Feature: #107518 - PSR-14 event to modify form elements after being added 

Description 

A new PSR-14 event BeforeRenderableIsAddedToFormEvent has been introduced. It serves as an improved replacement for the now removed hook $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['ext/form']['initializeFormElement'] .

The new event is dispatched immediately before a renderable has been constructed and added to the corresponding form. This allows full customization of the renderable after it has been initialized.

The event provides the $renderable public property.

Example 

An example event listener could look like this:

namespace MyVendor\MyExtension\Form\EventListener;

use TYPO3\CMS\Core\Attribute\AsEventListener;
use TYPO3\CMS\Form\Event\BeforeRenderableIsAddedToFormEvent;

final class BeforeRenderableIsAddedToFormEventListener
{
    #[AsEventListener('my-extension/before-renderable-is-added-to-form-event')]
    public function __invoke(BeforeRenderableIsAddedToFormEvent $event): void
    {
        $event->renderable->setLabel('foo');
    }
}

Impact 

With the new BeforeRenderableIsAddedToFormEvent , it is now possible to modify a renderable after it has been initialized and right before being added to its form.