From d8e5a04cb189e6ef0c676c44da7918b42e845df1 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Sun, 16 Aug 2026 10:55:44 +0200
Subject: [PATCH] Define the visible-page sort function, used in
 `getVisibleElements`, once

When scrolling through long documents, especially when using spread modes and/or wrapped scrolling, the visible-page sorting can be invoked *a lot*.
Hence it seems like a good idea to define the sort function just once, rather than re-creating it for every invocation.
---
 web/ui_utils.js | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/web/ui_utils.js b/web/ui_utils.js
index 3e1252f67ef63..b7c52ab226b33 100644
--- a/web/ui_utils.js
+++ b/web/ui_utils.js
@@ -399,6 +399,11 @@ function backtrackBeforeAllVisibleElements(index, views, top) {
   return index;
 }
 
+function visibleSort(a, b) {
+  const pc = a.percent - b.percent;
+  return Math.abs(pc) > 0.001 ? -pc : a.id - b.id; // ensure stability
+}
+
 /**
  * @typedef {Object} GetVisibleElementsParameters
  * @property {HTMLElement} scrollEl - A container that can possibly scroll.
@@ -576,13 +581,7 @@ function getVisibleElements({
     last = visible.at(-1);
 
   if (sortByVisibility) {
-    visible.sort(function (a, b) {
-      const pc = a.percent - b.percent;
-      if (Math.abs(pc) > 0.001) {
-        return -pc;
-      }
-      return a.id - b.id; // ensure stability
-    });
+    visible.sort(visibleSort);
   }
   return { first, last, views: visible, ids };
 }