Feature: #107683 - File storage tree items modification event and label support 

Description 

Similar to the page tree functionality introduced in TYPO3 v12 and v13, the file storage tree now supports modification of tree items through the new PSR-14 event \TYPO3\CMS\Backend\Controller\Event\AfterFileStorageTreeItemsPreparedEvent .

The event is dispatched in the file storage TreeController after the storage tree items have been resolved and prepared. It provides the current PSR-7 request as well as the collection of file storage tree items.

Additionally, labels can now be added to file storage tree nodes via user TSconfig, using the combined identifier of the folder:

options.folderTree.label.1:/campaigns/ {
    label = Main Storage
    color = #ff8700
}

Labels and status information 

Similar to the page tree, labels and status information can be added to file storage tree nodes. These features significantly improve the clarity and accessibility of the file storage tree component:

• Labels: Each node can support multiple labels, sorted by priority. The highest priority label takes precedence, and only its marker is rendered. All additional labels are added to the title attribute of the node.
• Status information: Can be added through the event to provide additional visual feedback. Like labels, status information is sorted by priority. Only the highest priority status indicator is displayed, while all status labels are added to the title attribute.

Example event listener 

<?php

declare(strict_types=1);

namespace MyVendor\MyExtension\Backend\EventListener;

use TYPO3\CMS\Backend\Controller\Event\AfterFileStorageTreeItemsPreparedEvent;
use TYPO3\CMS\Backend\Dto\Tree\Label\Label;
use TYPO3\CMS\Backend\Dto\Tree\Status\StatusInformation;
use TYPO3\CMS\Core\Attribute\AsEventListener;
use TYPO3\CMS\Core\Type\ContextualFeedbackSeverity;

#[AsEventListener(
    identifier: 'my-extension/backend/modify-file-storage-tree-items',
)]
final readonly class ModifyFileStorageTreeItems
{
    public function __invoke(AfterFileStorageTreeItemsPreparedEvent $event): void
    {
        $items = $event->getItems();

        foreach ($items as &$item) {
            // Add special label for storage with uid 1
            if ($item['resource']->getCombinedIdentifier() === '1:/campaigns/') {
                $item['labels'][] = new Label(
                    label: 'A label',
                    color: '#abcdef',
                    priority: 10,
                );
                $item['statusInformation'][] = new StatusInformation(
                    label: 'An important information',
                    severity: ContextualFeedbackSeverity::INFO,
                    priority: 10,
                    icon: 'content-info',
                );
            }
        }

        $event->setItems($items);
    }
}

Impact 

It is now possible to modify the prepared file storage tree items before they are returned by the TreeController , using the new PSR-14 event AfterFileStorageTreeItemsPreparedEvent . Additionally, labels can be assigned to file storage tree nodes via user TSconfig.

Using these functionalities helps provide visual cues and improved accessibility for editors working with file storages and folders.