LibGUI: Move widget registration to LibCore

This also moves Widget::load_from_json into Core::Object as a virtual
function in order to allow loading non-widget objects in GML (e.g.
BoxLayout).

Co-authored-by: Gunnar Beutner <gbeutner@serenityos.org>

13 files changed, 134 insertions, 85 deletions

diff --git a/Userland/Applications/SpaceAnalyzer/TreeMapWidget.cpp b/Userland/Applications/SpaceAnalyzer/TreeMapWidget.cpp
index 2bc94a01e0..00cdf6ee0a 100644
--- a/Userland/Applications/SpaceAnalyzer/TreeMapWidget.cpp
+++ b/Userland/Applications/SpaceAnalyzer/TreeMapWidget.cpp
@@ -11,10 +11,10 @@
 #include <LibGfx/Font.h>
 #include <WindowServer/WindowManager.h>
 
-namespace SpaceAnalyzer {
-
 REGISTER_WIDGET(SpaceAnalyzer, TreeMapWidget)
 
+namespace SpaceAnalyzer {
+
 TreeMapWidget::TreeMapWidget()
     : m_viewpoint(0)
 {
diff --git a/Userland/DevTools/HackStudio/HackStudioWidget.cpp b/Userland/DevTools/HackStudio/HackStudioWidget.cpp
index 5082480f96..24214c5acc 100644
--- a/Userland/DevTools/HackStudio/HackStudioWidget.cpp
+++ b/Userland/DevTools/HackStudio/HackStudioWidget.cpp
@@ -799,7 +799,11 @@ void HackStudioWidget::create_form_editor(GUI::Widget& parent)
 
     form_widgets_toolbar.add_action(cursor_tool_action);
 
-    GUI::WidgetClassRegistration::for_each([&, this](const GUI::WidgetClassRegistration& reg) {
+    auto& widget_class = *Core::ObjectClassRegistration::find("GUI::Widget");
+
+    Core::ObjectClassRegistration::for_each([&, this](const Core::ObjectClassRegistration& reg) {
+        if (!reg.is_derived_from(widget_class))
+            return;
         constexpr size_t gui_namespace_prefix_length = sizeof("GUI::") - 1;
         auto icon_path = String::formatted("/res/icons/hackstudio/G{}.png",
             reg.class_name().substring(gui_namespace_prefix_length, reg.class_name().length() - gui_namespace_prefix_length));
@@ -808,7 +812,7 @@ void HackStudioWidget::create_form_editor(GUI::Widget& parent)
 
         auto action = GUI::Action::create_checkable(reg.class_name(), Gfx::Bitmap::load_from_file(icon_path), [&reg, this](auto&) {
             m_form_editor_widget->set_tool(make<WidgetTool>(*m_form_editor_widget, reg));
-            auto widget = reg.construct();
+            auto widget = static_ptr_cast<Widget>(reg.construct());
             m_form_editor_widget->form_widget().add_child(widget);
             widget->set_relative_rect(30, 30, 30, 30);
             m_form_editor_widget->model().update();
diff --git a/Userland/DevTools/HackStudio/Tool.h b/Userland/DevTools/HackStudio/Tool.h
index d6ca633ce6..d4899182f6 100644
--- a/Userland/DevTools/HackStudio/Tool.h
+++ b/Userland/DevTools/HackStudio/Tool.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/Noncopyable.h>
+#include <LibCore/Forward.h>
 #include <LibGUI/Forward.h>
 
 namespace HackStudio {
diff --git a/Userland/DevTools/HackStudio/WidgetTool.h b/Userland/DevTools/HackStudio/WidgetTool.h
index c5e506df99..0421c8416d 100644
--- a/Userland/DevTools/HackStudio/WidgetTool.h
+++ b/Userland/DevTools/HackStudio/WidgetTool.h
@@ -12,7 +12,7 @@ namespace HackStudio {
 
 class WidgetTool final : public Tool {
 public:
-    explicit WidgetTool(FormEditorWidget& editor, const GUI::WidgetClassRegistration& meta_class)
+    explicit WidgetTool(FormEditorWidget& editor, const Core::ObjectClassRegistration& meta_class)
         : Tool(editor)
         , m_meta_class(meta_class)
     {
@@ -26,7 +26,7 @@ private:
     virtual void on_mousemove(GUI::MouseEvent&) override;
     virtual void on_keydown(GUI::KeyEvent&) override;
 
-    const GUI::WidgetClassRegistration& m_meta_class;
+    const Core::ObjectClassRegistration& m_meta_class;
 };
 
 }
diff --git a/Userland/DevTools/Playground/GMLAutocompleteProvider.cpp b/Userland/DevTools/Playground/GMLAutocompleteProvider.cpp
index c5da1523cc..37c78e7fa4 100644
--- a/Userland/DevTools/Playground/GMLAutocompleteProvider.cpp
+++ b/Userland/DevTools/Playground/GMLAutocompleteProvider.cpp
@@ -102,6 +102,8 @@ void GMLAutocompleteProvider::provide_completions(Function<void(Vector<Entry>)>
         state = previous_states.take_last();
     }
 
+    auto& widget_class = *Core::ObjectClassRegistration::find("GUI::Widget");
+
     Vector<GUI::AutocompleteProvider::Entry> class_entries, identifier_entries;
     switch (state) {
     case Free:
@@ -110,7 +112,9 @@ void GMLAutocompleteProvider::provide_completions(Function<void(Vector<Entry>)>
             // Nothing to put here.
             break;
         }
-        GUI::WidgetClassRegistration::for_each([&](const GUI::WidgetClassRegistration& registration) {
+        Core::ObjectClassRegistration::for_each([&](const Core::ObjectClassRegistration& registration) {
+            if (!registration.is_derived_from(widget_class))
+                return;
             class_entries.empend(String::formatted("@{}", registration.class_name()), 0u);
         });
         break;
@@ -122,12 +126,14 @@ void GMLAutocompleteProvider::provide_completions(Function<void(Vector<Entry>)>
             // TODO: Suggest braces?
             break;
         }
-        GUI::WidgetClassRegistration::for_each([&](const GUI::WidgetClassRegistration& registration) {
+        Core::ObjectClassRegistration::for_each([&](const Core::ObjectClassRegistration& registration) {
+            if (!registration.is_derived_from(widget_class))
+                return;
             if (registration.class_name().starts_with(class_names.last()))
                 identifier_entries.empend(registration.class_name(), class_names.last().length());
         });
         break;
-    case InIdentifier:
+    case InIdentifier: {
         if (class_names.is_empty())
             break;
         if (last_seen_token && last_seen_token->m_end.column + 1 != cursor.column() && last_seen_token->m_end.line == cursor.line()) {
@@ -135,7 +141,8 @@ void GMLAutocompleteProvider::provide_completions(Function<void(Vector<Entry>)>
             // TODO: Maybe suggest a colon?
             break;
         }
-        if (auto registration = GUI::WidgetClassRegistration::find(class_names.last())) {
+        auto registration = Core::ObjectClassRegistration::find(class_names.last());
+        if (registration && registration->is_derived_from(widget_class)) {
             auto instance = registration->construct();
             for (auto& it : instance->properties()) {
                 if (it.key.starts_with(identifier_string))
@@ -148,7 +155,8 @@ void GMLAutocompleteProvider::provide_completions(Function<void(Vector<Entry>)>
         if (identifier_entries.size() == 1 && identifier_entries.first().completion == identifier_string)
             identifier_entries.clear();
         break;
-    case AfterClassName:
+    }
+    case AfterClassName: {
         if (last_seen_token && last_seen_token->m_end.line == cursor.line()) {
             if (last_seen_token->m_type != GUI::GMLToken::Type::Identifier || last_seen_token->m_end.column + 1 != cursor.column()) {
                 // Inside braces, but on the same line as some other stuff (and not the continuation of one!)
@@ -157,7 +165,8 @@ void GMLAutocompleteProvider::provide_completions(Function<void(Vector<Entry>)>
             }
         }
         if (!class_names.is_empty()) {
-            if (auto registration = GUI::WidgetClassRegistration::find(class_names.last())) {
+            auto registration = Core::ObjectClassRegistration::find(class_names.last());
+            if (registration && registration->is_derived_from(widget_class)) {
                 auto instance = registration->construct();
                 for (auto& it : instance->properties()) {
                     if (!it.value->is_readonly())
@@ -165,16 +174,21 @@ void GMLAutocompleteProvider::provide_completions(Function<void(Vector<Entry>)>
                 }
             }
         }
-        GUI::WidgetClassRegistration::for_each([&](const GUI::WidgetClassRegistration& registration) {
+        Core::ObjectClassRegistration::for_each([&](const Core::ObjectClassRegistration& registration) {
+            if (!registration.is_derived_from(widget_class))
+                return;
             class_entries.empend(String::formatted("@{}", registration.class_name()), 0u);
         });
         break;
+    }
     case AfterIdentifier:
         if (last_seen_token && last_seen_token->m_end.line != cursor.line()) {
             break;
         }
         if (identifier_string == "layout") {
-            GUI::WidgetClassRegistration::for_each([&](const GUI::WidgetClassRegistration& registration) {
+            Core::ObjectClassRegistration::for_each([&](const Core::ObjectClassRegistration& registration) {
+                if (!registration.is_derived_from(widget_class))
+                    return;
                 if (registration.class_name().contains("Layout"))
                     class_entries.empend(String::formatted("@{}", registration.class_name()), 0u);
             });
diff --git a/Userland/DevTools/Playground/main.cpp b/Userland/DevTools/Playground/main.cpp
index fcd2f15d2c..eb95cddab9 100644
--- a/Userland/DevTools/Playground/main.cpp
+++ b/Userland/DevTools/Playground/main.cpp
@@ -128,7 +128,7 @@ int main(int argc, char** argv)
 
     editor.on_change = [&] {
         preview.remove_all_children();
-        preview.load_from_gml(editor.text(), [](const String& class_name) -> RefPtr<GUI::Widget> {
+        preview.load_from_gml(editor.text(), [](const String& class_name) -> RefPtr<Core::Object> {
             return UnregisteredWidget::construct(class_name);
         });
     };
diff --git a/Userland/Libraries/LibCore/Forward.h b/Userland/Libraries/LibCore/Forward.h
index ece3631f99..5bd7941640 100644
--- a/Userland/Libraries/LibCore/Forward.h
+++ b/Userland/Libraries/LibCore/Forward.h
@@ -27,6 +27,7 @@ class NetworkJob;
 class NetworkResponse;
 class Notifier;
 class Object;
+class ObjectClassRegistration;
 class ProcessStatisticsReader;
 class Socket;
 class SocketAddress;
diff --git a/Userland/Libraries/LibCore/Object.cpp b/Userland/Libraries/LibCore/Object.cpp
index fffeeb955f..4c316406fd 100644
--- a/Userland/Libraries/LibCore/Object.cpp
+++ b/Userland/Libraries/LibCore/Object.cpp
@@ -250,4 +250,44 @@ void Object::set_event_filter(Function<bool(Core::Event&)> filter)
     m_event_filter = move(filter);
 }
 
+static HashMap<String, ObjectClassRegistration*>& object_classes()
+{
+    static HashMap<String, ObjectClassRegistration*>* map;
+    if (!map)
+        map = new HashMap<String, ObjectClassRegistration*>;
+    return *map;
+}
+
+ObjectClassRegistration::ObjectClassRegistration(const String& class_name, Function<NonnullRefPtr<Object>()> factory, ObjectClassRegistration* parent_class)
+    : m_class_name(class_name)
+    , m_factory(move(factory))
+    , m_parent_class(parent_class)
+{
+    object_classes().set(class_name, this);
+}
+
+ObjectClassRegistration::~ObjectClassRegistration()
+{
+}
+
+bool ObjectClassRegistration::is_derived_from(const ObjectClassRegistration& base_class) const
+{
+    if (&base_class == this)
+        return true;
+    if (!m_parent_class)
+        return false;
+    return m_parent_class->is_derived_from(base_class);
+}
+
+void ObjectClassRegistration::for_each(Function<void(const ObjectClassRegistration&)> callback)
+{
+    for (auto& it : object_classes()) {
+        callback(*it.value);
+    }
+}
+
+const ObjectClassRegistration* ObjectClassRegistration::find(const String& class_name)
+{
+    return object_classes().get(class_name).value_or(nullptr);
+}
 }
diff --git a/Userland/Libraries/LibCore/Object.h b/Userland/Libraries/LibCore/Object.h
index c171c395f7..046a1b894f 100644
--- a/Userland/Libraries/LibCore/Object.h
+++ b/Userland/Libraries/LibCore/Object.h
@@ -19,6 +19,35 @@
 
 namespace Core {
 
+#define REGISTER_CORE_OBJECT(namespace_, class_name)                                                                                             \
+    namespace Core {                                                                                                                             \
+    namespace Registration {                                                                                                                     \
+    Core::ObjectClassRegistration registration_##class_name(#namespace_ "::" #class_name, []() { return namespace_::class_name::construct(); }); \
+    }                                                                                                                                            \
+    }
+
+class ObjectClassRegistration {
+    AK_MAKE_NONCOPYABLE(ObjectClassRegistration);
+    AK_MAKE_NONMOVABLE(ObjectClassRegistration);
+
+public:
+    ObjectClassRegistration(const String& class_name, Function<NonnullRefPtr<Object>()> factory, ObjectClassRegistration* parent_class = nullptr);
+    ~ObjectClassRegistration();
+
+    String class_name() const { return m_class_name; }
+    const ObjectClassRegistration* parent_class() const { return m_parent_class; }
+    NonnullRefPtr<Object> construct() const { return m_factory(); }
+    bool is_derived_from(const ObjectClassRegistration& base_class) const;
+
+    static void for_each(Function<void(const ObjectClassRegistration&)>);
+    static const ObjectClassRegistration* find(const String& class_name);
+
+private:
+    String m_class_name;
+    Function<NonnullRefPtr<Object>()> m_factory;
+    ObjectClassRegistration* m_parent_class { nullptr };
+};
+
 class RPCClient;
 
 enum class TimerShouldFireWhenNotVisible {
@@ -129,6 +158,8 @@ public:
     void increment_inspector_count(Badge<RPCClient>);
     void decrement_inspector_count(Badge<RPCClient>);
 
+    virtual bool load_from_json(const JsonObject&, RefPtr<Core::Object> (*)(const String&)) { return false; }
+
 protected:
     explicit Object(Object* parent = nullptr);
 
diff --git a/Userland/Libraries/LibGUI/BoxLayout.cpp b/Userland/Libraries/LibGUI/BoxLayout.cpp
index 113e4016a6..8ec88fe4d3 100644
--- a/Userland/Libraries/LibGUI/BoxLayout.cpp
+++ b/Userland/Libraries/LibGUI/BoxLayout.cpp
@@ -10,8 +10,8 @@
 #include <LibGfx/Orientation.h>
 #include <stdio.h>
 
-REGISTER_WIDGET(GUI, HorizontalBoxLayout)
-REGISTER_WIDGET(GUI, VerticalBoxLayout)
+REGISTER_CORE_OBJECT(GUI, HorizontalBoxLayout)
+REGISTER_CORE_OBJECT(GUI, VerticalBoxLayout)
 
 namespace GUI {
 
diff --git a/Userland/Libraries/LibGUI/Forward.h b/Userland/Libraries/LibGUI/Forward.h
index 83c97aaaad..00e5e7725b 100644
--- a/Userland/Libraries/LibGUI/Forward.h
+++ b/Userland/Libraries/LibGUI/Forward.h
@@ -78,7 +78,6 @@ class VerticalBoxLayout;
 class VerticalSlider;
 class WMEvent;
 class Widget;
-class WidgetClassRegistration;
 class Window;
 class WindowServerConnection;
 
diff --git a/Userland/Libraries/LibGUI/Widget.cpp b/Userland/Libraries/LibGUI/Widget.cpp
index 34b2fac31a..8e9da86a51 100644
--- a/Userland/Libraries/LibGUI/Widget.cpp
+++ b/Userland/Libraries/LibGUI/Widget.cpp
@@ -23,41 +23,10 @@
 #include <LibGfx/Palette.h>
 #include <unistd.h>
 
-REGISTER_WIDGET(GUI, Widget)
+REGISTER_CORE_OBJECT(GUI, Widget)
 
 namespace GUI {
 
-static HashMap<String, WidgetClassRegistration*>& widget_classes()
-{
-    static HashMap<String, WidgetClassRegistration*>* map;
-    if (!map)
-        map = new HashMap<String, WidgetClassRegistration*>;
-    return *map;
-}
-
-WidgetClassRegistration::WidgetClassRegistration(const String& class_name, Function<NonnullRefPtr<Widget>()> factory)
-    : m_class_name(class_name)
-    , m_factory(move(factory))
-{
-    widget_classes().set(class_name, this);
-}
-
-WidgetClassRegistration::~WidgetClassRegistration()
-{
-}
-
-void WidgetClassRegistration::for_each(Function<void(const WidgetClassRegistration&)> callback)
-{
-    for (auto& it : widget_classes()) {
-        callback(*it.value);
-    }
-}
-
-const WidgetClassRegistration* WidgetClassRegistration::find(const String& class_name)
-{
-    return widget_classes().get(class_name).value_or(nullptr);
-}
-
 Widget::Widget()
     : Core::Object(nullptr)
     , m_background_role(Gfx::ColorRole::Window)
@@ -996,13 +965,13 @@ void Widget::set_override_cursor(Gfx::StandardCursor cursor)
 
 bool Widget::load_from_gml(const StringView& gml_string)
 {
-    return load_from_gml(gml_string, [](const String& class_name) -> RefPtr<Widget> {
+    return load_from_gml(gml_string, [](const String& class_name) -> RefPtr<Core::Object> {
         dbgln("Class '{}' not registered", class_name);
         return nullptr;
     });
 }
 
-bool Widget::load_from_gml(const StringView& gml_string, RefPtr<Widget> (*unregistered_child_handler)(const String&))
+bool Widget::load_from_gml(const StringView& gml_string, RefPtr<Core::Object> (*unregistered_child_handler)(const String&))
 {
     auto value = parse_gml(gml_string);
     if (!value.is_object())
@@ -1010,7 +979,7 @@ bool Widget::load_from_gml(const StringView& gml_string, RefPtr<Widget> (*unregi
     return load_from_json(value.as_object(), unregistered_child_handler);
 }
 
-bool Widget::load_from_json(const JsonObject& json, RefPtr<Widget> (*unregistered_child_handler)(const String&))
+bool Widget::load_from_json(const JsonObject& json, RefPtr<Core::Object> (*unregistered_child_handler)(const String&))
 {
     json.for_each_member([&](auto& key, auto& value) {
         set_property(key, value);
@@ -1055,16 +1024,16 @@ bool Widget::load_from_json(const JsonObject& json, RefPtr<Widget> (*unregistere
                 return false;
             }
 
-            RefPtr<Widget> child_widget;
-            if (auto* registration = WidgetClassRegistration::find(class_name.as_string())) {
-                child_widget = registration->construct();
+            RefPtr<Core::Object> child;
+            if (auto* registration = Core::ObjectClassRegistration::find(class_name.as_string())) {
+                child = registration->construct();
             } else {
-                child_widget = unregistered_child_handler(class_name.as_string());
-                if (!child_widget)
-                    return false;
+                child = unregistered_child_handler(class_name.as_string());
             }
-            add_child(*child_widget);
-            child_widget->load_from_json(child_json, unregistered_child_handler);
+            if (!child)
+                return false;
+            add_child(*child);
+            child->load_from_json(child_json, unregistered_child_handler);
         }
     }
 
diff --git a/Userland/Libraries/LibGUI/Widget.h b/Userland/Libraries/LibGUI/Widget.h
index b90649af33..2ec342cc53 100644
--- a/Userland/Libraries/LibGUI/Widget.h
+++ b/Userland/Libraries/LibGUI/Widget.h
@@ -19,9 +19,18 @@
 #include <LibGfx/Rect.h>
 #include <LibGfx/StandardCursor.h>
 
-#define REGISTER_WIDGET(namespace_, class_name)                                                                                                 \
-    namespace {                                                                                                                                 \
-    GUI::WidgetClassRegistration registration_##class_name(#namespace_ "::" #class_name, []() { return namespace_::class_name::construct(); }); \
+namespace Core {
+namespace Registration {
+extern Core::ObjectClassRegistration registration_Widget;
+}
+}
+
+#define REGISTER_WIDGET(namespace_, class_name)                                                                                                   \
+    namespace Core {                                                                                                                              \
+    namespace Registration {                                                                                                                      \
+    Core::ObjectClassRegistration registration_##class_name(                                                                                      \
+        #namespace_ "::" #class_name, []() { return static_ptr_cast<Core::Object>(namespace_::class_name::construct()); }, &registration_Widget); \
+    }                                                                                                                                             \
     }
 
 namespace GUI {
@@ -35,25 +44,6 @@ enum class VerticalDirection {
     Down
 };
 
-class WidgetClassRegistration {
-    AK_MAKE_NONCOPYABLE(WidgetClassRegistration);
-    AK_MAKE_NONMOVABLE(WidgetClassRegistration);
-
-public:
-    WidgetClassRegistration(const String& class_name, Function<NonnullRefPtr<Widget>()> factory);
-    ~WidgetClassRegistration();
-
-    String class_name() const { return m_class_name; }
-    NonnullRefPtr<Widget> construct() const { return m_factory(); }
-
-    static void for_each(Function<void(const WidgetClassRegistration&)>);
-    static const WidgetClassRegistration* find(const String& class_name);
-
-private:
-    String m_class_name;
-    Function<NonnullRefPtr<Widget>()> m_factory;
-};
-
 enum class FocusPolicy {
     NoFocus = 0,
     TabFocus = 0x1,
@@ -281,7 +271,7 @@ public:
     void set_override_cursor(Gfx::StandardCursor);
 
     bool load_from_gml(const StringView&);
-    bool load_from_gml(const StringView&, RefPtr<Widget> (*unregistered_child_handler)(const String&));
+    bool load_from_gml(const StringView&, RefPtr<Core::Object> (*unregistered_child_handler)(const String&));
 
     void set_shrink_to_fit(bool);
     bool is_shrink_to_fit() const { return m_shrink_to_fit; }
@@ -341,7 +331,7 @@ private:
     void focus_previous_widget(FocusSource, bool siblings_only);
     void focus_next_widget(FocusSource, bool siblings_only);
 
-    bool load_from_json(const JsonObject&, RefPtr<Widget> (*unregistered_child_handler)(const String&));
+    virtual bool load_from_json(const JsonObject&, RefPtr<Core::Object> (*unregistered_child_handler)(const String&)) override;
 
     // HACK: These are used as property getters for the fixed_* size property aliases.
     int dummy_fixed_width() { return 0; }