Add dialog to navigate long room topics (#8517)

src/hooks/useHover.ts

@@ -0,0 +1,42 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import React, { useEffect, useState } from "react";
+
+export default function useHover(ref: React.MutableRefObject<HTMLElement>) {
+    const [hovered, setHoverState] = useState(false);
+
+    const handleMouseOver = () => setHoverState(true);
+    const handleMouseOut = () => setHoverState(false);
+
+    useEffect(
+        () => {
+            const node = ref.current;
+            if (node) {
+                node.addEventListener("mouseover", handleMouseOver);
+                node.addEventListener("mouseout", handleMouseOut);
+
+                return () => {
+                    node.removeEventListener("mouseover", handleMouseOver);
+                    node.removeEventListener("mouseout", handleMouseOut);
+                };
+            }
+        },
+        [ref],
+    );
+
+    return hovered;
+}