feat(#43): flash Windows taskbar on new message when window unfocused

lib/services/notification_service.dart

@@ -7,6 +7,7 @@ import 'package:flutter/foundation.dart';
 import '../helpers/reaction_helper.dart';
 import '../l10n/app_localizations.dart';
 import '../utils/platform_info.dart';
+import 'windows_taskbar_service.dart';
 
 class NotificationService {
   static final NotificationService _instance = NotificationService._internal();
@@ -166,6 +167,7 @@ class NotificationService {
     int? badgeCount,
   }) async {
     if (!await _ensureInitialized()) return;
+    await WindowsTaskbarService.flash();
 
     final androidDetails = AndroidNotificationDetails(
       'messages',
@@ -266,6 +268,7 @@ class NotificationService {
     int? badgeCount,
   }) async {
     if (!await _ensureInitialized()) return;
+    await WindowsTaskbarService.flash();
 
     final androidDetails = AndroidNotificationDetails(
       'channel_messages',

lib/services/windows_taskbar_service.dart

@@ -0,0 +1,29 @@
+import 'dart:io' show Platform;
+
+import 'package:flutter/foundation.dart' show debugPrint;
+import 'package:flutter/services.dart';
+
+/// Flashes the Windows taskbar button to draw attention — e.g. a new message
+/// arriving while the app window is not in the foreground.
+///
+/// The native side (`windows/runner/flutter_window.cpp`) only flashes when the
+/// window is not already the foreground window, so callers don't need to track
+/// focus themselves. No-op on every non-Windows platform.
+class WindowsTaskbarService {
+  WindowsTaskbarService._();
+
+  static const MethodChannel _channel = MethodChannel(
+    'meshcore_open/windows_taskbar',
+  );
+
+  /// Flash the taskbar button if the window isn't focused. Safe on any platform
+  /// (no-op off Windows) and harmless if the native handler isn't registered.
+  static Future<void> flash() async {
+    if (!Platform.isWindows) return;
+    try {
+      await _channel.invokeMethod<void>('flash');
+    } catch (e) {
+      debugPrint('WindowsTaskbarService.flash failed: $e');
+    }
+  }
+}

windows/runner/flutter_window.cpp

@@ -1,5 +1,9 @@
 #include "flutter_window.h"
 
+#include <windows.h>
+
+#include <flutter/standard_method_codec.h>
+
 #include <optional>
 
 #include "flutter/generated_plugin_registrant.h"
@@ -25,6 +29,35 @@ bool FlutterWindow::OnCreate() {
     return false;
   }
   RegisterPlugins(flutter_controller_->engine());
+
+  // Taskbar flash channel - Dart flashes the taskbar button on a new message
+  // when the window isn't focused (see lib/services/windows_taskbar_service.dart).
+  taskbar_channel_ =
+      std::make_unique<flutter::MethodChannel<flutter::EncodableValue>>(
+          flutter_controller_->engine()->messenger(),
+          "meshcore_open/windows_taskbar",
+          &flutter::StandardMethodCodec::GetInstance());
+  taskbar_channel_->SetMethodCallHandler(
+      [this](const flutter::MethodCall<flutter::EncodableValue>& call,
+             std::unique_ptr<flutter::MethodResult<flutter::EncodableValue>>
+                 result) {
+        if (call.method_name() == "flash") {
+          HWND hwnd = GetHandle();
+          if (hwnd != nullptr && GetForegroundWindow() != hwnd) {
+            FLASHWINFO info = {};
+            info.cbSize = static_cast<UINT>(sizeof(info));
+            info.hwnd = hwnd;
+            info.dwFlags = FLASHW_TRAY | FLASHW_TIMERNOFG;
+            info.uCount = 0;
+            info.dwTimeout = 0;
+            FlashWindowEx(&info);
+          }
+          result->Success();
+        } else {
+          result->NotImplemented();
+        }
+      });
+
   SetChildContent(flutter_controller_->view()->GetNativeWindow());
 
   flutter_controller_->engine()->SetNextFrameCallback([&]() {

windows/runner/flutter_window.h

@@ -3,6 +3,7 @@
 
 #include <flutter/dart_project.h>
 #include <flutter/flutter_view_controller.h>
+#include <flutter/method_channel.h>
 
 #include <memory>
 
@@ -28,6 +29,10 @@ class FlutterWindow : public Win32Window {
 
   // The Flutter instance hosted by this window.
   std::unique_ptr<flutter::FlutterViewController> flutter_controller_;
+
+  // Channel for native taskbar control (e.g. flash on new message).
+  std::unique_ptr<flutter::MethodChannel<flutter::EncodableValue>>
+      taskbar_channel_;
 };
 
 #endif  // RUNNER_FLUTTER_WINDOW_H_