Associations implementation (#13)

Author: zaucy

.vscode/launch.json

@@ -2,7 +2,7 @@
 	"version": "0.2.0",
 	"configurations": [
 		{
-			"name": "test //test:test",
+			"name": "test //runtime/test:test",
 			"request": "launch",
 			"program": "${workspaceFolder}/bazel-bin/runtime/test/test",
 			"cwd": "${workspaceFolder}",

README.md

@@ -1,3 +1,57 @@
 # EnTT Ecsact Runtime Implementation
 
 [Ecsact](https://ecsact.dev) runtime built with [EnTT](https://github.com/skypjack/entt).
+
+## System Views
+
+In the simpliest cases an Ecsact system lines up 1:1 with an EnTT view.
+
+```ecsact
+package example;
+component Health { f32 value; }
+component Invincible;
+system Gravity { readwrite Position; exclude Weightless; }
+```
+
+```cpp
+entt::basic_view<entt::entity, entt::get_t<example::Health>, entt::exclude_t<example::Invincible>>
+```
+
+Since `adds` implies `exclude` and `removes` implies `include` even `adds`/`removes` systems are _almost_ 1:1.
+
+```ecsact
+package example;
+component Health { f32 value; }
+component Healing;
+action StartHealing { include Health; adds Healing; }
+action StopHealing { include Health; removes Healing; }
+```
+
+```cpp
+// EnTT view for StartHealing
+entt::basic_view<entt::entity, entt::get_t<example::Health>, entt::exclude_t<example::Healing>>
+// EnTT view for StopHealing
+entt::basic_view<entt::entity, entt::get_t<example::Health, example::Healing>, entt::exclude_t<>>
+```
+
+As soon as system association occurs there now requires multiple views to be iterated at the same time.
+
+```ecsact
+package example;
+component Health { f32 value; }
+component Attacking { entity target; }
+action Attack {
+  entity target;
+  adds Attacking;
+}
+system AttackDamage {
+  readonly Attacking with target {
+    readwrite Health;
+  }
+}
+```
+
+```cpp
+entt::basic_view<entt::entity, entt:get_t<example::Attacking>, entt::exclude_t<>>
+entt::basic_view<entt::entity, entt:get_t<example::Health, ecsact::entt::association<example::Attacking, 0/*target*/>>, entt::exclude_t<>>
+```

ecsact/entt/detail/internal_markers.hh

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <cstdint>
+#include <type_traits>
+
+namespace ecsact::entt::detail {
+	template<typename C, std::size_t FieldOffset>
+	struct association {
+		using component = C;
+		static constexpr auto field_offset = FieldOffset;
+	};
+
+	template<typename C>
+	struct temp_storage;
+
+	template<typename C> requires(std::is_empty_v<C>)
+	struct temp_storage<C> { };
+
+	template<typename C> requires(!std::is_empty_v<C>)
+	struct temp_storage<C> { C value; };
+
+	template<typename C> requires(!std::is_empty_v<C>)
+	struct beforechange_storage { C value; bool set = false; };
+
+	template<typename C>
+	struct pending_add;
+
+	template<typename C> requires(std::is_empty_v<C>)
+	struct pending_add<C> { };
+
+	template<typename C> requires(!std::is_empty_v<C>)
+	struct pending_add<C> { C value; };
+
+	template<typename C>
+	struct pending_remove {};
+}

ecsact/entt/detail/registry_info.hh

@@ -10,6 +10,7 @@
 #include "ecsact/runtime/core.h"
 
 #include "ecsact/entt/event_markers.hh"
+#include "ecsact/entt/detail/internal_markers.hh"
 
 namespace ecsact_entt_rt {
 	using entity_id_map_t = std::unordered_map
@@ -57,6 +58,38 @@ namespace ecsact_entt_rt {
 			});
 		}
 
+		template<typename C>
+		void _add_association
+			( const C&                   component
+			, const ecsact::field_info&  field
+			)
+		{
+			using ecsact::entt::detail::association;
+			using boost::mp11::mp_with_index;
+
+			auto entity_field = field.template get<ecsact_entity_id>(component);
+			auto entity_field_entt = entities_map.at(entity_field);
+			mp_with_index<64>(field.offset, [&](auto I) {
+				registry.emplace<association<C, I>>(entity_field_entt);
+			});
+		}
+
+		template<typename C>
+		void _remove_association
+			( const C&                   component
+			, const ecsact::field_info&  field
+			)
+		{
+			using ecsact::entt::detail::association;
+			using boost::mp11::mp_with_index;
+
+			auto entity_field = field.template get<ecsact_entity_id>(component);
+			auto entity_field_entt = entities_map.at(entity_field);
+			mp_with_index<64>(field.offset, [&](auto I) {
+				registry.erase<association<C, I>>(entity_field_entt);
+			});
+		}
+
 		template<typename C> requires(std::is_empty_v<C>)
 		void add_component
 			( ::entt::entity entity
@@ -72,8 +105,9 @@ namespace ecsact_entt_rt {
 			)
 		{
 			using boost::mp11::mp_for_each;
+			using boost::mp11::mp_with_index;
 
-			registry.emplace<C>(entity, std::forward<Args>(args)...);
+			auto& comp = registry.emplace<C>(entity, std::forward<Args>(args)...);
 
 			mp_for_each<typename package::components>([&]<typename O>(O) {
 				if constexpr(std::is_same_v<std::remove_cvref_t<C>, O>) {
@@ -88,6 +122,15 @@ namespace ecsact_entt_rt {
 					);
 				}
 			});
+
+			constexpr auto fields_info = ecsact::fields_info<C>();
+			if constexpr(!fields_info.empty()) {
+				for(auto& field : fields_info) {
+					if(field.storage_type == ECSACT_ENTITY_TYPE) {
+						_add_association(comp, field);
+					}
+				}
+			}
 		}
 
 		template<typename C>
@@ -97,6 +140,16 @@ namespace ecsact_entt_rt {
 		{
 			using boost::mp11::mp_for_each;
 
+			constexpr auto fields_info = ecsact::fields_info<C>();
+			if constexpr(!fields_info.empty()) {
+				auto& comp = registry.get<C>(entity);
+				for(auto& field : fields_info) {
+					if(field.storage_type == ECSACT_ENTITY_TYPE) {
+						_remove_association(comp, field);
+					}
+				}
+			}
+
 			registry.erase<C>(entity);
 
 			if constexpr(!std::is_empty_v<C>) {