X-Git-Url: http://git.vanrenterghem.biz/git.ikiwiki.info.git/blobdiff_plain/b0952742b29373bd762cf13c258cfd4559a680ad..f8cbf79735bc4588ba6fde12f3855a51efeb7ae8:/doc/plugins/write.mdwn

diff --git a/doc/plugins/write.mdwn b/doc/plugins/write.mdwn
index a4e800c58..f808d2e1e 100644
--- a/doc/plugins/write.mdwn
+++ b/doc/plugins/write.mdwn
@@ -4,7 +4,9 @@ lowercase, such as `IkiWiki::Plugin::inline`. Ikiwiki includes a
 `IkiWiki::Plugin::skeleton` that can be fleshed out to make a useful
 plugin. `IkiWiki::Plugin::pagecount` is another simple example.
 
-## Note
+[[toc levels=2]]
+
+## 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
@@ -17,99 +19,368 @@ being edited.
 
 ## Registering plugins
 
-Plugins should, when imported, call IkiWiki::hook to hook into
-ikiwiki's processing. The function uses named parameters, and use varies depending on the type of plugin being registered. Note that a plugin can call the function more than once to register multiple hooks. All calls to IkiWiki::hook should be passed a "type" parameter, which gives the type of hook, a "id" paramter, which should be a unique string for this plugin, and a "call" parameter, which is a reference to a function to call for the hook.
+All plugins should `use IkiWiki` to import the ikiwiki plugin interface.
+
+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
+hook.
+
+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.
+
+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.
+
+## Types of hooks
+
+In roughly the order they are called.
+
+### getopt
+
+	hook(type => "getopt", id => "foo", call => \&getopt);
+
+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.
+
+### checkconfig
+
+	hook(type => "checkconfig", id => "foo", call => \&checkconfig);
 
-## Writing a [[PreProcessorDirective]]
+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.
 
-This is probably the most common use of a plugin.
+### filter
 
-        IkiWiki::hook(type => "preprocess", id => "foo", call => \&preprocess);
+	hook(type => "filter", id => "foo", call => \&filter);
 
-Replace "foo" with the command name that will be used inside brackers for the preprocessor directive.
+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.
 
-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.
+### scan
 
-### Error handing
+	hook(type => "scan", id => "foo", call => \&scan);
 
-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.
+This is identical to a preprocess hook (see below), except that it is
+called in the initial pass that scans pages for data that will be used in
+later passes. Scan hooks are the only hook that should modify 
 
-### Html issues
+### preprocess
 
-Note that if [[HTMLSanitization]] is enabled, html in 
+Adding a [[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 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). 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.
+
+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.
+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.
 
-## Other types of hooks
+### htmlize
 
-Beyond PreProcessorDirectives, Other types of hooks that can be used by plugins include:
+	hook(type => "htmlize", id => "ext", call => \&htmlize);
 
-### checkconfig
+Runs on the raw source of a page and turns it into html. The id parameter
+specifies the filename extension that a file must have to be htmlized using
+this plugin. This is how you can add support for new and exciting markup
+languages to ikiwiki.
+
+The function is passed named parameters: "page" and "content" and should
+return the htmlized content.
+
+### pagetemplate
+
+	hook(type => "pagetemplate", id => "foo", call => \&pagetemplate);
+
+[[Templates]] 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 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.
+
+The most common thing to do is probably to call $template->param() to add
+a new custom parameter to the template.
+
+### sanitize
 
-        IkiWiki::hook(type => "checkconfig", id => "foo", call => \&checkconfig);
+	hook(type => "sanitize", id => "foo", call => \&sanitize);
 
-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.
+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.
+
+### format
+
+	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.
+
+The function is passed named parameters: "page" and "content", and 
+should return the formatted content.
 
 ### delete
 
-        IkiWiki::hook(type => "delete", id => "foo", call => \&dele);
+	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.
 
-### render
+### change
 
-        IkiWiki::hook(type => "render", id => "foo", call => \&render);
+	hook(type => "change", id => "foo", call => \&render);
 
-Each time ikiwiki renders a change or addition (but not deletion) of a page to the wiki, the referenced function is called, and passed the name of the source file that was 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
 
-        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
+parameters, and if it will handle this CGI request, output a page and
+terminate the program.
+
+### 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. 
+
+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.
+
+### 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`, and `form`. These are, respectively, the
+`CGI` object, the user's `CGI::Session`, and a `CGI::FormBuilder`.
+
+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.
+
+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.
+
+### savestate
+
+	hook(type => "savestate", id => "foo", call => \&savestate);
+
+This hook is called wheneven ikiwiki normally saves its state, just before
+the state is saved. The function can save other state, modify values before
+they're saved, etc.
+
+## Plugin interface
+
+To import the ikiwiki plugin interface:
+
+	use IkiWiki '1.00';
+
+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.
 
-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.
+Note that IkiWiki also provides other variables 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.
 
-## Wiki configuration
+### %config
 
-A plugin can access the wiki's configuration via the `%IkiWiki::config` hash.
-The best way to understand the contents of the hash is to look at
+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.
 
-## Wiki data
+### 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:
 
-* `%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.
+* `%links` lists the names of each page that a page links to, in an array
+  reference.
+* `%renderedfiles` lists names of the files rendered by a page, in an array
+  reference.
+* `%pagesources` contains the name of the source file for a page.
 
-## Page templates
+Also, the %IkiWiki::version variable contains the version number for the
+ikiwiki program.
 
-Plugins are mostly limited to changing the content of pages, to change the look and feel of the wiki it's generally better to use a stylesheet and [[templates]]. However, there are some hooks in the templates that plugins can use to add stuff to the wiki's UI:
+### Library functions
 
-### Adding content to the page header
+#### `hook(@)`
 
-Html that is added to $IkiWiki::config{headercontent} will show up in the
-header of the page. One good thing to put here is a search form.
+Hook into ikiwiki's processing. See the discussion of hooks above.
+
+Note that in addition to the named parameters described above, a parameter
+named no_override is supported, If it's set to a true value, then this hook
+will not override any existing hook with the same id. This is useful if
+the id can be controled by the user.
+
+#### `debug($)`
+
+Logs a debugging message. These are supressed unless verbose mode is turned
+on.
+
+#### `error($)`
+
+Aborts with an error message.
+
+Note that while any plugin can use this for a fatal error, plugins should
+try to avoid dying on bad input, as that will halt the entire wiki build
+and make the wiki unusable. So for example, if a [[PreProcessorDirective]]
+is passed bad parameters, it's better to return an error message, which can
+appear on the wiki page, rather than calling error().
+
+#### `template($;@)`
+
+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($$)`
+
+Makes the specified page depend on the specified [[PageSpec]].
+
+#### `pagespec_match($$)`
+
+Passed a page name, and a [[PageSpec]], returns true if the [[PageSpec]]
+matches the page.
+
+#### `bestlink($$)`
+
+Given a page and the text of a link on the page, determine which
+existing page that link best points to. Prefers pages under a
+subdirectory with the same name as the source page, failing that
+goes down the directory tree to the base looking for matching
+pages, as described in [[SubPage/LinkingRules]].
+
+#### `htmllink($$$;$$$)`
+
+Many plugins need to generate html links and add them to a page. This is
+done by using the `htmllink` function. The usual way to call
+`htmlllink` is:
+
+	htmllink($page, $page, $link)
+
+Why is `$page` repeated? Because if a page is inlined inside another, and a
+link is placed on it, the right way to make that link is actually:
+
+	htmllink($page, $destpage, $link)
+
+Here `$destpage` is the inlining page. A `destpage` parameter is passed to
+some of the hook functions above; the ones that are not passed it are not used
+during inlining and don't need to worry about this issue.
+
+The remaining three optional parameters to `htmllink` are:
+
+1. noimageinline - set to true to avoid turning links into inline html images
+1. forcesubpage  - set to force a link to a subpage
+1. linktext - set to force the link text to something
+
+#### `readfile($;$)`
+
+Given a filename, reads and returns the entire file.
+
+The optional second parameter, if set to a true value, makes the file be read
+in binary mode.
+
+A failure to read the file will result in it dying with an error.
+
+#### `writefile($$$;$)`
+
+Given a filename, a directory to put it in, and the file's content,
+writes a file. 
+
+The optional second parameter, if set to a true value, makes the file be
+written in binary mode.
+
+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.
+
+#### `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($)`
+
+Given the name of a source file in the wiki, searches for the file in
+the source directory and the underlay directory, and returns the full
+path to the first file found.
+
+#### `displaytime($)`
+
+Given a time, formats it for display.
 
 ## RCS plugins
 
@@ -120,3 +391,5 @@ modules. These are in the `IkiWiki::RCS` namespace, for example
 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.