fix: Open PDF file in "richdocuments" if it is not downloadable

The PDF viewer must be able to download the file to show it, and if the
file is not downloadable an error message was just shown. However,
Nextcloud Office ("richdocuments") is able to show PDF files even if
they can not be downloaded, so now the viewer is reopened forcing
"richdocuments" to handle opening the file when it is not downloadable.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>

Author: danxuliu

src/views/PDFView.vue

@@ -7,7 +7,7 @@
 		ref="iframe"
 		:src="iframeSrc"
 		@load="onIFrameLoaded" />
-	<div v-else id="emptycontent">
+	<div v-else-if="!isRichDocumentsAvailable" id="emptycontent">
 		<div class="icon-error" />
 		<h3>{{ t('files_pdfviewer', 'To view a shared PDF file, the download needs to be allowed for this file share') }}</h3>
 	</div>
@@ -59,6 +59,10 @@ export default {
 			return true
 		},
 
+		isRichDocumentsAvailable() {
+			return 'richdocuments' in OC.appswebroots
+		},
+
 		isEditable() {
 			return this.file?.permissions?.indexOf('W') >= 0
 		},
@@ -68,6 +72,23 @@ export default {
 		if (!this.isDownloadable) {
 			this.doneLoading()
 
+			if (this.isRichDocumentsAvailable) {
+				console.info('PDF file is not downloadable, but "richdocuments" is available, so falling back to it')
+
+				// Opening the viewer again overwrites its current state, so the
+				// current options need to be explicitly passed again.
+				OCA.Viewer.openWith('richdocuments', {
+					fileInfo: this.file,
+					list: OCA.Viewer.list,
+					enableSidebar: OCA.Viewer.enableSidebar,
+					loadMore: OCA.Viewer.loadMore,
+					canLoop: OCA.Viewer.canLoop,
+					onPrev: OCA.Viewer.onPrev,
+					onNext: OCA.Viewer.onNext,
+					onClose: OCA.Viewer.onClose,
+				})
+			}
+
 			return
 		}