note that cgi hooks are called as early as possible, before any ikiwiki
+state is loaded, and with no session information.
+
+### auth
+
+       hook(type => "auth", id => "foo", call => \&auth);
+
+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
+if the name is set to the name of a user who is not registered,
+a basic registration of the user will be automatically performed.
+
+### sessioncgi
+
+       hook(type => "sessioncgi", id => "foo", call => \&sessioncgi);

 
 

-# Wiki configuration
+Unlike the cgi hook, which is run as soon as possible, the sessioncgi hook
+is only run once a session object is available. It is passed both a CGI
+object and a session object. To check if the user is in fact signed in, you
+can check if the session object has a "name" parameter set.

 
 

-A plugin can access the wiki's configuration via the `%IkiWiki::config`
+### canedit
+
+       hook(type => "canedit", id => "foo", call => \&pagelocked);
+
+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
+bypass it). When a page is edited, each registered canedit hook is called
+in turn, and passed the page name, a CGI object, and a session object.
+
+If the hook has no opinion about whether the edit can proceed, return
+`undef`, and the next plugin will be asked to decide. If edit can proceed,
+the hook should return "". If the edit is not allowed by this hook, the
+hook should return an error message for the user to see, or a function 
+that can be run to log the user in or perform other action necessary for
+them to be able to edit the page.
+
+This hook should avoid directly redirecting the user to a signin page,
+since it's sometimes used to test to see which pages in a set of pages a
+user can edit.
+
+### editcontent
+
+       hook(type => "editcontent", id => "foo", call => \&editcontent);
+
+This hook is called when a page is saved (or previewed) using the web
+interface. It is passed named parameters: `content`, `page`, `cgi`, and
+`session`. These are, respectively, the new page content as entered by the
+user, the page name, a `CGI` object, and the user's `CGI::Session`. 
+
+It can modify the content as desired, and should return the content.
+
+### formbuilder
+
+       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
+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
+reference to an array of names of buttons to go on the form.
+
+Each time a form is set up, the `formbuilder_setup` hook is called.
+Typically the `formbuilder_setup` hook will check the form's title, and if
+it's a form that it needs to modify, will call various methods to
+add/remove/change fields, tweak the validation code for the fields, etc. It
+will not validate or display the form.
+
+Just before a form is displayed to the user, the `formbuilder` hook is
+called. It can be used to validate the form, but should not display it.
+
+### savestate
+
+       hook(type => "savestate", id => "foo", call => \&savestate);
+
+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. The hook is passed named parameters: `page`, `oldpage`,
+`newpage`, and `content`, and should try to modify the content to reflect
+the name change. For example, by converting links to point to the new page.
+
+### 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 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 '2.00';
+
+This will import several variables and functions into your plugin's
+namespace. These variables and functions are the ones most plugins need,
+and a special effort will be made to avoid changing them in incompatible
+ways, and to document any changes that have to be made in the future.
+
+Note that IkiWiki also provides other variables and functions that are not
+exported by default. No guarantee is made about these in the future, so if
+it's not exported, the wise choice is to not use it.
+
+### %config
+
+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
 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}`.

 
 

-# Wiki data
+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.
+
+### Other variables

 
 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:
 
 
 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.
-
-See [[about_RCS_backends]] for some more info.
+* `%links` lists the names of each page that a page links to, in an array
+  reference.
+* `%destsources` contains the name of the source file used to create each
+  destination file.
+* `%pagesources` contains the name of the source file for each page.
+
+Also, the %IkiWiki::version variable contains the version number for the
+ikiwiki program.
+
+### Library functions
+
+#### `hook(@)`
+
+Hook into ikiwiki's processing. See the discussion of hooks above.
+
+Note that in addition to the named parameters described above, a parameter
+named `no_override` is supported, If it's set to a true value, then this hook
+will not override any existing hook with the same id. This is useful if
+the id can be controled by the user.
+
+#### `debug($)`
+
+Logs a debugging message. These are supressed unless verbose mode is turned
+on.
+
+#### `error($;$)`
+
+Aborts with an error message. If the second parameter is passed, it is a
+function that is called after the error message is printed, to do any final
+cleanup.
+
+If called inside a preprocess hook, error() does not abort the entire
+wiki build, but instead replaces the [[ikiwiki/PreProcessorDirective]] with
+a version containing the error message.
+
+In other hooks, error() is a fatal error, so use with care. Try to avoid
+dying on bad input when building a page, as that will halt
+the entire wiki build and make the wiki unusable.
+
+#### `template($;@)`
+
+Creates and returns a [[!cpan HTML::Template]] object. The first parameter
+is the name of the file in the template directory. The optional remaining
+parameters are passed to `HTML::Template->new`.
+
+#### `htmlpage($)`
+
+Passed a page name, returns the base name that will be used for a the html
+page created from it. (Ie, it appends ".html".)
+
+#### `add_depends($$)`
+
+Makes the specified page depend on the specified [[ikiwiki/PageSpec]].
+
+#### `pagespec_match($$;@)`
+
+Passed a page name, and [[ikiwiki/PageSpec]], returns true if the
+[[ikiwiki/PageSpec]] matches the page.
+
+Additional named parameters can be passed, to further limit the match.
+The most often used is "location", which specifies the location the
+PageSpec should match against. If not passed, relative PageSpecs will match
+relative to the top of the wiki.
+
+#### `bestlink($$)`
+
+Given a page and the text of a link on the page, determine which
+existing page that link best points to. Prefers pages under a
+subdirectory with the same name as the source page, failing that
+goes down the directory tree to the base looking for matching
+pages, as described in [[ikiwiki/SubPage/LinkingRules]].
+
+#### `htmllink($$$;@)`
+
+Many plugins need to generate html links and add them to a page. This is
+done by using the `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.
+
+After the three required parameters, named parameters can be used to
+control some options. These are:
+
+* noimageinline - set to true to avoid turning links into inline html images
+* forcesubpage  - set to force a link to a subpage
+* linktext - set to force the link text to something
+* anchor - set to make the link include an anchor
+* rel - set to add a rel attribute to the link
+* class - set to add a css class to the link
+
+#### `readfile($;$)`
+
+Given a filename, reads and returns the entire file.
+
+The optional second parameter, if set to a true value, makes the file be read
+in binary mode.
+
+A failure to read the file will result in it dying with an error.
+
+#### `writefile($$$;$$)`
+
+Given a filename, a directory to put it in, and the file's content,
+writes a file. 
+
+The optional fourth parameter, if set to a true value, makes the file be
+written in binary mode.
+
+The optional fifth parameter can be used to pass a function reference that
+will be called to handle writing to the file. The function will be called
+and passed a file descriptor it should write to, and an error recovery
+function it should call if the writing fails. (You will not normally need to
+use this interface.)
+
+A failure to write the file will result in it dying with an error.
+
+If the destination directory doesn't exist, it will first be created.
+
+#### `will_render($$)`
+
+Given a page name and a destination file name (not including the base
+destination directory), register that the page will result in that file
+being rendered. 
+
+It's important to call this before writing to any file in the destination
+directory, and it's important to call it consistently every time, even if
+the file isn't really written this time -- unless you delete any old
+version of the file. In particular, in preview mode, this should still be
+called even if the file isn't going to be written to during the preview.
+
+Ikiwiki uses this information to automatically clean up rendered files when
+the page that rendered them goes away or is changed to no longer render
+them. will_render also does a few important security checks.
+
+#### `pagetype($)`
+
+Given the name of a source file, returns the type of page it is, if it's
+a type that ikiwiki knowns how to htmlize. Otherwise, returns undef.
+
+#### `pagename($)`
+
+Given the name of a source file, returns the name of the wiki page
+that corresponds to that file.
+
+#### `srcfile($;$)`
+
+Given the name of a source file in the wiki, searches for the file in
+the source directory and the underlay directories (most recently added
+underlays first), and returns the full path to the first file found.
+
+Normally srcfile will fail with an error message if the source file cannot
+be found. The second parameter can be set to a true value to make it return
+undef instead.
+
+#### `add_underlay($)`
+
+Adds a directory to the set of underlay directories that ikiwiki will
+search for files.
+
+If the directory name is not absolute, ikiwiki will assume it is in
+the parent directory of the configured underlaydir.
+
+#### `displaytime($;$)`
+
+Given a time, formats it for display.
+
+The optional second parameter is a strftime format to use to format the
+time.
+
+#### `gettext`
+
+This is the standard gettext function, although slightly optimised.
+
+#### `urlto($$;$)`
+
+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`.
+
+If the third parameter is passed and is true, an absolute url will be
+constructed instead of the default relative url.
+
+#### `targetpage($$)`
+
+Passed a page and an extension, returns the filename that page will be
+rendered to.
+
+## Miscellaneous
+
+### Internal use pages
+
+Sometimes it's useful to put pages in the wiki without the overhead of
+having them be rendered to individual html files. Such internal use pages
+are collected together to form the RecentChanges page, for example.
+
+To make an internal use page, register a filename extension that starts
+with "_". Internal use pages cannot be edited with the web interface,
+generally shouldn't contain wikilinks or preprocessor directives (use
+either on them with extreme caution), and are not matched by regular
+PageSpecs glob patterns, but instead only by a special `internal()`
+[[ikiwiki/PageSpec]].
+
+### RCS plugins
+
+ikiwiki's support for [[revision_control_systems|rcs]] is also done via
+plugins. See [[RCS_details|rcs/details]] for some more info.
+
+RCS plugins must register a number of hooks. Each hook has type 'rcs', 
+and the 'id' field is set to the name of the hook. For example:
+       
+       hook(type => "rcs", id => "rcs_update", call => \&rcs_update);
+       hook(type => "rcs", id => "rcs_prepedit", call => \&rcs_prepedit);
+
+#### `rcs_update()`
+
+Updates the working directory with any remote changes.
+
+#### `rcs_prepedit($)`
+
+Is passed a file to prepare to edit. It can generate and return an arbitrary
+token, that will be passed into `rcs_commit` when committing. For example,
+it might return the current revision ID of the file, and use that
+information later when merging changes.
+
+#### `rcs_commit($$$;$$)`
+
+Passed a file, message, token (from `rcs_prepedit`), user, and ip address.
+Should try to commit the file. Returns `undef` on *success* and a version
+of the page with the rcs's conflict markers on failure.
+
+#### `rcs_commit_staged($$$)`
+
+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($)`
+
+Adds the passed file to the archive. The filename is relative to the root
+of the srcdir.
+
+Note that this should not check the new file in, it should only
+prepare for it to be checked in when rcs_commit (or `rcs_commit_staged`) is
+called. Note that the file may be in a new subdir that is not yet in
+to version control; the subdir can be added if so.
+
+#### `rcs_remove($)`
+
+Remove a file. The filename is relative to the root of the srcdir.
+
+Note that this should not check the removal in, it should only prepare for it
+to be checked in when `rcs_commit` (or `rcs_commit_staged`) is called. Note
+that the new file may be in a new subdir that is not yet inversion
+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($)`
+
+This is used to get the page creation time for a file from the RCS, by looking
+it up in the history.
+
+It's ok if this is not implemented, and throws an error.
+
+### PageSpec plugins
+
+It's also possible to write plugins that add new functions to
+[[PageSpecs|ikiwiki/PageSpec]]. Such a plugin should add a function to the
+IkiWiki::PageSpec package, that is named `match_foo`, where "foo()" is
+how it will be accessed in a [[ikiwiki/PageSpec]]. The function will be passed
+two parameters: The name of the page being matched, and the thing to match
+against. It may also be passed additional, named parameters. It should return
+a IkiWiki::SuccessReason object if the match succeeds, or an
+IkiWiki::FailReason object if the match fails.
+
+### Setup plugins
+
+The ikiwiki setup file is loaded using a pluggable mechanism. If you look
+at the top of a setup file, it starts with 'use IkiWiki::Setup::Standard',
+and the rest of the file is passed to that module's import method.
+
+It's possible to write other modules in the `IkiWiki::Setup::` namespace that
+can be used to configure ikiwiki in different ways. These modules should,
+when imported, populate `$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, a program just needs to
+do something like:
+`use IkiWiki::Setup; my %setup=IkiWiki::Setup::load($filename)`