Fix horizontal ScrollView resting past its left edge after a fling on Android 14

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactHorizontalScrollView.kt

@@ -850,7 +850,10 @@ constructor(context: Context, private val fpsListener: FpsListener? = null) :
           velocityX
         }
 
-    if (pagingEnabled) {
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S && scrollX <= 0 && correctedVelocityX < 0) {
+      // From Android 12 the platform absorbs this fling; an overscroll here sticks on Android 14.
+      super.fling(correctedVelocityX)
+    } else if (pagingEnabled) {
       flingAndSnap(correctedVelocityX)
     } else if (scroller != null) {
       // FB SCROLLVIEW CHANGE

packages/react-native/ReactAndroid/src/test/java/com/facebook/react/views/scroll/ReactHorizontalScrollViewFlingTest.kt

@@ -0,0 +1,145 @@
+/*
+ * 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.
+ */
+
+// The deprecated APIs exercised here remain public and required by this Robolectric setup.
+@file:Suppress("DEPRECATION")
+
+package com.facebook.react.views.scroll
+
+import android.annotation.SuppressLint
+import android.os.Build
+import android.os.Looper
+import android.os.SystemClock
+import android.util.DisplayMetrics
+import android.view.MotionEvent
+import android.view.View
+import android.widget.EdgeEffect
+import com.facebook.react.bridge.BridgeReactContext
+import com.facebook.react.bridge.ReactTestHelper.createMockCatalystInstance
+import com.facebook.react.internal.featureflags.ReactNativeFeatureFlagsForTests
+import com.facebook.react.uimanager.DisplayMetricsHolder
+import com.facebook.react.uimanager.ThemedReactContext
+import com.facebook.react.uimanager.UIManagerHelper
+import com.facebook.react.uimanager.events.EventDispatcher
+import com.facebook.soloader.SoLoader
+import java.time.Duration
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.After
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mockito.MockedStatic
+import org.mockito.Mockito.mockStatic
+import org.mockito.kotlin.any
+import org.mockito.kotlin.mock
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.RuntimeEnvironment
+import org.robolectric.Shadows.shadowOf
+import org.robolectric.annotation.Config
+import org.robolectric.annotation.Implementation
+import org.robolectric.annotation.Implements
+
+/** Verifies where a horizontal ScrollView comes to rest after a drag that ends in a fling. */
+@SuppressLint("DeprecatedClass", "DeprecatedMethod")
+@RunWith(RobolectricTestRunner::class)
+@Config(sdk = [34], shadows = [ReactHorizontalScrollViewFlingTest.ShadowStretchEdgeEffect::class])
+class ReactHorizontalScrollViewFlingTest {
+
+  /** Robolectric turns every edge effect off; a device stretches the edge a drag pulls past. */
+  @Implements(EdgeEffect::class)
+  class ShadowStretchEdgeEffect {
+    @Implementation(minSdk = Build.VERSION_CODES.S)
+    fun getCurrentEdgeEffectBehavior(): Int = EDGE_EFFECT_TYPE_STRETCH
+  }
+
+  private lateinit var themedContext: ThemedReactContext
+  private lateinit var uiManagerHelperMock: MockedStatic<UIManagerHelper>
+
+  @Before
+  fun setup() {
+    ReactNativeFeatureFlagsForTests.setUp()
+    SoLoader.setInTestMode()
+    val context = BridgeReactContext(RuntimeEnvironment.getApplication())
+    context.initializeWithInstance(createMockCatalystInstance())
+    themedContext = ThemedReactContext(context, context, null, -1)
+    DisplayMetricsHolder.setScreenDisplayMetrics(DisplayMetrics())
+    uiManagerHelperMock = mockStatic(UIManagerHelper::class.java)
+    uiManagerHelperMock
+        .`when`<EventDispatcher?> { UIManagerHelper.getEventDispatcher(any()) }
+        .thenReturn(mock())
+  }
+
+  @After
+  fun teardown() {
+    uiManagerHelperMock.close()
+    DisplayMetricsHolder.setScreenDisplayMetrics(null)
+  }
+
+  @Test
+  fun testFlingIntoLeftEdgeAtRestStaysAtLeftEdge() {
+    val view = createAtLeftEdge()
+
+    dragAndRelease(view, fromX = DRAG_START_X, toX = DRAG_END_X)
+    settle(view)
+
+    assertThat(view.scrollX).isEqualTo(0)
+  }
+
+  @Test
+  fun testFlingFromLeftEdgeIntoContentScrollsPastTheDrag() {
+    val view = createAtLeftEdge()
+
+    dragAndRelease(view, fromX = DRAG_END_X, toX = DRAG_START_X)
+    settle(view)
+
+    assertThat(view.scrollX).isGreaterThan((DRAG_END_X - DRAG_START_X).toInt())
+  }
+
+  private fun createAtLeftEdge(): ReactHorizontalScrollView {
+    val view = ReactHorizontalScrollViewManager().createViewInstance(themedContext)
+    val content = View(themedContext)
+    view.addView(content)
+    content.layout(0, 0, CONTENT_WIDTH, VIEWPORT_SIZE)
+    view.layout(0, 0, VIEWPORT_SIZE, VIEWPORT_SIZE)
+    assertThat(view.scrollX).isEqualTo(0)
+    return view
+  }
+
+  private fun dragAndRelease(view: ReactHorizontalScrollView, fromX: Float, toX: Float) {
+    val downTime = SystemClock.uptimeMillis()
+    val stepX = (toX - fromX) / DRAG_STEPS
+    view.onTouchEvent(obtainTouch(downTime, 0, MotionEvent.ACTION_DOWN, fromX))
+    for (step in 1 until DRAG_STEPS) {
+      view.onTouchEvent(obtainTouch(downTime, step, MotionEvent.ACTION_MOVE, fromX + stepX * step))
+    }
+    view.onTouchEvent(obtainTouch(downTime, DRAG_STEPS, MotionEvent.ACTION_UP, toX))
+  }
+
+  private fun obtainTouch(downTime: Long, step: Int, action: Int, x: Float): MotionEvent =
+      MotionEvent.obtain(downTime, downTime + step * STEP_MILLIS, action, x, TOUCH_Y, 0)
+
+  private fun settle(view: ReactHorizontalScrollView) {
+    repeat(SETTLE_FRAMES) {
+      shadowOf(Looper.getMainLooper()).idleFor(Duration.ofMillis(FRAME_MILLIS))
+      view.computeScroll()
+    }
+  }
+
+  private companion object {
+    // EdgeEffect.TYPE_STRETCH, which the SDK hides.
+    const val EDGE_EFFECT_TYPE_STRETCH = 1
+    const val VIEWPORT_SIZE = 1000
+    const val CONTENT_WIDTH = 5000
+    const val TOUCH_Y = 500f
+    const val DRAG_START_X = 100f
+    const val DRAG_END_X = 500f
+    const val DRAG_STEPS = 4
+    const val STEP_MILLIS = 10L
+    const val FRAME_MILLIS = 16L
+    const val SETTLE_FRAMES = 180
+  }
+}