Squashed 'external/entt/entt/' content from commit fef92113

git-subtree-dir: external/entt/entt
git-subtree-split: fef921132cae7588213d0f9bcd2fb9c8ffd8b7fc

test/lib/registry/lib.cpp

@@ -0,0 +1,19 @@
+#include <entt/core/attribute.h>
+#include <entt/entity/registry.hpp>
+#include "types.h"
+
+ENTT_API void update_position(entt::registry &registry) {
+    registry.view<position, velocity>().each([](auto &pos, auto &vel) {
+        pos.x += static_cast<int>(16 * vel.dx);
+        pos.y += static_cast<int>(16 * vel.dy);
+    });
+}
+
+ENTT_API void emplace_velocity(entt::registry &registry) {
+    // forces the creation of the pool for the velocity component
+    static_cast<void>(registry.storage<velocity>());
+
+    for(auto entity: registry.view<position>()) {
+        registry.emplace<velocity>(entity, 1., 1.);
+    }
+}

test/lib/registry/main.cpp

@@ -0,0 +1,27 @@
+#include <gtest/gtest.h>
+#include <entt/core/attribute.h>
+#include <entt/entity/entity.hpp>
+#include <entt/entity/registry.hpp>
+#include "types.h"
+
+ENTT_API void update_position(entt::registry &);
+ENTT_API void emplace_velocity(entt::registry &);
+
+TEST(Lib, Registry) {
+    entt::registry registry;
+
+    for(auto i = 0; i < 3; ++i) {
+        const auto entity = registry.create();
+        registry.emplace<position>(entity, i, i);
+    }
+
+    emplace_velocity(registry);
+    update_position(registry);
+
+    ASSERT_EQ(registry.storage<position>().size(), registry.storage<velocity>().size());
+
+    registry.view<position>().each([](auto entity, auto &position) {
+        ASSERT_EQ(position.x, static_cast<int>(entt::to_integral(entity) + 16));
+        ASSERT_EQ(position.y, static_cast<int>(entt::to_integral(entity) + 16));
+    });
+}

test/lib/registry/types.h

@@ -0,0 +1,16 @@
+#ifndef ENTT_LIB_REGISTRY_TYPES_H
+#define ENTT_LIB_REGISTRY_TYPES_H
+
+#include <entt/core/attribute.h>
+
+struct ENTT_API position {
+    int x;
+    int y;
+};
+
+struct ENTT_API velocity {
+    double dx;
+    double dy;
+};
+
+#endif