finalise interface & documentation

Signed-off-by: Folling <mail@folling.io>

include/ikarus/folders/entity_tree_item.h

@@ -0,0 +1,31 @@
+#pragma once
+
+/// \file entity_tree_item.h
+/// \author Folling <folling@ikarus.world>
+
+#include <ikarus/macros.h>
+
+/// \addtogroup entities Entities
+/// @{
+
+IKARUS_BEGIN_HEADER
+
+struct IkarusEntityTreeItem;
+
+/// \brief Visits a entity tree item, calling the appropriate visitor function.
+/// \param item The item to visit.
+/// \pre \li Must not be null.
+/// \pre \li Must exist.
+/// \param entity_visitor The visitor function called if the item is a entity. Skipped if null.
+/// \param entity_folder_visitor The visitor function called if the item is a entity folder. Skipped if null.
+/// \param data The data passed to the visitor functions.
+IKA_API void ikarus_entity_tree_item_visit(
+    struct IkarusEntityTreeItem * item,
+    void (*entity_visitor)(struct IkarusEntity * entity, void * data),
+    void (*entity_folder_visitor)(struct IkarusEntityFolder * folder, void * data),
+    void * data
+);
+
+IKARUS_END_HEADER
+
+/// @}