[window_proc_delegate] fix crash on multi engine

.gitignore

@@ -17,5 +17,5 @@ migrate_working_dir/
 *.ipr
 *.iws
 .idea/
-
+.vscode
 

packages/window_proc_delegate/CHANGELOG.md

@@ -1,3 +1,6 @@
+## 0.0.3
+* Fix crash on multi engine
+
 ## 0.0.2
 * Removed engine-specific message restriction - messages are now delivered to all registered delegates
 * Fixed crash issue when unregistering delegates

packages/window_proc_delegate/example/lib/main.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 
 import 'package:window_proc_delegate/window_proc_delegate.dart';
+import 'package:desktop_multi_window/desktop_multi_window.dart';
 
 void main() {
   runApp(const MyApp());
@@ -84,6 +85,12 @@ class _MyAppState extends State<MyApp> {
     }
   }
 
+  void _createChildWindow() async {
+    await WindowController.create(
+      WindowConfiguration(hiddenAtLaunch: false, arguments: ''),
+    );
+  }
+
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
@@ -106,6 +113,11 @@ class _MyAppState extends State<MyApp> {
                     onPressed: _delegateId != null ? _unregisterDelegate : null,
                     child: const Text('Unregister Delegate'),
                   ),
+                  const SizedBox(width: 8),
+                  ElevatedButton(
+                    onPressed: _createChildWindow,
+                    child: const Text('Create Child Window'),
+                  ),
                 ],
               ),
               const SizedBox(height: 8),

packages/window_proc_delegate/example/pubspec.lock

@@ -49,6 +49,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.0.8"
+  desktop_multi_window:
+    dependency: "direct main"
+    description:
+      name: desktop_multi_window
+      sha256: "60ba38725b8887b60e44d15afdcf0c3813568b5da2ccaf1e7f6fd09a380a6e24"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.3.0"
   fake_async:
     dependency: transitive
     description:
@@ -269,7 +277,7 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "0.0.1"
+    version: "0.0.3"
 sdks:
   dart: ">=3.10.0 <4.0.0"
   flutter: ">=3.18.0-18.0.pre.54"

packages/window_proc_delegate/example/pubspec.yaml

@@ -18,68 +18,15 @@ dependencies:
     sdk: flutter
 
   window_proc_delegate:
-    # When depending on this package from a real application you should use:
-    #   window_proc_delegate: ^x.y.z
-    # See https://dart.dev/tools/pub/dependencies#version-constraints
-    # The example app is bundled with the plugin so we use a path dependency on
-    # the parent directory to use the current plugin's version.
     path: ../
-
-  # The following adds the Cupertino Icons font to your application.
-  # Use with the CupertinoIcons class for iOS style icons.
   cupertino_icons: ^1.0.8
+  desktop_multi_window: ^0.3.0
 
 dev_dependencies:
   integration_test:
     sdk: flutter
   flutter_test:
     sdk: flutter
-
-  # The "flutter_lints" package below contains a set of recommended lints to
-  # encourage good coding practices. The lint set provided by the package is
-  # activated in the `analysis_options.yaml` file located at the root of your
-  # package. See that file for information about deactivating specific lint
-  # rules and activating additional ones.
   flutter_lints: ^6.0.0
 
-# For information on the generic Dart part of this file, see the
-# following page: https://dart.dev/tools/pub/pubspec
-
-# The following section is specific to Flutter packages.
 flutter:
-
-  # The following line ensures that the Material Icons font is
-  # included with your application, so that you can use the icons in
-  # the material Icons class.
-  uses-material-design: true
-
-  # To add assets to your application, add an assets section, like this:
-  # assets:
-  #   - images/a_dot_burr.jpeg
-  #   - images/a_dot_ham.jpeg
-
-  # An image asset can refer to one or more resolution-specific "variants", see
-  # https://flutter.dev/to/resolution-aware-images
-
-  # For details regarding adding assets from package dependencies, see
-  # https://flutter.dev/to/asset-from-package
-
-  # To add custom fonts to your application, add a fonts section here,
-  # in this "flutter" section. Each entry in this list should have a
-  # "family" key with the font family name, and a "fonts" key with a
-  # list giving the asset and other descriptors for the font. For
-  # example:
-  # fonts:
-  #   - family: Schyler
-  #     fonts:
-  #       - asset: fonts/Schyler-Regular.ttf
-  #       - asset: fonts/Schyler-Italic.ttf
-  #         style: italic
-  #   - family: Trajan Pro
-  #     fonts:
-  #       - asset: fonts/TrajanPro.ttf
-  #       - asset: fonts/TrajanPro_Bold.ttf
-  #         weight: 700
-  #
-  # For details regarding fonts from package dependencies,
-  # see https://flutter.dev/to/font-from-package

packages/window_proc_delegate/example/windows/flutter/generated_plugin_registrant.cc

@@ -6,9 +6,12 @@
 
 #include "generated_plugin_registrant.h"
 
+#include <desktop_multi_window/desktop_multi_window_plugin.h>
 #include <window_proc_delegate/window_proc_delegate_plugin_c_api.h>
 
 void RegisterPlugins(flutter::PluginRegistry* registry) {
+  DesktopMultiWindowPluginRegisterWithRegistrar(
+      registry->GetRegistrarForPlugin("DesktopMultiWindowPlugin"));
   WindowProcDelegatePluginCApiRegisterWithRegistrar(
       registry->GetRegistrarForPlugin("WindowProcDelegatePluginCApi"));
 }

packages/window_proc_delegate/example/windows/flutter/generated_plugins.cmake

@@ -3,6 +3,7 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  desktop_multi_window
   window_proc_delegate
 )
 

packages/window_proc_delegate/example/windows/runner/flutter_window.cpp

@@ -2,6 +2,7 @@
 
 #include <optional>
 
+#include "desktop_multi_window/desktop_multi_window_plugin.h"
 #include "flutter/generated_plugin_registrant.h"
 
 FlutterWindow::FlutterWindow(const flutter::DartProject& project)
@@ -25,11 +26,15 @@ bool FlutterWindow::OnCreate() {
     return false;
   }
   RegisterPlugins(flutter_controller_->engine());
+  DesktopMultiWindowSetWindowCreatedCallback([](void* controller) {
+    auto* flutter_view_controller =
+        reinterpret_cast<flutter::FlutterViewController*>(controller);
+    auto* registry = flutter_view_controller->engine();
+    RegisterPlugins(registry);
+  });
   SetChildContent(flutter_controller_->view()->GetNativeWindow());
 
-  flutter_controller_->engine()->SetNextFrameCallback([&]() {
-    this->Show();
-  });
+  flutter_controller_->engine()->SetNextFrameCallback([&]() { this->Show(); });
 
   // Flutter can complete the first frame before the "show window" callback is
   // registered. The following call ensures a frame is pending to ensure the

packages/window_proc_delegate/lib/src/window_proc_delegate_internal.dart

@@ -1,5 +1,6 @@
 import 'dart:ffi' as ffi;
 import 'dart:io';
+import 'package:flutter/services.dart';
 import 'package:flutter/foundation.dart';
 import 'windows_message.dart';
 import '../window_proc_delegate.dart';
@@ -33,6 +34,8 @@ external void setCallback(
 
 bool _initialized = false;
 bool _dartApiInitialized = false;
+bool _engineIdInitialized = false;
+final MethodChannel _channel = MethodChannel('window_proc_delegate');
 
 void ensureNativeLibraryInitialized() {
   if (_dartApiInitialized) return;
@@ -51,6 +54,29 @@ void ensureNativeLibraryInitialized() {
   }
 }
 
+/// Ensures the plugin's engine ID is initialized.
+///
+/// This method registers the current engine ID with the native plugin.
+/// It can be called early in application startup to ensure the plugin
+/// is ready before any delegates are registered.
+///
+/// If not called explicitly, the engine ID will be set automatically
+/// when the first delegate is registered.
+Future<void> ensureInitializeEngineId() async {
+  if (!Platform.isWindows) return;
+
+  if (_engineIdInitialized) return;
+
+  final int engineId = PlatformDispatcher.instance.engineId!;
+  try {
+    await _channel.invokeMethod('setEngineId', engineId);
+    _engineIdInitialized = true;
+  } catch (e) {
+    debugPrint('Failed to set engine ID: $e');
+    rethrow;
+  }
+}
+
 void initialize(
   List<WindowProcDelegateCallback?> delegates,
   void Function(ffi.Pointer<WindowsMessage>) handleWindowProc,
@@ -69,8 +95,11 @@ void initialize(
 
   // Get the engine ID and register the native callback
   try {
-    final engineId = PlatformDispatcher.instance.engineId!;
+    final int engineId = PlatformDispatcher.instance.engineId!;
     setCallback(engineId, nativeCallable.nativeFunction);
+
+    // Set engine ID asynchronously (fire-and-forget with error handling)
+    ensureInitializeEngineId();
   } catch (e) {
     debugPrint('Failed to set callback: $e');
   }

packages/window_proc_delegate/lib/window_proc_delegate.dart

@@ -2,6 +2,8 @@ import 'dart:ffi' as ffi;
 import 'src/windows_message.dart';
 import 'src/window_proc_delegate_internal.dart' as internal;
 
+export 'src/window_proc_delegate_internal.dart' show ensureInitializeEngineId;
+
 /// Signature for a WindowProc delegate callback.
 ///
 /// The callback receives the window message parameters:

packages/window_proc_delegate/pubspec.yaml

@@ -1,6 +1,6 @@
 name: window_proc_delegate
 description: A Flutter plugin that allows you to hook into Windows WindowProc messages from Dart code.
-version: 0.0.2
+version: 0.0.3
 homepage: https://github.com/boyan01/packages
 
 environment:

packages/window_proc_delegate/windows/include/window_proc_delegate/window_proc_delegate_plugin_c_api.h

@@ -2,55 +2,22 @@
 #define FLUTTER_PLUGIN_WINDOW_PROC_DELEGATE_PLUGIN_C_API_H_
 
 #include <flutter_plugin_registrar.h>
-#include <stdint.h>
-#include <windows.h>
 
 #ifdef FLUTTER_PLUGIN_IMPL
 #define FLUTTER_PLUGIN_EXPORT __declspec(dllexport)
 #else
 #define FLUTTER_PLUGIN_EXPORT __declspec(dllimport)
 #endif
 
-// Forward declaration
-namespace window_proc_delegate {
-struct WindowsMessage;
-}
-
 #if defined(__cplusplus)
 extern "C" {
 #endif
 
-// Callback signature for Dart WindowProc delegate
-typedef void (*DartWindowProcCallbackC)(
-    window_proc_delegate::WindowsMessage* message);
-
 FLUTTER_PLUGIN_EXPORT void WindowProcDelegatePluginCApiRegisterWithRegistrar(
     FlutterDesktopPluginRegistrarRef registrar);
 
-FLUTTER_PLUGIN_EXPORT void WindowProcDelegateSetCallback(
-    int64_t engineId, DartWindowProcCallbackC callback);
-
-FLUTTER_PLUGIN_EXPORT intptr_t WindowProcDelegateInitDartApi(void* data);
-
 #if defined(__cplusplus)
 }  // extern "C"
 #endif
 
-// C++ only functions (not in extern "C")
-#if defined(__cplusplus)
-#include <functional>
-
-namespace window_proc_delegate {
-typedef std::function<void(WindowsMessage*)> DartWindowProcCallback;
-}
-
-// Get the callback for a specific engine ID
-window_proc_delegate::DartWindowProcCallback GetCallbackForEngine(
-    int64_t engineId);
-
-// Get all registered callbacks
-std::vector<window_proc_delegate::DartWindowProcCallback> GetAllCallbacks();
-
-#endif
-
 #endif  // FLUTTER_PLUGIN_WINDOW_PROC_DELEGATE_PLUGIN_C_API_H_