3 files changed, 12 insertions, 5 deletions
diff --git a/src/ui/control.cpp b/src/ui/control.cpp
index 7691dac2..5417f4ce 100644
--- a/src/ui/control.cpp
+++ b/src/ui/control.cpp
@@ -33,12 +33,12 @@ void Control::_SetParent(Control* parent) {
 }
 
 void Control::_SetDescendantUiHost(UiHost* host) {
+  if (host == nullptr && ui_host_ == nullptr) return;
+
   // You can only attach or detach window.
   Expects((host != nullptr && ui_host_ == nullptr) ||
           (host == nullptr && ui_host_ != nullptr));
 
-  if (host == nullptr && ui_host_ == nullptr) return;
-
   if (host == nullptr) {
     const auto old = ui_host_;
     TraverseDescendants([old](Control* control) {
diff --git a/src/ui/ui_host.cpp b/src/ui/ui_host.cpp
index c82709dd..8b85ad30 100644
--- a/src/ui/ui_host.cpp
+++ b/src/ui/ui_host.cpp
@@ -101,7 +101,7 @@ UiHost::UiHost(Window* window)
       IUiApplication::GetInstance()->CreateWindow(nullptr);
 
   const auto native_window = native_window_resolver_->Resolve();
-  window->_SetDescendantUiHost(this);
+  window->ui_host_ = this;
 
   root_render_object_ = std::make_unique<render::WindowRenderObject>(this);
   root_render_object_->SetAttachedControl(window);
@@ -130,8 +130,15 @@ UiHost::UiHost(Window* window)
 }
 
 UiHost::~UiHost() {
+  deleting_ = true;
   window_control_->TraverseDescendants(
       [this](Control* control) { control->OnDetachFromHost(this); });
+  if (!native_window_destroyed_) {
+    const auto native_window = native_window_resolver_->Resolve();
+    if (native_window) {
+      native_window->Close();
+    }
+  }
 }
 
 void UiHost::InvalidatePaint() {
@@ -216,7 +223,8 @@ Control* UiHost::GetMouseCaptureControl() { return mouse_captured_control_; }
 
 void UiHost::OnNativeDestroy(INativeWindow* window, std::nullptr_t) {
   CRU_UNUSED(window)
-  delete this;  // TODO: Develop this.
+  native_window_destroyed_ = true;
+  if (!deleting_ && !retain_after_destroy_) delete window_control_;
 }
 
 void UiHost::OnNativePaint(INativeWindow* window, std::nullptr_t) {
diff --git a/src/ui/window.cpp b/src/ui/window.cpp
index 4f414385..7c0683af 100644
--- a/src/ui/window.cpp
+++ b/src/ui/window.cpp
@@ -4,7 +4,6 @@
 #include "cru/ui/ui_host.hpp"
 
 namespace cru::ui {
-
 Window* Window::CreateOverlapped() {
   return new Window(tag_overlapped_constructor{});
 }