Expose ComputePlatformResolvedLocale (flutter#58482)

GaryQian · web-flow · commit 0e735e4bca53 · 2020-06-30T18:54:02.000-07:00
diff --git a/packages/flutter/lib/src/widgets/binding.dart b/packages/flutter/lib/src/widgets/binding.dart
@@ -944,6 +944,46 @@ mixin WidgetsBinding on BindingBase, ServicesBinding, SchedulerBinding, GestureB
       buildOwner.reassemble(renderViewElement);
     return super.performReassemble();
   }
+
+  /// Computes the locale the current platform would resolve to.
+  ///
+  /// This method is meant to be used as part of a [localeListResolutionCallback].
+  /// Since this method may return null, a Flutter/dart algorithm should still be
+  /// provided as a fallback in case a native resolved locale cannot be determined
+  /// or if the native resolved locale is undesirable.
+  ///
+  /// This method may return a null [Locale] if the platform does not support
+  /// native locale resolution, or if the resolution failed.
+  ///
+  /// The first [supportedLocale] is treated as the default locale and will be returned
+  /// if no better match is found.
+  ///
+  /// Android and iOS are currently supported.
+  ///
+  /// On Android, the algorithm described in
+  /// https://developer.android.com/guide/topics/resources/multilingual-support
+  /// is used to determine the resolved locale. Depending on the android version
+  /// of the device, either the modern (>= API 24) or legacy (< API 24) algorithm
+  /// will be used.
+  ///
+  /// On iOS, the result of `preferredLocalizationsFromArray` method of `NSBundle`
+  /// is returned. See:
+  /// https://developer.apple.com/documentation/foundation/nsbundle/1417249-preferredlocalizationsfromarray?language=objc
+  /// for details on the used method.
+  ///
+  /// iOS treats script code as necessary for a match, so a user preferred locale of
+  /// `zh_Hans_CN` will not resolve to a supported locale of `zh_CN`.
+  ///
+  /// Since implementation may vary by platform and has potential to be heavy,
+  /// it is recommended to cache the results of this method if the value is
+  /// used multiple times.
+  ///
+  /// Second-best (and n-best) matching locales should be obtained by calling this
+  /// method again with the matched locale of the first call omitted from
+  /// [supportedLocales].
+  Locale computePlatformResolvedLocale(List<Locale> supportedLocales) {
+    return window.computePlatformResolvedLocale(supportedLocales);
+  }
 }
 
 /// Inflate the given widget and attach it to the screen.
