Improve design of the rich text editor (#9533)

New design for rich text composer

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

@@ -0,0 +1,37 @@
+/*
+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 { MutableRefObject, useEffect, useState } from "react";
+
+export function useIsExpanded(ref: MutableRefObject<HTMLElement | null>, breakingPoint: number) {
+    const [isExpanded, setIsExpanded] = useState(false);
+    useEffect(() => {
+        if (ref.current) {
+            const editor = ref.current;
+            const resizeObserver = new ResizeObserver(entries => {
+                requestAnimationFrame(() => {
+                    const height = entries[0]?.contentBoxSize?.[0].blockSize;
+                    setIsExpanded(height >= breakingPoint);
+                });
+            });
+
+            resizeObserver.observe(editor);
+            return () => resizeObserver.unobserve(editor);
+        }
+    }, [ref, breakingPoint]);
+
+    return isExpanded;
+}