Freetype-Go: move the pixel offset from the painter to the rasterizer.

R=rsc, r
CC=rog, golang-dev
http://codereview.appspot.com/1332041

freetype/freetype.go

@@ -145,7 +145,7 @@ func (c *RGBAContext) DrawText(pt raster.Point, s string) (err os.Error) {
 	advance, x0 := 0, pt.X
 	dx := raster.Fixed(-c.xmin << 8)
 	dy := raster.Fixed(-c.ymin << 8)
-	c.rp.Dy, y = c.ymin+int(pt.Y>>8), pt.Y&0xff
+	c.r.Dy, y = c.ymin+int(pt.Y>>8), pt.Y&0xff
 	y += dy
 	prev, hasPrev := truetype.Index(0), false
 	for _, ch := range s {
@@ -170,7 +170,7 @@ func (c *RGBAContext) DrawText(pt raster.Point, s string) (err os.Error) {
 		x = x0 + c.FUnitToFixed(advance)
 		// Break the co-ordinate down into an integer pixel part and a
 		// sub-pixel part, making sure that the latter is non-negative.
-		c.rp.Dx, x = c.xmin+int(x>>8), x&0xff
+		c.r.Dx, x = c.xmin+int(x>>8), x&0xff
 		x += dx
 		// Draw the contours.
 		c.r.Clear()

freetype/raster/paint.go

@@ -39,38 +39,34 @@ type AlphaPainter struct {
 	Image *image.Alpha
 	// The Porter-Duff composition operator.
 	Op draw.Op
-	// An offset (in pixels) to the painted spans.
-	Dx, Dy int
 }
 
 // Paint satisfies the Painter interface by painting ss onto an image.Alpha.
 func (r *AlphaPainter) Paint(ss []Span, done bool) {
 	for _, s := range ss {
-		y := r.Dy + s.Y
+		if s.Y < 0 {
-		if y < 0 {
 			continue
 		}
-		if y >= len(r.Image.Pixel) {
+		if s.Y >= len(r.Image.Pixel) {
 			return
 		}
-		p := r.Image.Pixel[y]
+		p := r.Image.Pixel[s.Y]
-		x0, x1 := r.Dx+s.X0, r.Dx+s.X1
+		if s.X0 < 0 {
-		if x0 < 0 {
+			s.X0 = 0
-			x0 = 0
 		}
-		if x1 > len(p) {
+		if s.X1 > len(p) {
-			x1 = len(p)
+			s.X1 = len(p)
 		}
 		if r.Op == draw.Over {
 			a := int(s.A >> 24)
-			for x := x0; x < x1; x++ {
+			for x := s.X0; x < s.X1; x++ {
 				ax := int(p[x].A)
 				ax = (ax*255 + (255-ax)*a) / 255
 				p[x] = image.AlphaColor{uint8(ax)}
 			}
 		} else {
 			color := image.AlphaColor{uint8(s.A >> 24)}
-			for x := x0; x < x1; x++ {
+			for x := s.X0; x < s.X1; x++ {
 				p[x] = color
 			}
 		}
@@ -87,8 +83,6 @@ type RGBAPainter struct {
 	Image *image.RGBA
 	// The Porter-Duff composition operator.
 	Op draw.Op
-	// An offset (in pixels) to the painted spans.
-	Dx, Dy int
 	// The 16-bit color to paint the spans.
 	cr, cg, cb, ca uint32
 }
@@ -96,22 +90,20 @@ type RGBAPainter struct {
 // Paint satisfies the Painter interface by painting ss onto an image.RGBA.
 func (r *RGBAPainter) Paint(ss []Span, done bool) {
 	for _, s := range ss {
-		y := r.Dy + s.Y
+		if s.Y < 0 {
-		if y < 0 {
 			continue
 		}
-		if y >= len(r.Image.Pixel) {
+		if s.Y >= len(r.Image.Pixel) {
 			return
 		}
-		p := r.Image.Pixel[y]
+		p := r.Image.Pixel[s.Y]
-		x0, x1 := r.Dx+s.X0, r.Dx+s.X1
+		if s.X0 < 0 {
-		if x0 < 0 {
+			s.X0 = 0
-			x0 = 0
 		}
-		if x1 > len(p) {
+		if s.X1 > len(p) {
-			x1 = len(p)
+			s.X1 = len(p)
 		}
-		for x := x0; x < x1; x++ {
+		for x := s.X0; x < s.X1; x++ {
 			// This code is duplicated from drawGlyphOver in $GOROOT/src/pkg/exp/draw/draw.go.
 			// TODO(nigeltao): Factor out common code into a utility function, once the compiler
 			// can inline such function calls.

freetype/raster/raster.go

@@ -64,6 +64,8 @@ type Rasterizer struct {
 	// If false, the default behavior is to use the even-odd winding fill
 	// rule during Rasterize.
 	UseNonZeroWinding bool
+	// An offset (in pixels) to the painted spans.
+	Dx, Dy int
 
 	// The width of the Rasterizer. The height is implicit in len(cellIndex).
 	width int
@@ -501,7 +503,7 @@ func (r *Rasterizer) Rasterize(p Painter) {
 						xi1 = r.width
 					}
 					if xi0 < xi1 {
-						r.spanBuf[s] = Span{yi, xi0, xi1, alpha}
+						r.spanBuf[s] = Span{yi + r.Dy, xi0 + r.Dx, xi1 + r.Dx, alpha}
 						s++
 					}
 				}
@@ -518,7 +520,7 @@ func (r *Rasterizer) Rasterize(p Painter) {
 					xi1 = r.width
 				}
 				if xi0 < xi1 {
-					r.spanBuf[s] = Span{yi, xi0, xi1, alpha}
+					r.spanBuf[s] = Span{yi + r.Dy, xi0 + r.Dx, xi1 + r.Dx, alpha}
 					s++
 				}
 			}