Foswiki::Plugins::EmptyPlugin
internal package
Foswiki::Plugins::EmptyPlugin
Foswiki plugins 'listen' to events happening in the core by registering an
interest in those events. They do this by declaring 'plugin handlers'. These
are simply functions with a particular name that, if they exist in your
plugin, will be called by the core.
This is an empty Foswiki plugin. It is a fully defined plugin, but is
disabled by default in a Foswiki installation. Use it as a template
for your own plugins.
To interact with Foswiki use ONLY the official APIs
documented in
DevelopingPlugins.
Do not reference any
packages, functions or variables elsewhere in Foswiki, as these are
subject to change without prior warning, and your plugin may suddenly stop
working.
Error messages can be output using the
Foswiki::Func
writeWarning
and
writeDebug
functions. These logs can be found in the Foswiki/working/logs
directory. You can also
print STDERR
; the output will appear in the
webserver error log. The {WarningsAreErrors} configure setting makes
Foswiki less tolerant of errors, and it is recommended to set it during
development. It can be set using configure, in the 'Miscellaneous'
section. Most handlers can also throw exceptions (e.g.
[[https://nkwiki.de/foswiki/bin/view/System/PerlDoc?module=
Foswiki::OopsException][
Foswiki::OopsException]])
For increased performance, all handler functions except
initPlugin
are
commented out below.
To enable a handler remove the leading
#
from
each line of the function. For efficiency and clarity, you should
only uncomment handlers you actually use.
NOTE: When developing a plugin it is important to remember that
Foswiki is tolerant of plugins that do not compile. In this case,
the failure will be silent but the plugin will not be available.
See
InstalledPlugins for error messages.
NOTE: Foswiki:Development.StepByStepRenderingOrder helps you decide which
rendering handler to use. When writing handlers, keep in mind that these may
be invoked on included topics. For example, if a plugin generates links to the
current topic, these need to be generated before the
afterCommonTagsHandler
is run. After that point in the rendering loop we have lost the information
that the text had been included from another topic.
NOTE: Not all handlers (and not all parameters passed to handlers) are
available with all versions of Foswiki. Where a handler has been added
the POD comment will indicate this with a "Since" line
e.g.
Since: Foswiki::Plugins::VERSION 1.1
Deprecated handlers are still available, and can continue to be used to
maintain compatibility with earlier releases, but will be removed at some
point in the future. If you do implement deprecated handlers, then you can
do no harm by simply keeping them in your code, but you are recommended to
implement the alternative as soon as possible.
See
http://foswiki.org/Download/ReleaseDates for a breakdown of release
versions.
initPlugin($topic, $web, $user) -> $boolean
-
$topic
- the name of the topic in the current CGI query
-
$web
- the name of the web in the current CGI query
-
$user
- the login name of the user
-
$installWeb
- the name of the web the plugin topic is in (usually the same as $Foswiki::cfg{SystemWebName}
)
REQUIRED
Called to initialise the plugin. If everything is OK, should return
a non-zero value. On non-fatal failure, should write a message
using
Foswiki::Func::writeWarning
and return 0. In this case
%FAILEDPLUGINS% will indicate which plugins failed.
In the case of a catastrophic failure that will prevent the whole
installation from working safely, this handler may use 'die', which
will be trapped and reported in the browser.
Note: Please align macro names with the Plugin name, e.g. if
your Plugin is called FooBarPlugin, name macros FOOBAR and/or
FOOBARSOMETHING. This avoids namespace issues.
earlyInitPlugin()
This handler is called before any other handler, and before it has been
determined if the plugin is enabled or not. Use it with great care!
If it returns a non-null error string, the plugin will be disabled.
initializeUserHandler( $loginName, $url, $pathInfo )
-
$loginName
- login name recovered from $ENV{REMOTE_USER}
-
$url
- request url
-
$pathInfo
- pathinfo from the CGI query
Allows a plugin to set the username. Normally Foswiki gets the username
from the login manager. This handler gives you a chance to override the
login manager.
Return the
login name.
This handler is called very early, immediately after
earlyInitPlugin
.
Since: Foswiki::Plugins::VERSION = '2.0'
finishPlugin()
Called when Foswiki is shutting down, this handler can be used by the plugin
to release resources - for example, shut down open database connections,
release allocated memory etc.
Note that it's important to break any cycles in memory allocated by plugins,
or that memory will be lost when Foswiki is run in a persistent context
e.g. mod_perl.
registrationHandler($web, $wikiName, $loginName, $data )
-
$web
- the name of the web in the current CGI query
-
$wikiName
- users wiki name
-
$loginName
- users login name
-
$data
- a hashref containing all the formfields POSTed to the registration script
Called when a new user registers with this Foswiki.
Note that the handler is not called when the user submits the registration
form if {Register}{NeedVerification} is enabled. It is then called when
the user submits the activation code.
Since: Foswiki::Plugins::VERSION = '2.0'
commonTagsHandler($text, $topic, $web, $included, $meta )
-
$text
- text to be processed
-
$topic
- the name of the topic in the current CGI query
-
$web
- the name of the web in the current CGI query
-
$included
- Boolean flag indicating whether the handler is invoked on an included topic
-
$meta
- meta-data object for the topic MAY BE undef
This handler is called by the code that expands %MACROS% syntax in
the topic body and in form fields. It may be called many times while
a topic is being rendered.
Only plugins that have to parse the entire topic content should implement
this function. For expanding macros with trivial syntax it is
far more
efficient to use
Foswiki::Func::registerTagHandler
(see
initPlugin
).
Internal Foswiki macros, (and any macros declared using
Foswiki::Func::registerTagHandler
) are expanded
before, and then again
after, this function is called to ensure all %MACROS% are expanded.
NOTE: when this handler is called, <verbatim> blocks have been
removed from the text (though all other blocks such as <pre> and
<noautolink> are still present).
NOTE: meta-data is
not embedded in the text passed to this
handler. Use the
$meta
object.
NOTE: Read the developer supplement at
Foswiki:Development.AddToZoneFromPluginHandlers if you are calling
addToZone()
from this handler
Since: $
Foswiki::Plugins::VERSION 2.0
beforeCommonTagsHandler($text, $topic, $web, $meta )
-
$text
- text to be processed
-
$topic
- the name of the topic in the current CGI query
-
$web
- the name of the web in the current CGI query
-
$meta
- meta-data object for the topic MAY BE undef
This handler is called before Foswiki does any expansion of its own
internal variables. It is designed for use by cache plugins. Note that
when this handler is called, <verbatim> blocks are still present
in the text.
NOTE: This handler is called once for each call to
commonTagsHandler
i.e. it may be called many times during the
rendering of a topic.
NOTE: meta-data is
not embedded in the text passed to this
handler.
NOTE: This handler is not separately called on included topics.
NOTE: Read the developer supplement at
Foswiki:Development.AddToZoneFromPluginHandlers if you are calling
addToZone()
from this handler
afterCommonTagsHandler($text, $topic, $web, $meta )
-
$text
- text to be processed
-
$topic
- the name of the topic in the current CGI query
-
$web
- the name of the web in the current CGI query
-
$meta
- meta-data object for the topic MAY BE undef
This handler is called after Foswiki has completed expansion of %MACROS%.
It is designed for use by cache plugins. Note that when this handler
is called, <verbatim> blocks are present in the text.
NOTE: This handler is called once for each call to
commonTagsHandler
i.e. it may be called many times during the
rendering of a topic.
NOTE: meta-data is
not embedded in the text passed to this
handler.
NOTE: Read the developer supplement at
Foswiki:Development.AddToZoneFromPluginHandlers if you are calling
addToZone()
from this handler
preRenderingHandler( $text, \%map )
-
$text
- text, with the head, verbatim and pre blocks replaced with placeholders
-
\%removed
- reference to a hash that maps the placeholders to the removed blocks.
Handler called immediately before Foswiki syntax structures (such as lists) are
processed, but after all variables have been expanded. Use this handler to
process special syntax only recognised by your plugin.
Placeholders are text strings constructed using the tag name and a
sequence number e.g. 'pre1', "verbatim6", "head1" etc. Placeholders are
inserted into the text inside <!--!marker!--> characters so the
text will contain <!--!pre1!--> for placeholder pre1.
Each removed block is represented by the block text and the parameters
passed to the tag (usually empty) e.g. for
<pre class='slobadob'>
XYZ
</pre>
the map will contain:
$removed->{'pre1'}{text}: XYZ
$removed->{'pre1'}{params}: class="slobadob"
Iterating over blocks for a single tag is easy. For example, to prepend a
line number to every line of every pre block you might use this code:
foreach my $placeholder ( keys %$map ) {
if( $placeholder =~ /^pre/i ) {
my $n = 1;
$map->{$placeholder}{text} =~ s/^/$n++/gem;
}
}
NOTE: This handler is called once for each rendered block of text i.e.
it may be called several times during the rendering of a topic.
NOTE: meta-data is
not embedded in the text passed to this
handler.
NOTE: Read the developer supplement at
Foswiki:Development.AddToZoneFromPluginHandlers if you are calling
addToZone()
from this handler
Since
Foswiki::Plugins::VERSION = '2.0'
postRenderingHandler( $text )
-
$text
- the text that has just been rendered. May be modified in place.
NOTE: This handler is called once for each rendered block of text i.e.
it may be called several times during the rendering of a topic.
NOTE: meta-data is
not embedded in the text passed to this
handler.
NOTE: Read the developer supplement at
Foswiki:Development.AddToZoneFromPluginHandlers if you are calling
addToZone()
from this handler
Since
Foswiki::Plugins::VERSION = '2.0'
beforeEditHandler($text, $topic, $web )
-
$text
- text that will be edited
-
$topic
- the name of the topic in the current CGI query
-
$web
- the name of the web in the current CGI query
This handler is called by the edit script just before presenting the edit text
in the edit box. It is called once when the
edit
script is run.
NOTE: meta-data may be embedded in the text passed to this handler
(using %META: tags)
Since: Foswiki::Plugins::VERSION = '2.0'
afterEditHandler($text, $topic, $web, $meta )
-
$text
- text that is being previewed
-
$topic
- the name of the topic in the current CGI query
-
$web
- the name of the web in the current CGI query
-
$meta
- meta-data for the topic.
This handler is called by the preview script just before presenting the text.
It is called once when the
preview
script is run.
NOTE: this handler is
not called unless the text is previewed.
NOTE: meta-data is
not embedded in the text passed to this
handler. Use the
$meta
object.
Since: $
Foswiki::Plugins::VERSION 2.0
beforeSaveHandler($text, $topic, $web, $meta )
-
$text
- text with embedded meta-data tags
-
$topic
- the name of the topic in the current CGI query
-
$web
- the name of the web in the current CGI query
-
$meta
- the metadata of the topic being saved, represented by a Foswiki::Meta object.
This handler is called each time a topic is saved.
NOTE: meta-data is embedded in
$text
(using %META: tags). If you modify
the
$meta
object, then it will override any changes to the meta-data
embedded in the text. Modify
either the META in the text
or the
$meta
object, never both. You are recommended to modify the
$meta
object rather
than the text, as this approach is proof against changes in the embedded
text format.
Since: Foswiki::Plugins::VERSION = 2.0
afterSaveHandler($text, $topic, $web, $error, $meta )
-
$text
- the text of the topic excluding meta-data tags (see beforeSaveHandler)
-
$topic
- the name of the topic in the current CGI query
-
$web
- the name of the web in the current CGI query
-
$error
- any error string returned by the save.
-
$meta
- the metadata of the saved topic, represented by a Foswiki::Meta object
This handler is called each time a topic is saved.
NOTE: meta-data is embedded in $text (using %META: tags)
Since: Foswiki::Plugins::VERSION 2.0
afterRenameHandler( $oldWeb, $oldTopic, $oldAttachment, $newWeb, $newTopic, $newAttachment )
-
$oldWeb
- name of old web
-
$oldTopic
- name of old topic (empty string if web rename)
-
$oldAttachment
- name of old attachment (empty string if web or topic rename)
-
$newWeb
- name of new web
-
$newTopic
- name of new topic (empty string if web rename)
-
$newAttachment
- name of new attachment (empty string if web or topic rename)
This handler is called just after the rename/move/delete action of a web, topic or attachment.
Since: Foswiki::Plugins::VERSION = '2.0'
beforeUploadHandler(\%attrHash, $meta )
-
\%attrHash
- reference to hash of attachment attribute values
-
$meta
- the Foswiki::Meta object where the upload will happen
This handler is called once when an attachment is uploaded. When this
handler is called, the attachment has
not been recorded in the database.
The attributes hash will include at least the following attributes:
-
attachment
=> the attachment name - must not be modified
-
user
- the user id - must not be modified
-
comment
- the comment - may be modified
-
stream
- an input stream that will deliver the data for the attachment. The stream can be assumed to be seekable, and the file pointer will be positioned at the start. It is not necessary to reset the file pointer to the start of the stream after you are done, nor is it necessary to close the stream.
The handler may wish to replace the original data served by the stream
with new data. In this case, the handler can set the
{stream}
to a
new stream.
For example:
sub beforeUploadHandler {
my ( $attrs, $meta ) = @_;
my $fh = $attrs->{stream};
local $/;
# read the whole stream
my $text = <$fh>;
# Modify the content
$text =~ s/investment bank/den of thieves/gi;
$fh = new File::Temp();
print $fh $text;
$attrs->{stream} = $fh;
}
Since: Foswiki::Plugins::VERSION = 2.1
afterUploadHandler(\%attrHash, $meta )
-
\%attrHash
- reference to hash of attachment attribute values
-
$meta
- a Foswiki::Meta object where the upload has happened
This handler is called just after the after the attachment
meta-data in the topic has been saved. The attributes hash
will include at least the following attributes, all of which are read-only:
-
attachment
=> the attachment name
-
comment
- the comment
-
user
- the user id
Since: Foswiki::Plugins::VERSION = 2.1
mergeHandler( $diff, $old, $new, \%info ) -> $text
Try to resolve a difference encountered during merge. The
differences
array is an array of hash references, where each hash contains the
following fields:
-
$diff
=> one of the characters '+', '-', 'c' or ' '.
- '+' -
new
contains text inserted in the new version
- '-' -
old
contains text deleted from the old version
- 'c' -
old
contains text from the old version, and new
text from the version being saved
- ' ' -
new
contains text common to both versions, or the change only involved whitespace
-
$old
=> text from version currently saved
-
$new
=> text from version being saved
-
\%info
is a reference to the form field description { name, title, type, size, value, tooltip, attributes, referenced }. It must not be wrtten to. This parameter will be undef when merging the body text of the topic.
Plugins should try to resolve differences and return the merged text.
For example, a radio button field where we have
{ diff=>'c', old=>'Leafy', new=>'Barky' }
might be resolved as
'Treelike'
. If the plugin cannot resolve a difference it should return
undef.
The merge handler will be called several times during a save; once for
each difference that needs resolution.
If any merges are left unresolved after all plugins have been given a
chance to intercede, the following algorithm is used to decide how to
merge the data:
-
new
is taken for all radio
, checkbox
and select
fields to resolve 'c' conflicts
- '+' and '-' text is always included in the the body text and text fields
-
<del>conflict</del> <ins>markers</ins>
are used to mark 'c' merges in text fields
The merge handler is called whenever a topic is saved, and a merge is
required to resolve concurrent edits on a topic.
Since: Foswiki::Plugins::VERSION = 2.0
modifyHeaderHandler( \%headers, $query )
-
\%headers
- reference to a hash of existing header values
-
$query
- reference to CGI query object
Lets the plugin modify the HTTP headers that will be emitted when a
page is written to the browser. \%headers= will contain the headers
proposed by the core, plus any modifications made by other plugins that also
implement this method that come earlier in the plugins list.
$headers->{expires} = '+1h';
Note that this is the HTTP header which is
not the same as the HTML
<HEAD> tag. The contents of the <HEAD> tag may be manipulated
using the
Foswiki::Func::addToHEAD
method.
Since: Foswiki::Plugins::VERSION 2.0
renderFormFieldForEditHandler($name, $type, $size, $value, $attributes, $possibleValues) -> $html
This handler is called before built-in types are considered. It generates
the HTML text rendering this form field, or false, if the rendering
should be done by the built-in type handlers.
-
$name
- name of form field
-
$type
- type of form field (checkbox, radio etc)
-
$size
- size of form field
-
$value
- value held in the form field
-
$attributes
- attributes of form field
-
$possibleValues
- the values defined as options for form field, if any. May be a scalar (one legal value) or a ref to an array (several legal values)
Return HTML text that renders this field. If false, form rendering
continues by considering the built-in types.
Since: Foswiki::Plugins::VERSION 2.0
Note that you can also extend the range of available
types by providing a subclass of
Foswiki::Form::FieldDefinition
to implement
the new type (see
Foswiki::Extensions.JSCalendarContrib
and
Foswiki::Extensions.RatingContrib
for examples). This is the preferred way to
extend the form field types.
renderWikiWordHandler($linkText, $hasExplicitLinkLabel, $web, $topic) -> $linkText
-
$linkText
- the text for the link i.e. for [[Link][blah blah]]
it's blah blah
, for BlahBlah
it's BlahBlah
, and for BlahBlah? it's Blah Blah
.
-
$hasExplicitLinkLabel
- true if the link is of the form [[Link][blah blah]]
(false if it's =[Blah]] or =BlahBlah
)
-
$web
, $topic
- specify the link being rendered
Called during rendering, this handler allows the plugin a chance to change
the rendering of labels used for links.
Return the new link text.
NOTE: this handler is to allow a plugin to change the link text for a possible link - it may never be used.
for example, Set ALLOWTOPICVIEW = is a possible
ACRONYM link that will not be displayed unless the topic exists
similarly, this handler is called before the Plurals code has a chance to remove the 's' from
WikiWords
Since: Foswiki::Plugins::VERSION 2.0
completePageHandler($html, $httpHeaders)
This handler is called on the ingredients of every page that is
output by the standard CGI scripts. It is designed primarily for use by
cache and security plugins.
-
$html
- the body of the page (normally <html>..$lt;/html>)
-
$httpHeaders
- the HTTP headers. Note that the headers do not contain a Content-length
. That will be computed and added immediately before the page is actually written. This is a string, which must end in \n\n.
Since: Foswiki::Plugins::VERSION 2.0
restExample($session) -> $text
This is an example of a sub to be called by the
rest
script. The parameter is:
-
$session
- The Foswiki object associated to this session.
Additional parameters can be recovered via the query object in the $session, for example:
my $query = $session->{request};
my $web = $query->{param}->{web}[0];
If your rest handler adds or replaces equivalent functionality to a standard script
provided with Foswiki, it should set the appropriate context in its switchboard entry.
In addition to the obvous contexts:
view
,
diff
, etc. the
static
context is used
to indicate that the resulting output will be read offline, such as in a PDF, and
dynamic links (edit, sorting, etc) should not be rendered.
A comprehensive list of core context identifiers used by Foswiki is found in
IfStatements. Please be careful not to
overwrite any of these identifiers!
For more information, check
CommandAndCGIScripts
For information about handling error returns from REST handlers, see
Foswiki:Support.Faq1
Since: Foswiki::Plugins::VERSION 2.0
Deprecated handlers
redirectCgiQueryHandler($query, $url )
-
$query
- the CGI query
-
$url
- the URL to redirect to
This handler can be used to replace Foswiki's internal redirect function.
If this handler is defined in more than one plugin, only the handler
in the earliest plugin in the INSTALLEDPLUGINS list will be called. All
the others will be ignored.
Deprecated in: Foswiki::Plugins::VERSION 2.1
This handler was deprecated because it cannot be guaranteed to work, and
caused a significant impediment to code improvements in the core.
beforeAttachmentSaveHandler(\%attrHash, $topic, $web )
-
\%attrHash
- reference to hash of attachment attribute values
-
$topic
- the name of the topic in the current CGI query
-
$web
- the name of the web in the current CGI query
This handler is called once when an attachment is uploaded. When this
handler is called, the attachment has
not been recorded in the database.
The attributes hash will include at least the following attributes:
-
attachment
=> the attachment name
-
comment
- the comment
-
user
- the user id
-
tmpFilename
- name of a temporary file containing the attachment data
Deprecated in: Foswiki::Plugins::VERSION 2.1
The efficiency of this handler (and therefore it's impact on performance)
is very bad. Please use
beforeUploadHandler()
instead.
afterAttachmentSaveHandler(\%attrHash, $topic, $web )
-
\%attrHash
- reference to hash of attachment attribute values
-
$topic
- the name of the topic in the current CGI query
-
$web
- the name of the web in the current CGI query
-
$error
- any error string generated during the save process (always undef in 2.1)
This handler is called just after the save action. The attributes hash
will include at least the following attributes:
-
attachment
=> the attachment name
-
comment
- the comment
-
user
- the user id
Deprecated in: Foswiki::Plugins::VERSION 2.1
This handler has a number of problems including security and performance
issues. Please use
afterUploadHandler()
instead.