Issue #3155280 by e0ipso: Improve usability in the toolbar integration

entity_reference_preview.module

@@ -35,17 +35,41 @@ function entity_reference_preview_toolbar_alter(&$items) {
   if (!$enabled) {
     return;
   }
-  $container = \Drupal::getContainer();
-  $request = $container
+  $request = \Drupal::getContainer()
     ->get('request_stack')
     ->getCurrentRequest();
-  $is_previewing = $request
+  $active_detector = $request
     ->attributes
-    ->get(PreviewNegotiationSubscriber::IS_PREVIEWING);
-  $current_status = $is_previewing ? 'previewing' : 'stopped';
+    ->get(PreviewNegotiationSubscriber::ACTIVE_DETECTOR);
+  $current_status = $active_detector ? 'previewing' : 'stopped';
 
   $has_permission = \Drupal::currentUser()
     ->hasPermission('request entity_reference_preview preview');
+
+  $message = $active_detector === 'rendered_entity'
+    ? 'The preview state is active because you are seeing the latest version of an entity under moderation.'
+    : 'The preview state is triggered by an external action.';
+  $controls = [
+    '#markup' => new TranslatableMarkup('<a href="#" title="' . $message . '">?</a>'),
+  ];
+  if (!$active_detector || $active_detector === 'cookie') {
+    $controls = [
+      '#type' => 'link',
+      '#title' => new TranslatableMarkup('Change'),
+      '#url' => Url::fromRoute('entity_reference_preview.controls'),
+      '#access' => $has_permission,
+    ];
+    try {
+      $controls['#url']
+        ->setRouteParameter(
+          'destination',
+          Url::createFromRequest($request)->toString()
+        );
+    }
+    catch (ResourceNotFoundException $exception) {
+      // If the request is 404 we can ignore it.
+    }
+  }
   $items['preview_controls'] = [
     '#type' => 'toolbar_item',
     'tab' => [
@@ -55,7 +79,7 @@ function entity_reference_preview_toolbar_alter(&$items) {
       '#attributes' => [
         'class' => [
           'toolbar-icon',
-          'preview--' . ($is_previewing ? 'started' : 'stopped'),
+          'preview--' . ($active_detector ? 'started' : 'stopped'),
         ],
       ],
     ],
@@ -75,12 +99,7 @@ function entity_reference_preview_toolbar_alter(&$items) {
           ],
         ],
       ],
-      'link' => [
-        '#type' => 'link',
-        '#title' => new TranslatableMarkup('Change'),
-        '#url' => Url::fromRoute('entity_reference_preview.controls'),
-        '#access' => $has_permission,
-      ],
+      'link' => $controls,
     ],
     '#attached' => [
       'library' => [
@@ -91,16 +110,6 @@ function entity_reference_preview_toolbar_alter(&$items) {
       'id' => 'entity-reference-preview-controls-tab',
     ],
   ];
-  try {
-    $items['preview_controls']['tray']['link']['#url']
-      ->setRouteParameter(
-        'destination',
-        Url::createFromRequest($request)->toString()
-      );
-  }
-  catch (ResourceNotFoundException $exception) {
-    // If the request is 404 we can ignore it.
-  }
 }
 
 /**

src/Events/PreviewNegotiationSubscriber.php

@@ -14,6 +14,8 @@ final class PreviewNegotiationSubscriber implements EventSubscriberInterface {
 
   const IS_PREVIEWING = '_is_previewing';
 
+  const ACTIVE_DETECTOR = '_active_detector';
+
   /**
    * The preview detector.
    *
@@ -52,8 +54,9 @@ final class PreviewNegotiationSubscriber implements EventSubscriberInterface {
   public function setPreview(GetResponseEvent $event): void {
     $request = $event->getRequest();
     // Set the global request state in the request object for others to read.
-    $is_previewing = $this->previewDetector->isPreviewing($request);
-    $request->attributes->set(static::IS_PREVIEWING, $is_previewing);
+    $active_detector = $this->previewDetector->activeDetector($request);
+    $request->attributes->set(static::IS_PREVIEWING, (bool) $active_detector);
+    $request->attributes->set(static::ACTIVE_DETECTOR, $active_detector);
   }
 
 }

src/PreviewDetectorPluginManager.php

@@ -54,16 +54,36 @@ class PreviewDetectorPluginManager extends DefaultPluginManager implements Fallb
    *   TRUE if the request is for a preview.
    */
   public function isPreviewing(Request $request, array $configuration = []): bool {
+    return (bool) $this->activeDetector($request, $configuration);
+  }
+
+  /**
+   * Gets the active detector ID, if any, for the current request.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The global request object.
+   * @param array $configuration
+   *   The configuration for the preview detectors.
+   *
+   * @return string
+   *   The plugin ID that is triggering the preview state.
+   */
+  public function activeDetector(Request $request, array $configuration = []): ?string {
     $instances = array_map(function (array $definition) use ($configuration) {
       return $this->createInstance($definition['id'], $configuration);
     }, $this->getDefinitions());
     // Return true if any of the plugins is true.
     return array_reduce(
       $instances,
-      function (bool $detected, PreviewDetectorInterface $detector) use ($request) {
-        return $detected || $detector->isPreviewing($request);
+      static function ($detected, PreviewDetectorInterface $detector) use ($request) {
+        if ($detected) {
+          return $detected;
+        }
+        return $detector->isPreviewing($request)
+          ? $detector->getPluginId()
+          : NULL;
       },
-      FALSE
+      NULL
     );
   }
 

tests/src/Unit/Events/PreviewNegotiationSubscriberTest.php

@@ -38,7 +38,7 @@ class PreviewNegotiationSubscriberTest extends UnitTestCase {
    *   The data.
    */
   public function dataProviderSetPreview() {
-    return [[TRUE], [FALSE]];
+    return [['foo'], [NULL]];
   }
 
   /**
@@ -55,10 +55,13 @@ class PreviewNegotiationSubscriberTest extends UnitTestCase {
    * @covers ::setPreview
    * @dataProvider dataProviderSetPreview
    */
-  public function testSetPreview($is_previewing) {
+  public function testSetPreview($active_detector) {
     $this->previewDetector
       ->isPreviewing(Argument::type(Request::class))
-      ->willReturn($is_previewing)
+      ->shouldBecalled($this->once());
+    $this->previewDetector
+      ->activeDetector(Argument::type(Request::class))
+      ->willReturn($active_detector)
       ->shouldBecalled($this->once());
     $request = new Request();
     $event = $this->prophesize(GetResponseEvent::class);
@@ -66,7 +69,10 @@ class PreviewNegotiationSubscriberTest extends UnitTestCase {
     $this->eventSubscriber->setPreview($event->reveal());
     $flag = $request->attributes
       ->get(PreviewNegotiationSubscriber::IS_PREVIEWING);
-    $this->assertSame($is_previewing, $flag);
+    $this->assertSame((bool) $active_detector, $flag);
+    $actual = $request->attributes
+      ->get(PreviewNegotiationSubscriber::ACTIVE_DETECTOR);
+    $this->assertSame($active_detector, $actual);
   }
 
 }