Properly calculate alwaysUse24HourFormat on MacOS (flutter/engine#53795)

Moves the implementation if isAlwaysUse24HourFormat from iOS's FlutterViewController internals to common utility, and makes use of it on MacOS in order to return correct value of `alwaysUse24HourFormat`.

This PR partially resolves [#32006](https://github.com/flutter/flutter/issues/32006).

Note that on iOS 16+ and MacOS 13+, there is a new API for obtaining this information: https://developer.apple.com/documentation/foundation/locale/components/3952289-hourcycle. However, to keep things simpler, I wanted to not include changes to the logic.

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

engine/src/flutter/ci/licenses_golden/licenses_flutter

@@ -43580,6 +43580,7 @@ ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterB
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterChannels.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterCodecs.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterDartProject.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterHourFormat.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterMacros.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterTexture.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterBinaryMessengerRelay.h + ../../../flutter/LICENSE
@@ -43588,6 +43589,7 @@ ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterBi
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterChannels.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterChannelsTest.m + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterCodecs.mm + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterHourFormat.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterNSBundleUtils.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterNSBundleUtils.mm + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterStandardCodec.mm + ../../../flutter/LICENSE
@@ -46480,6 +46482,7 @@ FILE: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterBin
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterChannels.h
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterCodecs.h
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterDartProject.h
+FILE: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterHourFormat.h
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterMacros.h
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Headers/FlutterTexture.h
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterBinaryMessengerRelay.h
@@ -46488,6 +46491,7 @@ FILE: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterBina
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterChannels.mm
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterChannelsTest.m
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterCodecs.mm
+FILE: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterHourFormat.mm
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterNSBundleUtils.h
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterNSBundleUtils.mm
 FILE: ../../../flutter/shell/platform/darwin/common/framework/Source/FlutterStandardCodec.mm

engine/src/flutter/shell/platform/darwin/common/BUILD.gn

@@ -85,6 +85,7 @@ source_set("framework_common") {
     "framework/Source/FlutterBinaryMessengerRelay.mm",
     "framework/Source/FlutterChannels.mm",
     "framework/Source/FlutterCodecs.mm",
+    "framework/Source/FlutterHourFormat.mm",
     "framework/Source/FlutterNSBundleUtils.h",
     "framework/Source/FlutterNSBundleUtils.mm",
     "framework/Source/FlutterStandardCodec.mm",

engine/src/flutter/shell/platform/darwin/common/framework/Headers/FlutterHourFormat.h

@@ -0,0 +1,15 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_SHELL_PLATFORM_DARWIN_COMMON_FRAMEWORK_HEADERS_FLUTTERHOURFORMAT_H_
+#define FLUTTER_SHELL_PLATFORM_DARWIN_COMMON_FRAMEWORK_HEADERS_FLUTTERHOURFORMAT_H_
+
+#import <Foundation/Foundation.h>
+
+@interface FlutterHourFormat : NSObject
++ (BOOL)isAlwaysUse24HourFormat;
+
+@end
+
+#endif  // FLUTTER_SHELL_PLATFORM_DARWIN_COMMON_FRAMEWORK_HEADERS_FLUTTERHOURFORMAT_H_

engine/src/flutter/shell/platform/darwin/common/framework/Source/FlutterHourFormat.mm

@@ -0,0 +1,26 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "flutter/shell/platform/darwin/common/framework/Headers/FlutterHourFormat.h"
+
+@implementation FlutterHourFormat
++ (BOOL)isAlwaysUse24HourFormat {
+  // iOS does not report its "24-Hour Time" user setting in the API. Instead, it applies
+  // it automatically to NSDateFormatter when used with [NSLocale currentLocale]. It is
+  // essential that [NSLocale currentLocale] is used. Any custom locale, even the one
+  // that's the same as [NSLocale currentLocale] will ignore the 24-hour option (there
+  // must be some internal field that's not exposed to developers).
+  //
+  // Therefore this option behaves differently across Android and iOS. On Android this
+  // setting is exposed standalone, and can therefore be applied to all locales, whether
+  // the "current system locale" or a custom one. On iOS it only applies to the current
+  // system locale. Widget implementors must take this into account in order to provide
+  // platform-idiomatic behavior in their widgets.
+  NSString* dateFormat = [NSDateFormatter dateFormatFromTemplate:@"j"
+                                                         options:0
+                                                          locale:[NSLocale currentLocale]];
+  return [dateFormat rangeOfString:@"a"].location == NSNotFound;
+}
+
+@end

engine/src/flutter/shell/platform/darwin/common/framework_common.gni

@@ -8,6 +8,7 @@ framework_common_headers =
                     "framework/Headers/FlutterBinaryMessenger.h",
                     "framework/Headers/FlutterChannels.h",
                     "framework/Headers/FlutterCodecs.h",
+                    "framework/Headers/FlutterHourFormat.h",
                     "framework/Headers/FlutterTexture.h",
                     "framework/Headers/FlutterDartProject.h",
                   ],

engine/src/flutter/shell/platform/darwin/ios/framework/Headers/FlutterViewController.h

@@ -11,6 +11,7 @@
 #import "FlutterBinaryMessenger.h"
 #import "FlutterDartProject.h"
 #import "FlutterEngine.h"
+#import "FlutterHourFormat.h"
 #import "FlutterMacros.h"
 #import "FlutterPlugin.h"
 #import "FlutterTexture.h"

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -2158,7 +2158,7 @@ static flutter::PointerData::DeviceKind DeviceKindFromTouchType(UITouch* touch)
 - (void)onUserSettingsChanged:(NSNotification*)notification {
   [[_engine.get() settingsChannel] sendMessage:@{
     @"textScaleFactor" : @([self textScaleFactor]),
-    @"alwaysUse24HourFormat" : @([self isAlwaysUse24HourFormat]),
+    @"alwaysUse24HourFormat" : @([FlutterHourFormat isAlwaysUse24HourFormat]),
     @"platformBrightness" : [self brightnessMode],
     @"platformContrast" : [self contrastMode],
     @"nativeSpellCheckServiceDefined" : @true,
@@ -2232,24 +2232,6 @@ static flutter::PointerData::DeviceKind DeviceKindFromTouchType(UITouch* touch)
   }
 }
 
-- (BOOL)isAlwaysUse24HourFormat {
-  // iOS does not report its "24-Hour Time" user setting in the API. Instead, it applies
-  // it automatically to NSDateFormatter when used with [NSLocale currentLocale]. It is
-  // essential that [NSLocale currentLocale] is used. Any custom locale, even the one
-  // that's the same as [NSLocale currentLocale] will ignore the 24-hour option (there
-  // must be some internal field that's not exposed to developers).
-  //
-  // Therefore this option behaves differently across Android and iOS. On Android this
-  // setting is exposed standalone, and can therefore be applied to all locales, whether
-  // the "current system locale" or a custom one. On iOS it only applies to the current
-  // system locale. Widget implementors must take this into account in order to provide
-  // platform-idiomatic behavior in their widgets.
-  NSString* dateFormat = [NSDateFormatter dateFormatFromTemplate:@"j"
-                                                         options:0
-                                                          locale:[NSLocale currentLocale]];
-  return [dateFormat rangeOfString:@"a"].location == NSNotFound;
-}
-
 // The brightness mode of the platform, e.g., light or dark, expressed as a string that
 // is understood by the Flutter framework. See the settings
 // system channel for more information.

engine/src/flutter/shell/platform/darwin/ios/framework/Source/FlutterViewControllerTest.mm

@@ -10,6 +10,7 @@
 #include "flutter/lib/ui/window/pointer_data.h"
 #import "flutter/lib/ui/window/viewport_metrics.h"
 #import "flutter/shell/platform/darwin/common/framework/Headers/FlutterBinaryMessenger.h"
+#import "flutter/shell/platform/darwin/common/framework/Headers/FlutterHourFormat.h"
 #import "flutter/shell/platform/darwin/common/framework/Headers/FlutterMacros.h"
 #import "flutter/shell/platform/darwin/ios/framework/Headers/FlutterViewController.h"
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterEmbedderKeyResponder.h"
@@ -1335,6 +1336,35 @@ extern NSNotificationName const FlutterViewControllerWillDealloc;
   [mockTraitCollection stopMocking];
 }
 
+- (void)testItReportsAlwaysUsed24HourFormat {
+  // Setup test.
+  id settingsChannel = OCMStrictClassMock([FlutterBasicMessageChannel class]);
+  OCMStub([self.mockEngine settingsChannel]).andReturn(settingsChannel);
+  FlutterViewController* vc = [[FlutterViewController alloc] initWithEngine:self.mockEngine
+                                                                    nibName:nil
+                                                                     bundle:nil];
+  // Test the YES case.
+  id mockHourFormat = OCMClassMock([FlutterHourFormat class]);
+  OCMStub([mockHourFormat isAlwaysUse24HourFormat]).andReturn(YES);
+  OCMExpect([settingsChannel sendMessage:[OCMArg checkWithBlock:^BOOL(id message) {
+                               return [message[@"alwaysUse24HourFormat"] isEqual:@(YES)];
+                             }]]);
+  [vc onUserSettingsChanged:nil];
+  [mockHourFormat stopMocking];
+
+  // Test the NO case.
+  mockHourFormat = OCMClassMock([FlutterHourFormat class]);
+  OCMStub([mockHourFormat isAlwaysUse24HourFormat]).andReturn(NO);
+  OCMExpect([settingsChannel sendMessage:[OCMArg checkWithBlock:^BOOL(id message) {
+                               return [message[@"alwaysUse24HourFormat"] isEqual:@(NO)];
+                             }]]);
+  [vc onUserSettingsChanged:nil];
+  [mockHourFormat stopMocking];
+
+  // Clean up mocks.
+  [settingsChannel stopMocking];
+}
+
 - (void)testItReportsAccessibilityOnOffSwitchLabelsFlagNotSet {
   if (@available(iOS 13, *)) {
     // noop

engine/src/flutter/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h

@@ -12,6 +12,7 @@
 #import "FlutterAppLifecycleDelegate.h"
 #import "FlutterBinaryMessenger.h"
 #import "FlutterDartProject.h"
+#import "FlutterHourFormat.h"
 #import "FlutterMacros.h"
 #import "FlutterPluginRegistrarMacOS.h"
 #import "FlutterTexture.h"

engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine.mm

@@ -964,7 +964,7 @@ static void SetThreadPriority(FlutterThreadPriority priority) {
     @"platformBrightness" : [brightness isEqualToString:@"Dark"] ? @"dark" : @"light",
     // TODO(jonahwilliams): https://github.com/flutter/flutter/issues/32006.
     @"textScaleFactor" : @1.0,
-    @"alwaysUse24HourFormat" : @false
+    @"alwaysUse24HourFormat" : @([FlutterHourFormat isAlwaysUse24HourFormat]),
   }];
 }
 

engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterEngineTest.mm

@@ -1268,6 +1268,44 @@ TEST_F(FlutterEngineTest, DisplaySizeIsInPhysicalPixel) {
   engine = nil;
 }
 
+TEST_F(FlutterEngineTest, ReportsHourFormat) {
+  __block BOOL expectedValue;
+
+  // Set up mocks.
+  id channelMock = OCMClassMock([FlutterBasicMessageChannel class]);
+  OCMStub([channelMock messageChannelWithName:@"flutter/settings"
+                              binaryMessenger:[OCMArg any]
+                                        codec:[OCMArg any]])
+      .andReturn(channelMock);
+  OCMStub([channelMock sendMessage:[OCMArg any]]).andDo((^(NSInvocation* invocation) {
+    __weak id message;
+    [invocation getArgument:&message atIndex:2];
+    EXPECT_EQ(message[@"alwaysUse24HourFormat"], @(expectedValue));
+  }));
+
+  id mockHourFormat = OCMClassMock([FlutterHourFormat class]);
+  OCMStub([mockHourFormat isAlwaysUse24HourFormat]).andDo((^(NSInvocation* invocation) {
+    [invocation setReturnValue:&expectedValue];
+  }));
+
+  id engineMock = CreateMockFlutterEngine(nil);
+
+  // Verify the YES case.
+  expectedValue = YES;
+  EXPECT_TRUE([engineMock runWithEntrypoint:@"main"]);
+  [engineMock shutDownEngine];
+
+  // Verify the NO case.
+  expectedValue = NO;
+  EXPECT_TRUE([engineMock runWithEntrypoint:@"main"]);
+  [engineMock shutDownEngine];
+
+  // Clean up mocks.
+  [mockHourFormat stopMocking];
+  [engineMock stopMocking];
+  [channelMock stopMocking];
+}
+
 }  // namespace flutter::testing
 
 // NOLINTEND(clang-analyzer-core.StackAddressEscape)