---
title: "Feature: #108508 - PSR-14 events for Fluid components"
manual: "TYPO3 Core Changelog"
version: "main"
permalink: "https://docs.typo3.org/permalink/changelog:feature-108508-1765987847"
source: "Changelog/14.1/Feature-108508-PSR-14EventsForFluidComponents.rst"
typo3-version: "14.1"
typo3-major: 14
type: "feature"
issue: 108508
forge: "https://forge.typo3.org/issues/108508"
tags: ["Fluid", "ext:fluid"]
rendered: "2026-09-25T23:17:45+00:00"
---

# Feature: #108508 - PSR-14 events for Fluid components {#feature-108508-1765987847}

See [forge#108508](https://forge.typo3.org/issues/108508)

## Description {#description}

Three PSR-14 events have been added to influence the processing and rendering
of Fluid components that are registered using the new configuration file
(see [Fluid components integration](https://docs.typo3.org/permalink/changelog:feature-108508-1765987901)).

### ModifyComponentDefinitionEvent {#modifycomponentdefinitionevent}

The `\TYPO3\CMS\Fluid\Event\ModifyComponentDefinitionEvent` can be
used to modify the definition of a component before it's written to the cache.
Component definitions must not have any dependencies on runtime information, as
they might be used for static analysis or IDE auto-completion. Due
to the component definitions cache, this is already enforced, as the registered
events are only executed once and not on every request.

Example:

**EXT:my_extension/Classes/EventListener/ModifyComponentDefinitionListener.php**

```php
<?php

declare(strict_types=1);

namespace MyVendor\MyExtension\EventListener;

use TYPO3\CMS\Core\Attribute\AsEventListener;
use TYPO3\CMS\Fluid\Event\ModifyComponentDefinitionEvent;
use TYPO3Fluid\Fluid\Core\Component\ComponentDefinition;
use TYPO3Fluid\Fluid\Core\ViewHelper\ArgumentDefinition;

#[AsEventListener]
final readonly class ModifyComponentDefinitionListener
{
    public function __invoke(ModifyComponentDefinitionEvent $event): void
    {
        // Add required argument to one specific component
        if (
            $event->getNamespace() === 'MyVendor\\MyExtension\\Components' &&
            $event->getComponentDefinition()->getName() === 'myComponent'
        ) {
            $originalDefinition = $event->getComponentDefinition();
            $event->setComponentDefinition(new ComponentDefinition(
                $originalDefinition->getName(),
                [
                    ...$originalDefinition->getArgumentDefinitions(),
                    'myArgument' => new ArgumentDefinition('myArgument', 'string', '', true),
                ],
                $originalDefinition->additionalArgumentsAllowed(),
                $originalDefinition->getAvailableSlots(),
            ));
        }
    }
}
```

### ProvideStaticVariablesToComponentEvent {#providestaticvariablestocomponentevent}

The `\TYPO3\CMS\Fluid\Event\ProvideStaticVariablesToComponentEvent` can
be used to inject additional static variables into component templates. As with the
`\TYPO3\CMS\Fluid\Event\ModifyComponentDefinitionEvent`, these variables
must not have any dependencies on runtime information, as they might be used for
static analysis or IDE auto-completion. The
`\TYPO3\CMS\Fluid\Event\RenderComponentEvent` can be used to add variables
with runtime dependencies.

Valid use cases for this event might be:

-   providing static (!) design tokens (colors, icons, ...) to all components in a collection
-   generating prefix strings based on the component's name

Example:

**EXT:my_extension/Classes/EventListener/ProvideStaticVariablesToComponentListener.php**

```php
<?php

declare(strict_types=1);

namespace MyVendor\MyExtension\EventListener;

use TYPO3\CMS\Core\Attribute\AsEventListener;
use TYPO3\CMS\Fluid\Event\ProvideStaticVariablesToComponentEvent;

#[AsEventListener]
final readonly class ProvideStaticVariablesToComponentListener
{
    public function __invoke(ProvideStaticVariablesToComponentEvent $event): void
    {
        // Provide design tokens to all components in a collection
        if ($event->getComponentCollection()->getNamespace() === 'MyVendor\\MyExtension\\Components') {
            $event->setStaticVariables([
                ...$event->getStaticVariables(),
                'designTokens' => [
                    'color1' => '#abcdef',
                    'color2' => '#123456',
                ],
            ]);
        }
    }
}
```

### RenderComponentEvent {#rendercomponentevent}

The `\TYPO3\CMS\Fluid\Event\RenderComponentEvent` can be used to alter or
replace the rendering of Fluid components. There are three possible use cases:

1.  fully take over the rendering of components by filling the `$renderedContent` with
    `$event->setRenderedContent()`. The first event that does this skips all following
    event listeners.
1.  provide additional arguments (= variables in the component template) or slots to
    the component with `$event->setArguments()`/`$event->setSlots()`.
1.  execute additional code that doesn't influence the component rendering directly, e. g.
    adding certain frontend assets to the page automatically.

Example:

**EXT:my_extension/Classes/EventListener/RenderComponentListener.php**

```php
<?php

declare(strict_types=1);

namespace MyVendor\MyExtension\EventListener;

use TYPO3\CMS\Core\Attribute\AsEventListener;
use TYPO3\CMS\Core\Page\AssetCollector;
use TYPO3\CMS\Fluid\Event\RenderComponentEvent;

#[AsEventListener]
final readonly class RenderComponentListener
{
    public function __construct(private AssetCollector $assetCollector) {}

    public function __invoke(RenderComponentEvent $event): void
    {
        // Add bundled components CSS if a component is used on the page
        if ($event->getComponentCollection()->getNamespace() === 'MyVendor\\MyExtension\\Components') {
            $this->assetCollector->addStyleSheet(
                'componentsBundle',
                'EXT:my_extension/Resources/Public/ComponentsBundle.css'
            );
        }
    }
}
```

## Impact {#impact}

Three new PSR-14 events can be used to influence the processing and rendering
of Fluid components.