Define the ScrollView decelerationRate default once

The Android default (0.985, ReactScrollView's initial rate) and the default elsewhere (0.998) were each written twice: in the BaseScrollViewProps member initializer and in a file-static constant for the classic constructor, under two #ifdef ANDROID blocks. BaseScrollViewProps::kDefaultDecelerationRate now holds the default for both. The three Frameworks C++ API snapshots list the new constant.

Author: bartlomiejbloniarz

packages/react-native/ReactCommon/react/renderer/components/scrollview/BaseScrollViewProps.cpp

@@ -15,12 +15,6 @@
 
 namespace facebook::react {
 
-#ifdef ANDROID
-static constexpr Float defaultDecelerationRate = 0.985f;
-#else
-static constexpr Float defaultDecelerationRate = 0.998f;
-#endif
-
 // TODO (T28334063): Consider for codegen.
 BaseScrollViewProps::BaseScrollViewProps(
     const PropsParserContext& context,
@@ -86,7 +80,7 @@ BaseScrollViewProps::BaseScrollViewProps(
           rawProps,
           "decelerationRate",
           sourceProps.decelerationRate,
-          defaultDecelerationRate)),
+          kDefaultDecelerationRate)),
       endDraggingSensitivityMultiplier(convertRawProp(
           context,
           rawProps,

packages/react-native/ReactCommon/react/renderer/components/scrollview/BaseScrollViewProps.h

@@ -43,10 +43,11 @@ class BaseScrollViewProps : public ViewProps {
   bool automaticallyAdjustKeyboardInsets{false};
 #ifdef ANDROID
   // ReactScrollView's initial rate.
-  Float decelerationRate{0.985f};
+  static constexpr Float kDefaultDecelerationRate = 0.985f;
 #else
-  Float decelerationRate{0.998f};
+  static constexpr Float kDefaultDecelerationRate = 0.998f;
 #endif
+  Float decelerationRate{kDefaultDecelerationRate};
   Float endDraggingSensitivityMultiplier{1};
   bool directionalLockEnabled{};
   ScrollViewIndicatorStyle indicatorStyle{};

scripts/cxx-api/api-snapshots/ReactAndroidFrameworksCxx.api

@@ -1433,6 +1433,7 @@ class facebook::react::BaseScrollViewProps : public facebook::react::HostPlatfor
   public facebook::react::Point contentOffset;
   public facebook::react::ScrollViewIndicatorStyle indicatorStyle;
   public facebook::react::ScrollViewKeyboardDismissMode keyboardDismissMode;
+  public static constexpr facebook::react::Float kDefaultDecelerationRate;
   public std::optional<facebook::react::ScrollViewMaintainVisibleContentPosition> maintainVisibleContentPosition;
   public std::optional<facebook::react::ScrollViewSnapToAlignment> snapToAlignment;
   public std::vector<facebook::react::Float> snapToOffsets;

scripts/cxx-api/api-snapshots/ReactAppleFrameworksCxx.api

@@ -4030,6 +4030,7 @@ class facebook::react::BaseScrollViewProps : public facebook::react::HostPlatfor
   public facebook::react::Point contentOffset;
   public facebook::react::ScrollViewIndicatorStyle indicatorStyle;
   public facebook::react::ScrollViewKeyboardDismissMode keyboardDismissMode;
+  public static constexpr facebook::react::Float kDefaultDecelerationRate;
   public std::optional<facebook::react::ScrollViewMaintainVisibleContentPosition> maintainVisibleContentPosition;
   public std::optional<facebook::react::ScrollViewSnapToAlignment> snapToAlignment;
   public std::vector<facebook::react::Float> snapToOffsets;

scripts/cxx-api/api-snapshots/ReactCommonFrameworksCxx.api

@@ -776,6 +776,7 @@ class facebook::react::BaseScrollViewProps : public facebook::react::HostPlatfor
   public facebook::react::Point contentOffset;
   public facebook::react::ScrollViewIndicatorStyle indicatorStyle;
   public facebook::react::ScrollViewKeyboardDismissMode keyboardDismissMode;
+  public static constexpr Float kDefaultDecelerationRate;
   public std::optional<facebook::react::ScrollViewMaintainVisibleContentPosition> maintainVisibleContentPosition;
   public std::optional<facebook::react::ScrollViewSnapToAlignment> snapToAlignment;
   public std::vector<Float> snapToOffsets;