feat: multiplayer undo / redo (#7348)

packages/excalidraw/hooks/useEmitter.ts

@@ -0,0 +1,21 @@
+import { useEffect, useState } from "react";
+import { Emitter } from "../emitter";
+
+export const useEmitter = <TEvent extends unknown>(
+  emitter: Emitter<[TEvent]>,
+  initialState: TEvent,
+) => {
+  const [event, setEvent] = useState<TEvent>(initialState);
+
+  useEffect(() => {
+    const unsubscribe = emitter.on((event) => {
+      setEvent(event);
+    });
+
+    return () => {
+      unsubscribe();
+    };
+  }, [emitter]);
+
+  return event;
+};