From 31cb38694173a385e1fefc5953774a40389cc547 Mon Sep 17 00:00:00 2001
From: Alf Eaton <alf.eaton@overleaf.com>
Date: Mon, 10 Jan 2022 13:58:31 +0000
Subject: [PATCH] Only store/restore PDF scroll position when visible (#6218)

GitOrigin-RevId: c2023b5173fe4668f52da3e096c3dfc0124a7248
---
 .../js/features/pdf-preview/components/pdf-js-viewer.js  | 9 ++++++++-
 .../js/features/pdf-preview/util/pdf-js-wrapper.js       | 4 ++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/services/web/frontend/js/features/pdf-preview/components/pdf-js-viewer.js b/services/web/frontend/js/features/pdf-preview/components/pdf-js-viewer.js
index 8ade85b673..5d84205f1c 100644
--- a/services/web/frontend/js/features/pdf-preview/components/pdf-js-viewer.js
+++ b/services/web/frontend/js/features/pdf-preview/components/pdf-js-viewer.js
@@ -82,13 +82,16 @@ function PdfJsViewer({ url }) {
     let storePositionTimer
 
     if (initialised && pdfJsWrapper) {
+      if (!pdfJsWrapper.isVisible()) {
+        return
+      }
+
       // store the scroll position in localStorage, for the synctex button
       const storePosition = debounce(pdfViewer => {
         // set position for "sync to code" button
         try {
           setPosition(pdfViewer.currentPosition)
         } catch (error) {
-          // TODO: investigate handling missing offsetParent in jsdom
           // console.error(error)
         }
       }, 500)
@@ -139,6 +142,10 @@ function PdfJsViewer({ url }) {
   // restore the saved scale and scroll position
   useEffect(() => {
     if (initialised && pdfJsWrapper) {
+      if (!pdfJsWrapper.isVisible()) {
+        return
+      }
+
       setScale(scale => {
         setPosition(position => {
           if (position) {
diff --git a/services/web/frontend/js/features/pdf-preview/util/pdf-js-wrapper.js b/services/web/frontend/js/features/pdf-preview/util/pdf-js-wrapper.js
index 70dbaeac03..a387d424f7 100644
--- a/services/web/frontend/js/features/pdf-preview/util/pdf-js-wrapper.js
+++ b/services/web/frontend/js/features/pdf-preview/util/pdf-js-wrapper.js
@@ -183,6 +183,10 @@ export default class PDFJSWrapper {
     })
   }
 
+  isVisible() {
+    return this.viewer.container.offsetParent !== null
+  }
+
   abortDocumentLoading() {
     this.loadDocumentTask = undefined
   }