shaping

type Bounds struct {
	// Ascent is the maximum ascent away from the baseline. This value is typically
	// positive in coordiate systems that grow up.
	Ascent fixed.Int26_6
	// Descent is the maximum descent away from the baseline. This value is typically
	// negative in coordinate systems that grow up.
	Descent fixed.Int26_6
	// Gap is the height of empty pixels between lines. This value is typically positive
	// in coordinate systems that grow up.
	Gap fixed.Int26_6
}

type Glyph struct {
	Width    fixed.Int26_6
	Height   fixed.Int26_6
	XBearing fixed.Int26_6
	YBearing fixed.Int26_6
	XAdvance fixed.Int26_6
	YAdvance fixed.Int26_6
	XOffset  fixed.Int26_6
	YOffset  fixed.Int26_6
	Cluster  int
	Glyph    fonts.GID
	Mask     harfbuzz.GlyphMask
}

type Input struct {
	// Text is the body of text being shaped. Only the range Text[RunStart:RunEnd] is considered
	// for shaping, with the rest provided as context for the shaper. This helps with, for example,
	// cross-run Arabic shaping or handling combining marks at the start of a run.
	Text []rune
	// RunStart and RunEnd indicate the subslice of Text being shaped.
	RunStart, RunEnd int
	// Direction is the directionality of the text.
	Direction di.Direction
	// Face is the font face to render the text in.
	Face font.Face

	// Size is the requested size of the font.
	// More generally, it is a scale factor applied to the resulting metrics.
	// For instance, given a device resolution (in dpi) and a point size (like 14), the `Size` to
	// get result in pixels is given by : pointSize * dpi / 72
	Size fixed.Int26_6

	// Script is an identifier for the writing system used in the text.
	Script language.Script

	// Language is an identifier for the language of the text.
	Language language.Language
}

type InvalidRunError struct {
	RunStart, RunEnd, TextLength int
}

type MissingGlyphError struct {
	fonts.GID
}

type Output struct {
	// Advance is the distance the Dot has advanced.
	Advance fixed.Int26_6
	// Glyphs are the shaped output text.
	Glyphs []Glyph
	// LineBounds describes the font's suggested line bounding dimensions. The
	// dimensions described should contain any glyphs from the given font.
	LineBounds Bounds
	// GlyphBounds describes a tight bounding box on the specific glyphs contained
	// within this output. The dimensions may not be sufficient to contain all
	// glyphs within the chosen font.
	GlyphBounds Bounds
}

type Shaper interface {
	// Shape takes an Input and shapes it into the Output.
	Shape(Input) Output
}

type UnimplementedDirectionError struct {
	Direction di.Direction
}