PDF.js in the Joomla administrator

Explicit asset registry registration

Automatic registration applies only to the site application. Add the registry yourself in an administrator component HTML view. This also works before onAfterRoute. The plugin must be installed: its namespace provides ModuleAssetItem, which resolves .mjs paths.

PHP example

<?php
use Joomla\CMS\Factory;
$document = Factory::getApplication()->getDocument();
$wa = $document->getWebAssetManager();
$wa->getRegistry()->addRegistryFile('media/plg_system_wtpdfjs/joomla.asset.json');
$wa->useScript('wt-pdf-js-legacy');