WP_HTML_Tag_Processor::apply_attributes_updates( int $shift_this_point ): int

Source

 *
 * This flag is set upon the first change that requires a string update.
 *
 * @var bool $modified
 */
$modified = false;

$seen      = array();
$to_remove = array();
$is_quirks = self::QUIRKS_MODE === $this->compat_mode;
if ( $is_quirks ) {
	foreach ( $this->classname_updates as $updated_name => $action ) {
		if ( self::REMOVE_CLASS === $action ) {
			$to_remove[] = strtolower( $updated_name );
		}
	}
} else {
	foreach ( $this->classname_updates as $updated_name => $action ) {
		if ( self::REMOVE_CLASS === $action ) {
			$to_remove[] = $updated_name;
		}
	}
}

// Remove unwanted classes by only copying the new ones.
$existing_class_length = strlen( $existing_class );
while ( $at < $existing_class_length ) {
	// Skip to the first non-whitespace character.
	$ws_at     = $at;
	$ws_length = strspn( $existing_class, " \t\f\r\n", $ws_at );
	$at       += $ws_length;

	// Capture the class name – it's everything until the next whitespace.
	$name_length = strcspn( $existing_class, " \t\f\r\n", $at );
	if ( 0 === $name_length ) {
		// If no more class names are found then that's the end.
		break;
	}

	$name                  = substr( $existing_class, $at, $name_length );
	$comparable_class_name = $is_quirks ? strtolower( $name ) : $name;
	$at                   += $name_length;

	// If this class is marked for removal, remove it and move on to the next one.
	if ( in_array( $comparable_class_name, $to_remove, true ) ) {
		$modified = true;
		continue;
	}

	// If a class has already been seen then skip it; it should not be added twice.
	if ( in_array( $comparable_class_name, $seen, true ) ) {
		continue;
	}

	$seen[] = $comparable_class_name;

	/*
	 * Otherwise, append it to the new "class" attribute value.
	 *
	 * There are options for handling whitespace between tags.
	 * Preserving the existing whitespace produces fewer changes
	 * to the HTML content and should clarify the before/after
	 * content when debugging the modified output.
	 *
	 * This approach contrasts normalizing the inter-class
	 * whitespace to a single space, which might appear cleaner
	 * in the output HTML but produce a noisier change.
	 */
	if ( '' !== $class ) {
		$class .= substr( $existing_class, $ws_at, $ws_length );
	}
	$class .= $name;
}

// Add new classes by appending those which haven't already been seen.
foreach ( $this->classname_updates as $name => $operation ) {
	$comparable_name = $is_quirks ? strtolower( $name ) : $name;
	if ( self::ADD_CLASS === $operation && ! in_array( $comparable_name, $seen, true ) ) {
		$modified = true;

		$class .= strlen( $class ) > 0 ? ' ' : '';
		$class .= $name;
	}
}

$this->classname_updates = array();
if ( ! $modified ) {
	return;

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