class PagerTestController

class PagerTestController extends ControllerBase implements TrustedCallbackInterface {
    
    /**
     * The pager request service.
     *
     * @var \Drupal\Core\Pager\PagerParametersInterface
     */
    protected $pagerParams;
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('pager.parameters'));
    }
    
    /**
     * Construct a new PagerTestController object.
     *
     * @param \Drupal\Core\Pager\PagerParametersInterface $pager_params
     *   The pager parameters.
     */
    public function __construct(PagerParametersInterface $pager_params) {
        $this->pagerParams = $pager_params;
    }
    
    /**
     * Builds a render array for a multi-page test table.
     *
     * @param int $element
     *   The pager element to be used for paging.
     * @param int $limit
     *   The limit of rows per page for the specified element.
     *
     * @return array
     *   A render array.
     */
    protected function buildTestTable($element, $limit) {
        $header = [
            [
                'data' => 'wid',
            ],
            [
                'data' => 'type',
            ],
            [
                'data' => 'timestamp',
            ],
        ];
        $query = Database::getConnection()->select('watchdog', 'd')
            ->extend(PagerSelectExtender::class)
            ->element($element);
        $result = $query->fields('d', [
            'wid',
            'type',
            'timestamp',
        ])
            ->limit($limit)
            ->orderBy('d.wid')
            ->execute();
        $rows = [];
        foreach ($result as $row) {
            $rows[] = [
                'data' => (array) $row,
            ];
        }
        return [
            '#theme' => 'table',
            '#header' => $header,
            '#rows' => $rows,
            '#empty' => $this->t("There are no watchdog records found in the db"),
        ];
    }
    
    /**
     * Returns a pager with 'parameters' variable.
     *
     * The 'pager_calls' parameter counts the calls to the pager, subsequent
     * to the initial call.
     */
    public function queryParameters() {
        // Example query.
        $build['pager_table_0'] = $this->buildTestTable(0, 5);
        // Counter of calls to the current pager.
        $query_params = $this->pagerParams
            ->getQueryParameters();
        $pager_calls = isset($query_params['pager_calls']) ? $query_params['pager_calls'] ? $query_params['pager_calls'] : 0 : 0;
        $build['l_pager_pager_0'] = [
            '#markup' => $this->t('Pager calls: @pager_calls', [
                '@pager_calls' => $pager_calls,
            ]),
        ];
        // Pager.
        $build['pager_pager_0'] = [
            '#type' => 'pager',
            '#element' => 0,
            '#parameters' => [
                'pager_calls' => ++$pager_calls,
            ],
            '#pre_render' => [
                'Drupal\\pager_test\\Controller\\PagerTestController::showPagerCacheContext',
            ],
        ];
        return $build;
    }
    
    /**
     * Returns a page with multiple pagers.
     */
    public function multiplePagers() {
        // Build three tables with same query and different pagers.
        $build['pager_table_0'] = $this->buildTestTable(0, 20);
        $build['pager_pager_0'] = [
            '#type' => 'container',
            '#attributes' => [
                'class' => [
                    'test-pager-0',
                ],
            ],
            'pager' => [
                '#type' => 'pager',
                '#element' => 0,
            ],
        ];
        $build['pager_table_1'] = $this->buildTestTable(1, 20);
        $build['pager_pager_1'] = [
            '#type' => 'container',
            '#attributes' => [
                'class' => [
                    'test-pager-1',
                ],
            ],
            'pager' => [
                '#type' => 'pager',
                '#element' => 1,
            ],
        ];
        $build['pager_table_4'] = $this->buildTestTable(4, 20);
        $build['pager_pager_4'] = [
            '#type' => 'container',
            '#attributes' => [
                'class' => [
                    'test-pager-4',
                ],
            ],
            'pager' => [
                '#type' => 'pager',
                '#element' => 4,
            ],
        ];
        return $build;
    }
    
    /**
     * #pre_render callback for #type => pager that shows the pager cache context.
     */
    public static function showPagerCacheContext(array $pager) {
        \Drupal::messenger()->addStatus(\Drupal::service('cache_contexts_manager')->convertTokensToKeys([
            'url.query_args.pagers:' . $pager['#element'],
        ])
            ->getKeys()[0]);
        return $pager;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function trustedCallbacks() {
        return [
            'showPagerCacheContext',
        ];
    }

}