DefaultSummary.php

<?php

namespace Drupal\views\Plugin\views\style;

use Drupal\Core\Form\FormStateInterface;

/**
 * The default style plugin for summaries.
 *
 * @ingroup views_style_plugins
 *
 * @ViewsStyle(
 *   id = "default_summary",
 *   title = @Translation("List"),
 *   help = @Translation("Displays the default summary as a list."),
 *   theme = "views_view_summary",
 *   display_types = {"summary"}
 * )
 */
class DefaultSummary extends StylePluginBase {
    protected function defineOptions() {
        $options = parent::defineOptions();
        $options['base_path'] = [
            'default' => '',
        ];
        $options['count'] = [
            'default' => TRUE,
        ];
        $options['override'] = [
            'default' => FALSE,
        ];
        $options['items_per_page'] = [
            'default' => 25,
        ];
        return $options;
    }
    public function query() {
        if (!empty($this->options['override'])) {
            $this->view
                ->setItemsPerPage(intval($this->options['items_per_page']));
        }
    }
    public function buildOptionsForm(&$form, FormStateInterface $form_state) {
        $form['base_path'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Base path'),
            '#default_value' => $this->options['base_path'],
            '#description' => $this->t('Define the base path for links in this summary
        view, i.e. http://example.com/<strong>your_view_path/archive</strong>.
        Do not include beginning and ending forward slash. If this value
        is empty, views will use the first path found as the base path,
        in page displays, or / if no path could be found.'),
        ];
        $form['count'] = [
            '#type' => 'checkbox',
            '#default_value' => !empty($this->options['count']),
            '#title' => $this->t('Display record count with link'),
        ];
        $form['override'] = [
            '#type' => 'checkbox',
            '#default_value' => !empty($this->options['override']),
            '#title' => $this->t('Override number of items to display'),
        ];
        $form['items_per_page'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Items to display'),
            '#default_value' => $this->options['items_per_page'],
            '#states' => [
                'visible' => [
                    ':input[name="options[summary][options][' . $this->definition['id'] . '][override]"]' => [
                        'checked' => TRUE,
                    ],
                ],
            ],
        ];
    }
    public function render() {
        $rows = [];
        foreach ($this->view->result as $row) {
            // @todo: Include separator as an option.
            $rows[] = $row;
        }
        return [
            '#theme' => $this->themeFunctions(),
            '#view' => $this->view,
            '#options' => $this->options,
            '#rows' => $rows,
        ];
    }

}