LibCore: Make CObject reference-counted

Okay, I've spent a whole day on this now, and it finally kinda works!
With this patch, CObject and all of its derived classes are reference
counted instead of tree-owned.

The previous, Qt-like model was nice and familiar, but ultimately also
outdated and difficult to reason about.

CObject-derived types should now be stored in RefPtr/NonnullRefPtr and
each class can be constructed using the forwarding construct() helper:

    auto widget = GWidget::construct(parent_widget);

Note that construct() simply forwards all arguments to an existing
constructor. It is inserted into each class by the C_OBJECT macro,
see CObject.h to understand how that works.

CObject::delete_later() disappears in this patch, as there is no longer
a single logical owner of a CObject.

Applications/DisplayProperties/DisplayProperties.cpp

@@ -97,7 +97,7 @@ void DisplayPropertiesWidget::create_frame()
  auto background_splitter = GSplitter::construct(Orientation::Vertical, nullptr);
  tab_widget->add_widget("Wallpaper", background_splitter);
 
- auto background_content = GWidget::construct(background_splitter);
+ auto background_content = GWidget::construct(background_splitter.ptr());
  background_content->set_layout(make<GBoxLayout>(Orientation::Vertical));
  background_content->layout()->set_margins({ 4, 4, 4, 4 });
 
@@ -120,7 +120,7 @@ void DisplayPropertiesWidget::create_frame()
  auto settings_splitter = GSplitter::construct(Orientation::Vertical, nullptr);
  tab_widget->add_widget("Settings", settings_splitter);
 
- auto settings_content = GWidget::construct(settings_splitter);
+ auto settings_content = GWidget::construct(settings_splitter.ptr());
  settings_content->set_layout(make<GBoxLayout>(Orientation::Vertical));
  settings_content->layout()->set_margins({ 4, 4, 4, 4 });
 
@@ -135,7 +135,7 @@ void DisplayPropertiesWidget::create_frame()
  settings_content->layout()->add_spacer();
 
  // Add the apply and cancel buttons
- auto bottom_widget = GWidget::construct(m_root_widget);
+ auto bottom_widget = GWidget::construct(m_root_widget.ptr());
  bottom_widget->set_layout(make<GBoxLayout>(Orientation::Horizontal));
  bottom_widget->layout()->add_spacer();
  bottom_widget->set_size_policy(Orientation::Vertical, SizePolicy::Fixed);

Applications/IRCClient/IRCAppWindow.cpp

@@ -171,7 +171,7 @@ void IRCAppWindow::setup_widgets()
  toolbar->add_action(*m_open_query_action);
  toolbar->add_action(*m_close_query_action);
 
- auto outer_container = GWidget::construct(widget);
+ auto outer_container = GWidget::construct(widget.ptr());
  outer_container->set_layout(make<GBoxLayout>(Orientation::Vertical));
  outer_container->layout()->set_margins({ 2, 0, 2, 2 });
 

Applications/PaintBrush/ColorDialog.cpp

@@ -25,10 +25,10 @@ void ColorDialog::build()
  horizontal_container->layout()->set_margins({ 4, 4, 4, 4 });
  set_main_widget(horizontal_container);
 
- auto left_vertical_container = GWidget::construct(horizontal_container);
+ auto left_vertical_container = GWidget::construct(horizontal_container.ptr());
  left_vertical_container->set_layout(make<GBoxLayout>(Orientation::Vertical));
 
- auto right_vertical_container = GWidget::construct(horizontal_container);
+ auto right_vertical_container = GWidget::construct(horizontal_container.ptr());
  right_vertical_container->set_layout(make<GBoxLayout>(Orientation::Vertical));
 
  enum RGBComponent {

Applications/PaintBrush/PaletteWidget.cpp

@@ -87,11 +87,11 @@ PaletteWidget::PaletteWidget(PaintableWidget& paintable_widget, GWidget* parent)
  color_container->set_layout(make<GBoxLayout>(Orientation::Vertical));
  color_container->layout()->set_spacing(1);
 
- auto top_color_container = GWidget::construct(color_container);
+ auto top_color_container = GWidget::construct(color_container.ptr());
  top_color_container->set_layout(make<GBoxLayout>(Orientation::Horizontal));
  top_color_container->layout()->set_spacing(1);
 
- auto bottom_color_container = GWidget::construct(color_container);
+ auto bottom_color_container = GWidget::construct(color_container.ptr());
  bottom_color_container->set_layout(make<GBoxLayout>(Orientation::Horizontal));
  bottom_color_container->layout()->set_spacing(1);
 

Applications/PaintBrush/main.cpp

@@ -19,14 +19,14 @@ int main(int argc, char** argv)
  window->set_title("PaintBrush");
  window->set_rect(100, 100, 640, 480);
 
- auto horizontal_container = GWidget::construct(nullptr);
+ auto horizontal_container = GWidget::construct();
  window->set_main_widget(horizontal_container);
  horizontal_container->set_layout(make<GBoxLayout>(Orientation::Horizontal));
  horizontal_container->layout()->set_spacing(0);
 
  new ToolboxWidget(horizontal_container);
 
- auto vertical_container = GWidget::construct(horizontal_container);
+ auto vertical_container = GWidget::construct(horizontal_container.ptr());
  vertical_container->set_layout(make<GBoxLayout>(Orientation::Vertical));
  vertical_container->layout()->set_spacing(0);
 

Applications/Piano/main.cpp

@@ -14,8 +14,8 @@
 int main(int argc, char** argv)
 {
  GApplication app(argc, argv);
- AClientConnection audio_connection;
- audio_connection.handshake();
+ auto audio_client = AClientConnection::construct();
+ audio_client->handshake();
 
  auto window = GWindow::construct();
  window->set_title("Piano");

Applications/SoundPlayer/main.cpp

@@ -27,8 +27,8 @@ int main(int argc, char** argv)
  return 1;
  }
 
- AClientConnection audio_client;
- audio_client.handshake();
+ auto audio_client = AClientConnection::construct();
+ audio_client->handshake();
 
  auto window = GWindow::construct();
  window->set_title("SoundPlayer");
@@ -57,7 +57,7 @@ int main(int argc, char** argv)
  sample_widget->set_buffer(nullptr);
  return;
  }
- bool enqueued = audio_client.try_enqueue(*next_sample_buffer);
+ bool enqueued = audio_client->try_enqueue(*next_sample_buffer);
  if (!enqueued)
  return;
  sample_widget->set_buffer(next_sample_buffer);

Applications/SystemMonitor/main.cpp

@@ -58,7 +58,7 @@ int main(int argc, char** argv)
  auto process_container_splitter = GSplitter::construct(Orientation::Vertical, nullptr);
  tabwidget->add_widget("Processes", process_container_splitter);
 
- auto process_table_container = GWidget::construct(process_container_splitter);
+ auto process_table_container = GWidget::construct(process_container_splitter.ptr());
 
  auto graphs_container = GWidget::construct();
  graphs_container->set_fill_with_background_color(true);
@@ -301,7 +301,7 @@ ObjectPtr<GWidget> build_file_systems_tab()
 
 ObjectPtr<GWidget> build_pci_devices_tab()
 {
- auto pci_widget = GWidget::construct(nullptr);
+ auto pci_widget = GWidget::construct();
  pci_widget->set_layout(make<GBoxLayout>(Orientation::Vertical));
  pci_widget->layout()->set_margins({ 4, 4, 4, 4 });
  auto pci_table_view = GTableView::construct(pci_widget);

Applications/Taskbar/TaskbarWindow.cpp

@@ -46,7 +46,7 @@ void TaskbarWindow::on_screen_rect_change(const Rect& rect)
  set_rect(new_rect);
 }
 
-GButton* TaskbarWindow::create_button(const WindowIdentifier& identifier)
+NonnullRefPtr<GButton> TaskbarWindow::create_button(const WindowIdentifier& identifier)
 {
  auto button = TaskbarButton::construct(identifier, main_widget());
  button->set_size_policy(SizePolicy::Fixed, SizePolicy::Fixed);

Applications/Taskbar/TaskbarWindow.h

@@ -12,7 +12,7 @@ class TaskbarWindow final : public GWindow {
 
 private:
  void on_screen_rect_change(const Rect&);
- GButton* create_button(const WindowIdentifier&);
+ NonnullRefPtr<GButton> create_button(const WindowIdentifier&);
 
  virtual void wm_event(GWMEvent&) override;
 };

Applications/Taskbar/WindowList.h

@@ -15,7 +15,6 @@ class Window {
 
  ~Window()
  {
- delete m_button;
  }
 
  WindowIdentifier identifier() const { return m_identifier; }
@@ -41,7 +40,7 @@ class Window {
  WindowIdentifier m_identifier;
  String m_title;
  Rect m_rect;
- GButton* m_button { nullptr };
+ RefPtr<GButton> m_button;
  RefPtr<GraphicsBitmap> m_icon;
  bool m_active { false };
  bool m_minimized { false };
@@ -62,7 +61,7 @@ class WindowList {
  Window& ensure_window(const WindowIdentifier&);
  void remove_window(const WindowIdentifier&);
 
- Function<GButton*(const WindowIdentifier&)> aid_create_button;
+ Function<NonnullRefPtr<GButton>(const WindowIdentifier&)> aid_create_button;
 
 private:
  HashMap<WindowIdentifier, NonnullOwnPtr<Window>> m_windows;

Applications/Welcome/main.cpp

@@ -83,7 +83,7 @@ int main(int argc, char** argv)
  // header
  //
 
- auto header = GLabel::construct(background);
+ auto header = GLabel::construct(background.ptr());
  header->set_font(Font::default_bold_font());
  header->set_text("Welcome to Serenity");
  header->set_text_alignment(TextAlignment::CenterLeft);
@@ -94,13 +94,13 @@ int main(int argc, char** argv)
  // main section
  //
 
- auto main_section = GWidget::construct(background);
+ auto main_section = GWidget::construct(background.ptr());
  main_section->set_layout(make<GBoxLayout>(Orientation::Horizontal));
  main_section->layout()->set_margins({ 0, 0, 0, 0 });
  main_section->layout()->set_spacing(8);
  main_section->set_size_policy(SizePolicy::Fill, SizePolicy::Fill);
 
- auto menu = GWidget::construct(main_section);
+ auto menu = GWidget::construct(main_section.ptr());
  menu->set_layout(make<GBoxLayout>(Orientation::Vertical));
  menu->layout()->set_margins({ 0, 0, 0, 0 });
  menu->layout()->set_spacing(8);
@@ -111,7 +111,7 @@ int main(int argc, char** argv)
  stack->set_size_policy(SizePolicy::Fill, SizePolicy::Fill);
 
  for (auto& page : pages) {
- auto content = GWidget::construct(stack);
+ auto content = GWidget::construct(stack.ptr());
  content->set_layout(make<GBoxLayout>(Orientation::Vertical));
  content->layout()->set_margins({ 0, 0, 0, 0 });
  content->layout()->set_spacing(8);

Demos/WidgetGallery/main.cpp

@@ -66,7 +66,7 @@ int main(int argc, char** argv)
  auto spinbox2 = GSpinBox::construct(main_widget);
  spinbox2->set_enabled(false);
 
- auto vertical_slider_container = GWidget::construct(main_widget);
+ auto vertical_slider_container = GWidget::construct(main_widget.ptr());
  vertical_slider_container->set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
  vertical_slider_container->set_preferred_size(0, 100);
  vertical_slider_container->set_layout(make<GBoxLayout>(Orientation::Horizontal));

Games/Minesweeper/main.cpp

@@ -24,7 +24,7 @@ int main(int argc, char** argv)
  widget->set_layout(make<GBoxLayout>(Orientation::Vertical));
  widget->layout()->set_spacing(0);
 
- auto container = GWidget::construct(widget);
+ auto container = GWidget::construct(widget.ptr());
  container->set_fill_with_background_color(true);
  container->set_size_policy(SizePolicy::Fill, SizePolicy::Fixed);
  container->set_preferred_size(0, 36);

Libraries/LibCore/CEvent.h

@@ -15,7 +15,6 @@ class CEvent {
  Timer,
  NotifierRead,
  NotifierWrite,
- DeferredDestroy,
  DeferredInvoke,
  ChildAdded,
  ChildRemoved,

Libraries/LibCore/CEventLoop.cpp

@@ -43,7 +43,7 @@ class RPCClient : public CObject {
  int nread = m_socket->read((u8*)&length, sizeof(length));
  if (nread == 0) {
  dbg() << "RPC client disconnected";
- delete_later();
+ shutdown();
  return;
  }
  ASSERT(nread == sizeof(length));
@@ -52,7 +52,7 @@ class RPCClient : public CObject {
  auto request_json = JsonValue::from_string(request);
  if (!request_json.is_object()) {
  dbg() << "RPC client sent invalid request";
- delete_later();
+ shutdown();
  return;
  }
 
@@ -111,11 +111,17 @@ class RPCClient : public CObject {
  }
 
  if (type == "Disconnect") {
- delete_later();
+ shutdown();
  return;
  }
  }
 
+ void shutdown()
+ {
+ // FIXME: This is quite a hackish way to clean ourselves up.
+ delete this;
+ }
+
 private:
  ObjectPtr<CLocalSocket> m_socket;
 };
@@ -148,7 +154,8 @@ CEventLoop::CEventLoop()
  s_rpc_server->on_ready_to_accept = [&] {
  auto client_socket = s_rpc_server->accept();
  ASSERT(client_socket);
- new RPCClient(move(client_socket));
+ // NOTE: RPCClient will delete itself in RPCClient::shutdown().
+ (void)RPCClient::construct(move(client_socket)).leak_ref();
  };
  }
 
@@ -246,6 +253,7 @@ void CEventLoop::pump(WaitMode mode)
 #endif
  static_cast<CDeferredInvocationEvent&>(event).m_invokee(*receiver);
  } else {
+ NonnullRefPtr<CObject> protector(*receiver);
  receiver->dispatch_event(event);
  }
 

Libraries/LibCore/CObject.cpp

@@ -23,23 +23,25 @@ CObject::CObject(CObject* parent, bool is_widget)
 
 CObject::~CObject()
 {
+ // NOTE: We move our children out to a stack vector to prevent other
+ // code from trying to iterate over them.
+ auto children = move(m_children);
+ // NOTE: We also unparent the children, so that they won't try to unparent
+ // themselves in their own destructors.
+ for (auto& child : children)
+ child.m_parent = nullptr;
+
  all_objects().remove(*this);
  stop_timer();
  if (m_parent)
  m_parent->remove_child(*this);
- auto children_to_delete = move(m_children);
- for (auto* child : children_to_delete)
- delete child;
 }
 
 void CObject::event(CEvent& event)
 {
  switch (event.type()) {
  case CEvent::Timer:
  return timer_event(static_cast<CTimerEvent&>(event));
- case CEvent::DeferredDestroy:
- delete this;
- break;
  case CEvent::ChildAdded:
  case CEvent::ChildRemoved:
  return child_event(static_cast<CChildEvent&>(event));
@@ -58,19 +60,24 @@ void CObject::add_child(CObject& object)
  // FIXME: Should we support reparenting objects?
  ASSERT(!object.parent() || object.parent() == this);
  object.m_parent = this;
- m_children.append(&object);
+ m_children.append(object);
  event(*make<CChildEvent>(CEvent::ChildAdded, object));
 }
 
 void CObject::remove_child(CObject& object)
 {
- for (ssize_t i = 0; i < m_children.size(); ++i) {
- if (m_children[i] == &object) {
+ for (int i = 0; i < m_children.size(); ++i) {
+ dbg() << i << "] " << m_children.at(i);
+ if (m_children.ptr_at(i).ptr() == &object) {
+ // NOTE: We protect the child so it survives the handling of ChildRemoved.
+ NonnullRefPtr<CObject> protector = object;
+ object.m_parent = nullptr;
  m_children.remove(i);
  event(*make<CChildEvent>(CEvent::ChildRemoved, object));
  return;
  }
  }
+ ASSERT_NOT_REACHED();
 }
 
 void CObject::timer_event(CTimerEvent&)
@@ -104,11 +111,6 @@ void CObject::stop_timer()
  m_timer_id = 0;
 }
 
-void CObject::delete_later()
-{
- CEventLoop::current().post_event(*this, make<CEvent>(CEvent::DeferredDestroy));
-}
-
 void CObject::dump_tree(int indent)
 {
  for (int i = 0; i < indent; ++i) {