DisplaySettings: Tweak main window layout & setup code

Get rid of the menu and put some padding around the main tab widget.

Userland/Applications/DisplaySettings/main.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2019-2020, Jesse Buhagiar <jooster669@gmail.com>
+ * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -33,30 +34,21 @@ int main(int argc, char** argv)
 
     auto app_icon = GUI::Icon::default_icon("app-display-settings");
 
-    // Let's create the tab pane that we'll hook our widgets up to :^)
-    auto tab_widget = GUI::TabWidget::construct();
-    tab_widget->add_tab<DisplaySettingsWidget>("Display Settings");
-    tab_widget->set_fill_with_background_color(true); // No black backgrounds!
-
     auto window = GUI::Window::construct();
-    dbgln("main window: {}", window);
     window->set_title("Display Settings");
     window->resize(360, 410);
     window->set_resizable(false);
-    window->set_main_widget(tab_widget.ptr());
-    window->set_icon(app_icon.bitmap_for_size(16));
 
-    auto menubar = GUI::Menubar::construct();
+    auto& main_widget = window->set_main_widget<GUI::Widget>();
+    main_widget.set_fill_with_background_color(true);
+    main_widget.set_layout<GUI::VerticalBoxLayout>();
+    main_widget.layout()->set_margins({ 4, 4, 4, 4 });
 
-    auto& file_menu = menubar->add_menu("&File");
-    file_menu.add_action(GUI::CommonActions::make_quit_action([&](const GUI::Action&) {
-        app->quit();
-    }));
+    auto& tab_widget = main_widget.add<GUI::TabWidget>();
+    tab_widget.add_tab<DisplaySettingsWidget>("Display Settings");
 
-    auto& help_menu = menubar->add_menu("&Help");
-    help_menu.add_action(GUI::CommonActions::make_about_action("Display Settings", app_icon, window));
+    window->set_icon(app_icon.bitmap_for_size(16));
 
-    window->set_menubar(move(menubar));
     window->show();
     return app->exec();
 }