Use the new direct endpoint for the og:image

Some providers had issues when using the preview link (since it was
double encoded).

Now we actually serve the max size preview so it looks better

The image isn't cropped anymore so supporting platforms can just embed
the whole image.

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

apps/files_sharing/lib/Controller/ShareController.php

@@ -373,15 +373,20 @@ class ShareController extends Controller {
 		$shareTmpl['previewMaxY'] = $this->config->getSystemValue('preview_max_y', 1024);
 		$shareTmpl['disclaimer'] = $this->config->getAppValue('core', 'shareapi_public_link_disclaimertext', null);
 		$shareTmpl['previewURL'] = $shareTmpl['downloadURL'];
+		$ogPreview = '';
 		if ($shareTmpl['previewSupported']) {
 			$shareTmpl['previewImage'] = $this->urlGenerator->linkToRouteAbsolute( 'files_sharing.PublicPreview.getPreview',
 				['x' => 200, 'y' => 200, 'file' => $shareTmpl['directory_path'], 't' => $shareTmpl['dirToken']]);
+			$ogPreview = $shareTmpl['previewImage'];
+
 			// We just have direct previews for image files
 			if ($share->getNode()->getMimePart() === 'image') {
 				$shareTmpl['previewURL'] = $this->urlGenerator->linkToRouteAbsolute('files_sharing.publicpreview.directLink', ['token' => $token]);
+				$ogPreview = $shareTmpl['previewURL'];
 			}
 		} else {
 			$shareTmpl['previewImage'] = $this->urlGenerator->getAbsoluteURL($this->urlGenerator->imagePath('core', 'favicon-fb.png'));
+			$ogPreview = $shareTmpl['previewImage'];
 		}
 
 		// Load files we need
@@ -411,7 +416,7 @@ class ShareController extends Controller {
 		\OCP\Util::addHeader('meta', ['property' => "og:site_name", 'content' => $this->defaults->getName()]);
 		\OCP\Util::addHeader('meta', ['property' => "og:url", 'content' => $shareTmpl['shareUrl']]);
 		\OCP\Util::addHeader('meta', ['property' => "og:type", 'content' => "object"]);
-		\OCP\Util::addHeader('meta', ['property' => "og:image", 'content' => $shareTmpl['previewImage']]);
+		\OCP\Util::addHeader('meta', ['property' => "og:image", 'content' => $ogPreview]);
 
 		$this->eventDispatcher->dispatch('OCA\Files_Sharing::loadAdditionalScripts');