moved text display to backend

backend/backendbase/base.go

@@ -18,6 +18,7 @@ type Backend interface {
 	Clear(pts [4][2]float64)
 	Fill(style *FillStyle, pts [][2]float64)
 	DrawImage(dimg Image, sx, sy, sw, sh, dx, dy, dw, dh float64, alpha float64)
+	FillImageMask(style *FillStyle, mask *image.Alpha, pts [4][2]float64)
 }
 
 // FillStyle is the color and other details on how to fill

backend/gogl/fill.go

@@ -1,6 +1,7 @@
 package goglbackend
 
 import (
+	"image"
 	"math"
 	"unsafe"
 
@@ -117,6 +118,57 @@ func (b *GoGLBackend) Fill(style *backendbase.FillStyle, pts [][2]float64) {
 	}
 }
 
+func (b *GoGLBackend) FillImageMask(style *backendbase.FillStyle, mask *image.Alpha, pts [4][2]float64) {
+	w, h := mask.Rect.Dx(), mask.Rect.Dy()
+
+	gl.ActiveTexture(gl.TEXTURE1)
+	gl.BindTexture(gl.TEXTURE_2D, b.alphaTex)
+	for y := 0; y < h; y++ {
+		off := y * mask.Stride
+		gl.TexSubImage2D(gl.TEXTURE_2D, 0, 0, int32(alphaTexSize-1-y), int32(w), 1, gl.ALPHA, gl.UNSIGNED_BYTE, gl.Ptr(&mask.Pix[off]))
+	}
+
+	// b.drawTextShadow(textOffset, w, h, x, y)
+
+	gl.StencilFunc(gl.EQUAL, 0, 0xFF)
+
+	gl.BindBuffer(gl.ARRAY_BUFFER, b.buf)
+
+	vertex, alphaTexCoord := b.useAlphaShader(style, 1)
+
+	gl.EnableVertexAttribArray(vertex)
+	gl.EnableVertexAttribArray(alphaTexCoord)
+
+	tw := float64(w) / alphaTexSize
+	th := float64(h) / alphaTexSize
+	var buf [16]float32
+	data := buf[:0]
+	for _, pt := range pts {
+		data = append(data, float32(pt[0]), float32(pt[1]))
+	}
+	data = append(data, 0, 1, 0, float32(1-th), float32(tw), float32(1-th), float32(tw), 1)
+
+	gl.BufferData(gl.ARRAY_BUFFER, len(data)*4, unsafe.Pointer(&data[0]), gl.STREAM_DRAW)
+
+	gl.VertexAttribPointer(vertex, 2, gl.FLOAT, false, 0, nil)
+	gl.VertexAttribPointer(alphaTexCoord, 2, gl.FLOAT, false, 0, gl.PtrOffset(8*4))
+	gl.DrawArrays(gl.TRIANGLE_FAN, 0, 4)
+
+	gl.DisableVertexAttribArray(vertex)
+	gl.DisableVertexAttribArray(alphaTexCoord)
+
+	gl.ActiveTexture(gl.TEXTURE1)
+	gl.BindTexture(gl.TEXTURE_2D, b.alphaTex)
+
+	gl.StencilFunc(gl.ALWAYS, 0, 0xFF)
+
+	for y := 0; y < h; y++ {
+		gl.TexSubImage2D(gl.TEXTURE_2D, 0, 0, int32(alphaTexSize-1-y), int32(w), 1, gl.ALPHA, gl.UNSIGNED_BYTE, gl.Ptr(&zeroes[0]))
+	}
+
+	gl.ActiveTexture(gl.TEXTURE0)
+}
+
 func (b *GoGLBackend) drawBlurred(blur float64) {
 	gl.BlendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA)
 

backend/gogl/gogl.go

@@ -11,6 +11,8 @@ import (
 
 const alphaTexSize = 2048
 
+var zeroes [alphaTexSize]byte
+
 type GoGLBackend struct {
 	x, y, w, h     int
 	fx, fy, fw, fh float64

text.go

@@ -5,7 +5,6 @@ import (
 	"image"
 	"image/draw"
 	"io/ioutil"
-	"unsafe"
 
 	"github.com/golang/freetype"
 	"github.com/golang/freetype/truetype"
@@ -210,52 +209,14 @@ func (cv *Canvas) FillText(str string, x, y float64) {
 		yOff = -float64(metrics.Descent) / 64
 	}
 
-	gli.ActiveTexture(gl_TEXTURE1)
+	var pts [4][2]float64
-	gli.BindTexture(gl_TEXTURE_2D, alphaTex)
+	pts[0] = cv.tf(vec{float64(textOffset.X) + x, float64(textOffset.Y) + y + yOff})
-	for y := 0; y < strHeight; y++ {
+	pts[1] = cv.tf(vec{float64(textOffset.X) + x, float64(textOffset.Y+strHeight) + y + yOff})
-		off := y * textImage.Stride
+	pts[2] = cv.tf(vec{float64(textOffset.X+strWidth) + x, float64(textOffset.Y+strHeight) + y + yOff})
-		gli.TexSubImage2D(gl_TEXTURE_2D, 0, 0, int32(alphaTexSize-1-y), int32(strWidth), 1, gl_ALPHA, gl_UNSIGNED_BYTE, gli.Ptr(&textImage.Pix[off]))
+	pts[3] = cv.tf(vec{float64(textOffset.X+strWidth) + x, float64(textOffset.Y) + y + yOff})
-	}
 
-	cv.drawTextShadow(textOffset, strWidth, strHeight, x, y)
+	stl := cv.backendFillStyle(&cv.state.fill, 1)
-
+	cv.b.FillImageMask(&stl, textImage.SubImage(image.Rect(0, 0, strWidth, strHeight)).(*image.Alpha), pts)
-	gli.StencilFunc(gl_EQUAL, 0, 0xFF)
-
-	gli.BindBuffer(gl_ARRAY_BUFFER, buf)
-
-	vertex, alphaTexCoord := cv.useAlphaShader(&cv.state.fill, 1)
-
-	gli.EnableVertexAttribArray(vertex)
-	gli.EnableVertexAttribArray(alphaTexCoord)
-
-	p0 := cv.tf(vec{float64(textOffset.X) + x, float64(textOffset.Y) + y + yOff})
-	p1 := cv.tf(vec{float64(textOffset.X) + x, float64(textOffset.Y+strHeight) + y + yOff})
-	p2 := cv.tf(vec{float64(textOffset.X+strWidth) + x, float64(textOffset.Y+strHeight) + y + yOff})
-	p3 := cv.tf(vec{float64(textOffset.X+strWidth) + x, float64(textOffset.Y) + y + yOff})
-
-	tw := float64(strWidth) / alphaTexSize
-	th := float64(strHeight) / alphaTexSize
-	data := [16]float32{float32(p0[0]), float32(p0[1]), float32(p1[0]), float32(p1[1]), float32(p2[0]), float32(p2[1]), float32(p3[0]), float32(p3[1]),
-		0, 1, 0, float32(1 - th), float32(tw), float32(1 - th), float32(tw), 1}
-	gli.BufferData(gl_ARRAY_BUFFER, len(data)*4, unsafe.Pointer(&data[0]), gl_STREAM_DRAW)
-
-	gli.VertexAttribPointer(vertex, 2, gl_FLOAT, false, 0, 0)
-	gli.VertexAttribPointer(alphaTexCoord, 2, gl_FLOAT, false, 0, 8*4)
-	gli.DrawArrays(gl_TRIANGLE_FAN, 0, 4)
-
-	gli.DisableVertexAttribArray(vertex)
-	gli.DisableVertexAttribArray(alphaTexCoord)
-
-	gli.ActiveTexture(gl_TEXTURE1)
-	gli.BindTexture(gl_TEXTURE_2D, alphaTex)
-
-	gli.StencilFunc(gl_ALWAYS, 0, 0xFF)
-
-	for y := 0; y < strHeight; y++ {
-		gli.TexSubImage2D(gl_TEXTURE_2D, 0, 0, int32(alphaTexSize-1-y), int32(strWidth), 1, gl_ALPHA, gl_UNSIGNED_BYTE, gli.Ptr(&zeroes[0]))
-	}
-
-	gli.ActiveTexture(gl_TEXTURE0)
 }
 
 // StrokeText draws the given string at the given coordinates