WP_Widget_Text::is_legacy_instance( array $instance ): bool

90	public function is_legacy_instance( $instance ) {91 92		// Legacy mode when not in visual mode.93		if ( isset( $instance['visual'] ) ) {94			return ! $instance['visual'];95		}96 97		// Or, the widget has been added/updated in 4.8.0 then filter prop is 'content' and it is no longer legacy.98		if ( isset( $instance['filter'] ) && 'content' === $instance['filter'] ) {99			return false;100		}101 102		// If the text is empty, then nothing is preventing migration to TinyMCE.103		if ( empty( $instance['text'] ) ) {104			return false;105		}106 107		$wpautop         = ! empty( $instance['filter'] );108		$has_line_breaks = ( str_contains( trim( $instance['text'] ), "\n" ) );109 110		// If auto-paragraphs are not enabled and there are line breaks, then ensure legacy mode.111		if ( ! $wpautop && $has_line_breaks ) {112			return true;113		}114 115		// If an HTML comment is present, assume legacy mode.116		if ( str_contains( $instance['text'], '<!--' ) ) {117			return true;118		}119 120		// In the rare case that DOMDocument is not available we cannot reliably sniff content and so we assume legacy.121		if ( ! class_exists( 'DOMDocument' ) ) {122			// @codeCoverageIgnoreStart123			return true;124			// @codeCoverageIgnoreEnd125		}126 127		$doc = new DOMDocument();128 129		// Suppress warnings generated by loadHTML.130		$errors = libxml_use_internal_errors( true );131		// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged132		@$doc->loadHTML(133			sprintf(134				'<!DOCTYPE html><html><head><meta charset="%s"></head><body>%s</body></html>',135				esc_attr( get_bloginfo( 'charset' ) ),136				$instance['text']137			)138		);139		libxml_use_internal_errors( $errors );140 141		$body = $doc->getElementsByTagName( 'body' )->item( 0 );142 143		// See $allowedposttags.144		$safe_elements_attributes = array(145			'strong'  => array(),146			'em'      => array(),147			'b'       => array(),148			'i'       => array(),149			'u'       => array(),150			's'       => array(),151			'ul'      => array(),152			'ol'      => array(),153			'li'      => array(),154			'hr'      => array(),155			'abbr'    => array(),156			'acronym' => array(),157			'code'    => array(),158			'dfn'     => array(),159			'a'       => array(160				'href' => true,161			),162			'img'     => array(163				'src' => true,164				'alt' => true,165			),166		);167		$safe_empty_elements      = array( 'img', 'hr', 'iframe' );168 169		foreach ( $body->getElementsByTagName( '*' ) as $element ) {