Ship "state update scroll race" to ScrollView and HorizontalScrollView

Summary:
As a followup to T91209139, ship "state update scroll race" in code. This also ships it for HorizontalScrollView since it's been validated for vertical scroll views.

Changelog: [Internal]

Reviewed By: sammy-SC

Differential Revision: D29595601

fbshipit-source-id: 64b6a23e2dab2c13123e132d9d899fb769d03172

ReactAndroid/src/main/java/com/facebook/react/config/ReactFeatureFlags.java

@@ -69,17 +69,4 @@ public static boolean isMapBufferSerializationEnabled() {
  public static boolean enableLockFreeEventDispatcher = false;
 
  public static boolean enableAggressiveEventEmitterCleanup = false;
-
- //
- // ScrollView C++ UpdateState vs onScroll race fixes
- //
-
- /* Enables a "state race condition fix" for ScrollViews StateUpdate + onScroll event emitter */
- public static boolean enableScrollViewStateEventRaceFix = false;
-
- /* Enables another "state race condition fix" for ScrollViews StateUpdate + onScroll event emitter. Races a StateUpdate with every onScroll event. */
- public static boolean enableScrollViewStateEventAlwaysRace = false;
-
- /* Configure a min scroll delta for UpdateState to be called while still actively scrolling. */
- public static int scrollViewUpdateStateMinScrollDelta = 0;
 }

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactHorizontalScrollView.java

@@ -417,6 +417,12 @@ protected void onScrollChanged(int x, int y, int oldX, int oldY) {
  updateClippingRect();
  }
 
+ // Race an UpdateState with every onScroll. This makes it more likely that, in Fabric,
+ // when JS processes the scroll event, the C++ ShadowNode representation will have a
+ // "more correct" scroll position. It will frequently be /incorrect/ but this decreases
+ // the error as much as possible.
+ updateStateOnScroll();
+
  ReactScrollViewHelper.emitScrollEvent(
  this,
  mOnScrollDispatchHelper.getXFlingVelocity(),

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java

@@ -30,7 +30,6 @@
 import com.facebook.react.bridge.WritableMap;
 import com.facebook.react.bridge.WritableNativeMap;
 import com.facebook.react.common.ReactConstants;
-import com.facebook.react.config.ReactFeatureFlags;
 import com.facebook.react.uimanager.FabricViewStateManager;
 import com.facebook.react.uimanager.MeasureSpecAssertions;
 import com.facebook.react.uimanager.PixelUtil;
@@ -101,7 +100,6 @@ public class ReactScrollView extends ScrollView
 
  private int mScrollAwayPaddingTop = 0;
 
- private boolean mWaitingForStateUpdateRoundTrip = false;
  private int mLastStateUpdateScrollX = -1;
  private int mLastStateUpdateScrollY = -1;
 
@@ -288,22 +286,16 @@ protected void onScrollChanged(int x, int y, int oldX, int oldY) {
  updateClippingRect();
  }
 
- // Another potential UpdateState vs onScroll fix: race an UpdateState with every onScroll
- // TODO T91209139: if this mechanism works well, port it to HorizontalScrollView
- if (ReactFeatureFlags.enableScrollViewStateEventAlwaysRace) {
-  updateStateOnScroll();
- }
+ // Race an UpdateState with every onScroll. This makes it more likely that, in Fabric,
+ // when JS processes the scroll event, the C++ ShadowNode representation will have a
+ // "more correct" scroll position. It will frequently be /incorrect/ but this decreases
+ // the error as much as possible.
+ updateStateOnScroll();
 
- // TODO T91209139: if this mechanism works well, port it to HorizontalScrollView
- boolean deferEvent =
- ReactFeatureFlags.enableScrollViewStateEventRaceFix
- && (mWaitingForStateUpdateRoundTrip || updateStateOnScroll());
- if (!deferEvent) {
- ReactScrollViewHelper.emitScrollEvent(
- this,
- mOnScrollDispatchHelper.getXFlingVelocity(),
- mOnScrollDispatchHelper.getYFlingVelocity());
- }
+ ReactScrollViewHelper.emitScrollEvent(
+ this,
+ mOnScrollDispatchHelper.getXFlingVelocity(),
+ mOnScrollDispatchHelper.getYFlingVelocity());
  }
  }
 
@@ -1013,23 +1005,6 @@ public void setScrollAwayTopPaddingEnabledUnstable(int topPadding) {
  setRemoveClippedSubviews(mRemoveClippedSubviews);
  }
 
- /**
- * If we know we are sending a State update, we defer emitting scroll events until the State
- * update makes it back to Java. When that happens, we should immediately emit the scroll event.
- */
- void onStateUpdate() {
- mWaitingForStateUpdateRoundTrip = false;
-
- // For now we don't dedupe these - we want to send an event whenever the metrics have changed
- // from the perspective of C++
- if (ReactFeatureFlags.enableScrollViewStateEventRaceFix) {
- ReactScrollViewHelper.emitScrollEvent(
- this,
- mOnScrollDispatchHelper.getXFlingVelocity(),
- mOnScrollDispatchHelper.getYFlingVelocity());
- }
- }
-
  /**
  * Called on any stabilized onScroll change to propagate content offset value to a Shadow Node.
  */
@@ -1043,20 +1018,9 @@ private boolean updateStateOnScroll(final int scrollX, final int scrollY) {
  return false;
  }
 
- // Require a certain delta if we're still scrolling
- if (mActivelyScrolling) {
- int MIN_DELTA_TO_UPDATE_SCROLL_STATE = ReactFeatureFlags.scrollViewUpdateStateMinScrollDelta;
- int deltaX = Math.abs(mLastStateUpdateScrollX - scrollX);
- int deltaY = Math.abs(mLastStateUpdateScrollY - scrollY);
- if (deltaX < MIN_DELTA_TO_UPDATE_SCROLL_STATE && deltaY < MIN_DELTA_TO_UPDATE_SCROLL_STATE) {
- return false;
- }
- }
-
  mLastStateUpdateScrollX = scrollX;
  mLastStateUpdateScrollY = scrollY;
 
- mWaitingForStateUpdateRoundTrip = true;
  forceUpdateState();
 
  return true;

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollViewManager.java

@@ -325,7 +325,6 @@ public void setContentOffset(ReactScrollView view, ReadableMap value) {
  public Object updateState(
  ReactScrollView view, ReactStylesDiffMap props, @Nullable StateWrapper stateWrapper) {
  view.getFabricViewStateManager().setStateWrapper(stateWrapper);
- view.onStateUpdate();
  return null;
  }