fix: synchronize macOS window theme on flutter theme changed.

flutter/lib/utils/platform_channel.dart

@@ -0,0 +1,34 @@
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_hbb/main.dart';
+
+enum SystemWindowTheme { light, dark }
+
+/// The platform channel for RustDesk
+class RdPlatformChannel {
+  RdPlatformChannel._();
+
+  static final RdPlatformChannel _windowUtil = RdPlatformChannel._();
+
+  static RdPlatformChannel get instance => _windowUtil;
+
+  final MethodChannel _osxMethodChannel =
+      MethodChannel("org.rustdesk.rustdesk/macos");
+  final MethodChannel _winMethodChannel =
+      MethodChannel("org.rustdesk.rustdesk/windows");
+  final MethodChannel _linuxMethodChannel =
+      MethodChannel("org.rustdesk.rustdesk/linux");
+
+  /// Change the theme of the system window
+  Future<void> changeSystemWindowTheme(SystemWindowTheme theme) {
+    assert(Platform.isMacOS);
+    if (kDebugMode) {
+      print(
+          "[Window ${kWindowId ?? 'Main'}] change system window theme to ${theme.name}");
+    }
+    return _osxMethodChannel
+        .invokeMethod("setWindowTheme", {"themeName": theme.name});
+  }
+}