1 files changed, 17 insertions, 3 deletions
diff --git a/src/librustdoc/html/static/js/source-script.js b/src/librustdoc/html/static/js/source-script.js
index c45d614293a..06d15d9e5ff 100644
--- a/src/librustdoc/html/static/js/source-script.js
+++ b/src/librustdoc/html/static/js/source-script.js
@@ -10,7 +10,7 @@
 (function() {
 
 const rootPath = document.getElementById("rustdoc-vars").attributes["data-root-path"].value;
-let oldScrollPosition = 0;
+let oldScrollPosition = null;
 
 const NAME_OFFSET = 0;
 const DIRS_OFFSET = 1;
@@ -75,18 +75,21 @@ function toggleSidebar() {
             oldScrollPosition = window.scrollY;
             document.body.style.position = "fixed";
             document.body.style.top = `-${oldScrollPosition}px`;
+        } else {
+            oldScrollPosition = null;
         }
         addClass(document.documentElement, "source-sidebar-expanded");
         child.innerText = "<";
         updateLocalStorage("source-sidebar-show", "true");
     } else {
-        if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT) {
+        if (window.innerWidth < window.RUSTDOC_MOBILE_BREAKPOINT && oldScrollPosition !== null) {
             // This is to keep the scroll position on mobile.
             document.body.style.position = "";
             document.body.style.top = "";
             // The scroll position is lost when resetting the style, hence why we store it in
-            // `oldScroll`.
+            // `oldScrollPosition`.
             window.scrollTo(0, oldScrollPosition);
+            oldScrollPosition = null;
         }
         removeClass(document.documentElement, "source-sidebar-expanded");
         child.innerText = ">";
@@ -94,6 +97,17 @@ function toggleSidebar() {
     }
 }
 
+window.addEventListener("resize", () => {
+    if (window.innerWidth >= window.RUSTDOC_MOBILE_BREAKPOINT && oldScrollPosition !== null) {
+        // If the user opens the sidebar in "mobile" mode, and then grows the browser window,
+        // we need to switch away from mobile mode and make the main content area scrollable.
+        document.body.style.position = "";
+        document.body.style.top = "";
+        window.scrollTo(0, oldScrollPosition);
+        oldScrollPosition = null;
+    }
+});
+
 function createSidebarToggle() {
     const sidebarToggle = document.createElement("div");
     sidebarToggle.id = "sidebar-toggle";