Auto scroll sticky ToC with content (#3115)

assets/js/_main.js

@@ -81,6 +81,23 @@ $(function() {
     });
   }
 
+  // Auto scroll sticky ToC with content
+  document.addEventListener("gumshoeActivate", function (event) {
+    var target = event.target;
+    var scrollOptions = { behavior: "auto", block: "nearest", inline: "start" };
+
+    var tocElement = document.querySelector("aside.sidebar__right.sticky");
+    if (!tocElement) return;
+    if (!window.getComputedStyle(tocElement).position !== "sticky") return;
+
+    if (target.parentElement.classList.contains("toc__menu") && target == target.parentElement.firstElementChild) {
+      // Scroll to top instead
+      document.querySelector("nav.toc header").scrollIntoView(scrollOptions);
+    } else {
+      target.scrollIntoView(scrollOptions);
+    }
+  });
+
   // add lightbox class to all image links
   $(
     "a[href$='.jpg'],a[href$='.jpeg'],a[href$='.JPG'],a[href$='.png'],a[href$='.gif'],a[href$='.webp']"