Add stuff to app header

src-web/hooks/useTimedBoolean.ts

@@ -0,0 +1,19 @@
+import { useRef, useState } from 'react';
+import { useUnmount } from 'react-use';
+
+/** Returns a boolean that is true for a given number of milliseconds. */
+export function useTimedBoolean(millis = 1000): [boolean, () => void] {
+  const [value, setValue] = useState(false);
+  const timeout = useRef<NodeJS.Timeout | null>(null);
+  const reset = () => timeout.current && clearTimeout(timeout.current);
+
+  useUnmount(reset);
+
+  const setToTrue = () => {
+    setValue(true);
+    reset();
+    timeout.current = setTimeout(() => setValue(false), millis);
+  };
+
+  return [value, setToTrue];
+}