Fix Windows menu item state and enabled properties ignored before addItem

On Windows, MenuItem.state and MenuItem.enabled properties set before
the item is added to a Menu via addItem() or insertItem() were silently
ignored. The root cause had two parts:

1. MenuItem::Impl had no enabled_ field - SetEnabled() only called
   EnableMenuItem() if parent_menu_ was set (null before addItem),
   and IsEnabled() fell back to returning true when parent_menu_ was null.

2. Menu::AddItem() and Menu::InsertItem() hardcoded MF_UNCHECKED for
   checkbox/radio types instead of reading the item's current state_,
   and never applied MF_GRAYED for disabled items.

Fixes applied:

- Added bool enabled_ field to MenuItem::Impl (default true)
- SetEnabled() always stores to enabled_ regardless of parent_menu_
- IsEnabled() reads from enabled_ field directly
- AddItem() reads item->GetState() for MF_CHECKED/MF_UNCHECKED
- AddItem() checks item->IsEnabled() for MF_GRAYED
- InsertItem() same fixes plus submenu support (was missing entirely)

Resolves libnativeapi/nativeapi-flutter#4
Resolves libnativeapi/nativeapi-flutter#5

Author: lijy91

CMakeLists.txt

@@ -17,6 +17,7 @@ add_subdirectory(examples/display_c_example)
 add_subdirectory(examples/id_allocator_example)
 add_subdirectory(examples/keyboard_example)
 add_subdirectory(examples/menu_example)
+add_subdirectory(examples/menu_state_example)
 add_subdirectory(examples/menu_c_example)
 add_subdirectory(examples/message_dialog_example)
 add_subdirectory(examples/message_dialog_c_example)

src/platform/windows/menu_windows.cpp

@@ -107,6 +107,7 @@ class MenuItem::Impl {
   KeyboardAccelerator accelerator_;
   bool has_accelerator_;
   MenuItemState state_;
+  bool enabled_;
   int radio_group_;
   std::shared_ptr<Menu> submenu_;
   int window_proc_handle_id_;
@@ -123,6 +124,7 @@ class MenuItem::Impl {
         accelerator_("", ModifierKey::None),
         has_accelerator_(false),
         state_(MenuItemState::Unchecked),
+        enabled_(true),
         radio_group_(-1),
         window_proc_handle_id_(-1),
         submenu_opened_listener_id_(0),
@@ -355,19 +357,14 @@ KeyboardAccelerator MenuItem::GetAccelerator() const {
 }
 
 void MenuItem::SetEnabled(bool enabled) {
+  pimpl_->enabled_ = enabled;
   if (pimpl_->parent_menu_) {
     EnableMenuItem(pimpl_->parent_menu_, pimpl_->id_, enabled ? MF_ENABLED : MF_GRAYED);
   }
 }
 
 bool MenuItem::IsEnabled() const {
-  if (pimpl_->parent_menu_) {
-    UINT state = GetMenuState(pimpl_->parent_menu_, pimpl_->id_, MF_BYCOMMAND);
-    if (state != (UINT)-1) {
-      return !(state & MF_GRAYED);
-    }
-  }
-  return true;
+  return pimpl_->enabled_;
 }
 
 void MenuItem::SetState(MenuItemState state) {
@@ -575,9 +572,15 @@ void Menu::AddItem(std::shared_ptr<MenuItem> item) {
   if (item->GetType() == MenuItemType::Separator) {
     flags = MF_SEPARATOR;
   } else if (item->GetType() == MenuItemType::Checkbox) {
-    flags |= MF_UNCHECKED;
+    flags |= (item->GetState() == MenuItemState::Checked) ? MF_CHECKED
+                                                           : MF_UNCHECKED;
   } else if (item->GetType() == MenuItemType::Radio) {
-    flags |= MF_UNCHECKED;
+    flags |= (item->GetState() == MenuItemState::Checked) ? MF_CHECKED
+                                                           : MF_UNCHECKED;
+  }
+
+  if (!item->IsEnabled()) {
+    flags |= MF_GRAYED;
   }
 
   UINT_PTR menu_id = item->GetId();
@@ -611,12 +614,31 @@ void Menu::InsertItem(size_t index, std::shared_ptr<MenuItem> item) {
   UINT flags = MF_STRING | MF_BYPOSITION;
   if (item->GetType() == MenuItemType::Separator) {
     flags = MF_SEPARATOR | MF_BYPOSITION;
+  } else if (item->GetType() == MenuItemType::Checkbox) {
+    flags |= (item->GetState() == MenuItemState::Checked) ? MF_CHECKED
+                                                           : MF_UNCHECKED;
+  } else if (item->GetType() == MenuItemType::Radio) {
+    flags |= (item->GetState() == MenuItemState::Checked) ? MF_CHECKED
+                                                           : MF_UNCHECKED;
+  }
+
+  if (!item->IsEnabled()) {
+    flags |= MF_GRAYED;
+  }
+
+  UINT_PTR menu_id = item->GetId();
+  if (item->GetSubmenu()) {
+    auto sub_menu =
+        static_cast<HMENU>(item->GetSubmenu()->GetNativeObject());
+    flags |= MF_POPUP;
+    menu_id = reinterpret_cast<UINT_PTR>(sub_menu);
   }
 
   auto label_opt = item->GetLabel();
   std::string label_str = label_opt.has_value() ? *label_opt : "";
   std::wstring w_label_str = StringToWString(label_str);
-  InsertMenuW(pimpl_->hmenu_, static_cast<UINT>(index), flags, item->GetId(), w_label_str.c_str());
+  InsertMenuW(pimpl_->hmenu_, static_cast<UINT>(index), flags, menu_id,
+              w_label_str.c_str());
 
   item->pimpl_->parent_menu_ = pimpl_->hmenu_;
 }