Wysiwyg Plugin

Translator framework for Wysiwyg editors

Support for the integration of WYSIWYG (What-You-See-Is-What-You-Get) editors. On its own, the only thing this plugin gives you is a stand-alone HTML to TWiki translator script. For WYSIWYG editing in TWiki, you will also need to install a specific editor package such as TWiki:Plugins.KupuEditorContrib or TWiki:Plugins.WikiwygContrib.

This plugin provides a generic framework that supports editing of TWiki topics using any browser-based HTML editor. It works by transforming TML (TWiki Meta Language) into HTML for the editor, and then transforming HTML back into TML on save.


  • Supports the input of malformed HTML
  • Full round-trip (TML -> XHTML -> TWiki syntax)
  • Framework is editor-agnostic


What's in the package

The package includes the following pieces:
  • TML (TWiki syntax) to HTML translator
  • HTML to TML translator (with stand-alone script)
  • Generic TWiki plugin for automating the translation during editing

How it works

The plugin works by translating the topic text into HTML when someone edits a topic. The HTML is then fed to the WYSIWYG editor. On save, the edited HTML is run through the reverse translation before saving to the topic. TWiki syntax is used in preference to HTML in the stored topic wherever possible, though HTML may be used if the translator can't find a suitable TML equivalent..

The default rendering that TWiki uses to generate HTML for display in browsers is 'lossy' - information in the TWiki syntax is lost in the HTML output, and a round-trip (recovering the original TWiki syntax from the HTML) is impossible. To solve this problem the plugin instead uses its own translation of TWiki syntax to XHTML. The generated XHTML is annotated with CSS classes that support the accurate recovery of the original TWiki syntax.

Before you ask the obvious question, yes, the translator could be used to replace the TWiki rendering pipeline for generating HTML pages. In fact, the translator is taken almost directly from the implementation of the rendering pipeline for the TWiki-4 release

Translation of the HTML back to TWiki syntax uses the CPAN:HTML::Parser. This parser is used in preference to a more modern XML parser, because the WYSIWYG editor may not generate fully compliant XHTML. A strict parser would risk losing content. CPAN:HTML::Parser is better at handling malformed HTML.

There is also the advantage that the translator can be used to import HTML from other sources - for example, existing web pages. Due to the simple nature of TWiki syntax and the potential complexity of web pages, this translation is often lossy - i.e there will be HTML features that can be entered by editors that will be lost in this translation step. This is especially noticeable with HTML tables.

Using the translators from Perl scripts

Both translators can be used directly from Perl scripts, for example to build your own stand-alone translators.

A stand-alone convertor script for HTML to TWiki is included in the installation. It can be found in tools/html2tml.pl.

Integrating a HTML Editor

The plugin can be used to integrate an HTML editor in a number of different ways.
  1. The HTML for the content-to-be-edited can be generated directly in the standard edit template.
  2. The HTML for the content-to-be-edited can be generated directly in a specialised edit template.
  3. A URL can be used to fetch the content-to-be-edited from the server, for use in an IFRAME.
  4. REST handlers can be called from Javacript to convert content.

Generating content directly in the standard edit template

This is the technique used by WYSIWYG editors that can sit on top of HTML textareas, such as TinyMCE. The topic content is pre-converted to HTML before inclusion in the standard edit template. These editors use plugins that have a beforeEditHandler and an afterEditHandler. These handlers are responsible for the conversion of topic text to HTML, and post-conversion of HTML back to TML.
  1. User hits "edit".
  2. Editor-specific plugin beforeEditHandler converts topic content to HTML by calling TWiki::Plugins::WysiwygPlugin::TranslateTML2HTML.
  3. User edits and saves
  4. Editor-specific plugin afterEditHandler converts HTML back to TML by calling TWiki::Plugins::WysiwygPlugin::TranslateHTML2TML.
  • WysiwygPlugin should not be enabled in configure.
  • WYSIWYGPLUGIN_WYSIWYGSKIN should not be set.
  • Your plugin should set the textareas_hijacked context id, to signal to skins to suppress their textarea manipulation functions.
This is the recommended integration technique, if your editor can support it.

Generating content directly in a specialised edit template

This technique is useful when the editor requires the topic content in a variety of different formats at the same time. In this scenario the editor uses a custom edit template. The WYSIWYG content is made available for instantiation in that template in a number of different formats. WYSIWYGPLUGIN_WYSIWYGSKIN must be set for this to work.

The flow of control is as follows:

  1. User hits "edit" with the skin (or cover) set the same as WYSIWYGPLUGIN_WYSIWYGSKIN.
  2. The WysiwygPlugin beforeEditHandler determines if the topic is WYSIWYG editable, and vetos the edit if not by redirecting to the standard edit skin. the edit
  3. The edit template containing the JS editor is instantiated.
  4. The following variables are available for expansion in the template:
    • %WYSIWYG_TEXT% expands to the HTML of the content-to-be-edited. This is suitable for use in a textarea.
    • %JAVASCRIPT_TEXT% expands to the HTML of the content-to-be-edited in a javascript constant.
  5. User edits and saves
  6. The afterEditHandler in the WyswiygPlugin sees that wysiwyg_edit is set, which triggers the conversion back to TML.

  • The HTML form in the edit template must include an <input called wysiwyg_edit and set it to 1, to trigger the conversion from HTML back to TML.
  • WYSIWYGPLUGIN_WYSIWYGSKIN must be set to the name of the skin used for WYSIWYG editing. This is usually the name of the editor e.g. kupu.

Fetching content from a URL

In this scenario, the edit template is generated without the content-to-be-edited. The content is retrieved from the server using a URL e.g. from an IFRAME.

The flow of control is as follows:

  1. As Generating content directly in a specialised edit template
  2. As Generating content directly in a specialised edit template
  3. As Generating content directly in a specialised edit template
  4. When the document loads in the browser, the JS editor invokes a content URL (using an IFRAME or a XmlHttpRequest) to obtain the HTML document to be edited
    • The content URL is just a TWiki view URL with the wysiwyg_edit parameter set.
    • The WysiwygPlugin recognises the wysiwyg_edit parameter and uses the TML2HTML? translator to prepare the text, which is then returned as text/plain to the browser.
    • Two TWiki variables, %OWEB% and %OTOPIC%=, can be used in the content URL in the edit template to refer to the source topic for the content.
  5. After edit handling is as for Generating content directly in a specialised edit template

Other techniques

Asynchronous saves

Editors can use XmlHttpRequest to perform saves, by POSTing to the TWiki save script with the wysiwyg_edit parameter set to 1. This parameter tells the beforeSaveHandler in the WysiwygPlugin to convert the content back to TML. See TWikiScripts for details of the other parameters to the save script.

Once the save script has completed it responds with a redirect, either to an Oops page if the save failed, or to the appropriate post-save URL (usually a view). The editor must be ready to handle this redirect.

Handling Attachments

Attachment uploads can be handled by URL requests from the editor template to the TWiki upload script. The upload script normally redirects to the containing topic; a behaviour that you usually don't want in an editor! There are two ways to handle this:
  • If the uploads are done in an IFRAME or via XmlHttpRequest, then the 302 redirect at the end of the upload can simply be ignored.
  • You can pass noredirect to the upload script to suppress the redirect. In this case you will get a text/plain response of OK followed by a message if everything went well, or an error message if it did not.

REST handlers

If you are confident in Javascript you can use REST handlers with XmlHttpRequest to convert content from TML to HTML and back again.

The plugin defines the following REST handlers:


Converts the HTML text to TML. topic must be specified.


Converts the TML text to HTML. topic must be specified. The response is a text/plain page of converted content.

Plugin Installation Instructions

You do not need to install anything in the browser to use this extension. The following instructions are for the administrator who installs the extension on the server where TWiki is running.

Like many other TWiki extensions, this module is shipped with a fully automatic installer script written using the BuildContrib.

  • If you have TWiki 4.2 or later, you can install from the configure interface (Go to Plugins->Find More Extensions)
  • If you have any problems, then you can still install manually from the command-line:
    1. Download one of the .zip or .tgz archives
    2. Unpack the archive in the root directory of your TWiki installation.
    3. Run the installer script ( perl <module>_installer )
    4. Run configure and enable the module, if it is a plugin.
    5. Repeat for any missing dependencies.
  • If you are still having problems, then instead of running the installer script:
    1. Make sure that the file permissions allow the webserver user to access all files.
    2. Check in any installed files that have existing ,v files in your existing install (take care not to lock the files when you check in)
    3. Manually edit LocalSite.cfg to set any configuration variables.

Plugin Configuration Settings

Translator control

The global TWiki Variable WYSIWYG_EXCLUDE can be set to make the plugin sensitive to what is in a topic, before allowing it to be edited. You can set it up to veto an edit if the topic contains:

  • html - HTML tags (e.g. <div>, not including <br>), or
  • variables - simple variables (e.g. %VAR%) or
  • calls - TWiki variables with parameters e.g. %VARIABLE{...}%
  • pre blocks (<pre>)
  • HTML comments (<!-- ... -->)
If the plugin detects an excluded construct in the topic, it will refuse to allow the edit and will redirect to the default editor.

If you excluded calls in WYSIWYG_EXCLUDE, you can still define a subset of TWiki variables that do not block edits. this is done in the global TWiki variable WYSIWYG_EDITABLE_CALLS, which should be a list of TWiki variable names separated by vertical bars, with no spaces, e.g: * Set WYSIWYG_EDITABLE_CALLS = COMMENT|CALENDAR|INCLUDE

You should set WYSIWYG_EXCLUDE and WYSIWYG_EDITABLE_CALLS in TWikiPreferences, or in WebPreferences for each web.

You can define the global variable WYSIWYGPLUGIN_STICKYBITS to stop the plugin from ever trying to convert specific HTML tags into HTML when certain specific attributes are present on the tag. This is most useful when you have styling or alignment information in tags that must be preserved.

This variable is used to tell the translator which attributes, when present on a tag, make it "stick" i.e. block conversion. For example, setting it to table=background,lang;tr=valign will stop the translator from trying to handle any table tag that has background or lang attributes, and any tr tag that has a valign attribute.

You can use perl regular expressions to match tag and attribute names, so .*=id,on.* will ensure that any tag with an on* event handler is kept as HTML.

The default setting for this variable is:


If you edit using the plain-text editor, you can use the <sticky>..</sticky> tags to delimit HTML (or TML) that you do not want to be WYSIWYG edited.

Implementors note if you are using your own before/after edit handlers, you can call TWiki::Plugins::WysiwygPlugin::isWysiwygEditable() to check these controls.

Known issues

Incompatible with "non-standard" syntax

WysiwygPlugin is incompatible with plugins that expand non-standard syntax e.g. TWiki:Plugins.MathModePlugin (WysiwygPlugin)

Plugins that extend the syntax using TWiki variables, such as %MYVARIABLE%, should work fine.

Overlapping styles

Because TWiki uses a "best guess" approach to some formatting, it allows overlapping of tags in a way forbidden by HTML, and it is impossible to guarantee 100% that formating in the original TWiki document will still be there when the same document is loaded and then saved through the WysiwygPlugin. The most obvious case of this is to do with styles. For example, the sentence
*bold _bold-italic* italic_
is legal in TML, but in HTML is represented by
<strong>bold <em>bold-italic</em></strong> <em>italic</em>
which gets translated back to TML as
*bold _bold-italic_* _italic_
which is correct by construction, but does not render correctly in TWiki. This problem is unfortunately unavoidable due to the way TWiki syntax works.

Plugin Info

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Many thanks to the following sponsors for supporting this work:

Plugin Author(s): TWiki:Main.CrawfordCurrie http://www.c-dot.co.uk
Copyright © ILOG 2005 http://www.ilog.fr
License GPL (Gnu General Public License)
Plugin Version: 17359 (11 Aug 2008)
Change History:  
7 Aug 2008 Fixed TWikibug:Item5707 (mod_perl)
3 Aug 2008 TWiki 4.2.1 release version
25 May 2008 TWikibug:Item5457: TWikibug:Item5528: TWikibug:Item5626: using a debug simulation, I believe I have finally fixed all the complexities of using international character sets with the translator.
13 Apr 2008 TWikibug:Item4946: TWikibug:Item5530: I think I have finally fixed non-iso-8859-1 character sets. Painful. TWikibug:Item5393: removed spurious DIV generated by IE inside LI tags
31 Mar 2008 TWikibug:Item5314: TWikibug:Item5457: Fixed pickaxe mode for editing UTF-8. Characters above 255 are converted to entitites, which is a bit of a PITA, but at least it no longer corrupts topics.
28 Mar 2008 TWikibug:Item5294: fixed angle brackets in plain text and promoted sticky to be higher priority than any other tag, solving several problems in one go
24 Jan 2008 TWikibug:Item5257: remove extra spaces at end of Set lines
20 Dec 2007 TWikibug:Item5022: made TT font size same as verbatim. Had to add a new style to do it, as TMCE didn't want to play with TT or CODE tags. TWikibug:Item5138: post-conversion of 8-bit entities to characters to aid searching etc.
19 Dec 2007 TWikibug:Item4836: make the parser tolerant of META, so pasting OO docs works TWikibug:Item4969: autoclose BR and HR tags TWikibug:Item5132: fixed IMG tags TWikibug:Item5076: fixed line-sensitive TML embedded in tables
8 Nov 2007 TWikibug:Item4923: fixed blocking of table conversion due to empty attributes TWikibug:Item4936: An em embedded in an em was getting eaten TWikibug:Item4817: added typewriter text button TWikibug:Item4850: added font colour controls TWikibug:Item4645: added REST handlers for upload and fetching lists of attachments
2 Nov 2007 TWikibug:Item4903: corrected over-enthusiastive interpretation of ! as an escape
21 Oct 2007 TWikibug:Item4788: fixed unbalanced protect, which could cause loss of protected status TWikibug:Item4811: noautolink looks like an HTML construct but in fact is not; the tag is infact an "on-off" switch and does not imply any HTML structure, so cannot be converted to a DIV or a span, so has to be removed. TWikibug:Item4747: added <sticky> to try to overcome limitations in translation TWikibug:Item4831: added increased flexibility in deciding what HTML get converted to TML, and what does not. Analysed all the HTML4 tags to establish initial settings. TWikibug:Item4847: don't call non-existent function with older HTML::Parser releases TWikibug:Item4844: Saving a table from IE didn't convert it back to TML TWikibug:Item4855: table rows generated from TWiki variables were being eaten
6 Oct 2007 TWikibug:Item4700: fixed colspans TWikibug:Item4701: removed extra line between %TABLE and the table TWikibug:Item4705: fixed spacing around literal and verbatim blocks TWikibug:Item4706: merge adjacent verbatim blocks separated only by whitespace TWikibug:Item4712: fixed eating of noautolink and literal TWikibug:Item4763: list items spanning multiple lines fixed TWikibug:Item4867: released tml2html
17 Sep 2007 TWikibug:Item4647: TWikibug:Item4652: problems related to DIV fixed. TWikibug:Item4653: fixed multi-line twiki variables
16 Sep 2007 TWikibug:Item4630: polished up the way the secret string is done, to ensure synch between perl and JS. Item4622: added UTF-8 handling steps that fixup malformed UTF8 strings before presenting them to the editor (saves Moz) and stops the editor passing them back to TWiki (saves IE). Removed extra entity decoding steps that were causing problems. TWikibug:Item4629: fixed issues with verbatim, highlighted by previous mangling of this topic
13 Sep 2007 TWikibug:Item4613 cleaned up spurious message when navigating away TWikibug:Item4615 fixed incorrect rendering of emphasis next to br
12 Sep 2007 TWikibug:Item4604 Fixes to REST handler, and add ability to trigger HTML2TML? conversion from a content comment alone (required for some editors) TWikibug:Item4588 fixes to conversion of double-character emphases
7 Sep 2007 TWikibug:Item4503 excess empty lines TWikibug:Item4486 no toc headers with unofficial syntax TWikibug:Item4560: empty lines lost TWikibug:Item4566: corrupted table on save TWikibug:Item4550 section tags being eaten
4 Sep 2007 TWikibug:Item4534 TWikibug:Item4535 fixed
See Subversion logs for earlier revisions
HTML::Parser>=3.28Required. Available from CPAN.
HTML::Entities>=1.25Required. Available from CPAN.
Plugin Home: http://twiki.org/cgi-bin/view/Plugins/WysiwygPlugin
Feedback: TWiki:Plugins/WysiwygPluginDev
Appraisal: http://twiki.org/cgi-bin/view/Plugins/WysiwygPluginAppraisal

Related Topics: TWikiPreferences, TWikiPlugins

Topic revision: r8 - 10 Aug 2008 - 12:02:42 - TWikiContributor

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