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superbuild/modules/entt/src/entt/entity/observer.hpp

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#ifndef ENTT_ENTITY_OBSERVER_HPP
#define ENTT_ENTITY_OBSERVER_HPP
#include <cstddef>
#include <cstdint>
#include <limits>
#include <type_traits>
#include <utility>
#include "../config/config.h"
#include "../core/type_traits.hpp"
#include "../signal/delegate.hpp"
#include "entity.hpp"
#include "fwd.hpp"
#include "registry.hpp"
#include "storage.hpp"
#include "utility.hpp"
namespace entt {
/*! @brief Grouping matcher. */
template<typename...>
struct matcher {};
/**
* @brief Collector.
*
* Primary template isn't defined on purpose. All the specializations give a
* compile-time error, but for a few reasonable cases.
*/
template<typename...>
struct basic_collector;
/**
* @brief Collector.
*
* A collector contains a set of rules (literally, matchers) to use to track
* entities.<br/>
* Its main purpose is to generate a descriptor that allows an observer to know
* how to connect to a registry.
*/
template<>
struct basic_collector<> {
/**
* @brief Adds a grouping matcher to the collector.
* @tparam AllOf Types of components tracked by the matcher.
* @tparam NoneOf Types of components used to filter out entities.
* @return The updated collector.
*/
template<typename... AllOf, typename... NoneOf>
static constexpr auto group(exclude_t<NoneOf...> = {}) ENTT_NOEXCEPT {
return basic_collector<matcher<type_list<>, type_list<>, type_list<NoneOf...>, AllOf...>>{};
}
/**
* @brief Adds an observing matcher to the collector.
* @tparam AnyOf Type of component for which changes should be detected.
* @return The updated collector.
*/
template<typename AnyOf>
static constexpr auto update() ENTT_NOEXCEPT {
return basic_collector<matcher<type_list<>, type_list<>, AnyOf>>{};
}
};
/**
* @brief Collector.
* @copydetails basic_collector<>
* @tparam Reject Untracked types used to filter out entities.
* @tparam Require Untracked types required by the matcher.
* @tparam Rule Specific details of the current matcher.
* @tparam Other Other matchers.
*/
template<typename... Reject, typename... Require, typename... Rule, typename... Other>
struct basic_collector<matcher<type_list<Reject...>, type_list<Require...>, Rule...>, Other...> {
/*! @brief Current matcher. */
using current_type = matcher<type_list<Reject...>, type_list<Require...>, Rule...>;
/**
* @brief Adds a grouping matcher to the collector.
* @tparam AllOf Types of components tracked by the matcher.
* @tparam NoneOf Types of components used to filter out entities.
* @return The updated collector.
*/
template<typename... AllOf, typename... NoneOf>
static constexpr auto group(exclude_t<NoneOf...> = {}) ENTT_NOEXCEPT {
return basic_collector<matcher<type_list<>, type_list<>, type_list<NoneOf...>, AllOf...>, current_type, Other...>{};
}
/**
* @brief Adds an observing matcher to the collector.
* @tparam AnyOf Type of component for which changes should be detected.
* @return The updated collector.
*/
template<typename AnyOf>
static constexpr auto update() ENTT_NOEXCEPT {
return basic_collector<matcher<type_list<>, type_list<>, AnyOf>, current_type, Other...>{};
}
/**
* @brief Updates the filter of the last added matcher.
* @tparam AllOf Types of components required by the matcher.
* @tparam NoneOf Types of components used to filter out entities.
* @return The updated collector.
*/
template<typename... AllOf, typename... NoneOf>
static constexpr auto where(exclude_t<NoneOf...> = {}) ENTT_NOEXCEPT {
using extended_type = matcher<type_list<Reject..., NoneOf...>, type_list<Require..., AllOf...>, Rule...>;
return basic_collector<extended_type, Other...>{};
}
};
/*! @brief Variable template used to ease the definition of collectors. */
inline constexpr basic_collector<> collector{};
/**
* @brief Observer.
*
* An observer returns all the entities and only the entities that fit the
* requirements of at least one matcher. Moreover, it's guaranteed that the
* entity list is tightly packed in memory for fast iterations.<br/>
* In general, observers don't stay true to the order of any set of components.
*
* Observers work mainly with two types of matchers, provided through a
* collector:
*
* * Observing matcher: an observer will return at least all the living entities
* for which one or more of the given components have been updated and not yet
* destroyed.
* * Grouping matcher: an observer will return at least all the living entities
* that would have entered the given group if it existed and that would have
* not yet left it.
*
* If an entity respects the requirements of multiple matchers, it will be
* returned once and only once by the observer in any case.
*
* Matchers support also filtering by means of a _where_ clause that accepts
* both a list of types and an exclusion list.<br/>
* Whenever a matcher finds that an entity matches its requirements, the
* condition of the filter is verified before to register the entity itself.
* Moreover, a registered entity isn't returned by the observer if the condition
* set by the filter is broken in the meantime.
*
* @b Important
*
* Iterators aren't invalidated if:
*
* * New instances of the given components are created and assigned to entities.
* * The entity currently pointed is modified (as an example, if one of the
* given components is removed from the entity to which the iterator points).
* * The entity currently pointed is destroyed.
*
* In all the other cases, modifying the pools of the given components in any
* way invalidates all the iterators and using them results in undefined
* behavior.
*
* @warning
* Lifetime of an observer doesn't necessarily have to overcome that of the
* registry to which it is connected. However, the observer must be disconnected
* from the registry before being destroyed to avoid crashes due to dangling
* pointers.
*
* @tparam Entity A valid entity type (see entt_traits for more details).
*/
template<typename Entity>
class basic_observer {
using payload_type = std::uint32_t;
template<typename>
struct matcher_handler;
template<typename... Reject, typename... Require, typename AnyOf>
struct matcher_handler<matcher<type_list<Reject...>, type_list<Require...>, AnyOf>> {
template<std::size_t Index>
static void maybe_valid_if(basic_observer &obs, basic_registry<Entity> &reg, const Entity entt) {
if(reg.template all_of<Require...>(entt) && !reg.template any_of<Reject...>(entt)) {
if(!obs.storage.contains(entt)) {
obs.storage.emplace(entt);
}
obs.storage.get(entt) |= (1 << Index);
}
}
template<std::size_t Index>
static void discard_if(basic_observer &obs, basic_registry<Entity> &, const Entity entt) {
if(obs.storage.contains(entt) && !(obs.storage.get(entt) &= (~(1 << Index)))) {
obs.storage.erase(entt);
}
}
template<std::size_t Index>
static void connect(basic_observer &obs, basic_registry<Entity> &reg) {
(reg.template on_destroy<Require>().template connect<&discard_if<Index>>(obs), ...);
(reg.template on_construct<Reject>().template connect<&discard_if<Index>>(obs), ...);
reg.template on_update<AnyOf>().template connect<&maybe_valid_if<Index>>(obs);
reg.template on_destroy<AnyOf>().template connect<&discard_if<Index>>(obs);
}
static void disconnect(basic_observer &obs, basic_registry<Entity> &reg) {
(reg.template on_destroy<Require>().disconnect(obs), ...);
(reg.template on_construct<Reject>().disconnect(obs), ...);
reg.template on_update<AnyOf>().disconnect(obs);
reg.template on_destroy<AnyOf>().disconnect(obs);
}
};
template<typename... Reject, typename... Require, typename... NoneOf, typename... AllOf>
struct matcher_handler<matcher<type_list<Reject...>, type_list<Require...>, type_list<NoneOf...>, AllOf...>> {
template<std::size_t Index, typename... Ignore>
static void maybe_valid_if(basic_observer &obs, basic_registry<Entity> &reg, const Entity entt) {
auto condition = [&reg, entt]() {
if constexpr(sizeof...(Ignore) == 0) {
return reg.template all_of<AllOf..., Require...>(entt) && !reg.template any_of<NoneOf..., Reject...>(entt);
} else {
return reg.template all_of<AllOf..., Require...>(entt) && ((std::is_same_v<Ignore..., NoneOf> || !reg.template any_of<NoneOf>(entt)) && ...) && !reg.template any_of<Reject...>(entt);
}
};
if(condition()) {
if(!obs.storage.contains(entt)) {
obs.storage.emplace(entt);
}
obs.storage.get(entt) |= (1 << Index);
}
}
template<std::size_t Index>
static void discard_if(basic_observer &obs, basic_registry<Entity> &, const Entity entt) {
if(obs.storage.contains(entt) && !(obs.storage.get(entt) &= (~(1 << Index)))) {
obs.storage.erase(entt);
}
}
template<std::size_t Index>
static void connect(basic_observer &obs, basic_registry<Entity> &reg) {
(reg.template on_destroy<Require>().template connect<&discard_if<Index>>(obs), ...);
(reg.template on_construct<Reject>().template connect<&discard_if<Index>>(obs), ...);
(reg.template on_construct<AllOf>().template connect<&maybe_valid_if<Index>>(obs), ...);
(reg.template on_destroy<NoneOf>().template connect<&maybe_valid_if<Index, NoneOf>>(obs), ...);
(reg.template on_destroy<AllOf>().template connect<&discard_if<Index>>(obs), ...);
(reg.template on_construct<NoneOf>().template connect<&discard_if<Index>>(obs), ...);
}
static void disconnect(basic_observer &obs, basic_registry<Entity> &reg) {
(reg.template on_destroy<Require>().disconnect(obs), ...);
(reg.template on_construct<Reject>().disconnect(obs), ...);
(reg.template on_construct<AllOf>().disconnect(obs), ...);
(reg.template on_destroy<NoneOf>().disconnect(obs), ...);
(reg.template on_destroy<AllOf>().disconnect(obs), ...);
(reg.template on_construct<NoneOf>().disconnect(obs), ...);
}
};
template<typename... Matcher>
static void disconnect(basic_registry<Entity> &reg, basic_observer &obs) {
(matcher_handler<Matcher>::disconnect(obs, reg), ...);
}
template<typename... Matcher, std::size_t... Index>
void connect(basic_registry<Entity> &reg, std::index_sequence<Index...>) {
static_assert(sizeof...(Matcher) < std::numeric_limits<payload_type>::digits, "Too many matchers");
(matcher_handler<Matcher>::template connect<Index>(*this, reg), ...);
release.template connect<&basic_observer::disconnect<Matcher...>>(reg);
}
public:
/*! @brief Underlying entity identifier. */
using entity_type = Entity;
/*! @brief Unsigned integer type. */
using size_type = std::size_t;
/*! @brief Random access iterator type. */
using iterator = typename basic_sparse_set<Entity>::iterator;
/*! @brief Default constructor. */
basic_observer()
: release{},
storage{} {}
/*! @brief Default copy constructor, deleted on purpose. */
basic_observer(const basic_observer &) = delete;
/*! @brief Default move constructor, deleted on purpose. */
basic_observer(basic_observer &&) = delete;
/**
* @brief Creates an observer and connects it to a given registry.
* @tparam Matcher Types of matchers to use to initialize the observer.
* @param reg A valid reference to a registry.
*/
template<typename... Matcher>
basic_observer(basic_registry<entity_type> &reg, basic_collector<Matcher...>)
: basic_observer{} {
connect<Matcher...>(reg, std::index_sequence_for<Matcher...>{});
}
/*! @brief Default destructor. */
~basic_observer() = default;
/**
* @brief Default copy assignment operator, deleted on purpose.
* @return This observer.
*/
basic_observer &operator=(const basic_observer &) = delete;
/**
* @brief Default move assignment operator, deleted on purpose.
* @return This observer.
*/
basic_observer &operator=(basic_observer &&) = delete;
/**
* @brief Connects an observer to a given registry.
* @tparam Matcher Types of matchers to use to initialize the observer.
* @param reg A valid reference to a registry.
*/
template<typename... Matcher>
void connect(basic_registry<entity_type> &reg, basic_collector<Matcher...>) {
disconnect();
connect<Matcher...>(reg, std::index_sequence_for<Matcher...>{});
storage.clear();
}
/*! @brief Disconnects an observer from the registry it keeps track of. */
void disconnect() {
if(release) {
release(*this);
release.reset();
}
}
/**
* @brief Returns the number of elements in an observer.
* @return Number of elements.
*/
[[nodiscard]] size_type size() const ENTT_NOEXCEPT {
return storage.size();
}
/**
* @brief Checks whether an observer is empty.
* @return True if the observer is empty, false otherwise.
*/
[[nodiscard]] bool empty() const ENTT_NOEXCEPT {
return storage.empty();
}
/**
* @brief Direct access to the list of entities of the observer.
*
* The returned pointer is such that range `[data(), data() + size())` is
* always a valid range, even if the container is empty.
*
* @note
* Entities are in the reverse order as returned by the `begin`/`end`
* iterators.
*
* @return A pointer to the array of entities.
*/
[[nodiscard]] const entity_type *data() const ENTT_NOEXCEPT {
return storage.data();
}
/**
* @brief Returns an iterator to the first entity of the observer.
*
* The returned iterator points to the first entity of the observer. If the
* container is empty, the returned iterator will be equal to `end()`.
*
* @return An iterator to the first entity of the observer.
*/
[[nodiscard]] iterator begin() const ENTT_NOEXCEPT {
return storage.basic_sparse_set<entity_type>::begin();
}
/**
* @brief Returns an iterator that is past the last entity of the observer.
*
* The returned iterator points to the entity following the last entity of
* the observer. Attempting to dereference the returned iterator results in
* undefined behavior.
*
* @return An iterator to the entity following the last entity of the
* observer.
*/
[[nodiscard]] iterator end() const ENTT_NOEXCEPT {
return storage.basic_sparse_set<entity_type>::end();
}
/*! @brief Clears the underlying container. */
void clear() ENTT_NOEXCEPT {
storage.clear();
}
/**
* @brief Iterates entities and applies the given function object to them.
*
* The function object is invoked for each entity.<br/>
* The signature of the function must be equivalent to the following form:
*
* @code{.cpp}
* void(const entity_type);
* @endcode
*
* @tparam Func Type of the function object to invoke.
* @param func A valid function object.
*/
template<typename Func>
void each(Func func) const {
for(const auto entity: *this) {
func(entity);
}
}
/**
* @brief Iterates entities and applies the given function object to them,
* then clears the observer.
*
* @sa each
*
* @tparam Func Type of the function object to invoke.
* @param func A valid function object.
*/
template<typename Func>
void each(Func func) {
std::as_const(*this).each(std::move(func));
clear();
}
private:
delegate<void(basic_observer &)> release;
basic_storage<entity_type, payload_type> storage;
};
} // namespace entt
#endif