font.h

// © Joseph Cameron - MIT License
 
#ifndef GDK_GRAPHICS_EXT_FONT_H
#define GDK_GRAPHICS_EXT_FONT_H
 
#include <gdk/graphics/texture_data.h>
 
#include <cstddef>
#include <memory>
#include <optional>
#include <span>
 
namespace gdk::graphics::ext {
    enum class font_sizing {
        ascent_to_descent,
        em
    };

    struct font_settings final {
        std::size_t face = 0;

        font_sizing sizing = font_sizing::ascent_to_descent;

        std::size_t atlas_edge = 512;

        std::size_t max_atlas_edge = 2048;
    };

    class font final {
    public:
        struct glyph {
            float s0 = 0; 
            float t0 = 0; 
            float s1 = 0; 
            float t1 = 0; 
 
            float left = 0;    
            float top = 0;     
            float width = 0;   
            float height = 0;  
            float advance = 0; 
        };

        [[nodiscard]] const glyph *try_get(char32_t aCodepoint);

        [[nodiscard]] const glyph &fallback() const;

        void clear();

        [[nodiscard]] float kerning(char32_t aLeft, char32_t aRight) const;

        [[nodiscard]] texture_data::view atlas() const;

        struct atlas_region {
            std::size_t x = 0, y = 0, width = 0, height = 0;
        };

        [[nodiscard]] std::optional<atlas_region> atlas_changed_since(std::size_t aGeneration) const;

        [[nodiscard]] std::size_t atlas_generation() const;

        [[nodiscard]] float line_height() const;

        [[nodiscard]] float ascent() const;

        [[nodiscard]] float descent() const;

        font(
            std::span<const texture_data::encoded_byte> aTrueTypeData,
            float aPixelSize,
            font_settings aSettings = {}
        );

        [[nodiscard]] std::size_t atlas_edge() const;
 
        ~font();
 
        font(font &&) noexcept;
        font &operator=(font &&) noexcept;
 
        font(const font &) = delete;
        font &operator=(const font &) = delete;
 
    private:
        struct impl;
        std::unique_ptr<impl> m_pImpl;
    };
}
 
#endif