From 231ef25a15603c3118799164feee3fd3b5260d3a Mon Sep 17 00:00:00 2001
From: John Thomson <john_thomson@sil.org>
Date: Tue, 24 Mar 2026 14:54:17 -0500
Subject: [PATCH] Preserve QR code when switching to standard mode (BL-16060)

---
 src/BloomExe/Book/Book.cs                      |  8 +++++++-
 src/BloomExe/Book/BookStorage.cs               | 10 ++++++++--
 src/BloomExe/web/controllers/EditingViewApi.cs |  4 ++++
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/BloomExe/Book/Book.cs b/src/BloomExe/Book/Book.cs
index 1f6ca06d034a..21375ebeba25 100644
--- a/src/BloomExe/Book/Book.cs
+++ b/src/BloomExe/Book/Book.cs
@@ -5403,12 +5403,18 @@ var page in RawDom
         public void UpdateSupportFiles()
         {
             Storage.UpdateSupportFiles();
+            UpdateQrCodeHtmlForCurrentSettings();
+        }
+
+        internal void UpdateQrCodeHtmlForCurrentSettings(bool updateQrCodeFileEvenIfItExists = true)
+        {
             BookStorage.UpdateQrCode(
                 OurHtmlDom,
                 CollectionSettings.ShowBlorgLanguageQrCode,
                 Language1Tag,
                 CollectionSettings.BadgeQrCodeLabelLocalizedWithLang,
-                FolderPath
+                FolderPath,
+                updateQrCodeFileEvenIfItExists
             );
         }
 
diff --git a/src/BloomExe/Book/BookStorage.cs b/src/BloomExe/Book/BookStorage.cs
index 238f88310af2..40f375d24722 100644
--- a/src/BloomExe/Book/BookStorage.cs
+++ b/src/BloomExe/Book/BookStorage.cs
@@ -2789,7 +2789,8 @@ public static void UpdateQrCode(
             bool shouldHaveQrCode,
             string langCode,
             string badgeQrCodeLabelLocalizedWithLang,
-            string bookFolderPath
+            string bookFolderPath,
+            bool updateQrCodeFileEvenIfItExists = true
         )
         {
             var qrWrappers = dom.SafeSelectNodes(
@@ -2799,6 +2800,8 @@ string bookFolderPath
             var url = "https://bloomlibrary.org/language:" + langCode;
 
             string qrFileName = null;
+            const string kQrFileName = "lang-qr-code.png";
+            var qrFilePath = Path.Combine(bookFolderPath, kQrFileName);
 
             foreach (var qrWrapper in qrWrappers)
             {
@@ -2823,7 +2826,10 @@ string bookFolderPath
 
                 if (qrFileName == null)
                 {
-                    qrFileName = GenerateQrCodeImage(bookFolderPath, url);
+                    if (updateQrCodeFileEvenIfItExists || !RobustFile.Exists(qrFilePath))
+                        qrFileName = GenerateQrCodeImage(bookFolderPath, url);
+                    else
+                        qrFileName = kQrFileName;
                 }
 
                 AdjustHtmlForHavingQrCode(
diff --git a/src/BloomExe/web/controllers/EditingViewApi.cs b/src/BloomExe/web/controllers/EditingViewApi.cs
index f6af7d3c507e..682425de77e9 100644
--- a/src/BloomExe/web/controllers/EditingViewApi.cs
+++ b/src/BloomExe/web/controllers/EditingViewApi.cs
@@ -203,6 +203,10 @@ private void HandleToggleCustomCover(ApiRequest request)
                     // Bring everything up to date consistent with the new
                     // state. Might be enough just do the BookData update.
                     book.EnsureUpToDateMemory(new NullProgress());
+                    // Toggling between custom and standard layout can replace the xMatter page HTML,
+                    // so reapply branding QR-code HTML adjustments for the current book settings.
+                    // This should not need to regenerate the QR code file.
+                    book.UpdateQrCodeHtmlForCurrentSettings(updateQrCodeFileEvenIfItExists: false);
 
                     var updatedPageElt = book.GetPage(pageId)?.GetDivNodeForThisPage();
                     if (updatedPageElt != null)