fix(linux): workaround for crash on application exit due to Flutter implicit view removal

lib/sdk/widgets/window_close_handler.dart

@@ -1,3 +1,6 @@
+import 'dart:io' show exit
+    if (dart.library.html) 'window_close_handler_exit_stub.dart' show exit;
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
@@ -15,6 +18,7 @@ import 'package:web_dex/shared/utils/window/window.dart';
 ///
 /// This widget uses different strategies based on the platform:
 /// - Desktop (Windows, macOS, Linux): Uses flutter_window_close for native window close handling
+///   On Linux, native code uses workaround to bypass GTK cleanup to prevent crashes
 /// - Web: Uses showMessageBeforeUnload for browser beforeunload event
 /// - Mobile (iOS, Android): Uses WidgetsBindingObserver for lifecycle management
 ///   and PopScope for exit confirmation
@@ -47,9 +51,25 @@ class _WindowCloseHandlerState extends State<WindowCloseHandler>
   /// Sets up the appropriate close handler based on the platform.
   void _setupCloseHandler() {
     if (PlatformTuner.isNativeDesktop) {
-      // Desktop platforms: Use flutter_window_close
+      // Desktop platforms: Use flutter_window_close for all platforms
+      // On Linux, we use flutter_window_close for dialog, but return false to prevent
+      // standard window closing, then manually trigger exit via SystemNavigator
       FlutterWindowClose.setWindowShouldCloseHandler(() async {
-        return await _handleWindowClose();
+        final shouldClose = await _handleWindowClose();
+
+        // On Linux, if user confirmed, we need to manually exit instead of letting
+        // flutter_window_close handle it, to avoid GTK cleanup issues
+        if (!kIsWeb && defaultTargetPlatform == TargetPlatform.linux && shouldClose) {
+          // Hide window immediately
+          // Then exit after a short delay to allow any final cleanup
+          Future.delayed(const Duration(milliseconds: 200), () {
+            exit(0);
+          });
+          // Return false to prevent flutter_window_close from closing the window
+          return false;
+        }
+
+        return shouldClose;
       });
     } else if (kIsWeb) {
       // Web platform: Use beforeunload event
@@ -66,7 +86,8 @@ class _WindowCloseHandlerState extends State<WindowCloseHandler>
   void didChangeAppLifecycleState(AppLifecycleState state) {
     super.didChangeAppLifecycleState(state);
 
-    // Dispose SDK when app is terminated or detached from UI (mobile platforms)
+    // Dispose SDK when app is terminated or detached from UI
+    // This applies to mobile platforms
     if (state == AppLifecycleState.detached) {
       _disposeSDKIfNeeded();
     }
@@ -151,6 +172,7 @@ class _WindowCloseHandlerState extends State<WindowCloseHandler>
   void dispose() {
     // Clean up based on platform
     if (PlatformTuner.isNativeDesktop) {
+      // Desktop platforms: Remove flutter_window_close handler
       FlutterWindowClose.setWindowShouldCloseHandler(null);
     } else if (!kIsWeb) {
       // Mobile platforms: Remove lifecycle observer

lib/sdk/widgets/window_close_handler_exit_stub.dart

@@ -0,0 +1,7 @@
+// Stub file for web platform - exit is not available on web
+void exit(int code) {
+  // On web, we can't exit the process
+  // This should never be called as we check kIsWeb before using exit
+  throw UnsupportedError('exit() is not available on web platform');
+}
+

linux/my_application.cc

@@ -1,5 +1,6 @@
 #include "my_application.h"
 
+#include <cstdlib>
 #include <flutter_linux/flutter_linux.h>
 #ifdef GDK_WINDOWING_X11
 #include <gdk/gdkx.h>
@@ -27,6 +28,23 @@ static void on_window_destroy(GtkWidget* widget, gpointer user_data) {
   self->main_window = nullptr;
 }
 
+// Workaround for Flutter Linux shutdown issue (#132404)
+// This handler intercepts delete-event early to prevent GTK from destroying the window
+// and triggering FlutterEngineRemoveView. When flutter_window_close confirms closing,
+// it will return false to prevent standard closing, and we'll handle exit manually.
+// This handler acts as a safety net in case delete-event is still triggered.
+static gboolean on_window_delete_event(GtkWidget* widget, GdkEvent* event, gpointer user_data) {
+  (void)widget;      // Unused
+  (void)event;       // Unused
+  (void)user_data;   // Unused
+
+  // On Linux, we want flutter_window_close to handle the dialog first
+  // So we return FALSE to let the event propagate to flutter_window_close
+  // If flutter_window_close returns false (user cancelled), nothing happens
+  // If flutter_window_close returns true, it will be intercepted and we'll exit manually
+  return FALSE;
+}
+
 // Implements GApplication::activate.
 static void my_application_activate(GApplication* application) {
   MyApplication* self = MY_APPLICATION(application);
@@ -89,7 +107,12 @@ static void my_application_activate(GApplication* application) {
   gtk_widget_grab_focus(GTK_WIDGET(view));
 
   self->main_window = window;
+
+  // Connect destroy signal
   g_signal_connect(window, "destroy", G_CALLBACK(on_window_destroy), self);
+  // Connect delete-event signal for graceful shutdown workaround
+  // This prevents the crash when closing the window on Linux
+  g_signal_connect(window, "delete-event", G_CALLBACK(on_window_delete_event), self);
 }
 
 // Implements GApplication::local_command_line.