feat(platform): treat HarmonyOS as a mobile target

.gitignore

@@ -109,3 +109,7 @@ android/app/src/main/jniLibs/
 /third_party/fvp/android/.cxx/
 /third_party/fvp/android/mdk-sdk/
 /third_party/fvp/android/mdk-sdk-*.7z
+
+# OHOS plugin overlay working copies (scripts/enable-ohos-plugins.sh)
+/pubspec.yaml.ohos-backup
+/pubspec.lock.ohos-backup

lib/app/desktop_image_preview_window.dart

@@ -14,6 +14,7 @@ import '../components/ui_components.dart';
 import '../l10n/app_localizations.dart';
 import '../platform/desktop_clipboard_images.dart';
 import '../platform/keyboard_modifiers.dart';
+import '../platform/ohos_support.dart';
 import '../tdlib/td_image_loader.dart';
 import '../tdlib/td_models.dart';
 import '../theme/app_theme.dart';
@@ -304,7 +305,7 @@ class _DesktopImagePreviewState extends State<_DesktopImagePreview> {
         bytes: bytes,
       );
       if (selected == null) return;
-      if (!Platform.isAndroid && !Platform.isIOS) {
+      if (!isMobilePlatform) {
         await File(selected).writeAsBytes(bytes, flush: true);
       }
       _showStatus(AppStrings.t(AppStringKeys.accentColorPickerSave));

lib/auth/account_backup_service.dart

@@ -4,6 +4,7 @@ import 'dart:io';
 import 'package:flutter/services.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
+import '../platform/ohos_support.dart';
 import '../tdlib/gram_js_session.dart';
 import '../tdlib/json_helpers.dart';
 import '../tdlib/td_client.dart';
@@ -38,8 +39,7 @@ class AccountSessionBackup {
 class AccountBackupService {
   AccountBackupService({MethodChannel? channel, bool? platformEligible})
     : _channel = channel ?? const MethodChannel('mithka/account_backup'),
-      _platformEligible =
-          platformEligible ?? (Platform.isIOS || Platform.isAndroid);
+      _platformEligible = platformEligible ?? isMobilePlatform;
 
   static final AccountBackupService shared = AccountBackupService();
 
@@ -66,15 +66,26 @@ class AccountBackupService {
     required bool isSupported,
   }) => isIOS && isSupported;
 
-  Future<bool> get isSupported async {
-    if (!_platformEligible) return false;
-    return await _channel.invokeMethod<bool>('isSupported') ?? false;
-  }
+  Future<bool> get isSupported => _probeSupport('isSupported');
+
+  Future<bool> get isLocalStorageSupported =>
+      _probeSupport('isLocalStorageSupported');
 
-  Future<bool> get isLocalStorageSupported async {
+  /// A mobile OS says nothing about whether this host implements the
+  /// `mithka/account_backup` channel — the HarmonyOS host registers only
+  /// generated federated plugins and has no handler for it, so the raw probe
+  /// throws [MissingPluginException] at call time. Report the capability as
+  /// absent instead: every surface already owns a not-supported branch
+  /// (empty backup list, disabled buttons, login consent row hidden).
+  Future<bool> _probeSupport(String method) async {
     if (!_platformEligible) return false;
-    return await _channel.invokeMethod<bool>('isLocalStorageSupported') ??
-        false;
+    try {
+      return await _channel.invokeMethod<bool>(method) ?? false;
+    } on MissingPluginException {
+      return false;
+    } on PlatformException {
+      return false;
+    }
   }
 
   Future<Set<String>> consentedAccountIds() async {

lib/auth/login_view.dart

@@ -26,6 +26,7 @@ import '../components/app_icons.dart';
 import '../components/app_interactive_surface.dart';
 import '../components/country_flag.dart';
 import '../components/ui_components.dart';
+import '../platform/ohos_support.dart';
 import '../profile/profile_proxy_button.dart';
 import '../settings/account_backup_view.dart';
 import '../settings/api_credentials_view.dart';
@@ -106,11 +107,18 @@ class _LoginViewState extends State<LoginView> {
   String get _phoneDigits => _phone.text.replaceAll(RegExp(r'[^0-9]'), '');
   Country? get _detectedCountry => Country.match(_phoneDigits);
 
+  /// Whether the restore entry may appear: a mobile form factor AND a native
+  /// account-backup implementation behind it. The icon is only advertised
+  /// once the channel answered, so a mobile host without the channel
+  /// (HarmonyOS today) hides it instead of opening an empty restore sheet.
+  bool get _canRestoreAccountBackup =>
+      isMobilePlatform && (_backupSupported || _restorableBackupCount > 0);
+
   @override
   void initState() {
     super.initState();
     unawaited(_loadBotEndpoint());
-    if (Platform.isIOS || Platform.isAndroid) {
+    if (isMobilePlatform) {
       unawaited(_initializeBackupConsent());
       unawaited(_loadRestorableBackupCount());
     }
@@ -1149,7 +1157,7 @@ class _LoginViewState extends State<LoginView> {
             enabled: !auth.isWorking,
             onTap: () => _requestQrLogin(auth),
           ),
-        if (showingPhone && (Platform.isIOS || Platform.isAndroid))
+        if (showingPhone && _canRestoreAccountBackup)
           _loginIconButton(
             icon: HeroAppIcons.key,
             tooltip: AppStrings.t(AppStringKeys.accountBackupRestoreAccount),

lib/call/call_screen.dart

@@ -131,8 +131,7 @@ class _CallScreenState extends State<CallScreen> {
                     children: [
                       _overlayScrim(isVideoActive),
                       if (showLocalPreview) _localPreview(isLandscape),
-                      if (showLocalPreview &&
-                          (Platform.isAndroid || Platform.isIOS))
+                      if (showLocalPreview && widget.manager.supportsMediaCalls)
                         Positioned(
                           top: isLandscape ? 16 : 54,
                           left: isLandscape ? 24 : 16,
@@ -238,7 +237,7 @@ class _CallScreenState extends State<CallScreen> {
           ),
         // Remote camera feed — fills the screen over the
         // blurred-avatar fallback once decoded frames arrive (black until then).
-        if (isVideoActive && (Platform.isAndroid || Platform.isIOS))
+        if (isVideoActive && widget.manager.supportsMediaCalls)
           _nativeVideoView('remote'),
       ],
     );
@@ -261,8 +260,12 @@ class _CallScreenState extends State<CallScreen> {
 
   Widget _localPreview(bool isLandscape) {
     // Show our own camera feed when it's on; otherwise a placeholder glyph.
+    // The engine capability (a native tgcalls implementation owns the
+    // `mithka/video_view` platform views) decides, not the form factor: a
+    // mobile host without the engine keeps the placeholder instead of
+    // mounting a view type nothing renders into.
     final showVideo =
-        (Platform.isAndroid || Platform.isIOS) && widget.manager.isVideoEnabled;
+        widget.manager.supportsMediaCalls && widget.manager.isVideoEnabled;
     return Positioned(
       top: 56,
       right: isLandscape ? 24 : 16,

lib/chat/chat_wallpaper.dart

@@ -16,6 +16,7 @@ import 'package:shared_preferences/shared_preferences.dart';
 import 'package:vector_graphics/vector_graphics_compat.dart'
     show RenderingStrategy;
 
+import '../platform/ohos_support.dart';
 import '../tdlib/json_helpers.dart';
 import '../tdlib/td_client.dart';
 import '../tdlib/td_image_loader.dart';
@@ -2641,10 +2642,7 @@ class _WallpaperMotionState extends State<_WallpaperMotion>
   }
 }
 
-bool get _supportsWallpaperTilt =>
-    !kIsWeb &&
-    (defaultTargetPlatform == TargetPlatform.android ||
-        defaultTargetPlatform == TargetPlatform.iOS);
+bool get _supportsWallpaperTilt => isMobilePlatform;
 
 /// Maps the gravity-vector change since a wallpaper was opened to a bounded
 /// parallax translation. The baseline keeps an upright phone centered just as

lib/chat/link_browser.dart

@@ -48,9 +48,9 @@ bool internalBrowserSupported({TargetPlatform? platform, bool isWeb = kIsWeb}) {
     TargetPlatform.android ||
     TargetPlatform.iOS ||
     TargetPlatform.macOS => true,
-    TargetPlatform.fuchsia ||
-    TargetPlatform.linux ||
-    TargetPlatform.windows => false,
+    // Desktop, fuchsia, and the ohos fork's extra enum value fall back to the
+    // system browser instead of throwing.
+    _ => false,
   };
 }
 

lib/chat/media_library_saver.dart

@@ -1,8 +1,10 @@
 import 'dart:io';
 
+import 'package:flutter/services.dart';
 import 'package:permission_handler/permission_handler.dart';
 import 'package:photo_manager/photo_manager.dart';
 
+import '../platform/ohos_support.dart';
 import '../tdlib/td_image_loader.dart';
 import '../tdlib/td_models.dart';
 
@@ -50,9 +52,17 @@ class MediaLibrarySaveTarget {
 class MediaLibrarySaver {
   const MediaLibrarySaver._();
 
+  /// Saves a chat photo/video into the system gallery.
+  ///
+  /// Being a mobile OS does not guarantee a photo_library implementation: a
+  /// host without one (HarmonyOS today) has no handler on the photo_manager
+  /// channel, and [PhotoManager.systemVersion] short-circuits there without
+  /// crossing the channel, so the first real round trip is the save itself.
+  /// A missing channel reads as [MediaLibrarySaveResult.unsupported] — the
+  /// same answer a desktop host gets — instead of a call-time crash.
   static Future<MediaLibrarySaveResult> save(ChatMessage message) async {
     final target = MediaLibrarySaveTarget.fromMessage(message);
-    if (target == null || (!Platform.isIOS && !Platform.isAndroid)) {
+    if (target == null || !isMobilePlatform) {
       return MediaLibrarySaveResult.unsupported;
     }
 
@@ -72,6 +82,8 @@ class MediaLibrarySaver {
         creationDate: target.creationDate,
         permissionAlreadyGranted: true,
       );
+    } on MissingPluginException {
+      return MediaLibrarySaveResult.unsupported;
     } catch (_) {
       return MediaLibrarySaveResult.failed;
     }
@@ -85,7 +97,7 @@ class MediaLibrarySaver {
     required bool isVideo,
     DateTime? creationDate,
   }) async {
-    if (!Platform.isIOS && !Platform.isAndroid) {
+    if (!isMobilePlatform) {
       return MediaLibrarySaveResult.unsupported;
     }
     try {
@@ -94,6 +106,8 @@ class MediaLibrarySaver {
         isVideo: isVideo,
         creationDate: creationDate,
       );
+    } on MissingPluginException {
+      return MediaLibrarySaveResult.unsupported;
     } catch (_) {
       return MediaLibrarySaveResult.failed;
     }

lib/chat/music_now_playing.dart

@@ -13,6 +13,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 
 import '../l10n/app_localizations.dart';
+import '../platform/ohos_support.dart';
 import '../tdlib/td_image_loader.dart';
 import '../tdlib/td_models.dart';
 
@@ -114,10 +115,7 @@ class MusicNowPlayingBridge {
   /// generation must never publish onto a reused file id.
   int _artworkGeneration = 0;
 
-  static bool get _platformSupported =>
-      !kIsWeb &&
-      (defaultTargetPlatform == TargetPlatform.iOS ||
-          defaultTargetPlatform == TargetPlatform.android);
+  static bool get _platformSupported => isMobilePlatform;
 
   static Future<String?> _defaultArtwork(TdFileRef cover) =>
       TdFileCenter.shared.pathFor(cover);

lib/chat/sticker_export_service.dart

@@ -12,6 +12,7 @@ import 'package:lottie/lottie.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:video_player/video_player.dart';
 
+import '../platform/ohos_support.dart';
 import '../tdlib/td_image_loader.dart';
 import '../tdlib/td_models.dart';
 import 'media_library_saver.dart';
@@ -126,7 +127,7 @@ class StickerExportService {
         allowedExtensions: [format.extension],
         bytes: bytes,
       );
-      if (selectedPath != null && !Platform.isIOS && !Platform.isAndroid) {
+      if (selectedPath != null && !isMobilePlatform) {
         await File(selectedPath).writeAsBytes(bytes, flush: true);
       }
       return selectedPath == null
@@ -201,7 +202,7 @@ class StickerExportService {
         allowedExtensions: const ['zip'],
         bytes: Uint8List.fromList(bytes),
       );
-      if (selectedPath != null && !Platform.isIOS && !Platform.isAndroid) {
+      if (selectedPath != null && !isMobilePlatform) {
         await File(selectedPath).writeAsBytes(bytes, flush: true);
       }
       return selectedPath == null
@@ -262,7 +263,7 @@ class StickerExportService {
 
   static bool _isSupportedPlatform(StickerExportDestination destination) {
     if (destination == StickerExportDestination.photos) {
-      return Platform.isIOS || Platform.isAndroid;
+      return isMobilePlatform;
     }
     return Platform.isIOS ||
         Platform.isAndroid ||

lib/chat/video_player_view.dart

@@ -36,6 +36,7 @@ import '../media/video_playback_reporting.dart';
 import '../media/video_view_compatibility.dart';
 import '../platform/fullscreen_system_ui.dart';
 import '../platform/keyboard_modifiers.dart';
+import '../platform/ohos_support.dart';
 import '../platform/player_brightness.dart';
 import '../platform/player_system_volume.dart';
 import '../platform/screen_wakelock.dart';
@@ -4987,9 +4988,7 @@ class _VideoPlayerViewState extends State<VideoPlayerView>
 
   bool get _showsOrientationButton =>
       widget.presentation == VideoPlayerPresentation.fullscreen &&
-      !kIsWeb &&
-      (defaultTargetPlatform == TargetPlatform.android ||
-          defaultTargetPlatform == TargetPlatform.iOS);
+      isMobilePlatform;
 
   Future<void> _toggleVideoOrientation() async {
     if (_orientationChangeInFlight) return;

lib/main.dart

@@ -70,6 +70,7 @@ import 'notifications/notification_preferences.dart';
 import 'notifications/push_device_registrar.dart';
 import 'platform/application_exit_coordinator.dart';
 import 'platform/firebase_configuration.dart';
+import 'platform/ohos_support.dart';
 import 'platform/system_ui.dart';
 import 'pro/mithka_pro_service.dart';
 import 'security/local_app_lock_controller.dart';
@@ -220,9 +221,7 @@ Future<void> _bootstrapAndRunApp() async {
   // AuthManager's stream whenever it is ready.
   final auth = AuthManager()..start();
   _initializeVideoBackend();
-  final isMobile =
-      defaultTargetPlatform == TargetPlatform.iOS ||
-      defaultTargetPlatform == TargetPlatform.android;
+  final isMobile = isMobilePlatform;
   if (isMobile) {
     // Let iPhone and iPad follow every physical orientation. Desktop windows
     // have no orientation/system bars — skip both platform-channel round

lib/platform/ohos_support.dart

@@ -0,0 +1,49 @@
+//
+//  ohos_support.dart
+//
+//  HarmonyOS (ohos) platform gating helpers.
+//
+
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+
+/// Whether [operatingSystem] names HarmonyOS.
+///
+/// Pure so tests can pin the mapping on any host.
+bool isOhosFor(String operatingSystem) => operatingSystem == 'ohos';
+
+/// Whether the app runs on HarmonyOS (HarmonyOS NEXT).
+///
+/// Detected through `dart:io`'s operating-system string instead of
+/// `TargetPlatform.ohos` because the stock Flutter SDK that CI compiles with
+/// has no such enum value — that literal only builds against the OpenHarmony
+/// flutter fork. The fork reports `Platform.operatingSystem == 'ohos'` at
+/// runtime, which stock-compiled code can still observe.
+bool get isOhos => !kIsWeb && isOhosFor(Platform.operatingSystem);
+
+/// Whether [operatingSystem] names a phone/tablet system.
+bool isMobileOperatingSystemFor(String operatingSystem) =>
+    operatingSystem == 'android' ||
+    operatingSystem == 'ios' ||
+    isOhosFor(operatingSystem);
+
+/// Whether the app runs on a phone/tablet platform: Android, iOS, or
+/// HarmonyOS.
+///
+/// The mobile-vs-desktop boundary in one place, so HarmonyOS joins the mobile
+/// branch without every call site learning about it. Reads `dart:io` (not
+/// `TargetPlatform.ohos`) for the same stock-SDK reason as [isOhos]; on the
+/// ohos fork `defaultTargetPlatform` is an enum value stock code cannot name.
+///
+/// An explicit `debugDefaultTargetPlatformOverride` of Android or iOS also
+/// counts: widget tests simulate those platforms through that override while
+/// `dart:io` keeps reporting the desktop host, and the mobile branch must
+/// follow the simulation. The override is null outside tests, so real devices
+/// and profiles are decided by the operating system alone.
+bool get isMobilePlatform {
+  if (kIsWeb) return false;
+  if (isMobileOperatingSystemFor(Platform.operatingSystem)) return true;
+  final override = debugDefaultTargetPlatformOverride;
+  return override == TargetPlatform.android || override == TargetPlatform.iOS;
+}

lib/platform/system_ui.dart

@@ -9,6 +9,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
 import '../theme/app_theme.dart';
+import 'ohos_support.dart';
 
 /// The cold-start background, per brightness.
 ///
@@ -82,6 +83,10 @@ SystemUiOverlayStyle systemUiOverlayStyleForTheme(ThemeData theme) {
 
 /// Whether the current platform should treat system bars as edge-to-edge.
 bool get supportsImmersiveSystemUI {
+  // HarmonyOS reports a TargetPlatform the stock SDK's switch below cannot
+  // name, and it shares the Android windowing model (transparent, edge-to-edge
+  // system bars), so it is decided by operating system here.
+  if (isOhos) return true;
   switch (defaultTargetPlatform) {
     case TargetPlatform.android:
     case TargetPlatform.iOS: