From 5d6d938f104492a6096ebc8b2a4ad4dccee1cf74 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Thu, 22 Jan 2026 08:20:09 +0000
Subject: [PATCH] perf: throttle Hero scroll listener with
 requestAnimationFrame

- Implements requestAnimationFrame throttling for the scroll event listener in Hero.tsx
- Adds cleanup for the animation frame on component unmount
- Adds unit tests to verify behavior and throttling logic
---
 src/components/sections/Hero.test.tsx | 135 ++++++++++++++++++++++++++
 src/components/sections/Hero.tsx      |  16 ++-
 2 files changed, 149 insertions(+), 2 deletions(-)
 create mode 100644 src/components/sections/Hero.test.tsx

diff --git a/src/components/sections/Hero.test.tsx b/src/components/sections/Hero.test.tsx
new file mode 100644
index 0000000..540ce68
--- /dev/null
+++ b/src/components/sections/Hero.test.tsx
@@ -0,0 +1,135 @@
+import { render, fireEvent, act, cleanup } from "@testing-library/react";
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { Hero } from "./Hero";
+import { MemoryRouter } from "react-router-dom";
+
+// Mock dependencies
+vi.mock("../../i18n", () => ({
+  useTranslation: () => ({
+    t: {
+      hero: {
+        company: "Test Company",
+        greeting: "Hello",
+        tagline: "Building the Future",
+        rotatingWords: ["Code", "Design"],
+        cta: "Contact Us",
+        ctaSecondary: "About Us",
+        scroll: "Scroll Down",
+      },
+    },
+  }),
+}));
+
+vi.mock("../../hooks", () => ({
+  useTypingEffect: () => ({
+    text: "Code",
+  }),
+}));
+
+vi.mock("../effects", () => ({
+  GradientBlinds: () => <div data-testid="gradient-blinds" />,
+}));
+
+// Mock Link from react-router-dom to avoid needing Router context for just Link,
+// OR just use MemoryRouter in the render. MemoryRouter is safer.
+
+describe("Hero Component", () => {
+  beforeEach(() => {
+    // Reset scroll position
+    window.scrollY = 0;
+    vi.clearAllMocks();
+    vi.useFakeTimers();
+  });
+
+  afterEach(() => {
+    cleanup();
+    vi.useRealTimers();
+  });
+
+  it("renders correctly and shows scroll indicator initially", () => {
+    const { getByText } = render(
+      <MemoryRouter>
+        <Hero />
+      </MemoryRouter>
+    );
+
+    expect(getByText("Test Company")).toBeDefined();
+    expect(getByText("Scroll Down")).toBeDefined();
+  });
+
+  it("hides scroll indicator when scrolled down", () => {
+    const { queryByText } = render(
+      <MemoryRouter>
+        <Hero />
+      </MemoryRouter>
+    );
+
+    expect(queryByText("Scroll Down")).toBeDefined();
+
+    // Simulate scroll
+    act(() => {
+      window.scrollY = 100;
+      window.dispatchEvent(new Event("scroll"));
+      vi.runAllTimers();
+    });
+
+    expect(queryByText("Scroll Down")).toBeNull();
+  });
+
+  it("shows scroll indicator again when scrolled back up", () => {
+    const { queryByText } = render(
+      <MemoryRouter>
+        <Hero />
+      </MemoryRouter>
+    );
+
+    // Initial scroll down
+    act(() => {
+      window.scrollY = 100;
+      window.dispatchEvent(new Event("scroll"));
+      vi.runAllTimers();
+    });
+    expect(queryByText("Scroll Down")).toBeNull();
+
+    // Scroll back up
+    act(() => {
+      window.scrollY = 0;
+      window.dispatchEvent(new Event("scroll"));
+      vi.runAllTimers();
+    });
+    expect(queryByText("Scroll Down")).toBeDefined();
+  });
+
+  it("throttles scroll events using requestAnimationFrame", () => {
+    const rafSpy = vi.spyOn(window, "requestAnimationFrame");
+    render(
+      <MemoryRouter>
+        <Hero />
+      </MemoryRouter>
+    );
+
+    // Trigger multiple scroll events rapidly
+    act(() => {
+      window.scrollY = 10;
+      window.dispatchEvent(new Event("scroll"));
+      window.dispatchEvent(new Event("scroll"));
+      window.dispatchEvent(new Event("scroll"));
+    });
+
+    // Should call rAF only once before timers run (because of ticking flag)
+    expect(rafSpy).toHaveBeenCalledTimes(1);
+
+    // Run timers to reset ticking
+    act(() => {
+      vi.runAllTimers();
+    });
+
+    // Trigger again
+    act(() => {
+      window.dispatchEvent(new Event("scroll"));
+    });
+
+    // Should call rAF again
+    expect(rafSpy).toHaveBeenCalledTimes(2);
+  });
+});
diff --git a/src/components/sections/Hero.tsx b/src/components/sections/Hero.tsx
index 9c185a9..f7855f2 100644
--- a/src/components/sections/Hero.tsx
+++ b/src/components/sections/Hero.tsx
@@ -14,12 +14,24 @@ export function Hero() {
   const [showScrollIndicator, setShowScrollIndicator] = useState(true);
 
   useEffect(() => {
+    let ticking = false;
+    let rafId: number;
+
     const handleScroll = () => {
-      setShowScrollIndicator(window.scrollY < 50);
+      if (!ticking) {
+        rafId = window.requestAnimationFrame(() => {
+          setShowScrollIndicator(window.scrollY < 50);
+          ticking = false;
+        });
+        ticking = true;
+      }
     };
 
     window.addEventListener("scroll", handleScroll, { passive: true });
-    return () => window.removeEventListener("scroll", handleScroll);
+    return () => {
+      window.removeEventListener("scroll", handleScroll);
+      if (rafId) window.cancelAnimationFrame(rafId);
+    };
   }, []);
 
   const { text } = useTypingEffect({
-- 
2.49.1