Improve design of the rich text editor (#9533)

New design for rich text composer

src/components/views/rooms/wysiwyg_composer/hooks/useIsFocused.ts

@@ -0,0 +1,36 @@
+/*
+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 { FocusEvent, useCallback, useEffect, useRef, useState } from "react";
+
+export function useIsFocused() {
+    const [isFocused, setIsFocused] = useState(false);
+    const timeoutIDRef = useRef<number>();
+
+    useEffect(() => () => clearTimeout(timeoutIDRef.current), [timeoutIDRef]);
+    const onFocus = useCallback((event: FocusEvent<HTMLElement>) => {
+        clearTimeout(timeoutIDRef.current);
+        if (event.type === 'focus') {
+            setIsFocused(true);
+        } else {
+            // To avoid a blink when we switch mode between plain text and rich text mode
+            // We delay the unfocused action
+            timeoutIDRef.current = setTimeout(() => setIsFocused(false), 100);
+        }
+    }, [setIsFocused, timeoutIDRef]);
+
+    return { isFocused, onFocus };
+}