From 1dffe20f05d343bb04d9eed9673a25502f2b1a31 Mon Sep 17 00:00:00 2001
From: Copilot <198982749+Copilot@users.noreply.github.com>
Date: Thu, 19 Mar 2026 10:45:43 +0000
Subject: [PATCH] Fix beamer PDF preview scroll drift on recompile (#32077)

GitOrigin-RevId: 6f15671ba7f7944446e48136b775dea7e5c9b34a
---
 .../features/pdf-preview/util/pdf-js-wrapper.ts  | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/services/web/frontend/js/features/pdf-preview/util/pdf-js-wrapper.ts b/services/web/frontend/js/features/pdf-preview/util/pdf-js-wrapper.ts
index 5c73bee2b9..45e7a322db 100644
--- a/services/web/frontend/js/features/pdf-preview/util/pdf-js-wrapper.ts
+++ b/services/web/frontend/js/features/pdf-preview/util/pdf-js-wrapper.ts
@@ -161,11 +161,23 @@ export default class PDFJSWrapper {
 
   // get the current page, offset and page size
   get currentPosition() {
-    const pageIndex = this.viewer.currentPageNumber - 1
+    const containerRect = this.container.getBoundingClientRect()
+
+    let pageIndex = this.viewer.currentPageNumber - 1
+    for (let i = pageIndex; i >= 0; i--) {
+      const pageView = this.viewer.getPageView(i)
+      if (!pageView?.div) continue
+      const pageRect = pageView.div.getBoundingClientRect()
+      if (pageRect.bottom < containerRect.top) {
+        pageIndex = i + 1
+        break
+      }
+      pageIndex = i
+    }
+
     const pageView = this.viewer.getPageView(pageIndex)
     const pageRect = pageView.div.getBoundingClientRect()
 
-    const containerRect = this.container.getBoundingClientRect()
     const dy = containerRect.top - pageRect.top
     const dx = containerRect.left - pageRect.left
     const [left, top] = pageView.viewport.convertToPdfPoint(dx, dy)