Marquee.php

<?php

namespace Drupal\render_example\Element;

use Drupal\Core\Render\Element\RenderElement;

/**
 * Provides a marquee render element.
 *
 * New render element types are defined as plugins. They live in the
 * Drupal\{module_name}\Element namespace and implement
 * \Drupal\Core\Render\Element\ElementInterface. They are annotated with either
 * \Drupal\Core\Render\Annotation\RenderElement or
 * \Drupal\Core\Render\Annotation\FormElement. And extend either the
 * \Drupal\Core\Render\Element\RenderElement, or
 * \Drupal\Core\Render\Element\FormElement base classes.
 *
 * In the annotation below we define the string "marquee" as the ID for this
 * plugin. That will also be the value used for the '#type' property in a render
 * array. For example:
 *
 * @code
 * $build['awesome'] = [
 *   '#type' => 'marquee',
 *   '#content' => 'Whoa cools, a marquee!',
 * ];
 * @endcode
 *
 * View an example of this custom element in use in
 * \Drupal\render_example\Controller\RenderExampleController::arrays().
 *
 * @see plugin_api
 * @see render_example_theme()
 *
 * @RenderElement("marquee")
 */
class Marquee extends RenderElement {
    
    /**
     * {@inheritdoc}
     */
    public function getInfo() {
        // Returns an array of default properties that will be merged with any
        // properties defined in a render array when using this element type.
        // You can use any standard render array property here, and you can also
        // custom properties that are specific to your new element type.
        return [
            // See render_example_theme() where this new theme hook is declared.
'#theme' => 'render_example_marquee',
            // Define a default #pre_render method. We will use this to handle
            // additional processing for the custom attributes we add below.
'#pre_render' => [
                [
                    self::class,
                    'preRenderMarquee',
                ],
            ],
            // This is a custom property for our element type. We set it to blank by
            // default. The expectation is that a user will add the content that they
            // would like to see inside the marquee tag. This custom property is
            // accounted for in the associated template file.
'#content' => '',
            '#attributes' => [
                'direction' => 'left',
                'loop' => -1,
                'scrollamount' => 'random',
            ],
        ];
    }
    
    /**
     * Pre-render callback; Process custom attribute options.
     *
     * @param array $element
     *   The renderable array representing the element with '#type' => 'marquee'
     *   property set.
     *
     * @return array
     *   The passed in element with changes made to attributes depending on
     *   context.
     */
    public static function preRenderMarquee(array $element) {
        // Normal attributes for a <marquee> tag do not include a 'random' option
        // for scroll amount. Our marquee element type does though. So we use this
        // #pre_render callback to check if the element was defined with the value
        // 'random' for the scrollamount attribute, and if so replace the string
        // with a random number.
        if ($element['#attributes']['scrollamount'] == 'random') {
            $element['#attributes']['scrollamount'] = abs(rand(1, 50));
        }
        return $element;
    }

}