diff --git a/Applications/About/main.cpp b/Applications/About/main.cpp
index b98b4ca496..045b02681d 100644
--- a/Applications/About/main.cpp
+++ b/Applications/About/main.cpp
@@ -14,7 +14,7 @@ int main(int argc, char** argv)
     Rect window_rect { 0, 0, 240, 120 };
     window_rect.center_within({ 0, 0, 1024, 768 });
     window->set_rect(window_rect);
-    window->set_should_exit_app_on_close(true);
+    window->set_should_exit_event_loop_on_close(true);
 
     auto* widget = new GWidget;
     window->set_main_widget(widget);
diff --git a/Applications/FileManager/main.cpp b/Applications/FileManager/main.cpp
index a3a9eafed3..d7b4ab5c9d 100644
--- a/Applications/FileManager/main.cpp
+++ b/Applications/FileManager/main.cpp
@@ -29,7 +29,7 @@ int main(int argc, char** argv)
     auto* window = new GWindow;
     window->set_title("FileManager");
     window->set_rect(20, 200, 640, 480);
-    window->set_should_exit_app_on_close(true);
+    window->set_should_exit_event_loop_on_close(true);
 
     auto* widget = new GWidget;
     widget->set_layout(make<GBoxLayout>(Orientation::Vertical));
diff --git a/Applications/FontEditor/main.cpp b/Applications/FontEditor/main.cpp
index bf0511e6da..36f5e1d402 100644
--- a/Applications/FontEditor/main.cpp
+++ b/Applications/FontEditor/main.cpp
@@ -29,7 +29,7 @@ int main(int argc, char** argv)
     window->set_rect({ 50, 50, 420, 300 });
     auto* font_editor = new FontEditorWidget(path, move(edited_font));
     window->set_main_widget(font_editor);
-    window->set_should_exit_app_on_close(true);
+    window->set_should_exit_event_loop_on_close(true);
     window->show();
     return app.exec();
 }
diff --git a/Applications/IRCClient/IRCAppWindow.cpp b/Applications/IRCClient/IRCAppWindow.cpp
index d61e56fcf3..1b431ecbd6 100644
--- a/Applications/IRCClient/IRCAppWindow.cpp
+++ b/Applications/IRCClient/IRCAppWindow.cpp
@@ -9,6 +9,7 @@
 #include <LibGUI/GAction.h>
 #include <LibGUI/GMenu.h>
 #include <LibGUI/GMenuBar.h>
+#include <LibGUI/GMessageBox.h>
 #include <stdio.h>
 
 IRCAppWindow::IRCAppWindow()
@@ -40,6 +41,9 @@ void IRCAppWindow::setup_client()
     };
 
     m_client.on_connect = [this] {
+        GMessageBox box("We are connected!", "Message");
+        int code = box.exec();
+        dbgprintf("GMessageBox::exec() returned %d\n", code);
         m_client.join_channel("#test");
     };
 
diff --git a/Applications/Launcher/main.cpp b/Applications/Launcher/main.cpp
index 44aca4d460..616df66b0b 100644
--- a/Applications/Launcher/main.cpp
+++ b/Applications/Launcher/main.cpp
@@ -27,7 +27,7 @@ int main(int argc, char** argv)
     signal(SIGCHLD, handle_sigchld);
 
     auto* launcher_window = make_launcher_window();
-    launcher_window->set_should_exit_app_on_close(true);
+    launcher_window->set_should_exit_event_loop_on_close(true);
     launcher_window->show();
 
     return app.exec();
diff --git a/Applications/ProcessManager/main.cpp b/Applications/ProcessManager/main.cpp
index 14008e63b7..38bfdde050 100644
--- a/Applications/ProcessManager/main.cpp
+++ b/Applications/ProcessManager/main.cpp
@@ -71,7 +71,7 @@ int main(int argc, char** argv)
     window->set_title("ProcessManager");
     window->set_rect(20, 200, 640, 400);
     window->set_main_widget(widget);
-    window->set_should_exit_app_on_close(true);
+    window->set_should_exit_event_loop_on_close(true);
     window->show();
 
     return app.exec();
diff --git a/Applications/Terminal/main.cpp b/Applications/Terminal/main.cpp
index 808b14e9b3..a3cba5d296 100644
--- a/Applications/Terminal/main.cpp
+++ b/Applications/Terminal/main.cpp
@@ -89,7 +89,7 @@ int main(int argc, char** argv)
 
     auto* window = new GWindow;
     window->set_double_buffering_enabled(false);
-    window->set_should_exit_app_on_close(true);
+    window->set_should_exit_event_loop_on_close(true);
 
     Terminal terminal(ptm_fd);
     window->set_has_alpha_channel(true);
diff --git a/Applications/TextEditor/main.cpp b/Applications/TextEditor/main.cpp
index 4df7073241..16023de124 100644
--- a/Applications/TextEditor/main.cpp
+++ b/Applications/TextEditor/main.cpp
@@ -136,7 +136,7 @@ int main(int argc, char** argv)
     window->set_title(String::format("TextEditor: %s", path.characters()));
     window->set_rect(20, 200, 640, 400);
     window->set_main_widget(widget);
-    window->set_should_exit_app_on_close(true);
+    window->set_should_exit_event_loop_on_close(true);
     text_editor->set_focus(true);
     window->show();
 
diff --git a/Kernel/makeall.sh b/Kernel/makeall.sh
index 2929983813..d246871f3f 100755
--- a/Kernel/makeall.sh
+++ b/Kernel/makeall.sh
@@ -12,12 +12,12 @@ $make_cmd -C ../LibM && \
 (cd ../LibM && ./install.sh) && \
 $make_cmd -C ../LibM clean && \
 $make_cmd -C ../LibM clean && \
+$make_cmd -C ../WindowServer clean && \
+$make_cmd -C ../WindowServer && \
 $make_cmd -C ../LibGUI clean && \
 $make_cmd -C ../LibGUI && \
 $make_cmd -C ../Userland clean && \
 $make_cmd -C ../Userland && \
-$make_cmd -C ../WindowServer clean && \
-$make_cmd -C ../WindowServer && \
 $make_cmd -C ../Applications/Terminal clean && \
 $make_cmd -C ../Applications/Terminal && \
 $make_cmd -C ../Applications/FontEditor clean && \
diff --git a/LibGUI/GBoxLayout.cpp b/LibGUI/GBoxLayout.cpp
index 9abea5ed62..8e5ecad875 100644
--- a/LibGUI/GBoxLayout.cpp
+++ b/LibGUI/GBoxLayout.cpp
@@ -37,7 +37,8 @@ void GBoxLayout::run(GWidget& widget)
     should_log = true;
 #endif
     if (should_log)
-        printf("GBoxLayout: running layout on %s{%p}\n", widget.class_name(), &widget);
+        printf("GBoxLayout: running layout on %s{%p}, entry count: %d\n", widget.class_name(), &widget, m_entries.size());
+
     if (m_entries.is_empty())
         return;
 
diff --git a/LibGUI/GButton.cpp b/LibGUI/GButton.cpp
index 4b1a35b988..9023aaac19 100644
--- a/LibGUI/GButton.cpp
+++ b/LibGUI/GButton.cpp
@@ -13,11 +13,11 @@ GButton::~GButton()
 {
 }
 
-void GButton::set_caption(String&& caption)
+void GButton::set_caption(const String& caption)
 {
     if (caption == m_caption)
         return;
-    m_caption = move(caption);
+    m_caption = caption;
     update();
 }
 
diff --git a/LibGUI/GButton.h b/LibGUI/GButton.h
index d5897a5d7a..3e76476d15 100644
--- a/LibGUI/GButton.h
+++ b/LibGUI/GButton.h
@@ -12,7 +12,7 @@ public:
     virtual ~GButton() override;
 
     String caption() const { return m_caption; }
-    void set_caption(String&&);
+    void set_caption(const String&);
 
     void set_icon(RetainPtr<GraphicsBitmap>&& icon) { m_icon = move(icon); }
     const GraphicsBitmap* icon() const { return m_icon.ptr(); }
diff --git a/LibGUI/GClipboard.cpp b/LibGUI/GClipboard.cpp
index d6fe9efba3..9a349a157d 100644
--- a/LibGUI/GClipboard.cpp
+++ b/LibGUI/GClipboard.cpp
@@ -19,7 +19,7 @@ String GClipboard::data() const
 {
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::GetClipboardContents;
-    auto response = GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidGetClipboardContents);
+    auto response = GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidGetClipboardContents);
     if (response.clipboard.shared_buffer_id < 0)
         return { };
     auto shared_buffer = SharedBuffer::create_from_shared_buffer_id(response.clipboard.shared_buffer_id);
@@ -38,7 +38,7 @@ void GClipboard::set_data(const String& data)
 {
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::SetClipboardContents;
-    auto shared_buffer = SharedBuffer::create(GEventLoop::main().server_pid(), data.length() + 1);
+    auto shared_buffer = SharedBuffer::create(GEventLoop::current().server_pid(), data.length() + 1);
     if (!shared_buffer) {
         dbgprintf("GClipboard::set_data() failed to create a shared buffer\n");
         return;
@@ -50,6 +50,6 @@ void GClipboard::set_data(const String& data)
     shared_buffer->seal();
     request.clipboard.shared_buffer_id = shared_buffer->shared_buffer_id();
     request.clipboard.contents_size = data.length();
-    auto response = GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidSetClipboardContents);
+    auto response = GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidSetClipboardContents);
     ASSERT(response.clipboard.shared_buffer_id == shared_buffer->shared_buffer_id());
 }
diff --git a/LibGUI/GDialog.cpp b/LibGUI/GDialog.cpp
new file mode 100644
index 0000000000..97f0c103c6
--- /dev/null
+++ b/LibGUI/GDialog.cpp
@@ -0,0 +1,26 @@
+#include <LibGUI/GDialog.h>
+#include <LibGUI/GEventLoop.h>
+
+GDialog::GDialog(GObject* parent)
+    : GWindow(parent)
+{
+    set_modal(true);
+    set_should_exit_event_loop_on_close(true);
+}
+
+GDialog::~GDialog()
+{
+}
+
+int GDialog::exec()
+{
+    GEventLoop loop;
+    show();
+    return loop.exec();
+}
+
+void GDialog::done(int result)
+{
+    m_result = result;
+    GEventLoop::current().quit(result);
+}
diff --git a/LibGUI/GDialog.h b/LibGUI/GDialog.h
new file mode 100644
index 0000000000..9dcf88a772
--- /dev/null
+++ b/LibGUI/GDialog.h
@@ -0,0 +1,19 @@
+#pragma once
+
+#include <LibGUI/GWindow.h>
+
+class GDialog : public GWindow {
+public:
+    virtual ~GDialog() override;
+
+    int exec();
+
+    int result() const { return m_result; }
+    void done(int result);
+
+protected:
+    explicit GDialog(GObject* parent);
+
+private:
+    int m_result { 0 };
+};
diff --git a/LibGUI/GEventLoop.cpp b/LibGUI/GEventLoop.cpp
index 2015a65ae7..ed9aba0726 100644
--- a/LibGUI/GEventLoop.cpp
+++ b/LibGUI/GEventLoop.cpp
@@ -21,11 +21,16 @@
 
 static HashMap<GShortcut, GAction*>* g_actions;
 static GEventLoop* s_main_event_loop;
+static Vector<GEventLoop*>* s_event_loop_stack;
 int GEventLoop::s_event_fd = -1;
 pid_t GEventLoop::s_server_pid = -1;
+HashMap<int, OwnPtr<GEventLoop::EventLoopTimer>>* GEventLoop::s_timers;
+HashTable<GNotifier*>* GEventLoop::s_notifiers;
+int GEventLoop::s_next_timer_id = 1;
 
 void GEventLoop::connect_to_server()
 {
+    ASSERT(s_event_fd == -1);
     s_event_fd = socket(AF_LOCAL, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
     if (s_event_fd < 0) {
         perror("socket");
@@ -51,12 +56,25 @@ void GEventLoop::connect_to_server()
     if (rc < 0) {
         ASSERT_NOT_REACHED();
     }
+
+    WSAPI_ClientMessage request;
+    request.type = WSAPI_ClientMessage::Type::Greeting;
+    request.greeting.client_pid = getpid();
+    auto response = sync_request(request, WSAPI_ServerMessage::Type::Greeting);
+    s_server_pid = response.greeting.server_pid;
 }
 
 GEventLoop::GEventLoop()
 {
+    if (!s_event_loop_stack) {
+        s_event_loop_stack = new Vector<GEventLoop*>;
+        s_timers = new HashMap<int, OwnPtr<GEventLoop::EventLoopTimer>>;
+        s_notifiers = new HashTable<GNotifier*>;
+    }
+
     if (!s_main_event_loop) {
         s_main_event_loop = this;
+        s_event_loop_stack->append(this);
         connect_to_server();
     }
 
@@ -78,14 +96,41 @@ GEventLoop& GEventLoop::main()
     return *s_main_event_loop;
 }
 
+GEventLoop& GEventLoop::current()
+{
+    return *s_event_loop_stack->last();
+}
+
 void GEventLoop::quit(int code)
 {
     m_exit_requested = true;
     m_exit_code = code;
 }
 
+struct GEventLoopPusher {
+public:
+    GEventLoopPusher(GEventLoop& event_loop) : m_event_loop(event_loop)
+    {
+        if (&m_event_loop != s_main_event_loop) {
+            m_event_loop.take_pending_events_from(GEventLoop::current());
+            s_event_loop_stack->append(&event_loop);
+        }
+    }
+    ~GEventLoopPusher()
+    {
+        if (&m_event_loop != s_main_event_loop) {
+            s_event_loop_stack->take_last();
+            GEventLoop::current().take_pending_events_from(m_event_loop);
+        }
+    }
+private:
+    GEventLoop& m_event_loop;
+};
+
 int GEventLoop::exec()
 {
+    GEventLoopPusher pusher(*this);
+
     m_running = true;
     for (;;) {
         if (m_exit_requested)
@@ -228,7 +273,7 @@ void GEventLoop::wait_for_event()
     };
 
     add_fd_to_set(s_event_fd, rfds);
-    for (auto& notifier : m_notifiers) {
+    for (auto& notifier : *s_notifiers) {
         if (notifier->event_mask() & GNotifier::Read)
             add_fd_to_set(notifier->fd(), rfds);
         if (notifier->event_mask() & GNotifier::Write)
@@ -238,15 +283,15 @@ void GEventLoop::wait_for_event()
     }
 
     struct timeval timeout = { 0, 0 };
-    if (!m_timers.is_empty() && m_queued_events.is_empty())
+    if (!s_timers->is_empty() && m_queued_events.is_empty())
         get_next_timer_expiration(timeout);
     ASSERT(m_unprocessed_messages.is_empty());
-    int rc = select(max_fd + 1, &rfds, &wfds, nullptr, (m_queued_events.is_empty() && m_timers.is_empty()) ? nullptr : &timeout);
+    int rc = select(max_fd + 1, &rfds, &wfds, nullptr, (m_queued_events.is_empty() && s_timers->is_empty()) ? nullptr : &timeout);
     if (rc < 0) {
         ASSERT_NOT_REACHED();
     }
 
-    for (auto& it : m_timers) {
+    for (auto& it : *s_timers) {
         auto& timer = *it.value;
         if (!timer.has_expired())
             continue;
@@ -262,7 +307,7 @@ void GEventLoop::wait_for_event()
         }
     }
 
-    for (auto& notifier : m_notifiers) {
+    for (auto& notifier : *s_notifiers) {
         if (FD_ISSET(notifier->fd(), &rfds)) {
             if (notifier->on_ready_to_read)
                 notifier->on_ready_to_read(*notifier);
@@ -378,9 +423,9 @@ void GEventLoop::EventLoopTimer::reload()
 
 void GEventLoop::get_next_timer_expiration(timeval& soonest)
 {
-    ASSERT(!m_timers.is_empty());
+    ASSERT(!s_timers->is_empty());
     bool has_checked_any = false;
-    for (auto& it : m_timers) {
+    for (auto& it : *s_timers) {
         auto& fire_time = it.value->fire_time;
         if (!has_checked_any || fire_time.tv_sec < soonest.tv_sec || (fire_time.tv_sec == soonest.tv_sec && fire_time.tv_usec < soonest.tv_usec))
             soonest = fire_time;
@@ -396,30 +441,30 @@ int GEventLoop::register_timer(GObject& object, int milliseconds, bool should_re
     timer->interval = milliseconds;
     timer->reload();
     timer->should_reload = should_reload;
-    int timer_id = ++m_next_timer_id;  // FIXME: This will eventually wrap around.
+    int timer_id = ++s_next_timer_id;  // FIXME: This will eventually wrap around.
     ASSERT(timer_id); // FIXME: Aforementioned wraparound.
     timer->timer_id = timer_id;
-    m_timers.set(timer->timer_id, move(timer));
+    s_timers->set(timer->timer_id, move(timer));
     return timer_id;
 }
 
 bool GEventLoop::unregister_timer(int timer_id)
 {
-    auto it = m_timers.find(timer_id);
-    if (it == m_timers.end())
+    auto it = s_timers->find(timer_id);
+    if (it == s_timers->end())
         return false;
-    m_timers.remove(it);
+    s_timers->remove(it);
     return true;
 }
 
 void GEventLoop::register_notifier(Badge<GNotifier>, GNotifier& notifier)
 {
-    m_notifiers.set(&notifier);
+    s_notifiers->set(&notifier);
 }
 
 void GEventLoop::unregister_notifier(Badge<GNotifier>, GNotifier& notifier)
 {
-    m_notifiers.remove(&notifier);
+    s_notifiers->remove(&notifier);
 }
 
 bool GEventLoop::post_message_to_server(const WSAPI_ClientMessage& message)
@@ -456,7 +501,7 @@ WSAPI_ServerMessage GEventLoop::sync_request(const WSAPI_ClientMessage& request,
     ASSERT(success);
 
     WSAPI_ServerMessage response;
-    success = GEventLoop::main().wait_for_specific_event(response_type, response);
+    success = wait_for_specific_event(response_type, response);
     ASSERT(success);
     return response;
 }
diff --git a/LibGUI/GEventLoop.h b/LibGUI/GEventLoop.h
index 325115e70a..14ea43bd41 100644
--- a/LibGUI/GEventLoop.h
+++ b/LibGUI/GEventLoop.h
@@ -23,14 +23,15 @@ public:
     void post_event(GObject& receiver, OwnPtr<GEvent>&&);
 
     static GEventLoop& main();
+    static GEventLoop& current();
 
     bool running() const { return m_running; }
 
-    int register_timer(GObject&, int milliseconds, bool should_reload);
-    bool unregister_timer(int timer_id);
+    static int register_timer(GObject&, int milliseconds, bool should_reload);
+    static bool unregister_timer(int timer_id);
 
-    void register_notifier(Badge<GNotifier>, GNotifier&);
-    void unregister_notifier(Badge<GNotifier>, GNotifier&);
+    static void register_notifier(Badge<GNotifier>, GNotifier&);
+    static void unregister_notifier(Badge<GNotifier>, GNotifier&);
 
     void quit(int);
 
@@ -41,6 +42,12 @@ public:
 
     static pid_t server_pid() { return s_server_pid; }
 
+    void take_pending_events_from(GEventLoop& other)
+    {
+        m_queued_events.append(move(other.m_queued_events));
+        m_unprocessed_messages.append(move(other.m_unprocessed_messages));
+    }
+
 private:
     void wait_for_event();
     bool drain_messages_from_server();
@@ -67,7 +74,6 @@ private:
     bool m_running { false };
     bool m_exit_requested { false };
     int m_exit_code { 0 };
-    int m_next_timer_id { 1 };
 
     static pid_t s_server_pid;
     static pid_t s_event_fd;
@@ -83,6 +89,8 @@ private:
         bool has_expired() const;
     };
 
-    HashMap<int, OwnPtr<EventLoopTimer>> m_timers;
-    HashTable<GNotifier*> m_notifiers;
+    static HashMap<int, OwnPtr<EventLoopTimer>>* s_timers;
+    static int s_next_timer_id;
+
+    static HashTable<GNotifier*>* s_notifiers;
 };
diff --git a/LibGUI/GMenu.cpp b/LibGUI/GMenu.cpp
index 69ecad518d..54712228ce 100644
--- a/LibGUI/GMenu.cpp
+++ b/LibGUI/GMenu.cpp
@@ -46,7 +46,7 @@ int GMenu::realize_menu()
     ASSERT(m_name.length() < (ssize_t)sizeof(request.text));
     strcpy(request.text, m_name.characters());
     request.text_length = m_name.length();
-    auto response = GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidCreateMenu);
+    auto response = GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidCreateMenu);
     m_menu_id = response.menu.menu_id;
 
     ASSERT(m_menu_id > 0);
@@ -56,7 +56,7 @@ int GMenu::realize_menu()
             WSAPI_ClientMessage request;
             request.type = WSAPI_ClientMessage::Type::AddMenuSeparator;
             request.menu.menu_id = m_menu_id;
-            GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidAddMenuSeparator);
+            GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidAddMenuSeparator);
             continue;
         }
         if (item.type() == GMenuItem::Action) {
@@ -78,7 +78,7 @@ int GMenu::realize_menu()
                 request.menu.shortcut_text_length = 0;
             }
 
-            GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidAddMenuItem);
+            GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidAddMenuItem);
         }
     }
     all_menus().set(m_menu_id, this);
@@ -93,7 +93,7 @@ void GMenu::unrealize_menu()
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::DestroyMenu;
     request.menu.menu_id = m_menu_id;
-    GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidDestroyMenu);
+    GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidDestroyMenu);
     m_menu_id = 0;
 }
 
diff --git a/LibGUI/GMenuBar.cpp b/LibGUI/GMenuBar.cpp
index 1cce445e69..8befe45944 100644
--- a/LibGUI/GMenuBar.cpp
+++ b/LibGUI/GMenuBar.cpp
@@ -19,7 +19,7 @@ int GMenuBar::realize_menubar()
 {
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::CreateMenubar;
-    WSAPI_ServerMessage response = GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidCreateMenubar);
+    WSAPI_ServerMessage response = GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidCreateMenubar);
     return response.menu.menubar_id;
 }
 
@@ -30,7 +30,7 @@ void GMenuBar::unrealize_menubar()
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::DestroyMenubar;
     request.menu.menubar_id = m_menubar_id;
-    GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidDestroyMenubar);
+    GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidDestroyMenubar);
     m_menubar_id = 0;
 }
 
@@ -47,12 +47,12 @@ void GMenuBar::notify_added_to_application(Badge<GApplication>)
         request.type = WSAPI_ClientMessage::Type::AddMenuToMenubar;
         request.menu.menubar_id = m_menubar_id;
         request.menu.menu_id = menu_id;
-        GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidAddMenuToMenubar);
+        GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidAddMenuToMenubar);
     }
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::SetApplicationMenubar;
     request.menu.menubar_id = m_menubar_id;
-    GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidSetApplicationMenubar);
+    GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidSetApplicationMenubar);
 }
 
 void GMenuBar::notify_removed_from_application(Badge<GApplication>)
diff --git a/LibGUI/GMessageBox.cpp b/LibGUI/GMessageBox.cpp
new file mode 100644
index 0000000000..8f97cca5bd
--- /dev/null
+++ b/LibGUI/GMessageBox.cpp
@@ -0,0 +1,45 @@
+#include <LibGUI/GMessageBox.h>
+#include <LibGUI/GBoxLayout.h>
+#include <LibGUI/GLabel.h>
+#include <LibGUI/GButton.h>
+
+GMessageBox::GMessageBox(const String& text, const String& title, GObject* parent)
+    : GDialog(parent)
+    , m_text(text)
+{
+    set_title(title);
+    build();
+}
+
+GMessageBox::~GMessageBox()
+{
+}
+
+void GMessageBox::build()
+{
+    auto* widget = new GWidget;
+    set_main_widget(widget);
+
+    int text_width = widget->font().width(m_text);
+
+    set_rect(x(), y(), text_width + 80, 80);
+
+    widget->set_layout(make<GBoxLayout>(Orientation::Vertical));
+    widget->set_fill_with_background_color(true);
+
+    widget->layout()->set_margins({ 0, 15, 0, 15 });
+    widget->layout()->set_spacing(15);
+
+    auto* label = new GLabel(m_text, widget);
+    label->set_size_policy(SizePolicy::Fixed, SizePolicy::Fixed);
+    label->set_preferred_size({ text_width, 16 });
+
+    auto* button = new GButton(widget);
+    button->set_size_policy(SizePolicy::Fixed, SizePolicy::Fixed);
+    button->set_preferred_size({ 100, 16 });
+    button->set_caption("OK");
+    button->on_click = [this] (auto&) {
+        dbgprintf("OK button clicked\n");
+        done(0);
+    };
+}
diff --git a/LibGUI/GMessageBox.h b/LibGUI/GMessageBox.h
new file mode 100644
index 0000000000..fbbc371fba
--- /dev/null
+++ b/LibGUI/GMessageBox.h
@@ -0,0 +1,16 @@
+#pragma once
+
+#include <LibGUI/GDialog.h>
+
+class GMessageBox : public GDialog {
+public:
+    explicit GMessageBox(const String& text, const String& title, GObject* parent = nullptr);
+    virtual ~GMessageBox() override;
+
+    String text() const { return m_text; }
+
+    void build();
+
+private:
+    String m_text;
+};
diff --git a/LibGUI/GNotifier.cpp b/LibGUI/GNotifier.cpp
index 1d5ad6c816..649cc84bcc 100644
--- a/LibGUI/GNotifier.cpp
+++ b/LibGUI/GNotifier.cpp
@@ -5,11 +5,11 @@ GNotifier::GNotifier(int fd, unsigned event_mask)
     : m_fd(fd)
     , m_event_mask(event_mask)
 {
-    GEventLoop::main().register_notifier(Badge<GNotifier>(), *this);
+    GEventLoop::register_notifier(Badge<GNotifier>(), *this);
 }
 
 GNotifier::~GNotifier()
 {
-    GEventLoop::main().unregister_notifier(Badge<GNotifier>(), *this);
+    GEventLoop::unregister_notifier(Badge<GNotifier>(), *this);
 }
 
diff --git a/LibGUI/GObject.cpp b/LibGUI/GObject.cpp
index 1d2c59b427..4dbbe4bc0b 100644
--- a/LibGUI/GObject.cpp
+++ b/LibGUI/GObject.cpp
@@ -2,6 +2,7 @@
 #include "GEvent.h"
 #include "GEventLoop.h"
 #include <AK/Assertions.h>
+#include <stdio.h>
 
 GObject::GObject(GObject* parent)
     : m_parent(parent)
@@ -42,7 +43,7 @@ void GObject::event(GEvent& event)
 void GObject::add_child(GObject& object)
 {
     m_children.append(&object);
-    GEventLoop::main().post_event(*this, make<GChildEvent>(GEvent::ChildAdded, object));
+    GEventLoop::current().post_event(*this, make<GChildEvent>(GEvent::ChildAdded, object));
 }
 
 void GObject::remove_child(GObject& object)
@@ -50,7 +51,7 @@ void GObject::remove_child(GObject& object)
     for (ssize_t i = 0; i < m_children.size(); ++i) {
         if (m_children[i] == &object) {
             m_children.remove(i);
-            GEventLoop::main().post_event(*this, make<GChildEvent>(GEvent::ChildRemoved, object));
+            GEventLoop::current().post_event(*this, make<GChildEvent>(GEvent::ChildRemoved, object));
             return;
         }
     }
@@ -71,20 +72,32 @@ void GObject::start_timer(int ms)
         ASSERT_NOT_REACHED();
     }
 
-    m_timer_id = GEventLoop::main().register_timer(*this, ms, true);
+    m_timer_id = GEventLoop::register_timer(*this, ms, true);
 }
 
 void GObject::stop_timer()
 {
     if (!m_timer_id)
         return;
-    bool success = GEventLoop::main().unregister_timer(m_timer_id);
+    bool success = GEventLoop::unregister_timer(m_timer_id);
     ASSERT(success);
     m_timer_id = 0;
 }
 
 void GObject::delete_later()
 {
-    GEventLoop::main().post_event(*this, make<GEvent>(GEvent::DeferredDestroy));
+    GEventLoop::current().post_event(*this, make<GEvent>(GEvent::DeferredDestroy));
 }
 
+void GObject::dump_tree(int indent)
+{
+    for (int i = 0; i < indent; ++i) {
+        printf(" ");
+    }
+    printf("%s{%p}\n", class_name(), this);
+
+    for (auto* child : children()) {
+        child->dump_tree(indent + 2);
+    }
+
+}
diff --git a/LibGUI/GObject.h b/LibGUI/GObject.h
index b1f24462fe..694112dace 100644
--- a/LibGUI/GObject.h
+++ b/LibGUI/GObject.h
@@ -30,6 +30,8 @@ public:
 
     void delete_later();
 
+    void dump_tree(int indent = 0);
+
     virtual bool is_widget() const { return false; }
 
 protected:
diff --git a/LibGUI/GWindow.cpp b/LibGUI/GWindow.cpp
index 8486489f16..3dd4b9557a 100644
--- a/LibGUI/GWindow.cpp
+++ b/LibGUI/GWindow.cpp
@@ -44,10 +44,8 @@ GWindow::~GWindow()
 
 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().quit(0);
+    if (should_exit_event_loop_on_close())
+        GEventLoop::current().quit(0);
     delete_later();
 }
 
@@ -67,7 +65,7 @@ void GWindow::show()
     ASSERT(m_title_when_windowless.length() < (ssize_t)sizeof(request.text));
     strcpy(request.text, m_title_when_windowless.characters());
     request.text_length = m_title_when_windowless.length();
-    auto response = GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidCreateWindow);
+    auto response = GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidCreateWindow);
     m_window_id = response.window_id;
 
     windows().set(m_window_id, this);
@@ -82,12 +80,12 @@ void GWindow::hide()
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::DestroyWindow;
     request.window_id = m_window_id;
-    GEventLoop::main().post_message_to_server(request);
+    GEventLoop::current().post_message_to_server(request);
 }
 
-void GWindow::set_title(String&& title)
+void GWindow::set_title(const String& title)
 {
-    m_title_when_windowless = move(title);
+    m_title_when_windowless = title;
     if (!m_window_id)
         return;
 
@@ -97,7 +95,7 @@ void GWindow::set_title(String&& title)
     ASSERT(m_title_when_windowless.length() < (ssize_t)sizeof(request.text));
     strcpy(request.text, m_title_when_windowless.characters());
     request.text_length = m_title_when_windowless.length();
-    GEventLoop::main().post_message_to_server(request);
+    GEventLoop::current().post_message_to_server(request);
 }
 
 String GWindow::title() const
@@ -108,7 +106,7 @@ String GWindow::title() const
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::GetWindowTitle;
     request.window_id = m_window_id;
-    auto response = GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidGetWindowTitle);
+    auto response = GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidGetWindowTitle);
     return String(response.text, response.text_length);
 }
 
@@ -120,7 +118,7 @@ Rect GWindow::rect() const
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::GetWindowRect;
     request.window_id = m_window_id;
-    auto response = GEventLoop::main().sync_request(request, WSAPI_ServerMessage::Type::DidGetWindowRect);
+    auto response = GEventLoop::current().sync_request(request, WSAPI_ServerMessage::Type::DidGetWindowRect);
     ASSERT(response.window_id == m_window_id);
     return response.window.rect;
 }
@@ -128,13 +126,16 @@ Rect GWindow::rect() const
 void GWindow::set_rect(const Rect& a_rect)
 {
     m_rect_when_windowless = a_rect;
-    if (!m_window_id)
+    if (!m_window_id) {
+        if (m_main_widget)
+            m_main_widget->resize(m_rect_when_windowless.size());
         return;
+    }
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::SetWindowRect;
     request.window_id = m_window_id;
     request.window.rect = a_rect;
-    GEventLoop::main().post_message_to_server(request);
+    GEventLoop::current().post_message_to_server(request);
 }
 
 void GWindow::event(GEvent& event)
@@ -185,7 +186,7 @@ void GWindow::event(GEvent& event)
             message.type = WSAPI_ClientMessage::Type::DidFinishPainting;
             message.window_id = m_window_id;
             message.window.rect = rect;
-            GEventLoop::main().post_message_to_server(message);
+            GEventLoop::current().post_message_to_server(message);
         }
         return;
     }
@@ -255,7 +256,7 @@ void GWindow::update(const Rect& a_rect)
     request.type = WSAPI_ClientMessage::Type::InvalidateRect;
     request.window_id = m_window_id;
     request.window.rect = a_rect;
-    GEventLoop::main().post_message_to_server(request);
+    GEventLoop::current().post_message_to_server(request);
 }
 
 void GWindow::set_main_widget(GWidget* widget)
@@ -283,12 +284,12 @@ void GWindow::set_focused_widget(GWidget* widget)
     if (m_focused_widget == widget)
         return;
     if (m_focused_widget) {
-        GEventLoop::main().post_event(*m_focused_widget, make<GEvent>(GEvent::FocusOut));
+        GEventLoop::current().post_event(*m_focused_widget, make<GEvent>(GEvent::FocusOut));
         m_focused_widget->update();
     }
     m_focused_widget = widget;
     if (m_focused_widget) {
-        GEventLoop::main().post_event(*m_focused_widget, make<GEvent>(GEvent::FocusIn));
+        GEventLoop::current().post_event(*m_focused_widget, make<GEvent>(GEvent::FocusIn));
         m_focused_widget->update();
     }
 }
@@ -306,7 +307,7 @@ void GWindow::set_global_cursor_tracking_widget(GWidget* widget)
     request.value = widget != nullptr;
     // FIXME: What if the cursor moves out of our interest range before the server can handle this?
     //        Maybe there could be a response that includes the current cursor location as of enabling.
-    GEventLoop::main().post_message_to_server(request);
+    GEventLoop::current().post_message_to_server(request);
 }
 
 void GWindow::set_has_alpha_channel(bool value)
@@ -331,7 +332,7 @@ void GWindow::set_opacity(float opacity)
     request.window_id = m_window_id;
     request.window.opacity = opacity;
     m_opacity_when_windowless = opacity;
-    GEventLoop::main().post_message_to_server(request);
+    GEventLoop::current().post_message_to_server(request);
 }
 
 void GWindow::set_hovered_widget(GWidget* widget)
@@ -340,12 +341,12 @@ void GWindow::set_hovered_widget(GWidget* widget)
         return;
 
     if (m_hovered_widget)
-        GEventLoop::main().post_event(*m_hovered_widget, make<GEvent>(GEvent::Leave));
+        GEventLoop::current().post_event(*m_hovered_widget, make<GEvent>(GEvent::Leave));
 
     m_hovered_widget = widget ? widget->make_weak_ptr() : nullptr;
 
     if (m_hovered_widget)
-        GEventLoop::main().post_event(*m_hovered_widget, make<GEvent>(GEvent::Enter));
+        GEventLoop::current().post_event(*m_hovered_widget, make<GEvent>(GEvent::Enter));
 }
 
 void GWindow::set_current_backing_bitmap(GraphicsBitmap& bitmap, bool flush_immediately)
@@ -359,7 +360,7 @@ void GWindow::set_current_backing_bitmap(GraphicsBitmap& bitmap, bool flush_imme
     message.backing.has_alpha_channel = bitmap.has_alpha_channel();
     message.backing.size = bitmap.size();
     message.backing.flush_immediately = flush_immediately;
-    GEventLoop::main().sync_request(message, WSAPI_ServerMessage::Type::DidSetWindowBackingStore);
+    GEventLoop::current().sync_request(message, WSAPI_ServerMessage::Type::DidSetWindowBackingStore);
 }
 
 void GWindow::flip(const Rect& dirty_rect)
@@ -389,3 +390,9 @@ Retained<GraphicsBitmap> GWindow::create_backing_bitmap(const Size& size)
     auto format = m_has_alpha_channel ? GraphicsBitmap::Format::RGBA32 : GraphicsBitmap::Format::RGB32;
     return GraphicsBitmap::create_with_shared_buffer(format, *shared_buffer, size);
 }
+
+void GWindow::set_modal(bool modal)
+{
+    ASSERT(!m_window_id);
+    m_modal = modal;
+}
diff --git a/LibGUI/GWindow.h b/LibGUI/GWindow.h
index 16abab6cbf..3874887c5f 100644
--- a/LibGUI/GWindow.h
+++ b/LibGUI/GWindow.h
@@ -15,6 +15,9 @@ public:
 
     static GWindow* from_window_id(int);
 
+    bool is_modal() const { return m_modal; }
+    void set_modal(bool);
+
     void set_double_buffering_enabled(bool);
     void set_has_alpha_channel(bool);
     void set_opacity(float);
@@ -22,7 +25,7 @@ public:
     int window_id() const { return m_window_id; }
 
     String title() const;
-    void set_title(String&&);
+    void set_title(const String&);
 
     int x() const { return rect().x(); }
     int y() const { return rect().y(); }
@@ -62,8 +65,8 @@ 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; }
+    bool should_exit_event_loop_on_close() const { return m_should_exit_app_on_close; }
+    void set_should_exit_event_loop_on_close(bool b) { m_should_exit_app_on_close = b; }
 
     GWidget* hovered_widget() { return m_hovered_widget.ptr(); }
     const GWidget* hovered_widget() const { return m_hovered_widget.ptr(); }
@@ -101,5 +104,6 @@ private:
     bool m_should_exit_app_on_close { false };
     bool m_has_alpha_channel { false };
     bool m_double_buffering_enabled { true };
+    bool m_modal { false };
 };
 
diff --git a/LibGUI/Makefile b/LibGUI/Makefile
index 098c3cf779..025391745a 100644
--- a/LibGUI/Makefile
+++ b/LibGUI/Makefile
@@ -42,6 +42,8 @@ LIBGUI_OBJS = \
     GScrollableWidget.o \
     GSocket.o \
     GTCPSocket.o \
+    GMessageBox.o \
+    GDialog.o \
     GWindow.o
 
 OBJS = $(SHAREDGRAPHICS_OBJS) $(LIBGUI_OBJS)
diff --git a/Userland/guitest2.cpp b/Userland/guitest2.cpp
index f91cf451e7..4e8e593b67 100644
--- a/Userland/guitest2.cpp
+++ b/Userland/guitest2.cpp
@@ -35,7 +35,7 @@ int main(int argc, char** argv)
     signal(SIGCHLD, handle_sigchld);
 
     auto* launcher_window = make_launcher_window();
-    launcher_window->set_should_exit_app_on_close(true);
+    launcher_window->set_should_exit_event_loop_on_close(true);
     launcher_window->show();
 
     return app.exec();
diff --git a/WindowServer/WSAPITypes.h b/WindowServer/WSAPITypes.h
index bcf075cca9..65dce5e0af 100644
--- a/WindowServer/WSAPITypes.h
+++ b/WindowServer/WSAPITypes.h
@@ -164,6 +164,7 @@ struct WSAPI_ClientMessage {
         SetWindowBackingStore,
         GetClipboardContents,
         SetClipboardContents,
+        Greeting,
     };
     Type type { Invalid };
     int window_id { -1 };
@@ -172,6 +173,9 @@ struct WSAPI_ClientMessage {
     int value { 0 };
 
     union {
+        struct {
+            int client_pid;
+        } greeting;
         struct {
             int menubar_id;
             int menu_id;