font

type Descriptor struct {
	FontName    string     // required, except (usually) for Type 3 fonts
	FontFamily  string     // optional
	FontStretch os2.Width  // optional
	FontWeight  os2.Weight // optional

	IsFixedPitch bool // flag
	IsSerif      bool // flag
	IsSymbolic   bool // flag
	IsScript     bool // flag
	IsItalic     bool // flag
	IsAllCap     bool // flag
	IsSmallCap   bool // flag
	ForceBold    bool // flag

	FontBBox     *pdf.Rectangle // required, except for Type 3 fonts
	ItalicAngle  float64        // required
	Ascent       float64        // required, except for Type 3 fonts
	Descent      float64        // required, except for Type 3 fonts
	Leading      float64        // optional (default: 0)
	CapHeight    float64        // required, except if no latin chars or for Type 3 fonts
	XHeight      float64        // optional (default: 0)
	StemV        float64        // required, except for Type 3 fonts (0 = unknown, set to -1 for Type 3 fonts)
	StemH        float64        // optional (default: 0)
	MaxWidth     float64        // optional (default: 0)
	AvgWidth     float64        // optional (default: 0)
	MissingWidth float64        // optional (default: 0)
}

type Dict interface {
	Embed(w pdf.Putter, fontDictRef pdf.Reference) error
}

type Dicts struct {
	PostScriptName pdf.Name
	SubsetTag      string

	FontDict       pdf.Dict
	CIDFontDict    pdf.Dict
	FontDescriptor *Descriptor
	FontProgramRef pdf.Reference
	FontProgram    *pdf.Stream
	Type           EmbeddingType
}

type Embedded interface {
	pdf.Resource
	WritingMode() int // 0 = horizontal, 1 = vertical
	ForeachWidth(s pdf.String, yield func(width float64, is_space bool))
}

type EmbeddingType int

type Font interface {
	Embed(w pdf.Putter, opt *Options) (Layouter, error)
}

type Geometry struct {
	Ascent             float64
	Descent            float64 // negative
	BaseLineDistance   float64
	UnderlinePosition  float64
	UnderlineThickness float64

	GlyphExtents []pdf.Rectangle // indexed by GID
	Widths       []float64       // indexed by GID
}

type Glyph struct {
	GID glyph.ID

	// Advance is the advance width for the current glyph the client
	// wishes to achieve.  It is measured in PDF text space units,
	// and is already scaled by the font size.
	Advance float64

	// Rise is by how much the glyph should be lifted above the baseline.  The
	// rise is measured in PDF text space units, and is already scaled by the
	// font size.
	Rise float64

	Text []rune
}

type GlyphSeq struct {
	Skip float64
	Seq  []Glyph
}

type Layouter interface {
	Embedded

	// GetGeometry returns font metrics required for typesetting.
	GetGeometry() *Geometry

	// Layout appends a string to a glyph sequence.  The string is typeset at
	// the given point size.
	//
	// If seq is non-nil, a new glyph sequence is allocated.  The resulting
	// GlyphSeq is returned.  If seq is not nil, the return value is guaranteed
	// to be equal to seq.
	Layout(seq *GlyphSeq, ptSize float64, s string) *GlyphSeq

	// CodeAndWidth converts a glyph ID (corresponding to the given text) into
	// a PDF character code The character code is appended to s. The function
	// returns the new string s, the width of the glyph in PDF text space units
	// (still to be multiplied by the font size), and a value indicating
	// whether PDF word spacing adjustment applies to this glyph.
	//
	// As a side effect, this function allocates codes for the given
	// glyph/text combination in the font's encoding.
	CodeAndWidth(s pdf.String, gid glyph.ID, rr []rune) (pdf.String, float64, bool)

	// Close writes the used subset of the font to the PDF file. After close
	// has been called, only previously used glyph/text combinations can be
	// used.
	//
	// If this function is not called by the user, the font will be
	// automatically closed when the PDF file is closed.
	Close() error
}

type Options struct {
	Language language.Tag

	GsubFeatures map[string]bool
	GposFeatures map[string]bool

	// Composite specifies whether to embed the font as a composite font.
	Composite bool

	MakeGIDToCID func() cmap.GIDToCID                // only used for composite fonts
	MakeEncoder  func(cmap.GIDToCID) cmap.CIDEncoder // only used for composite fonts

	// The default resource name to use for the font within content streams.
	// Leave blank to have names allocated automatically.
	ResName pdf.Name
}