Add title bar color sync with app theme on Windows

lib/widgets/fluffy_chat_app.dart

@@ -51,6 +51,12 @@ class FluffyChatApp extends StatefulWidget {
 
 class _FluffyChatAppState extends State<FluffyChatApp> {
   final _androidSystemFontPlugin = AndroidSystemFont();
+  static const _platform = MethodChannel('xyz.extera.next/window');
+
+  // Keeps track of the last Brightness applied to the native window frame
+  // (title bar) so we don't spam the platform channel with redundant calls
+  // on every rebuild.
+  Brightness? _lastWindowBrightness;
 
   @override
   void initState() {
@@ -88,6 +94,25 @@ class _FluffyChatAppState extends State<FluffyChatApp> {
     });
   }
 
+  void _syncWindowBrightness(BuildContext context, ThemeMode themeMode) {
+    if (!Platform.isWindows) return;
+
+    final resolvedBrightness = switch (themeMode) {
+      ThemeMode.dark => Brightness.dark,
+      ThemeMode.light => Brightness.light,
+      ThemeMode.system => MediaQuery.platformBrightnessOf(context),
+    };
+
+    if (resolvedBrightness == _lastWindowBrightness) return;
+    _lastWindowBrightness = resolvedBrightness;
+
+    _platform.invokeMethod('setTitleBarDarkMode', {
+      'isDark': resolvedBrightness == Brightness.dark,
+    }).catchError((e) {
+      debugPrint('Failed to set title bar color: $e');
+    });
+  }
+
   @override
   Widget build(BuildContext context) {
     return ThemeBuilder(
@@ -99,45 +124,51 @@ class _FluffyChatAppState extends State<FluffyChatApp> {
             schemeVariant,
             pureBlack,
             twemoji,
-          ) => MaterialApp.router(
-            title: AppConfig.applicationName,
-            themeMode: themeMode,
-            theme: FluffyThemes.buildTheme(
-              context,
-              Brightness.light,
-              primaryColor,
-              schemeVariant,
-              pureBlack,
-              twemoji,
-            ),
-            darkTheme: FluffyThemes.buildTheme(
-              context,
-              Brightness.dark,
-              primaryColor,
-              schemeVariant,
-              pureBlack,
-              twemoji,
-            ),
-            scrollBehavior: CustomScrollBehavior(),
-            localizationsDelegates: L10n.localizationsDelegates,
-            supportedLocales: L10n.supportedLocales,
-            routerConfig: FluffyChatApp.router,
-            builder: (context, child) => AppLockWidget(
-              pincode: widget.pincode,
-              clients: widget.clients,
+          ) {
+            WidgetsBinding.instance.addPostFrameCallback((_) {
+              _syncWindowBrightness(context, themeMode);
+            });
+
+            return MaterialApp.router(
+              title: AppConfig.applicationName,
+              themeMode: themeMode,
+              theme: FluffyThemes.buildTheme(
+                context,
+                Brightness.light,
+                primaryColor,
+                schemeVariant,
+                pureBlack,
+                twemoji,
+              ),
+              darkTheme: FluffyThemes.buildTheme(
+                context,
+                Brightness.dark,
+                primaryColor,
+                schemeVariant,
+                pureBlack,
+                twemoji,
+              ),
+              scrollBehavior: CustomScrollBehavior(),
+              localizationsDelegates: L10n.localizationsDelegates,
+              supportedLocales: L10n.supportedLocales,
+              routerConfig: FluffyChatApp.router,
+              builder: (context, child) => AppLockWidget(
+                pincode: widget.pincode,
+                clients: widget.clients,	
               // Need a navigator above the Matrix widget for
               // displaying dialogs
-              child: DownloadManager(
-                child: BackgroundAudioPlayer(
-                  child: Matrix(
-                    clients: widget.clients,
-                    store: widget.store,
-                    child: widget.testWidget ?? child,
+                child: DownloadManager(
+                  child: BackgroundAudioPlayer(
+                    child: Matrix(
+                      clients: widget.clients,
+                      store: widget.store,
+                      child: widget.testWidget ?? child,
+                    ),
                   ),
                 ),
               ),
-            ),
-          ),
+            );
+          },
     );
   }
-}
+}

windows/runner/flutter_window.cpp

@@ -26,9 +26,42 @@ bool FlutterWindow::OnCreate() {
   }
   RegisterPlugins(flutter_controller_->engine());
   SetChildContent(flutter_controller_->view()->GetNativeWindow());
+
+  SetupChannelHandlers();
   return true;
 }
 
+void FlutterWindow::SetupChannelHandlers() {
+  auto channel =
+      std::make_unique<flutter::MethodChannel<flutter::EncodableValue>>(
+          flutter_controller_->engine()->messenger(), "xyz.extera.next/window",
+          &flutter::StandardMethodCodec::GetInstance());
+
+  channel->SetMethodCallHandler(
+      [this](const flutter::MethodCall<flutter::EncodableValue>& call,
+             std::unique_ptr<flutter::MethodResult<flutter::EncodableValue>>
+                 result) {
+        if (call.method_name() == "setTitleBarDarkMode") {
+          const auto* arguments = std::get_if<flutter::EncodableMap>(call.arguments());
+          if (arguments) {
+            auto isDark_variant = arguments->find(flutter::EncodableValue("isDark"));
+            if (isDark_variant != arguments->end()) {
+              if (const auto* isDark = std::get_if<bool>(&isDark_variant->second)) {
+                SetTitleBarColor(*isDark);
+                result->Success();
+                return;
+              }
+            }
+          }
+          result->Error("INVALID_ARGUMENT", "isDark parameter is required");
+        } else {
+          result->NotImplemented();
+        }
+      });
+
+  method_channel_ = std::move(channel);
+}
+
 void FlutterWindow::OnDestroy() {
   if (flutter_controller_) {
     flutter_controller_ = nullptr;

windows/runner/flutter_window.h

@@ -3,6 +3,8 @@
 
 #include <flutter/dart_project.h>
 #include <flutter/flutter_view_controller.h>
+#include <flutter/method_channel.h>
+#include <flutter/standard_method_codec.h>
 
 #include <memory>
 
@@ -28,6 +30,10 @@ class FlutterWindow : public Win32Window {
 
   // The Flutter instance hosted by this window.
   std::unique_ptr<flutter::FlutterViewController> flutter_controller_;
+  std::unique_ptr<flutter::MethodChannel<flutter::EncodableValue>>
+      method_channel_;
+
+  void SetupChannelHandlers();
 };
 
 #endif  // RUNNER_FLUTTER_WINDOW_H_

windows/runner/win32_window.cpp

@@ -1,9 +1,12 @@
 #include "win32_window.h"
 
 #include <flutter_windows.h>
+#include <dwmapi.h>
 
 #include "resource.h"
 
+#pragma comment(lib, "dwmapi.lib")
+
 namespace {
 
 constexpr const wchar_t kWindowClassName[] = L"FLUTTER_RUNNER_WIN32_WINDOW";
@@ -235,6 +238,15 @@ void Win32Window::SetQuitOnClose(bool quit_on_close) {
   quit_on_close_ = quit_on_close;
 }
 
+void Win32Window::SetTitleBarColor(bool isDark) {
+  if (!window_handle_) return;
+
+  // Use DwmSetWindowAttribute to set the title bar color
+  // DWMWA_USE_IMMERSIVE_DARK_MODE = 20 for Windows 11
+  BOOL value = isDark ? TRUE : FALSE;
+  DwmSetWindowAttribute(window_handle_, 20, &value, sizeof(value));
+}
+
 bool Win32Window::OnCreate() {
   // No-op; provided for subclasses.
   return true;

windows/runner/win32_window.h

@@ -54,6 +54,10 @@ class Win32Window {
   // Return a RECT representing the bounds of the current client area.
   RECT GetClientArea();
 
+  // Sets the title bar color based on brightness (dark/light mode).
+  // isDark: true for dark mode (dark title bar), false for light mode (light title bar)
+  void SetTitleBarColor(bool isDark);
+
  protected:
   // Processes and route salient window messages for mouse handling,
   // size change and DPI. Delegates handling of these to member overloads that