* Link to my Ikiwiki user page

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

diff --git a/doc/plugins/write.mdwn b/doc/plugins/write.mdwn
index 90818c42e6777b58e862d366d2b6b4ae3cc86392..3dd8bdaa16b6955893f196575ee7b82e3499ac5b 100644 (file)
--- a/doc/plugins/write.mdwn
+++ b/doc/plugins/write.mdwn
@@ -1,10 +1,35 @@
-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.
-
-[[toc levels=2]]
+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]].
+
+[[!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
 
 
 ## Considerations
 


@@ -19,17 +44,14 @@ being edited.
 
 ## Registering plugins
 
 
 ## Registering plugins
 

-All 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`
-

 Plugins should, when imported, call `hook()` to hook into ikiwiki's
 processing. The function uses named parameters, and use varies depending on
 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 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.
 
 An optional "last" parameter, if set to a true value, makes the hook run
 hook.
 
 An optional "last" parameter, if set to a true value, makes the hook run


@@ -62,15 +84,35 @@ 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.
 
 function is passed no values. It's ok for the function to call
 `error()` if something isn't configured right.
 

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

 ### needsbuild
 
        hook(type => "needsbuild", id => "foo", call => \&needsbuild);
 
 ### needsbuild
 
        hook(type => "needsbuild", id => "foo", call => \&needsbuild);
 

-This allows a plugin the manipulate the list of files that need to be
+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.
 
 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.
 

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


@@ -81,8 +123,8 @@ make arbitrary changes. The function is passed named parameters "page",
 
 ### preprocess
 
 
 ### preprocess
 

-Adding a [[PreProcessorDirective]] is probably the most common use of a
-plugin.
+Adding a [[ikiwiki/PreProcessorDirective]] is probably the most common use
+of a plugin.

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


@@ -103,20 +145,34 @@ 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
 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.
+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.)

 
 Note that if the [[htmlscrubber]] is enabled, html in
 
 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
-linkified and passed through markdown (or whatever engine is used to htmlize
-the page) along with the rest of the page.
+[[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);
 
 
 ### 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.
 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.


@@ -128,12 +184,12 @@ return the htmlized content.
 
        hook(type => "pagetemplate", id => "foo", call => \&pagetemplate);
 
 
        hook(type => "pagetemplate", id => "foo", call => \&pagetemplate);
 

-[[Templates|wikitemplate]] are filled out for many different things in
+[[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"
 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
+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.
 
 will be used to generate the page. The function can manipulate that
 template object.
 


@@ -144,7 +200,7 @@ a new custom parameter to the template.
 
        hook(type => "templatefile", id => "foo", call => \&templatefile);
 
 
        hook(type => "templatefile", id => "foo", call => \&templatefile);
 

-This hook allows plugins to change the [[template|wikitemplate]] that is
+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
 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


@@ -157,8 +213,19 @@ want to change the default ("page.tmpl"). Template files are looked for in
 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.
 
 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
 
 
 ### format
 


@@ -166,7 +233,9 @@ should return the sanitized content.
 
 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
 
 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.
 
 The function is passed named parameters: "page" and "content", and 
 should return the formatted content.


@@ -192,22 +261,34 @@ source files that were rendered.
 
 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 (including the http headers) 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);
 
 
 ### auth
 
        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
 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.
 
 
 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);
+
+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.
+

 ### canedit
 
        hook(type => "canedit", id => "foo", call => \&pagelocked);
 ### canedit
 
        hook(type => "canedit", id => "foo", call => \&pagelocked);


@@ -217,20 +298,38 @@ 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.
 
 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 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.

 If the hook has no opinion about whether the edit can proceed, return
 If the hook has no opinion about whether the edit can proceed, return

-`undef`, and the next plugin will be asked to decide.
+`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);
 
 
 ### 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
+These hooks allow tapping into the parts of ikiwiki that use [[!cpan

 CGI::FormBuilder]] to generate web forms. These hooks are passed named
 CGI::FormBuilder]] to generate web forms. These hooks are passed named

-parameters: `cgi`, `session`, and `form`. These are, respectively, the
-`CGI` object, the user's `CGI::Session`, and a `CGI::FormBuilder`.
+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
 
 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


@@ -238,32 +337,38 @@ 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.
 
 add/remove/change fields, tweak the validation code for the fields, etc. It
 will not validate or display the form.
 

-Form validation and display can be overridden by the formbuilder hook.
-By default, ikiwiki will do a basic validation and display of the form,
-but if this hook is registered, it will stop that and let the hook take
-over. This hook is passed an additional named parameter: `buttons` is an
-array of the submit buttons for 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);
 
 
 ### savestate
 
        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.
 
 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.
+

 ## Plugin interface
 
 To import the ikiwiki plugin interface:
 
 ## Plugin interface
 
 To import the ikiwiki plugin interface:
 

-       use IkiWiki '1.00';
+       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.
 
 
 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 functions that are not
+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.
 
 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.
 


@@ -273,12 +378,30 @@ 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.
 
 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.
 

+### %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}{$key}`.
+
+The `$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:
 
 ### 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:
 

-* `links` lists the names of each page that a page links to, in an array
+* `%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.
   reference.
 * `%destsources` contains the name of the source file used to create each
   destination file.


@@ -309,15 +432,17 @@ 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.
 
 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 [[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 [[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($;@)`
 
 
 #### `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`.
 
 is the name of the file in the template directory. The optional remaining
 parameters are passed to `HTML::Template->new`.
 


@@ -328,12 +453,12 @@ page created from it. (Ie, it appends ".html".)
 
 #### `add_depends($$)`
 
 
 #### `add_depends($$)`
 

-Makes the specified page depend on the specified [[PageSpec]].
+Makes the specified page depend on the specified [[ikiwiki/PageSpec]].

 
 #### `pagespec_match($$;@)`
 
 
 #### `pagespec_match($$;@)`
 

-Passed a page name, and [[PageSpec]], returns true if the [[PageSpec]]
-matches the page.
+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
 
 Additional named parameters can be passed, to further limit the match.
 The most often used is "location", which specifies the location the


@@ -346,7 +471,7 @@ 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
 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 [[SubPage/LinkingRules]].
+pages, as described in [[ikiwiki/SubPage/LinkingRules]].

 
 #### `htmllink($$$;@)`
 
 
 #### `htmllink($$$;@)`
 


@@ -372,7 +497,8 @@ control some options. These are:
 * 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
 * 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.
+* rel - set to add a rel attribute to the link
+* class - set to add a css class to the link

 
 #### `readfile($;$)`
 
 
 #### `readfile($;$)`
 


@@ -405,8 +531,17 @@ If the destination directory doesn't exist, it will first be created.
 
 Given a page name and a destination file name (not including the base
 destination directory), register that the page will result in that file
 
 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.
+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($)`
 
 
 #### `pagetype($)`
 


@@ -418,16 +553,31 @@ a type that ikiwiki knowns how to htmlize. Otherwise, returns undef.
 Given the name of a source file, returns the name of the wiki page
 that corresponds to that file.
 
 Given the name of a source file, returns the name of the wiki page
 that corresponds to that file.
 

-#### `srcfile($)`
+#### `srcfile($;$)`

 
 Given the name of a source file in the wiki, searches for the file in
 
 Given the name of a source file in the wiki, searches for the file in

-the source directory and the underlay directory, and returns the full
-path to the first file found.
+the source directory and the underlay directories (most recently added
+underlays first), and returns the full path to the first file found.

 
 

-#### `displaytime($)`
+Normally srcfile will fail with an error message if the source file cannot
+be found. The second parameter can be set to a true value to make it return
+undef instead.
+
+#### `add_underlay($)`
+
+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.
 
 
 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.
 #### `gettext`
 
 This is the standard gettext function, although slightly optimised.


@@ -443,25 +593,56 @@ destination file, as registered by `will_render`.
 Passed a page and an extension, returns the filename that page will be
 rendered to.
 
 Passed a page and an extension, returns the filename that page will be
 rendered to.
 

-## RCS plugins
+## 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.

 
 

-ikiwiki's support for revision control systems also uses pluggable perl
-modules. These are in the `IkiWiki::RCS` namespace, 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]] 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.
 
 `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.
+See [[RCS_details|rcs/details]] for some more info.

 
 

-## PageSpec plugins
+### PageSpec plugins

 
 It's also possible to write plugins that add new functions to
 
 It's also possible to write plugins that add new functions to

-[[PageSpecs|PageSpec]]. Such a plugin should add a function to the
+[[PageSpecs|ikiwiki/PageSpec]]. Such a plugin should add a function to the

 IkiWiki::PageSpec package, that is named `match_foo`, where "foo()" is
 IkiWiki::PageSpec package, that is named `match_foo`, where "foo()" is

-how it will be accessed in a [[PageSpec]]. The function will be passed
+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.
 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 [[ikiwiki.setup]], 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 `$IkiWiki::Setup::raw_setup` with a reference
+to a hash containing all the config items.
+
+By the way, to parse a ikiwiki setup file, a program just needs to
+do something like:
+`use IkiWiki::Setup; my %setup=IkiWiki::Setup::load($filename)`