From aa289b17b6a8f2af3fabaef552f3f90b8b6dc246 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Thu, 9 Sep 2021 14:21:15 +0200
Subject: [PATCH] Don't create `PDFViewerApplication.pdfHistory` when the
 browsing history is disabled

Similar to other viewer components, e.g. the `PDFFindBar` and `PDFPresentationMode`, there's no need to create a `PDFHistory`-instance when it's not going to be used.
---
 web/app.js              | 20 +++++++++++---------
 web/pdf_link_service.js |  8 ++------
 2 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/web/app.js b/web/app.js
index c2c6b7eae..b0d4be166 100644
--- a/web/app.js
+++ b/web/app.js
@@ -534,11 +534,15 @@ const PDFViewerApplication = {
     });
     pdfRenderingQueue.setThumbnailViewer(this.pdfThumbnailViewer);
 
-    this.pdfHistory = new PDFHistory({
-      linkService: pdfLinkService,
-      eventBus,
-    });
-    pdfLinkService.setHistory(this.pdfHistory);
+    // The browsing history is only enabled when the viewer is standalone,
+    // i.e. not when it is embedded in a web page.
+    if (!this.isViewerEmbedded && !AppOptions.get("disableHistory")) {
+      this.pdfHistory = new PDFHistory({
+        linkService: pdfLinkService,
+        eventBus,
+      });
+      pdfLinkService.setHistory(this.pdfHistory);
+    }
 
     if (!this.supportsIntegratedFind) {
       this.findBar = new PDFFindBar(appConfig.findBar, eventBus, this.l10n);
@@ -1631,9 +1635,7 @@ const PDFViewerApplication = {
    * @private
    */
   _initializePdfHistory({ fingerprint, viewOnLoad, initialDest = null }) {
-    if (this.isViewerEmbedded || AppOptions.get("disableHistory")) {
-      // The browsing history is only enabled when the viewer is standalone,
-      // i.e. not when it is embedded in a web page.
+    if (!this.pdfHistory) {
       return;
     }
     this.pdfHistory.initialize({
@@ -2456,7 +2458,7 @@ function webViewerHashchange(evt) {
   }
   if (!PDFViewerApplication.isInitialViewSet) {
     PDFViewerApplication.initialBookmark = hash;
-  } else if (!PDFViewerApplication.pdfHistory.popStateInProgress) {
+  } else if (!PDFViewerApplication.pdfHistory?.popStateInProgress) {
     PDFViewerApplication.pdfLinkService.setHash(hash);
   }
 }
diff --git a/web/pdf_link_service.js b/web/pdf_link_service.js
index 32109f183..cd83e2711 100644
--- a/web/pdf_link_service.js
+++ b/web/pdf_link_service.js
@@ -380,15 +380,11 @@ class PDFLinkService {
     // See PDF reference, table 8.45 - Named action
     switch (action) {
       case "GoBack":
-        if (this.pdfHistory) {
-          this.pdfHistory.back();
-        }
+        this.pdfHistory?.back();
         break;
 
       case "GoForward":
-        if (this.pdfHistory) {
-          this.pdfHistory.forward();
-        }
+        this.pdfHistory?.forward();
         break;
 
       case "NextPage":