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PlatformColor lazy fallback: honor a raw-color fallback on Android (native)#57655

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Abbondanzo:export-D113329136
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PlatformColor lazy fallback: honor a raw-color fallback on Android (native)#57655
Abbondanzo wants to merge 2 commits into
react:mainfrom
Abbondanzo:export-D113329136

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Summary:
An implementation for the RFC in react-native-community/discussions-and-proposals#1008

Wires up the Android native color resolvers (Fabric and Paper) to honor the lazy {fallback} carried by PlatformColor(...). A later diff adds the JS argument that emits it, so on its own this change is a no-op for existing call sites.

To tell a genuine miss apart from a token that resolves to transparent black (ARGB 0):

  • FabricUIManager.getColor now returns a boxed Nullable Integernull means no resource path resolved. The Fabric C++ PlatformColorParser.h reads that boxed result over JNI, caches the explicit-miss signal, and on a miss parses the raw fallback string. The color object is now read as a map<string, RawValue> because it mixes an array (resource_paths) with an optional string (fallback).
  • On the Paper path, ColorPropConverter parses the raw fallback string when every resource path misses, and degrades to transparent (rather than crashing) when a fallback is present but unparseable.
  • NativeDrawable carries an optional colorFallback alongside resource_paths so ripple drawables degrade to the fallback too.

The fallback string parser accepts #RGB/#RGBA/#RRGGBB/#RRGGBBAA (alpha last, as in CSS and iOS — not Android's native #AARRGGBB), rgb()/rgba(), and named colors. rgb()/rgba() require exactly 3 / 4 components respectively, matching the CSS parser used on the iOS Fabric path, so lenient inputs are rejected consistently across platforms. Unknown named colors return quietly rather than logging on every resolve.

Generated files (ReactAndroid.api and the ReactAndroid*Cxx.api snapshots) are regenerated to match the new public signatures.

Changelog:
[Internal] - PlatformColor: Android native support for a lazy raw-color fallback

Differential Revision: D113329136

…cOS (native)

Summary:
This is the first diff in a stack that adds an optional trailing `{fallback: '<raw color string>'}` argument to `PlatformColor(...)`. The fallback is carried lazily to native and parsed only when every supplied color token fails to resolve. This diff wires up the iOS and macOS native color resolvers to honor that fallback; a later diff adds the JS argument that emits it, so on its own this change is a no-op for existing call sites.

To distinguish a genuine miss (no token resolves) from a token that legitimately resolves to a transparent color, the semantic-color resolver gains an `OrNil` variant:

- `RCTPlatformColorFromSemanticItemsOrNil` returns `nil` on a miss instead of collapsing to `clearColor`. `RCTPlatformColorFromSemanticItems` keeps its existing non-null contract by wrapping the `OrNil` variant.
- On Fabric, `Color::createSemanticColor` returns the undefined-color sentinel (a null underlying `UIColor`) on a miss, so `PlatformColorParser.mm` can apply the fallback only on a true miss and otherwise render transparent exactly as before.
- The fallback string is parsed with the shared CSS color parser (`parseCSSProperty<CSSColor>`), so `transparent`/`rgba(0,0,0,0)` are honored rather than mistaken for a parse failure.
- On the iOS Paper (legacy) path, `RCTConvert.mm` parses the common hex forms (`#RGB`, `#RGBA`, `#RRGGBB`, `#RRGGBBAA`, alpha last) as the fallback when every semantic name misses.

This spans the `xplat` iOS/macOS graphics resolvers and the vendored `third-party/react-native-macos` copies.

Changelog:
[Internal] - PlatformColor: iOS/macOS native support for a lazy raw-color fallback

Differential Revision: D111837102
…ative)

Summary:
An implementation for the RFC in react-native-community/discussions-and-proposals#1008

Wires up the Android native color resolvers (Fabric and Paper) to honor the lazy `{fallback}` carried by `PlatformColor(...)`. A later diff adds the JS argument that emits it, so on its own this change is a no-op for existing call sites.

To tell a genuine miss apart from a token that resolves to transparent black (ARGB 0):

- `FabricUIManager.getColor` now returns a boxed `Nullable Integer` — `null` means no resource path resolved. The Fabric C++ `PlatformColorParser.h` reads that boxed result over JNI, caches the explicit-miss signal, and on a miss parses the raw fallback string. The color object is now read as a `map<string, RawValue>` because it mixes an array (`resource_paths`) with an optional string (`fallback`).
- On the Paper path, `ColorPropConverter` parses the raw fallback string when every resource path misses, and degrades to transparent (rather than crashing) when a fallback is present but unparseable.
- `NativeDrawable` carries an optional `colorFallback` alongside `resource_paths` so ripple drawables degrade to the fallback too.

The fallback string parser accepts `#RGB`/`#RGBA`/`#RRGGBB`/`#RRGGBBAA` (alpha last, as in CSS and iOS — not Android's native `#AARRGGBB`), `rgb()`/`rgba()`, and named colors. `rgb()`/`rgba()` require exactly 3 / 4 components respectively, matching the CSS parser used on the iOS Fabric path, so lenient inputs are rejected consistently across platforms. Unknown named colors return quietly rather than logging on every resolve.

Generated files (`ReactAndroid.api` and the `ReactAndroid*Cxx.api` snapshots) are regenerated to match the new public signatures.

Changelog:
[Internal] - PlatformColor: Android native support for a lazy raw-color fallback

Differential Revision: D113329136
@meta-cla meta-cla Bot added the CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. label Jul 23, 2026
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meta-codesync Bot commented Jul 23, 2026

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@Abbondanzo has exported this pull request. If you are a Meta employee, you can view the originating Diff in D113329136.

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