Check transforms for skew in C++ on Android

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/SkewMatrixHelper.kt

@@ -8,6 +8,7 @@
 package com.facebook.react.uimanager
 
 import android.graphics.Matrix
+import com.facebook.react.bridge.NativeArray
 import com.facebook.react.bridge.ReadableArray
 import com.facebook.react.bridge.ReadableMap
 import com.facebook.react.bridge.ReadableType
@@ -28,6 +29,10 @@ internal object SkewMatrixHelper {
    */
   @JvmStatic
   fun isAffine2DTransformWithSkew(transforms: ReadableArray): Boolean {
+    // Read Fabric's arrays in C++ rather than crossing JNI for every element and key.
+    if (transforms is NativeArray) {
+      return TransformHelper.isAffine2DTransformWithSkew(transforms)
+    }
     if (isRawMatrixShorthand(transforms)) {
       return false
     }

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/TransformHelper.kt

@@ -237,6 +237,14 @@ public object TransformHelper {
     return doubleArrayOf(newTranslateX, newTranslateY, newTranslateZ)
   }
 
+  /** Native implementation of [SkewMatrixHelper.isAffine2DTransformWithSkew]. */
+  @JvmStatic
+  internal fun isAffine2DTransformWithSkew(transforms: NativeArray): Boolean =
+      nativeIsAffine2DTransformWithSkew(transforms)
+
+  @JvmStatic
+  private external fun nativeIsAffine2DTransformWithSkew(transforms: NativeArray): Boolean
+
   @JvmStatic
   private external fun nativeProcessTransform(
       transforms: NativeArray,

packages/react-native/ReactAndroid/src/main/jni/react/jni/TransformHelper.cpp

@@ -51,11 +51,49 @@ void processTransform(
   jResult->setRegion(0, MatrixSize, doubleTransform.data());
 }
 
+// Same result as SkewMatrixHelper.isAffine2DTransformWithSkew, but reads the
+// array in place instead of crossing JNI for each element and key.
+jboolean isAffine2DTransformWithSkew(
+    jni::alias_ref<jclass> /*unused*/,
+    NativeArray* jTransforms) {
+  const auto& transforms = jTransforms->getArray();
+  // The raw 16-element matrix shorthand used by Fabric LayoutAnimations.
+  if (transforms.size() == 16 && transforms[0].isNumber()) {
+    return JNI_FALSE;
+  }
+  bool hasSkewTransform = false;
+  for (const auto& transform : transforms) {
+    if (!transform.isObject() || transform.empty()) {
+      continue;
+    }
+    const auto& [key, value] = *transform.items().begin();
+    if (!key.isString()) {
+      continue;
+    }
+    const auto& type = key.getString();
+    if (type == "matrix" || type == "perspective" || type == "rotateX" ||
+        type == "rotateY") {
+      return JNI_FALSE;
+    }
+    if (type == "translate") {
+      if (value.isArray() && value.size() > 2 && value[2].isNumber() &&
+          value[2].asDouble() != 0.0) {
+        return JNI_FALSE;
+      }
+    } else if (type == "skewX" || type == "skewY") {
+      hasSkewTransform = true;
+    }
+  }
+  return hasSkewTransform ? JNI_TRUE : JNI_FALSE;
+}
+
 } // namespace
 
 void TransformHelper::registerNatives() {
   javaClassLocal()->registerNatives({
       makeNativeMethod("nativeProcessTransform", processTransform),
+      makeNativeMethod(
+          "nativeIsAffine2DTransformWithSkew", isAffine2DTransformWithSkew),
   });
 }