[Summary view] [Print] [Text view]

   1  <?php
   2  /**
   3   * HTML API: WP_HTML_Active_Formatting_Elements class
   4   *
   5   * @package WordPress
   6   * @subpackage HTML-API
   7   * @since 6.4.0
   8   */
   9  
  10  /**
  11   * Core class used by the HTML processor during HTML parsing
  12   * for managing the stack of active formatting elements.
  13   *
  14   * This class is designed for internal use by the HTML processor.
  15   *
  16   * > Initially, the list of active formatting elements is empty.
  17   * > It is used to handle mis-nested formatting element tags.
  18   * >
  19   * > The list contains elements in the formatting category, and markers.
  20   * > The markers are inserted when entering applet, object, marquee,
  21   * > template, td, th, and caption elements, and are used to prevent
  22   * > formatting from "leaking" into applet, object, marquee, template,
  23   * > td, th, and caption elements.
  24   * >
  25   * > In addition, each element in the list of active formatting elements
  26   * > is associated with the token for which it was created, so that
  27   * > further elements can be created for that token if necessary.
  28   *
  29   * @since 6.4.0
  30   *
  31   * @access private
  32   *
  33   * @see https://html.spec.whatwg.org/#list-of-active-formatting-elements
  34   * @see WP_HTML_Processor
  35   */
  36  class WP_HTML_Active_Formatting_Elements {
  37      /**
  38       * Holds the stack of active formatting element references.
  39       *
  40       * @since 6.4.0
  41       *
  42       * @var WP_HTML_Token[]
  43       */
  44      private $stack = array();
  45  
  46      /**
  47       * Reports if a specific node is in the stack of active formatting elements.
  48       *
  49       * @since 6.4.0
  50       *
  51       * @param WP_HTML_Token $token Look for this node in the stack.
  52       * @return bool Whether the referenced node is in the stack of active formatting elements.
  53       */
  54  	public function contains_node( $token ) {
  55          foreach ( $this->walk_up() as $item ) {
  56              if ( $token->bookmark_name === $item->bookmark_name ) {
  57                  return true;
  58              }
  59          }
  60  
  61          return false;
  62      }
  63  
  64      /**
  65       * Returns how many nodes are currently in the stack of active formatting elements.
  66       *
  67       * @since 6.4.0
  68       *
  69       * @return int How many node are in the stack of active formatting elements.
  70       */
  71  	public function count() {
  72          return count( $this->stack );
  73      }
  74  
  75      /**
  76       * Returns the node at the end of the stack of active formatting elements,
  77       * if one exists. If the stack is empty, returns null.
  78       *
  79       * @since 6.4.0
  80       *
  81       * @return WP_HTML_Token|null Last node in the stack of active formatting elements, if one exists, otherwise null.
  82       */
  83  	public function current_node() {
  84          $current_node = end( $this->stack );
  85  
  86          return $current_node ? $current_node : null;
  87      }
  88  
  89      /**
  90       * Pushes a node onto the stack of active formatting elements.
  91       *
  92       * @since 6.4.0
  93       *
  94       * @see https://html.spec.whatwg.org/#push-onto-the-list-of-active-formatting-elements
  95       *
  96       * @param WP_HTML_Token $token Push this node onto the stack.
  97       */
  98  	public function push( $token ) {
  99          /*
 100           * > If there are already three elements in the list of active formatting elements after the last marker,
 101           * > if any, or anywhere in the list if there are no markers, that have the same tag name, namespace, and
 102           * > attributes as element, then remove the earliest such element from the list of active formatting
 103           * > elements. For these purposes, the attributes must be compared as they were when the elements were
 104           * > created by the parser; two elements have the same attributes if all their parsed attributes can be
 105           * > paired such that the two attributes in each pair have identical names, namespaces, and values
 106           * > (the order of the attributes does not matter).
 107           *
 108           * @todo Implement the "Noah's Ark clause" to only add up to three of any given kind of formatting elements to the stack.
 109           */
 110          // > Add element to the list of active formatting elements.
 111          $this->stack[] = $token;
 112      }
 113  
 114      /**
 115       * Removes a node from the stack of active formatting elements.
 116       *
 117       * @since 6.4.0
 118       *
 119       * @param WP_HTML_Token $token Remove this node from the stack, if it's there already.
 120       * @return bool Whether the node was found and removed from the stack of active formatting elements.
 121       */
 122  	public function remove_node( $token ) {
 123          foreach ( $this->walk_up() as $position_from_end => $item ) {
 124              if ( $token->bookmark_name !== $item->bookmark_name ) {
 125                  continue;
 126              }
 127  
 128              $position_from_start = $this->count() - $position_from_end - 1;
 129              array_splice( $this->stack, $position_from_start, 1 );
 130              return true;
 131          }
 132  
 133          return false;
 134      }
 135  
 136      /**
 137       * Steps through the stack of active formatting elements, starting with the
 138       * top element (added first) and walking downwards to the one added last.
 139       *
 140       * This generator function is designed to be used inside a "foreach" loop.
 141       *
 142       * Example:
 143       *
 144       *     $html = '<em><strong><a>We are here';
 145       *     foreach ( $stack->walk_down() as $node ) {
 146       *         echo "{$node->node_name} -> ";
 147       *     }
 148       *     > EM -> STRONG -> A ->
 149       *
 150       * To start with the most-recently added element and walk towards the top,
 151       * see WP_HTML_Active_Formatting_Elements::walk_up().
 152       *
 153       * @since 6.4.0
 154       */
 155  	public function walk_down() {
 156          $count = count( $this->stack );
 157  
 158          for ( $i = 0; $i < $count; $i++ ) {
 159              yield $this->stack[ $i ];
 160          }
 161      }
 162  
 163      /**
 164       * Steps through the stack of active formatting elements, starting with the
 165       * bottom element (added last) and walking upwards to the one added first.
 166       *
 167       * This generator function is designed to be used inside a "foreach" loop.
 168       *
 169       * Example:
 170       *
 171       *     $html = '<em><strong><a>We are here';
 172       *     foreach ( $stack->walk_up() as $node ) {
 173       *         echo "{$node->node_name} -> ";
 174       *     }
 175       *     > A -> STRONG -> EM ->
 176       *
 177       * To start with the first added element and walk towards the bottom,
 178       * see WP_HTML_Active_Formatting_Elements::walk_down().
 179       *
 180       * @since 6.4.0
 181       */
 182  	public function walk_up() {
 183          for ( $i = count( $this->stack ) - 1; $i >= 0; $i-- ) {
 184              yield $this->stack[ $i ];
 185          }
 186      }
 187  }