Samuel Susla

Downgrade offscreen Fabric image requests to prefetch (#56976) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/56976 changelog: [internal] Use Fabric layout data to classify image shadow nodes as visible or offscreen on Apple platforms. Offscreen image requests now use `ImageRequestPriority::Prefetch`, which is bridged to the existing `RCTImageLoaderPriorityPrefetch` API, while visible images stay at `Immediate`. The new React Native feature flag defaults to `false` until app-specific gating wires it up. Reviewed By: javache Differential Revision: D106074485 fbshipit-source-id: 80ece75cf0d639be1fdbfdd5f19b838b7b64aba6

Clear RuntimeScheduler queues on error (#56892) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/56892 changelog: [internal] Add `enableRuntimeSchedulerQueueClearingOnError` and use it in `RuntimeScheduler_Modern` to clear pending tasks, pending rendering updates, and pending surface IDs before forwarding task or microtask errors to `onTaskError`. Update `SchedulerDelegateInvalidationTest` so `enableSchedulerDelegateInvalidation` can be disabled while the new queue-clearing flag is enabled, proving that stale rendering updates and queued follow-up tasks are dropped after an error. Reviewed By: christophpurrer Differential Revision: D105696366 fbshipit-source-id: 24aa04a8084fb1534bb85785558b503bb8cf619c

Add fixYogaFlexBasisFitContentInMainAxis flag to avoid unnecessary re-measurement (#55897) Summary: X-link: https://github.com/facebook/yoga/pull/1909 Pull Request resolved: https://github.com/facebook/react-native/pull/55897 changelog: [internal] this change is gated. ## Problem When Yoga computes flex basis for container children, the legacy behavior applies a `FitContent` constraint in the **main axis**, bounding the child's measurement by the parent's available space. This creates a dependency between the child's flex basis and the parent's content-determined size, causing **unnecessary re-measurement and cascading ownership clones** when siblings change size. ### The re-measurement cascade (before fix) ``` ScrollView (overflow: scroll) +-------------------------------+ | Content Container (auto h) | | +---------------------------+ | | | Item A h=200 | | <-- Item A height changes | +---------------------------+ | | | Item B h=300 | | | +---------------------------+ | | | Item C h=150 | | | +---------------------------+ | +-------------------------------+ | v Content container height changes (200+300+150 = 650) | v FitContent(650) re-measures ALL items <-- PROBLEM | because their flex basis was FitContent(old_height) v Cascading clones of the entire subtree ``` With the legacy `FitContent` in the main axis, each item's flex basis is `min(content, parent_height)`. When Item A changes height, the content container's height changes, which invalidates the FitContent constraint for ALL items, triggering a full re-measurement cascade. ### After fix (MaxContent in main axis) ``` ScrollView (overflow: scroll) +-------------------------------+ | Content Container (auto h) | | +---------------------------+ | | | Item A h=200 -> 250 | | <-- Item A height changes | +---------------------------+ | | | Item B h=300 | | <-- NOT re-measured (basis unchanged) | +---------------------------+ | | | Item C h=150 | | <-- NOT re-measured (basis unchanged) | +---------------------------+ | +-------------------------------+ | v Content container height changes (250+300+150 = 700) | v Only Item A is re-measured. B and C keep their MaxContent flex basis (independent of parent height). ``` With `MaxContent`, each item's flex basis is its intrinsic content size, independent of the parent. Changing one item doesn't invalidate siblings. ## Solution This diff adds a `FlexBasisFitContentInMainAxis` errata bit gated by the `fixYogaFlexBasisFitContentInMainAxis` feature flag. When the fix is active, flex basis measurement uses `MaxContent` (unbounded) instead of `FitContent` for container children in the main axis. ### Three check points in `computeFlexBasisForChild` ``` computeFlexBasisForChild(parent, child) | |-- Check 1: Accept positive flex basis when mainAxisSize is NaN | (fixes flexBasis:200 items in ScrollView getting height 0) | |-- Check 2: FitContent vs MaxContent constraint | +--------------------------------------------------+ | | Parent type | Legacy (errata) | Fix | | |--------------------+-----------------+-----------| | | Auto height | FitContent | MaxContent| <-- key change | | Definite height | FitContent | FitContent| <-- preserved | | Scroll container | MaxContent | MaxContent| <-- unchanged | | Text child (any) | FitContent | FitContent| <-- preserved | +--------------------------------------------------+ | |-- Check 3: ownerHeightForChildren fallback (preserves percentage resolution when availableInnerHeight is NaN) ``` ### Why definite-height parents keep FitContent Yoga's default `flexShrink` is 0 (unlike CSS's default of 1). Without FitContent, a child measured at MaxContent would get a flex basis equal to its full content height and never shrink to fit: ``` View (height: 760) View (height: 760) +-------------------+ +-------------------+ | Wrapper (auto h) | | Wrapper (auto h) | | +-----------+ | | +-----------+-----|----+ | | ScrollView| | | | ScrollView| | | | | content: | | | | content: | | | | | 1800px | | | | 1800px | | | | +-----------+ | | | | | | | h=760 (bounded) | | +-----------+ | | +-------------------+ +---|---------+-----|----+ FitContent: wrapper=760 | h=1800 (overflows!) ScrollView can scroll MaxContent: wrapper=1800 flexShrink=0, no shrinking ScrollView frame=1800=content scrollable range = 0! ``` For **definite-height** parents, FitContent is safe (the parent's size is fixed, so no re-measurement cascade). For **auto-height** parents, MaxContent is used to avoid the cascade. ### Percentage resolution preservation (Check 3) When MaxContent is used, `availableInnerHeight` becomes NaN. This would break percentage-height grandchildren. Check 3 derives a definite `ownerHeightForChildren` from the parent-provided `ownerHeight`: ``` View (height: 844) +---------------------------+ | Wrapper (auto h) | availableInnerHeight = NaN (MaxContent) | ownerHeight = 844 | ownerHeightForChildren = 844 (from Check 3) | +-----+ +-----------+ | | |h:500| |h:'50%' | | 50% resolves against 844, not NaN | | | |= 422 | | | +-----+ +-----------+ | +---------------------------+ ``` Children of scroll containers skip this fallback (scroll content is intentionally unbounded). Reviewed By: javache Differential Revision: D94658492 fbshipit-source-id: 1587151670803ace0eae2ee91883fe4be72bfa27

Move View.js prop transformations to C++ prop parsing (#55853) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/55853 Changelog: [Internal] `View.js` previously transformed `aria-*` props to `accessibility*` equivalents, `id` to `nativeID`, and `tabIndex` to `focusable` in JavaScript before passing to the native component. This diff moves all those transformations to the C++ prop parsing layer (`AccessibilityProps::setProp`, `Props::setProp`, and `HostPlatformViewProps::setProp`), making the JS wrapper thinner and faster. ## Benchmark Results (View vs ViewNativeComponent) | Component | Before (median ns) | After (median ns) | Change | | View | 666,750 | 546,917 | **-18%** | This change is gated for safe rollout. Reviewed By: javache, NickGerleman Differential Revision: D94219577 fbshipit-source-id: 6dee071a2a8caea533dbedd21a2294aec38307f2

Pre-allocate mutation vectors in Differentiator to reduce reallocation overhead (#55819) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/55819 Changelog: [Internal] speed up differentiator | Test | Before (ms) | After (ms) | Improvement | |-------------------------------|-------------|------------|-------------| | 100 uncollapsable views | 3.0 | 2.7 | +10% | | 1000 uncollapsable views | 91.1 | 50.5 | +45% | | 100 views w/ many props | 9.8 | 9.2 | +6% | | 1000 views w/ many props | 147.4 | 116.7 | +21% | | 1500 views w/ many props | 143.1 | 136.7 | +5% | Reviewed By: mdvacca Differential Revision: D94096006 fbshipit-source-id: 024072e12fc7ba7969ce0ca6969ba8895f38ea15

Re-land: fixYogaFlexBasisFitContentInMainAxis (#56064) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/56064 X-link: https://github.com/facebook/yoga/pull/1917 Re-land of D94658492 with fixes, which was reverted in D95669495. ## Context D94658492 added the `fixYogaFlexBasisFitContentInMainAxis` flag to avoid unnecessary re-measurement cascades in Yoga. When Yoga computes flex basis for container children, the legacy behavior applies a `FitContent` constraint in the main axis, bounding the child's measurement by the parent's available space. This creates a dependency between the child's flex basis and the parent's content-determined size — when one sibling changes size, all siblings get re-measured and their shadow nodes get cloned unnecessarily. The fix switches from `FitContent` to `MaxContent` for non-measure container children under auto-height parents, making each child's flex basis independent of the parent's size. ## What went wrong D94658492 modeled the fix as a `YogaErrata` bit (`FLEX_BASIS_FIT_CONTENT_IN_MAIN_AXIS`). Errata flags are bitmasks, and apps that opt into `ALL` or `CLASSIC` errata (like IGVR and Airwave) inadvertently picked up the new behavior without explicitly enabling the feature flag, causing breakages. ## What changed in this re-land This diff models the fix as a `YogaExperimentalFeature` (`FIX_FLEX_BASIS_FIT_CONTENT`) instead of a `YogaErrata` bit. Experimental features are individually opt-in, so existing apps won't accidentally pick up the change. This diff only wires up the RN feature flag infrastructure (flag defaults to `false`). The iOS MobileConfig override and the Yoga layout logic will be landed in follow-up diffs. changelog: [internal] Reviewed By: javache, NickGerleman Differential Revision: D95852922 fbshipit-source-id: e2b1aa7a5d8f340011123679f721c62396b5caa5

Remove native View prop transformation flag (#56699) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/56699 Remove the `enableNativeViewPropTransformations` React Native feature flag and the native prop parsing code paths it controlled. Keep `View.js` performing the existing JS-side `aria-*`, `id`, and `tabIndex` prop transformations unconditionally. Changelog: [General][Removed] - Remove the experimental native View prop transformation feature flag. Reviewed By: javache Differential Revision: D104024823 fbshipit-source-id: 78b4d2d19fe3661a1b68c2456c7bc8605289ef04

Replace TinyMap with std::unordered_map in Differentiator (#55680) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/55680 changelog: [internal] Replace TinyMap<Tag, X> with std::unordered_map<Tag, X>. There is no detectable regression in performance and code is simpler, let's remove TinyMap. ``` ┌────────────────────────────┬──────────────────┬───────────────────────────────────┬───────────────┐ │ Benchmark │ TinyMap (before) │ unordered_map + ctor size (after) │ Change │ ├────────────────────────────┼──────────────────┼───────────────────────────────────┼───────────────┤ │ 100 uncollapsable views │ 1,499,917 ns │ 1,343,333 ns │ -10.4% │ ├────────────────────────────┼──────────────────┼───────────────────────────────────┼───────────────┤ │ 1000 uncollapsable views │ 52,148,021 ns │ 44,131,792 ns │ -15.4% │ ├────────────────────────────┼──────────────────┼───────────────────────────────────┼───────────────┤ │ 100 views large props │ 5,131,292 ns │ 4,529,937 ns │ -11.7% │ ├────────────────────────────┼──────────────────┼───────────────────────────────────┼───────────────┤ │ 1000 views large props │ 82,706,813 ns │ 84,334,167 ns │ +2.0% (noise) │ ├────────────────────────────┼──────────────────┼───────────────────────────────────┼───────────────┤ │ 1500 views large props │ 61,470,542 ns │ 62,976,646 ns │ +2.5% (noise) │ ├────────────────────────────┼──────────────────┼───────────────────────────────────┼───────────────┤ │ deep (depth=5, breadth=4) │ 32,672,583 ns │ 30,700,542 ns │ -6.0% │ ├────────────────────────────┼──────────────────┼───────────────────────────────────┼───────────────┤ │ deep (depth=7, breadth=3) │ 78,523,542 ns │ 74,121,729 ns │ -5.6% │ ├────────────────────────────┼──────────────────┼───────────────────────────────────┼───────────────┤ │ deep (depth=10, breadth=2) │ 48,328,562 ns │ 45,702,188 ns │ -5.4% │ └────────────────────────────┴──────────────────┴───────────────────────────────────┴───────────────┘ ``` Reviewed By: NickGerleman Differential Revision: D90346356 fbshipit-source-id: 90a26da056202d75bc74fec0ed00439a8dbf16cb

Expand Fantom integration tests for FlatList coverage (#55930) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/55930 Expand FlatList Fantom tests to improve FlatList.js code coverage from 44% to 62% line coverage. Changelog: [Internal] Reviewed By: zeyap Differential Revision: D94361042 fbshipit-source-id: 4923886eb7adfa5e5513e1e0a58c6b6f6ff72a2a

Ship useUnorderedMapInDifferentiator (#56918) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/56918 changelog: [internal] the experiment was neutral, let's ship it to simplify code Reviewed By: javache Differential Revision: D105943424 fbshipit-source-id: 3ff2ed1dbcb85f640305c4fcb2485db0a8a312fc

Back out "Add fixYogaFlexBasisFitContentInMainAxis flag to avoid unnecessary re-measurement" (#55989) Summary: changelog: [internal] Pull Request resolved: https://github.com/facebook/react-native/pull/55989 X-link: https://github.com/facebook/yoga/pull/1912 Original commit changeset: 158715167080 Original Phabricator Diff: D94658492 Reviewed By: NickGerleman Differential Revision: D95669495 fbshipit-source-id: a11d59c14521749986271815da535fab7e4a144b

Hoist regex patterns to module-level in StyleSheet processors (#56022) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/56022 Changelog: [Internal] Hoist inline regex patterns to module-level constants in processFilter.js, processBackgroundImage.js, and processTransformOrigin.js to avoid repeated regex compilation on each function call. Fantom benchmark results (p50 latency, optimized build). | Benchmark | Before | After | Improvement | |---|---|---|---| | 100 views with filter strings | 4.427ms | 3.556ms | 24.48% faster | | 500 views with filter strings | 22.523ms | 17.861ms | 26.10% faster | | 100 views with boxShadow strings | 5.835ms | 5.729ms | 1.85% faster | | 500 views with boxShadow strings | 29.914ms | 28.846ms | 3.70% faster | | 100 views with transformOrigin strings | 2.521ms | 2.512ms | 0.36% faster | | 500 views with transformOrigin strings | 12.706ms | 12.421ms | 2.30% faster | Reviewed By: javache Differential Revision: D95853070 fbshipit-source-id: 788a656fcc626fe0da73fa689298114e53f3b031

Add getDefinedEventHandlers API (#55861) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/55861 Add `Fantom.getDefinedEventHandlers(element)` which returns the names of event handlers registered on a component. It Reads committed memoizedProps from the React fiber, so it works for any component type — including component-specific events like ScrollView's onScroll. The alternative we considered was reading the ViewEvents bitmap from `BaseViewProps` in the ShadowNode (C++). That approach only covers View-specific touch/pointer events and onLayout; it misses component-specific events dispatched imperatively (e.g. ScrollView's onScroll), requiring a separate codepath per component type. Changelog: [Internal] Reviewed By: javache Differential Revision: D94936370 fbshipit-source-id: f48b6e37a9e7cf252f396db69e1a43ecca82db96

Optimize processBoxShadow with pre-compiled regex patterns (#55825) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/55825 changelog: [internal] Hoist regex patterns to module-level constants to avoid recompiling them on every function call. This optimization targets a hotspot identified via JS sampling profiler. Benchmark results show 6-7% improvement in "views with large props and styles" tests: - render 100 views with large props/styles: 9.48ms → 8.89ms (-6.2%) - render 1500 views with large props/styles: 137.2ms → 127.5ms (-7.0%) Reviewed By: javache, NickGerleman Differential Revision: D92153667 fbshipit-source-id: d4cd98d34e968b2cea5a491ede4ed727273708cd

fix a regression introduced by fixYogaFlexBasisFitContentInMainAxis feature flag (#56839) Summary: X-link: https://github.com/facebook/yoga/pull/1962 Pull Request resolved: https://github.com/facebook/react-native/pull/56839 changelog: [internal] Limit the FixFlexBasisFitContent height optimization to non-measure container children inside scroll subtrees. This keeps Marketplace Home wrappers outside the ScrollView viewport-bounded while preserving the scroll remeasurement optimization. This regression was discovered during a recent QE where I tried to run enable this optimisation. Reviewed By: christophpurrer Differential Revision: D105167981 fbshipit-source-id: bc988005507ebc1fc1688a8dc77c233e12ac2834

migrate SectionList from jest to Fantom (#55834) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/55834 Migrate SectionList tests from Jest to Fantom. Changelog: [Internal] Reviewed By: huntie Differential Revision: D94887790 fbshipit-source-id: 476161ed73784e450c1ef222e1700612970d1af5

Fix Fantom getRenderedOutput not reflecting removed props (#55891) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/55891 `RenderOutput::renderView` merged old cached props with new debug props via `mergeDynamicProps`. Since `getDebugProps()` omits default-valued props, removed props were never cleared from the cache. Also, `renderedViews_.insert()` never overwrote existing entries. Changelog: [Internal] Reviewed By: javache Differential Revision: D95055704 fbshipit-source-id: 6cdcbde0473a1d03785f49a9eac79be18395a0bf

Add reset tests for View prop transformations (#55893) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/55893 add tests to validate that aria-* props are set back to default correctly when set to undefined Changelog: [Internal] Reviewed By: javache Differential Revision: D95061571 fbshipit-source-id: c035132638fe7223ef544fb422c1a12f57c5fdb6

Add tests for aria- props (#55851) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/55851 Changelog: [Internal] just missing tests Reviewed By: javache Differential Revision: D94904120 fbshipit-source-id: fb73fc92e0ea30b3e37a1fd5725d3bec1b89fb1f

Add image request priority debug overlay (#56970) Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/56970 changelog: [internal] Add an opt-in `RCT_IMAGE_REQUEST_PRIORITY_DEBUG_OVERLAY` label for Fabric image component views so local debugging can show whether an image request is using immediate priority or the offscreen prefetch path. Reviewed By: christophpurrer Differential Revision: D106363533 fbshipit-source-id: ae68c9a5849dc6507f7611e02c217b674f899bd6