freetype/truetype: implement compound glyph transforms.

R=bsiegert
CC=golang-dev
https://codereview.appspot.com/14425064

freetype/truetype/glyph.go

@@ -286,7 +286,7 @@ func (g *GlyphBuf) loadCompound(recursion int32, glyf []byte) error {
 	for offset := loadOffset; ; {
 		flags := u16(glyf, offset)
 		component := Index(u16(glyf, offset+2))
-		dx, dy := int32(0), int32(0)
+		dx, dy, transform, hasTransform := int32(0), int32(0), [4]int32{}, false
 		if flags&flagArg1And2AreWords != 0 {
 			dx = int32(int16(u16(glyf, offset+4)))
 			dy = int32(int16(u16(glyf, offset+6)))
@@ -300,12 +300,38 @@ func (g *GlyphBuf) loadCompound(recursion int32, glyf []byte) error {
 			return UnsupportedError("compound glyph transform vector")
 		}
 		if flags&(flagWeHaveAScale|flagWeHaveAnXAndYScale|flagWeHaveATwoByTwo) != 0 {
-			return UnsupportedError("compound glyph scale/transform")
+			hasTransform = true
+			switch {
+			case flags&flagWeHaveAScale != 0:
+				transform[0] = int32(int16(u16(glyf, offset+0)))
+				transform[3] = transform[0]
+				offset += 2
+			case flags&flagWeHaveAnXAndYScale != 0:
+				transform[0] = int32(int16(u16(glyf, offset+0)))
+				transform[3] = int32(int16(u16(glyf, offset+2)))
+				offset += 4
+			case flags&flagWeHaveATwoByTwo != 0:
+				transform[0] = int32(int16(u16(glyf, offset+0)))
+				transform[1] = int32(int16(u16(glyf, offset+2)))
+				transform[2] = int32(int16(u16(glyf, offset+4)))
+				transform[3] = int32(int16(u16(glyf, offset+6)))
+				offset += 8
+			}
 		}
 		np0 := len(g.Point)
 		if err := g.load(recursion+1, component, flags&flagUseMyMetrics != 0); err != nil {
 			return err
 		}
+		if hasTransform {
+			for i := np0; i < len(g.Point); i++ {
+				p := &g.Point[i]
+				newX := int32((int64(p.X)*int64(transform[0])+1<<13)>>14) +
+					int32((int64(p.Y)*int64(transform[2])+1<<13)>>14)
+				newY := int32((int64(p.X)*int64(transform[1])+1<<13)>>14) +
+					int32((int64(p.Y)*int64(transform[3])+1<<13)>>14)
+				p.X, p.Y = newX, newY
+			}
+		}
 		dx = g.font.scale(g.scale * dx)
 		dy = g.font.scale(g.scale * dy)
 		if flags&flagRoundXYToGrid != 0 {

freetype/truetype/truetype_test.go

@@ -263,7 +263,6 @@ var scalingTestCases = []struct {
 // TODO: also test bounding boxes, not just points.
 
 func testScaling(t *testing.T, hinter *Hinter) {
-loop:
 	for _, tc := range scalingTestCases {
 		font, testdataIsOptional, err := parseTestdataFont(tc.name)
 		if err != nil {
@@ -272,7 +271,7 @@ loop:
 			} else {
 				t.Error(err)
 			}
-			continue loop
+			continue
 		}
 		hinting := "sans"
 		if hinter != nil {
@@ -282,7 +281,7 @@ loop:
 			"../../testdata/%s-%dpt-%s-hinting.txt", tc.name, tc.size, hinting))
 		if err != nil {
 			t.Errorf("%s: Open: %v", tc.name, err)
-			continue loop
+			continue
 		}
 		defer f.Close()
 
@@ -293,7 +292,7 @@ loop:
 		}
 		if err := scanner.Err(); err != nil && err != io.EOF {
 			t.Errorf("%s: Scanner: %v", tc.name, err)
-			continue loop
+			continue
 		}
 
 		glyphBuf := NewGlyphBuf()
@@ -305,12 +304,8 @@ loop:
 			}
 
 			if err = glyphBuf.Load(font, tc.size*64, Index(i), hinter); err != nil {
-				if ue, ok := err.(UnsupportedError); ok && ue == "compound glyph scale/transform" {
-					// TODO: implement compound glyph scale/transform.
-					continue loop
-				}
 				t.Errorf("%s: glyph #%d: Load: %v", tc.name, i, err)
-				continue loop
+				continue
 			}
 			got := glyphBuf.Point
 			for i := range got {