From f063ceeb0d3aa3a8a0293a4cb5579247fc059d8f Mon Sep 17 00:00:00 2001
From: Calixte Denizet <calixte.denizet@gmail.com>
Date: Sun, 6 Dec 2020 20:59:10 +0100
Subject: [PATCH] Fix automatic zoom under spread mode (#12699)

---
 web/base_viewer.js | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/web/base_viewer.js b/web/base_viewer.js
index 3b9b78ca40e1ad..060cf331f79bdc 100644
--- a/web/base_viewer.js
+++ b/web/base_viewer.js
@@ -735,6 +735,11 @@ class BaseViewer {
       if (!currentPage) {
         return;
       }
+      const factor =
+        this.spreadMode === SpreadMode.NONE || this._isScrollModeHorizontal
+          ? 1
+          : 2;
+
       const noPadding = this.isInPresentationMode || this.removePageBorders;
       let hPadding = noPadding ? 0 : SCROLLBAR_PADDING;
       let vPadding = noPadding ? 0 : VERTICAL_PADDING;
@@ -743,8 +748,9 @@ class BaseViewer {
         [hPadding, vPadding] = [vPadding, hPadding]; // Swap the padding values.
       }
       const pageWidthScale =
-        ((this.container.clientWidth - hPadding) / currentPage.width) *
-        currentPage.scale;
+        (((this.container.clientWidth - hPadding) / currentPage.width) *
+          currentPage.scale) /
+        factor;
       const pageHeightScale =
         ((this.container.clientHeight - vPadding) / currentPage.height) *
         currentPage.scale;