drupal/core/modules/views_ui/views_ui.module

<?php

/**
 * @file
 * Provide structure for the administrative interface to Views.
 */

use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Url;
use Drupal\views\ViewExecutable;
use Drupal\views\Analyzer;

/**
 * Implements hook_help().
 */
function views_ui_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    case 'help.page.views_ui':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The Views UI module provides an interface for managing views for the <a href=":views">Views module</a>. For more information, see the <a href=":handbook">online documentation for the Views UI module</a>.', [':views' => Url::fromRoute('help.page', ['name' => 'views'])->toString(), ':handbook' => 'https://www.drupal.org/documentation/modules/views_ui']) . '</p>';
      $output .= '<h3>' . t('Uses') . '</h3>';
      $output .= '<dl>';
      $output .= '<dt>' . t('Creating and managing views') . '</dt>';
      $output .= '<dd>' . t('Views can be created from the <a href=":list">Views list page</a> by using the "Add view" action. Existing views can be managed from the <a href=":list">Views list page</a> by locating the view in the "Enabled" or "Disabled" list and selecting the desired operation action, for example "Edit".', [':list' => Url::fromRoute('entity.view.collection', ['name' => 'views_ui'])->toString()]) . '</dd>';
      $output .= '<dt>' . t('Enabling and disabling views') . '<dt>';
      $output .= '<dd>' . t('Views can be enabled or disabled from the <a href=":list">Views list page</a>. To enable a view, find the view within the "Disabled" list and select the "Enable" operation. To disable a view find the view within the "Enabled" list and select the "Disable" operation.', [':list' => Url::fromRoute('entity.view.collection', ['name' => 'views_ui'])->toString()]) . '</dd>';
      $output .= '<dt>' . t('Exporting and importing views') . '</dt>';
      $output .= '<dd>' . t('Views can be exported and imported as configuration files by using the <a href=":config">Configuration Manager module</a>.', [':config' => (\Drupal::moduleHandler()->moduleExists('config')) ? Url::fromRoute('help.page', ['name' => 'config'])->toString() : '#']) . '</dd>';
      $output .= '</dl>';
      return $output;
  }
}

/**
 * Implements hook_entity_type_build().
 */
function views_ui_entity_type_build(array &$entity_types) {
  /** @var \Drupal\Core\Entity\EntityTypeInterface[] $entity_types */
  $entity_types['view']
    ->setFormClass('edit', 'Drupal\views_ui\ViewEditForm')
    ->setFormClass('add', 'Drupal\views_ui\ViewAddForm')
    ->setFormClass('preview', 'Drupal\views_ui\ViewPreviewForm')
    ->setFormClass('duplicate', 'Drupal\views_ui\ViewDuplicateForm')
    ->setFormClass('delete', 'Drupal\Core\Entity\EntityDeleteForm')
    ->setFormClass('break_lock', 'Drupal\views_ui\Form\BreakLockForm')
    ->setListBuilderClass('Drupal\views_ui\ViewListBuilder')
    ->setLinkTemplate('edit-form', '/admin/structure/views/view/{view}')
    ->setLinkTemplate('edit-display-form', '/admin/structure/views/view/{view}/edit/{display_id}')
    ->setLinkTemplate('preview-form', '/admin/structure/views/view/{view}/preview/{display_id}')
    ->setLinkTemplate('duplicate-form', '/admin/structure/views/view/{view}/duplicate')
    ->setLinkTemplate('delete-form', '/admin/structure/views/view/{view}/delete')
    ->setLinkTemplate('enable', '/admin/structure/views/view/{view}/enable')
    ->setLinkTemplate('disable', '/admin/structure/views/view/{view}/disable')
    ->setLinkTemplate('break-lock-form', '/admin/structure/views/view/{view}/break-lock')
    ->setLinkTemplate('collection', '/admin/structure/views');
}

/**
 * Implements hook_theme().
 */
function views_ui_theme() {
  return [
    // edit a view
    'views_ui_display_tab_setting' => [
      'variables' => ['description' => '', 'link' => '', 'settings_links' => [], 'overridden' => FALSE, 'defaulted' => FALSE, 'description_separator' => TRUE, 'class' => []],
      'file' => 'views_ui.theme.inc',
    ],
    'views_ui_display_tab_bucket' => [
      'render element' => 'element',
      'file' => 'views_ui.theme.inc',
    ],
    'views_ui_rearrange_filter_form' => [
      'render element' => 'form',
      'file' => 'views_ui.theme.inc',
    ],
    'views_ui_expose_filter_form' => [
      'render element' => 'form',
      'file' => 'views_ui.theme.inc',
    ],

    // Legacy theme hook for displaying views info.
    'views_ui_view_info' => [
      'variables' => ['view' => NULL, 'displays' => NULL],
      'file' => 'views_ui.theme.inc',
    ],

    // List views.
    'views_ui_views_listing_table' => [
      'variables' => [
        'headers' => NULL,
        'rows' => NULL,
        'attributes' => [],
      ],
      'file' => 'views_ui.theme.inc',
    ],
    'views_ui_view_displays_list' => [
      'variables' => ['displays' => []],
    ],

    // Group of filters.
    'views_ui_build_group_filter_form' => [
      'render element' => 'form',
      'file' => 'views_ui.theme.inc',
    ],

    // On behalf of a plugin
    'views_ui_style_plugin_table' => [
      'render element' => 'form',
      'file' => 'views_ui.theme.inc',
    ],

    // When previewing a view.
    'views_ui_view_preview_section' => [
      'variables' => ['view' => NULL, 'section' => NULL, 'content' => NULL, 'links' => ''],
      'file' => 'views_ui.theme.inc',
    ],

    // Generic container wrapper, to use instead of theme_container when an id
    // is not desired.
    'views_ui_container' => [
      'variables' => ['children' => NULL, 'attributes' => []],
      'file' => 'views_ui.theme.inc',
    ],
  ];
}

/**
 * Implements hook_preprocess_HOOK() for views templates.
 */
function views_ui_preprocess_views_view(&$variables) {
  $view = $variables['view'];

  // Render title for the admin preview.
  if (!empty($view->live_preview)) {
    $variables['title'] = [
      '#markup' => $view->getTitle(),
    ];
  }

  if (!empty($view->live_preview) && \Drupal::moduleHandler()->moduleExists('contextual')) {
    $view->setShowAdminLinks(FALSE);
    foreach (['title', 'header', 'exposed', 'rows', 'pager', 'more', 'footer', 'empty', 'attachment_after', 'attachment_before'] as $section) {
      if (!empty($variables[$section])) {
        $variables[$section] = [
          '#theme' => 'views_ui_view_preview_section',
          '#view' => $view,
          '#section' => $section,
          '#content' => $variables[$section],
          '#theme_wrappers' => ['views_ui_container'],
          '#attributes' => ['class' => ['contextual-region']],
        ];
      }
    }
  }
}

/**
 * Implements hook_theme_suggestions_HOOK().
 */
function views_ui_theme_suggestions_views_ui_view_preview_section(array $variables) {
  return ['views_ui_view_preview_section__' . $variables['section']];
}

/**
 * Returns contextual links for each handler of a certain section.
 *
 * @TODO
 *   Bring in relationships
 *   Refactor this function to use much stuff of views_ui_edit_form_get_bucket.
 *
 * @param $title
 *   Add a bolded title of this section.
 */
function views_ui_view_preview_section_handler_links(ViewExecutable $view, $type, $title = FALSE) {
  $display = $view->display_handler->display;
  $handlers = $view->display_handler->getHandlers($type);
  $links = [];

  $types = ViewExecutable::getHandlerTypes();
  if ($title) {
    $links[$type . '-title'] = [
      'title' => $types[$type]['title'],
    ];
  }

  foreach ($handlers as $id => $handler) {
    $field_name = $handler->adminLabel(TRUE);
    $links[$type . '-edit-' . $id] = [
      'title' => t('Edit @section', ['@section' => $field_name]),
      'url' => Url::fromRoute('views_ui.form_handler', ['js' => 'nojs', 'view' => $view->storage->id(), 'display_id' => $display['id'], 'type' => $type, 'id' => $id]),
      'attributes' => ['class' => ['views-ajax-link']],
    ];
  }
  $links[$type . '-add'] = [
    'title' => t('Add new'),
    'url' => Url::fromRoute('views_ui.form_add_handler', ['js' => 'nojs', 'view' => $view->storage->id(), 'display_id' => $display['id'], 'type' => $type]),
    'attributes' => ['class' => ['views-ajax-link']],
  ];

  return $links;
}

/**
 * Returns a link to editing a certain display setting.
 */
function views_ui_view_preview_section_display_category_links(ViewExecutable $view, $type, $title) {
  $display = $view->display_handler->display;
  $links = [
    $type . '-edit' => [
      'title' => t('Edit @section', ['@section' => $title]),
      'url' => Url::fromRoute('views_ui.form_display', ['js' => 'nojs', 'view' => $view->storage->id(), 'display_id' => $display['id'], 'type' => $type]),
      'attributes' => ['class' => ['views-ajax-link']],
    ],
  ];

  return $links;
}

/**
 * Returns all contextual links for the main content part of the view.
 */
function views_ui_view_preview_section_rows_links(ViewExecutable $view) {
  $links = [];
  $links = array_merge($links, views_ui_view_preview_section_handler_links($view, 'filter', TRUE));
  $links = array_merge($links, views_ui_view_preview_section_handler_links($view, 'field', TRUE));
  $links = array_merge($links, views_ui_view_preview_section_handler_links($view, 'sort', TRUE));
  $links = array_merge($links, views_ui_view_preview_section_handler_links($view, 'argument', TRUE));
  $links = array_merge($links, views_ui_view_preview_section_handler_links($view, 'relationship', TRUE));

  return $links;
}

/**
 * Implements hook_views_plugins_display_alter().
 */
function views_ui_views_plugins_display_alter(&$plugins) {
  // Attach contextual links to each display plugin. The links will point to
  // paths underneath "admin/structure/views/view/{$view->id()}" (i.e., paths
  // for editing and performing other contextual actions on the view).
  foreach ($plugins as &$display) {
    $display['contextual links']['entity.view.edit_form'] = [
      'route_name' => 'entity.view.edit_form',
      'route_parameters_names' => ['view' => 'id'],
    ];
  }
}

/**
 * Implements hook_contextual_links_view_alter().
 */
function views_ui_contextual_links_view_alter(&$element, $items) {
  // Remove contextual links from being rendered, when so desired, such as
  // within a View preview.
  if (views_ui_contextual_links_suppress()) {
    $element['#links'] = [];
  }
  // Append the display ID to the Views UI edit links, so that clicking on the
  // contextual link takes you directly to the correct display tab on the edit
  // screen.
  elseif (!empty($element['#links']['entityviewedit-form'])) {
    $display_id = $items['entity.view.edit_form']['metadata']['display_id'];
    $route_parameters = $element['#links']['entityviewedit-form']['url']->getRouteParameters() + ['display_id' => $display_id];
    $element['#links']['entityviewedit-form']['url'] = Url::fromRoute('entity.view.edit_display_form', $route_parameters);
  }
}

/**
 * Sets a static variable for controlling whether contextual links are rendered.
 *
 * @see views_ui_contextual_links_view_alter()
 */
function views_ui_contextual_links_suppress($set = NULL) {
  $suppress = &drupal_static(__FUNCTION__);
  if (isset($set)) {
    $suppress = $set;
  }
  return $suppress;
}

/**
 * Increments the views_ui_contextual_links_suppress() static variable.
 *
 * When this function is added to the #pre_render of an element, and
 * 'views_ui_contextual_links_suppress_pop' is added to the #post_render of the
 * same element, then all contextual links within the element and its
 * descendants are suppressed from being rendered. This is used, for example,
 * during a View preview, when it is not desired for nodes in the Views result
 * to have contextual links.
 *
 * @see views_ui_contextual_links_suppress_pop()
 */
function views_ui_contextual_links_suppress_push() {
  views_ui_contextual_links_suppress(((int) views_ui_contextual_links_suppress()) + 1);
}

/**
 * Decrements the views_ui_contextual_links_suppress() static variable.
 *
 * @see views_ui_contextual_links_suppress_push()
 */
function views_ui_contextual_links_suppress_pop() {
  views_ui_contextual_links_suppress(((int) views_ui_contextual_links_suppress()) - 1);
}

/**
 * Implements hook_views_analyze().
 *
 * This is the basic views analysis that checks for very minimal problems.
 * There are other analysis tools in core specific sections, such as
 * node.views.inc as well.
 */
function views_ui_views_analyze(ViewExecutable $view) {
  $ret = [];
  // Check for something other than the default display:
  if (count($view->displayHandlers) < 2) {
    $ret[] = Analyzer::formatMessage(t('This view has only a default display and therefore will not be placed anywhere on your site; perhaps you want to add a page or a block display.'), 'warning');
  }
  // If a display has a path, check that it does not match an existing path
  // alias. This results in the path alias not working.
  foreach ($view->displayHandlers as $display) {
    if (empty($display)) {
      continue;
    }
    if ($display->hasPath() && $path = $display->getOption('path')) {
      $normal_path = \Drupal::service('path_alias.manager')->getPathByAlias($path);
      if ($path != $normal_path) {
        $ret[] = Analyzer::formatMessage(t('You have configured display %display with a path which is an path alias as well. This might lead to unwanted effects so better use an internal path.', ['%display' => $display->display['display_title']]), 'warning');
      }
    }
  }

  return $ret;
}

/**
 * Truncate strings to a set length and provide a '...' if they truncated.
 *
 * This is often used in the UI to ensure long strings fit.
 */
function views_ui_truncate($string, $length) {
  if (mb_strlen($string) > $length) {
    $string = mb_substr($string, 0, $length);
    $string .= '...';
  }

  return $string;
}