Chris@0: <?php
Chris@0: 
Chris@0: namespace Drupal\Core\Render;
Chris@0: 
Chris@0: /**
Chris@0:  * The render context: a stack containing bubbleable rendering metadata.
Chris@0:  *
Chris@0:  * A stack of \Drupal\Core\Render\BubbleableMetadata objects.
Chris@0:  *
Chris@0:  * @see \Drupal\Core\Render\RendererInterface
Chris@0:  * @see \Drupal\Core\Render\Renderer
Chris@0:  * @see \Drupal\Core\Render\BubbleableMetadata
Chris@0:  */
Chris@0: class RenderContext extends \SplStack {
Chris@0: 
Chris@0:   /**
Chris@0:    * Updates the current frame of the stack.
Chris@0:    *
Chris@0:    * @param array &$element
Chris@0:    *   The element of the render array that has just been rendered. The stack
Chris@0:    *   frame for this element will be updated with the bubbleable rendering
Chris@0:    *   metadata of this element.
Chris@0:    */
Chris@0:   public function update(&$element) {
Chris@0:     // The latest frame represents the bubbleable metadata for the subtree.
Chris@0:     $frame = $this->pop();
Chris@0:     // Update the frame, but also update the current element, to ensure it
Chris@0:     // contains up-to-date information in case it gets render cached.
Chris@0:     $updated_frame = BubbleableMetadata::createFromRenderArray($element)->merge($frame);
Chris@0:     $updated_frame->applyTo($element);
Chris@0:     $this->push($updated_frame);
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Bubbles the stack.
Chris@0:    *
Chris@0:    * Whenever another level in the render array has been rendered, the stack
Chris@0:    * must be bubbled, to merge its rendering metadata with that of the parent
Chris@0:    * element.
Chris@0:    */
Chris@0:   public function bubble() {
Chris@0:     // If there's only one frame on the stack, then this is the root call, and
Chris@0:     // we can't bubble up further. ::renderRoot() will reset the stack, but we
Chris@0:     // must not reset it here to allow users of ::executeInRenderContext() to
Chris@0:     // access the stack directly.
Chris@0:     if ($this->count() === 1) {
Chris@0:       return;
Chris@0:     }
Chris@0: 
Chris@0:     // Merge the current and the parent stack frame.
Chris@0:     $current = $this->pop();
Chris@0:     $parent = $this->pop();
Chris@0:     $this->push($current->merge($parent));
Chris@0:   }
Chris@0: 
Chris@0: }