LibGUI: Some more convenience functions for constructing widgets

This patch adds two new API's:

- WidgetType& GUI::Window::set_main_widget<WidgetType>();

  This creates a new main widget for a window, assigns it, and returns
  it to you as a WidgetType&.

- LayoutType& GUI::Widget::set_layout<LayoutType>();

  Same basic idea, creates a new layout, assigns it, and returns it to
  you as a LayoutType&.

10 files changed, 68 insertions, 62 deletions

diff --git a/Applications/About/main.cpp b/Applications/About/main.cpp
index c1467cf39b..d8f5c33b07 100644
--- a/Applications/About/main.cpp
+++ b/Applications/About/main.cpp
@@ -63,21 +63,20 @@ int main(int argc, char** argv)
     window->set_resizable(false);
     window->set_rect(window_rect);
 
-    auto outer_widget = GUI::Widget::construct();
-    window->set_main_widget(outer_widget);
-    outer_widget->set_fill_with_background_color(true);
-    outer_widget->set_layout(make<GUI::VerticalBoxLayout>());
-    outer_widget->layout()->set_margins({ 8, 8, 8, 8 });
-
-    auto inner_widget = outer_widget->add<GUI::Widget>();
-    inner_widget->set_layout(make<GUI::HorizontalBoxLayout>());
+    auto& outer_widget = window->set_main_widget<GUI::Widget>();
+    outer_widget.set_fill_with_background_color(true);
+    outer_widget.set_layout<GUI::VerticalBoxLayout>();
+    outer_widget.layout()->set_margins({ 8, 8, 8, 8 });
+
+    auto inner_widget = outer_widget.add<GUI::Widget>();
+    inner_widget->set_layout<GUI::HorizontalBoxLayout>();
     inner_widget->layout()->set_spacing(8);
 
     auto left_outer_container = inner_widget->add<GUI::Widget>();
-    left_outer_container->set_layout(make<GUI::HorizontalBoxLayout>());
+    left_outer_container->set_layout<GUI::HorizontalBoxLayout>();
 
     auto left_inner_container = left_outer_container->add<GUI::Widget>();
-    left_inner_container->set_layout(make<GUI::VerticalBoxLayout>());
+    left_inner_container->set_layout<GUI::VerticalBoxLayout>();
     left_inner_container->layout()->set_spacing(8);
     left_inner_container->set_preferred_size(0, 50);
     left_inner_container->set_size_policy(GUI::SizePolicy::Fill, GUI::SizePolicy::Fixed);
@@ -106,7 +105,7 @@ int main(int argc, char** argv)
     git_info_label->set_preferred_size(0, 11);
 
     auto right_container = inner_widget->add<GUI::Widget>();
-    right_container->set_layout(make<GUI::VerticalBoxLayout>());
+    right_container->set_layout<GUI::VerticalBoxLayout>();
 
     auto icon_label = right_container->add<GUI::Label>();
     icon_label->set_icon(Gfx::Bitmap::load_from_file("/res/icons/buggie.png"));
@@ -114,7 +113,7 @@ int main(int argc, char** argv)
     icon_label->set_size_policy(GUI::SizePolicy::Fixed, GUI::SizePolicy::Fixed);
     icon_label->set_preferred_size(icon_label->icon()->size());
 
-    auto quit_button = outer_widget->add<GUI::Button>();
+    auto quit_button = outer_widget.add<GUI::Button>();
     quit_button->set_text("Okay");
     quit_button->set_size_policy(GUI::SizePolicy::Fixed, GUI::SizePolicy::Fixed);
     quit_button->set_preferred_size(100, 20);
diff --git a/Applications/Browser/main.cpp b/Applications/Browser/main.cpp
index e38824896c..61e9c3da69 100644
--- a/Applications/Browser/main.cpp
+++ b/Applications/Browser/main.cpp
@@ -75,13 +75,13 @@ int main(int argc, char** argv)
     auto window = GUI::Window::construct();
     window->set_rect(100, 100, 640, 480);
 
-    auto widget = GUI::Widget::construct();
-    widget->set_fill_with_background_color(true);
-    widget->set_layout(make<GUI::VerticalBoxLayout>());
-    widget->layout()->set_spacing(0);
+    auto& widget = window->set_main_widget<GUI::Widget>();
+    widget.set_fill_with_background_color(true);
+    widget.set_layout<GUI::VerticalBoxLayout>();
+    widget.layout()->set_spacing(0);
 
-    auto toolbar = widget->add<GUI::ToolBar>();
-    auto html_widget = widget->add<HtmlView>();
+    auto toolbar = widget.add<GUI::ToolBar>();
+    auto html_widget = widget.add<HtmlView>();
 
     History<URL> history;
 
@@ -151,7 +151,7 @@ int main(int argc, char** argv)
         location_box->set_focus(true);
     });
 
-    auto statusbar = widget->add<GUI::StatusBar>();
+    auto statusbar = widget.add<GUI::StatusBar>();
 
     html_widget->on_link_hover = [&](auto& href) {
         statusbar->set_text(href);
@@ -200,8 +200,7 @@ int main(int argc, char** argv)
             dom_inspector_window = GUI::Window::construct();
             dom_inspector_window->set_rect(100, 100, 300, 500);
             dom_inspector_window->set_title("DOM inspector");
-            auto dom_inspector_widget = InspectorWidget::construct();
-            dom_inspector_window->set_main_widget(dom_inspector_widget);
+            dom_inspector_window->set_main_widget<InspectorWidget>();
         }
         auto* inspector_widget = static_cast<InspectorWidget*>(dom_inspector_window->main_widget());
         inspector_widget->set_document(html_widget->document());
@@ -244,7 +243,6 @@ int main(int argc, char** argv)
     window->set_icon(Gfx::Bitmap::load_from_file("/res/icons/16x16/filetype-html.png"));
 
     window->set_title("Browser");
-    window->set_main_widget(widget);
     window->show();
 
     URL url_to_load = home_url;
diff --git a/Applications/Calculator/main.cpp b/Applications/Calculator/main.cpp
index 6b166c5e25..772564f4a4 100644
--- a/Applications/Calculator/main.cpp
+++ b/Applications/Calculator/main.cpp
@@ -60,8 +60,7 @@ int main(int argc, char** argv)
     window->set_resizable(false);
     window->set_rect({ 300, 200, 254, 213 });
 
-    auto calc_widget = CalculatorWidget::construct();
-    window->set_main_widget(calc_widget);
+    window->set_main_widget<CalculatorWidget>();
 
     window->show();
     window->set_icon(Gfx::Bitmap::load_from_file("/res/icons/16x16/app-calculator.png"));
diff --git a/Applications/ChanViewer/main.cpp b/Applications/ChanViewer/main.cpp
index 1f874fc2b7..0cf00598b9 100644
--- a/Applications/ChanViewer/main.cpp
+++ b/Applications/ChanViewer/main.cpp
@@ -57,22 +57,21 @@ int main(int argc, char** argv)
     window->set_rect(100, 100, 800, 500);
     window->set_icon(Gfx::Bitmap::load_from_file("/res/icons/16x16/app-chanviewer.png"));
 
-    auto widget = GUI::Widget::construct();
-    window->set_main_widget(widget);
-    widget->set_fill_with_background_color(true);
-    widget->set_layout(make<GUI::VerticalBoxLayout>());
+    auto& widget = window->set_main_widget<GUI::Widget>();
+    widget.set_fill_with_background_color(true);
+    widget.set_layout<GUI::VerticalBoxLayout>();
 
-    auto board_combo = widget->add<GUI::ComboBox>();
+    auto board_combo = widget.add<GUI::ComboBox>();
     board_combo->set_only_allow_values_from_model(true);
     board_combo->set_size_policy(GUI::SizePolicy::Fill, GUI::SizePolicy::Fixed);
     board_combo->set_preferred_size(0, 20);
     board_combo->set_model(BoardListModel::create());
 
-    auto catalog_view = widget->add<GUI::TableView>();
+    auto catalog_view = widget.add<GUI::TableView>();
     catalog_view->set_model(ThreadCatalogModel::create());
     auto& catalog_model = *static_cast<ThreadCatalogModel*>(catalog_view->model());
 
-    auto statusbar = widget->add<GUI::StatusBar>();
+    auto statusbar = widget.add<GUI::StatusBar>();
 
     board_combo->on_change = [&] (auto&, const GUI::ModelIndex& index) {
         auto selected_board = board_combo->model()->data(index, GUI::Model::Role::Custom);
diff --git a/Applications/FileManager/PropertiesDialog.cpp b/Applications/FileManager/PropertiesDialog.cpp
index 4c43f069ca..3561de5e08 100644
--- a/Applications/FileManager/PropertiesDialog.cpp
+++ b/Applications/FileManager/PropertiesDialog.cpp
@@ -43,16 +43,15 @@ PropertiesDialog::PropertiesDialog(GUI::FileSystemModel& model, String path, boo
     auto file_path = FileSystemPath(path);
     ASSERT(file_path.is_valid());
 
-    auto main_widget = GUI::Widget::construct();
-    main_widget->set_layout(make<GUI::VerticalBoxLayout>());
-    main_widget->layout()->set_margins({ 4, 4, 4, 4 });
-    main_widget->set_fill_with_background_color(true);
+    auto& main_widget = set_main_widget<GUI::Widget>();
+    main_widget.set_layout(make<GUI::VerticalBoxLayout>());
+    main_widget.layout()->set_margins({ 4, 4, 4, 4 });
+    main_widget.set_fill_with_background_color(true);
 
-    set_main_widget(main_widget);
     set_rect({ 0, 0, 360, 420 });
     set_resizable(false);
 
-    auto tab_widget = main_widget->add<GUI::TabWidget>();
+    auto tab_widget = main_widget.add<GUI::TabWidget>();
 
     auto general_tab = tab_widget->add_tab<GUI::Widget>("General");
     general_tab->set_layout(make<GUI::VerticalBoxLayout>());
@@ -131,8 +130,8 @@ PropertiesDialog::PropertiesDialog(GUI::FileSystemModel& model, String path, boo
 
     general_tab->layout()->add_spacer();
 
-    auto button_widget = main_widget->add<GUI::Widget>();
-    button_widget->set_layout(make<GUI::HorizontalBoxLayout>());
+    auto button_widget = main_widget.add<GUI::Widget>();
+    button_widget->set_layout<GUI::HorizontalBoxLayout>();
     button_widget->set_size_policy(GUI::SizePolicy::Fill, GUI::SizePolicy::Fixed);
     button_widget->set_preferred_size(0, 24);
     button_widget->layout()->set_spacing(5);
diff --git a/Applications/FileManager/main.cpp b/Applications/FileManager/main.cpp
index f47c33150d..15ea2d6a6e 100644
--- a/Applications/FileManager/main.cpp
+++ b/Applications/FileManager/main.cpp
@@ -92,12 +92,12 @@ int main(int argc, char** argv)
     auto heigth = config->read_num_entry("Window", "Heigth", 480);
     window->set_rect({ left, top, width, heigth });
 
-    auto widget = GUI::Widget::construct();
-    widget->set_layout(make<GUI::VerticalBoxLayout>());
-    widget->layout()->set_spacing(0);
+    auto& widget = window->set_main_widget<GUI::Widget>();
+    widget.set_layout<GUI::VerticalBoxLayout>();
+    widget.layout()->set_spacing(0);
 
-    auto main_toolbar = widget->add<GUI::ToolBar>();
-    auto location_toolbar = widget->add<GUI::ToolBar>();
+    auto main_toolbar = widget.add<GUI::ToolBar>();
+    auto location_toolbar = widget.add<GUI::ToolBar>();
     location_toolbar->layout()->set_margins({ 6, 3, 6, 3 });
     location_toolbar->set_preferred_size(0, 25);
 
@@ -106,7 +106,7 @@ int main(int argc, char** argv)
 
     auto location_textbox = location_toolbar->add<GUI::TextBox>();
 
-    auto splitter = widget->add<GUI::HorizontalSplitter>();
+    auto splitter = widget.add<GUI::HorizontalSplitter>();
     auto tree_view = splitter->add<GUI::TreeView>();
     auto directories_model = GUI::FileSystemModel::create("/", GUI::FileSystemModel::Mode::DirectoriesOnly);
     tree_view->set_model(directories_model);
@@ -122,7 +122,7 @@ int main(int argc, char** argv)
     tree_view->set_preferred_size(150, 0);
     auto directory_view = splitter->add<DirectoryView>();
 
-    auto statusbar = widget->add<GUI::StatusBar>();
+    auto statusbar = widget.add<GUI::StatusBar>();
 
     auto progressbar = statusbar->add<GUI::ProgressBar>();
     progressbar->set_caption("Generating thumbnails: ");
@@ -641,7 +641,6 @@ int main(int argc, char** argv)
     directory_view->open(initial_location);
     directory_view->set_focus(true);
 
-    window->set_main_widget(widget);
     window->show();
 
     window->set_icon(Gfx::Bitmap::load_from_file("/res/icons/16x16/filetype-folder.png"));
diff --git a/Applications/Help/main.cpp b/Applications/Help/main.cpp
index 010a87f0e5..423bc5ef64 100644
--- a/Applications/Help/main.cpp
+++ b/Applications/Help/main.cpp
@@ -78,13 +78,13 @@ int main(int argc, char* argv[])
     window->set_title("Help");
     window->set_rect(300, 200, 570, 500);
 
-    auto widget = GUI::Widget::construct();
-    widget->set_layout(make<GUI::VerticalBoxLayout>());
-    widget->layout()->set_spacing(0);
+    auto& widget = window->set_main_widget<GUI::Widget>();
+    widget.set_layout<GUI::VerticalBoxLayout>();
+    widget.layout()->set_spacing(0);
 
-    auto toolbar = widget->add<GUI::ToolBar>();
+    auto toolbar = widget.add<GUI::ToolBar>();
 
-    auto splitter = widget->add<GUI::HorizontalSplitter>();
+    auto splitter = widget.add<GUI::HorizontalSplitter>();
 
     auto model = ManualModel::create();
 
@@ -195,7 +195,6 @@ int main(int argc, char* argv[])
 
     app.set_menubar(move(menubar));
 
-    window->set_main_widget(widget);
     window->set_focused_widget(tree_view);
     window->show();
 
diff --git a/Demos/HelloWorld/main.cpp b/Demos/HelloWorld/main.cpp
index 73ce17a3a0..14614c00ce 100644
--- a/Demos/HelloWorld/main.cpp
+++ b/Demos/HelloWorld/main.cpp
@@ -39,17 +39,16 @@ int main(int argc, char** argv)
     window->set_rect(100, 100, 240, 160);
     window->set_title("Hello World!");
 
-    auto main_widget = GUI::Widget::construct();
-    window->set_main_widget(main_widget);
-    main_widget->set_fill_with_background_color(true);
-    main_widget->set_background_color(Color::White);
-    main_widget->set_layout(make<GUI::VerticalBoxLayout>());
-    main_widget->layout()->set_margins({ 4, 4, 4, 4 });
-
-    auto label = main_widget->add<GUI::Label>();
+    auto& main_widget = window->set_main_widget<GUI::Widget>();
+    main_widget.set_fill_with_background_color(true);
+    main_widget.set_background_color(Color::White);
+    auto& layout = main_widget.set_layout<GUI::VerticalBoxLayout>();
+    layout.set_margins({ 4, 4, 4, 4 });
+
+    auto label = main_widget.add<GUI::Label>();
     label->set_text("Hello\nWorld!");
 
-    auto button = main_widget->add<GUI::Button>();
+    auto button = main_widget.add<GUI::Button>();
     button->set_text("Good-bye");
     button->set_size_policy(GUI::SizePolicy::Fill, GUI::SizePolicy::Fixed);
     button->set_preferred_size(0, 20);
diff --git a/Libraries/LibGUI/Widget.h b/Libraries/LibGUI/Widget.h
index 3de5ac95da..96795a94c4 100644
--- a/Libraries/LibGUI/Widget.h
+++ b/Libraries/LibGUI/Widget.h
@@ -98,6 +98,13 @@ public:
     const Layout* layout() const { return m_layout.ptr(); }
     void set_layout(OwnPtr<Layout>&&);
 
+    template<typename T>
+    T& set_layout()
+    {
+        set_layout(make<T>());
+        return static_cast<T&>(*layout());
+    }
+
     SizePolicy horizontal_size_policy() const { return m_horizontal_size_policy; }
     SizePolicy vertical_size_policy() const { return m_vertical_size_policy; }
     SizePolicy size_policy(Orientation orientation) { return orientation == Orientation::Horizontal ? m_horizontal_size_policy : m_vertical_size_policy; }
diff --git a/Libraries/LibGUI/Window.h b/Libraries/LibGUI/Window.h
index 65db147a96..c056637c50 100644
--- a/Libraries/LibGUI/Window.h
+++ b/Libraries/LibGUI/Window.h
@@ -125,6 +125,14 @@ public:
     const Widget* main_widget() const { return m_main_widget; }
     void set_main_widget(Widget*);
 
+    template<class T, class... Args>
+    inline T& set_main_widget(Args&&... args)
+    {
+        auto widget = T::construct(forward<Args>(args)...);
+        set_main_widget(widget.ptr());
+        return *widget;
+    }
+
     Widget* focused_widget() { return m_focused_widget; }
     const Widget* focused_widget() const { return m_focused_widget; }
     void set_focused_widget(Widget*);