TrueTypeFont.hpp

// Copyright 2019, 2020 Pokitec
// All rights reserved.
 
#pragma once
 
#include "TTauri/Text/Font.hpp"
#include "TTauri/Foundation/Path.hpp"
#include "TTauri/Foundation/ResourceView.hpp"
#include <memory>
 
namespace tt {
 
class TrueTypeFont final: public Font {
private:
    std::unique_ptr<ResourceView> view;
 
    nonstd::span<std::byte const> file_bytes;
 
    uint16_t OS2_xHeight = 0;
    uint16_t OS2_HHeight = 0;
 
 
    nonstd::span<std::byte const> cmapTableBytes;
 
    nonstd::span<std::byte const> cmapBytes;
 
    nonstd::span<std::byte const> glyfTableBytes;
 
    nonstd::span<std::byte const> headTableBytes;
    float unitsPerEm;
    float emScale;
    bool locaTableIsOffset32;
 
    nonstd::span<std::byte const> hheaTableBytes;
    float ascender;
    float descender;
    float lineGap;
    uint16_t numberOfHMetrics;
 
    nonstd::span<std::byte const> hmtxTableBytes;
 
    nonstd::span<std::byte const> locaTableBytes;
 
    nonstd::span<std::byte const> maxpTableBytes;
    int numGlyphs;
 
    nonstd::span<std::byte const> nameTableBytes;
 
    nonstd::span<std::byte const> postTableBytes;
 
    nonstd::span<std::byte const> os2TableBytes;
 
    nonstd::span<std::byte const> kernTableBytes;
 
public:
    TrueTypeFont(nonstd::span<std::byte const> bytes) :
        file_bytes(bytes) {
        parseFontDirectory();
    }
 
    TrueTypeFont(std::unique_ptr<ResourceView> view) :
        view(std::move(view)) {
        file_bytes = this->view->bytes();
        parseFontDirectory();
    }
 
    TrueTypeFont() = delete;
    TrueTypeFont(TrueTypeFont const &other) = delete;
    TrueTypeFont &operator=(TrueTypeFont const &other) = delete;
    TrueTypeFont(TrueTypeFont &&other) = delete;
    TrueTypeFont &operator=(TrueTypeFont &&other) = delete;
    ~TrueTypeFont() = default;
 
    [[nodiscard]] GlyphID find_glyph(char32_t c) const noexcept override;
    
    std::optional<GlyphID> loadGlyph(GlyphID glyph_id, Path &path) const noexcept override;
 
    bool loadGlyphMetrics(GlyphID glyph_id, GlyphMetrics &metrics, GlyphID lookahead_glyph_id=GlyphID{}) const noexcept override;
 
private:
    void parseFontDirectory();
 
    void parseHeadTable(nonstd::span<std::byte const> headTableBytes);
 
    void parseHheaTable(nonstd::span<std::byte const> bytes);
 
    void parseNameTable(nonstd::span<std::byte const> bytes);
 
    void parseOS2Table(nonstd::span<std::byte const> bytes);
 
    [[nodiscard]] UnicodeRanges parseCharacterMap();
 
 
    void parseMaxpTable(nonstd::span<std::byte const> bytes);
 
    bool getGlyphBytes(GlyphID glyph_id, nonstd::span<std::byte const> &bytes) const noexcept;
 
    bool updateGlyphMetrics(GlyphID glyph_id, GlyphMetrics &metrics, GlyphID kern_glyph1_id=GlyphID{}, GlyphID kern_glyph2_id=GlyphID{}) const noexcept;
 
    bool loadSimpleGlyph(nonstd::span<std::byte const> bytes, Path &glyph) const noexcept;
 
    bool loadCompoundGlyph(nonstd::span<std::byte const> bytes, Path &glyph, GlyphID &metrics_glyph_id) const noexcept;
 
    bool loadCompoundGlyphMetrics(nonstd::span<std::byte const> bytes, GlyphID &metrics_glyph_id) const noexcept;
 
 
};
 
}