From 34326a0d466ecf9e16e63670e7ae6fccd6e48076 Mon Sep 17 00:00:00 2001
From: Anna Wang <annawangx@gmail.com>
Date: Wed, 27 May 2026 03:33:20 +0000
Subject: [PATCH] add custom JS to preserve sidebar scroll position across
 navigation

---
 sidebar-scroll.js | 86 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 sidebar-scroll.js

diff --git a/sidebar-scroll.js b/sidebar-scroll.js
new file mode 100644
index 0000000..5f0c80b
--- /dev/null
+++ b/sidebar-scroll.js
@@ -0,0 +1,86 @@
+(function () {
+  if (typeof window === "undefined") return;
+
+  var KEY = "kernel-docs-sidebar-scroll";
+
+  function findSidebar() {
+    var candidates = document.querySelectorAll(
+      "aside, nav[aria-label='Sidebar'], aside[aria-label='Sidebar'], #sidebar"
+    );
+    for (var i = 0; i < candidates.length; i++) {
+      var el = candidates[i];
+      if (el.scrollHeight > el.clientHeight + 1) return el;
+    }
+    return null;
+  }
+
+  function save() {
+    var sb = findSidebar();
+    if (sb) {
+      try { sessionStorage.setItem(KEY, String(sb.scrollTop)); } catch (e) {}
+    }
+  }
+
+  function restore() {
+    var sb = findSidebar();
+    if (!sb) return false;
+    var raw;
+    try { raw = sessionStorage.getItem(KEY); } catch (e) { return false; }
+    if (raw === null) return false;
+    var top = parseInt(raw, 10);
+    if (isNaN(top)) return false;
+    if (Math.abs(sb.scrollTop - top) > 1) sb.scrollTop = top;
+    return true;
+  }
+
+  var saveTimer;
+  document.addEventListener(
+    "scroll",
+    function (e) {
+      var sb = findSidebar();
+      if (!sb) return;
+      var t = e.target;
+      if (t === sb || (t.contains && t.contains(sb)) || sb.contains(t)) {
+        clearTimeout(saveTimer);
+        saveTimer = setTimeout(save, 80);
+      }
+    },
+    true
+  );
+
+  document.addEventListener(
+    "click",
+    function (e) {
+      if (e.target && e.target.closest && e.target.closest("a")) save();
+    },
+    true
+  );
+
+  function pollRestore() {
+    var attempts = 0;
+    var iv = setInterval(function () {
+      attempts++;
+      if (restore() || attempts > 30) clearInterval(iv);
+    }, 50);
+  }
+
+  var origPush = history.pushState;
+  history.pushState = function () {
+    var r = origPush.apply(this, arguments);
+    pollRestore();
+    return r;
+  };
+  var origReplace = history.replaceState;
+  history.replaceState = function () {
+    var r = origReplace.apply(this, arguments);
+    pollRestore();
+    return r;
+  };
+  window.addEventListener("popstate", pollRestore);
+
+  if (document.readyState === "complete") {
+    pollRestore();
+  } else {
+    window.addEventListener("load", pollRestore);
+  }
+})();