Improve logic around using Ref<T> with GDExtension virtual functions

core/extension/gdextension_interface.cpp

@@ -879,6 +879,23 @@ static GDObjectInstanceID gdextension_object_get_instance_id(GDExtensionConstObj
 	return (GDObjectInstanceID)o->get_instance_id();
 }
 
+static GDExtensionObjectPtr gdextension_ref_get_object(GDExtensionConstRefPtr p_ref) {
+	const Ref<RefCounted> *ref = (const Ref<RefCounted> *)p_ref;
+	if (ref == nullptr || ref->is_null()) {
+		return (GDExtensionObjectPtr) nullptr;
+	} else {
+		return (GDExtensionObjectPtr)ref->ptr();
+	}
+}
+
+static void gdextension_ref_set_object(GDExtensionRefPtr p_ref, GDExtensionObjectPtr p_object) {
+	Ref<RefCounted> *ref = (Ref<RefCounted> *)p_ref;
+	ERR_FAIL_NULL(ref);
+
+	Object *o = (RefCounted *)p_object;
+	ref->reference_ptr(o);
+}
+
 static GDExtensionScriptInstancePtr gdextension_script_instance_create(const GDExtensionScriptInstanceInfo *p_info, GDExtensionScriptInstanceDataPtr p_instance_data) {
 	ScriptInstanceExtension *script_instance_extension = memnew(ScriptInstanceExtension);
 	script_instance_extension->instance = p_instance_data;
@@ -1057,6 +1074,11 @@ void gdextension_setup_interface(GDExtensionInterface *p_interface) {
 	gde_interface.object_get_instance_from_id = gdextension_object_get_instance_from_id;
 	gde_interface.object_get_instance_id = gdextension_object_get_instance_id;
 
+	/* REFERENCE */
+
+	gde_interface.ref_get_object = gdextension_ref_get_object;
+	gde_interface.ref_set_object = gdextension_ref_set_object;
+
 	/* SCRIPT INSTANCE */
 
 	gde_interface.script_instance_create = gdextension_script_instance_create;

core/extension/gdextension_interface.h

@@ -154,6 +154,8 @@ typedef const void *GDExtensionMethodBindPtr;
 typedef int64_t GDExtensionInt;
 typedef uint8_t GDExtensionBool;
 typedef uint64_t GDObjectInstanceID;
+typedef void *GDExtensionRefPtr;
+typedef const void *GDExtensionConstRefPtr;
 
 /* VARIANT DATA I/O */
 
@@ -551,6 +553,11 @@ typedef struct {
 	GDExtensionObjectPtr (*object_get_instance_from_id)(GDObjectInstanceID p_instance_id);
 	GDObjectInstanceID (*object_get_instance_id)(GDExtensionConstObjectPtr p_object);
 
+	/* REFERENCE */
+
+	GDExtensionObjectPtr (*ref_get_object)(GDExtensionConstRefPtr p_ref);
+	void (*ref_set_object)(GDExtensionRefPtr p_ref, GDExtensionObjectPtr p_object);
+
 	/* SCRIPT INSTANCE */
 
 	GDExtensionScriptInstancePtr (*script_instance_create)(const GDExtensionScriptInstanceInfo *p_info, GDExtensionScriptInstanceDataPtr p_instance_data);

core/object/ref_counted.h

@@ -253,12 +253,14 @@ public:
 template <class T>
 struct PtrToArg<Ref<T>> {
 	_FORCE_INLINE_ static Ref<T> convert(const void *p_ptr) {
+		// p_ptr points to a RefCounted object
 		return Ref<T>(const_cast<T *>(reinterpret_cast<const T *>(p_ptr)));
 	}
 
 	typedef Ref<T> EncodeT;
 
 	_FORCE_INLINE_ static void encode(Ref<T> p_val, const void *p_ptr) {
+		// p_ptr points to an EncodeT object which is a Ref<T> object.
 		*(const_cast<Ref<RefCounted> *>(reinterpret_cast<const Ref<RefCounted> *>(p_ptr))) = p_val;
 	}
 };
@@ -268,6 +270,7 @@ struct PtrToArg<const Ref<T> &> {
 	typedef Ref<T> EncodeT;
 
 	_FORCE_INLINE_ static Ref<T> convert(const void *p_ptr) {
+		// p_ptr points to a RefCounted object
 		return Ref<T>((T *)p_ptr);
 	}
 };