WindowServer+LibGUI: Automatically close child windows with parent

If a window has child windows when it's destroyed, WindowServer will
now automatically tear down all of its children as well.

This is communicated to the client program through a vector of window
ID's included with the response to WindowServer::DestroyWindow.

This does feel a little bit awkward, but managing it on the client side
also seems a bit awkward.

Libraries/LibGUI/Window.cpp

@@ -126,18 +126,29 @@ Window* Window::find_parent_window()
     return nullptr;
 }
 
-void Window::hide()
+void Window::server_did_destroy()
 {
-    if (!is_visible())
-        return;
-    reified_windows->remove(m_window_id);
-    WindowServerConnection::the().send_sync<Messages::WindowServer::DestroyWindow>(m_window_id);
     m_window_id = 0;
     m_visible = false;
     m_pending_paint_event_rects.clear();
     m_back_bitmap = nullptr;
     m_front_bitmap = nullptr;
     m_override_cursor = StandardCursor::None;
+}
+
+void Window::hide()
+{
+    if (!is_visible())
+        return;
+    reified_windows->remove(m_window_id);
+    auto response = WindowServerConnection::the().send_sync<Messages::WindowServer::DestroyWindow>(m_window_id);
+    server_did_destroy();
+
+    for (auto child_window_id : response->destroyed_window_ids()) {
+        if (auto* window = Window::from_window_id(child_window_id)) {
+            window->server_did_destroy();
+        }
+    }
 
     bool app_has_visible_windows = false;
     for (auto& window : *all_windows) {

Libraries/LibGUI/Window.h

@@ -191,6 +191,8 @@ protected:
 private:
     virtual bool is_window() const override final { return true; }
 
+    void server_did_destroy();
+
     RefPtr<Gfx::Bitmap> create_backing_bitmap(const Gfx::Size&);
     RefPtr<Gfx::Bitmap> create_shared_bitmap(Gfx::BitmapFormat, const Gfx::Size&);
     void set_current_backing_bitmap(Gfx::Bitmap&, bool flush_immediately = false);

Servers/WindowServer/ClientConnection.cpp

@@ -472,6 +472,10 @@ OwnPtr<Messages::WindowServer::CreateWindowResponse> ClientConnection::handle(co
             did_misbehave("CreateWindow with bad parent_window_id");
             return nullptr;
         }
+        if (parent_window->window_id() == window_id) {
+            did_misbehave("CreateWindow trying to make a window with itself as parent");
+            return nullptr;
+        }
         window->set_parent_window(*parent_window);
     }
 
@@ -497,6 +501,25 @@ OwnPtr<Messages::WindowServer::CreateWindowResponse> ClientConnection::handle(co
     return make<Messages::WindowServer::CreateWindowResponse>(window_id);
 }
 
+void ClientConnection::destroy_window(Window& window, Vector<i32>& destroyed_window_ids)
+{
+    for (auto& child_window : window.child_windows()) {
+        if (!child_window)
+            continue;
+        ASSERT(child_window->window_id() != window.window_id());
+        destroy_window(*child_window, destroyed_window_ids);
+    }
+
+    destroyed_window_ids.append(window.window_id());
+
+    if (window.type() == WindowType::MenuApplet)
+        AppletManager::the().remove_applet(window);
+
+    WindowManager::the().invalidate(window);
+    remove_child(window);
+    m_windows.remove(window.window_id());
+}
+
 OwnPtr<Messages::WindowServer::DestroyWindowResponse> ClientConnection::handle(const Messages::WindowServer::DestroyWindow& message)
 {
     auto it = m_windows.find(message.window_id());
@@ -505,16 +528,9 @@ OwnPtr<Messages::WindowServer::DestroyWindowResponse> ClientConnection::handle(c
         return nullptr;
     }
     auto& window = *(*it).value;
-
+    Vector<i32> destroyed_window_ids;
-    if (window.type() == WindowType::MenuApplet)
+    destroy_window(window, destroyed_window_ids);
-        AppletManager::the().remove_applet(window);
+    return make<Messages::WindowServer::DestroyWindowResponse>(destroyed_window_ids);
-
-    WindowManager::the().invalidate(window);
-    remove_child(window);
-    ASSERT(it->value.ptr() == &window);
-    m_windows.remove(message.window_id());
-
-    return make<Messages::WindowServer::DestroyWindowResponse>();
 }
 
 void ClientConnection::post_paint_message(Window& window, bool ignore_occlusion)

Servers/WindowServer/ClientConnection.h

@@ -79,6 +79,8 @@ public:
 private:
     explicit ClientConnection(Core::LocalSocket&, int client_id);
 
+    void destroy_window(Window&, Vector<i32>& destroyed_window_ids);
+
     virtual OwnPtr<Messages::WindowServer::GreetResponse> handle(const Messages::WindowServer::Greet&) override;
     virtual OwnPtr<Messages::WindowServer::CreateMenubarResponse> handle(const Messages::WindowServer::CreateMenubar&) override;
     virtual OwnPtr<Messages::WindowServer::DestroyMenubarResponse> handle(const Messages::WindowServer::DestroyMenubar&) override;

Servers/WindowServer/WindowServer.ipc

@@ -44,7 +44,7 @@ endpoint WindowServer = 2
         String title,
         i32 parent_window_id) => (i32 window_id)
 
-    DestroyWindow(i32 window_id) => ()
+    DestroyWindow(i32 window_id) => (Vector<i32> destroyed_window_ids)
 
     SetWindowTitle(i32 window_id, String title) => ()
     GetWindowTitle(i32 window_id) => (String title)