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themes/hugo-theme-stack/assets/ts/smoothAnchors.ts

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+// Implements smooth scrolling when clicking on an anchor link.
+// This is required instead of using modern CSS because Chromium does not currently support scrolling
+// one element with scrollTo while another element is scrolled because of a click on a link. This would
+// thus not work with the ToC scrollspy and e.g. footnotes.
+
+// Here are additional links about this issue:
+// - https://stackoverflow.com/questions/49318497/google-chrome-simultaneously-smooth-scrollintoview-with-more-elements-doesn
+// - https://stackoverflow.com/questions/57214373/scrollintoview-using-smooth-function-on-multiple-elements-in-chrome
+// - https://bugs.chromium.org/p/chromium/issues/detail?id=833617
+// - https://bugs.chromium.org/p/chromium/issues/detail?id=1043933
+// - https://bugs.chromium.org/p/chromium/issues/detail?id=1121151
+
+const anchorLinksQuery = "a[href]";
+
+function setupSmoothAnchors() {
+    document.querySelectorAll(anchorLinksQuery).forEach(aElement => {
+        let href = aElement.getAttribute("href");
+        if (!href.startsWith("#")) {
+            return;
+        }
+        aElement.addEventListener("click", clickEvent => {
+            clickEvent.preventDefault();
+
+            const targetId = decodeURI(aElement.getAttribute("href").substring(1)),
+                target = document.getElementById(targetId) as HTMLElement,
+                offset = target.getBoundingClientRect().top - document.documentElement.getBoundingClientRect().top;
+
+            window.history.pushState({}, "", aElement.getAttribute("href"));
+            scrollTo({
+                top: offset,
+                behavior: "smooth"
+            });
+        });
+    });
+}
+
+export { setupSmoothAnchors };