Add device visibility and responsive navigation for 1.10.0

public/assets/tabs.js

@@ -25,14 +25,19 @@
       panels[index].querySelector('.tabs-heading')?.classList.add('visually-hidden');
     });
 
+    const available = () => links.map((link, i) => getComputedStyle(link.parentElement).display !== 'none' ? i : -1).filter(i => i >= 0);
+    let selected = -1;
     const select = (index, moveFocus = true) => {
+      const visible = available();
+      if (!visible.includes(index)) index = visible[0] ?? -1;
+      selected = index;
       links.forEach((link, i) => {
         const current = i === index;
         link.setAttribute('aria-selected', String(current));
         link.tabIndex = current ? 0 : -1;
         panels[i].hidden = !current;
       });
-      if (moveFocus) links[index].focus();
+      if (moveFocus && index >= 0) links[index].focus();
     };
 
     list.addEventListener('click', event => {
@@ -46,15 +51,18 @@
     list.addEventListener('keydown', event => {
       const index = links.indexOf(event.target.closest('a'));
       if (index === -1) return;
-      const moves = { ArrowRight: index + 1, ArrowLeft: index - 1, Home: 0, End: links.length - 1 };
+      const visible = available(), position = visible.indexOf(index);
+      if (!visible.length) return;
+      const moves = { ArrowRight: position + 1, ArrowLeft: position - 1, Home: 0, End: visible.length - 1 };
       if (!(event.key in moves)) return;
       event.preventDefault();
-      select((moves[event.key] + links.length) % links.length);
+      select(visible[(moves[event.key] + visible.length) % visible.length]);
     });
 
     // A link from elsewhere may point straight at one panel.
     const deepLink = panels.findIndex(panel => panel.id === location.hash.slice(1));
     select(deepLink === -1 ? 0 : deepLink, false);
+    window.addEventListener('resize', () => select(selected, false));
     group.classList.add('tabs-ready');
   };