Add helper macros for defining ecs components and their to_string() methods

libs/ecs/include/psemek/ecs/define_component.hpp

@@ -0,0 +1,98 @@
+#pragma once
+
+#include <psemek/ecs/declare_uuid.hpp>
+
+#include <boost/preprocessor/tuple/elem.hpp>
+#include <boost/preprocessor/tuple/size.hpp>
+#include <boost/preprocessor/cat.hpp>
+#include <boost/preprocessor/stringize.hpp>
+#include <boost/preprocessor/seq/for_each.hpp>
+#include <boost/preprocessor/seq/variadic_seq_to_seq.hpp>
+
+#include <format>
+
+namespace psemek::ecs::detail
+{
+
+	template <typename T>
+	struct define_component_type_helper;
+
+	template <typename T>
+	struct define_component_type_helper<void(T)>
+	{
+		using type = T;
+	};
+
+}
+
+#define psemek_ecs_define_component_detail_field_impl_2(value) \
+	typename ::psemek::ecs::detail::define_component_type_helper<void(BOOST_PP_TUPLE_ELEM(1, value))>::type BOOST_PP_TUPLE_ELEM(0, value);
+
+#define psemek_ecs_define_component_detail_field_impl_3(value) \
+	typename ::psemek::ecs::detail::define_component_type_helper<void(BOOST_PP_TUPLE_ELEM(1, value))>::type BOOST_PP_TUPLE_ELEM(0, value) = BOOST_PP_TUPLE_ELEM(2, value);
+
+#define psemek_ecs_define_component_detail_field_impl(value, size) \
+	BOOST_PP_CAT(psemek_ecs_define_component_detail_field_impl_, size)(value)
+
+#define psemek_ecs_define_component_detail_field(r, data, value) \
+	psemek_ecs_define_component_detail_field_impl(value, BOOST_PP_TUPLE_SIZE(value))
+
+#define psemek_ecs_define_component_detail_to_string_impl(fname) \
+	result += std::format(BOOST_PP_STRINGIZE(fname) ": {}\n", fname);
+
+#define psemek_ecs_define_component_detail_to_string(r, data, value) \
+	psemek_ecs_define_component_detail_to_string_impl(BOOST_PP_TUPLE_ELEM(0, value))
+
+#define psemek_ecs_define_component_fields_impl(fields) \
+		BOOST_PP_SEQ_FOR_EACH(psemek_ecs_define_component_detail_field, _, fields) \
+		std::string to_string() const { \
+			std::string result; \
+			BOOST_PP_SEQ_FOR_EACH(psemek_ecs_define_component_detail_to_string, _, fields) \
+			return result; \
+		}
+
+/* Given a sequence of pairs or triples of the form
+ *
+ *     (name, type)
+ *     (name, type, default_value)
+ *
+ * emit a field with the specified type, name, and default_value (if present),
+ * and generate a to_string() const method that outputs each field on its own line
+ * using std::format.
+ *
+ * For example,
+ *
+ *     psemek_ecs_define_component_fields(
+ *         (position, float)
+ *         (count, int, 0)
+ *     )
+ *
+ * emits
+ *
+ *     float position;
+ *     int count = 0;
+ *
+ * and the corresponding to_string() implementation.
+ *
+ * If the type contains commas (e.g. if it is a template specialization with several
+ * parameters, like math::vector<float, 2>), the whole type must be put in parentheses, like
+ *
+ *     psemek_ecs_define_component_fields(
+ *         (position, (math::vector<float, 2>))
+ *     )
+ *
+ * If the default value contains commas, the same applies. If the default value is an initializer
+ * list, it (quite regrettably) must be converted to an explicit value within parentheses, e.g.
+ *
+ *     psemek_ecs_define_component_fields(
+ *         (position, (math::vector<float, 2>), (math::vector{100.f, 100.f}))
+ *     )
+ */
+#define psemek_ecs_define_component_fields(fields) \
+	psemek_ecs_define_component_fields_impl(BOOST_PP_VARIADIC_SEQ_TO_SEQ(fields))
+
+#define psemek_ecs_define_component(cname, fields) \
+	struct cname { \
+		psemek_ecs_define_component_fields_impl(BOOST_PP_VARIADIC_SEQ_TO_SEQ(fields)) \
+		psemek_ecs_declare_uuid(BOOST_PP_STRINGIZE(cname)) \
+	};

libs/ecs/include/psemek/ecs/to_string.hpp

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <boost/preprocessor/control/if.hpp>
+#include <boost/preprocessor/seq/for_each_i.hpp>
+#include <boost/preprocessor/variadic/to_seq.hpp>
+#include <boost/preprocessor/stringize.hpp>
+
+#include <format>
+
+#define psemek_ecs_to_string_detail_apply_one(r, data, i, elem) \
+    BOOST_PP_IF(i, "\n", "") BOOST_PP_STRINGIZE(elem) ": {}"
+
+/* Format a sequence of values into lines of the form "name: value".
+ * For example, having
+ *
+ *     int a = 10;
+ *     float x = 3.5f;
+ *
+ * The call
+ *
+ *     psemek_ecs_to_string(a, b)
+ *
+ * returns a string
+ *
+ *     "a = 10\nx = 3.5\n"
+ */
+#define psemek_ecs_to_string(...) \
+    std::format( \
+        BOOST_PP_SEQ_FOR_EACH_I( \
+            psemek_ecs_to_string_detail_apply_one, _, BOOST_PP_VARIADIC_TO_SEQ(__VA_ARGS__) \
+        ), \
+        __VA_ARGS__ \
+    )
+
+#define psemek_ecs_declare_to_string(...) \
+	std::string to_string() const { return psemek_ecs_to_string(__VA_ARGS__); }