From be15138681a697529748758b65f1be1a1d346fb5 Mon Sep 17 00:00:00 2001
From: Pieter De Baets <pieterdb@meta.com>
Date: Wed, 24 Jun 2026 06:56:42 -0700
Subject: [PATCH] Add Fantom benchmark for ViewProps cloneProps (#57324)

Summary:

Adds `ViewProps-benchmark-itest.js` covering three scenarios that exercise the C++ Props construction path:

1. Mount N views with a full prop bag (initial Props construction).
2. Re-render N views with a full prop swap (cloneProps, every prop changes).
3. Re-render N views with a single-prop delta (cloneProps, hot path for typical UI updates).

`fantom_flags enableCppPropsIteratorSetter:*` matrix-expands the suite so each scenario runs once with the classic per-field parse and once with the iterator-setter path. This establishes a baseline for upcoming changes that simplify the per-class `flag ? sourceProps.X : convertRawProp(...)` ternaries into two distinct constructors and that skip the now-unused `RawPropsParser::parse()` in the iterator-setter branch.

Changelog:
[Internal]

Differential Revision: D109563268
---
 .../__tests__/ViewProps-benchmark-itest.js    | 172 ++++++++++++++++++
 1 file changed, 172 insertions(+)
 create mode 100644 packages/react-native/Libraries/Components/View/__tests__/ViewProps-benchmark-itest.js

diff --git a/packages/react-native/Libraries/Components/View/__tests__/ViewProps-benchmark-itest.js b/packages/react-native/Libraries/Components/View/__tests__/ViewProps-benchmark-itest.js
new file mode 100644
index 000000000000..0544b9115c2b
--- /dev/null
+++ b/packages/react-native/Libraries/Components/View/__tests__/ViewProps-benchmark-itest.js
@@ -0,0 +1,172 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @fantom_flags enableCppPropsIteratorSetter:*
+ * @flow strict-local
+ * @format
+ */
+
+import '@react-native/fantom/src/setUpDefaultReactNativeEnvironment';
+
+import * as Fantom from '@react-native/fantom';
+import * as React from 'react';
+import {View} from 'react-native';
+
+let root;
+let initialTree: React.MixedElement;
+let updatedTree: React.MixedElement;
+
+function buildViewsWithFullPropBag(
+  count: number,
+  variant: 'a' | 'b',
+): React.MixedElement {
+  const accent = variant === 'a' ? 'blue' : 'red';
+  const offset = variant === 'a' ? 0 : 1;
+  const children = [];
+  for (let i = 0; i < count; i++) {
+    children.push(
+      <View
+        key={i}
+        accessibilityLabelledBy={`label-${i.toString()}`}
+        accessibilityLiveRegion="polite"
+        aria-labelledby={`label-${i.toString()}`}
+        aria-live="polite"
+        collapsable={false}
+        focusable={i % 2 === 0}
+        hasTVPreferredFocus={i % 2 === 0}
+        id={String(i)}
+        importantForAccessibility="no-hide-descendants"
+        nativeID={String(i)}
+        nextFocusDown={i + offset}
+        nextFocusForward={i + 1 + offset}
+        nextFocusLeft={i + 2 + offset}
+        nextFocusRight={i + 3 + offset}
+        nextFocusUp={i + 4 + offset}
+        renderToHardwareTextureAndroid={true}
+        style={{
+          width: i + 1 + offset,
+          height: i + 1 + offset,
+          backgroundColor: accent,
+          borderCurve: 'circular',
+          borderBottomWidth: i % 2 === 0 ? 0 : 1,
+          borderWidth: i % 2 === 0 ? 0 : 1,
+          borderEndWidth: i % 2 === 0 ? 0 : 1,
+          borderLeftWidth: i % 2 === 0 ? 0 : 1,
+          borderRightWidth: i % 2 === 0 ? 0 : 1,
+          borderStartWidth: i % 2 === 0 ? 0 : 1,
+          borderTopWidth: i % 2 === 0 ? 0 : 1,
+          borderBottomColor: accent,
+          borderEndColor: accent,
+          borderStartColor: accent,
+          borderTopColor: accent,
+          borderRightColor: accent,
+          borderLeftColor: accent,
+          opacity: i % 2 === 0 ? 0 : 1,
+          elevation: i % 2 === 0 ? 0 : 1,
+          pointerEvents: 'auto',
+          boxShadow: '0 0 0 1px ' + accent,
+          isolation: 'isolate',
+          cursor: 'pointer',
+          backfaceVisibility: 'visible',
+          mixBlendMode: 'multiply',
+        }}
+        tabIndex={i % 2 === 0 ? 0 : undefined}
+      />,
+    );
+  }
+  return (
+    <View collapsable={false} nativeID="root">
+      {children}
+    </View>
+  );
+}
+
+function buildViewsWithSinglePropDelta(
+  count: number,
+  toggle: boolean,
+): React.MixedElement {
+  const children = [];
+  for (let i = 0; i < count; i++) {
+    children.push(
+      <View
+        key={i}
+        collapsable={false}
+        nativeID={String(i)}
+        style={{
+          width: i + 1,
+          height: i + 1,
+          opacity: toggle && i % 2 === 0 ? 0.5 : 1,
+        }}
+      />,
+    );
+  }
+  return (
+    <View collapsable={false} nativeID="root">
+      {children}
+    </View>
+  );
+}
+
+Fantom.unstable_benchmark
+  .suite('Props construction')
+  .test.each(
+    [100, 1000],
+    n => `mount ${n.toString()} views with full prop bag`,
+    () => {
+      Fantom.runTask(() => root.render(initialTree));
+    },
+    n => ({
+      beforeAll: () => {
+        initialTree = buildViewsWithFullPropBag(n, 'a');
+      },
+      beforeEach: () => {
+        root = Fantom.createRoot();
+      },
+      afterEach: () => {
+        root.destroy();
+      },
+    }),
+  )
+  .test.each(
+    [100, 1000],
+    n => `re-render ${n.toString()} views with full prop swap (cloneProps)`,
+    () => {
+      Fantom.runTask(() => root.render(updatedTree));
+    },
+    n => ({
+      beforeAll: () => {
+        initialTree = buildViewsWithFullPropBag(n, 'a');
+        updatedTree = buildViewsWithFullPropBag(n, 'b');
+      },
+      beforeEach: () => {
+        root = Fantom.createRoot();
+        Fantom.runTask(() => root.render(initialTree));
+      },
+      afterEach: () => {
+        root.destroy();
+      },
+    }),
+  )
+  .test.each(
+    [100, 1000],
+    n => `re-render ${n.toString()} views with single-prop delta (cloneProps)`,
+    () => {
+      Fantom.runTask(() => root.render(updatedTree));
+    },
+    n => ({
+      beforeAll: () => {
+        initialTree = buildViewsWithSinglePropDelta(n, false);
+        updatedTree = buildViewsWithSinglePropDelta(n, true);
+      },
+      beforeEach: () => {
+        root = Fantom.createRoot();
+        Fantom.runTask(() => root.render(initialTree));
+      },
+      afterEach: () => {
+        root.destroy();
+      },
+    }),
+  );