freetype/raster: fix some style nits.

This code dates from before Go 1.0.

LGTM=crawshaw
R=crawshaw
CC=golang-codereviews
https://codereview.appspot.com/206860043

freetype/raster/geom.go

@@ -101,7 +101,7 @@ func (p Point) Len() Fix32 {
 func (p Point) Norm(length Fix32) Point {
 	d := p.Len()
 	if d == 0 {
-		return Point{0, 0}
+		return Point{}
 	}
 	s, t := int64(length), int64(d)
 	x := int64(p.X) * s / t
@@ -204,74 +204,34 @@ func (p Path) String() string {
 	return s
 }
 
-// grow adds n elements to p.
-func (p *Path) grow(n int) {
-	n += len(*p)
-	if n > cap(*p) {
-		old := *p
-		*p = make([]Fix32, n, 2*n+8)
-		copy(*p, old)
-		return
-	}
-	*p = (*p)[0:n]
-}
-
 // Clear cancels any previous calls to p.Start or p.AddXxx.
 func (p *Path) Clear() {
-	*p = (*p)[0:0]
+	*p = (*p)[:0]
 }
 
 // Start starts a new curve at the given point.
 func (p *Path) Start(a Point) {
-	n := len(*p)
-	p.grow(4)
-	(*p)[n] = 0
-	(*p)[n+1] = a.X
-	(*p)[n+2] = a.Y
-	(*p)[n+3] = 0
+	*p = append(*p, 0, a.X, a.Y, 0)
 }
 
 // Add1 adds a linear segment to the current curve.
 func (p *Path) Add1(b Point) {
-	n := len(*p)
-	p.grow(4)
-	(*p)[n] = 1
-	(*p)[n+1] = b.X
-	(*p)[n+2] = b.Y
-	(*p)[n+3] = 1
+	*p = append(*p, 1, b.X, b.Y, 1)
 }
 
 // Add2 adds a quadratic segment to the current curve.
 func (p *Path) Add2(b, c Point) {
-	n := len(*p)
-	p.grow(6)
-	(*p)[n] = 2
-	(*p)[n+1] = b.X
-	(*p)[n+2] = b.Y
-	(*p)[n+3] = c.X
-	(*p)[n+4] = c.Y
-	(*p)[n+5] = 2
+	*p = append(*p, 2, b.X, b.Y, c.X, c.Y, 2)
 }
 
 // Add3 adds a cubic segment to the current curve.
 func (p *Path) Add3(b, c, d Point) {
-	n := len(*p)
-	p.grow(8)
-	(*p)[n] = 3
-	(*p)[n+1] = b.X
-	(*p)[n+2] = b.Y
-	(*p)[n+3] = c.X
-	(*p)[n+4] = c.Y
-	(*p)[n+5] = d.X
-	(*p)[n+6] = d.Y
-	(*p)[n+7] = 3
+	*p = append(*p, 3, b.X, b.Y, c.X, c.Y, d.X, d.Y, 3)
 }
 
 // AddPath adds the Path q to p.
 func (p *Path) AddPath(q Path) {
-	n, m := len(*p), len(q)
-	p.grow(m)
-	copy((*p)[n:n+m], q)
+	*p = append(*p, q...)
 }
 
 // AddStroke adds a stroked Path.

freetype/raster/paint.go

@@ -208,11 +208,11 @@ func (m *MonochromePainter) Paint(ss []Span, done bool) {
 		if j < len(ss) {
 			ss[j] = finalSpan
 			j++
-			m.Painter.Paint(ss[0:j], true)
+			m.Painter.Paint(ss[:j], true)
 		} else if j == len(ss) {
 			m.Painter.Paint(ss, false)
 			if cap(ss) > 0 {
-				ss = ss[0:1]
+				ss = ss[:1]
 			} else {
 				ss = make([]Span, 1)
 			}
@@ -224,7 +224,7 @@ func (m *MonochromePainter) Paint(ss []Span, done bool) {
 		// Reset the accumulator, so that this Painter can be re-used.
 		m.y, m.x0, m.x1 = 0, 0, 0
 	} else {
-		m.Painter.Paint(ss[0:j], false)
+		m.Painter.Paint(ss[:j], false)
 	}
 }
 
@@ -253,11 +253,11 @@ func (g *GammaCorrectionPainter) Paint(ss []Span, done bool) {
 			M = 0x1010101 // 255*M == 1<<32-1
 			N = 0x8080    // N = M>>9, and N < 1<<16-1
 		)
-		for i, _ := range ss {
-			if ss[i].A == 0 || ss[i].A == 1<<32-1 {
+		for i, s := range ss {
+			if s.A == 0 || s.A == 1<<32-1 {
 				continue
 			}
-			p, q := ss[i].A/M, (ss[i].A%M)>>9
+			p, q := s.A/M, (s.A%M)>>9
 			// The resultant alpha is a linear interpolation of g.a[p] and g.a[p+1].
 			a := uint32(g.a[p])*(N-q) + uint32(g.a[p+1])*q
 			a = (a + N/2) / N

freetype/raster/raster.go

@@ -327,8 +327,8 @@ func (r *Rasterizer) Add2(b, c Point) {
 		s := sStack[i]
 		p := pStack[2*i:]
 		if s > 0 {
-			// Split the quadratic curve p[0:3] into an equivalent set of two shorter curves:
-			// p[0:3] and p[2:5]. The new p[4] is the old p[2], and p[0] is unchanged.
+			// Split the quadratic curve p[:3] into an equivalent set of two shorter curves:
+			// p[:3] and p[2:5]. The new p[4] is the old p[2], and p[0] is unchanged.
 			mx := p[1].X
 			p[4].X = p[2].X
 			p[3].X = (p[4].X + mx) / 2
@@ -385,8 +385,8 @@ func (r *Rasterizer) Add3(b, c, d Point) {
 		s := sStack[i]
 		p := pStack[3*i:]
 		if s > 0 {
-			// Split the cubic curve p[0:4] into an equivalent set of two shorter curves:
-			// p[0:4] and p[3:7]. The new p[6] is the old p[3], and p[0] is unchanged.
+			// Split the cubic curve p[:4] into an equivalent set of two shorter curves:
+			// p[:4] and p[3:7]. The new p[6] is the old p[3], and p[0] is unchanged.
 			m01x := (p[0].X + p[1].X) / 2
 			m12x := (p[1].X + p[2].X) / 2
 			m23x := (p[2].X + p[3].X) / 2
@@ -519,22 +519,22 @@ func (r *Rasterizer) Rasterize(p Painter) {
 				}
 			}
 			if s > len(r.spanBuf)-2 {
-				p.Paint(r.spanBuf[0:s], false)
+				p.Paint(r.spanBuf[:s], false)
 				s = 0
 			}
 		}
 	}
-	p.Paint(r.spanBuf[0:s], true)
+	p.Paint(r.spanBuf[:s], true)
 }
 
 // Clear cancels any previous calls to r.Start or r.AddXxx.
 func (r *Rasterizer) Clear() {
-	r.a = Point{0, 0}
+	r.a = Point{}
 	r.xi = 0
 	r.yi = 0
 	r.area = 0
 	r.cover = 0
-	r.cell = r.cell[0:0]
+	r.cell = r.cell[:0]
 	for i := 0; i < len(r.cellIndex); i++ {
 		r.cellIndex[i] = -1
 	}
@@ -562,11 +562,11 @@ func (r *Rasterizer) SetBounds(width, height int) {
 	r.width = width
 	r.splitScale2 = ss2
 	r.splitScale3 = ss3
-	r.cell = r.cellBuf[0:0]
+	r.cell = r.cellBuf[:0]
 	if height > len(r.cellIndexBuf) {
 		r.cellIndex = make([]int, height)
 	} else {
-		r.cellIndex = r.cellIndexBuf[0:height]
+		r.cellIndex = r.cellIndexBuf[:height]
 	}
 	r.Clear()
 }

freetype/raster/stroke.go

@@ -401,7 +401,7 @@ func (k *stroker) stroke(q Path) {
 	// The left-hand-side path is added immediately to k.p; the right-hand-side
 	// path is accumulated in k.r. Once we've finished adding the LHS to k.p,
 	// we add the RHS in reverse order.
-	k.r = Path(make([]Fix32, 0, len(q)))
+	k.r = make(Path, 0, len(q))
 	k.a = Point{q[1], q[2]}
 	for i := 4; i < len(q); {
 		switch q[i] {