,

,

,
) and truncates with * a DOM-aware algorithm that preserves HTML structure. Replicates the * preview logic from RteImagePreviewRenderer for use in Content Blocks * and other custom backend preview templates. * * Usage: * * * * * @author Netresearch DTT GmbH * @license https://www.gnu.org/licenses/agpl-3.0.de.html */ final class RteImagePreviewViewHelper extends AbstractViewHelper { /** * Output is already sanitized HTML, do not escape. * * @var bool */ protected $escapeOutput = false; public function initializeArguments(): void { $this->registerArgument('html', 'string', 'RTE HTML content to preview', true); $this->registerArgument('maxLength', 'int', 'Max characters before truncation', false, 1500); $this->registerArgument('allowedTags', 'string', 'HTML tags to keep', false, '

'); } public function render(): string { return self::processHtml( $this->arguments['html'], $this->arguments['maxLength'], $this->arguments['allowedTags'], ); } /** * Process RTE HTML for backend preview: sanitize, strip tags, and truncate. * * @param mixed $html Raw HTML content * @param mixed $maxLength Maximum text length before truncation * @param mixed $allowedTags HTML tags to preserve (strip_tags format) */ public static function processHtml(mixed $html, mixed $maxLength = 1500, mixed $allowedTags = '

'): string { if (!is_string($html) || $html === '') { return ''; } $maxLength = is_int($maxLength) || is_numeric($maxLength) ? max(0, (int) $maxLength) : 1500; $allowedTags = is_string($allowedTags) ? $allowedTags : '

'; // Sanitize control characters (replaces invalid chars with U+FFFD) // - Invalid control chars: [\x00-\x08\x0B\x0C\x0E-\x1F] // - UTF-16 surrogates (UTF-8 encoded): \xED[\xA0-\xBF][\x80-\xBF] // - Non-characters U+FFFE and U+FFFF: \xEF\xBF[\xBE\xBF] $html = preg_replace( '/[\x00-\x08\x0B\x0C\x0E-\x1F]|\xED[\xA0-\xBF][\x80-\xBF]|\xEF\xBF[\xBE\xBF]/', "\xEF\xBF\xBD", $html, ) ?? ''; if ($html === '') { return ''; } // Strip to allowed tags only $html = strip_tags($html, $allowedTags); return self::truncate($html, $maxLength); } /** * Truncates the given text, but preserves HTML tags. * * @see https://stackoverflow.com/questions/16583676/shorten-text-without-splitting-words-or-breaking-html-tags */ private static function truncate(string $html, int $length): string { $internalErrors = libxml_use_internal_errors(true); $dom = new DOMDocument(); $dom->loadHTML( '' . $html, LIBXML_NONET | LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD, ); libxml_use_internal_errors($internalErrors); $totalLength = 0; $reachedLimit = false; $toRemove = []; self::walk($dom, $length, $totalLength, $reachedLimit, $toRemove); foreach ($toRemove as $child) { $child->parentNode?->removeChild($child); } $result = $dom->saveHTML(); if ($result === false) { return ''; } // Remove the XML encoding PI that was prepended for UTF-8 support return str_replace('', '', $result); } /** * Walk the DOM tree and collect the length of all text nodes. * * @param DOMNode $node * @param int $maxLength * @param int $totalLength Current accumulated text length (passed by reference) * @param bool $reachedLimit Whether the limit has been reached (passed by reference) * @param DOMNode[] $toRemove Nodes to remove after traversal (passed by reference) */ private static function walk( DOMNode $node, int $maxLength, int &$totalLength, bool &$reachedLimit, array &$toRemove, ): void { if ($reachedLimit) { $toRemove[] = $node; } else { if (($node instanceof DOMText) && ($node->nodeValue !== null)) { $totalLength += $nodeLen = mb_strlen($node->nodeValue); if ($totalLength > $maxLength) { $node->nodeValue = mb_substr( $node->nodeValue, 0, $nodeLen - ($totalLength - $maxLength), ) . '...'; $reachedLimit = true; } } if ($node->hasChildNodes()) { foreach ($node->childNodes as $child) { self::walk($child, $maxLength, $totalLength, $reachedLimit, $toRemove); } } } } }