From bdf99377e1b5a2771e971e4ac17bb8ba971971da Mon Sep 17 00:00:00 2001
From: Eli Zoller <5439169+elizoller@users.noreply.github.com>
Date: Wed, 17 Mar 2021 19:57:16 -0700
Subject: [PATCH] captions v2 (#826)

---
 .../islandora_audio/islandora_audio.module    |  15 ++
 .../IslandoraFileAudioFormatter.php           |  28 +++
 .../templates/islandora-file-audio.html.twig  |  28 +++
 .../islandora_video/islandora_video.module    |  15 ++
 .../IslandoraFileVideoFormatter.php           |  95 ++++++++
 .../templates/islandora-file-video.html.twig  |  27 +++
 .../IslandoraFileMediaFormatterBase.php       |  92 +++++++
 src/Plugin/Field/FieldType/MediaTrackItem.php | 224 ++++++++++++++++++
 .../Field/FieldWidget/MediaTrackWidget.php    | 173 ++++++++++++++
 9 files changed, 697 insertions(+)
 create mode 100644 modules/islandora_audio/src/Plugin/Field/FieldFormatter/IslandoraFileAudioFormatter.php
 create mode 100644 modules/islandora_audio/templates/islandora-file-audio.html.twig
 create mode 100644 modules/islandora_video/src/Plugin/Field/FieldFormatter/IslandoraFileVideoFormatter.php
 create mode 100644 modules/islandora_video/templates/islandora-file-video.html.twig
 create mode 100644 src/Plugin/Field/FieldFormatter/IslandoraFileMediaFormatterBase.php
 create mode 100644 src/Plugin/Field/FieldType/MediaTrackItem.php
 create mode 100644 src/Plugin/Field/FieldWidget/MediaTrackWidget.php

diff --git a/modules/islandora_audio/islandora_audio.module b/modules/islandora_audio/islandora_audio.module
index a5093c1b..07b93840 100644
--- a/modules/islandora_audio/islandora_audio.module
+++ b/modules/islandora_audio/islandora_audio.module
@@ -30,3 +30,18 @@ function islandora_audio_help($route_name, RouteMatchInterface $route_match) {
     default:
   }
 }
+
+/**
+ * Implements hook_theme().
+ */
+function islandora_audio_theme() {
+  return [
+    'islandora_file_audio' => [
+      'variables' => [
+        'files' => [],
+        'tracks' => NULL,
+        'attributes' => NULL,
+      ],
+    ],
+  ];
+}
diff --git a/modules/islandora_audio/src/Plugin/Field/FieldFormatter/IslandoraFileAudioFormatter.php b/modules/islandora_audio/src/Plugin/Field/FieldFormatter/IslandoraFileAudioFormatter.php
new file mode 100644
index 00000000..579da554
--- /dev/null
+++ b/modules/islandora_audio/src/Plugin/Field/FieldFormatter/IslandoraFileAudioFormatter.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace Drupal\islandora_audio\Plugin\Field\FieldFormatter;
+
+use Drupal\islandora\Plugin\Field\FieldFormatter\IslandoraFileMediaFormatterBase;
+
+/**
+ * Plugin implementation of the 'file_audio' formatter.
+ *
+ * @FieldFormatter(
+ *   id = "islandora_file_audio",
+ *   label = @Translation("Audio with Captions"),
+ *   description = @Translation("Display the file using an HTML5 audio tag."),
+ *   field_types = {
+ *     "file"
+ *   }
+ * )
+ */
+class IslandoraFileAudioFormatter extends IslandoraFileMediaFormatterBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getMediaType() {
+    return 'audio';
+  }
+
+}
diff --git a/modules/islandora_audio/templates/islandora-file-audio.html.twig b/modules/islandora_audio/templates/islandora-file-audio.html.twig
new file mode 100644
index 00000000..3c2d0a7a
--- /dev/null
+++ b/modules/islandora_audio/templates/islandora-file-audio.html.twig
@@ -0,0 +1,28 @@
+{#
+/**
+* @file
+* Default theme implementation to display the file entity as an audio tag.
+*
+* Available variables:
+* - attributes: An array of HTML attributes, intended to be added to the
+*   audio tag.
+* - files: And array of files to be added as sources for the audio tag. Each
+*   element is an array with the following elements:
+*   - file: The full file object.
+*   - source_attributes: An array of HTML attributes for to be added to the
+*     source tag.
+*
+* @ingroup themeable
+*/
+#}
+<audio {{ attributes }}>
+  {% for file in files %}
+    <source {{ file.source_attributes }} />
+    {% if tracks %}
+    {% for track in tracks %}
+      <track {{ track.track_attributes }}
+    {% endfor %}
+    {% endif %}
+  {% endfor %}
+</audio>
+
diff --git a/modules/islandora_video/islandora_video.module b/modules/islandora_video/islandora_video.module
index d45baf06..a1ef752b 100644
--- a/modules/islandora_video/islandora_video.module
+++ b/modules/islandora_video/islandora_video.module
@@ -30,3 +30,18 @@ function islandora_video_help($route_name, RouteMatchInterface $route_match) {
     default:
   }
 }
+
+/**
+ * Implements hook_theme().
+ */
+function islandora_video_theme() {
+  return [
+    'islandora_file_video' => [
+      'variables' => [
+        'files' => [],
+        'tracks' => NULL,
+        'attributes' => NULL,
+      ],
+    ],
+  ];
+}
diff --git a/modules/islandora_video/src/Plugin/Field/FieldFormatter/IslandoraFileVideoFormatter.php b/modules/islandora_video/src/Plugin/Field/FieldFormatter/IslandoraFileVideoFormatter.php
new file mode 100644
index 00000000..47fca594
--- /dev/null
+++ b/modules/islandora_video/src/Plugin/Field/FieldFormatter/IslandoraFileVideoFormatter.php
@@ -0,0 +1,95 @@
+<?php
+
+namespace Drupal\islandora_video\Plugin\Field\FieldFormatter;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\islandora\Plugin\Field\FieldFormatter\IslandoraFileMediaFormatterBase;
+
+/**
+ * Plugin implementation of the 'file_video' formatter.
+ *
+ * @FieldFormatter(
+ *   id = "islandora_file_video",
+ *   label = @Translation("Video with Captions"),
+ *   description = @Translation("Display the file using an HTML5 video tag."),
+ *   field_types = {
+ *     "file"
+ *   }
+ * )
+ */
+class IslandoraFileVideoFormatter extends IslandoraFileMediaFormatterBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getMediaType() {
+    return 'video';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultSettings() {
+    return [
+      'muted' => FALSE,
+      'width' => 640,
+      'height' => 480,
+    ] + parent::defaultSettings();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsForm(array $form, FormStateInterface $form_state) {
+    return parent::settingsForm($form, $form_state) + [
+      'muted' => [
+        '#title' => $this->t('Muted'),
+        '#type' => 'checkbox',
+        '#default_value' => $this->getSetting('muted'),
+      ],
+      'width' => [
+        '#type' => 'number',
+        '#title' => $this->t('Width'),
+        '#default_value' => $this->getSetting('width'),
+        '#size' => 5,
+        '#maxlength' => 5,
+        '#field_suffix' => $this->t('pixels'),
+        '#min' => 0,
+        '#required' => TRUE,
+      ],
+      'height' => [
+        '#type' => 'number',
+        '#title' => $this->t('Height'),
+        '#default_value' => $this->getSetting('height'),
+        '#size' => 5,
+        '#maxlength' => 5,
+        '#field_suffix' => $this->t('pixels'),
+        '#min' => 0,
+        '#required' => TRUE,
+      ],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsSummary() {
+    $summary = parent::settingsSummary();
+    $summary[] = $this->t('Muted: %muted', ['%muted' => $this->getSetting('muted') ? $this->t('yes') : $this->t('no')]);
+    $summary[] = $this->t('Size: %width x %height pixels', [
+      '%width' => $this->getSetting('width'),
+      '%height' => $this->getSetting('height'),
+    ]);
+    return $summary;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function prepareAttributes(array $additional_attributes = []) {
+    return parent::prepareAttributes(['muted'])
+      ->setAttribute('width', $this->getSetting('width'))
+      ->setAttribute('height', $this->getSetting('height'));
+  }
+
+}
diff --git a/modules/islandora_video/templates/islandora-file-video.html.twig b/modules/islandora_video/templates/islandora-file-video.html.twig
new file mode 100644
index 00000000..7c62bade
--- /dev/null
+++ b/modules/islandora_video/templates/islandora-file-video.html.twig
@@ -0,0 +1,27 @@
+{#
+/**
+* @file
+* Default theme implementation to display the file entity as a video tag.
+*
+* Available variables:
+* - attributes: An array of HTML attributes, intended to be added to the
+*   video tag.
+* - files: And array of files to be added as sources for the video tag. Each
+*   element is an array with the following elements:
+*   - file: The full file object.
+*   - source_attributes: An array of HTML attributes for to be added to the
+*     source tag.
+*
+* @ingroup themeable
+*/
+#}
+<video {{ attributes }}>
+  {% for file in files %}
+    <source {{ file.source_attributes }} />
+  {% endfor %}
+  {% if tracks %}
+    {% for track in tracks %}
+      <track {{ track.track_attributes }}
+    {% endfor %}
+  {% endif %}
+</video>
diff --git a/src/Plugin/Field/FieldFormatter/IslandoraFileMediaFormatterBase.php b/src/Plugin/Field/FieldFormatter/IslandoraFileMediaFormatterBase.php
new file mode 100644
index 00000000..9707544f
--- /dev/null
+++ b/src/Plugin/Field/FieldFormatter/IslandoraFileMediaFormatterBase.php
@@ -0,0 +1,92 @@
+<?php
+
+namespace Drupal\islandora\Plugin\Field\FieldFormatter;
+
+use Drupal\file\Plugin\Field\FieldFormatter\FileMediaFormatterBase;
+use Drupal\Core\Field\EntityReferenceFieldItemListInterface;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Cache\Cache;
+use Drupal\Core\Template\Attribute;
+
+/**
+ * Extension of FileMediaFormatterBase that enables captions.
+ */
+abstract class IslandoraFileMediaFormatterBase extends FileMediaFormatterBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function viewElements(FieldItemListInterface $items, $langcode) {
+    $elements = [];
+
+    $source_files = $this->getSourceFiles($items, $langcode);
+    $track_files = $this->getTrackFiles($items, $langcode);
+    if (!empty($source_files)) {
+      $attributes = $this->prepareAttributes();
+      foreach ($source_files as $delta => $files) {
+        $elements[$delta] = [
+          '#theme' => $this->getPluginId(),
+          '#attributes' => $attributes,
+          '#files' => $files,
+          '#tracks' => isset($track_files[$delta]) ? $track_files[$delta] : [],
+          '#cache' => ['tags' => []],
+        ];
+
+        $cache_tags = [];
+        foreach ($files as $file) {
+          $cache_tags = Cache::mergeTags($cache_tags, $file['file']->getCacheTags());
+        }
+        $elements[$delta]['#cache']['tags'] = $cache_tags;
+      }
+    }
+
+    return $elements;
+  }
+
+  /**
+   * Gets the track files with attributes.
+   *
+   * @param \Drupal\Core\Field\EntityReferenceFieldItemListInterface $items
+   *   The items.
+   * @param string $langcode
+   *   The langcode.
+   *
+   * @return array
+   *   Numerically indexed array, which again contains an associative array with
+   *   the following key/values:
+   *     - file => \Drupal\file\Entity\File
+   *     - track_attributes => \Drupal\Core\Template\Attribute
+   */
+  protected function getTrackFiles(EntityReferenceFieldItemListInterface $items, $langcode) {
+    $track_files = [];
+    $media_entity = $items->getParent()->getEntity();
+    $fields = $media_entity->getFields();
+    foreach ($fields as $key => $field) {
+      $definition = $field->getFieldDefinition();
+      if (method_exists($definition, 'get')) {
+        if ($definition->get('field_type') == 'media_track') {
+          // Extract the info for each track.
+          $entities = $field->referencedEntities();
+          $values = $field->getValue();
+          foreach ($entities as $delta => $file) {
+            $track_attributes = new Attribute();
+            $track_attributes
+              ->setAttribute('src', $file->createFileUrl())
+              ->setAttribute('srclang', $values[$delta]['srclang'])
+              ->setAttribute('label', $values[$delta]['label'])
+              ->setAttribute('kind', $values[$delta]['kind']);
+            if ($values[$delta]['default']) {
+              $track_attributes->setAttribute('default', 'default');
+            }
+            $track_files[0][] = [
+              'file' => $file,
+              'track_attributes' => $track_attributes,
+            ];
+          }
+        }
+      }
+    }
+    return $track_files;
+  }
+
+}
diff --git a/src/Plugin/Field/FieldType/MediaTrackItem.php b/src/Plugin/Field/FieldType/MediaTrackItem.php
new file mode 100644
index 00000000..d281ed21
--- /dev/null
+++ b/src/Plugin/Field/FieldType/MediaTrackItem.php
@@ -0,0 +1,224 @@
+<?php
+
+namespace Drupal\islandora\Plugin\Field\FieldType;
+
+use Drupal\Core\Field\FieldDefinitionInterface;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\StreamWrapper\StreamWrapperInterface;
+use Drupal\Core\TypedData\DataDefinition;
+use Drupal\file\Plugin\Field\FieldType\FileItem;
+
+/**
+ * Plugin implementation of the 'media_track' field type.
+ *
+ * @FieldType(
+ *   id = "media_track",
+ *   label = @Translation("Media track"),
+ *   description = @Translation("This field stores the ID of a media track file as an integer value."),
+ *   category = @Translation("Reference"),
+ *   default_widget = "media_track",
+ *   default_formatter = "file_default",
+ *   column_groups = {
+ *     "file" = {
+ *       "label" = @Translation("File"),
+ *       "columns" = {
+ *         "target_id"
+ *       },
+ *       "require_all_groups_for_translation" = TRUE
+ *     },
+ *     "label" = {
+ *       "label" = @Translation("Track label"),
+ *       "translatable" = FALSE,
+ *     },
+ *     "kind" = {
+ *       "label" = @Translation("Kind"),
+ *       "translatable" = FALSE
+ *     },
+ *     "srclang" = {
+ *       "label" = @Translation("SRC Language"),
+ *       "translatable" = FALSE
+ *     },
+ *     "default" = {
+ *       "label" = @Translation("Default"),
+ *       "translatable" = FALSE
+ *     },
+ *   },
+ *   list_class = "\Drupal\file\Plugin\Field\FieldType\FileFieldItemList",
+ *   constraints = {"ReferenceAccess" = {}, "FileValidation" = {}}
+ * )
+ */
+class MediaTrackItem extends FileItem {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultFieldSettings() {
+    $settings = [
+      'file_extensions' => 'vtt',
+      'languages' => 'installed',
+    ] + parent::defaultFieldSettings();
+
+    unset($settings['description_field']);
+    return $settings;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function schema(FieldStorageDefinitionInterface $field_definition) {
+    return [
+      'columns' => [
+        'target_id' => [
+          'description' => 'The ID of the file entity.',
+          'type' => 'int',
+          'unsigned' => TRUE,
+        ],
+        'label' => [
+          'description' => "Label of track, for the track's 'label' attribute.",
+          'type' => 'varchar',
+          'length' => 128,
+        ],
+        'kind' => [
+          'description' => "Type of track, for the track's 'kind' attribute.",
+          'type' => 'varchar',
+          'length' => 20,
+        ],
+        'srclang' => [
+          'description' => "Language of track, for the track's 'srclang' attribute.",
+          'type' => 'varchar',
+          'length' => 20,
+        ],
+        'default' => [
+          'description' => "Flag to indicate whether to use this as the default track of this kind.",
+          'type' => 'int',
+          'size' => 'tiny',
+          'unsigned' => TRUE,
+          'default' => 0,
+        ],
+      ],
+      'indexes' => [
+        'target_id' => ['target_id'],
+      ],
+      'foreign keys' => [
+        'target_id' => [
+          'table' => 'file_managed',
+          'columns' => ['target_id' => 'fid'],
+        ],
+      ],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
+    $properties = parent::propertyDefinitions($field_definition);
+
+    unset($properties['display']);
+    unset($properties['description']);
+
+    $properties['label'] = DataDefinition::create('string')
+      ->setLabel(t('Label'))
+      ->setDescription(t("Label of track, for the track's 'label' attribute."));
+
+    $properties['kind'] = DataDefinition::create('string')
+      ->setLabel(t('Track kind'))
+      ->setDescription(t("Type of track, for the track's 'kind' attribute."));
+
+    $properties['srclang'] = DataDefinition::create('string')
+      ->setLabel(t('SRC Language'))
+      ->setDescription(t("Language of track, for the track's 'srclang' attribute."));
+
+    $properties['default'] = DataDefinition::create('boolean')
+      ->setLabel(t('Default'))
+      ->setDescription(t("Flag to indicate whether to use this as the default track of this kind."));
+
+    return $properties;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function storageSettingsForm(array &$form, FormStateInterface $form_state, $has_data) {
+    $element = [];
+
+    $scheme_options = \Drupal::service('stream_wrapper_manager')->getNames(StreamWrapperInterface::WRITE_VISIBLE);
+    $element['uri_scheme'] = [
+      '#type' => 'radios',
+      '#title' => t('Upload destination'),
+      '#options' => $scheme_options,
+      '#default_value' => $this->getSetting('uri_scheme'),
+      '#description' => t('Select where the final files should be stored. Private file storage has significantly more overhead than public files, but allows restricted access to files within this field.'),
+    ];
+
+    return $element;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function fieldSettingsForm(array $form, FormStateInterface $form_state) {
+    // Get base form from FileItem.
+    $element = parent::fieldSettingsForm($form, $form_state);
+    $settings = $this->getSettings();
+
+    // Remove the description option.
+    unset($element['description_field']);
+
+    $element['languages'] = [
+      '#type' => 'radios',
+      '#title' => $this->t('List all languages'),
+      '#description' => $this->t('Allow the user to select all languages or only the currently installed languages?'),
+      '#options' => [
+        'all' => $this->t('All Languages'),
+        'installed' => $this->t('Currently Installed Languages'),
+      ],
+      '#default_value' => $settings['languages'] ?: 'installed',
+    ];
+
+    return $element;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function generateSampleValue(FieldDefinitionInterface $field_definition) {
+    // @todo This will need to generate a text file, containing a sequence of
+    // timestamps and nonsense text. Include some gap periods where nothing is
+    // displayed.
+    // See the ImageItem::generateSampleValue() for how the files are saved.
+    // The part about "Generate a max of 5 different images" is a good idea
+    // here too. We only need a WebVTT few files.
+    // See one of the text item implementation for how to generate nonsense.
+    // Pseudocode plan...
+    // $sample_file_text = 'WEBVTT'; // start of file.
+    // for ($i = 0; $ < $utterances; $i++) {
+    // $sample_file_text += \n\n
+    // $timestamp += 3-10seconds // start of display
+    // $sample_file_text += $timestamp
+    // $timestamp += 3-10seconds // end of display
+    // $sample_file_text += $timestamp
+    // $sample_file_text += randomText()
+    // }
+    // $file = file_write($sample_file_text, 'random_filename.vtt');
+    $values = [
+      'target_id' => $file->id(),
+      // Randomize the rest of these...
+      'label' => '',
+      'kind' => '',
+      'srclang' => '',
+      // Careful with this one, complex validation.
+      'default' => '',
+    ];
+    return $values;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function isDisplayed() {
+    return TRUE;
+  }
+
+}
diff --git a/src/Plugin/Field/FieldWidget/MediaTrackWidget.php b/src/Plugin/Field/FieldWidget/MediaTrackWidget.php
new file mode 100644
index 00000000..52de9f94
--- /dev/null
+++ b/src/Plugin/Field/FieldWidget/MediaTrackWidget.php
@@ -0,0 +1,173 @@
+<?php
+
+namespace Drupal\islandora\Plugin\Field\FieldWidget;
+
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Language\LanguageManager;
+use Drupal\file\Plugin\Field\FieldWidget\FileWidget;
+
+/**
+ * Plugin implementation of the 'media_track' widget.
+ *
+ * @FieldWidget(
+ *   id = "media_track",
+ *   label = @Translation("Media Track"),
+ *   field_types = {
+ *     "media_track"
+ *   }
+ * )
+ */
+class MediaTrackWidget extends FileWidget {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultSettings() {
+    return [
+      'progress_indicator' => 'throbber',
+    ] + parent::defaultSettings();
+  }
+
+  /**
+   * Overrides FileWidget::formMultipleElements().
+   *
+   * Special handling for draggable multiple widgets and 'add more' button.
+   */
+  protected function formMultipleElements(FieldItemListInterface $items, array &$form, FormStateInterface $form_state) {
+    $elements = parent::formMultipleElements($items, $form, $form_state);
+
+    $cardinality = $this->fieldDefinition->getFieldStorageDefinition()->getCardinality();
+    $file_upload_help = [
+      '#theme' => 'file_upload_help',
+      '#description' => '',
+      '#upload_validators' => $elements[0]['#upload_validators'],
+      '#cardinality' => $cardinality,
+    ];
+    if ($cardinality == 1) {
+      // If there's only one field, return it as delta 0.
+      if (empty($elements[0]['#default_value']['fids'])) {
+        $file_upload_help['#description'] = $this->getFilteredDescription();
+        $elements[0]['#description'] = \Drupal::service('renderer')->renderPlain($file_upload_help);
+      }
+    }
+    else {
+      $elements['#file_upload_description'] = $file_upload_help;
+    }
+
+    return $elements;
+  }
+
+  /**
+   * {@inheritDoc}
+   *
+   * Add the field settings so they can be used in the process method.
+   */
+  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
+    $element = parent::formElement($items, $delta, $element, $form, $form_state);
+    $element['#field_settings'] = $this->getFieldSettings();
+
+    return $element;
+  }
+
+  /**
+   * Form API callback: Processes a media_track field element.
+   *
+   * Expands the media_track type to include the alt and title fields.
+   *
+   * This method is assigned as a #process callback in formElement() method.
+   */
+  public static function process($element, FormStateInterface $form_state, $form) {
+    $item = $element['#value'];
+    $item['fids'] = $element['fids']['#value'];
+
+    $element['label'] = [
+      '#title' => t('Label'),
+      '#type' => 'textfield',
+      '#default_value' => isset($item['label']) ? $item['label'] : '',
+      '#description' => t('Label for the track file.'),
+      '#maxlength' => 128,
+      '#access' => (bool) $item['fids'],
+    ];
+    $element['kind'] = [
+      '#title' => t('Kind'),
+      '#type' => 'select',
+      '#description' => t('The kind of media track.'),
+      '#options' => [
+        'subtitles' => t('Subtitles'),
+        'captions' => t('Captions'),
+        'descriptions' => t('Descriptions'),
+        'chapters' => t('Chapters'),
+        'metadata' => t('Metadata'),
+      ],
+      '#default_value' => isset($item['kind']) ? $item['kind'] : '',
+      '#access' => (bool) $item['fids'],
+    ];
+
+    $srclang_options = [];
+    if ($element['#field_settings']['languages'] == 'all') {
+      // Need to list all languages.
+      $languages = LanguageManager::getStandardLanguageList();
+      foreach ($languages as $key => $language) {
+        if ($language[0] == $language[1]) {
+          // Both the native language name and the English language name are
+          // the same, so only show one of them.
+          $srclang_options[$key] = $language[0];
+        }
+        else {
+          // The native language name and English language name are different
+          // so show both of them.
+          $srclang_options[$key] = t('@lang0 / @lang1', [
+            '@lang0' => $language[0],
+            '@lang1' => $language[1],
+          ]);
+        }
+      }
+    }
+    else {
+      // Only list the installed languages.
+      $languages = \Drupal::languageManager()->getLanguages();
+      foreach ($languages as $key => $language) {
+        $srclang_options[$key] = $language->getName();
+      }
+    }
+
+    $element['srclang'] = [
+      '#title' => t('SRC Language'),
+      '#description' => t('Choose from one of the installed languages.'),
+      '#type' => 'select',
+      '#options' => $srclang_options,
+      '#default_value' => isset($item['srclang']) ? $item['srclang'] : '',
+      '#maxlength' => 20,
+      '#access' => (bool) $item['fids'],
+      '#element_validate' => [[get_called_class(), 'validateRequiredFields']],
+    ];
+    // @see https://www.w3.org/TR/html/semantics-embedded-content.html#elementdef-track
+    $element['default'] = [
+      '#type' => 'checkbox',
+      '#title' => t('Default track'),
+      '#default_value' => isset($item['default']) ? $item['default'] : '',
+      '#description' => t('Use this as the default track of this kind.'),
+      '#access' => (bool) $item['fids'],
+    ];
+
+    return parent::process($element, $form_state, $form);
+  }
+
+  /**
+   * Validate callback for kind/srclang/label/default.
+   *
+   * This is separated in a validate function instead of a #required flag to
+   * avoid being validated on the process callback.
+   * The 'default' track has complex validation, see HTML5.2 for details.
+   */
+  public static function validateRequiredFields($element, FormStateInterface $form_state) {
+    // Only do validation if the function is triggered from other places than
+    // the image process form.
+    $triggering_element = $form_state->getTriggeringElement();
+    if (!empty($triggering_element['#submit']) && in_array('file_managed_file_submit', $triggering_element['#submit'], TRUE)) {
+      $form_state->setLimitValidationErrors([]);
+    }
+  }
+
+}