ViewPreviewForm.php

<?php

namespace Drupal\views_ui;

use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Url;

/**
 * Form controller for the Views preview form.
 *
 * @internal
 */
class ViewPreviewForm extends ViewFormBase {
    
    /**
     * {@inheritdoc}
     */
    public function form(array $form, FormStateInterface $form_state) {
        $view = $this->entity;
        $form['#prefix'] = '<div id="views-preview-wrapper" class="views-preview-wrapper views-admin clearfix">';
        $form['#suffix'] = '</div>';
        $form['#id'] = 'views-ui-preview-form';
        $form_state->disableCache();
        $form['controls']['#attributes'] = [
            'class' => [
                'clearfix',
            ],
        ];
        $form['controls']['title'] = [
            '#prefix' => '<h2 class="view-preview-form__title">',
            '#markup' => $this->t('Preview'),
            '#suffix' => '</h2>',
        ];
        // Add a checkbox controlling whether or not this display auto-previews.
        $form['controls']['live_preview'] = [
            '#type' => 'checkbox',
            '#id' => 'edit-displays-live-preview',
            '#title' => $this->t('Auto preview'),
            '#default_value' => \Drupal::config('views.settings')->get('ui.always_live_preview'),
        ];
        // Add the arguments textfield
        $form['controls']['view_args'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Preview with contextual filters:'),
            '#description' => $this->t('Separate contextual filter values with a "/". For example, %example.', [
                '%example' => '40/12/10',
            ]),
            '#id' => 'preview-args',
        ];
        $args = [];
        if (!$form_state->isValueEmpty('view_args')) {
            $args = explode('/', $form_state->getValue('view_args'));
        }
        $user_input = $form_state->getUserInput();
        if ($form_state->get('show_preview') || !empty($user_input['js'])) {
            $form['preview'] = [
                '#weight' => 110,
                '#theme_wrappers' => [
                    'container',
                ],
                '#attributes' => [
                    'id' => 'views-live-preview',
                    'class' => [
                        'views-live-preview',
                    ],
                ],
                'preview' => $view->renderPreview($this->displayID, $args),
            ];
        }
        $uri = $view->toUrl('preview-form');
        $uri->setRouteParameter('display_id', $this->displayID);
        $form['#action'] = $uri->toString();
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function actions(array $form, FormStateInterface $form_state) {
        $view = $this->entity;
        return [
            '#attributes' => [
                'id' => 'preview-submit-wrapper',
                'class' => [
                    'preview-submit-wrapper',
                ],
            ],
            'button' => [
                '#type' => 'submit',
                '#value' => $this->t('Update preview'),
                '#attributes' => [
                    'class' => [
                        'arguments-preview',
                    ],
                ],
                '#submit' => [
                    '::submitPreview',
                ],
                '#id' => 'preview-submit',
                '#ajax' => [
                    'url' => Url::fromRoute('entity.view.preview_form', [
                        'view' => $view->id(),
                        'display_id' => $this->displayID,
                    ]),
                    'wrapper' => 'views-preview-wrapper',
                    'event' => 'click',
                    'progress' => [
                        'type' => 'fullscreen',
                    ],
                    'method' => 'replaceWith',
                    'disable-refocus' => TRUE,
                ],
            ],
        ];
    }
    
    /**
     * Form submission handler for the Preview button.
     */
    public function submitPreview($form, FormStateInterface $form_state) {
        $form_state->set('show_preview', TRUE);
        $form_state->setRebuild();
    }

}