Add in-app language picker to App Settings

ApplicationLibrary/Views/Setting/MacAppView.swift

@@ -7,16 +7,21 @@ import SwiftUI
 #endif
 
 public struct AppView: View {
-    @State private var isLoading = true
+    private static let supportedLanguages: [(code: String?, name: String)] = [
+        (nil, String(localized: "System Default")),
+        ("en", "English"),
+        ("zh-Hans", "简体中文"),
+    ]
 
+    @State private var isLoading = true
+    @State private var selectedLanguage: String?
+
+    #if os(macOS)
         @State private var startAtLogin = false
         @Environment(\.showMenuBarExtra) private var showMenuBarExtra
         @Environment(\.menuBarExtraSpeedMode) private var menuBarExtraSpeedMode
         @State private var menuBarExtraInBackground = false
-    #if os(macOS)
-
         @State private var rootHelperRegistrationStatus: SMAppService.Status = .notRegistered
-
     #endif
 
     @State private var alert: AlertState?
@@ -32,6 +37,15 @@ public struct AppView: View {
                 }
             } else {
                 FormView {
+                    Picker("Language", selection: $selectedLanguage) {
+                        ForEach(Self.supportedLanguages, id: \.code) { language in
+                            Text(language.name).tag(language.code)
+                        }
+                    }
+                    .onChangeCompat(of: selectedLanguage) { newValue in
+                        updateLanguage(newValue)
+                    }
+
                     #if os(macOS)
                         FormToggle("Start At Login", "Launch the application when the system is logged in. If enabled at the same time as `Show in Menu Bar` and `Keep Menu Bar in Background`, the application interface will not be opened automatically.", $startAtLogin) { newValue in
                             updateLoginItems(newValue)
@@ -145,6 +159,7 @@ public struct AppView: View {
     }
 
     private func loadSettings() async {
+        selectedLanguage = Self.currentLanguage()
         #if os(macOS)
             startAtLogin = SMAppService.mainApp.status == .enabled
             menuBarExtraInBackground = await SharedPreferences.menuBarExtraInBackground.get()
@@ -155,6 +170,32 @@ public struct AppView: View {
         isLoading = false
     }
 
+    private static func currentLanguage() -> String? {
+        guard let languages = UserDefaults.standard.array(forKey: "AppleLanguages") as? [String],
+              let first = languages.first
+        else {
+            return nil
+        }
+        for language in supportedLanguages {
+            if let code = language.code, first.hasPrefix(code) {
+                return code
+            }
+        }
+        return nil
+    }
+
+    private func updateLanguage(_ language: String?) {
+        if let language {
+            UserDefaults.standard.set([language], forKey: "AppleLanguages")
+        } else {
+            UserDefaults.standard.removeObject(forKey: "AppleLanguages")
+        }
+        alert = AlertState(
+            title: String(localized: "Restart Required"),
+            message: String(localized: "Language will be changed after restarting the app.")
+        )
+    }
+
     #if os(macOS)
 
         private func updateLoginItems(_ startAtLogin: Bool) {

ApplicationLibrary/Views/Setting/SettingView.swift

@@ -27,11 +27,7 @@ public struct SettingView: View {
             self
         }
 
-        #if os(macOS)
-            case app
-        #endif
-
-        case core, packetTunnel, onDemandRules, profileOverride, sponsors
+        case app, core, packetTunnel, onDemandRules, profileOverride, sponsors
 
         #if os(macOS)
             var page: SettingsPage {
@@ -58,10 +54,8 @@ public struct SettingView: View {
 
         var title: String {
             switch self {
-            #if os(macOS)
             case .app:
                 return String(localized: "App")
-            #endif
             case .core:
                 return String(localized: "Core")
             case .packetTunnel:
@@ -77,10 +71,8 @@ public struct SettingView: View {
 
         private var iconImage: String {
             switch self {
-            #if os(macOS)
             case .app:
                 return "app.badge.fill"
-            #endif
             case .core:
                 return "shippingbox.fill"
             case .packetTunnel:
@@ -98,10 +90,8 @@ public struct SettingView: View {
         var contentView: some View {
             Group {
                 switch self {
-                #if os(macOS)
                 case .app:
                     AppView()
-                #endif
                 case .core:
                     CoreView()
                 case .packetTunnel:
@@ -165,10 +155,7 @@ public struct SettingView: View {
     public var body: some View {
         FormView {
             Section {
-                #if os(macOS)
-                    Tabs.app.navigationLink
-                #endif
-                ForEach([Tabs.core, Tabs.packetTunnel, Tabs.onDemandRules, Tabs.profileOverride]) { it in
+                ForEach([Tabs.app, Tabs.core, Tabs.packetTunnel, Tabs.onDemandRules, Tabs.profileOverride]) { it in
                     it.navigationLink
                 }
             }

Localizable.xcstrings

@@ -1531,6 +1531,26 @@
         }
       }
     },
+    "Language" : {
+      "localizations" : {
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "语言"
+          }
+        }
+      }
+    },
+    "Language will be changed after restarting the app." : {
+      "localizations" : {
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "重启应用后语言将生效。"
+          }
+        }
+      }
+    },
     "Last Updated" : {
       "localizations" : {
         "zh-Hans" : {
@@ -1830,9 +1850,6 @@
           }
         }
       }
-    },
-    "Not installed" : {
-
     },
     "Ok" : {
       "localizations" : {
@@ -2141,6 +2158,16 @@
         }
       }
     },
+    "Restart Required" : {
+      "localizations" : {
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "需要重启"
+          }
+        }
+      }
+    },
     "Resume" : {
       "comment" : "Resume log auto-scroll",
       "localizations" : {
@@ -2517,6 +2544,16 @@
         }
       }
     },
+    "System Default" : {
+      "localizations" : {
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "跟随系统"
+          }
+        }
+      }
+    },
     "System Extension" : {
       "localizations" : {
         "zh-Hans" : {