Set and require android:supportsRtl="true" for RTL layout

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/modules/i18nmanager/I18nUtil.java

@@ -9,19 +9,30 @@
 
 import android.content.Context;
 import android.content.SharedPreferences;
+import android.content.pm.ApplicationInfo;
+import androidx.annotation.Nullable;
 import androidx.core.text.TextUtilsCompat;
+import androidx.core.util.Preconditions;
 import androidx.core.view.ViewCompat;
+import com.facebook.common.logging.FLog;
+import com.facebook.infer.annotation.Nullsafe;
+import java.lang.reflect.Method;
 import java.util.Locale;
 
+@Nullsafe(Nullsafe.Mode.LOCAL)
 public class I18nUtil {
-  private static I18nUtil sharedI18nUtilInstance = null;
+  private static @Nullable I18nUtil sharedI18nUtilInstance = null;
 
+  private static final String TAG = "I18nUtil";
   private static final String SHARED_PREFS_NAME = "com.facebook.react.modules.i18nmanager.I18nUtil";
   private static final String KEY_FOR_PREFS_ALLOWRTL = "RCTI18nUtil_allowRTL";
   private static final String KEY_FOR_PREFS_FORCERTL = "RCTI18nUtil_forceRTL";
   private static final String KEY_FOR_PERFS_MAKE_RTL_FLIP_LEFT_AND_RIGHT_STYLES =
       "RCTI18nUtil_makeRTLFlipLeftAndRightStyles";
 
+  private boolean mHasCheckedRtlSupport = false;
+  private boolean mHasRtlSupport = true;
+
   private I18nUtil() {
     // Exists only to defeat instantiation.
   }
@@ -42,19 +53,46 @@ public static I18nUtil getInstance() {
    * </ul>
    */
   public boolean isRTL(Context context) {
+    if (!applicationHasRtlSupport(context)) {
+      return false;
+    }
+
     if (isRTLForced(context)) {
       return true;
     }
+
     return isRTLAllowed(context) && isDevicePreferredLanguageRTL();
   }
 
+  /**
+   * Android relies on the presence of `android:supportsRtl="true"` being set in order to resolve
+   * RTL as a layout direction for native Android views. RTL in React Native relies on this being
+   * set.
+   */
+  private boolean applicationHasRtlSupport(Context context) {
+    if (!mHasCheckedRtlSupport) {
+      mHasCheckedRtlSupport = true;
+      ApplicationInfo applicationInfo = context.getApplicationInfo();
+      try {
+        Method hasRtlSupport = ApplicationInfo.class.getMethod("hasRtlSupport");
+        mHasRtlSupport =
+            Preconditions.checkNotNull((Boolean) hasRtlSupport.invoke(applicationInfo));
+      } catch (ReflectiveOperationException e) {
+        FLog.w(TAG, "Failed to check if application has RTL support");
+      }
+    }
+    return mHasRtlSupport;
+  }
+
   /**
    * Should be used very early during app start up Before the bridge is initialized
    *
    * @return whether the app allows RTL layout, default is true
    */
   private boolean isRTLAllowed(Context context) {
-    return isPrefSet(context, KEY_FOR_PREFS_ALLOWRTL, true);
+    // We should only claim to allow RTL if `android:supportsRtl="true"` is set, otherwise the
+    // platform apart from Yoga ignores layout direction.
+    return applicationHasRtlSupport(context) && isPrefSet(context, KEY_FOR_PREFS_ALLOWRTL, true);
   }
 
   public void allowRTL(Context context, boolean allowRTL) {

packages/react-native/template/android/app/src/main/AndroidManifest.xml

@@ -8,7 +8,8 @@
       android:icon="@mipmap/ic_launcher"
       android:roundIcon="@mipmap/ic_launcher_round"
       android:allowBackup="false"
-      android:theme="@style/AppTheme">
+      android:theme="@style/AppTheme"
+      android:supportsRtl="true">
       <activity
         android:name=".MainActivity"
         android:label="@string/app_name"

packages/rn-tester/android/app/src/main/AndroidManifest.xml

@@ -37,7 +37,8 @@
       android:icon="@mipmap/ic_launcher"
       android:roundIcon="@mipmap/ic_launcher_round"
       android:label="@string/app_name"
-      android:theme="@style/AppTheme">
+      android:theme="@style/AppTheme"
+      android:supportsRtl="true">
     <activity
         android:name=".RNTesterActivity"
         android:label="@string/app_name"