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Sylius Media Alt Text: Extending

This documentation always describes the latest published version.

Services

Both interfaces are registered as public alias services and can be injected through autowiring. AltTextManagerInterface::apply() replaces all texts of an image and persists them, but does not call flush(); that is up to the caller. MediaAltTextSettingsProvider::isActive() tells you whether the "Output alt texts" switch is on.

Fallback providers

A fallback provider supplies the text when no maintained text exists. The plugin ships OwnerNameFallbackProvider: it uses the product or category name, and for avatars the name of the admin user.

Custom providers implement the interface:

use Mmd\SyliusMediaAltTextPlugin\Resolver\AltTextFallbackProviderInterface;
use Sylius\Component\Core\Model\ImageInterface;

final class MyFallbackProvider implements AltTextFallbackProviderInterface
{
    public function supports(ImageInterface $image): bool
    {
        return $image instanceof MyImage;
    }

    public function fallbackFor(ImageInterface $image, string $locale, bool $exactLocale = false): ?string
    {
        return 'My text';
    }
}

The plugin applies the tag mmd_sylius_media_alt_text.fallback_provider only to its own services. You have to tag a provider in your app yourself:

services:
    App\Alt\MyFallbackProvider:
        tags:
            - { name: mmd_sylius_media_alt_text.fallback_provider, priority: 10 }

The providers are asked by priority (higher first), and the first non-empty text wins. OwnerNameFallbackProvider has the default priority 0 and answers with the name for product and category images as soon as one exists. A custom provider for these image types is only reached if you give it a higher priority. $exactLocale = true requires a name in exactly the given language (this is how the backfill command works).

Additional image types

The mapping "image interface => alt text entity" lives in the service mmd_sylius_media_alt_text.registry (ImageAltTextTypeRegistry). It is a plain constructor argument; there is no tag for registering a type from the outside.

To cover another image type, you need:

1. your own entity that extends AbstractImageAltText and implements ImageAltTextInterface (with mapping and migration for your table)
2. an override of the service mmd_sylius_media_alt_text.registry in your app that extends both arrays with your type (interface => entity and short name => interface)

The short name is the value the backfill command accepts for --type.

Normalizer and persist processor

• The normalizer mmd_sylius_media_alt_text.normalizer.image runs with priority 65, before Sylius's image normalizer (priority 64). If you add your own normalizers for images, take this order into account.
• mmd_sylius_media_alt_text.state_processor.persist decorates API Platform's persist processor for all Doctrine operations. It acts only on images known to the registry and passes every other object through unchanged.

The plugin does not document a backward compatibility promise for interfaces and service IDs. For your own code, prefer extending the interfaces mentioned above rather than concrete classes.