utils_meta.hpp

#ifndef LXGUI_UTILS_META_HPP
#define LXGUI_UTILS_META_HPP
 
#include "lxgui/lxgui.hpp"
 
#include <type_traits>
 
namespace lxgui::utils {
 
namespace impl {
template<typename T>
struct first_function_argument_;
 
template<typename R, typename T, typename... Args>
struct first_function_argument_<R (*)(T, Args...)> {
    using type = T;
};
 
template<typename R, typename F, typename T, typename... Args>
struct first_function_argument_<R (F::*)(T, Args...)> {
    using type = T;
};
 
template<typename R, typename F, typename T, typename... Args>
struct first_function_argument_<R (F::*)(T, Args...) const> {
    using type = T;
};
} // namespace impl
 
template<typename T>
using first_function_argument =
    typename impl::first_function_argument_<decltype(&std::decay_t<T>::operator())>::type;
 
} // namespace lxgui::utils
 
#endif