Roughly modularize document rendering in Files

Summary:
Ref T13105. This change begins modularizing document rendering. I'm starting in Files since it's the use case with the smallest amount of complexity.

Currently, we hard-coding the inline rendering for images, audio, and video. Instead, use the modular engine pattern to make rendering flexible and extensible.

There aren't any options for switching modes yet and none of the renderers do anything fancy. This API is also probably very unstable.

Test Plan: Viewwed images, audio, video, and other files. Saw reasonable renderings, with "nothing can render this" for any other file type.

Maniphest Tasks: T13105

Differential Revision: https://secure.phabricator.com/D19237

resources/celerity/map.php

@@ -9,7 +9,7 @@ return array(
   'names' => array(
     'conpherence.pkg.css' => 'e68cf1fa',
     'conpherence.pkg.js' => '15191c65',
-    'core.pkg.css' => 'c218ed53',
+    'core.pkg.css' => '6a8ba174',
     'core.pkg.js' => '8581cd02',
     'differential.pkg.css' => '113e692c',
     'differential.pkg.js' => 'f6d809c0',
@@ -168,7 +168,7 @@ return array(
     'rsrc/css/phui/phui-object-box.css' => '9cff003c',
     'rsrc/css/phui/phui-pager.css' => 'edcbc226',
     'rsrc/css/phui/phui-pinboard-view.css' => '2495140e',
-    'rsrc/css/phui/phui-property-list-view.css' => '2dc7993f',
+    'rsrc/css/phui/phui-property-list-view.css' => '79fc3a02',
     'rsrc/css/phui/phui-remarkup-preview.css' => '54a34863',
     'rsrc/css/phui/phui-segment-bar-view.css' => 'b1d1b892',
     'rsrc/css/phui/phui-spacing.css' => '042804d6',
@@ -848,7 +848,7 @@ return array(
     'phui-oi-simple-ui-css' => 'a8beebea',
     'phui-pager-css' => 'edcbc226',
     'phui-pinboard-view-css' => '2495140e',
-    'phui-property-list-view-css' => '2dc7993f',
+    'phui-property-list-view-css' => '79fc3a02',
     'phui-remarkup-preview-css' => '54a34863',
     'phui-segment-bar-view-css' => 'b1d1b892',
     'phui-spacing-css' => '042804d6',

src/__phutil_library_map__.php

@@ -2066,6 +2066,7 @@ phutil_register_library_map(array(
     'PhabricatorAsanaConfigOptions' => 'applications/doorkeeper/option/PhabricatorAsanaConfigOptions.php',
     'PhabricatorAsanaSubtaskHasObjectEdgeType' => 'applications/doorkeeper/edge/PhabricatorAsanaSubtaskHasObjectEdgeType.php',
     'PhabricatorAsanaTaskHasObjectEdgeType' => 'applications/doorkeeper/edge/PhabricatorAsanaTaskHasObjectEdgeType.php',
+    'PhabricatorAudioDocumentEngine' => 'applications/files/document/PhabricatorAudioDocumentEngine.php',
     'PhabricatorAuditActionConstants' => 'applications/audit/constants/PhabricatorAuditActionConstants.php',
     'PhabricatorAuditApplication' => 'applications/audit/application/PhabricatorAuditApplication.php',
     'PhabricatorAuditCommentEditor' => 'applications/audit/editor/PhabricatorAuditCommentEditor.php',
@@ -2808,6 +2809,8 @@ phutil_register_library_map(array(
     'PhabricatorDividerEditField' => 'applications/transactions/editfield/PhabricatorDividerEditField.php',
     'PhabricatorDividerProfileMenuItem' => 'applications/search/menuitem/PhabricatorDividerProfileMenuItem.php',
     'PhabricatorDivinerApplication' => 'applications/diviner/application/PhabricatorDivinerApplication.php',
+    'PhabricatorDocumentEngine' => 'applications/files/document/PhabricatorDocumentEngine.php',
+    'PhabricatorDocumentRef' => 'applications/files/document/PhabricatorDocumentRef.php',
     'PhabricatorDoorkeeperApplication' => 'applications/doorkeeper/application/PhabricatorDoorkeeperApplication.php',
     'PhabricatorDraft' => 'applications/draft/storage/PhabricatorDraft.php',
     'PhabricatorDraftDAO' => 'applications/draft/storage/PhabricatorDraftDAO.php',
@@ -3155,6 +3158,7 @@ phutil_register_library_map(array(
     'PhabricatorIconSet' => 'applications/files/iconset/PhabricatorIconSet.php',
     'PhabricatorIconSetEditField' => 'applications/transactions/editfield/PhabricatorIconSetEditField.php',
     'PhabricatorIconSetIcon' => 'applications/files/iconset/PhabricatorIconSetIcon.php',
+    'PhabricatorImageDocumentEngine' => 'applications/files/document/PhabricatorImageDocumentEngine.php',
     'PhabricatorImageMacroRemarkupRule' => 'applications/macro/markup/PhabricatorImageMacroRemarkupRule.php',
     'PhabricatorImageRemarkupRule' => 'applications/files/markup/PhabricatorImageRemarkupRule.php',
     'PhabricatorImageTransformer' => 'applications/files/PhabricatorImageTransformer.php',
@@ -4481,7 +4485,9 @@ phutil_register_library_map(array(
     'PhabricatorVCSResponse' => 'applications/repository/response/PhabricatorVCSResponse.php',
     'PhabricatorVersionedDraft' => 'applications/draft/storage/PhabricatorVersionedDraft.php',
     'PhabricatorVeryWowEnglishTranslation' => 'infrastructure/internationalization/translation/PhabricatorVeryWowEnglishTranslation.php',
+    'PhabricatorVideoDocumentEngine' => 'applications/files/document/PhabricatorVideoDocumentEngine.php',
     'PhabricatorViewerDatasource' => 'applications/people/typeahead/PhabricatorViewerDatasource.php',
+    'PhabricatorVoidDocumentEngine' => 'applications/files/document/PhabricatorVoidDocumentEngine.php',
     'PhabricatorWatcherHasObjectEdgeType' => 'applications/transactions/edges/PhabricatorWatcherHasObjectEdgeType.php',
     'PhabricatorWebContentSource' => 'infrastructure/contentsource/PhabricatorWebContentSource.php',
     'PhabricatorWebServerSetupCheck' => 'applications/config/check/PhabricatorWebServerSetupCheck.php',
@@ -7497,6 +7503,7 @@ phutil_register_library_map(array(
     'PhabricatorAsanaConfigOptions' => 'PhabricatorApplicationConfigOptions',
     'PhabricatorAsanaSubtaskHasObjectEdgeType' => 'PhabricatorEdgeType',
     'PhabricatorAsanaTaskHasObjectEdgeType' => 'PhabricatorEdgeType',
+    'PhabricatorAudioDocumentEngine' => 'PhabricatorDocumentEngine',
     'PhabricatorAuditActionConstants' => 'Phobject',
     'PhabricatorAuditApplication' => 'PhabricatorApplication',
     'PhabricatorAuditCommentEditor' => 'PhabricatorEditor',
@@ -8362,6 +8369,8 @@ phutil_register_library_map(array(
     'PhabricatorDividerEditField' => 'PhabricatorEditField',
     'PhabricatorDividerProfileMenuItem' => 'PhabricatorProfileMenuItem',
     'PhabricatorDivinerApplication' => 'PhabricatorApplication',
+    'PhabricatorDocumentEngine' => 'Phobject',
+    'PhabricatorDocumentRef' => 'Phobject',
     'PhabricatorDoorkeeperApplication' => 'PhabricatorApplication',
     'PhabricatorDraft' => 'PhabricatorDraftDAO',
     'PhabricatorDraftDAO' => 'PhabricatorLiskDAO',
@@ -8756,6 +8765,7 @@ phutil_register_library_map(array(
     'PhabricatorIconSet' => 'Phobject',
     'PhabricatorIconSetEditField' => 'PhabricatorEditField',
     'PhabricatorIconSetIcon' => 'Phobject',
+    'PhabricatorImageDocumentEngine' => 'PhabricatorDocumentEngine',
     'PhabricatorImageMacroRemarkupRule' => 'PhutilRemarkupRule',
     'PhabricatorImageRemarkupRule' => 'PhutilRemarkupRule',
     'PhabricatorImageTransformer' => 'Phobject',
@@ -10330,7 +10340,9 @@ phutil_register_library_map(array(
     'PhabricatorVCSResponse' => 'AphrontResponse',
     'PhabricatorVersionedDraft' => 'PhabricatorDraftDAO',
     'PhabricatorVeryWowEnglishTranslation' => 'PhutilTranslation',
+    'PhabricatorVideoDocumentEngine' => 'PhabricatorDocumentEngine',
     'PhabricatorViewerDatasource' => 'PhabricatorTypeaheadDatasource',
+    'PhabricatorVoidDocumentEngine' => 'PhabricatorDocumentEngine',
     'PhabricatorWatcherHasObjectEdgeType' => 'PhabricatorEdgeType',
     'PhabricatorWebContentSource' => 'PhabricatorContentSource',
     'PhabricatorWebServerSetupCheck' => 'PhabricatorSetupCheck',

src/applications/files/controller/PhabricatorFileInfoController.php

@@ -23,6 +23,7 @@ final class PhabricatorFileInfoController extends PhabricatorFileController {
       }
       return id(new AphrontRedirectResponse())->setURI($file->getInfoURI());
     }
+
     $file = id(new PhabricatorFileQuery())
       ->setViewer($viewer)
       ->withIDs(array($id))
@@ -62,31 +63,34 @@ final class PhabricatorFileInfoController extends PhabricatorFileController {
     $timeline = $this->buildTransactionView($file);
     $crumbs = $this->buildApplicationCrumbs();
     $crumbs->addTextCrumb(
-      'F'.$file->getID(),
-      $this->getApplicationURI("/info/{$phid}/"));
+      $file->getMonogram(),
+      $file->getInfoURI());
     $crumbs->setBorder(true);
 
     $object_box = id(new PHUIObjectBoxView())
-      ->setHeaderText(pht('File'))
+      ->setHeaderText(pht('File Metadata'))
       ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY);
 
     $this->buildPropertyViews($object_box, $file);
     $title = $file->getName();
 
+    $file_content = $this->newFileContent($file);
+
     $view = id(new PHUITwoColumnView())
       ->setHeader($header)
       ->setCurtain($curtain)
-      ->setMainColumn(array(
-        $object_box,
-        $timeline,
-      ));
+      ->setMainColumn(
+        array(
+          $object_box,
+          $file_content,
+          $timeline,
+        ));
 
     return $this->newPage()
       ->setTitle($title)
       ->setCrumbs($crumbs)
       ->setPageObjectPHIDs(array($file->getPHID()))
       ->appendChild($view);
-
   }
 
   private function buildTransactionView(PhabricatorFile $file) {
@@ -325,61 +329,6 @@ final class PhabricatorFileInfoController extends PhabricatorFileController {
         $viewer->renderHandleList($phids));
     }
 
-    if ($file->isViewableImage()) {
-      $image = phutil_tag(
-        'img',
-        array(
-          'src' => $file->getViewURI(),
-          'class' => 'phui-property-list-image',
-        ));
-
-      $linked_image = phutil_tag(
-        'a',
-        array(
-          'href' => $file->getViewURI(),
-        ),
-        $image);
-
-      $media = id(new PHUIPropertyListView())
-        ->addImageContent($linked_image);
-
-      $box->addPropertyList($media);
-    } else if ($file->isVideo()) {
-      $video = phutil_tag(
-        'video',
-        array(
-          'controls' => 'controls',
-          'class' => 'phui-property-list-video',
-        ),
-        phutil_tag(
-          'source',
-          array(
-            'src' => $file->getViewURI(),
-            'type' => $file->getMimeType(),
-          )));
-      $media = id(new PHUIPropertyListView())
-        ->addImageContent($video);
-
-      $box->addPropertyList($media);
-    } else if ($file->isAudio()) {
-      $audio = phutil_tag(
-        'audio',
-        array(
-          'controls' => 'controls',
-          'class' => 'phui-property-list-audio',
-        ),
-        phutil_tag(
-          'source',
-          array(
-            'src' => $file->getViewURI(),
-            'type' => $file->getMimeType(),
-          )));
-      $media = id(new PHUIPropertyListView())
-        ->addImageContent($audio);
-
-      $box->addPropertyList($media);
-    }
-
     $engine = $this->loadStorageEngine($file);
     if ($engine) {
       if ($engine->isChunkEngine()) {
@@ -453,5 +402,52 @@ final class PhabricatorFileInfoController extends PhabricatorFileController {
     return $engine;
   }
 
+  private function newFileContent(PhabricatorFile $file) {
+    $viewer = $this->getViewer();
+    $engines = PhabricatorDocumentEngine::getAllEngines();
+
+    $ref = id(new PhabricatorDocumentRef())
+      ->setFile($file);
+
+    foreach ($engines as $key => $engine) {
+      $engine = id(clone $engine)
+        ->setViewer($viewer);
+
+      if (!$engine->canRenderDocument($ref)) {
+        unset($engines[$key]);
+        continue;
+      }
+
+      $engines[$key] = $engine;
+    }
+
+    if (!$engines) {
+      throw new Exception(pht('No engine can render this document.'));
+    }
+
+    $vectors = array();
+    foreach ($engines as $key => $usable_engine) {
+      $vectors[$key] = $usable_engine->newSortVector($ref);
+    }
+    $vectors = msortv($vectors, 'getSelf');
+
+    $engine = $engines[head_key($vectors)];
+
+    $content = $engine->newDocument($ref);
+    if (!$content) {
+      return null;
+    }
+
+    $icon = $engine->newDocumentIcon($ref);
+
+    $header = id(new PHUIHeaderView())
+      ->setHeaderIcon($icon)
+      ->setHeader($ref->getName());
+
+    return id(new PHUIObjectBoxView())
+      ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
+      ->setHeader($header)
+      ->appendChild($content);
+  }
 
 }

src/applications/files/document/PhabricatorAudioDocumentEngine.php

@@ -0,0 +1,61 @@
+<?php
+
+final class PhabricatorAudioDocumentEngine
+  extends PhabricatorDocumentEngine {
+
+  const ENGINEKEY = 'audio';
+
+  protected function getDocumentIconIcon(PhabricatorDocumentRef $ref) {
+    return 'fa-file-sound-o';
+  }
+
+  protected function canRenderDocumentType(PhabricatorDocumentRef $ref) {
+    $file = $ref->getFile();
+    if ($file) {
+      return $file->isAudio();
+    }
+
+    $viewable_types = PhabricatorEnv::getEnvConfig('files.viewable-mime-types');
+    $viewable_types = array_keys($viewable_types);
+
+    $audio_types = PhabricatorEnv::getEnvConfig('files.audio-mime-types');
+    $audio_types = array_keys($audio_types);
+
+    return
+      $ref->hasAnyMimeType($viewable_types) &&
+      $ref->hasAnyMimeType($audio_types);
+  }
+
+  protected function newDocumentContent(PhabricatorDocumentRef $ref) {
+    $file = $ref->getFile();
+    if ($file) {
+      $source_uri = $file->getViewURI();
+    } else {
+      throw new PhutilMethodNotImplementedException();
+    }
+
+    $mime_type = $ref->getMimeType();
+
+    $audio = phutil_tag(
+      'audio',
+      array(
+        'controls' => 'controls',
+      ),
+      phutil_tag(
+        'source',
+        array(
+          'src' => $source_uri,
+          'type' => $mime_type,
+        )));
+
+    $container = phutil_tag(
+      'div',
+      array(
+        'class' => 'document-engine-audio',
+      ),
+      $audio);
+
+    return $container;
+  }
+
+}

src/applications/files/document/PhabricatorDocumentEngine.php

@@ -0,0 +1,62 @@
+<?php
+
+abstract class PhabricatorDocumentEngine
+  extends Phobject {
+
+  private $viewer;
+
+  final public function setViewer(PhabricatorUser $viewer) {
+    $this->viewer = $viewer;
+    return $this;
+  }
+
+  final public function getViewer() {
+    return $this->viewer;
+  }
+
+  final public function canRenderDocument(PhabricatorDocumentRef $ref) {
+    return $this->canRenderDocumentType($ref);
+  }
+
+  abstract protected function canRenderDocumentType(
+    PhabricatorDocumentRef $ref);
+
+  final public function newDocument(PhabricatorDocumentRef $ref) {
+    return $this->newDocumentContent($ref);
+  }
+
+  final public function newDocumentIcon(PhabricatorDocumentRef $ref) {
+    return id(new PHUIIconView())
+      ->setIcon($this->getDocumentIconIcon($ref));
+  }
+
+  abstract protected function newDocumentContent(
+    PhabricatorDocumentRef $ref);
+
+  protected function getDocumentIconIcon(PhabricatorDocumentRef $ref) {
+    return 'fa-file-o';
+  }
+
+  final public function getDocumentEngineKey() {
+    return $this->getPhobjectClassConstant('ENGINEKEY');
+  }
+
+  final public static function getAllEngines() {
+    return id(new PhutilClassMapQuery())
+      ->setAncestorClass(__CLASS__)
+      ->setUniqueMethod('getDocumentEngineKey')
+      ->execute();
+  }
+
+  final public function newSortVector(PhabricatorDocumentRef $ref) {
+    $content_score = $this->getContentScore($ref);
+
+    return id(new PhutilSortVector())
+      ->addInt(-$content_score);
+  }
+
+  protected function getContentScore() {
+    return 2000;
+  }
+
+}

src/applications/files/document/PhabricatorDocumentRef.php

@@ -0,0 +1,93 @@
+<?php
+
+final class PhabricatorDocumentRef
+  extends Phobject {
+
+  private $name;
+  private $mimeType;
+  private $file;
+  private $byteLength;
+
+  public function setFile(PhabricatorFile $file) {
+    $this->file = $file;
+    return $this;
+  }
+
+  public function getFile() {
+    return $this->file;
+  }
+
+  public function setMimeType($mime_type) {
+    $this->mimeType = $mime_type;
+    return $this;
+  }
+
+  public function getMimeType() {
+    if ($this->mimeType !== null) {
+      return $this->mimeType;
+    }
+
+    if ($this->file) {
+      return $this->file->getMimeType();
+    }
+
+    return null;
+  }
+
+  public function setName($name) {
+    $this->name = $name;
+    return $this;
+  }
+
+  public function getName() {
+    if ($this->name !== null) {
+      return $this->name;
+    }
+
+    if ($this->file) {
+      return $this->file->getName();
+    }
+
+    return null;
+  }
+
+  public function setByteLength($length) {
+    $this->byteLength = $length;
+    return $this;
+  }
+
+  public function getLength() {
+    if ($this->byteLength !== null) {
+      return $this->byteLength;
+    }
+
+    if ($this->file) {
+      return (int)$this->file->getByteSize();
+    }
+
+    return null;
+  }
+
+  public function hasAnyMimeType(array $candidate_types) {
+    $mime_full = $this->getMimeType();
+    $mime_parts = explode(';', $mime_full);
+
+    $mime_type = head($mime_parts);
+    $mime_type = $this->normalizeMimeType($mime_type);
+
+    foreach ($candidate_types as $candidate_type) {
+      if ($this->normalizeMimeType($candidate_type) === $mime_type) {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
+  private function normalizeMimeType($mime_type) {
+    $mime_type = trim($mime_type);
+    $mime_type = phutil_utf8_strtolower($mime_type);
+    return $mime_type;
+  }
+
+}

src/applications/files/document/PhabricatorImageDocumentEngine.php

@@ -0,0 +1,63 @@
+<?php
+
+final class PhabricatorImageDocumentEngine
+  extends PhabricatorDocumentEngine {
+
+  const ENGINEKEY = 'image';
+
+  protected function getDocumentIconIcon(PhabricatorDocumentRef $ref) {
+    return 'fa-file-image-o';
+  }
+
+  protected function canRenderDocumentType(PhabricatorDocumentRef $ref) {
+    $file = $ref->getFile();
+    if ($file) {
+      return $file->isViewableImage();
+    }
+
+    $viewable_types = PhabricatorEnv::getEnvConfig('files.viewable-mime-types');
+    $viewable_types = array_keys($viewable_types);
+
+    $image_types = PhabricatorEnv::getEnvConfig('files.image-mime-types');
+    $image_types = array_keys($image_types);
+
+    return
+      $ref->hasAnyMimeType($viewable_types) &&
+      $ref->hasAnyMimeType($image_types);
+  }
+
+  protected function newDocumentContent(PhabricatorDocumentRef $ref) {
+    $file = $ref->getFile();
+    if ($file) {
+      $source_uri = $file->getViewURI();
+    } else {
+      // We could use a "data:" URI here. It's not yet clear if or when we'll
+      // have a ref but no backing file.
+      throw new PhutilMethodNotImplementedException();
+    }
+
+    $image = phutil_tag(
+      'img',
+      array(
+        'src' => $source_uri,
+      ));
+
+    $linked_image = phutil_tag(
+      'a',
+      array(
+        'href' => $source_uri,
+        'rel' => 'noreferrer',
+      ),
+      $image);
+
+    $container = phutil_tag(
+      'div',
+      array(
+        'class' => 'document-engine-image',
+      ),
+      $linked_image);
+
+    return $container;
+  }
+
+}

src/applications/files/document/PhabricatorVideoDocumentEngine.php

@@ -0,0 +1,61 @@
+<?php
+
+final class PhabricatorVideoDocumentEngine
+  extends PhabricatorDocumentEngine {
+
+  const ENGINEKEY = 'video';
+
+  protected function getDocumentIconIcon(PhabricatorDocumentRef $ref) {
+    return 'fa-film';
+  }
+
+  protected function canRenderDocumentType(PhabricatorDocumentRef $ref) {
+    $file = $ref->getFile();
+    if ($file) {
+      return $file->isVideo();
+    }
+
+    $viewable_types = PhabricatorEnv::getEnvConfig('files.viewable-mime-types');
+    $viewable_types = array_keys($viewable_types);
+
+    $video_types = PhabricatorEnv::getEnvConfig('files.video-mime-types');
+    $video_types = array_keys($video_types);
+
+    return
+      $ref->hasAnyMimeType($viewable_types) &&
+      $ref->hasAnyMimeType($video_types);
+  }
+
+  protected function newDocumentContent(PhabricatorDocumentRef $ref) {
+    $file = $ref->getFile();
+    if ($file) {
+      $source_uri = $file->getViewURI();
+    } else {
+      throw new PhutilMethodNotImplementedException();
+    }
+
+    $mime_type = $ref->getMimeType();
+
+    $video = phutil_tag(
+      'video',
+      array(
+        'controls' => 'controls',
+      ),
+      phutil_tag(
+        'source',
+        array(
+          'src' => $source_uri,
+          'type' => $mime_type,
+        )));
+
+    $container = phutil_tag(
+      'div',
+      array(
+        'class' => 'document-engine-video',
+      ),
+      $video);
+
+    return $container;
+  }
+
+}

src/applications/files/document/PhabricatorVoidDocumentEngine.php

@@ -0,0 +1,34 @@
+<?php
+
+final class PhabricatorVoidDocumentEngine
+  extends PhabricatorDocumentEngine {
+
+  const ENGINEKEY = 'void';
+
+  protected function getDocumentIconIcon(PhabricatorDocumentRef $ref) {
+    return 'fa-file';
+  }
+
+  protected function getContentScore() {
+    return 1000;
+  }
+
+  protected function canRenderDocumentType(PhabricatorDocumentRef $ref) {
+    return true;
+  }
+
+  protected function newDocumentContent(PhabricatorDocumentRef $ref) {
+    $message = pht(
+      'No document engine can render the contents of this file.');
+
+    $container = phutil_tag(
+      'div',
+      array(
+        'class' => 'document-engine-message',
+      ),
+      $message);
+
+    return $container;
+  }
+
+}

src/view/phui/PHUIHeaderView.php

@@ -307,9 +307,14 @@ final class PHUIHeaderView extends AphrontTagView {
 
     $icon = null;
     if ($this->headerIcon) {
-      $icon = id(new PHUIIconView())
-        ->setIcon($this->headerIcon)
-        ->addClass('phui-header-icon');
+      if ($this->headerIcon instanceof PHUIIconView) {
+        $icon = id(clone $this->headerIcon)
+          ->addClass('phui-header-icon');
+      } else {
+        $icon = id(new PHUIIconView())
+          ->setIcon($this->headerIcon)
+          ->addClass('phui-header-icon');
+      }
     }
 
     $header_content = $this->header;

webroot/rsrc/css/phui/phui-property-list-view.css

@@ -149,24 +149,6 @@ div.phui-property-list-stacked .phui-property-list-properties
 }
 
 
-.phui-property-list-image {
-  margin: auto;
-  max-width: 95%;
-}
-
-.phui-property-list-audio {
-  display: block;
-  margin: 16px auto;
-  width: 50%;
-  min-width: 240px;
-}
-
-.phui-property-list-video {
-  display: block;
-  margin: 0 auto;
-  max-width: 95%;
-}
-
 /* When tags appear in property lists, give them a little more vertical
    spacing. */
 .phui-property-list-value .phui-tag-view {
@@ -220,3 +202,32 @@ div.phui-property-list-stacked .phui-property-list-properties
   border-right: 1px solid {$lightblueborder};
   border-bottom: 1px solid {$blueborder};
 }
+
+
+.document-engine-image img {
+  margin: 20px auto;
+  background: url('/rsrc/image/checker_light.png');
+}
+
+.device-desktop .document-engine-image img:hover {
+  background: url('/rsrc/image/checker_dark.png');
+}
+
+.document-engine-video video {
+  margin: 20px auto;
+  display: block;
+  max-width: 95%;
+}
+
+.document-engine-audio audio {
+  display: block;
+  margin: 16px auto;
+  width: 50%;
+  min-width: 240px;
+}
+
+.document-engine-message {
+  margin: 20px auto;
+  text-align: center;
+  color: {$greytext};
+}