clean install

web/core/modules/views_ui/src/Ajax/SetFormCommand.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace Drupal\views_ui\Ajax;
+
+use Drupal\Core\Ajax\CommandInterface;
+
+/**
+ * Provides an AJAX command for setting a form submit URL in modal forms.
+ *
+ * This command is implemented in Drupal.AjaxCommands.prototype.viewsSetForm.
+ */
+class SetFormCommand implements CommandInterface {
+
+  /**
+   * The URL of the form.
+   *
+   * @var string
+   */
+  protected $url;
+
+  /**
+   * Constructs a SetFormCommand object.
+   *
+   * @param string $url
+   *   The URL of the form.
+   */
+  public function __construct($url) {
+    $this->url = $url;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function render() {
+    return [
+      'command' => 'viewsSetForm',
+      'url' => $this->url,
+    ];
+  }
+
+}

web/core/modules/views_ui/src/Controller/ViewsUIController.php

@@ -0,0 +1,225 @@
+<?php
+
+namespace Drupal\views_ui\Controller;
+
+use Drupal\Component\Utility\Tags;
+use Drupal\Core\Controller\ControllerBase;
+use Drupal\Core\Link;
+use Drupal\Core\Url;
+use Drupal\views\ViewExecutable;
+use Drupal\views\ViewEntityInterface;
+use Drupal\views\Views;
+use Drupal\views_ui\ViewUI;
+use Drupal\views\ViewsData;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\JsonResponse;
+use Drupal\Core\Ajax\AjaxResponse;
+use Drupal\Core\Ajax\ReplaceCommand;
+use Drupal\Component\Utility\Html;
+
+/**
+ * Returns responses for Views UI routes.
+ */
+class ViewsUIController extends ControllerBase {
+
+  /**
+   * Stores the Views data cache object.
+   *
+   * @var \Drupal\views\ViewsData
+   */
+  protected $viewsData;
+
+  /**
+   * Constructs a new \Drupal\views_ui\Controller\ViewsUIController object.
+   *
+   * @param \Drupal\views\ViewsData $views_data
+   *   The Views data cache object.
+   */
+  public function __construct(ViewsData $views_data) {
+    $this->viewsData = $views_data;
+  }
+
+  /**
+   * Lists all instances of fields on any views.
+   *
+   * @return array
+   *   The Views fields report page.
+   */
+  public function reportFields() {
+    $views = $this->entityTypeManager()->getStorage('view')->loadMultiple();
+
+    // Fetch all fieldapi fields which are used in views
+    // Therefore search in all views, displays and handler-types.
+    $fields = [];
+    $handler_types = ViewExecutable::getHandlerTypes();
+    foreach ($views as $view) {
+      $executable = $view->getExecutable();
+      $executable->initDisplay();
+      foreach ($executable->displayHandlers as $display_id => $display) {
+        if ($executable->setDisplay($display_id)) {
+          foreach ($handler_types as $type => $info) {
+            foreach ($executable->getHandlers($type, $display_id) as $item) {
+              $table_data = $this->viewsData->get($item['table']);
+              if (isset($table_data[$item['field']]) && isset($table_data[$item['field']][$type])
+                && $field_data = $table_data[$item['field']][$type]) {
+                // The final check that we have a fieldapi field now.
+                if (isset($field_data['field_name'])) {
+                  $fields[$field_data['field_name']][$view->id()] = $view->id();
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+
+    $header = [$this->t('Field name'), $this->t('Used in')];
+    $rows = [];
+    foreach ($fields as $field_name => $views) {
+      $rows[$field_name]['data'][0]['data']['#plain_text'] = $field_name;
+      foreach ($views as $view) {
+        $rows[$field_name]['data'][1][] = Link::fromTextAndUrl($view, new Url('entity.view.edit_form', ['view' => $view]))->toString();
+      }
+      $item_list = [
+        '#theme' => 'item_list',
+        '#items' => $rows[$field_name]['data'][1],
+        '#context' => ['list_style' => 'comma-list'],
+      ];
+      $rows[$field_name]['data'][1] = ['data' => $item_list];
+    }
+
+    // Sort rows by field name.
+    ksort($rows);
+    $output = [
+      '#type' => 'table',
+      '#header' => $header,
+      '#rows' => $rows,
+      '#empty' => $this->t('No fields have been used in views yet.'),
+    ];
+
+    return $output;
+  }
+
+  /**
+   * Lists all plugins and what enabled Views use them.
+   *
+   * @return array
+   *   The Views plugins report page.
+   */
+  public function reportPlugins() {
+    $rows = Views::pluginList();
+    foreach ($rows as &$row) {
+      $views = [];
+      // Link each view name to the view itself.
+      foreach ($row['views'] as $view) {
+        $views[] = Link::fromTextAndUrl($view, new Url('entity.view.edit_form', ['view' => $view]))->toString();
+      }
+      unset($row['views']);
+      $row['views']['data'] = [
+        '#theme' => 'item_list',
+        '#items' => $views,
+        '#context' => ['list_style' => 'comma-list'],
+      ];
+    }
+
+    // Sort rows by field name.
+    ksort($rows);
+    return [
+      '#type' => 'table',
+      '#header' => [$this->t('Type'), $this->t('Name'), $this->t('Provided by'), $this->t('Used in')],
+      '#rows' => $rows,
+      '#empty' => $this->t('There are no enabled views.'),
+    ];
+  }
+
+  /**
+   * Calls a method on a view and reloads the listing page.
+   *
+   * @param \Drupal\views\ViewEntityInterface $view
+   *   The view being acted upon.
+   * @param string $op
+   *   The operation to perform, e.g., 'enable' or 'disable'.
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The current request.
+   *
+   * @return \Drupal\Core\Ajax\AjaxResponse|\Symfony\Component\HttpFoundation\RedirectResponse
+   *   Either returns a rebuilt listing page as an AJAX response, or redirects
+   *   back to the listing page.
+   */
+  public function ajaxOperation(ViewEntityInterface $view, $op, Request $request) {
+    // Perform the operation.
+    $view->$op()->save();
+
+    // If the request is via AJAX, return the rendered list as JSON.
+    if ($request->request->get('js')) {
+      $list = $this->entityTypeManager()->getListBuilder('view')->render();
+      $response = new AjaxResponse();
+      $response->addCommand(new ReplaceCommand('#views-entity-list', $list));
+      return $response;
+    }
+
+    // Otherwise, redirect back to the page.
+    return $this->redirect('entity.view.collection');
+  }
+
+  /**
+   * Menu callback for Views tag autocompletion.
+   *
+   * Like other autocomplete functions, this function inspects the 'q' query
+   * parameter for the string to use to search for suggestions.
+   *
+   * @return \Symfony\Component\HttpFoundation\JsonResponse
+   *   A JSON response containing the autocomplete suggestions for Views tags.
+   */
+  public function autocompleteTag(Request $request) {
+    $matches = [];
+    $string = $request->query->get('q');
+    // Get matches from default views.
+    $views = $this->entityTypeManager()->getStorage('view')->loadMultiple();
+    // Keep track of previously processed tags so they can be skipped.
+    $tags = [];
+    foreach ($views as $view) {
+      $view_tag = $view->get('tag');
+      foreach (Tags::explode($view_tag) as $tag) {
+        if ($tag && !in_array($tag, $tags, TRUE)) {
+          $tags[] = $tag;
+          if (mb_stripos($tag, $string) !== FALSE) {
+            $matches[] = ['value' => $tag, 'label' => Html::escape($tag)];
+            if (count($matches) >= 10) {
+              break 2;
+            }
+          }
+        }
+      }
+    }
+
+    return new JsonResponse($matches);
+  }
+
+  /**
+   * Returns the form to edit a view.
+   *
+   * @param \Drupal\views_ui\ViewUI $view
+   *   The view to be edited.
+   * @param string|null $display_id
+   *   (optional) The display ID being edited. Defaults to NULL, which will load
+   *   the first available display.
+   *
+   * @return array
+   *   An array containing the Views edit and preview forms.
+   */
+  public function edit(ViewUI $view, $display_id = NULL) {
+    $name = $view->label();
+    $data = $this->viewsData->get($view->get('base_table'));
+
+    if (isset($data['table']['base']['title'])) {
+      $name .= ' (' . $data['table']['base']['title'] . ')';
+    }
+    $build['#title'] = $name;
+
+    $build['edit'] = $this->entityFormBuilder()->getForm($view, 'edit', ['display_id' => $display_id]);
+    $build['preview'] = $this->entityFormBuilder()->getForm($view, 'preview', ['display_id' => $display_id]);
+    return $build;
+  }
+
+}

web/core/modules/views_ui/src/Form/AdvancedSettingsForm.php

@@ -0,0 +1,101 @@
+<?php
+
+namespace Drupal\views_ui\Form;
+
+use Drupal\Core\Form\ConfigFormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\views\Views;
+
+/**
+ * Form builder for the advanced admin settings page.
+ *
+ * @internal
+ */
+class AdvancedSettingsForm extends ConfigFormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_admin_settings_advanced';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getEditableConfigNames() {
+    return ['views.settings'];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $form = parent::buildForm($form, $form_state);
+
+    $config = $this->config('views.settings');
+    $form['cache'] = [
+      '#type' => 'details',
+      '#title' => $this->t('Caching'),
+      '#open' => TRUE,
+    ];
+
+    $form['cache']['clear_cache'] = [
+      '#type' => 'submit',
+      '#value' => $this->t("Clear Views' cache"),
+      '#submit' => ['::cacheSubmit'],
+    ];
+
+    $form['debug'] = [
+      '#type' => 'details',
+      '#title' => $this->t('Debugging'),
+      '#open' => TRUE,
+    ];
+
+    $form['debug']['sql_signature'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Add Views signature to all SQL queries'),
+      '#description' => $this->t("All Views-generated queries will include the name of the views and display 'view-name:display-name' as a string at the end of the SELECT clause. This makes identifying Views queries in database server logs simpler, but should only be used when troubleshooting."),
+
+      '#default_value' => $config->get('sql_signature'),
+    ];
+
+    $options = Views::fetchPluginNames('display_extender');
+    if (!empty($options)) {
+      $form['extenders'] = [
+        '#type' => 'details',
+        '#title' => $this->t('Display extenders'),
+        '#open' => TRUE,
+      ];
+      $form['extenders']['display_extenders'] = [
+        '#default_value' => array_filter($config->get('display_extenders')),
+        '#options' => $options,
+        '#type' => 'checkboxes',
+        '#description' => $this->t('Select extensions of the views interface.'),
+      ];
+    }
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $this->config('views.settings')
+      ->set('sql_signature', $form_state->getValue('sql_signature'))
+      ->set('display_extenders', $form_state->getValue('display_extenders', []))
+      ->save();
+
+    parent::submitForm($form, $form_state);
+  }
+
+  /**
+   * Submission handler to clear the Views cache.
+   */
+  public function cacheSubmit() {
+    views_invalidate_cache();
+    $this->messenger()->addStatus($this->t('The cache has been cleared.'));
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/AddHandler.php

@@ -0,0 +1,189 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\views\ViewExecutable;
+use Drupal\views\ViewEntityInterface;
+use Drupal\views\Views;
+
+/**
+ * Provides a form for adding an item in the Views UI.
+ *
+ * @internal
+ */
+class AddHandler extends ViewsFormBase {
+
+  /**
+   * Constructs a new AddHandler object.
+   */
+  public function __construct($type = NULL) {
+    $this->setType($type);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormKey() {
+    return 'add-handler';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getForm(ViewEntityInterface $view, $display_id, $js, $type = NULL) {
+    $this->setType($type);
+    return parent::getForm($view, $display_id, $js);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_add_handler_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+    $type = $form_state->get('type');
+
+    $form = [
+      'options' => [
+        '#theme_wrappers' => ['container'],
+        '#attributes' => ['class' => ['scroll'], 'data-drupal-views-scroll' => TRUE],
+      ],
+    ];
+
+    $executable = $view->getExecutable();
+    if (!$executable->setDisplay($display_id)) {
+      $form['markup'] = ['#markup' => $this->t('Invalid display id @display', ['@display' => $display_id])];
+      return $form;
+    }
+    $display = &$executable->displayHandlers->get($display_id);
+
+    $types = ViewExecutable::getHandlerTypes();
+    $ltitle = $types[$type]['ltitle'];
+    $section = $types[$type]['plural'];
+
+    if (!empty($types[$type]['type'])) {
+      $type = $types[$type]['type'];
+    }
+
+    $form['#title'] = $this->t('Add @type', ['@type' => $ltitle]);
+    $form['#section'] = $display_id . 'add-handler';
+
+    // Add the display override dropdown.
+    views_ui_standard_display_dropdown($form, $form_state, $section);
+
+    // Figure out all the base tables allowed based upon what the relationships provide.
+    $base_tables = $executable->getBaseTables();
+    $options = Views::viewsDataHelper()->fetchFields(array_keys($base_tables), $type, $display->useGroupBy(), $form_state->get('type'));
+
+    if (!empty($options)) {
+      $form['override']['controls'] = [
+        '#theme_wrappers' => ['container'],
+        '#id' => 'views-filterable-options-controls',
+        '#attributes' => ['class' => ['form--inline', 'views-filterable-options-controls']],
+      ];
+      $form['override']['controls']['options_search'] = [
+        '#type' => 'textfield',
+        '#title' => $this->t('Search'),
+      ];
+
+      $groups = ['all' => $this->t('- All -')];
+      $form['override']['controls']['group'] = [
+        '#type' => 'select',
+        '#title' => $this->t('Category'),
+        '#options' => [],
+      ];
+
+      $form['options']['name'] = [
+        '#prefix' => '<div class="views-radio-box form-checkboxes views-filterable-options">',
+        '#suffix' => '</div>',
+        '#type' => 'tableselect',
+        '#header' => [
+          'title' => $this->t('Title'),
+          'group' => $this->t('Category'),
+          'help' => $this->t('Description'),
+        ],
+        '#js_select' => FALSE,
+      ];
+
+      $grouped_options = [];
+      foreach ($options as $key => $option) {
+        $group = preg_replace('/[^a-z0-9]/', '-', strtolower($option['group']));
+        $groups[$group] = $option['group'];
+        $grouped_options[$group][$key] = $option;
+        if (!empty($option['aliases']) && is_array($option['aliases'])) {
+          foreach ($option['aliases'] as $id => $alias) {
+            if (empty($alias['base']) || !empty($base_tables[$alias['base']])) {
+              $copy = $option;
+              $copy['group'] = $alias['group'];
+              $copy['title'] = $alias['title'];
+              if (isset($alias['help'])) {
+                $copy['help'] = $alias['help'];
+              }
+
+              $group = preg_replace('/[^a-z0-9]/', '-', strtolower($copy['group']));
+              $groups[$group] = $copy['group'];
+              $grouped_options[$group][$key . '$' . $id] = $copy;
+            }
+          }
+        }
+      }
+
+      foreach ($grouped_options as $group => $group_options) {
+        foreach ($group_options as $key => $option) {
+          $form['options']['name']['#options'][$key] = [
+            '#attributes' => [
+              'class' => ['filterable-option', $group],
+            ],
+            'title' => [
+              'data' => [
+                '#title' => $option['title'],
+                '#plain_text' => $option['title'],
+              ],
+              'class' => ['title'],
+            ],
+            'group' => $option['group'],
+            'help' => [
+              'data' => $option['help'],
+              'class' => ['description'],
+            ],
+          ];
+        }
+      }
+
+      $form['override']['controls']['group']['#options'] = $groups;
+    }
+    else {
+      $form['options']['markup'] = [
+        '#markup' => '<div class="js-form-item form-item">' . $this->t('There are no @types available to add.', ['@types' => $ltitle]) . '</div>',
+      ];
+    }
+    // Add a div to show the selected items
+    $form['selected'] = [
+      '#type' => 'item',
+      '#markup' => '<span class="views-ui-view-title">' . $this->t('Selected:') . '</span> ' . '<div class="views-selected-options"></div>',
+      '#theme_wrappers' => ['form_element', 'views_ui_container'],
+      '#attributes' => [
+        'class' => ['container-inline', 'views-add-form-selected', 'views-offset-bottom'],
+        'data-drupal-views-offset' => 'bottom',
+      ],
+    ];
+    $view->getStandardButtons($form, $form_state, 'views_ui_add_handler_form', $this->t('Add and configure @types', ['@types' => $ltitle]));
+
+    // Remove the default submit function.
+    $form['actions']['submit']['#submit'] = array_filter($form['actions']['submit']['#submit'], function ($var) {
+      return !(is_array($var) && isset($var[1]) && $var[1] == 'standardSubmit');
+    });
+    $form['actions']['submit']['#submit'][] = [$view, 'submitItemAdd'];
+
+    return $form;
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/Analyze.php

@@ -0,0 +1,62 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\views\Views;
+
+/**
+ * Displays analysis information for a view.
+ *
+ * @internal
+ */
+class Analyze extends ViewsFormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormKey() {
+    return 'analyze';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_analyze_view_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+
+    $form['#title'] = $this->t('View analysis');
+    $form['#section'] = 'analyze';
+
+    $analyzer = Views::analyzer();
+    $messages = $analyzer->getMessages($view->getExecutable());
+
+    $form['analysis'] = [
+      '#prefix' => '<div class="js-form-item form-item">',
+      '#suffix' => '</div>',
+      '#markup' => $analyzer->formatMessages($messages),
+    ];
+
+    // Inform the standard button function that we want an OK button.
+    $form_state->set('ok_button', TRUE);
+    $view->getStandardButtons($form, $form_state, 'views_ui_analyze_view_form');
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    /** @var \Drupal\views_ui\ViewUI $view */
+    $view = $form_state->get('view');
+    $form_state->setRedirectUrl($view->toUrl('edit-form'));
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/ConfigHandler.php

@@ -0,0 +1,281 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\views\ViewEntityInterface;
+use Drupal\views\ViewExecutable;
+use Drupal\views\Views;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Provides a form for configuring an item in the Views UI.
+ *
+ * @internal
+ */
+class ConfigHandler extends ViewsFormBase {
+
+  /**
+   * Constructs a new ConfigHandler object.
+   */
+  public function __construct($type = NULL, $id = NULL) {
+    $this->setType($type);
+    $this->setID($id);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormKey() {
+    return 'handler';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getForm(ViewEntityInterface $view, $display_id, $js, $type = NULL, $id = NULL) {
+    $this->setType($type);
+    $this->setID($id);
+    return parent::getForm($view, $display_id, $js);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_config_item_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state, ?Request $request = NULL) {
+    /** @var \Drupal\views\Entity\View $view */
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+    $type = $form_state->get('type');
+    $id = $form_state->get('id');
+
+    $form = [
+      'options' => [
+        '#tree' => TRUE,
+        '#theme_wrappers' => ['container'],
+        '#attributes' => ['class' => ['scroll'], 'data-drupal-views-scroll' => TRUE],
+      ],
+    ];
+    $executable = $view->getExecutable();
+    $save_ui_cache = FALSE;
+    if (!$executable->setDisplay($display_id)) {
+      $form['markup'] = ['#markup' => $this->t('Invalid display id @display', ['@display' => $display_id])];
+      return $form;
+    }
+    $item = $executable->getHandler($display_id, $type, $id);
+
+    if ($item) {
+      $handler = $executable->display_handler->getHandler($type, $id);
+      if (empty($handler)) {
+        $form['markup'] = ['#markup' => $this->t("Error: handler for @table > @field doesn't exist!", ['@table' => $item['table'], '@field' => $item['field']])];
+      }
+      else {
+        $types = ViewExecutable::getHandlerTypes();
+        $form['#title'] = $this->t('Configure @type: @item', ['@type' => $types[$type]['lstitle'], '@item' => $handler->adminLabel()]);
+
+        // If this item can come from the default display, show a dropdown
+        // that lets the user choose which display the changes should apply to.
+        if ($executable->display_handler->defaultableSections($types[$type]['plural'])) {
+          $section = $types[$type]['plural'];
+          $form_state->set('section', $section);
+          views_ui_standard_display_dropdown($form, $form_state, $section);
+        }
+
+        // A whole bunch of code to figure out what relationships are valid for
+        // this item.
+        $relationships = $executable->display_handler->getOption('relationships');
+        $relationship_options = [];
+
+        foreach ($relationships as $relationship) {
+          // Relationships can't link back to self. But also, due to ordering,
+          // relationships can only link to prior relationships.
+          if ($type == 'relationship' && $id == $relationship['id']) {
+            break;
+          }
+          $relationship_handler = Views::handlerManager('relationship')->getHandler($relationship);
+          // Ignore invalid/broken relationships.
+          if (empty($relationship_handler)) {
+            continue;
+          }
+
+          // If this relationship is valid for this type, add it to the list.
+          $data = Views::viewsData()->get($relationship['table']);
+          if (isset($data[$relationship['field']]['relationship']['base']) && $base = $data[$relationship['field']]['relationship']['base']) {
+            $base_fields = Views::viewsDataHelper()->fetchFields($base, $type, $executable->display_handler->useGroupBy());
+            if (isset($base_fields[$item['table'] . '.' . $item['field']])) {
+              $relationship_handler->init($executable, $executable->display_handler, $relationship);
+              $relationship_options[$relationship['id']] = $relationship_handler->adminLabel();
+            }
+          }
+        }
+
+        if (!empty($relationship_options)) {
+          // Make sure the existing relationship is even valid. If not, force
+          // it to none.
+          $base_fields = Views::viewsDataHelper()->fetchFields($view->get('base_table'), $type, $executable->display_handler->useGroupBy());
+          if (isset($base_fields[$item['table'] . '.' . $item['field']])) {
+            $relationship_options = array_merge(['none' => $this->t('Do not use a relationship')], $relationship_options);
+          }
+          $rel = empty($item['relationship']) ? 'none' : $item['relationship'];
+          if (empty($relationship_options[$rel])) {
+            // Pick the first relationship.
+            $rel = key($relationship_options);
+            // We want this relationship option to get saved even if the user
+            // skips submitting the form.
+            $executable->setHandlerOption($display_id, $type, $id, 'relationship', $rel);
+            $save_ui_cache = TRUE;
+            // Re-initialize with new relationship.
+            $item['relationship'] = $rel;
+            $handler->init($executable, $executable->display_handler, $item);
+          }
+
+          $form['options']['relationship'] = [
+            '#type' => 'select',
+            '#title' => $this->t('Relationship'),
+            '#options' => $relationship_options,
+            '#default_value' => $rel,
+            '#weight' => -500,
+          ];
+        }
+        else {
+          $form['options']['relationship'] = [
+            '#type' => 'value',
+            '#value' => 'none',
+          ];
+        }
+
+        if (!empty($handler->definition['help'])) {
+          $form['options']['form_description'] = [
+            '#markup' => $handler->definition['help'],
+            '#theme_wrappers' => ['container'],
+            '#attributes' => ['class' => ['js-form-item form-item description']],
+            '#weight' => -1000,
+          ];
+        }
+
+        $form['#section'] = $display_id . '-' . $type . '-' . $id;
+
+        // Get form from the handler.
+        $handler->buildOptionsForm($form['options'], $form_state);
+        $form_state->set('handler', $handler);
+      }
+
+      $name = $form_state->get('update_name');
+
+      $view->getStandardButtons($form, $form_state, 'views_ui_config_item_form', $name);
+      // Add a 'remove' button.
+      $form['actions']['remove'] = [
+        '#type' => 'submit',
+        '#value' => $this->t('Remove'),
+        '#submit' => [[$this, 'remove']],
+        '#limit_validation_errors' => [['override']],
+        '#button_type' => 'danger',
+      ];
+    }
+
+    if ($save_ui_cache) {
+      $view->cacheSet();
+    }
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {
+    $form_state->get('handler')->validateOptionsForm($form['options'], $form_state);
+
+    if ($form_state->getErrors()) {
+      $form_state->set('rerender', TRUE);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+    $id = $form_state->get('id');
+    $handler = $form_state->get('handler');
+
+    // Run it through the handler's submit function.
+    $handler->submitOptionsForm($form['options'], $form_state);
+    $item = $handler->options;
+    $types = ViewExecutable::getHandlerTypes();
+
+    // For footer/header $handler_type is area but $type is footer/header.
+    // For all other handle types it's the same.
+    $handler_type = $type = $form_state->get('type');
+    if (!empty($types[$type]['type'])) {
+      $handler_type = $types[$type]['type'];
+    }
+
+    $override = NULL;
+    $executable = $view->getExecutable();
+    if ($executable->display_handler->useGroupBy() && !empty($item['group_type'])) {
+      if (empty($executable->query)) {
+        $executable->initQuery();
+      }
+      $aggregate = $executable->query->getAggregationInfo();
+      if (!empty($aggregate[$item['group_type']]['handler'][$type])) {
+        $override = $aggregate[$item['group_type']]['handler'][$type];
+      }
+    }
+
+    // Create a new handler and unpack the options from the form onto it. We
+    // can use that for storage.
+    $handler = Views::handlerManager($handler_type)->getHandler($item, $override);
+    $handler->init($executable, $executable->display_handler, $item);
+
+    // Add the incoming options to existing options because items using
+    // the extra form may not have everything in the form here.
+    $options = $handler->submitFormCalculateOptions($handler->options, $form_state->getValue('options', []));
+
+    // This unpacks only options that are in the definition, ensuring random
+    // extra stuff on the form is not sent through.
+    $handler->unpackOptions($handler->options, $options, NULL, FALSE);
+
+    // Store the item back on the view
+    $executable->setHandler($display_id, $type, $id, $handler->options);
+
+    // Ensure any temporary options are removed.
+    if (isset($view->temporary_options[$type][$id])) {
+      unset($view->temporary_options[$type][$id]);
+    }
+
+    // Write to cache
+    $view->cacheSet();
+  }
+
+  /**
+   * Submit handler for removing an item from a view.
+   */
+  public function remove(&$form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+    $type = $form_state->get('type');
+    $id = $form_state->get('id');
+    // Store the item back on the view
+    [$was_defaulted, $is_defaulted] = $view->getOverrideValues($form, $form_state);
+    $executable = $view->getExecutable();
+    // If the display selection was changed toggle the override value.
+    if ($was_defaulted != $is_defaulted) {
+      $display = &$executable->displayHandlers->get($display_id);
+      $display->optionsOverride($form, $form_state);
+    }
+    $executable->removeHandler($display_id, $type, $id);
+
+    // Write to cache
+    $view->cacheSet();
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/ConfigHandlerExtra.php

@@ -0,0 +1,122 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\views\ViewEntityInterface;
+use Drupal\views\ViewExecutable;
+
+/**
+ * Provides a form for configuring extra information for a Views UI item.
+ *
+ * @internal
+ */
+class ConfigHandlerExtra extends ViewsFormBase {
+
+  /**
+   * Constructs a new ConfigHandlerExtra object.
+   */
+  public function __construct($type = NULL, $id = NULL) {
+    $this->setType($type);
+    $this->setID($id);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormKey() {
+    return 'handler-extra';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getForm(ViewEntityInterface $view, $display_id, $js, $type = NULL, $id = NULL) {
+    $this->setType($type);
+    $this->setID($id);
+    return parent::getForm($view, $display_id, $js);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_config_item_extra_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+    $type = $form_state->get('type');
+    $id = $form_state->get('id');
+
+    $form = [
+      'options' => [
+        '#tree' => TRUE,
+        '#theme_wrappers' => ['container'],
+        '#attributes' => ['class' => ['scroll'], 'data-drupal-views-scroll' => TRUE],
+      ],
+    ];
+    $executable = $view->getExecutable();
+    if (!$executable->setDisplay($display_id)) {
+      $form['markup'] = ['#markup' => $this->t('Invalid display id @display', ['@display' => $display_id])];
+      return $form;
+    }
+    $item = $executable->getHandler($display_id, $type, $id);
+
+    if ($item) {
+      $handler = $executable->display_handler->getHandler($type, $id);
+      if (empty($handler)) {
+        $form['markup'] = ['#markup' => $this->t("Error: handler for @table > @field doesn't exist!", ['@table' => $item['table'], '@field' => $item['field']])];
+      }
+      else {
+        $handler->init($executable, $executable->display_handler, $item);
+        $types = ViewExecutable::getHandlerTypes();
+
+        $form['#title'] = $this->t('Configure extra settings for @type %item', ['@type' => $types[$type]['lstitle'], '%item' => $handler->adminLabel()]);
+
+        $form['#section'] = $display_id . '-' . $type . '-' . $id;
+
+        // Get form from the handler.
+        $handler->buildExtraOptionsForm($form['options'], $form_state);
+        $form_state->set('handler', $handler);
+      }
+
+      $view->getStandardButtons($form, $form_state, 'views_ui_config_item_extra_form');
+    }
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {
+    $form_state->get('handler')->validateExtraOptionsForm($form['options'], $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $handler = $form_state->get('handler');
+    // Run it through the handler's submit function.
+    $handler->submitExtraOptionsForm($form['options'], $form_state);
+    $item = $handler->options;
+
+    // Store the data we're given.
+    foreach ($form_state->getValue('options') as $key => $value) {
+      $item[$key] = $value;
+    }
+
+    // Store the item back on the view
+    $view->getExecutable()->setHandler($form_state->get('display_id'), $form_state->get('type'), $form_state->get('id'), $item);
+
+    // Write to cache
+    $view->cacheSet();
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/ConfigHandlerGroup.php

@@ -0,0 +1,115 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\views\Views;
+use Drupal\views\ViewEntityInterface;
+use Drupal\views\ViewExecutable;
+
+/**
+ * Provides a form for configuring grouping information for a Views UI handler.
+ *
+ * @internal
+ */
+class ConfigHandlerGroup extends ViewsFormBase {
+
+  /**
+   * Constructs a new ConfigHandlerGroup object.
+   */
+  public function __construct($type = NULL, $id = NULL) {
+    $this->setType($type);
+    $this->setID($id);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormKey() {
+    return 'handler-group';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getForm(ViewEntityInterface $view, $display_id, $js, $type = NULL, $id = NULL) {
+    $this->setType($type);
+    $this->setID($id);
+    return parent::getForm($view, $display_id, $js);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_config_item_group_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+    $type = $form_state->get('type');
+    $id = $form_state->get('id');
+
+    $form = [
+      'options' => [
+        '#tree' => TRUE,
+        '#theme_wrappers' => ['container'],
+        '#attributes' => ['class' => ['scroll'], 'data-drupal-views-scroll' => TRUE],
+      ],
+    ];
+    $executable = $view->getExecutable();
+    if (!$executable->setDisplay($display_id)) {
+      $form['markup'] = ['#markup' => $this->t('Invalid display id @display', ['@display' => $display_id])];
+      return $form;
+    }
+
+    $executable->initQuery();
+
+    $item = $executable->getHandler($display_id, $type, $id);
+
+    if ($item) {
+      $handler = $executable->display_handler->getHandler($type, $id);
+      if (empty($handler)) {
+        $form['markup'] = ['#markup' => $this->t("Error: handler for @table > @field doesn't exist!", ['@table' => $item['table'], '@field' => $item['field']])];
+      }
+      else {
+        $handler->init($executable, $executable->display_handler, $item);
+        $types = ViewExecutable::getHandlerTypes();
+
+        $form['#title'] = $this->t('Configure aggregation settings for @type %item', ['@type' => $types[$type]['lstitle'], '%item' => $handler->adminLabel()]);
+
+        $handler->buildGroupByForm($form['options'], $form_state);
+        $form_state->set('handler', $handler);
+      }
+
+      $view->getStandardButtons($form, $form_state, 'views_ui_config_item_group_form');
+    }
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $item = &$form_state->get('handler')->options;
+    $type = $form_state->get('type');
+
+    $handler = Views::handlerManager($type)->getHandler($item);
+    $executable = $view->getExecutable();
+    $handler->init($executable, $executable->display_handler, $item);
+
+    $handler->submitGroupByForm($form, $form_state);
+
+    // Store the item back on the view
+    $executable->setHandler($form_state->get('display_id'), $form_state->get('type'), $form_state->get('id'), $item);
+
+    // Write to cache
+    $view->cacheSet();
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/Display.php

@@ -0,0 +1,116 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\views\ViewEntityInterface;
+
+/**
+ * Provides a form for editing the Views display.
+ *
+ * @internal
+ */
+class Display extends ViewsFormBase {
+
+  /**
+   * Constructs a new Display object.
+   */
+  public function __construct($type = NULL) {
+    $this->setType($type);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormKey() {
+    return 'display';
+  }
+
+  /**
+   * {@inheritdoc}
+   *
+   * @todo Remove this and switch all usage of $form_state->get('section') to
+   *   $form_state->get('type').
+   */
+  public function getFormState(ViewEntityInterface $view, $display_id, $js) {
+    $form_state = parent::getFormState($view, $display_id, $js);
+    $form_state->set('section', $this->type);
+    return $form_state;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getForm(ViewEntityInterface $view, $display_id, $js, $type = NULL) {
+    $this->setType($type);
+    return parent::getForm($view, $display_id, $js);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_edit_display_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+
+    $executable = $view->getExecutable();
+    if (!$executable->setDisplay($display_id)) {
+      $form['markup'] = ['#markup' => $this->t('Invalid display id @display', ['@display' => $display_id])];
+      return $form;
+    }
+
+    // Get form from the handler.
+    $form['options'] = [
+      '#theme_wrappers' => ['container'],
+      '#attributes' => ['class' => ['scroll'], 'data-drupal-views-scroll' => TRUE],
+    ];
+    $executable->display_handler->buildOptionsForm($form['options'], $form_state);
+
+    // The handler options form sets $form['#title'], which we need on the entire
+    // $form instead of just the ['options'] section.
+    $form['#title'] = $form['options']['#title'];
+    unset($form['options']['#title']);
+
+    // Move the override dropdown out of the scrollable section of the form.
+    if (isset($form['options']['override'])) {
+      $form['override'] = $form['options']['override'];
+      unset($form['options']['override']);
+    }
+
+    $name = $form_state->get('update_name');
+    $view->getStandardButtons($form, $form_state, 'views_ui_edit_display_form', $name);
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+    $view->getExecutable()->displayHandlers->get($display_id)->validateOptionsForm($form['options'], $form_state);
+
+    if ($form_state->getErrors()) {
+      $form_state->set('rerender', TRUE);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+    $view->getExecutable()->displayHandlers->get($display_id)->submitOptionsForm($form['options'], $form_state);
+
+    $view->cacheSet();
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/EditDetails.php

@@ -0,0 +1,92 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\views\Views;
+
+/**
+ * Provides a form for editing the details of a View.
+ *
+ * @internal
+ */
+class EditDetails extends ViewsFormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormKey() {
+    return 'edit-details';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_edit_details_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+
+    $form['#title'] = $this->t('Name and description');
+    $form['#section'] = 'details';
+
+    $form['details'] = [
+      '#theme_wrappers' => ['container'],
+      '#attributes' => ['class' => ['scroll'], 'data-drupal-views-scroll' => TRUE],
+    ];
+    $form['details']['label'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Administrative name'),
+      '#default_value' => $view->label(),
+    ];
+    $form['details']['langcode'] = [
+      '#type' => 'language_select',
+      '#title' => $this->t('View language'),
+      '#description' => $this->t('Language of labels and other textual elements in this view.'),
+      '#default_value' => $view->get('langcode'),
+    ];
+    $form['details']['description'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Administrative description'),
+      '#default_value' => $view->get('description'),
+    ];
+    $form['details']['tag'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Administrative tags'),
+      '#description' => $this->t('Enter a comma-separated list of words to describe your view.'),
+      '#default_value' => $view->get('tag'),
+      '#autocomplete_route_name' => 'views_ui.autocomplete',
+    ];
+
+    $view->getStandardButtons($form, $form_state, 'views_ui_edit_details_form');
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    foreach ($form_state->getValues() as $key => $value) {
+      // Only save values onto the view if they're actual view properties
+      // (as opposed to 'op' or 'form_build_id').
+      if (isset($form['details'][$key])) {
+        $view->set($key, $value);
+      }
+    }
+    $bases = Views::viewsData()->fetchBaseTables();
+    $page_title = $view->label();
+    if (isset($bases[$view->get('base_table')])) {
+      $page_title .= ' (' . $bases[$view->get('base_table')]['title'] . ')';
+    }
+    $form_state->set('page_title', $page_title);
+
+    $view->cacheSet();
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/Rearrange.php

@@ -0,0 +1,186 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Component\Render\FormattableMarkup;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Link;
+use Drupal\Core\Render\Markup;
+use Drupal\Core\Url;
+use Drupal\views\ViewEntityInterface;
+use Drupal\views\ViewExecutable;
+
+/**
+ * Provides a rearrange form for Views handlers.
+ *
+ * @internal
+ */
+class Rearrange extends ViewsFormBase {
+
+  /**
+   * Constructs a new Rearrange object.
+   */
+  public function __construct($type = NULL) {
+    $this->setType($type);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormKey() {
+    return 'rearrange';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getForm(ViewEntityInterface $view, $display_id, $js, $type = NULL) {
+    $this->setType($type);
+    return parent::getForm($view, $display_id, $js);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_rearrange_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+    $type = $form_state->get('type');
+
+    $types = ViewExecutable::getHandlerTypes();
+    $executable = $view->getExecutable();
+    if (!$executable->setDisplay($display_id)) {
+      $form['markup'] = ['#markup' => $this->t('Invalid display id @display', ['@display' => $display_id])];
+      return $form;
+    }
+    $display = &$executable->displayHandlers->get($display_id);
+    $form['#title'] = $this->t('Rearrange @type', ['@type' => $types[$type]['ltitle']]);
+    $form['#section'] = $display_id . 'rearrange-item';
+
+    if ($display->defaultableSections($types[$type]['plural'])) {
+      $section = $types[$type]['plural'];
+      $form_state->set('section', $section);
+      views_ui_standard_display_dropdown($form, $form_state, $section);
+    }
+
+    $count = 0;
+
+    // Get relationship labels
+    $relationships = [];
+    foreach ($display->getHandlers('relationship') as $id => $handler) {
+      $relationships[$id] = $handler->adminLabel();
+    }
+
+    $form['fields'] = [
+      '#type' => 'table',
+      '#header' => ['', $this->t('Weight'), $this->t('Remove')],
+      '#empty' => $this->t('No fields available.'),
+      '#tabledrag' => [
+        [
+          'action' => 'order',
+          'relationship' => 'sibling',
+          'group' => 'weight',
+        ],
+      ],
+      '#tree' => TRUE,
+      '#prefix' => '<div class="scroll" data-drupal-views-scroll>',
+      '#suffix' => '</div>',
+    ];
+
+    foreach ($display->getOption($types[$type]['plural']) as $id => $field) {
+      $form['fields'][$id] = [];
+
+      $form['fields'][$id]['#attributes'] = ['class' => ['draggable'], 'id' => 'views-row-' . $id];
+
+      $handler = $display->getHandler($type, $id);
+      if ($handler) {
+        $name = $handler->adminLabel() . ' ' . $handler->adminSummary();
+        if (!empty($field['relationship']) && !empty($relationships[$field['relationship']])) {
+          $name = '(' . $relationships[$field['relationship']] . ') ' . $name;
+        }
+        $markup = $name;
+      }
+      else {
+        $name = $id;
+        $markup = $this->t('Broken field @id', ['@id' => $id]);
+      }
+      $form['fields'][$id]['name'] = ['#markup' => $markup];
+
+      $form['fields'][$id]['weight'] = [
+        '#type' => 'textfield',
+        '#default_value' => ++$count,
+        '#attributes' => ['class' => ['weight']],
+        '#title' => $this->t('Weight for @title', ['@title' => $name]),
+        '#title_display' => 'invisible',
+      ];
+
+      $form['fields'][$id]['removed'] = [
+        '#type' => 'checkbox',
+        '#title' => $this->t('Remove @title', ['@title' => $name]),
+        '#title_display' => 'invisible',
+        '#id' => 'views-removed-' . $id,
+        '#attributes' => ['class' => ['views-remove-checkbox']],
+        '#default_value' => 0,
+        '#prefix' => '<div class="js-hide">',
+        '#suffix' => Markup::create('</div>' . Link::fromTextAndUrl(new FormattableMarkup('<span>@text</span>', ['@text' => $this->t('Remove')]),
+          Url::fromRoute('<none>', [], [
+            'attributes' => [
+              'id' => 'views-remove-link-' . $id,
+              'class' => ['views-hidden', 'views-button-remove', 'views-remove-link'],
+              'alt' => $this->t('Remove this item'),
+              'title' => $this->t('Remove this item'),
+            ],
+          ])
+        )->toString()),
+      ];
+    }
+
+    $view->getStandardButtons($form, $form_state, 'views_ui_rearrange_form');
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+    $type = $form_state->get('type');
+
+    $types = ViewExecutable::getHandlerTypes();
+    $display = &$view->getExecutable()->displayHandlers->get($display_id);
+
+    $old_fields = $display->getOption($types[$type]['plural']);
+    $new_fields = $order = [];
+
+    // Make an array with the weights
+    foreach ($form_state->getValue('fields') as $field => $info) {
+      // Add each value that is a field with a weight to our list, but only if
+      // it has had its 'removed' checkbox checked.
+      if (is_array($info) && isset($info['weight']) && empty($info['removed'])) {
+        $order[$field] = $info['weight'];
+      }
+    }
+
+    // Sort the array
+    asort($order);
+
+    // Create a new list of fields in the new order.
+    foreach (array_keys($order) as $field) {
+      $new_fields[$field] = $old_fields[$field];
+    }
+    $display->setOption($types[$type]['plural'], $new_fields);
+
+    // Store in cache
+    $view->cacheSet();
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/RearrangeFilter.php

@@ -0,0 +1,358 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Component\Utility\Html;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\views\ViewExecutable;
+
+/**
+ * Provides a rearrange form for Views filters.
+ *
+ * @internal
+ */
+class RearrangeFilter extends ViewsFormBase {
+
+  /**
+   * Constructs a new RearrangeFilter object.
+   */
+  public function __construct($type = NULL) {
+    $this->setType($type);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormKey() {
+    return 'rearrange-filter';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_rearrange_filter_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+    $type = 'filter';
+
+    $types = ViewExecutable::getHandlerTypes();
+    $executable = $view->getExecutable();
+    if (!$executable->setDisplay($display_id)) {
+      $form['markup'] = ['#markup' => $this->t('Invalid display id @display', ['@display' => $display_id])];
+      return $form;
+    }
+    $display = $executable->displayHandlers->get($display_id);
+    $form['#title'] = Html::escape($display->display['display_title']) . ': ';
+    $form['#title'] .= $this->t('Rearrange @type', ['@type' => $types[$type]['ltitle']]);
+    $form['#section'] = $display_id . 'rearrange-item';
+
+    if ($display->defaultableSections($types[$type]['plural'])) {
+      $section = $types[$type]['plural'];
+      $form_state->set('section', $section);
+      views_ui_standard_display_dropdown($form, $form_state, $section);
+    }
+
+    if (!empty($view->form_cache)) {
+      $groups = $view->form_cache['groups'];
+      $handlers = $view->form_cache['handlers'];
+    }
+    else {
+      $groups = $display->getOption('filter_groups');
+      $handlers = $display->getOption($types[$type]['plural']);
+    }
+    $count = 0;
+
+    // Get relationship labels
+    $relationships = [];
+    foreach ($display->getHandlers('relationship') as $id => $handler) {
+      $relationships[$id] = $handler->adminLabel();
+    }
+
+    $group_options = [];
+
+    /**
+     * Filter groups is an array that contains:
+     * [
+     *   'operator' => 'and' || 'or',
+     *   'groups' => [
+     *     $group_id => 'and' || 'or',
+     *   ],
+     * ];
+     */
+
+    $grouping = count(array_keys($groups['groups'])) > 1;
+
+    $form['filter_groups']['#tree'] = TRUE;
+    $form['filter_groups']['operator'] = [
+      '#type' => 'select',
+      '#options' => [
+        'AND' => $this->t('And'),
+        'OR' => $this->t('Or'),
+      ],
+      '#default_value' => $groups['operator'],
+      '#attributes' => [
+        'class' => ['warning-on-change'],
+      ],
+      '#title' => $this->t('Operator to use on all groups'),
+      '#description' => $this->t('Either "group 0 AND group 1 AND group 2" or "group 0 OR group 1 OR group 2", etc'),
+      '#access' => $grouping,
+    ];
+
+    $form['remove_groups']['#tree'] = TRUE;
+
+    foreach ($groups['groups'] as $id => $group) {
+      $form['filter_groups']['groups'][$id] = [
+        '#title' => $this->t('Operator'),
+        '#type' => 'select',
+        '#options' => [
+          'AND' => $this->t('And'),
+          'OR' => $this->t('Or'),
+        ],
+        '#default_value' => $group,
+        '#attributes' => [
+          'class' => ['warning-on-change'],
+        ],
+      ];
+
+      // To prevent a notice.
+      $form['remove_groups'][$id] = [];
+      if ($id != 1) {
+        $form['remove_groups'][$id] = [
+          '#type' => 'submit',
+          '#value' => $this->t('Remove group @group', ['@group' => $id]),
+          '#id' => "views-remove-group-$id",
+          '#attributes' => [
+            'class' => ['views-remove-group'],
+          ],
+          '#group' => $id,
+          '#ajax' => ['url' => NULL],
+        ];
+      }
+      $group_options[$id] = $id == 1 ? $this->t('Default group') : $this->t('Group @group', ['@group' => $id]);
+      $form['#group_renders'][$id] = [];
+    }
+
+    $form['#group_options'] = $group_options;
+    $form['#groups'] = $groups;
+    // We don't use getHandlers() because we want items without handlers to
+    // appear and show up as 'broken' so that the user can see them.
+    $form['filters'] = ['#tree' => TRUE];
+    foreach ($handlers as $id => $field) {
+      // If the group does not exist, move the filters to the default group.
+      if (empty($field['group']) || empty($groups['groups'][$field['group']])) {
+        $field['group'] = 1;
+      }
+
+      $handler = $display->getHandler($type, $id);
+      if ($grouping && $handler && !$handler->canGroup()) {
+        $field['group'] = 'ungroupable';
+      }
+
+      // If not grouping and the handler is set ungroupable, move it back to
+      // the default group to prevent weird errors from having it be in its
+      // own group:
+      if (!$grouping && $field['group'] == 'ungroupable') {
+        $field['group'] = 1;
+      }
+
+      // Place this item into the proper group for rendering.
+      $form['#group_renders'][$field['group']][] = $id;
+
+      $form['filters'][$id]['weight'] = [
+        '#title' => $this->t('Weight for @id', ['@id' => $id]),
+        '#title_display' => 'invisible',
+        '#type' => 'textfield',
+        '#default_value' => ++$count,
+        '#size' => 8,
+      ];
+      $form['filters'][$id]['group'] = [
+        '#title' => $this->t('Group for @id', ['@id' => $id]),
+        '#title_display' => 'invisible',
+        '#type' => 'select',
+        '#options' => $group_options,
+        '#default_value' => $field['group'],
+        '#attributes' => [
+          'class' => ['views-region-select', 'views-region-' . $id],
+        ],
+        '#access' => $field['group'] !== 'ungroupable',
+      ];
+
+      if ($handler) {
+        $name = $handler->adminLabel() . ' ' . $handler->adminSummary();
+        if (!empty($field['relationship']) && !empty($relationships[$field['relationship']])) {
+          $name = '(' . $relationships[$field['relationship']] . ') ' . $name;
+        }
+
+        $form['filters'][$id]['name'] = [
+          '#markup' => $name,
+        ];
+      }
+      else {
+        $form['filters'][$id]['name'] = ['#markup' => $this->t('Broken field @id', ['@id' => $id])];
+      }
+      $form['filters'][$id]['removed'] = [
+        '#title' => $this->t('Remove @id', ['@id' => $id]),
+        '#title_display' => 'invisible',
+        '#type' => 'checkbox',
+        '#id' => 'views-removed-' . $id,
+        '#attributes' => ['class' => ['views-remove-checkbox']],
+        '#default_value' => 0,
+      ];
+    }
+
+    $view->getStandardButtons($form, $form_state, 'views_ui_rearrange_filter_form');
+    $form['actions']['add_group'] = [
+      '#type' => 'submit',
+      '#value' => $this->t('Create new filter group'),
+      '#id' => 'views-add-group',
+      '#group' => 'add',
+      '#attributes' => [
+        'class' => ['views-add-group'],
+      ],
+      '#ajax' => ['url' => NULL],
+    ];
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $types = ViewExecutable::getHandlerTypes();
+    $view = $form_state->get('view');
+    $display = &$view->getExecutable()->displayHandlers->get($form_state->get('display_id'));
+    $remember_groups = [];
+
+    if (!empty($view->form_cache)) {
+      $old_fields = $view->form_cache['handlers'];
+    }
+    else {
+      $old_fields = $display->getOption($types['filter']['plural']);
+    }
+
+    $groups = $form_state->getValue('filter_groups');
+    // Whatever button was clicked, re-calculate field information.
+    $new_fields = $order = [];
+
+    // Make an array with the weights
+    foreach ($form_state->getValue('filters') as $field => $info) {
+      // Add each value that is a field with a weight to our list, but only if
+      // it has had its 'removed' checkbox checked.
+      if (is_array($info) && empty($info['removed'])) {
+        if (isset($info['weight'])) {
+          $order[$field] = $info['weight'];
+        }
+
+        if (isset($info['group'])) {
+          $old_fields[$field]['group'] = $info['group'];
+          $remember_groups[$info['group']][] = $field;
+        }
+      }
+    }
+
+    // Sort the array
+    asort($order);
+
+    // Create a new list of fields in the new order.
+    foreach (array_keys($order) as $field) {
+      $new_fields[$field] = $old_fields[$field];
+    }
+
+    // If the #group property is set on the clicked button, that means we are
+    // either adding or removing a group, not actually updating the filters.
+    $triggering_element = $form_state->getTriggeringElement();
+    if (!empty($triggering_element['#group'])) {
+      if ($triggering_element['#group'] == 'add') {
+        // Add a new group
+        $groups['groups'][] = 'AND';
+      }
+      else {
+        // Renumber groups above the removed one down.
+        foreach (array_keys($groups['groups']) as $group_id) {
+          if ($group_id >= $triggering_element['#group']) {
+            $old_group = $group_id + 1;
+            if (isset($groups['groups'][$old_group])) {
+              $groups['groups'][$group_id] = $groups['groups'][$old_group];
+              if (isset($remember_groups[$old_group])) {
+                foreach ($remember_groups[$old_group] as $id) {
+                  $new_fields[$id]['group'] = $group_id;
+                }
+              }
+            }
+            else {
+              // If this is the last one, just unset it.
+              unset($groups['groups'][$group_id]);
+            }
+          }
+        }
+      }
+      // Update our cache with values so that cancel still works the way
+      // people expect.
+      $view->form_cache = [
+        'key' => 'rearrange-filter',
+        'groups' => $groups,
+        'handlers' => $new_fields,
+      ];
+
+      // Return to this form except on actual Update.
+      $view->addFormToStack('rearrange-filter', $form_state->get('display_id'), 'filter');
+    }
+    else {
+      // The actual update button was clicked. Remove the empty groups, and
+      // renumber them sequentially.
+      ksort($remember_groups);
+      $groups['groups'] = static::arrayKeyPlus(array_values(array_intersect_key($groups['groups'], $remember_groups)));
+      // Change the 'group' key on each field to match. Here, $mapping is an
+      // array whose keys are the old group numbers and whose values are the new
+      // (sequentially numbered) ones.
+      $mapping = array_flip(static::arrayKeyPlus(array_keys($remember_groups)));
+      foreach ($new_fields as &$new_field) {
+        $new_field['group'] = $mapping[$new_field['group']];
+      }
+
+      // Write the changed handler values.
+      $display->setOption($types['filter']['plural'], $new_fields);
+      $display->setOption('filter_groups', $groups);
+      if (isset($view->form_cache)) {
+        unset($view->form_cache);
+      }
+    }
+
+    // Store in cache.
+    $view->cacheSet();
+  }
+
+  /**
+   * Adds one to each key of an array.
+   *
+   * For example [0 => 'foo'] would be [1 => 'foo'].
+   *
+   * @param array $array
+   *   The array to increment keys on.
+   *
+   * @return array
+   *   The array with incremented keys.
+   */
+  public static function arrayKeyPlus($array) {
+    $keys = array_keys($array);
+    // Sort the keys in reverse order so incrementing them doesn't overwrite any
+    // existing keys.
+    rsort($keys);
+    foreach ($keys as $key) {
+      $array[$key + 1] = $array[$key];
+      unset($array[$key]);
+    }
+    // Sort the keys back to ascending order.
+    ksort($array);
+    return $array;
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/ReorderDisplays.php

@@ -0,0 +1,198 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Component\Render\FormattableMarkup;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Url;
+
+/**
+ * Displays the display reorder form.
+ *
+ * @internal
+ */
+class ReorderDisplays extends ViewsFormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormKey() {
+    return 'reorder-displays';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_reorder_displays_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    /** @var \Drupal\views\ViewEntityInterface $view */
+    $view = $form_state->get('view');
+    $display_id = $form_state->get('display_id');
+
+    $form['#title'] = $this->t('Reorder displays');
+    $form['#section'] = 'reorder';
+    $form['#action'] = Url::fromRoute('views_ui.form_reorder_displays', [
+      'js' => 'nojs',
+      'view' => $view->id(),
+      'display_id' => $display_id,
+    ])->toString();
+    $form['view'] = [
+      '#type' => 'value',
+      '#value' => $view,
+    ];
+
+    $displays = $view->get('display');
+    $count = count($displays);
+
+    // Sort the displays.
+    uasort($displays, function ($display1, $display2) {
+      return $display1['position'] <=> $display2['position'];
+    });
+
+    $form['displays'] = [
+      '#type' => 'table',
+      '#id' => 'reorder-displays',
+      '#header' => [$this->t('Display'), $this->t('Weight'), $this->t('Remove')],
+      '#empty' => $this->t('No displays available.'),
+      '#tabledrag' => [
+        [
+          'action' => 'order',
+          'relationship' => 'sibling',
+          'group' => 'weight',
+        ],
+      ],
+      '#tree' => TRUE,
+      '#prefix' => '<div class="scroll" data-drupal-views-scroll>',
+      '#suffix' => '</div>',
+    ];
+
+    foreach ($displays as $id => $display) {
+      $form['displays'][$id] = [
+        '#display' => $display,
+        '#attributes' => [
+          'id' => 'display-row-' . $id,
+        ],
+        '#weight' => $display['position'],
+      ];
+
+      // Only make row draggable if it's not the default display.
+      if ($id !== 'default') {
+        $form['displays'][$id]['#attributes']['class'][] = 'draggable';
+      }
+
+      $form['displays'][$id]['title'] = [
+        '#markup' => $display['display_title'],
+      ];
+
+      $form['displays'][$id]['weight'] = [
+        '#type' => 'weight',
+        '#value' => $display['position'],
+        '#delta' => $count,
+        '#title' => $this->t('Weight for @display', ['@display' => $display['display_title']]),
+        '#title_display' => 'invisible',
+        '#attributes' => [
+          'class' => ['weight'],
+        ],
+      ];
+
+      $form['displays'][$id]['removed'] = [
+        'checkbox' => [
+          '#title' => $this->t('Remove @id', ['@id' => $id]),
+          '#title_display' => 'invisible',
+          '#type' => 'checkbox',
+          '#id' => 'display-removed-' . $id,
+          '#attributes' => [
+            'class' => ['views-remove-checkbox'],
+          ],
+          '#default_value' => !empty($display['deleted']),
+        ],
+        'link' => [
+          '#type' => 'link',
+          '#title' => new FormattableMarkup('<span>@text</span>', ['@text' => $this->t('Remove')]),
+          '#url' => Url::fromRoute('<none>'),
+          '#attributes' => [
+            'id' => 'display-remove-link-' . $id,
+            'class' => ['views-button-remove', 'display-remove-link'],
+            'alt' => $this->t('Remove this display'),
+            'title' => $this->t('Remove this display'),
+          ],
+        ],
+        '#access' => ($id !== 'default'),
+      ];
+
+      if (!empty($display['deleted'])) {
+        $form['displays'][$id]['deleted'] = [
+          '#type' => 'value',
+          '#value' => TRUE,
+        ];
+
+        $form['displays'][$id]['#attributes']['class'][] = 'hidden';
+      }
+
+    }
+
+    $view->getStandardButtons($form, $form_state, 'views_ui_reorder_displays_form');
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    /** @var \Drupal\views_ui\ViewUI $view */
+    $view = $form_state->get('view');
+    $order = [];
+
+    $user_input = $form_state->getUserInput();
+    foreach ($user_input['displays'] as $display => $info) {
+      // Add each value that is a field with a weight to our list, but only if
+      // it has had its 'removed' checkbox checked.
+      if (is_array($info) && isset($info['weight']) && empty($info['removed']['checkbox'])) {
+        $order[$display] = $info['weight'];
+      }
+    }
+
+    // Sort the order array.
+    asort($order);
+
+    // Remove the default display from ordering.
+    unset($order['default']);
+    // Increment up positions.
+    $position = 1;
+
+    foreach (array_keys($order) as $display) {
+      $order[$display] = $position++;
+    }
+
+    // Setting up position and removing deleted displays.
+    $displays = $view->get('display');
+    foreach ($displays as $display_id => &$display) {
+      // Don't touch the default.
+      if ($display_id === 'default') {
+        $display['position'] = 0;
+        continue;
+      }
+      if (isset($order[$display_id])) {
+        $display['position'] = $order[$display_id];
+      }
+      else {
+        $display['deleted'] = TRUE;
+      }
+    }
+    $view->set('display', $displays);
+
+    // Store in cache.
+    $view->cacheSet();
+    $url = $view->toUrl('edit-form')
+      ->setOption('fragment', 'views-tab-default');
+    $form_state->setRedirectUrl($url);
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/ViewsFormBase.php

@@ -0,0 +1,283 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Component\Utility\Html;
+use Drupal\Core\Ajax\AjaxResponse;
+use Drupal\Core\Ajax\CloseModalDialogCommand;
+use Drupal\Core\Ajax\OpenModalDialogCommand;
+use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormState;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Render\BubbleableMetadata;
+use Drupal\Core\Render\RenderContext;
+use Drupal\Core\Url;
+use Drupal\views\Ajax\HighlightCommand;
+use Drupal\views\Ajax\ReplaceTitleCommand;
+use Drupal\views\Ajax\ShowButtonsCommand;
+use Drupal\views\Ajax\TriggerPreviewCommand;
+use Drupal\views\ViewEntityInterface;
+use Drupal\views_ui\Ajax\SetFormCommand;
+use Symfony\Component\HttpFoundation\RedirectResponse;
+
+/**
+ * Provides a base class for Views UI AJAX forms.
+ */
+abstract class ViewsFormBase extends FormBase implements ViewsFormInterface {
+
+  /**
+   * The ID of the item this form is manipulating.
+   *
+   * @var string
+   */
+  protected $id;
+
+  /**
+   * The type of item this form is manipulating.
+   *
+   * @var string
+   */
+  protected $type;
+
+  /**
+   * Sets the ID for this form.
+   *
+   * @param string $id
+   *   The ID of the item this form is manipulating.
+   */
+  protected function setID($id) {
+    if ($id) {
+      $this->id = $id;
+    }
+  }
+
+  /**
+   * Sets the type for this form.
+   *
+   * @param string $type
+   *   The type of the item this form is manipulating.
+   */
+  protected function setType($type) {
+    if ($type) {
+      $this->type = $type;
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormState(ViewEntityInterface $view, $display_id, $js) {
+    // $js may already have been converted to a Boolean.
+    $ajax = is_string($js) ? $js === 'ajax' : $js;
+    return (new FormState())
+      ->set('form_id', $this->getFormId())
+      ->set('form_key', $this->getFormKey())
+      ->set('ajax', $ajax)
+      ->set('display_id', $display_id)
+      ->set('view', $view)
+      ->set('type', $this->type)
+      ->set('id', $this->id)
+      ->disableRedirect()
+      ->addBuildInfo('callback_object', $this);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getForm(ViewEntityInterface $view, $display_id, $js) {
+    /** @var \Drupal\Core\Form\FormStateInterface $form_state */
+    $form_state = $this->getFormState($view, $display_id, $js);
+    $view = $form_state->get('view');
+    $form_key = $form_state->get('form_key');
+
+    // @todo Remove the need for this.
+    \Drupal::moduleHandler()->loadInclude('views_ui', 'inc', 'admin');
+
+    // Reset the cache of IDs. Drupal rather aggressively prevents ID
+    // duplication but this causes it to remember IDs that are no longer even
+    // being used.
+    Html::resetSeenIds();
+
+    // Check to see if this is the top form of the stack. If it is, pop
+    // it off; if it isn't, the user clicked somewhere else and the stack is
+    // now irrelevant.
+    if (!empty($view->stack)) {
+      $identifier = implode('-', array_filter([$form_key, $view->id(), $display_id, $form_state->get('type'), $form_state->get('id')]));
+      // Retrieve the first form from the stack without changing the integer keys,
+      // as they're being used for the "2 of 3" progress indicator.
+      reset($view->stack);
+      $stack_key = key($view->stack);
+      $top = current($view->stack);
+      next($view->stack);
+      unset($view->stack[$stack_key]);
+
+      if (array_shift($top) != $identifier) {
+        $view->stack = [];
+      }
+    }
+
+    // Automatically remove the form cache if it is set and the key does
+    // not match. This way navigating away from the form without hitting
+    // update will work.
+    if (isset($view->form_cache) && $view->form_cache['key'] !== $form_key) {
+      unset($view->form_cache);
+    }
+
+    $form_class = get_class($form_state->getFormObject());
+    $response = $this->ajaxFormWrapper($form_class, $form_state);
+
+    // If the form has not been submitted, or was not set for rerendering, stop.
+    if (!$form_state->isSubmitted() || $form_state->get('rerender')) {
+      return $response;
+    }
+
+    // Sometimes we need to re-generate the form for multi-step type operations.
+    if (!empty($view->stack)) {
+      $stack = $view->stack;
+      $top = array_shift($stack);
+
+      // Build the new form state for the next form in the stack.
+      $reflection = new \ReflectionClass($view::$forms[$top[1]]);
+      $form_state = $reflection->newInstanceArgs(array_slice($top, 3, 2))->getFormState($view, $top[2], $form_state->get('ajax'));
+      $form_class = get_class($form_state->getFormObject());
+
+      $form_state->setUserInput([]);
+      $form_url = views_ui_build_form_url($form_state);
+      if (!$form_state->get('ajax')) {
+        return new RedirectResponse($form_url->setAbsolute()->toString());
+      }
+      $form_state->set('url', $form_url);
+      $response = $this->ajaxFormWrapper($form_class, $form_state);
+    }
+    elseif (!$form_state->get('ajax')) {
+      // If nothing on the stack, non-js forms just go back to the main view editor.
+      $display_id = $form_state->get('display_id');
+      return new RedirectResponse(Url::fromRoute('entity.view.edit_display_form', ['view' => $view->id(), 'display_id' => $display_id], ['absolute' => TRUE])->toString());
+    }
+    else {
+      $response = new AjaxResponse();
+      $response->addCommand(new CloseModalDialogCommand());
+      $response->addCommand(new ShowButtonsCommand(!empty($view->changed)));
+      $response->addCommand(new TriggerPreviewCommand());
+      if ($page_title = $form_state->get('page_title')) {
+        $response->addCommand(new ReplaceTitleCommand($page_title));
+      }
+    }
+    // If this form was for view-wide changes, there's no need to regenerate
+    // the display section of the form.
+    if ($display_id !== '') {
+      \Drupal::entityTypeManager()->getFormObject('view', 'edit')->rebuildCurrentTab($view, $response, $display_id);
+    }
+
+    return $response;
+  }
+
+  /**
+   * Wrapper for handling AJAX forms.
+   *
+   * Wrapper around \Drupal\Core\Form\FormBuilderInterface::buildForm() to
+   * handle some AJAX stuff automatically.
+   * This makes some assumptions about the client.
+   *
+   * @param \Drupal\Core\Form\FormInterface|string $form_class
+   *   The value must be one of the following:
+   *   - The name of a class that implements \Drupal\Core\Form\FormInterface.
+   *   - An instance of a class that implements \Drupal\Core\Form\FormInterface.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   *
+   * @return \Drupal\Core\Ajax\AjaxResponse|string|array
+   *   Returns one of three possible values:
+   *   - A \Drupal\Core\Ajax\AjaxResponse object.
+   *   - The rendered form, as a string.
+   *   - A render array with the title in #title and the rendered form in the
+   *   #markup array.
+   */
+  protected function ajaxFormWrapper($form_class, FormStateInterface &$form_state) {
+    /** @var \Drupal\Core\Render\RendererInterface $renderer */
+    $renderer = \Drupal::service('renderer');
+
+    // This won't override settings already in.
+    if (!$form_state->has('rerender')) {
+      $form_state->set('rerender', FALSE);
+    }
+    $ajax = $form_state->get('ajax');
+    // Do not overwrite if the redirect has been disabled.
+    if (!$form_state->isRedirectDisabled()) {
+      $form_state->disableRedirect($ajax);
+    }
+    $form_state->disableCache();
+
+    // Builds the form in a render context in order to ensure that cacheable
+    // metadata is bubbled up.
+    $render_context = new RenderContext();
+    $callable = function () use ($form_class, &$form_state) {
+      return \Drupal::formBuilder()->buildForm($form_class, $form_state);
+    };
+    $form = $renderer->executeInRenderContext($render_context, $callable);
+
+    if (!$render_context->isEmpty()) {
+      BubbleableMetadata::createFromRenderArray($form)
+        ->merge($render_context->pop())
+        ->applyTo($form);
+    }
+    $output = $renderer->renderRoot($form);
+
+    // These forms have the title built in, so set the title here:
+    $title = $form_state->get('title') ?: '';
+
+    if ($ajax && (!$form_state->isExecuted() || $form_state->get('rerender'))) {
+      // If the form didn't execute and we're using ajax, build up an
+      // Ajax command list to execute.
+      $response = new AjaxResponse();
+
+      // Attach the library necessary for using the OpenModalDialogCommand and
+      // set the attachments for this Ajax response.
+      $form['#attached']['library'][] = 'core/drupal.dialog.ajax';
+      $response->setAttachments($form['#attached']);
+
+      $display = '';
+      $status_messages = ['#type' => 'status_messages'];
+      if ($messages = $renderer->renderRoot($status_messages)) {
+        $display = '<div class="views-messages">' . $messages . '</div>';
+      }
+      $display .= $output;
+
+      $options = [
+        'classes' => [
+          'ui-dialog' => 'views-ui-dialog js-views-ui-dialog',
+        ],
+        'width' => '75%',
+      ];
+
+      $response->addCommand(new OpenModalDialogCommand($title, $display, $options));
+
+      // Views provides its own custom handling of AJAX form submissions.
+      // Usually this happens at the same path, but custom paths may be
+      // specified in $form_state.
+      $form_url = $form_state->has('url') ? $form_state->get('url')->toString() : Url::fromRoute('<current>')->toString();
+      $response->addCommand(new SetFormCommand($form_url));
+
+      if ($section = $form_state->get('#section')) {
+        $response->addCommand(new HighlightCommand('.' . Html::cleanCssIdentifier($section)));
+      }
+
+      return $response;
+    }
+
+    return $title ? ['#title' => $title, '#markup' => $output] : $output;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+  }
+
+}

web/core/modules/views_ui/src/Form/Ajax/ViewsFormInterface.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace Drupal\views_ui\Form\Ajax;
+
+use Drupal\Core\Form\FormInterface;
+use Drupal\views\ViewEntityInterface;
+
+interface ViewsFormInterface extends FormInterface {
+
+  /**
+   * Returns the key that represents this form.
+   *
+   * @return string
+   *   The form key used in the URL, e.g., the string 'add-handler' in
+   *   'admin/structure/views/%/add-handler/%/%/%'.
+   */
+  public function getFormKey();
+
+  /**
+   * Gets the form state for this form.
+   *
+   * @param \Drupal\views\ViewEntityInterface $view
+   *   The view being edited.
+   * @param string|null $display_id
+   *   The display ID being edited, or NULL to load the first available display.
+   * @param string $js
+   *   If this is an AJAX form, it will be the string 'ajax'. Otherwise, it will
+   *   be 'nojs'. This determines the response.
+   *
+   * @return \Drupal\Core\Form\FormStateInterface
+   *   The current state of the form.
+   */
+  public function getFormState(ViewEntityInterface $view, $display_id, $js);
+
+  /**
+   * Creates a new instance of this form.
+   *
+   * @param \Drupal\views\ViewEntityInterface $view
+   *   The view being edited.
+   * @param string|null $display_id
+   *   The display ID being edited, or NULL to load the first available display.
+   * @param string $js
+   *   If this is an AJAX form, it will be the string 'ajax'. Otherwise, it will
+   *   be 'nojs'. This determines the response.
+   *
+   * @return array
+   *   A form for a specific operation in the Views UI, or an array of AJAX
+   *   commands to render a form.
+   *
+   * @todo When https://www.drupal.org/node/1843224 is in, this will return
+   *   \Drupal\Core\Ajax\AjaxResponse instead of the array of AJAX commands.
+   */
+  public function getForm(ViewEntityInterface $view, $display_id, $js);
+
+}

web/core/modules/views_ui/src/Form/BasicSettingsForm.php

@@ -0,0 +1,169 @@
+<?php
+
+namespace Drupal\views_ui\Form;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\Config\TypedConfigManagerInterface;
+use Drupal\Core\Extension\ThemeHandlerInterface;
+use Drupal\Core\Form\ConfigFormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Form\RedundantEditableConfigNamesTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Form builder for the admin display defaults page.
+ *
+ * @internal
+ */
+class BasicSettingsForm extends ConfigFormBase {
+  use RedundantEditableConfigNamesTrait;
+
+  /**
+   * The theme handler.
+   *
+   * @var \Drupal\Core\Extension\ThemeHandlerInterface
+   */
+  protected $themeHandler;
+
+  /**
+   * Constructs a \Drupal\views_ui\Form\BasicSettingsForm object.
+   *
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The factory for configuration objects.
+   * @param \Drupal\Core\Config\TypedConfigManagerInterface $typedConfigManager
+   *   The typed config manager.
+   * @param \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler
+   *   The theme handler.
+   */
+  public function __construct(ConfigFactoryInterface $config_factory, TypedConfigManagerInterface $typedConfigManager, ThemeHandlerInterface $theme_handler) {
+    parent::__construct($config_factory, $typedConfigManager);
+
+    $this->themeHandler = $theme_handler;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('config.factory'),
+      $container->get('config.typed'),
+      $container->get('theme_handler')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_admin_settings_basic';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $form = parent::buildForm($form, $form_state);
+
+    $options = [];
+    foreach ($this->themeHandler->listInfo() as $name => $theme) {
+      if ($theme->status) {
+        $options[$name] = $theme->info['name'];
+      }
+    }
+
+    // This is not currently a fieldset but we may want it to be later,
+    // so this will make it easier to change if we do.
+    $form['basic'] = [];
+
+    $form['basic']['ui_show_default_display'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Always show the default display'),
+      '#config_target' => 'views.settings:ui.show.default_display',
+    ];
+
+    $form['basic']['ui_show_advanced_column'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Always show advanced display settings'),
+      '#config_target' => 'views.settings:ui.show.advanced_column',
+    ];
+
+    $form['basic']['ui_show_display_embed'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Allow embedded displays'),
+      '#description' => $this->t('Embedded displays can be used in code via views_embed_view().'),
+      '#config_target' => 'views.settings:ui.show.display_embed',
+    ];
+
+    $form['basic']['ui_exposed_filter_any_label'] = [
+      '#type' => 'select',
+      '#title' => $this->t('Label for "Any" value on non-required single-select exposed filters'),
+      '#options' => ['old_any' => '<Any>', 'new_any' => $this->t('- Any -')],
+      '#config_target' => 'views.settings:ui.exposed_filter_any_label',
+    ];
+
+    $form['live_preview'] = [
+      '#type' => 'details',
+      '#title' => $this->t('Live preview settings'),
+      '#open' => TRUE,
+    ];
+
+    $form['live_preview']['ui_always_live_preview'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Automatically update preview on changes'),
+      '#config_target' => 'views.settings:ui.always_live_preview',
+    ];
+
+    $form['live_preview']['ui_show_preview_information'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Show information and statistics about the view during live preview'),
+      '#config_target' => 'views.settings:ui.show.preview_information',
+    ];
+
+    $form['live_preview']['options'] = [
+      '#type' => 'container',
+      '#states' => [
+        'visible' => [
+          ':input[name="ui_show_preview_information"]' => ['checked' => TRUE],
+        ],
+      ],
+    ];
+
+    $form['live_preview']['options']['ui_show_sql_query_enabled'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Show the SQL query'),
+      '#config_target' => 'views.settings:ui.show.sql_query.enabled',
+    ];
+
+    $form['live_preview']['options']['ui_show_sql_query_where'] = [
+      '#type' => 'radios',
+      '#states' => [
+        'visible' => [
+          ':input[name="ui_show_sql_query_enabled"]' => ['checked' => TRUE],
+        ],
+      ],
+      '#title' => $this->t('Show SQL query'),
+      '#options' => [
+        'above' => $this->t('Above the preview'),
+        'below' => $this->t('Below the preview'),
+      ],
+      '#config_target' => 'views.settings:ui.show.sql_query.where',
+    ];
+
+    $form['live_preview']['options']['ui_show_performance_statistics'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Show performance statistics'),
+      '#config_target' => 'views.settings:ui.show.performance_statistics',
+    ];
+
+    $form['live_preview']['options']['ui_show_additional_queries'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Show other queries run during render during live preview'),
+      '#description' => $this->t("Drupal has the potential to run many queries while a view is being rendered. Checking this box will display every query run during view render as part of the live preview."),
+      '#config_target' => 'views.settings:ui.show.additional_queries',
+    ];
+
+    return $form;
+  }
+
+}

web/core/modules/views_ui/src/Form/BreakLockForm.php

@@ -0,0 +1,116 @@
+<?php
+
+namespace Drupal\views_ui\Form;
+
+use Drupal\Core\Entity\EntityConfirmFormBase;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\TempStore\SharedTempStoreFactory;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Builds the form to break the lock of an edited view.
+ *
+ * @internal
+ */
+class BreakLockForm extends EntityConfirmFormBase {
+
+  /**
+   * Stores the entity type manager.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+   */
+  protected $entityTypeManager;
+
+  /**
+   * Stores the shared tempstore.
+   *
+   * @var \Drupal\Core\TempStore\SharedTempStore
+   */
+  protected $tempStore;
+
+  /**
+   * Constructs a \Drupal\views_ui\Form\BreakLockForm object.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   The entity type manager.
+   * @param \Drupal\Core\TempStore\SharedTempStoreFactory $temp_store_factory
+   *   The factory for the temp store object.
+   */
+  public function __construct(EntityTypeManagerInterface $entity_type_manager, SharedTempStoreFactory $temp_store_factory) {
+    $this->entityTypeManager = $entity_type_manager;
+    $this->tempStore = $temp_store_factory->get('views');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('entity_type.manager'),
+      $container->get('tempstore.shared')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'views_ui_break_lock_confirm';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getQuestion() {
+    return $this->t('Do you want to break the lock on view %name?', ['%name' => $this->entity->id()]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDescription() {
+    $locked = $this->tempStore->getMetadata($this->entity->id());
+    $account = $this->entityTypeManager->getStorage('user')->load($locked->getOwnerId());
+    $username = [
+      '#theme' => 'username',
+      '#account' => $account,
+    ];
+    return $this->t('By breaking this lock, any unsaved changes made by @user will be lost.', ['@user' => \Drupal::service('renderer')->render($username)]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCancelUrl() {
+    return $this->entity->toUrl('edit-form');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getConfirmText() {
+    return $this->t('Break lock');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    if (!$this->tempStore->getMetadata($this->entity->id())) {
+      $form['message']['#markup'] = $this->t('There is no lock on view %name to break.', ['%name' => $this->entity->id()]);
+      return $form;
+    }
+    return parent::buildForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $this->tempStore->delete($this->entity->id());
+    $form_state->setRedirectUrl($this->entity->toUrl('edit-form'));
+    $this->messenger()->addStatus($this->t('The lock has been broken and you may now edit this view.'));
+  }
+
+}

web/core/modules/views_ui/src/ParamConverter/ViewUIConverter.php

@@ -0,0 +1,99 @@
+<?php
+
+namespace Drupal\views_ui\ParamConverter;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\Entity\EntityRepositoryInterface;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\ParamConverter\AdminPathConfigEntityConverter;
+use Drupal\Core\ParamConverter\ParamConverterInterface;
+use Drupal\Core\Routing\AdminContext;
+use Drupal\Core\TempStore\SharedTempStoreFactory;
+use Drupal\views_ui\ViewUI;
+use Symfony\Component\Routing\Route;
+
+/**
+ * Provides upcasting for a view entity to be used in the Views UI.
+ *
+ * Example:
+ *
+ * pattern: '/some/{view}/and/{bar}'
+ * options:
+ *   parameters:
+ *     view:
+ *       type: 'entity:view'
+ *       tempstore: TRUE
+ *
+ * The value for {view} will be converted to a view entity prepared for the
+ * Views UI and loaded from the views temp store, but it will not touch the
+ * value for {bar}.
+ */
+class ViewUIConverter extends AdminPathConfigEntityConverter implements ParamConverterInterface {
+
+  /**
+   * Stores the tempstore factory.
+   *
+   * @var \Drupal\Core\TempStore\SharedTempStoreFactory
+   */
+  protected $tempStoreFactory;
+
+  /**
+   * Constructs a new ViewUIConverter.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   The entity type manager.
+   * @param \Drupal\Core\TempStore\SharedTempStoreFactory $temp_store_factory
+   *   The factory for the temp store object.
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config factory.
+   * @param \Drupal\Core\Routing\AdminContext $admin_context
+   *   The route admin context service.
+   * @param \Drupal\Core\Entity\EntityRepositoryInterface $entity_repository
+   *   The entity repository.
+   */
+  public function __construct(EntityTypeManagerInterface $entity_type_manager, SharedTempStoreFactory $temp_store_factory, ConfigFactoryInterface $config_factory, AdminContext $admin_context, EntityRepositoryInterface $entity_repository) {
+    parent::__construct($entity_type_manager, $config_factory, $admin_context, $entity_repository);
+
+    $this->tempStoreFactory = $temp_store_factory;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function convert($value, $definition, $name, array $defaults) {
+    if (!$entity = parent::convert($value, $definition, $name, $defaults)) {
+      return;
+    }
+
+    // Get the temp store for this variable if it needs one. Attempt to load the
+    // view from the temp store, synchronize its status with the existing view,
+    // and store the lock metadata.
+    $store = $this->tempStoreFactory->get('views');
+    if ($view = $store->get($value)) {
+      if ($entity->status()) {
+        $view->enable();
+      }
+      else {
+        $view->disable();
+      }
+      $view->setLock($store->getMetadata($value));
+    }
+    // Otherwise, decorate the existing view for use in the UI.
+    else {
+      $view = new ViewUI($entity);
+    }
+
+    return $view;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function applies($definition, $name, Route $route) {
+    if (parent::applies($definition, $name, $route)) {
+      return !empty($definition['tempstore']) && $definition['type'] === 'entity:view';
+    }
+    return FALSE;
+  }
+
+}

web/core/modules/views_ui/src/ProxyClass/ParamConverter/ViewUIConverter.php

@@ -0,0 +1,88 @@
+<?php
+// phpcs:ignoreFile
+
+/**
+ * This file was generated via php core/scripts/generate-proxy-class.php 'Drupal\views_ui\ParamConverter\ViewUIConverter' "core/modules/views_ui/src".
+ */
+
+namespace Drupal\views_ui\ProxyClass\ParamConverter {
+
+    /**
+     * Provides a proxy class for \Drupal\views_ui\ParamConverter\ViewUIConverter.
+     *
+     * @see \Drupal\Component\ProxyBuilder
+     */
+    class ViewUIConverter implements \Drupal\Core\ParamConverter\ParamConverterInterface
+    {
+
+        use \Drupal\Core\DependencyInjection\DependencySerializationTrait;
+
+        /**
+         * The id of the original proxied service.
+         *
+         * @var string
+         */
+        protected $drupalProxyOriginalServiceId;
+
+        /**
+         * The real proxied service, after it was lazy loaded.
+         *
+         * @var \Drupal\views_ui\ParamConverter\ViewUIConverter
+         */
+        protected $service;
+
+        /**
+         * The service container.
+         *
+         * @var \Symfony\Component\DependencyInjection\ContainerInterface
+         */
+        protected $container;
+
+        /**
+         * Constructs a ProxyClass Drupal proxy object.
+         *
+         * @param \Symfony\Component\DependencyInjection\ContainerInterface $container
+         *   The container.
+         * @param string $drupal_proxy_original_service_id
+         *   The service ID of the original service.
+         */
+        public function __construct(\Symfony\Component\DependencyInjection\ContainerInterface $container, $drupal_proxy_original_service_id)
+        {
+            $this->container = $container;
+            $this->drupalProxyOriginalServiceId = $drupal_proxy_original_service_id;
+        }
+
+        /**
+         * Lazy loads the real service from the container.
+         *
+         * @return object
+         *   Returns the constructed real service.
+         */
+        protected function lazyLoadItself()
+        {
+            if (!isset($this->service)) {
+                $this->service = $this->container->get($this->drupalProxyOriginalServiceId);
+            }
+
+            return $this->service;
+        }
+
+        /**
+         * {@inheritdoc}
+         */
+        public function convert($value, $definition, $name, array $defaults)
+        {
+            return $this->lazyLoadItself()->convert($value, $definition, $name, $defaults);
+        }
+
+        /**
+         * {@inheritdoc}
+         */
+        public function applies($definition, $name, \Symfony\Component\Routing\Route $route)
+        {
+            return $this->lazyLoadItself()->applies($definition, $name, $route);
+        }
+
+    }
+
+}

web/core/modules/views_ui/src/ViewAddForm.php

@@ -0,0 +1,228 @@
+<?php
+
+namespace Drupal\views_ui;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\views\Plugin\views\wizard\WizardPluginBase;
+use Drupal\views\Plugin\views\wizard\WizardException;
+use Drupal\views\Plugin\ViewsPluginManager;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+
+/**
+ * Form controller for the Views add form.
+ *
+ * @internal
+ */
+class ViewAddForm extends ViewFormBase {
+
+  /**
+   * The wizard plugin manager.
+   *
+   * @var \Drupal\views\Plugin\ViewsPluginManager
+   */
+  protected $wizardManager;
+
+  /**
+   * The module handler service.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
+   * Constructs a new ViewAddForm object.
+   *
+   * @param \Drupal\views\Plugin\ViewsPluginManager $wizard_manager
+   *   The wizard plugin manager.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler service.
+   */
+  public function __construct(ViewsPluginManager $wizard_manager, ModuleHandlerInterface $module_handler) {
+    $this->wizardManager = $wizard_manager;
+    $this->moduleHandler = $module_handler;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('plugin.manager.views.wizard'),
+      $container->get('module_handler')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function prepareEntity() {
+    // Do not prepare the entity while it is being added.
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function form(array $form, FormStateInterface $form_state) {
+    $form['#attached']['library'][] = 'views_ui/views_ui.admin';
+    $form['#attributes']['class'] = ['views-admin'];
+
+    $form['name'] = [
+      '#type' => 'fieldset',
+      '#title' => $this->t('View basic information'),
+      '#attributes' => ['class' => ['fieldset-no-legend']],
+    ];
+
+    $form['name']['label'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('View name'),
+      '#required' => TRUE,
+      '#size' => 32,
+      '#default_value' => '',
+      '#maxlength' => 255,
+    ];
+    $form['name']['id'] = [
+      '#type' => 'machine_name',
+      '#maxlength' => 128,
+      '#machine_name' => [
+        'exists' => '\Drupal\views\Views::getView',
+        'source' => ['name', 'label'],
+      ],
+      '#description' => $this->t('A unique machine-readable name for this View. It must only contain lowercase letters, numbers, and underscores.'),
+    ];
+
+    $form['name']['description_enable'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Description'),
+    ];
+    $form['name']['description'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Provide description'),
+      '#title_display' => 'invisible',
+      '#size' => 64,
+      '#default_value' => '',
+      '#states' => [
+        'visible' => [
+          ':input[name="description_enable"]' => ['checked' => TRUE],
+        ],
+      ],
+    ];
+
+    // Create a wrapper for the entire dynamic portion of the form. Everything
+    // that can be updated by AJAX goes somewhere inside here. For example, this
+    // is needed by "Show" dropdown (below); it changes the base table of the
+    // view and therefore potentially requires all options on the form to be
+    // dynamically updated.
+    $form['displays'] = [];
+
+    // Create the part of the form that allows the user to select the basic
+    // properties of what the view will display.
+    $form['displays']['show'] = [
+      '#type' => 'fieldset',
+      '#title' => $this->t('View settings'),
+      '#tree' => TRUE,
+      '#attributes' => ['class' => ['container-inline']],
+    ];
+
+    // Create the "Show" dropdown, which allows the base table of the view to be
+    // selected.
+    $wizard_plugins = $this->wizardManager->getDefinitions();
+    $options = [];
+    foreach ($wizard_plugins as $key => $wizard) {
+      $options[$key] = $wizard['title'];
+    }
+    $form['displays']['show']['wizard_key'] = [
+      '#type' => 'select',
+      '#title' => $this->t('Show'),
+      '#options' => $options,
+      '#sort_options' => TRUE,
+    ];
+    $show_form = &$form['displays']['show'];
+    $default_value = $this->moduleHandler->moduleExists('node') ? 'node' : 'users';
+    $show_form['wizard_key']['#default_value'] = WizardPluginBase::getSelected($form_state, ['show', 'wizard_key'], $default_value, $show_form['wizard_key']);
+    // Changing this dropdown updates the entire content of $form['displays'] via
+    // AJAX.
+    views_ui_add_ajax_trigger($show_form, 'wizard_key', ['displays']);
+
+    // Build the rest of the form based on the currently selected wizard plugin.
+    $wizard_key = $show_form['wizard_key']['#default_value'];
+    $wizard_instance = $this->wizardManager->createInstance($wizard_key);
+    $form = $wizard_instance->buildForm($form, $form_state);
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function actions(array $form, FormStateInterface $form_state) {
+    $actions = parent::actions($form, $form_state);
+    $actions['submit']['#value'] = $this->t('Save and edit');
+    // Remove EntityFormController::save() form the submission handlers.
+    $actions['submit']['#submit'] = [[$this, 'submitForm']];
+    $actions['cancel'] = [
+      '#type' => 'submit',
+      '#value' => $this->t('Cancel'),
+      '#submit' => ['::cancel'],
+      '#limit_validation_errors' => [],
+    ];
+    return $actions;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {
+    $wizard_type = $form_state->getValue(['show', 'wizard_key']);
+    $wizard_instance = $this->wizardManager->createInstance($wizard_type);
+    $form_state->set('wizard', $wizard_instance->getPluginDefinition());
+    $form_state->set('wizard_instance', $wizard_instance);
+
+    $path = &$form_state->getValue(['page', 'path']);
+    if (!empty($path)) {
+      // @todo https://www.drupal.org/node/2423913 Views should expect and store
+      //   a leading /.
+      $path = ltrim($path, '/ ');
+    }
+    $errors = $wizard_instance->validateView($form, $form_state);
+
+    foreach ($errors as $display_errors) {
+      foreach ($display_errors as $name => $message) {
+        $form_state->setErrorByName($name, $message);
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    try {
+      /** @var \Drupal\views\Plugin\views\wizard\WizardInterface $wizard */
+      $wizard = $form_state->get('wizard_instance');
+      $this->entity = $wizard->createView($form, $form_state);
+    }
+    // @todo Figure out whether it really makes sense to throw and catch exceptions on the wizard.
+    catch (WizardException $e) {
+      $this->messenger()->addError($e->getMessage());
+      $form_state->setRedirect('entity.view.collection');
+      return;
+    }
+    $this->entity->save();
+    $this->messenger()->addStatus($this->t('The view %name has been saved.', ['%name' => $form_state->getValue('label')]));
+    $form_state->setRedirectUrl($this->entity->toUrl('edit-form'));
+  }
+
+  /**
+   * Form submission handler for the 'cancel' action.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   */
+  public function cancel(array $form, FormStateInterface $form_state) {
+    $form_state->setRedirect('entity.view.collection');
+  }
+
+}

web/core/modules/views_ui/src/ViewDuplicateForm.php

@@ -0,0 +1,146 @@
+<?php
+
+namespace Drupal\views_ui;
+
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Language\LanguageManagerInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Form controller for the Views duplicate form.
+ *
+ * @internal
+ */
+class ViewDuplicateForm extends ViewFormBase {
+
+  /**
+   * The language manager.
+   *
+   * @var \Drupal\Core\Language\LanguageManagerInterface
+   */
+  protected LanguageManagerInterface $languageManager;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('module_handler'),
+      $container->get('language_manager')
+    );
+  }
+
+  /**
+   * Constructs a ViewDuplicateForm.
+   *
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $moduleHandler
+   *   Drupal's module handler.
+   * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
+   *   The language manager.
+   */
+  public function __construct(ModuleHandlerInterface $moduleHandler, LanguageManagerInterface $language_manager) {
+    $this->setModuleHandler($moduleHandler);
+    $this->languageManager = $language_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function prepareEntity() {
+    // Do not prepare the entity while it is being added.
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function form(array $form, FormStateInterface $form_state) {
+    parent::form($form, $form_state);
+
+    $form['#title'] = $this->t('Duplicate of @label', ['@label' => $this->entity->label()]);
+
+    $form['label'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('View name'),
+      '#required' => TRUE,
+      '#size' => 32,
+      '#maxlength' => 255,
+      '#default_value' => $this->t('Duplicate of @label', ['@label' => $this->entity->label()]),
+    ];
+    $form['id'] = [
+      '#type' => 'machine_name',
+      '#maxlength' => 128,
+      '#machine_name' => [
+        'exists' => '\Drupal\views\Views::getView',
+        'source' => ['label'],
+      ],
+      '#default_value' => '',
+      '#description' => $this->t('A unique machine-readable name for this View. It must only contain lowercase letters, numbers, and underscores.'),
+    ];
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function actions(array $form, FormStateInterface $form_state) {
+    $actions['submit'] = [
+      '#type' => 'submit',
+      '#value' => $this->t('Duplicate'),
+    ];
+    return $actions;
+  }
+
+  /**
+   * Form submission handler for the 'clone' action.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   A reference to a keyed array containing the current state of the form.
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    // The original ID gets set to NULL when duplicating, so we need to store it
+    // here.
+    $original_id = $this->entity->id();
+    $this->entity = $this->entity->createDuplicate();
+    $this->entity->set('label', $form_state->getValue('label'));
+    $this->entity->set('id', $form_state->getValue('id'));
+    $this->entity->save();
+    $this->copyTranslations($original_id);
+
+    // Redirect the user to the view admin form.
+    $form_state->setRedirectUrl($this->entity->toUrl('edit-form'));
+  }
+
+  /**
+   * Copies all translations that existed on the original View.
+   *
+   * @param string $original_id
+   *   The original View ID.
+   */
+  private function copyTranslations(string $original_id): void {
+    if (!$this->moduleHandler->moduleExists('config_translation')) {
+      return;
+    }
+    $current_langcode = $this->languageManager->getConfigOverrideLanguage()
+      ->getId();
+    $languages = $this->languageManager->getLanguages();
+    $original_name = 'views.view.' . $original_id;
+    $duplicate_name = 'views.view.' . $this->entity->id();
+    foreach ($languages as $language) {
+      $langcode = $language->getId();
+      if ($langcode !== $current_langcode) {
+        $original_translation = $this->languageManager->getLanguageConfigOverride($langcode, $original_name)
+          ->get();
+        if ($original_translation) {
+          $duplicate_translation = $this->languageManager->getLanguageConfigOverride($langcode, $duplicate_name);
+          $duplicate_translation->setData($original_translation);
+          $duplicate_translation->save();
+        }
+      }
+    }
+  }
+
+}

web/core/modules/views_ui/src/ViewFormBase.php

@@ -0,0 +1,174 @@
+<?php
+
+namespace Drupal\views_ui;
+
+use Drupal\Component\Utility\Unicode;
+use Drupal\Core\Entity\EntityForm;
+use Drupal\Core\Form\FormStateInterface;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+
+/**
+ * Base form for Views forms.
+ */
+abstract class ViewFormBase extends EntityForm {
+
+  /**
+   * The name of the display used by the form.
+   *
+   * @var string
+   */
+  protected $displayID;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function init(FormStateInterface $form_state) {
+    parent::init($form_state);
+
+    // @todo Remove the need for this.
+    $form_state->loadInclude('views_ui', 'inc', 'admin');
+    $form_state->set('view', $this->entity);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state, $display_id = NULL) {
+    if (isset($display_id) && $form_state->has('display_id') && ($display_id !== $form_state->get('display_id'))) {
+      throw new \InvalidArgumentException('Mismatch between $form_state->get(\'display_id\') and $display_id.');
+    }
+    $this->displayID = $form_state->has('display_id') ? $form_state->get('display_id') : $display_id;
+    return parent::buildForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function prepareEntity() {
+    // Determine the displays available for editing.
+    if ($tabs = $this->getDisplayTabs($this->entity)) {
+      if (empty($this->displayID)) {
+        // If a display isn't specified, use the first one after sorting by
+        // #weight.
+        uasort($tabs, 'Drupal\Component\Utility\SortArray::sortByWeightProperty');
+        foreach ($tabs as $id => $tab) {
+          if (!isset($tab['#access']) || $tab['#access']) {
+            $this->displayID = $id;
+            break;
+          }
+        }
+      }
+      // If a display is specified, but we don't have access to it, return
+      // an access denied page.
+      if ($this->displayID && !isset($tabs[$this->displayID])) {
+        throw new NotFoundHttpException();
+      }
+      elseif ($this->displayID && (isset($tabs[$this->displayID]['#access']) && !$tabs[$this->displayID]['#access'])) {
+        throw new AccessDeniedHttpException();
+      }
+
+    }
+    elseif ($this->displayID) {
+      throw new NotFoundHttpException();
+    }
+  }
+
+  /**
+   * Adds tabs for navigating across Displays when editing a View.
+   *
+   * This function can be called from hook_menu_local_tasks_alter() to implement
+   * these tabs as secondary local tasks, or it can be called from elsewhere if
+   * having them as secondary local tasks isn't desired. The caller is responsible
+   * for setting the active tab's #active property to TRUE.
+   *
+   * @param \Drupal\views_ui\ViewUI $view
+   *   The ViewUI entity.
+   *
+   * @return array
+   *   An array of tab definitions.
+   */
+  public function getDisplayTabs(ViewUI $view) {
+    $executable = $view->getExecutable();
+    $executable->initDisplay();
+    $display_id = $this->displayID;
+    $tabs = [];
+
+    // Create a tab for each display.
+    foreach ($view->get('display') as $id => $display) {
+      // Get an instance of the display plugin, to make sure it will work in the
+      // UI.
+      $display_plugin = $executable->displayHandlers->get($id);
+      if (empty($display_plugin)) {
+        continue;
+      }
+
+      $tabs[$id] = [
+        '#theme' => 'menu_local_task',
+        '#weight' => $display['position'],
+        '#link' => [
+          'title' => $this->getDisplayLabel($view, $id),
+          'localized_options' => [],
+          'url' => $view->toUrl('edit-display-form')->setRouteParameter('display_id', $id),
+        ],
+      ];
+      if (!empty($display['deleted'])) {
+        $tabs[$id]['#link']['localized_options']['attributes']['class'][] = 'views-display-deleted-link';
+      }
+      if (isset($display['display_options']['enabled']) && !$display['display_options']['enabled']) {
+        $tabs[$id]['#link']['localized_options']['attributes']['class'][] = 'views-display-disabled-link';
+      }
+    }
+
+    // If the default display isn't supposed to be shown, don't display its tab, unless it's the only display.
+    if ((!$this->isDefaultDisplayShown($view) && $display_id != 'default') && count($tabs) > 1) {
+      $tabs['default']['#access'] = FALSE;
+    }
+
+    // Mark the display tab as red to show validation errors.
+    $errors = $executable->validate();
+    foreach ($view->get('display') as $id => $display) {
+      if (!empty($errors[$id])) {
+        // Always show the tab.
+        $tabs[$id]['#access'] = TRUE;
+        // Add a class to mark the error and a title to make a hover tip.
+        $tabs[$id]['#link']['localized_options']['attributes']['class'][] = 'error';
+        $tabs[$id]['#link']['localized_options']['attributes']['title'] = $this->t('This display has one or more validation errors.');
+      }
+    }
+
+    return $tabs;
+  }
+
+  /**
+   * Controls whether or not the default display should have its own tab on edit.
+   */
+  public function isDefaultDisplayShown(ViewUI $view) {
+    // Always show the default display for advanced users who prefer that mode.
+    $advanced_mode = \Drupal::config('views.settings')->get('ui.show.default_display');
+    // For other users, show the default display only if there are no others, and
+    // hide it if there's at least one "real" display.
+    $additional_displays = (count($view->getExecutable()->displayHandlers) == 1);
+
+    return $advanced_mode || $additional_displays;
+  }
+
+  /**
+   * Placeholder function for overriding $display['display_title'].
+   *
+   * @todo Remove this function once editing the display title is possible.
+   */
+  public function getDisplayLabel(ViewUI $view, $display_id, $check_changed = TRUE) {
+    $display = $view->get('display');
+    $title = $display_id == 'default' ? $this->t('Default') : $display[$display_id]['display_title'];
+    $title = Unicode::truncate($title, 25, FALSE, TRUE);
+
+    if ($check_changed && !empty($view->changed_display[$display_id])) {
+      $changed = '*';
+      $title = $title . $changed;
+    }
+
+    return $title;
+  }
+
+}

web/core/modules/views_ui/src/ViewListBuilder.php

@@ -0,0 +1,291 @@
+<?php
+
+namespace Drupal\views_ui;
+
+use Drupal\Component\Plugin\PluginManagerInterface;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Config\Entity\ConfigEntityListBuilder;
+use Drupal\Core\Entity\EntityStorageInterface;
+use Drupal\Core\Entity\EntityTypeInterface;
+use Drupal\Core\Link;
+use Drupal\Core\Url;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\Exception\BadRequestException;
+use Symfony\Component\HttpKernel\Exception\NotAcceptableHttpException;
+
+/**
+ * Defines a class to build a listing of view entities.
+ *
+ * @see \Drupal\views\Entity\View
+ */
+class ViewListBuilder extends ConfigEntityListBuilder {
+
+  /**
+   * The views display plugin manager to use.
+   *
+   * @var \Drupal\Component\Plugin\PluginManagerInterface
+   */
+  protected $displayManager;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
+    return new static(
+      $entity_type,
+      $container->get('entity_type.manager')->getStorage($entity_type->id()),
+      $container->get('plugin.manager.views.display')
+    );
+  }
+
+  /**
+   * Constructs a new ViewListBuilder object.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
+   *   The entity type definition.
+   * @param \Drupal\Core\Entity\EntityStorageInterface $storage
+   *   The entity storage class.
+   * @param \Drupal\Component\Plugin\PluginManagerInterface $display_manager
+   *   The views display plugin manager to use.
+   */
+  public function __construct(EntityTypeInterface $entity_type, EntityStorageInterface $storage, PluginManagerInterface $display_manager) {
+    parent::__construct($entity_type, $storage);
+
+    $this->displayManager = $display_manager;
+    // This list builder uses client-side filters which requires all entities to
+    // be listed, disable the pager.
+    // @todo https://www.drupal.org/node/2536826 change the filtering to support
+    //   a pager.
+    $this->limit = FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function load() {
+    $entities = [
+      'enabled' => [],
+      'disabled' => [],
+    ];
+    foreach (parent::load() as $entity) {
+      if ($entity->status()) {
+        $entities['enabled'][] = $entity;
+      }
+      else {
+        $entities['disabled'][] = $entity;
+      }
+    }
+    return $entities;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildRow(EntityInterface $view) {
+    $row = parent::buildRow($view);
+    return [
+      'data' => [
+        'view_name' => [
+          'data' => [
+            '#plain_text' => $view->label(),
+          ],
+        ],
+        'machine_name' => [
+          'data' => [
+            '#plain_text' => $view->id(),
+          ],
+        ],
+        'description' => [
+          'data' => [
+            '#plain_text' => $view->get('description'),
+          ],
+        ],
+        'displays' => [
+          'data' => [
+            '#theme' => 'views_ui_view_displays_list',
+            '#displays' => $this->getDisplaysList($view),
+          ],
+        ],
+        'operations' => $row['operations'],
+      ],
+      '#attributes' => [
+        'class' => [$view->status() ? 'views-ui-list-enabled' : 'views-ui-list-disabled'],
+      ],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildHeader() {
+    return [
+      'view_name' => [
+        'data' => $this->t('View name'),
+        '#attributes' => [
+          'class' => ['views-ui-name'],
+        ],
+      ],
+      'machine_name' => [
+        'data' => $this->t('Machine name'),
+        '#attributes' => [
+          'class' => ['views-ui-machine-name'],
+        ],
+      ],
+      'description' => [
+        'data' => $this->t('Description'),
+        '#attributes' => [
+          'class' => ['views-ui-description'],
+        ],
+      ],
+      'displays' => [
+        'data' => $this->t('Displays'),
+        '#attributes' => [
+          'class' => ['views-ui-displays'],
+        ],
+      ],
+      'operations' => [
+        'data' => $this->t('Operations'),
+        '#attributes' => [
+          'class' => ['views-ui-operations'],
+        ],
+      ],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDefaultOperations(EntityInterface $entity) {
+    $operations = parent::getDefaultOperations($entity);
+    // Remove destination redirect for Edit operation.
+    $operations['edit']['url'] = $entity->toUrl('edit-form');
+
+    if ($entity->hasLinkTemplate('duplicate-form')) {
+      $operations['duplicate'] = [
+        'title' => $this->t('Duplicate'),
+        'weight' => 15,
+        'url' => $entity->toUrl('duplicate-form'),
+      ];
+    }
+
+    // Add AJAX functionality to enable/disable operations.
+    foreach (['enable', 'disable'] as $op) {
+      if (isset($operations[$op])) {
+        $operations[$op]['url'] = $entity->toUrl($op);
+        // Enable and disable operations should use AJAX.
+        $operations[$op]['attributes']['class'][] = 'use-ajax';
+      }
+    }
+
+    // ajax.js focuses automatically on the data-drupal-selector element. When
+    // enabling the view again, focusing on the disable link doesn't work, as it
+    // is hidden. We assign data-drupal-selector to every link, so it focuses
+    // on the edit link.
+    foreach ($operations as &$operation) {
+      $operation['attributes']['data-drupal-selector'] = 'views-listing-' . $entity->id();
+    }
+
+    return $operations;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function render() {
+    $entities = $this->load();
+    $list['#type'] = 'container';
+    $list['#attributes']['id'] = 'views-entity-list';
+
+    $list['#attached']['library'][] = 'core/drupal.ajax';
+    $list['#attached']['library'][] = 'views_ui/views_ui.listing';
+
+    $list['filters'] = [
+      '#type' => 'container',
+      '#attributes' => [
+        'class' => ['table-filter', 'js-show'],
+      ],
+    ];
+
+    $list['filters']['text'] = [
+      '#type' => 'search',
+      '#title' => $this->t('Filter'),
+      '#title_display' => 'invisible',
+      '#size' => 60,
+      '#placeholder' => $this->t('Filter by view name, machine name, description, or display path'),
+      '#attributes' => [
+        'class' => ['views-filter-text'],
+        'data-table' => '.views-listing-table',
+        'autocomplete' => 'off',
+        'title' => $this->t('Enter a part of the view name, machine name, description, or display path to filter by.'),
+      ],
+    ];
+
+    $list['enabled']['heading']['#markup'] = '<h2>' . $this->t('Enabled', [], ['context' => 'Plural']) . '</h2>';
+    $list['disabled']['heading']['#markup'] = '<h2>' . $this->t('Disabled', [], ['context' => 'Plural']) . '</h2>';
+    foreach (['enabled', 'disabled'] as $status) {
+      $list[$status]['#type'] = 'container';
+      $list[$status]['#attributes'] = ['class' => ['views-list-section', $status]];
+      $list[$status]['table'] = [
+        '#theme' => 'views_ui_views_listing_table',
+        '#headers' => $this->buildHeader(),
+        '#attributes' => ['class' => ['views-listing-table', $status]],
+      ];
+      foreach ($entities[$status] as $entity) {
+        $list[$status]['table']['#rows'][$entity->id()] = $this->buildRow($entity);
+      }
+    }
+    $list['enabled']['table']['#empty'] = $this->t('There are no enabled views.');
+    $list['disabled']['table']['#empty'] = $this->t('There are no disabled views.');
+
+    return $list;
+  }
+
+  /**
+   * Gets a list of displays included in the view.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $view
+   *   The view entity instance to get a list of displays for.
+   *
+   * @return array
+   *   An array of display types that this view includes.
+   */
+  protected function getDisplaysList(EntityInterface $view) {
+    $displays = [];
+
+    $executable = $view->getExecutable();
+    $executable->initDisplay();
+    foreach ($executable->displayHandlers as $display) {
+      $rendered_path = FALSE;
+      $definition = $display->getPluginDefinition();
+      if (!empty($definition['admin'])) {
+        if ($display->hasPath()) {
+          $path = $display->getPath();
+          if ($view->status() && !str_contains($path, '%')) {
+            // Wrap this in a try/catch as trying to generate links to some
+            // routes may throw an exception, for example if they do not
+            // respond to HTML, such as RESTExports.
+            try {
+              // @todo Views should expect and store a leading /. See:
+              //   https://www.drupal.org/node/2423913
+              $rendered_path = Link::fromTextAndUrl('/' . $path, Url::fromUserInput('/' . $path))->toString();
+            }
+            catch (BadRequestException | NotAcceptableHttpException $e) {
+              $rendered_path = '/' . $path;
+            }
+          }
+          else {
+            $rendered_path = '/' . $path;
+          }
+        }
+        $displays[] = [
+          'display' => $definition['admin'],
+          'path' => $rendered_path,
+        ];
+      }
+    }
+
+    sort($displays);
+    return $displays;
+  }
+
+}

web/core/modules/views_ui/src/ViewPreviewForm.php

@@ -0,0 +1,109 @@
+<?php
+
+namespace Drupal\views_ui;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Form\WorkspaceSafeFormInterface;
+use Drupal\Core\Url;
+
+/**
+ * Form controller for the Views preview form.
+ *
+ * @internal
+ */
+class ViewPreviewForm extends ViewFormBase implements WorkspaceSafeFormInterface {
+
+  /**
+   * {@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->getValue('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();
+  }
+
+}