[shubh73]

Summary:

react/yoga#2055 stops zeroOutLayoutRecursively from cloning display: none subtrees that are already zeroed out. Without it, every commit that lays out the parent of a hidden view clones every node under it (yogaNodeCloneCallbackConnector → cloneChildInPlace), and YogaLayoutableShadowNode::layout() never settles those clones because it doesn't descend into display: none. React commits re-run layout along the path to a change, so even a colour change pays it. On Android the differ then walks the freshly cloned subtrees too, since useTraitHiddenOnAndroid is off by default.

The cost grows with every screen kept mounted with display: none:

• <Activity mode="hidden">
• React Navigation 8 (alpha) stack, drawer and custom tabs (ActivityView)
• React Navigation 7 with detachInactiveScreens={false} (Screen.tsx) or freezeOnBlur (react-freeze)
• Expo Router headless tabs (expo-router/ui) (TabSlot.tsx)

#59113 fixed the related case where those subtrees dirtied their ancestors.

The Yoga change reaches React Native through the Yoga sync. This PR adds a Fantom test for it, so it should land after the sync. It's a draft until then.

On an OPPO CPH2667 (Android 16, RNTester release build), with N hidden screens of about 500 nodes each, the change brings the extra time per update to the visible screen at N = 10 from +13.0 ms to +5.9 ms. The details are in react/yoga#2055. Most of what remains is the differ walk that useTraitHiddenOnAndroid skips: with the flag on as well, it's +1.8 ms.

Changelog:

[INTERNAL] [ADDED] - Fantom test for display: none subtrees not being cloned on every commit

Test Plan:

View-hiddenSubtrees-itest.js adds two tests:

• lays out a screen shown again after updates while it was hidden: hidden screens are updated while hidden and then shown, and must lay out the same as screens that were never hidden. This covers resizes around them, content added and removed while hidden, display: contents, nested display: none and non-absolute screens. It passes with and without Don't clone zeroed out display: none subtrees on every layout pass yoga#2055.
• does not clone a hidden subtree when its parent is laid out again: a hidden descendant's ShadowNode revision must stay the same across React commits and a setNativeProps commit that lay out its parent. It fails on main ("Expected 1 but received 3") and passes with Don't clone zeroed out display: none subtrees on every layout pass yoga#2055 applied to the vendored copy.

yarn fantom packages/react-native/Libraries/Components/View/__tests__/View-hiddenSubtrees-itest.js

With react/yoga#2055 applied to the vendored copy and a Debug tester (react_native_assert on), the rest of the Fantom suite doesn't change.

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