FontVariant.hpp

// Copyright 2020 Pokitec
// All rights reserved.
 
#pragma once
 
#include "TTauri/Text/FontWeight.hpp"
 
namespace tt {
 
class FontVariant {
    uint8_t value;
 
public:
    constexpr static int max() { return 20; }
    constexpr static int half() { return max() / 2; }
 
    constexpr FontVariant(FontWeight weight, bool italic) noexcept : value(static_cast<uint8_t>(static_cast<int>(weight) + (italic ? half() : 0))) {}
    constexpr FontVariant() noexcept : FontVariant(FontWeight::Regular, false) {}
    constexpr FontVariant(FontWeight weight) noexcept : FontVariant(weight, false) {}
    constexpr FontVariant(bool italic) noexcept : FontVariant(FontWeight::Regular, italic) {}
 
    constexpr FontWeight weight() const noexcept {
        tt_assume(value < max());
        return static_cast<FontWeight>(value % half());
    }
 
    [[nodiscard]] constexpr bool italic() const noexcept {
        tt_assume(value < max());
        return value >= half();
    }
 
    constexpr FontVariant &set_weight(FontWeight rhs) noexcept {
        value = static_cast<uint8_t>(static_cast<int>(rhs) + (italic() ? half() : 0));
        tt_assume(value < max());
        return *this;
    }
 
    constexpr FontVariant &set_italic(bool rhs) noexcept {
        value = static_cast<uint8_t>(static_cast<int>(weight()) + (rhs ? half() : 0));
        tt_assume(value < max());
        return *this;
    }
 
    constexpr operator int () const noexcept {
        tt_assume(value < max());
        return value;
    }
 
    constexpr FontVariant alternative(int i) const noexcept {
        tt_assume(i >= 0 && i < max());
        ttlet w = FontWeight_alterative(weight(), i % half());
        ttlet it = italic() == (i < half());
        return {w, it};
    }
 
    [[nodiscard]] friend std::string to_string(FontVariant const &rhs) noexcept {
        return fmt::format("{}", rhs.weight(), rhs.italic() ? "/italic" : "");
    }
 
    friend std::ostream &operator<<(std::ostream &lhs, FontVariant const &rhs) {
        return lhs << to_string(rhs);
    }
};
 
}