Signal / Slots

#ifndef ONIDEV_UI_SIGNAL_H_INCLUDED
#define ONIDEV_UI_SIGNAL_H_INCLUDED

#include <functional>
#include "signal.incl"

template <typename... Args>
class Signal
{
    // http://stackoverflow.com/questions/21192659/variadic-templates-and-stdbind
    template<class T, int... Is>
    void connect_member(void (T::*field)(Args...), T* t, int_sequence<Is...>)
    {
        _slot = std::bind(field, t, placeholder_template<Is>{}...);
    }

public:
    typedef std::function<void(Args...)> Slot;

    template<class T>
    void connect(void (T::*field)(Args...), T* t)
    {
        connect_member(field, t, make_int_sequence<sizeof...(Args)>{});
    }
    void connect(Slot const& slot) const
    {
        _slot = slot;
    }
    void disconnect() const
    {
        _slot = Slot();
    }
    void emit(Args... p)
    {
        if(_slot)
            _slot(p...);
    }
    Signal& operator=(Signal const& other)
    {
        disconnect();
    }

private:
    mutable Slot _slot;
};

#endif


--- signal.incl ---

#include <cstddef>
#include <type_traits>

template<int...>
struct int_sequence
{
};

template<int N, int... Is>
struct make_int_sequence:
    make_int_sequence<N-1, N-1, Is...>
{
};
template<int... Is>
struct make_int_sequence<0, Is...>:
    int_sequence<Is...>
{
};

template<int>
struct placeholder_template
{
};

namespace std
{
template<int N>
struct is_placeholder< placeholder_template<N> >
    : integral_constant<int, N+1>
{
};
}