add incomplete Text type in text package

text/text.go

@@ -0,0 +1,232 @@
+package text
+
+import (
+	"image"
+	"image/color"
+	"image/draw"
+	"unicode"
+	"unicode/utf8"
+
+	"github.com/faiface/pixel"
+	"golang.org/x/image/font"
+	"golang.org/x/image/math/fixed"
+)
+
+var ASCII []rune
+
+func init() {
+	ASCII = make([]rune, unicode.MaxASCII-32)
+	for i := range ASCII {
+		ASCII[i] = rune(32 + i)
+	}
+}
+
+func RangeTable(table *unicode.RangeTable) []rune {
+	var runes []rune
+	for _, rng := range table.R16 {
+		for r := rng.Lo; r <= rng.Hi; r += rng.Stride {
+			runes = append(runes, rune(r))
+		}
+	}
+	for _, rng := range table.R32 {
+		for r := rng.Lo; r <= rng.Hi; r += rng.Stride {
+			runes = append(runes, rune(r))
+		}
+	}
+	return runes
+}
+
+type Text struct {
+	Dot pixel.Vec
+
+	color pixel.RGBA
+
+	prevR rune
+	atlas atlas
+	tris  pixel.TrianglesData
+	d     pixel.Drawer
+}
+
+func New(face font.Face, runeSets ...[]rune) *Text {
+	runes := []rune{unicode.ReplacementChar}
+	for _, set := range runeSets {
+		runes = append(runes, set...)
+	}
+
+	txt := &Text{
+		color: pixel.Alpha(1),
+		atlas: makeAtlas(face, runes),
+	}
+	txt.d.Picture = txt.atlas.pic
+	txt.d.Triangles = &txt.tris
+
+	txt.Clear()
+
+	return txt
+}
+
+func (txt *Text) Color(c color.Color) {
+	txt.color = pixel.ToRGBA(c)
+}
+
+func (txt *Text) Clear() {
+	txt.prevR = -1
+	txt.tris.SetLen(0)
+	txt.d.Dirty()
+}
+
+func (txt *Text) Write(p []byte) (n int, err error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+
+	n = len(p)
+
+	glyphTris := make(pixel.TrianglesData, 6)
+	for i := range glyphTris {
+		glyphTris[i].Color = txt.color
+		glyphTris[i].Intensity = 1
+	}
+
+	for len(p) > 0 {
+		r, size := utf8.DecodeRune(p)
+		p = p[size:]
+
+		switch r {
+		case '\n':
+			txt.Dot -= pixel.Y(txt.atlas.lineHeight)
+			txt.Dot = txt.Dot.WithX(0)
+			continue
+		case '\r':
+			txt.Dot = txt.Dot.WithX(0)
+			continue
+		case '\t':
+			//TODO
+			continue
+		}
+
+		glyph, ok := txt.atlas.mapping[r]
+		if !ok {
+			glyph = txt.atlas.mapping[unicode.ReplacementChar]
+		}
+
+		if txt.prevR >= 0 {
+			txt.Dot += pixel.X(txt.atlas.kern[struct{ r0, r1 rune }{txt.prevR, r}])
+		}
+
+		a := pixel.V(glyph.frame.Min.X(), glyph.frame.Min.Y())
+		b := pixel.V(glyph.frame.Max.X(), glyph.frame.Min.Y())
+		c := pixel.V(glyph.frame.Max.X(), glyph.frame.Max.Y())
+		d := pixel.V(glyph.frame.Min.X(), glyph.frame.Max.Y())
+
+		for i, v := range []pixel.Vec{a, b, c, a, c, d} {
+			glyphTris[i].Position = v - glyph.orig + txt.Dot
+			glyphTris[i].Picture = v
+		}
+
+		txt.tris = append(txt.tris, glyphTris...)
+
+		txt.Dot += pixel.X(glyph.advance)
+		txt.prevR = r
+	}
+
+	txt.d.Dirty()
+
+	return n, nil
+}
+
+func (txt *Text) Draw(t pixel.Target) {
+	txt.d.Draw(t)
+}
+
+type atlas struct {
+	pic        pixel.Picture
+	mapping    map[rune]glyph
+	kern       map[struct{ r0, r1 rune }]float64
+	lineHeight float64
+}
+
+type glyph struct {
+	orig    pixel.Vec
+	frame   pixel.Rect
+	advance float64
+}
+
+func makeAtlas(face font.Face, runes []rune) atlas {
+	//FIXME: don't put glyphs in just one row, make a square
+
+	width := fixed.Int26_6(0)
+	for _, r := range runes {
+		b, _, ok := face.GlyphBounds(r)
+		if !ok && r != unicode.ReplacementChar {
+			continue
+		}
+		width += b.Max.X - b.Min.X
+
+		// padding to avoid filtering artifacts
+		width = fixed.I(width.Ceil())
+		width += fixed.I(2)
+	}
+
+	atlasImg := image.NewRGBA(image.Rect(
+		0, 0,
+		width.Ceil(), (face.Metrics().Ascent + face.Metrics().Descent).Ceil(),
+	))
+	atlasHeight := float64(atlasImg.Bounds().Dy())
+
+	mapping := make(map[rune]glyph)
+
+	dot := fixed.Point26_6{
+		X: 0,
+		Y: face.Metrics().Ascent,
+	}
+
+	for _, r := range runes {
+		b, _, ok := face.GlyphBounds(r)
+		if !ok && r != unicode.ReplacementChar {
+			continue
+		}
+
+		dot.X -= b.Min.X
+
+		dr, mask, maskp, _, _ := face.Glyph(dot, r)
+		draw.Draw(atlasImg, dr, mask, maskp, draw.Src)
+
+		orig := pixel.V(
+			float64(dot.X)/(1<<6),
+			atlasHeight-float64(dot.Y)/(1<<6),
+		)
+
+		frame := pixel.R(
+			float64(dr.Min.X),
+			atlasHeight-float64(dr.Min.Y),
+			float64(dr.Max.X),
+			atlasHeight-float64(dr.Max.Y),
+		).Norm()
+
+		adv, _ := face.GlyphAdvance(r)
+		advance := float64(adv) / (1 << 6)
+
+		mapping[r] = glyph{orig, frame, advance}
+
+		dot.X += b.Max.X
+
+		// padding
+		dot.X = fixed.I(dot.X.Ceil())
+		dot.X += fixed.I(2)
+	}
+
+	kern := make(map[struct{ r0, r1 rune }]float64)
+	for _, r0 := range runes {
+		for _, r1 := range runes {
+			kern[struct{ r0, r1 rune }{r0, r1}] = float64(face.Kern(r0, r1)) / (1 << 6)
+		}
+	}
+
+	return atlas{
+		pixel.PictureDataFromImage(atlasImg),
+		mapping,
+		kern,
+		float64(face.Metrics().Height) / (1 << 6),
+	}
+}