Add a simple close button ("X") to windows.

Clicking the button generates a WindowCloseRequest event which the client app
then has to deal with. The default behavior for GWindow is to close() itself.

I also added a flag, GWindow::should_exit_event_loop_on_close() which does
what it sounds like it does.

This patch exposed some bugs in GWindow and GWidget teardown.

14 files changed, 103 insertions, 1 deletions

diff --git a/Clock/main.cpp b/Clock/main.cpp
index 483d5cc88f..98593d1905 100644
--- a/Clock/main.cpp
+++ b/Clock/main.cpp
@@ -8,7 +8,8 @@ int main(int, char**)
 
     auto* window = new GWindow;
     window->set_title("Clock");
-    window->set_rect({ 100, 100, 100, 40 });
+    window->set_rect({ 600, 100, 100, 40 });
+    window->set_should_exit_app_on_close(true);
 
     auto* clock_widget = new ClockWidget;
     clock_widget->set_relative_rect({ 0, 0, 100, 40 });
diff --git a/Kernel/GUITypes.h b/Kernel/GUITypes.h
index 9059ed96e4..61aa6587eb 100644
--- a/Kernel/GUITypes.h
+++ b/Kernel/GUITypes.h
@@ -66,6 +66,7 @@ struct GUI_Event {
         KeyUp,
         WindowActivated,
         WindowDeactivated,
+        WindowCloseRequest,
     };
     Type type { Invalid };
     int window_id { -1 };
diff --git a/LibGUI/GEvent.h b/LibGUI/GEvent.h
index 2e35aa4de8..52846cb0ae 100644
--- a/LibGUI/GEvent.h
+++ b/LibGUI/GEvent.h
@@ -24,6 +24,7 @@ public:
         WindowBecameActive,
         FocusIn,
         FocusOut,
+        WindowCloseRequest,
     };
 
     GEvent() { }
diff --git a/LibGUI/GEventLoop.cpp b/LibGUI/GEventLoop.cpp
index fa42115cf8..187f1df816 100644
--- a/LibGUI/GEventLoop.cpp
+++ b/LibGUI/GEventLoop.cpp
@@ -35,6 +35,12 @@ GEventLoop& GEventLoop::main()
     return *s_mainGEventLoop;
 }
 
+void GEventLoop::exit(int code)
+{
+    m_exit_requested = true;
+    m_exit_code = code;
+}
+
 int GEventLoop::exec()
 {
     m_event_fd = open("/dev/gui_events", O_RDONLY | O_NONBLOCK | O_CLOEXEC);
@@ -45,6 +51,8 @@ int GEventLoop::exec()
 
     m_running = true;
     for (;;) {
+        if (m_exit_requested)
+            return m_exit_code;
         if (m_queued_events.is_empty())
             wait_for_event();
         Vector<QueuedEvent> events = move(m_queued_events);
@@ -69,6 +77,7 @@ int GEventLoop::exec()
             }
         }
     }
+    ASSERT_NOT_REACHED();
 }
 
 void GEventLoop::post_event(GObject* receiver, OwnPtr<GEvent>&& event)
@@ -95,6 +104,11 @@ void GEventLoop::handle_window_activation_event(const GUI_Event& event, GWindow&
     post_event(&window, make<GEvent>(event.type == GUI_Event::Type::WindowActivated ? GEvent::WindowBecameActive : GEvent::WindowBecameInactive));
 }
 
+void GEventLoop::handle_window_close_request_event(const GUI_Event&, GWindow& window)
+{
+    post_event(&window, make<GEvent>(GEvent::WindowCloseRequest));
+}
+
 void GEventLoop::handle_key_event(const GUI_Event& event, GWindow& window)
 {
 #ifdef GEVENTLOOP_DEBUG
@@ -192,6 +206,9 @@ void GEventLoop::wait_for_event()
         case GUI_Event::Type::WindowDeactivated:
             handle_window_activation_event(event, *window);
             break;
+        case GUI_Event::Type::WindowCloseRequest:
+            handle_window_close_request_event(event, *window);
+            break;
         case GUI_Event::Type::KeyDown:
         case GUI_Event::Type::KeyUp:
             handle_key_event(event, *window);
diff --git a/LibGUI/GEventLoop.h b/LibGUI/GEventLoop.h
index e4063bf64b..ad5fce26c1 100644
--- a/LibGUI/GEventLoop.h
+++ b/LibGUI/GEventLoop.h
@@ -27,12 +27,15 @@ public:
     int register_timer(GObject&, int milliseconds, bool should_reload);
     bool unregister_timer(int timer_id);
 
+    void exit(int);
+
 private:
     void wait_for_event();
     void handle_paint_event(const GUI_Event&, GWindow&);
     void handle_mouse_event(const GUI_Event&, GWindow&);
     void handle_key_event(const GUI_Event&, GWindow&);
     void handle_window_activation_event(const GUI_Event&, GWindow&);
+    void handle_window_close_request_event(const GUI_Event&, GWindow&);
 
     void get_next_timer_expiration(timeval&);
 
@@ -44,6 +47,8 @@ private:
 
     int m_event_fd { -1 };
     bool m_running { false };
+    bool m_exit_requested { false };
+    int m_exit_code { 0 };
 
     int m_next_timer_id { 1 };
 
diff --git a/LibGUI/GObject.cpp b/LibGUI/GObject.cpp
index be8627dc86..985d459c00 100644
--- a/LibGUI/GObject.cpp
+++ b/LibGUI/GObject.cpp
@@ -12,6 +12,7 @@ GObject::GObject(GObject* parent)
 
 GObject::~GObject()
 {
+    stop_timer();
     if (m_parent)
         m_parent->remove_child(*this);
     auto children_to_delete = move(m_children);
diff --git a/LibGUI/GWindow.cpp b/LibGUI/GWindow.cpp
index 9b92536679..f5ec3cfc77 100644
--- a/LibGUI/GWindow.cpp
+++ b/LibGUI/GWindow.cpp
@@ -35,11 +35,17 @@ GWindow::GWindow(GObject* parent)
 
 GWindow::~GWindow()
 {
+    if (m_main_widget)
+        delete m_main_widget;
     hide();
 }
 
 void GWindow::close()
 {
+    // FIXME: If we exit the event loop, we're never gonna deal with the delete_later request!
+    //        This will become relevant once we support nested event loops.
+    if (should_exit_app_on_close())
+        GEventLoop::main().exit(0);
     delete_later();
 }
 
@@ -160,6 +166,11 @@ void GWindow::event(GEvent& event)
         return;
     }
 
+    if (event.type() == GEvent::WindowCloseRequest) {
+        close();
+        return;
+    }
+
     GObject::event(event);
 }
 
diff --git a/LibGUI/GWindow.h b/LibGUI/GWindow.h
index dc2549ee9f..33af06f2bb 100644
--- a/LibGUI/GWindow.h
+++ b/LibGUI/GWindow.h
@@ -53,6 +53,9 @@ public:
     GWidget* global_cursor_tracking_widget() { return m_global_cursor_tracking_widget.ptr(); }
     const GWidget* global_cursor_tracking_widget() const { return m_global_cursor_tracking_widget.ptr(); }
 
+    bool should_exit_app_on_close() const { return m_should_exit_app_on_close; }
+    void set_should_exit_app_on_close(bool b) { m_should_exit_app_on_close = b; }
+
 private:
     RetainPtr<GraphicsBitmap> m_backing;
     int m_window_id { 0 };
@@ -62,5 +65,6 @@ private:
     WeakPtr<GWidget> m_global_cursor_tracking_widget;
     Rect m_rect_when_windowless;
     String m_title_when_windowless;
+    bool m_should_exit_app_on_close { false };
 };
 
diff --git a/Terminal/main.cpp b/Terminal/main.cpp
index f6f2a47830..44b7b17d2a 100644
--- a/Terminal/main.cpp
+++ b/Terminal/main.cpp
@@ -149,6 +149,8 @@ int main(int, char**)
                 terminal.set_in_active_window(true);
             } else if (event.type == GUI_Event::Type::WindowDeactivated) {
                 terminal.set_in_active_window(false);
+            } else if (event.type == GUI_Event::Type::WindowCloseRequest) {
+                return 0;
             }
         }
     }
diff --git a/Userland/guitest2.cpp b/Userland/guitest2.cpp
index 92b254563b..54187c82a6 100644
--- a/Userland/guitest2.cpp
+++ b/Userland/guitest2.cpp
@@ -40,6 +40,7 @@ int main(int argc, char** argv)
 #endif
 
     auto* launcher_window = make_launcher_window();
+    launcher_window->set_should_exit_app_on_close(true);
     launcher_window->show();
 
     return loop.exec();
diff --git a/WindowServer/WSMessage.h b/WindowServer/WSMessage.h
index 87211001b0..f0c47897e2 100644
--- a/WindowServer/WSMessage.h
+++ b/WindowServer/WSMessage.h
@@ -22,6 +22,7 @@ public:
         KeyUp,
         WindowActivated,
         WindowDeactivated,
+        WindowCloseRequest,
     };
 
     WSMessage() { }
diff --git a/WindowServer/WSWindow.cpp b/WindowServer/WSWindow.cpp
index 8b6414c8ec..e98a7ed368 100644
--- a/WindowServer/WSWindow.cpp
+++ b/WindowServer/WSWindow.cpp
@@ -118,6 +118,9 @@ void WSWindow::on_message(WSMessage& message)
     case WSMessage::WindowDeactivated:
         gui_event.type = GUI_Event::Type::WindowDeactivated;
         break;
+    case WSMessage::WindowCloseRequest:
+        gui_event.type = GUI_Event::Type::WindowCloseRequest;
+        break;
     default:
         break;
     }
diff --git a/WindowServer/WSWindowManager.cpp b/WindowServer/WSWindowManager.cpp
index 225f0afce2..0912579891 100644
--- a/WindowServer/WSWindowManager.cpp
+++ b/WindowServer/WSWindowManager.cpp
@@ -36,6 +36,19 @@ static inline Rect title_bar_text_rect(const Rect& window)
     };
 }
 
+static inline Rect close_button_rect_for_window(const Rect& window_rect)
+{
+    auto titlebar_inner_rect = title_bar_text_rect(window_rect);
+    int close_button_margin = 1;
+    int close_button_size = titlebar_inner_rect.height() - close_button_margin * 2;
+    return Rect {
+        titlebar_inner_rect.right() - close_button_size,
+        titlebar_inner_rect.top() + close_button_margin,
+        close_button_size,
+        close_button_size
+    };
+}
+
 static inline Rect border_window_rect(const Rect& window)
 {
     auto titlebar_rect = title_bar_rect(window);
@@ -152,6 +165,22 @@ WSWindowManager::~WSWindowManager()
 {
 }
 
+static const char* s_close_button_bitmap_data = {
+    " ##     ## "
+    "  ##   ##  "
+    "   ## ##   "
+    "    ###    "
+    "     #     "
+    "    ###    "
+    "   ## ##   "
+    "  ##   ##  "
+    " ##     ## "
+};
+
+static CharacterBitmap* s_close_button_bitmap;
+static const int s_close_button_bitmap_width = 11;
+static const int s_close_button_bitmap_height = 11;
+
 void WSWindowManager::paint_window_frame(WSWindow& window)
 {
     LOCKER(m_lock);
@@ -204,6 +233,17 @@ void WSWindowManager::paint_window_frame(WSWindow& window)
     m_back_painter->draw_rect(inner_border_rect, border_color);
     m_back_painter->draw_text(titlebar_title_rect, window.title(), Painter::TextAlignment::CenterLeft, title_color);
 
+    Rect close_button_rect = close_button_rect_for_window(window.rect());
+    if (!s_close_button_bitmap)
+        s_close_button_bitmap = CharacterBitmap::create_from_ascii(s_close_button_bitmap_data, s_close_button_bitmap_width, s_close_button_bitmap_height).leak_ref();
+
+    m_back_painter->fill_rect_with_gradient(close_button_rect, Color::LightGray, Color::White);
+    m_back_painter->draw_rect(close_button_rect, Color::Black);
+    auto x_location = close_button_rect.location();
+    x_location.move_by(2, 2);
+    m_back_painter->draw_bitmap(x_location, *s_close_button_bitmap, Color::Black);
+
+
 #ifdef DEBUG_WID_IN_TITLE_BAR
     Color metadata_color(96, 96, 96);
     m_back_painter->draw_text(
@@ -276,6 +316,15 @@ void WSWindowManager::handle_titlebar_mouse_event(WSWindow& window, WSMouseEvent
     }
 }
 
+void WSWindowManager::handle_close_button_mouse_event(WSWindow& window, WSMouseEvent& event)
+{
+    if (event.type() == WSMessage::MouseDown && event.button() == MouseButton::Left) {
+        WSMessage message(WSMessage::WindowCloseRequest);
+        window.on_message(message);
+        return;
+    }
+}
+
 void WSWindowManager::process_mouse_event(WSMouseEvent& event)
 {
     if (event.type() == WSMessage::MouseUp && event.button() == MouseButton::Left) {
@@ -320,6 +369,10 @@ void WSWindowManager::process_mouse_event(WSMouseEvent& event)
                 move_to_front(*window);
                 set_active_window(window);
             }
+            if (close_button_rect_for_window(window->rect()).contains(event.position())) {
+                handle_close_button_mouse_event(*window, event);
+                return;
+            }
             handle_titlebar_mouse_event(*window, event);
             return;
         }
diff --git a/WindowServer/WSWindowManager.h b/WindowServer/WSWindowManager.h
index d55ea34791..dd3a7b17f3 100644
--- a/WindowServer/WSWindowManager.h
+++ b/WindowServer/WSWindowManager.h
@@ -48,6 +48,7 @@ private:
 
     void process_mouse_event(WSMouseEvent&);
     void handle_titlebar_mouse_event(WSWindow&, WSMouseEvent&);
+    void handle_close_button_mouse_event(WSWindow&, WSMouseEvent&);
 
     void set_active_window(WSWindow*);