radio_button_delegate.hpp

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// Copyright Take Vos 2023.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "../notifier.hpp"
 
namespace hi { inline namespace v1 {
 
class radio_button_delegate {
public:
    using notifier_type = notifier<>;
    using callback_token = notifier_type::callback_token;
    using callback_proto = notifier_type::callback_proto;
 
    virtual ~button_delegate() = default;
 
    virtual void init(widget& sender) noexcept {}
 
    virtual void deinit(widget& sender) noexcept {}
 
    virtual void activate(widget& sender) noexcept = 0;
 
    [[nodiscard]] virtual widget_state state(widget const& sender) const noexcept
    {
        return widget_state::off;
    }
 
    [[nodiscard]] callback_token
    subscribe(forward_of<callback_proto> auto&& callback, callback_flags flags = callback_flags::synchronous) noexcept
    {
        return _notifier.subscribe(hi_forward(callback), flags);
    }
 
protected:
    notifier_type _notifier;
};
 
template<typename T>
class default_radio_button_delegate : public radio_button_delegate {
public:
    using value_type = T;
 
    observer<value_type> value;
    observer<value_type> on_value;
 
    default_radio_button_delegate(
        forward_of<observer<value_type>> auto&& value,
        forward_of<observer<value_type>> auto&& on_value) noexcept :
        value(hi_forward(value)), on_value(hi_forward(on_value))
    {
        // clang-format off
        _value_cbt = this->value.subscribe([&](auto...){ this->_notifier(); });
        _on_value_cbt = this->on_value.subscribe([&](auto...){ this->_notifier(); });
        // clang-format on
    }
 
    [[nodiscard]] widget_state state(widget const& sender) const noexcept override
    {
        if (*value == *on_value) {
            return widget_state::on;
        } else {
            return widget_state::off;
        }
    }
 
    void activate(widget& sender) noexcept override
    {
        value = *on_value;
    }
private:
    typename decltype(value)::callback_token _value_cbt;
    typename decltype(on_value)::callback_token _on_value_cbt;
};
 
}} // namespace hi::v1