Allow for multiple fields to be selected (#165)

modules/islandora_iiif/src/Plugin/views/style/IIIFManifest.php

@@ -145,7 +145,8 @@ class IIIFManifest extends StylePluginBase {
    */
   protected function getTileSourceFromRow(ResultRow $row, $iiif_address, $iiif_base_id) {
     $canvases = [];
-    $viewsField = $this->view->field[$this->options['iiif_tile_field']];
+    foreach ($this->options['iiif_tile_field'] as $iiif_tile_field) {
+      $viewsField = $this->view->field[$iiif_tile_field];
       $entity = $viewsField->getEntity($row);
 
       if (isset($entity->{$viewsField->definition['field_name']})) {
@@ -186,6 +187,7 @@ class IIIFManifest extends StylePluginBase {
           ];
         }
       }
+    }
 
     return $canvases;
   }
@@ -242,8 +244,8 @@ class IIIFManifest extends StylePluginBase {
     }
 
     $form['iiif_tile_field'] = [
-      '#title' => $this->t('Tile source field'),
-      '#type' => 'select',
+      '#title' => $this->t('Tile source field(s)'),
+      '#type' => 'checkboxes',
       '#default_value' => $this->options['iiif_tile_field'],
       '#description' => $this->t("The source of image for each entity."),
       '#options' => $field_options,