--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/html-api/class-wp-html-active-formatting-elements.php Fri Sep 05 18:40:08 2025 +0200
@@ -0,0 +1,187 @@
+<?php
+/**
+ * HTML API: WP_HTML_Active_Formatting_Elements class
+ *
+ * @package WordPress
+ * @subpackage HTML-API
+ * @since 6.4.0
+ */
+
+/**
+ * Core class used by the HTML processor during HTML parsing
+ * for managing the stack of active formatting elements.
+ *
+ * This class is designed for internal use by the HTML processor.
+ *
+ * > Initially, the list of active formatting elements is empty.
+ * > It is used to handle mis-nested formatting element tags.
+ * >
+ * > The list contains elements in the formatting category, and markers.
+ * > The markers are inserted when entering applet, object, marquee,
+ * > template, td, th, and caption elements, and are used to prevent
+ * > formatting from "leaking" into applet, object, marquee, template,
+ * > td, th, and caption elements.
+ * >
+ * > In addition, each element in the list of active formatting elements
+ * > is associated with the token for which it was created, so that
+ * > further elements can be created for that token if necessary.
+ *
+ * @since 6.4.0
+ *
+ * @access private
+ *
+ * @see https://html.spec.whatwg.org/#list-of-active-formatting-elements
+ * @see WP_HTML_Processor
+ */
+class WP_HTML_Active_Formatting_Elements {
+ /**
+ * Holds the stack of active formatting element references.
+ *
+ * @since 6.4.0
+ *
+ * @var WP_HTML_Token[]
+ */
+ private $stack = array();
+
+ /**
+ * Reports if a specific node is in the stack of active formatting elements.
+ *
+ * @since 6.4.0
+ *
+ * @param WP_HTML_Token $token Look for this node in the stack.
+ * @return bool Whether the referenced node is in the stack of active formatting elements.
+ */
+ public function contains_node( $token ) {
+ foreach ( $this->walk_up() as $item ) {
+ if ( $token->bookmark_name === $item->bookmark_name ) {
+ return true;
+ }
+ }
+
+ return false;
+ }
+
+ /**
+ * Returns how many nodes are currently in the stack of active formatting elements.
+ *
+ * @since 6.4.0
+ *
+ * @return int How many node are in the stack of active formatting elements.
+ */
+ public function count() {
+ return count( $this->stack );
+ }
+
+ /**
+ * Returns the node at the end of the stack of active formatting elements,
+ * if one exists. If the stack is empty, returns null.
+ *
+ * @since 6.4.0
+ *
+ * @return WP_HTML_Token|null Last node in the stack of active formatting elements, if one exists, otherwise null.
+ */
+ public function current_node() {
+ $current_node = end( $this->stack );
+
+ return $current_node ? $current_node : null;
+ }
+
+ /**
+ * Pushes a node onto the stack of active formatting elements.
+ *
+ * @since 6.4.0
+ *
+ * @see https://html.spec.whatwg.org/#push-onto-the-list-of-active-formatting-elements
+ *
+ * @param WP_HTML_Token $token Push this node onto the stack.
+ */
+ public function push( $token ) {
+ /*
+ * > If there are already three elements in the list of active formatting elements after the last marker,
+ * > if any, or anywhere in the list if there are no markers, that have the same tag name, namespace, and
+ * > attributes as element, then remove the earliest such element from the list of active formatting
+ * > elements. For these purposes, the attributes must be compared as they were when the elements were
+ * > created by the parser; two elements have the same attributes if all their parsed attributes can be
+ * > paired such that the two attributes in each pair have identical names, namespaces, and values
+ * > (the order of the attributes does not matter).
+ *
+ * @todo Implement the "Noah's Ark clause" to only add up to three of any given kind of formatting elements to the stack.
+ */
+ // > Add element to the list of active formatting elements.
+ $this->stack[] = $token;
+ }
+
+ /**
+ * Removes a node from the stack of active formatting elements.
+ *
+ * @since 6.4.0
+ *
+ * @param WP_HTML_Token $token Remove this node from the stack, if it's there already.
+ * @return bool Whether the node was found and removed from the stack of active formatting elements.
+ */
+ public function remove_node( $token ) {
+ foreach ( $this->walk_up() as $position_from_end => $item ) {
+ if ( $token->bookmark_name !== $item->bookmark_name ) {
+ continue;
+ }
+
+ $position_from_start = $this->count() - $position_from_end - 1;
+ array_splice( $this->stack, $position_from_start, 1 );
+ return true;
+ }
+
+ return false;
+ }
+
+ /**
+ * Steps through the stack of active formatting elements, starting with the
+ * top element (added first) and walking downwards to the one added last.
+ *
+ * This generator function is designed to be used inside a "foreach" loop.
+ *
+ * Example:
+ *
+ * $html = '<em><strong><a>We are here';
+ * foreach ( $stack->walk_down() as $node ) {
+ * echo "{$node->node_name} -> ";
+ * }
+ * > EM -> STRONG -> A ->
+ *
+ * To start with the most-recently added element and walk towards the top,
+ * see WP_HTML_Active_Formatting_Elements::walk_up().
+ *
+ * @since 6.4.0
+ */
+ public function walk_down() {
+ $count = count( $this->stack );
+
+ for ( $i = 0; $i < $count; $i++ ) {
+ yield $this->stack[ $i ];
+ }
+ }
+
+ /**
+ * Steps through the stack of active formatting elements, starting with the
+ * bottom element (added last) and walking upwards to the one added first.
+ *
+ * This generator function is designed to be used inside a "foreach" loop.
+ *
+ * Example:
+ *
+ * $html = '<em><strong><a>We are here';
+ * foreach ( $stack->walk_up() as $node ) {
+ * echo "{$node->node_name} -> ";
+ * }
+ * > A -> STRONG -> EM ->
+ *
+ * To start with the first added element and walk towards the bottom,
+ * see WP_HTML_Active_Formatting_Elements::walk_down().
+ *
+ * @since 6.4.0
+ */
+ public function walk_up() {
+ for ( $i = count( $this->stack ) - 1; $i >= 0; $i-- ) {
+ yield $this->stack[ $i ];
+ }
+ }
+}