X-Git-Url: http://git.vanrenterghem.biz/git.ikiwiki.info.git/blobdiff_plain/b66f9a1981094bc2159a228dfaefc5c2e01ee68a..724dbabc4aecf26f6c6899cea823a38a6c0f4375:/doc/plugins/write.mdwn?ds=inline
diff --git a/doc/plugins/write.mdwn b/doc/plugins/write.mdwn
index 5def4c679..fff142fa2 100644
--- a/doc/plugins/write.mdwn
+++ b/doc/plugins/write.mdwn
@@ -3,7 +3,7 @@ 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]]
+[[!toc levels=2]]
## Types of plugins
@@ -19,7 +19,7 @@ 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`.
+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
@@ -46,15 +46,17 @@ being edited.
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
@@ -99,6 +101,18 @@ 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);
@@ -109,34 +123,42 @@ make arbitrary changes. The function is passed named parameters "page",
### 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
@@ -154,23 +176,11 @@ 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`.
-### 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.
-
### 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.
@@ -178,6 +188,10 @@ 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 this extension will not be stripped from the source filename when
+generating the page.
+
### pagetemplate
hook(type => "pagetemplate", id => "foo", call => \&pagetemplate);
@@ -187,7 +201,7 @@ 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.
@@ -214,6 +228,17 @@ 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.
+
### format
hook(type => "format", id => "foo", call => \&format);
@@ -258,9 +283,9 @@ state is loaded, and with no session information.
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
@@ -296,6 +321,41 @@ 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.
+### cansave
+
+ hook(type => "cansave", id => "foo", call => \&cansave);
+
+This hook can be used to implement arbitrary access methods to control
+when a page being edited can be saved using the web interface (commits
+from revision control bypass it).
+
+When a page is about to be saved, each registered cansave hook is
+called in turn, and passed the page name, the edited content, a CGI
+object and a session object.
+
+The return value of a cansave hook is interpreted the same as for the
+canedit hook.
+
+### 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.
+
+### 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` and `canremove` hook,
+but is passed:
+* a CGI object
+* a session object
+* the named parameters `src`, `srcfile`, `dest` and `destfile`.
+
### editcontent
hook(type => "editcontent", id => "foo", call => \&editcontent);
@@ -312,7 +372,7 @@ It can modify the content as desired, and should return the content.
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
@@ -331,15 +391,97 @@ called. It can be used to validate the form, but should not display it.
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.
+### renamelink
+
+ hook(type => "renamelink", id => "foo", call => \&renamelink);
+
+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 => \&renamepages);
+
+When a page or set of pages is renamed, the referenced function is
+called, and is passed:
+
+* a reference to an array of hashes with keys: `src`, `srcfile`,
+ `dest`, `destfile`, `required`. Such a hook function can modify
+ the array.
+* a CGI object
+* a session object
+
+### 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 '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,
@@ -354,14 +496,14 @@ it's not exported, the wise choice is to not use it.
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}`.
The `$value` can be anything that perl's Storable module is capable of
serializing. `$key` can be any string you like, but `$id` must be the same
@@ -374,6 +516,15 @@ When pages are deleted, ikiwiki automatically deletes their pagestate too.
Note that page state does not persist across wiki rebuilds, only across
wiki updates.
+### %wikistate
+
+The `%wikistate` hash can be used by a plugin to store persistant state
+that is not bound to any one page. To set a value, use
+`$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
@@ -385,7 +536,7 @@ use the following hashes, using a page name as the key:
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
@@ -410,16 +561,17 @@ 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.
-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`.
@@ -428,6 +580,9 @@ 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($$)`
Makes the specified page depend on the specified [[ikiwiki/PageSpec]].
@@ -530,6 +685,23 @@ a type that ikiwiki knowns how to htmlize. Otherwise, returns undef.
Given the name of a source file, returns the name of the wiki page
that corresponds to that file.
+#### `pagetitle($)`
+
+Give the name of a wiki page, returns a version suitable to be displayed as
+the page's title. This is accomplished by de-escaping escaped characters in
+the page name. "_" is replaced with a space, and '__NN__' is replaced by
+the UTF character with code NN.
+
+#### `titlepage($)`
+
+This performs the inverse of `pagetitle`, ie, it converts a page title into
+a wiki page name.
+
+#### `linkpage($)`
+
+This converts text that could have been entered by the user as a
+[[WikiLink]] into a wiki page name.
+
#### `srcfile($;$)`
Given the name of a source file in the wiki, searches for the file in
@@ -559,18 +731,33 @@ time.
This is the standard gettext function, although slightly optimised.
-#### `urlto($$)`
+#### `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($$)`
+
+This can be called when creating a new page, to determine what filename
+to save the page to. It's passed a page name, and its type, and returns
+the name of the file to create, relative to the srcdir.
+
+#### `targetpage($$;$)`
Passed a page and an extension, returns the filename that page will be
rendered to.
-## Internal use pages
+Optionally, a third parameter can be passed, to specify the preferred
+filename of the page. For example, `targetpage("foo", "rss", "feed")`
+will yield something like `foo/feed.rss`.
+
+## Miscellaneous
+
+### Internal use pages
Sometimes it's useful to put pages in the wiki without the overhead of
having them be rendered to individual html files. Such internal use pages
@@ -583,19 +770,135 @@ either on them with extreme caution), and are not matched by regular
PageSpecs glob patterns, but instead only by a special `internal()`
[[ikiwiki/PageSpec]].
-## RCS plugins
+### RCS plugins
+
+ikiwiki's support for [[revision_control_systems|rcs]] is also done via
+plugins. See [[RCS_details|rcs/details]] for some more info.
+
+RCS plugins must register a number of hooks. Each hook has type 'rcs',
+and the 'id' field is set to the name of the hook. For example:
+
+ hook(type => "rcs", id => "rcs_update", call => \&rcs_update);
+ hook(type => "rcs", id => "rcs_prepedit", call => \&rcs_prepedit);
+
+#### `rcs_update()`
+
+Updates the working directory with any remote changes.
+
+#### `rcs_prepedit($)`
+
+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($$$)`
+
+Passed a message, user, and ip address. Should commit all staged changes.
+Returns undef on success, and an error message on failure.
+
+Changes can be staged by calls to `rcs_add, `rcs_remove`, and
+`rcs_rename`.
+
+#### `rcs_add($)`
+
+Adds the passed file to the archive. The filename is relative to the root
+of the srcdir.
+
+Note that this should not commit the new file, it should only
+prepare for it to be committed when rcs_commit (or `rcs_commit_staged`) is
+called. Note that the file may be in a new subdir that is not yet in
+to version control; the subdir can be added if so.
+
+#### `rcs_remove($)`
+
+Remove a file. The filename is relative to the root of the srcdir.
+
+Note that this should not commit the removal, it should only prepare for it
+to be committed when `rcs_commit` (or `rcs_commit_staged`) is called. Note
+that the new file may be in a new subdir that is not yet in version
+control; the subdir can be added if so.
+
+#### `rcs_rename($$)`
+
+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.
-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`.
+It's ok if this is not implemented, and throws an error.
-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_receive()`
-See [[RCS_details|rcs/details]] for some more info.
+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.
-## PageSpec plugins
+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
@@ -605,3 +908,98 @@ 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 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.
+
+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 "";
+ });
+
+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 `