widget_baseline.hpp

// Copyright Take Vos 2022.
// 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 "../alignment.hpp"
 
namespace hi::inline v1 {
 
class widget_baseline {
public:
    constexpr widget_baseline() noexcept = default;
    constexpr widget_baseline(widget_baseline const&) noexcept = default;
    constexpr widget_baseline(widget_baseline&&) noexcept = default;
    constexpr widget_baseline& operator=(widget_baseline const&) noexcept = default;
    constexpr widget_baseline& operator=(widget_baseline&&) noexcept = default;
    [[nodiscard]] constexpr friend bool operator==(widget_baseline const&, widget_baseline const&) noexcept = default;
 
    constexpr widget_baseline(
        float priority,
        vertical_alignment alignment,
        float cap_height,
        float graphic_height = 0.0f) noexcept :
        _priority(priority)
    {
        if (alignment == vertical_alignment::top) {
            _gain = 1.0f;
            _bias = graphic_height * -0.5f + cap_height * -0.5f;
        } else if (alignment == vertical_alignment::middle) {
            _gain = 0.5f;
            _bias = cap_height * -0.5f;
        } else if (alignment == vertical_alignment::bottom) {
            _gain = 0.5f;
            _bias = graphic_height * 0.5f + cap_height * -0.5f;
        } else {
            hi_no_default();
        }
    }
 
    constexpr widget_baseline(float priority, float gain, float bias) noexcept : _priority(priority), _gain(gain), _bias(bias) {}
 
    [[nodiscard]] constexpr auto friend operator<=>(widget_baseline const& lhs, widget_baseline const& rhs) noexcept
    {
        return lhs._priority <=> rhs._priority;
    }
 
    [[nodiscard]] constexpr bool empty() const noexcept
    {
        return _priority == 0.0f;
    }
 
    explicit operator bool() const noexcept
    {
        return not empty();
    }
 
    [[nodiscard]] constexpr float absolute(float height) const noexcept
    {
        return height * _gain + _bias;
    }
 
private:
    float _priority = 0.0f;
    float _gain = 0.0f;
    float _bias = 0.0f;
};
 
} // namespace hi::inline v1