class SystemCompactLink

class SystemCompactLink extends Link {
    
    /**
     * {@inheritdoc}
     */
    public function getInfo() {
        $class = get_class($this);
        return [
            '#pre_render' => [
                [
                    $class,
                    'preRenderCompactLink',
                ],
                [
                    $class,
                    'preRenderLink',
                ],
            ],
            '#theme_wrappers' => [
                'container' => [
                    '#attributes' => [
                        'class' => [
                            'compact-link',
                        ],
                    ],
                ],
            ],
        ];
    }
    
    /**
     * Pre-render callback: Renders a link into #markup.
     *
     * Doing so during pre_render gives modules a chance to alter the link parts.
     *
     * @param array $element
     *   A structured array whose keys form the arguments to Drupal::l():
     *   - #title: The link text to pass as argument to Drupal::l().
     *   - One of the following:
     *     - #route_name and (optionally) a #route_parameters array; The route
     *       name and route parameters which will be passed into the link
     *       generator.
     *     - #href: The system path or URL to pass as argument to Drupal::l().
     *   - #options: (optional) An array of options to pass to Drupal::l() or the
     *     link generator.
     *
     * @return array
     *   The passed-in element containing the system compact link default values.
     */
    public static function preRenderCompactLink($element) {
        // By default, link options to pass to l() are normally set in #options.
        $element += [
            '#options' => [],
        ];
        if (system_admin_compact_mode()) {
            $element['#title'] = t('Show descriptions');
            $element['#url'] = BaseUrl::fromRoute('system.admin_compact_page', [
                'mode' => 'off',
            ]);
            $element['#options'] = [
                'attributes' => [
                    'title' => t('Expand layout to include descriptions.'),
                ],
                'query' => \Drupal::destination()->getAsArray(),
            ];
        }
        else {
            $element['#title'] = t('Hide descriptions');
            $element['#url'] = BaseUrl::fromRoute('system.admin_compact_page', [
                'mode' => 'on',
            ]);
            $element['#options'] = [
                'attributes' => [
                    'title' => t('Compress layout by hiding descriptions.'),
                ],
                'query' => \Drupal::destination()->getAsArray(),
            ];
        }
        $options = NestedArray::mergeDeep($element['#url']->getOptions(), $element['#options']);
        $element['#markup'] = BaseLink::fromTextAndUrl($element['#title'], $element['#url']->setOptions($options))
            ->toString();
        return $element;
    }

}