true_type_font.hpp

// Copyright Take Vos 2019-2021.
// 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 "font.hpp"
#include "../graphic_path.hpp"
#include "../resource_view.hpp"
#include "../URL.hpp"
#include "../counters.hpp"
#include <memory>
 
namespace tt {
 
class true_type_font final : public font {
private:
    std::optional<URL> url;
 
    mutable std::unique_ptr<resource_view> view;
 
    uint16_t OS2_xHeight = 0;
    uint16_t OS2_HHeight = 0;
 
    float unitsPerEm;
    float emScale;
    bool locaTableIsOffset32;
 
    float ascender;
    float descender;
    float lineGap;
    uint16_t numberOfHMetrics;
 
    int numGlyphs;
 
public:
    true_type_font(std::unique_ptr<resource_view> view) : url(), view(std::move(view))
    {
        parse_font_directory();
    }
 
    true_type_font(URL const &url) : url(url), view(url.loadView())
    {
        ++global_counter<"ttf:map">;
        try {
            parse_font_directory();
 
            // Clear the view to reclaim resources.
            view = {};
            ++global_counter<"ttf:unmap">;
 
        } catch (std::exception const &e) {
            throw parse_error("{}: Could not parse font directory.\n{}", to_string(url), e.what());
        }
    }
 
    true_type_font() = delete;
    true_type_font(true_type_font const &other) = delete;
    true_type_font &operator=(true_type_font const &other) = delete;
    true_type_font(true_type_font &&other) = delete;
    true_type_font &operator=(true_type_font &&other) = delete;
    ~true_type_font() = default;
 
    [[nodiscard]] bool loaded() const noexcept override
    {
        return static_cast<bool>(view);
    }
 
    [[nodiscard]] tt::glyph_id find_glyph(char32_t c) const noexcept override;
 
    std::optional<tt::glyph_id> load_glyph(tt::glyph_id glyph_id, graphic_path &path) const noexcept override;
 
    bool load_glyph_metrics(tt::glyph_id glyph_id, glyph_metrics &metrics, tt::glyph_id lookahead_glyph_id = tt::glyph_id{})
        const noexcept override;
 
private:
    [[nodiscard]] std::span<std::byte const> getTableBytes(char const *table_name) const;
 
    void parse_font_directory();
 
    void parseHeadTable(std::span<std::byte const> headTableBytes);
 
    void parseHheaTable(std::span<std::byte const> bytes);
 
    void parseNameTable(std::span<std::byte const> bytes);
 
    void parseOS2Table(std::span<std::byte const> bytes);
 
    [[nodiscard]] tt::unicode_mask parseCharacterMap();
 
    void parseMaxpTable(std::span<std::byte const> bytes);
 
    bool getGlyphBytes(tt::glyph_id glyph_id, std::span<std::byte const> &bytes) const noexcept;
 
    bool update_glyph_metrics(
        tt::glyph_id glyph_id,
        glyph_metrics &metrics,
        tt::glyph_id kern_glyph1_id = tt::glyph_id{},
        tt::glyph_id kern_glyph2_id = tt::glyph_id{}) const noexcept;
 
    bool loadSimpleGlyph(std::span<std::byte const> bytes, graphic_path &glyph) const noexcept;
 
    bool loadCompoundGlyph(std::span<std::byte const> bytes, graphic_path &glyph, tt::glyph_id &metrics_glyph_id) const noexcept;
 
    bool loadCompoundglyph_metrics(std::span<std::byte const> bytes, tt::glyph_id &metrics_glyph_id) const noexcept;
};
 
} // namespace tt