frontend/src/components/TopNav.tsx

@@ -20,12 +20,13 @@ type Props = { user: User | null }
 export default (({ user }: Props) => {
   const location = useLocation ()
 
-  const itemRefs = useRef<(HTMLAnchorElement | null)[]> ([])
+  const dirRef = useRef<(-1) | 1> (1)
+  const itemsRef = useRef<(HTMLAnchorElement | null)[]> ([])
   const navRef = useRef<HTMLDivElement | null> (null)
 
   const measure = () => {
     const nav = navRef.current
-    const el = itemRefs.current[activeIdx]
+    const el = itemsRef.current[activeIdx]
     if (!(nav) || !(el) || activeIdx < 0)
       return
 
@@ -44,7 +45,6 @@ export default (({ user }: Props) => {
   const [menuOpen, setMenuOpen] = useState (false)
   const [openItemIdx, setOpenItemIdx] = useState (-1)
   const [postCount, setPostCount] = useState<number | null> (null)
-  const [subDir, setSubDir] = useState<(-1) | 1> (1)
   const [wikiId, setWikiId] = useState<number | null> (WikiIdBus.get ())
 
   const wikiPageFlg = Boolean (/^\/wiki\/(?!new|changes)[^\/]+/.test (location.pathname) && wikiId)
@@ -80,6 +80,14 @@ export default (({ user }: Props) => {
 
   const prevActiveIdxRef = useRef<number> (activeIdx)
 
+  if (activeIdx !== prevActiveIdxRef.current)
+    {
+      dirRef.current = activeIdx > prevActiveIdxRef.current ? 1 : -1
+      prevActiveIdxRef.current = activeIdx
+    }
+
+  const dir = dirRef.current
+
   useLayoutEffect (() => {
     if (activeIdx < 0)
       return
@@ -99,15 +107,6 @@ export default (({ user }: Props) => {
     return () => unsubscribe ()
   }, [])
 
-  useEffect (() => {
-    const prev = prevActiveIdxRef.current
-    if (prev !== activeIdx)
-      {
-	setSubDir (activeIdx > prev ? 1 : -1)
-	prevActiveIdxRef.current = activeIdx
-      }
-  }, [activeIdx])
-
   useEffect (() => {
     setMenuOpen (false)
     setOpenItemIdx (menu.findIndex (item => (
@@ -150,9 +149,9 @@ export default (({ user }: Props) => {
 
 	    <div ref={navRef} className="relative hidden md:flex h-full items-center">
 	      <div aria-hidden
-		   className={cn ('absolute top-1/2 -translate-y-1/2 h-full rounded-md',
+		   className={cn ('absolute top-1/2 -translate-y-1/2 h-full',
 				  'bg-yellow-200 dark:bg-red-950',
-				  'transition-[transform,width,opacity] duration-200 ease-out')}
+				  'transition-[transform,width] duration-200 ease-out')}
 		   style={{ width:      hl.width,
 			    transform:  `translate(${ hl.left }px, -50%)`,
 			    opacity:    hl.visible ? 1 : 0 }}/>
@@ -161,12 +160,10 @@ export default (({ user }: Props) => {
 		  <Link key={i}
 			to={item.to}
 			ref={el => {
-			  itemRefs.current[i] = el
+			  itemsRef.current[i] = el
 			}}
 			className={cn ('relative z-10 flex h-full items-center px-5',
-				       ((i === openItemIdx)
-					? 'font-bold'
-					: 'opacity-90 hover:opacity-100'))}>
+				       (i === openItemIdx) && 'font-bold')}>
 		    {item.name}
 		  </Link>))}
 	    </div>
@@ -186,16 +183,20 @@ export default (({ user }: Props) => {
 	  </a>
 	</nav>
 
-	<div className="hidden md:flex bg-yellow-200 dark:bg-red-950
-			items-center w-full min-h-[40px] px-3 overflow-hidden">
-	  <AnimatePresence mode="wait" initial={false}>
+	<div className="relative hidden md:flex bg-yellow-200 dark:bg-red-950
+			items-center w-full min-h-[40px] overflow-hidden">
+	  <AnimatePresence initial={false} custom={dir}>
 	    <motion.div
 		key={activeIdx}
-		className="flex items-center"
-		initial={{ y: subDir * 24, opacity: 0 }}
-		animate={{ y: 0, opacity: 1 }}
-		exit={{ y: subDir * 24, opacity: 0 }}
-		transition={{ duration: .1, ease: 'easeOut' }}>
+		custom={dir}
+		variants={{ enter: (d: -1 | 1) => ({ y: d * 24, opacity: 0 }),
+			    centre: { y: 0, opacity: 1 },
+			    exit: (d: -1 | 1) => ({ y: (-d) * 24, opacity: 0 }) }}
+		className="absolute inset-0 flex items-center px-3"
+		initial="enter"
+		animate="centre"
+		exit="exit"
+		transition={{ duration: .2, ease: 'easeOut' }}>
 	      {(menu[activeIdx]?.subMenu ?? [])
 	       .filter (item => item.visible ?? true)
 	       .map ((item, i) => (