add settings reset

libs/include/entt/entity/component.hpp

@@ -0,0 +1,56 @@
+#ifndef ENTT_ENTITY_COMPONENT_HPP
+#define ENTT_ENTITY_COMPONENT_HPP
+
+#include <cstddef>
+#include <type_traits>
+#include "../config/config.h"
+#include "fwd.hpp"
+
+namespace entt {
+
+/*! @cond TURN_OFF_DOXYGEN */
+namespace internal {
+
+template<typename Type, typename = void>
+struct in_place_delete: std::bool_constant<!(std::is_move_constructible_v<Type> && std::is_move_assignable_v<Type>)> {};
+
+template<>
+struct in_place_delete<void>: std::false_type {};
+
+template<typename Type>
+struct in_place_delete<Type, std::enable_if_t<Type::in_place_delete>>
+    : std::true_type {};
+
+template<typename Type, typename = void>
+struct page_size: std::integral_constant<std::size_t, !std::is_empty_v<ENTT_ETO_TYPE(Type)> * ENTT_PACKED_PAGE> {};
+
+template<>
+struct page_size<void>: std::integral_constant<std::size_t, 0u> {};
+
+template<typename Type>
+struct page_size<Type, std::void_t<decltype(Type::page_size)>>
+    : std::integral_constant<std::size_t, Type::page_size> {};
+
+} // namespace internal
+/*! @endcond */
+
+/**
+ * @brief Common way to access various properties of components.
+ * @tparam Type Type of component.
+ */
+template<typename Type, typename = void>
+struct component_traits {
+    static_assert(std::is_same_v<std::decay_t<Type>, Type>, "Unsupported type");
+
+    /*! @brief Component type. */
+    using type = Type;
+
+    /*! @brief Pointer stability, default is `false`. */
+    static constexpr bool in_place_delete = internal::in_place_delete<Type>::value;
+    /*! @brief Page size, default is `ENTT_PACKED_PAGE` for non-empty types. */
+    static constexpr std::size_t page_size = internal::page_size<Type>::value;
+};
+
+} // namespace entt
+
+#endif