feat(build): Implement scons building

feat(engine): Integrate basic Godot project
feat(test): Demonstrate Godot using extension
feat(dependency): Add OV2-compiler as deps submodule
feat(dependency): Add godot-cpp as a submodule
feat(git): Ignore Godot 4 files
feat(docs): Updated readme with instructions
feat: Can call `TestSingleton.hello_singleton()` from GDScript

Adds basic workflow support but that is currently disabled

5 files changed, 117 insertions, 0 deletions

diff --git a/extension/deps/OV2-compiler b/extension/deps/OV2-compiler
new file mode 160000
+Subproject 267d38aab922fa929c0ce649fad699a6468b6c3
diff --git a/extension/src/TestSingleton.cpp b/extension/src/TestSingleton.cpp
new file mode 100644
index 0000000..0855a30
--- /dev/null
+++ b/extension/src/TestSingleton.cpp
@@ -0,0 +1,36 @@
+#include "TestSingleton.hpp"
+
+#include <godot_cpp/core/class_db.hpp>
+#include <godot_cpp/variant/utility_functions.hpp>
+
+using namespace godot;
+using namespace OpenVic2;
+
+TestSingleton *TestSingleton::singleton = nullptr;
+
+void TestSingleton::_bind_methods()
+{
+	ClassDB::bind_method(D_METHOD("hello_singleton"), &TestSingleton::hello_singleton);
+}
+
+TestSingleton *TestSingleton::get_singleton()
+{
+	return singleton;
+}
+
+TestSingleton::TestSingleton()
+{
+	ERR_FAIL_COND(singleton != nullptr);
+	singleton = this;
+}
+
+TestSingleton::~TestSingleton()
+{
+	ERR_FAIL_COND(singleton != this);
+	singleton = nullptr;
+}
+
+void TestSingleton::hello_singleton()
+{
+	UtilityFunctions::print("Hello GDExtension Singleton!");
+}
\ No newline at end of file
diff --git a/extension/src/TestSingleton.hpp b/extension/src/TestSingleton.hpp
new file mode 100644
index 0000000..0a591ac
--- /dev/null
+++ b/extension/src/TestSingleton.hpp
@@ -0,0 +1,24 @@
+#pragma once
+
+#include <godot_cpp/classes/object.hpp>
+#include <godot_cpp/core/class_db.hpp>
+
+namespace OpenVic2 {
+	class TestSingleton : public godot::Object
+	{
+		GDCLASS(TestSingleton, godot::Object);
+
+		static TestSingleton *singleton;
+
+	protected:
+		static void _bind_methods();
+
+	public:
+		static TestSingleton *get_singleton();
+
+		TestSingleton();
+		~TestSingleton();
+
+		void hello_singleton();
+	};
+}
\ No newline at end of file
diff --git a/extension/src/register_types.cpp b/extension/src/register_types.cpp
new file mode 100644
index 0000000..775e6c3
--- /dev/null
+++ b/extension/src/register_types.cpp
@@ -0,0 +1,51 @@
+#include "register_types.h"
+#include <gdextension_interface.h>
+#include <godot_cpp/core/class_db.hpp>
+#include <godot_cpp/core/defs.hpp>
+#include <godot_cpp/godot.hpp>
+#include <godot_cpp/classes/engine.hpp>
+
+#include "TestSingleton.hpp"
+
+using namespace godot;
+using namespace OpenVic2;
+
+static TestSingleton *_test_singleton;
+
+void initialize_openvic2_types(ModuleInitializationLevel p_level)
+{
+    if (p_level != MODULE_INITIALIZATION_LEVEL_SCENE) {
+        return;
+    }
+
+    ClassDB::register_class<TestSingleton>();
+
+    _test_singleton = memnew(TestSingleton);
+    Engine::get_singleton()->register_singleton("TestSingleton", TestSingleton::get_singleton());
+}
+
+void uninitialize_openvic2_types(ModuleInitializationLevel p_level) {
+    if (p_level != MODULE_INITIALIZATION_LEVEL_SCENE) {
+        return;
+    }
+
+    Engine::get_singleton()->unregister_singleton("TestSingleton");
+    memdelete(_test_singleton);
+}
+
+extern "C"
+{
+
+    // Initialization.
+
+    GDExtensionBool GDE_EXPORT openvic2_library_init(const GDExtensionInterface *p_interface, const GDExtensionClassLibraryPtr p_library, GDExtensionInitialization *r_initialization)
+    {
+        GDExtensionBinding::InitObject init_obj(p_interface, p_library, r_initialization);
+
+        init_obj.register_initializer(initialize_openvic2_types);
+        init_obj.register_terminator(uninitialize_openvic2_types);
+        init_obj.set_minimum_library_initialization_level(MODULE_INITIALIZATION_LEVEL_SCENE);
+
+        return init_obj.init();
+    }
+}
\ No newline at end of file
diff --git a/extension/src/register_types.h b/extension/src/register_types.h
new file mode 100644
index 0000000..860359f
--- /dev/null
+++ b/extension/src/register_types.h
@@ -0,0 +1,6 @@
+#pragma once
+
+#include <godot_cpp/core/class_db.hpp>
+
+void initialize_openvic2_types(godot::ModuleInitializationLevel);
+void uninitialize_openvic2_types(godot::ModuleInitializationLevel);
\ No newline at end of file