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Transformation of content between the database and an RTE is needed if
the format of the content in the database is different than the format
understood by an RTE. A simple example could be that bold-tags in the
<b> should be converted to
<strong> tags in the RTE or that
references to images in
<img> tags in the database should be relative
while absolute in the RTE. In such cases a transformation is needed to
do the conversion both ways: from database (DB) to RTE and from RTE to
Generally transformations are needed for two reasons:
Data Formats: If the agreed format of the stored content in TYPO3 is different from the HTML format the RTE produces. This could be issues like XHTML, banning of certain tags or maybe a hybrid format in the database. (See section 3 in the illustration some pages ahead)
RTE specifics: If the RTE has special requirements to the content before it can be edited and if that format is different from what we want to store in the database. For instance an RTE could require a full HTML document with
<body>- obviously we don't want that in the database and likewise we will have to wrap content in such a dummy-body before it can be edited.
Many of the transformations performed back and forth in the TYPO3
backend date back to when it was a challenge to incorporate a RTE
in a browser. It was then sometimes needed to fall back an a simple
<textarea> where rich text had to be presented in a simple enough
way so that editors could work with it with no visual help.
This is what the mode
css_transform tries to achieve: maintain a
data format that is as human readable as possible while still offering
an RTE for editing if applicable.
To know the details of those transformations, please refer to the Transformation Overview. Here is a short example of a hybrid mode:
This is how the content in the database could look for a hybrid mode
1This is line number 1 with a <a href="t3://page?uid=123">link</a> inside 2This is line number 2 with a <b>bold part</b> in the text 3<p align="center">This line is centered.</p> 4This line is just plain
As you can see the TYPO3-specific tag,
<a href="t3://page?uid=123"> is used for the link to page 123.
This tag is designed to be easy for editors to insert and easy for TYPO3
to parse and understand. The t3:// scheme is later resolved to a real
link in the frontend by the LinkHandler Api. Further line 2 shows
bold text. In line 3 the situation is that the paragraph should be
centered - and there seems to be no other way than wrapping the line
<p> tag with the "align" attribute. Not so human readable but we
can do no better without an RTE. Line 4 is just plain.
Generally this content will be processed before output on a page of
course. Typically the rule will be this: "Wrap each line in a
which is not already wrapped in a
<p> tag and run all
<a>-tags with TYPO3-specific schemes through a Linkhandler to
resolve them to real uris." and thus the final result will be valid HTML.
The content in the database can easily be edited as plain text thanks
to the "hybrid-mode" used to store the content. But when the content
above from the database has to go into the RTE it will not work if
every line is not wrapped in a
This is what eventually goes into the RTE:
<p>This is line number 1 with a <a href="t3://page?uid=123">link</a> inside</p> <p>This is line number 2 with a <strong>bold part</strong> in the text</p> <p align="center">This line is centered.</p> <p>This line is just plain</p>
This process of conversion from one format to the other is what transformations do!
Transformations are mainly defined in the 'special configurations' of the $TCA "types"-configuration. See label 'special-configuration' in older versions of the TCA-Reference.
In addition transformations can be fine-tuned by Page TSconfig which means that RTE behaviour can be determined even on page branch level!
Where Transformations are Performed¶
The transformations you can do with TYPO3 are done in the class
\TYPO3\CMS\Core\Html\RteHtmlParser. There is typically a function for each
direction; From DB to RTE and from RTE to DB.
The transformations are invoked in two cases:
Before content enters the editing form This is done by calling the method
Before content is saved in the database This is done by calling the method
The rationale for transformations is discussed in Historical Perspective on RTE Transformations.