Add image editor

ts/hooks/usePortal.ts

@@ -0,0 +1,21 @@
+// Copyright 2019-2020 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { useEffect, useState } from 'react';
+
+export function usePortal(): HTMLDivElement | null {
+  const [root, setRoot] = useState<HTMLDivElement | null>(null);
+
+  useEffect(() => {
+    const div = document.createElement('div');
+    document.body.appendChild(div);
+    setRoot(div);
+
+    return () => {
+      document.body.removeChild(div);
+      setRoot(null);
+    };
+  }, []);
+
+  return root;
+}