Feature: #104221 - PSR-14 events for RTE <-> Persistence transformations 

Description 

When using an RTE HTML content element, two transformations take place within the TYPO3 backend:

• From database: Fetching the current content from the database (persistence) and preparing it to be displayed inside the RTE HTML component.
• To database: Retrieving the data returned by the RTE and preparing it to be persisted into the database.

This takes place in the \TYPO3\CMS\Core\Html\RteHtmlParser class, by utilizing the methods transformTextForRichTextEditor and transformTextForPersistence.

With forge#96107 and forge#92992, the former hook $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['t3lib/class.t3lib_parsehtml_proc.php']['transformation'] was removed, which took care of applying custom user-transformations. The suggested replacement for this was to use the actual RTE YAML configuration and API like allowAttributes.

Now, four PSR-14 Events are introduced to allow more granular control over data for persistence -> RTE and RTE -> persistence. This allows developers to apply more customized transformations, apart from the internal and API ones:

Modify data when saving RTE content to the database (persistence):

• \TYPO3\CMS\Core\Html\Event\BeforeTransformTextForPersistenceEvent
• \TYPO3\CMS\Core\Html\Event\AfterTransformTextForPersistenceEvent

Modify data when retrieving content from the database and pass to the RTE:

• \TYPO3\CMS\Core\Html\Event\BeforeTransformTextForRichTextEditorEvent
• \TYPO3\CMS\Core\Html\Event\AfterTransformTextForRichTextEditorEvent

All four events have the same structure (for now):

• getHtmlContent() - retrieve the current HTML content
• setHtmlContent() - used to set modifications of the HTML content
• getInitialHtmlContent() - retrieve the untampered initial HTML content
• getProcessingConfiguration() - retrieve processing configuration array

The event is meant to be used so that developers can change the HTML content either before the internal TYPO3 modifications, or after those.

The before events are executed before TYPO3 applied any kind of internal transformations, like for links. Event Listeners that want to modify output so that TYPO3 additionally operates on that, should listen to those before-Events.

When Event Listeners want to perform on the final result, the corresponding after-Events should be utilized.

Event listeners can use $value = $event->getHtmlContent() to get the current contents, apply changes to $value and then store the manipulated data via $event->setHtmlContent($value), see example:

Example 

An event listener class is constructed which will take an RTE input TYPO3 and internally store it in the database as [tag:typo3]. This could allow a content element data processor in the frontend to handle this part of the content with for example internal glossary operations.

The workflow would be:

• Editor enters "TYPO3" in the RTE instance.
• When saving, this gets stored as "[tag:typo3]".
• When the editor sees the RTE instance again, "[tag:typo3]" gets replaced to "TYPO3" again.
• So: The editor will always only see "TYPO3" and not know how it is internally handled.
• The frontend output receives "[tag:typo3]" and could do its own content element magic, other services accessing the database could also use the parseable representation.

The corresponding event listener class:

<?php
declare(strict_types=1);

namespace MyVendor\MyExtension\EventListener;

use TYPO3\CMS\Core\Attribute\AsEventListener;

class TransformListener
{
    /**
     * Transforms the current value the RTE delivered into a value that is stored (persisted) in the database.
     */
    #[AsEventListener('rtehtmlparser/modify-data-for-persistence')]
    public function modifyPersistence(AfterTransformTextForPersistenceEvent $event): void
    {
        $value = $event->getHtmlContent();
        $value = str_replace('TYPO3', '[tag:typo3]', $value);
        $event->setHtmlContent($value);
    }

    /**
     * Transforms the current persisted value into something the RTE can display
     */
    #[AsEventListener('rtehtmlparser/modify-data-for-richtexteditor')]
    public function modifyRichTextEditor(AfterTransformTextForRichTextEditorEvent $event): void
    {
        $value = $event->getHtmlContent();
        $value = str_replace('[tag:typo3]', 'TYPO3', $value);
        $event->setHtmlContent($value);
    }
}

Impact 

Using the new PSR-14 events

• \TYPO3\CMS\Core\Html\Event\BeforeTransformTextForPersistenceEvent
• \TYPO3\CMS\Core\Html\Event\AfterTransformTextForPersistenceEvent
• \TYPO3\CMS\Core\Html\Event\BeforeTransformTextForRichTextEditorEvent
• \TYPO3\CMS\Core\Html\Event\AfterTransformTextForRichTextEditorEvent

allows to apply custom transformations for database <-> RTE content transformations.