snapshot of https://github.com/RocketChat/Rocket.Chat.git (develop, 2026-09-16; blobs > 131072B omitted)

apps/meteor/client/sidebar/Item/useDeferredMenuMount.ts

@@ -0,0 +1,59 @@
+import { useCallback, useEffect, useRef, useState } from 'react';
+
+type IdleHandle = { type: 'idle' | 'timeout'; id: number };
+
+const schedule = (fn: () => void): IdleHandle => {
+	if (typeof window !== 'undefined' && typeof window.requestIdleCallback === 'function') {
+		return { type: 'idle', id: window.requestIdleCallback(fn, { timeout: 200 }) };
+	}
+	return { type: 'timeout', id: window.setTimeout(fn, 50) };
+};
+
+const cancel = (handle: IdleHandle) => {
+	if (handle.type === 'idle' && typeof window.cancelIdleCallback === 'function') {
+		window.cancelIdleCallback(handle.id);
+		return;
+	}
+	window.clearTimeout(handle.id);
+};
+
+/**
+ * Defers mounting the sidebar item's RoomMenu until the browser is idle. The menu's hooks
+ * (useUserSubscription, usePermission, useSetting, useOmnichannelPrioritiesMenu, useUserPresence)
+ * are not cheap to run synchronously inside the same pointerover/click task as a room navigation,
+ * so we let the browser finish more urgent work first.
+ */
+export const useDeferredMenuMount = () => {
+	const [mounted, setMounted] = useState(typeof window !== 'undefined' && !!window.DISABLE_ANIMATION);
+	const handleRef = useRef<IdleHandle | undefined>(undefined);
+
+	const requestMount = useCallback(() => {
+		if (mounted || handleRef.current !== undefined) {
+			return;
+		}
+		handleRef.current = schedule(() => {
+			handleRef.current = undefined;
+			setMounted(true);
+		});
+	}, [mounted]);
+
+	const mountNow = useCallback(() => {
+		if (handleRef.current !== undefined) {
+			cancel(handleRef.current);
+			handleRef.current = undefined;
+		}
+		setMounted(true);
+	}, []);
+
+	useEffect(
+		() => () => {
+			if (handleRef.current !== undefined) {
+				cancel(handleRef.current);
+				handleRef.current = undefined;
+			}
+		},
+		[],
+	);
+
+	return { mounted, requestMount, mountNow };
+};