font_book.hpp

// Copyright Take Vos 2020-2021.
// 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_description.hpp"
#include "grapheme.hpp"
#include "font.hpp"
#include "font_family_id.hpp"
#include "font_id.hpp"
#include "font_grapheme_id.hpp"
#include "font_glyph_ids.hpp"
#include "../URL.hpp"
#include "../alignment.hpp"
#include "../subsystem.hpp"
#include <limits>
#include <array>
#include <new>
#include <atomic>
 
namespace tt {
 
class font_book {
public:
    font_book(std::vector<URL> const &font_directories);
 
    font_id register_font(URL url, bool post_process = true);
 
    void post_process() noexcept;
 
    [[nodiscard]] font_family_id find_family(std::string_view family_name) const noexcept;
 
    [[nodiscard]] font_family_id register_family(std::string_view family_name) noexcept;
 
    [[nodiscard]] font_id find_font(font_family_id family_id, font_variant variant) const noexcept;
 
    [[nodiscard]] font_id find_font(font_family_id family_id, font_weight weight, bool italic) const noexcept;
 
    [[nodiscard]] font_id find_font(std::string_view family_name, font_weight weight, bool italic) const noexcept;
 
    [[nodiscard]] font const &get_font(font_id font_id) const noexcept;
 
    [[nodiscard]] font_glyph_ids find_glyph(font_id font_id, grapheme grapheme) const noexcept;
 
    [[nodiscard]] static font_book &global() noexcept
    {
        return *start_subsystem_or_terminate(_global, nullptr, subsystem_init, subsystem_deinit);
    }
 
private:
    struct fontEntry {
        URL url;
        font_description description;
        mutable std::unique_ptr<font> font;
        std::vector<font_id> fallbacks;
 
        fontEntry(URL url, font_description description) noexcept :
            url(std::move(url)), description(std::move(description)), font(), fallbacks()
        {
        }
    };
 
    static inline std::atomic<font_book *> _global;
 
    std::unordered_map<std::string, font_family_id> family_names;
 
    std::unordered_map<std::string, std::string> family_name_fallback_chain;
 
    std::vector<std::array<font_id, font_variant::max()>> font_variants;
 
    std::vector<fontEntry> font_entries;
 
    mutable std::unordered_map<std::string, font_family_id> family_name_cache;
 
    mutable std::unordered_map<font_grapheme_id, font_glyph_ids> glyph_cache;
    void calculate_fallback_fonts(
        fontEntry &entry,
        std::function<bool(font_description const &, font_description const &)> predicate) noexcept;
 
    [[nodiscard]] font_glyph_ids find_glyph_actual(font_id font_id, grapheme grapheme) const noexcept;
 
    // void morph_glyphs(glyph_array &glyphs) const noexcept;
 
    // void atlas_lookup(glyph &glyph) noexcept;
 
    // void atlas_lookup(glyph_array &glyphs) noexcept;
 
    // void kern_glyphs(glyph_array &glyphs) const noexcept;
 
    [[nodiscard]] std::string const &find_fallback_family_name(std::string const &name) const noexcept;
 
    void create_family_name_fallback_chain() noexcept;
 
    [[nodiscard]] static font_book *subsystem_init() noexcept
    {
        return new font_book(std::vector<URL>{URL::urlFromSystemfontDirectory()});
    }
 
    static void subsystem_deinit() noexcept
    {
        if (auto tmp = _global.exchange(nullptr)) {
            delete tmp;
        }
    }
};
 
} // namespace tt