Freetype-Go: take the RGBAPainter out of a RGBAContext. Instead,

a Context can now take any Painter during DrawText.

R=r
CC=rog, golang-dev
http://codereview.appspot.com/1341041

example/freetype/main.go

@@ -1,3 +1,8 @@
+// Copyright 2010 The Freetype-Go Authors. All rights reserved.
+// Use of this source code is governed by your choice of either the
+// FreeType License or the GNU General Public License version 2,
+// both of which can be found in the LICENSE file.
+
 package main
 
 import (
@@ -6,6 +11,7 @@ import (
 	"flag"
 	"fmt"
 	"freetype-go.googlecode.com/hg/freetype"
+	"freetype-go.googlecode.com/hg/freetype/raster"
 	"image"
 	"image/png"
 	"io/ioutil"
@@ -83,12 +89,13 @@ func main() {
 	}
 	rgba := image.NewRGBA(640, 480)
 	draw.Draw(rgba, draw.Rect(0, 0, rgba.Width(), rgba.Height()), bg, draw.ZP)
-	c := freetype.NewRGBAContext(rgba)
+	c := freetype.NewContext()
-	c.SetColor(fg)
 	c.SetDPI(*dpi)
 	c.SetFont(font)
 	c.SetFontSize(*size)
-	c.SetGamma(*gamma)
+	rp := raster.NewRGBAPainter(rgba)
+	rp.SetColor(fg)
+	gcp := raster.NewGammaCorrectionPainter(rp, *gamma)
 
 	// Draw the guidelines.
 	for i := 0; i < 200; i++ {
@@ -99,7 +106,7 @@ func main() {
 	// Draw the text.
 	pt := freetype.Pt(10, 10)
 	for _, s := range text {
-		err = c.DrawText(pt, s)
+		err = c.DrawText(gcp, pt, s)
 		if err != nil {
 			log.Stderr(err)
 			return

freetype/freetype.go

@@ -11,7 +11,6 @@ package freetype
 import (
 	"freetype-go.googlecode.com/hg/freetype/raster"
 	"freetype-go.googlecode.com/hg/freetype/truetype"
-	"image"
 	"os"
 )
 
@@ -28,12 +27,9 @@ func Pt(x, y int) raster.Point {
 	return raster.Point{raster.Fixed(x << 8), raster.Fixed(y << 8)}
 }
 
-// An RGBAContext holds the state for drawing text from a given font at a
+// A Context holds the state for drawing text in a given font and size.
-// given size.
+type Context struct {
-type RGBAContext struct {
 	r        *raster.Rasterizer
-	rp       *raster.RGBAPainter
-	gp       *raster.GammaCorrectionPainter
 	font     *truetype.Font
 	glyphBuf *truetype.GlyphBuf
 	fontSize float
@@ -59,30 +55,30 @@ type RGBAContext struct {
 
 // FUnitToFixed converts the given number of FUnits into fixed point units,
 // rounding to nearest.
-func (c *RGBAContext) FUnitToFixed(x int) raster.Fixed {
+func (c *Context) FUnitToFixed(x int) raster.Fixed {
 	return raster.Fixed((x*c.scale + 128) >> 8)
 }
 
 // FUnitToPixelRD converts the given number of FUnits into pixel units,
 // rounding down.
-func (c *RGBAContext) FUnitToPixelRD(x int) int {
+func (c *Context) FUnitToPixelRD(x int) int {
 	return x * c.scale >> 16
 }
 
 // FUnitToPixelRU converts the given number of FUnits into pixel units,
 // rounding up.
-func (c *RGBAContext) FUnitToPixelRU(x int) int {
+func (c *Context) FUnitToPixelRU(x int) int {
 	return (x*c.scale + 0xffff) >> 16
 }
 
 // PointToFixed converts the given number of points (as in ``a 12 point font'')
 // into fixed point units.
-func (c *RGBAContext) PointToFixed(x float) raster.Fixed {
+func (c *Context) PointToFixed(x float) raster.Fixed {
 	return raster.Fixed(x * float(c.dpi) * (256.0 / 72.0))
 }
 
 // drawContour draws the given closed contour with the given offset.
-func (c *RGBAContext) drawContour(ps []truetype.Point, dx, dy raster.Fixed) {
+func (c *Context) drawContour(ps []truetype.Point, dx, dy raster.Fixed) {
 	if len(ps) == 0 {
 		return
 	}
@@ -128,18 +124,18 @@ func (c *RGBAContext) drawContour(ps []truetype.Point, dx, dy raster.Fixed) {
 	}
 }
 
-// DrawText draws s at pt. The text is placed so that the top left of the em
+// DrawText draws s at pt using p. The text is placed so that the top left of
-// square of the first character of s is equal to pt. The majority of the
+// the em square of the first character of s is equal to pt. The majority of
-// affected pixels will be below and to the right of pt, but some may be above
+// the affected pixels will be below and to the right of pt, but some may be
-// or to the left. For example, drawing a string that starts with a 'J' in an
+// above or to the left. For example, drawing a string that starts with a 'J'
-// italic font may affect pixels to the left of pt.
+// in an italic font may affect pixels to the left of pt.
 // pt is a raster.Point and can therefore represent sub-pixel positions.
-func (c *RGBAContext) DrawText(pt raster.Point, s string) (err os.Error) {
+func (c *Context) DrawText(p raster.Painter, pt raster.Point, s string) (err os.Error) {
 	if c.font == nil {
 		return os.NewError("freetype: DrawText called with a nil font")
 	}
 	// pt.X, pt.Y, x, y, dx, dy and x0 are measured in raster.Fixed units,
-	// c.p.Dx, c.p.Dy, c.xmin and c.ymin are measured in pixels, and
+	// c.r.Dx, c.r.Dy, c.xmin and c.ymin are measured in pixels, and
 	// advance is measured in FUnits.
 	var x, y raster.Fixed
 	advance, x0 := 0, pt.X
@@ -179,7 +175,7 @@ func (c *RGBAContext) DrawText(pt raster.Point, s string) (err os.Error) {
 			c.drawContour(c.glyphBuf.Point[e0:e], x, y)
 			e0 = e
 		}
-		c.r.Rasterize(c.gp)
+		c.r.Rasterize(p)
 		// Advance the cursor.
 		advance += int(c.font.HMetric(index).AdvanceWidth)
 		prev, hasPrev = index, true
@@ -189,7 +185,7 @@ func (c *RGBAContext) DrawText(pt raster.Point, s string) (err os.Error) {
 
 // recalc recalculates scale and bounds values from the font size, screen
 // resolution and font metrics.
-func (c *RGBAContext) recalc() {
+func (c *Context) recalc() {
 	c.scale = int((c.fontSize * float(c.dpi) * 256 * 256) / (float(c.upe) * 72))
 	if c.font == nil {
 		c.xmin, c.ymin = 0, 0
@@ -203,19 +199,14 @@ func (c *RGBAContext) recalc() {
 	}
 }
 
-// SetColor sets the color to draw text.
-func (c *RGBAContext) SetColor(color image.Color) {
-	c.rp.SetColor(color)
-}
-
 // SetDPI sets the screen resolution in dots per inch.
-func (c *RGBAContext) SetDPI(dpi int) {
+func (c *Context) SetDPI(dpi int) {
 	c.dpi = dpi
 	c.recalc()
 }
 
 // SetFont sets the font used to draw text.
-func (c *RGBAContext) SetFont(font *truetype.Font) {
+func (c *Context) SetFont(font *truetype.Font) {
 	c.font = font
 	c.upe = font.UnitsPerEm()
 	if c.upe <= 0 {
@@ -225,32 +216,19 @@ func (c *RGBAContext) SetFont(font *truetype.Font) {
 }
 
 // SetFontSize sets the font size in points (as in ``a 12 point font'').
-func (c *RGBAContext) SetFontSize(fontSize float) {
+func (c *Context) SetFontSize(fontSize float) {
 	c.fontSize = fontSize
 	c.recalc()
 }
 
-// SetGamma sets the gamma correction parameter.
+// NewContext creates a new Context.
-func (c *RGBAContext) SetGamma(g float) {
+func NewContext() *Context {
-	c.gp.SetGamma(g)
+	return &Context{
-}
-
-// SetRGBA sets the image that the RGBAContext draws onto.
-func (c *RGBAContext) SetRGBA(m *image.RGBA) {
-	c.rp.Image = m
-}
-
-// NewRGBAContext creates a new RGBAContext.
-func NewRGBAContext(m *image.RGBA) *RGBAContext {
-	c := &RGBAContext{
 		r:        raster.NewRasterizer(0, 0),
-		rp:       raster.NewRGBAPainter(m),
 		glyphBuf: truetype.NewGlyphBuf(),
 		fontSize: 12,
 		dpi:      72,
 		upe:      2048,
 		scale:    (12 * 72 * 256 * 256) / (2048 * 72),
 	}
-	c.gp = raster.NewGammaCorrectionPainter(c.rp, 1.0)
-	return c
 }