ui: build paths as ops

Instead of allocating and constructing a clip path, store path data
directly in op lists. Use separate op lists for cached text layout
paths.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/app/internal/gpu/gpu.go

@@ -3,6 +3,7 @@
 package gpu
 
 import (
+	"encoding/binary"
 	"fmt"
 	"image"
 	"image/color"
@@ -16,7 +17,6 @@ import (
 	gdraw "gioui.org/ui/draw"
 	"gioui.org/ui/f32"
 	"gioui.org/ui/internal/ops"
-	"gioui.org/ui/internal/path"
 	"golang.org/x/image/draw"
 )
 
@@ -87,10 +87,11 @@ type pathOp struct {
 	off f32.Point
 	// clip is the union of all
 	// later clip rectangles.
-	clip   image.Rectangle
+	clip      image.Rectangle
-	path   *path.Path
+	pathKey   ui.OpKey
-	parent *pathOp
+	pathVerts []byte
-	place  placement
+	parent    *pathOp
+	place     placement
 }
 
 type imageOp struct {
@@ -114,6 +115,31 @@ type material struct {
 	uvOffset f32.Point
 }
 
+// opClip structure must match opClip in package ui/draw.
+type opClip struct {
+	bounds f32.Rectangle
+}
+
+func (op *opClip) decode(data []byte) {
+	if ops.OpType(data[0]) != ops.TypeClip {
+		panic("invalid op")
+	}
+	bo := binary.LittleEndian
+	r := f32.Rectangle{
+		Min: f32.Point{
+			X: math.Float32frombits(bo.Uint32(data[1:])),
+			Y: math.Float32frombits(bo.Uint32(data[5:])),
+		},
+		Max: f32.Point{
+			X: math.Float32frombits(bo.Uint32(data[9:])),
+			Y: math.Float32frombits(bo.Uint32(data[13:])),
+		},
+	}
+	*op = opClip{
+		bounds: r,
+	}
+}
+
 type clipType uint8
 
 type resourceCache struct {
@@ -485,10 +511,10 @@ func (r *renderer) stencilClips(cache *resourceCache, ops []*pathOp) {
 			bindFramebuffer(r.ctx, f.fbo)
 			r.ctx.Clear(gl.COLOR_BUFFER_BIT)
 		}
-		data, exists := cache.get(p.path)
+		data, exists := cache.get(p.pathKey)
 		if !exists {
-			data = buildPath(r.ctx, p.path)
+			data = buildPath(r.ctx, p.pathVerts)
-			cache.put(p.path, data)
+			cache.put(p.pathKey, data)
 		}
 		r.pather.stencilPath(p.clip, p.off, p.place.Pos, data.(*pathData))
 	}
@@ -528,7 +554,7 @@ func (r *renderer) intersectPath(p *pathOp, clip image.Rectangle) {
 	if p.parent != nil {
 		r.intersectPath(p.parent, clip)
 	}
-	if p.path == nil {
+	if len(p.pathVerts) == 0 {
 		return
 	}
 	o := p.place.Pos.Add(clip.Min).Sub(p.clip.Min)
@@ -550,7 +576,7 @@ func (r *renderer) packIntersections(ops []imageOp) {
 		var npaths int
 		var onePath *pathOp
 		for p := img.path; p != nil; p = p.parent {
-			if p.path != nil {
+			if len(p.pathVerts) > 0 {
 				onePath = p
 				npaths++
 			}
@@ -665,27 +691,27 @@ func (d *drawOps) newPathOp() *pathOp {
 }
 
 func (d *drawOps) collectOps(r *ui.OpsReader, state drawState) int {
+	var aux []byte
+	var auxKey ui.OpKey
 loop:
 	for {
-		data, refs, ok := r.Decode()
+		encOp, ok := r.Decode()
 		if !ok {
 			break
 		}
-		switch ops.OpType(data[0]) {
+		switch ops.OpType(encOp.Data[0]) {
 		case ops.TypeTransform:
 			var op ui.OpTransform
-			op.Decode(data)
+			op.Decode(encOp.Data)
 			state.t = state.t.Mul(op.Transform)
+		case ops.TypeAux:
+			aux = encOp.Data[ops.TypeAuxLen:]
+			auxKey = encOp.Key
 		case ops.TypeClip:
-			var op gdraw.OpClip
+			var op opClip
-			op.Decode(data, refs)
+			op.decode(encOp.Data)
-			if op.Path == nil {
-				state.clip = f32.Rectangle{}
-				continue
-			}
-			data := op.Path.Data().(*path.Path)
 			off := state.t.Transform(f32.Point{})
-			state.clip = state.clip.Intersect(data.Bounds.Add(off))
+			state.clip = state.clip.Intersect(op.bounds.Add(off))
 			if state.clip.Empty() {
 				continue
 			}
@@ -695,24 +721,27 @@ loop:
 				off:    off,
 			}
 			state.cpath = npath
-			if len(data.Vertices) > 0 {
+			if len(aux) > 0 {
 				state.rect = false
-				state.cpath.path = data
+				state.cpath.pathKey = auxKey
+				state.cpath.pathVerts = aux
 				d.pathOps = append(d.pathOps, state.cpath)
 			}
+			aux = nil
+			auxKey = ui.OpKey{}
 		case ops.TypeColor:
 			var op gdraw.OpColor
-			op.Decode(data, refs)
+			op.Decode(encOp.Data, encOp.Refs)
 			state.img = nil
 			state.color = op.Col
 		case ops.TypeImage:
 			var op gdraw.OpImage
-			op.Decode(data, refs)
+			op.Decode(encOp.Data, encOp.Refs)
 			state.img = op.Img
 			state.imgRect = op.Rect
 		case ops.TypeDraw:
 			var op gdraw.OpDraw
-			op.Decode(data, refs)
+			op.Decode(encOp.Data, encOp.Refs)
 			off := state.t.Transform(f32.Point{})
 			clip := state.clip.Intersect(op.Rect.Add(off))
 			if clip.Empty() {

ui/app/internal/gpu/path.go

@@ -221,12 +221,12 @@ func (c *coverer) release() {
 	}
 }
 
-func buildPath(ctx *context, p *path.Path) *pathData {
+func buildPath(ctx *context, p []byte) *pathData {
 	buf := ctx.CreateBuffer()
 	ctx.BindBuffer(gl.ARRAY_BUFFER, buf)
-	ctx.BufferData(gl.ARRAY_BUFFER, gl.BytesView(p.Vertices), gl.STATIC_DRAW)
+	ctx.BufferData(gl.ARRAY_BUFFER, p, gl.STATIC_DRAW)
 	return &pathData{
-		ncurves: len(p.Vertices),
+		ncurves: len(p) / path.VertStride,
 		data:    buf,
 	}
 }

ui/app/window.go

@@ -156,14 +156,14 @@ func collectRedraws(r *ui.OpsReader) (time.Time, bool) {
 	var t time.Time
 	redraw := false
 	for {
-		data, _, ok := r.Decode()
+		encOp, ok := r.Decode()
 		if !ok {
 			break
 		}
-		switch ops.OpType(data[0]) {
+		switch ops.OpType(encOp.Data[0]) {
 		case ops.TypeRedraw:
 			var op ui.OpRedraw
-			op.Decode(data)
+			op.Decode(encOp.Data)
 			if !redraw || op.At.Before(t) {
 				redraw = true
 				t = op.At

ui/draw/draw.go

@@ -11,7 +11,6 @@ import (
 	"gioui.org/ui"
 	"gioui.org/ui/f32"
 	"gioui.org/ui/internal/ops"
-	"gioui.org/ui/internal/path"
 )
 
 type OpImage struct {
@@ -114,14 +113,10 @@ func (d *OpDraw) Decode(data []byte, refs []interface{}) {
 	}
 }
 
-// RectPath constructs a path corresponding to
+// RectClip append a clip op corresponding to
 // a pixel aligned rectangular area.
-func RectPath(r image.Rectangle) *Path {
+func RectClip(ops *ui.Ops, r image.Rectangle) {
-	return &Path{
+	opClip{bounds: toRectF(r)}.Add(ops)
-		data: &path.Path{
-			Bounds: toRectF(r),
-		},
-	}
 }
 
 func itof(i int) float32 {

ui/draw/path.go

@@ -3,7 +3,9 @@
 package draw
 
 import (
+	"encoding/binary"
 	"math"
+	"unsafe"
 
 	"gioui.org/ui"
 	"gioui.org/ui/f32"
@@ -11,81 +13,71 @@ import (
 	"gioui.org/ui/internal/path"
 )
 
-type OpClip struct {
-	Path *Path
-}
-
-type Path struct {
-	data *path.Path
-}
-
 type PathBuilder struct {
-	verts     []path.Vertex
 	firstVert int
+	nverts    int
 	maxy      float32
 	pen       f32.Point
 	bounds    f32.Rectangle
 	hasBounds bool
 }
 
-// Data is for internal use only.
+// opClip structure must match opClip in package ui/internal/gpu.
-func (p *Path) Data() interface{} {
+type opClip struct {
-	return p.data
+	bounds f32.Rectangle
 }
 
-func (c OpClip) Add(o *ui.Ops) {
+func (p opClip) Add(o *ui.Ops) {
 	data := make([]byte, ops.TypeClipLen)
 	data[0] = byte(ops.TypeClip)
-	o.Write(data, []interface{}{c.Path})
+	bo := binary.LittleEndian
-}
+	bo.PutUint32(data[1:], math.Float32bits(p.bounds.Min.X))
-
+	bo.PutUint32(data[5:], math.Float32bits(p.bounds.Min.Y))
-func (c *OpClip) Decode(d []byte, refs []interface{}) {
+	bo.PutUint32(data[9:], math.Float32bits(p.bounds.Max.X))
-	if ops.OpType(d[0]) != ops.TypeClip {
+	bo.PutUint32(data[13:], math.Float32bits(p.bounds.Max.Y))
-		panic("invalid op")
+	o.Write(data, nil)
-	}
-	*c = OpClip{
-		Path: refs[0].(*Path),
-	}
 }
 
 // MoveTo moves the pen to the given position.
-func (p *PathBuilder) Move(to f32.Point) {
+func (p *PathBuilder) Move(ops *ui.Ops, to f32.Point) {
-	p.end()
+	p.end(ops)
 	to = to.Add(p.pen)
 	p.maxy = to.Y
 	p.pen = to
 }
 
 // end completes the current contour.
-func (p *PathBuilder) end() {
+func (p *PathBuilder) end(ops *ui.Ops) {
-	// Fill in maximal Y coordinates of the NW and NE corners
+	aux := ops.Aux()
-	// and offset their curve coordinates.
+	bo := binary.LittleEndian
-	for i := p.firstVert; i < len(p.verts); i++ {
+	// Fill in maximal Y coordinates of the NW and NE corners.
-		p.verts[i].MaxY = p.maxy
+	for i := p.firstVert; i < p.nverts; i++ {
+		off := path.VertStride*i + int(unsafe.Offsetof(((*path.Vertex)(nil)).MaxY))
+		bo.PutUint32(aux[off:], math.Float32bits(p.maxy))
 	}
-	p.firstVert = len(p.verts)
+	p.firstVert = p.nverts
 }
 
 // Line records a line from the pen to end.
-func (p *PathBuilder) Line(to f32.Point) {
+func (p *PathBuilder) Line(ops *ui.Ops, to f32.Point) {
 	to = to.Add(p.pen)
-	p.lineTo(to)
+	p.lineTo(ops, to)
 }
 
-func (p *PathBuilder) lineTo(to f32.Point) {
+func (p *PathBuilder) lineTo(ops *ui.Ops, to f32.Point) {
 	// Model lines as degenerate quadratic beziers.
-	p.quadTo(to.Add(p.pen).Mul(.5), to)
+	p.quadTo(ops, to.Add(p.pen).Mul(.5), to)
 }
 
 // Quad records a quadratic bezier from the pen to end
 // with the control point ctrl.
-func (p *PathBuilder) Quad(ctrl, to f32.Point) {
+func (p *PathBuilder) Quad(ops *ui.Ops, ctrl, to f32.Point) {
 	ctrl = ctrl.Add(p.pen)
 	to = to.Add(p.pen)
-	p.quadTo(ctrl, to)
+	p.quadTo(ops, ctrl, to)
 }
 
-func (p *PathBuilder) quadTo(ctrl, to f32.Point) {
+func (p *PathBuilder) quadTo(ops *ui.Ops, ctrl, to f32.Point) {
 	// Zero width curves don't contribute to stenciling.
 	if p.pen.X == to.X && p.pen.X == ctrl.X {
 		p.pen = to
@@ -112,8 +104,8 @@ func (p *PathBuilder) quadTo(ctrl, to f32.Point) {
 		ctrl0 := p.pen.Mul(1 - t).Add(ctrl.Mul(t))
 		ctrl1 := ctrl.Mul(1 - t).Add(to.Mul(t))
 		mid := ctrl0.Mul(1 - t).Add(ctrl1.Mul(t))
-		p.simpleQuadTo(ctrl0, mid)
+		p.simpleQuadTo(ops, ctrl0, mid)
-		p.simpleQuadTo(ctrl1, to)
+		p.simpleQuadTo(ops, ctrl1, to)
 		if mid.X > bounds.Max.X {
 			bounds.Max.X = mid.X
 		}
@@ -121,7 +113,7 @@ func (p *PathBuilder) quadTo(ctrl, to f32.Point) {
 			bounds.Min.X = mid.X
 		}
 	} else {
-		p.simpleQuadTo(ctrl, to)
+		p.simpleQuadTo(ops, ctrl, to)
 	}
 	// Find the y extremum, if any.
 	d = v0.Y - v1.Y
@@ -140,7 +132,7 @@ func (p *PathBuilder) quadTo(ctrl, to f32.Point) {
 
 // Cube records a cubic bezier from the pen through
 // two control points ending in to.
-func (p *PathBuilder) Cube(ctrl0, ctrl1, to f32.Point) {
+func (p *PathBuilder) Cube(ops *ui.Ops, ctrl0, ctrl1, to f32.Point) {
 	ctrl0 = ctrl0.Add(p.pen)
 	ctrl1 = ctrl1.Add(p.pen)
 	to = to.Add(p.pen)
@@ -154,12 +146,12 @@ func (p *PathBuilder) Cube(ctrl0, ctrl1, to f32.Point) {
 	if h := hull.Dy(); h > l {
 		l = h
 	}
-	p.approxCubeTo(0, l*0.001, ctrl0, ctrl1, to)
+	p.approxCubeTo(ops, 0, l*0.001, ctrl0, ctrl1, to)
 }
 
 // approxCube approximates a cubic beziér by a series of quadratic
 // curves.
-func (p *PathBuilder) approxCubeTo(splits int, maxDist float32, ctrl0, ctrl1, to f32.Point) int {
+func (p *PathBuilder) approxCubeTo(ops *ui.Ops, splits int, maxDist float32, ctrl0, ctrl1, to f32.Point) int {
 	// The idea is from
 	// https://caffeineowl.com/graphics/2d/vectorial/cubic2quad01.html
 	// where a quadratic approximates a cubic by eliminating its t³ term
@@ -171,7 +163,7 @@ func (p *PathBuilder) approxCubeTo(splits int, maxDist float32, ctrl0, ctrl1, to
 	//
 	// C1 = (3ctrl0 - pen)/2
 	//
-	// The reverse cubic that is anchored at the end point has the polynomial
+	// The reverse cubic anchored at the end point has the polynomial
 	//
 	// P'(t) = to + 3t(ctrl1 - to) + 3t²(ctrl0 - 2ctrl1 + to) + t³(pen - 3ctrl0 + 3ctrl1 - to)
 	//
@@ -187,7 +179,7 @@ func (p *PathBuilder) approxCubeTo(splits int, maxDist float32, ctrl0, ctrl1, to
 	c := ctrl0.Mul(3).Sub(p.pen).Add(ctrl1.Mul(3)).Sub(to).Mul(1.0 / 4.0)
 	const maxSplits = 32
 	if splits >= maxSplits {
-		p.quadTo(c, to)
+		p.quadTo(ops, c, to)
 		return splits
 	}
 	// The maximum distance between the cubic P and its approximation Q given t
@@ -199,7 +191,7 @@ func (p *PathBuilder) approxCubeTo(splits int, maxDist float32, ctrl0, ctrl1, to
 	v := to.Sub(ctrl1.Mul(3)).Add(ctrl0.Mul(3)).Sub(p.pen)
 	d2 := (v.X*v.X + v.Y*v.Y) * 3 / (36 * 36)
 	if d2 <= maxDist*maxDist {
-		p.quadTo(c, to)
+		p.quadTo(ops, c, to)
 		return splits
 	}
 	// De Casteljau split the curve and approximate the halves.
@@ -211,8 +203,8 @@ func (p *PathBuilder) approxCubeTo(splits int, maxDist float32, ctrl0, ctrl1, to
 	c12 := c1.Add(c2.Sub(c1).Mul(t))
 	c0112 := c01.Add(c12.Sub(c01).Mul(t))
 	splits++
-	splits = p.approxCubeTo(splits, maxDist, c0, c01, c0112)
+	splits = p.approxCubeTo(ops, splits, maxDist, c0, c01, c0112)
-	splits = p.approxCubeTo(splits, maxDist, c12, c2, to)
+	splits = p.approxCubeTo(ops, splits, maxDist, c12, c2, to)
 	return splits
 }
 
@@ -228,8 +220,9 @@ func (p *PathBuilder) expand(b f32.Rectangle) {
 	p.bounds = p.bounds.Union(b)
 }
 
-func (p *PathBuilder) vertex(cornerx, cornery int16, ctrl, to f32.Point) {
+func (p *PathBuilder) vertex(o *ui.Ops, cornerx, cornery int16, ctrl, to f32.Point) {
-	p.verts = append(p.verts, path.Vertex{
+	p.nverts++
+	v := path.Vertex{
 		CornerX: cornerx,
 		CornerY: cornery,
 		FromX:   p.pen.X,
@@ -238,10 +231,25 @@ func (p *PathBuilder) vertex(cornerx, cornery int16, ctrl, to f32.Point) {
 		CtrlY:   ctrl.Y,
 		ToX:     to.X,
 		ToY:     to.Y,
-	})
+	}
+	data := make([]byte, path.VertStride+1)
+	data[0] = byte(ops.TypeAux)
+	bo := binary.LittleEndian
+	data[1] = byte(uint16(v.CornerX))
+	data[2] = byte(uint16(v.CornerX) >> 8)
+	data[3] = byte(uint16(v.CornerY))
+	data[4] = byte(uint16(v.CornerY) >> 8)
+	bo.PutUint32(data[5:], math.Float32bits(v.MaxY))
+	bo.PutUint32(data[9:], math.Float32bits(v.FromX))
+	bo.PutUint32(data[13:], math.Float32bits(v.FromY))
+	bo.PutUint32(data[17:], math.Float32bits(v.CtrlX))
+	bo.PutUint32(data[21:], math.Float32bits(v.CtrlY))
+	bo.PutUint32(data[25:], math.Float32bits(v.ToX))
+	bo.PutUint32(data[29:], math.Float32bits(v.ToY))
+	o.Write(data, nil)
 }
 
-func (p *PathBuilder) simpleQuadTo(ctrl, to f32.Point) {
+func (p *PathBuilder) simpleQuadTo(ops *ui.Ops, ctrl, to f32.Point) {
 	if p.pen.Y > p.maxy {
 		p.maxy = p.pen.Y
 	}
@@ -252,25 +260,19 @@ func (p *PathBuilder) simpleQuadTo(ctrl, to f32.Point) {
 		p.maxy = to.Y
 	}
 	// NW.
-	p.vertex(-1, 1, ctrl, to)
+	p.vertex(ops, -1, 1, ctrl, to)
 	// NE.
-	p.vertex(1, 1, ctrl, to)
+	p.vertex(ops, 1, 1, ctrl, to)
 	// SW.
-	p.vertex(-1, -1, ctrl, to)
+	p.vertex(ops, -1, -1, ctrl, to)
 	// SE.
-	p.vertex(1, -1, ctrl, to)
+	p.vertex(ops, 1, -1, ctrl, to)
 	p.pen = to
 }
 
-func (p *PathBuilder) Path() *Path {
+func (p *PathBuilder) End(ops *ui.Ops) {
-	p.end()
+	p.end(ops)
-	data := &Path{
+	opClip{
-		data: &path.Path{
+		bounds: p.bounds,
-			Bounds: p.bounds,
+	}.Add(ops)
-		},
-	}
-	if !p.bounds.Empty() {
-		data.data.Vertices = p.verts
-	}
-	return data
 }

ui/internal/ops/ops.go

@@ -11,7 +11,6 @@ const (
 	TypeTransform
 	TypeLayer
 	TypeRedraw
-	TypeClip
 	TypeImage
 	TypeDraw
 	TypeColor
@@ -20,6 +19,8 @@ const (
 	TypeHideInput
 	TypePush
 	TypePop
+	TypeAux
+	TypeClip
 )
 
 const (
@@ -28,7 +29,6 @@ const (
 	TypeTransformLen      = 1 + 4*2
 	TypeLayerLen          = 1
 	TypeRedrawLen         = 1 + 8
-	TypeClipLen           = 1
 	TypeImageLen          = 1 + 4*4
 	TypeDrawLen           = 1 + 4*4
 	TypeColorLen          = 1 + 4
@@ -37,13 +37,14 @@ const (
 	TypeHideInputLen      = 1
 	TypePushLen           = 1
 	TypePopLen            = 1
+	TypeAuxLen            = 1 + 4
+	TypeClipLen           = 1 + 4*4
 
 	TypeBlockDefRefs       = 0
 	TypeBlockRefs          = 1
 	TypeTransformRefs      = 0
 	TypeLayerRefs          = 0
 	TypeRedrawRefs         = 0
-	TypeClipRefs           = 1
 	TypeImageRefs          = 1
 	TypeDrawRefs           = 0
 	TypeColorRefs          = 0
@@ -52,4 +53,6 @@ const (
 	TypeHideInputRefs      = 0
 	TypePushRefs           = 0
 	TypePopRefs            = 0
+	TypeAuxRefs            = 0
+	TypeClipRefs           = 0
 )

ui/internal/path/path.go

@@ -4,15 +4,8 @@ package path
 
 import (
 	"unsafe"
-
-	"gioui.org/ui/f32"
 )
 
-type Path struct {
-	Vertices []Vertex
-	Bounds   f32.Rectangle
-}
-
 // The vertex data suitable for passing to vertex programs.
 type Vertex struct {
 	CornerX, CornerY int16

ui/key/queue.go

@@ -80,14 +80,14 @@ func resolveFocus(r *ui.OpsReader, focus Key) (Key, listenerPriority, bool) {
 	var hide bool
 loop:
 	for {
-		data, refs, ok := r.Decode()
+		encOp, ok := r.Decode()
 		if !ok {
 			break
 		}
-		switch ops.OpType(data[0]) {
+		switch ops.OpType(encOp.Data[0]) {
 		case ops.TypeKeyHandler:
 			var op OpHandler
-			op.Decode(data, refs)
+			op.Decode(encOp.Data, encOp.Refs)
 			var newPri listenerPriority
 			switch {
 			case op.Focus:

ui/layout/list.go

@@ -179,7 +179,7 @@ func (l *List) Layout(ops *ui.Ops) Dimens {
 			Max: axisPoint(l.Axis, max, ui.Inf),
 		}
 		ui.OpPush{}.Add(ops)
-		draw.OpClip{Path: draw.RectPath(r)}.Add(ops)
+		draw.RectClip(ops, r)
 		ui.OpTransform{
 			Transform: ui.Offset(toPointF(axisPoint(l.Axis, pos, cross))),
 		}.Add(ops)

ui/measure/measure.go

@@ -30,7 +30,7 @@ type cachedLayout struct {
 
 type cachedPath struct {
 	active bool
-	path   *draw.Path
+	path   ui.OpBlock
 }
 
 type layoutKey struct {
@@ -121,7 +121,7 @@ func (f *textFace) Layout(str string, singleLine bool, maxWidth int) *text.Layou
 	return l
 }
 
-func (f *textFace) Path(str text.String) *draw.Path {
+func (f *textFace) Path(str text.String) ui.OpBlock {
 	ppem := fixed.Int26_6(f.faces.Cfg.Val(f.size)*64 + .5)
 	pk := pathKey{
 		f:    f.font.Font,
@@ -229,11 +229,13 @@ func layoutText(ppem fixed.Int26_6, str string, f *opentype, singleLine bool, ma
 	return &text.Layout{Lines: lines}
 }
 
-func textPath(ppem fixed.Int26_6, f *opentype, str text.String) *draw.Path {
+func textPath(ppem fixed.Int26_6, f *opentype, str text.String) ui.OpBlock {
 	var lastPos f32.Point
 	var builder draw.PathBuilder
+	ops := new(ui.Ops)
 	var x fixed.Int26_6
 	var advIdx int
+	ops.Begin()
 	for _, r := range str.String {
 		if !unicode.IsSpace(r) {
 			segs, ok := f.LoadGlyph(ppem, r)
@@ -244,7 +246,7 @@ func textPath(ppem fixed.Int26_6, f *opentype, str text.String) *draw.Path {
 			pos := f32.Point{
 				X: float32(x) / 64,
 			}
-			builder.Move(pos.Sub(lastPos))
+			builder.Move(ops, pos.Sub(lastPos))
 			lastPos = pos
 			var lastArg f32.Point
 			// Convert sfnt.Segments to relative segments.
@@ -269,13 +271,13 @@ func textPath(ppem fixed.Int26_6, f *opentype, str text.String) *draw.Path {
 				}
 				switch fseg.Op {
 				case sfnt.SegmentOpMoveTo:
-					builder.Move(args[0])
+					builder.Move(ops, args[0])
 				case sfnt.SegmentOpLineTo:
-					builder.Line(args[0])
+					builder.Line(ops, args[0])
 				case sfnt.SegmentOpQuadTo:
-					builder.Quad(args[0], args[1])
+					builder.Quad(ops, args[0], args[1])
 				case sfnt.SegmentOpCubeTo:
-					builder.Cube(args[0], args[1], args[2])
+					builder.Cube(ops, args[0], args[1], args[2])
 				default:
 					panic("unsupported segment op")
 				}
@@ -285,5 +287,6 @@ func textPath(ppem fixed.Int26_6, f *opentype, str text.String) *draw.Path {
 		x += str.Advances[advIdx]
 		advIdx++
 	}
-	return builder.Path()
+	builder.End(ops)
+	return ops.End()
 }

ui/ops.go

@@ -11,6 +11,10 @@ type Ops struct {
 	// Stack of block start indices.
 	stack []pc
 	ops   opsData
+
+	inAux  bool
+	auxOff int
+	auxLen int
 }
 
 type opsData struct {
@@ -21,14 +25,30 @@ type opsData struct {
 	refs []interface{}
 }
 
+// OpsReader parses an ops list. Internal use only.
 type OpsReader struct {
 	pc    pc
 	stack []block
-	ops   opsData
+	ops   *opsData
+}
+
+// EncodedOp represents an encoded op returned by
+// OpsReader. Internal use only.
+type EncodedOp struct {
+	Key  OpKey
+	Data []byte
+	Refs []interface{}
+}
+
+// OpKey is a unique key for a given op. Internal use only.
+type OpKey struct {
+	ops     *opsData
+	pc      int
+	version int
 }
 
 type block struct {
-	ops   opsData
+	ops   *opsData
 	retPC pc
 	endPC pc
 }
@@ -44,7 +64,6 @@ var typeLengths = [...]int{
 	ops.TypeTransformLen,
 	ops.TypeLayerLen,
 	ops.TypeRedrawLen,
-	ops.TypeClipLen,
 	ops.TypeImageLen,
 	ops.TypeDrawLen,
 	ops.TypeColorLen,
@@ -53,6 +72,8 @@ var typeLengths = [...]int{
 	ops.TypeHideInputLen,
 	ops.TypePushLen,
 	ops.TypePopLen,
+	ops.TypeAuxLen,
+	ops.TypeClipLen,
 }
 
 var refLengths = [...]int{
@@ -61,7 +82,6 @@ var refLengths = [...]int{
 	ops.TypeTransformRefs,
 	ops.TypeLayerRefs,
 	ops.TypeRedrawRefs,
-	ops.TypeClipRefs,
 	ops.TypeImageRefs,
 	ops.TypeDrawRefs,
 	ops.TypeColorRefs,
@@ -70,6 +90,8 @@ var refLengths = [...]int{
 	ops.TypeHideInputRefs,
 	ops.TypePushRefs,
 	ops.TypePopRefs,
+	ops.TypeAuxRefs,
+	ops.TypeClipRefs,
 }
 
 type OpPush struct{}
@@ -77,7 +99,7 @@ type OpPush struct{}
 type OpPop struct{}
 
 type OpBlock struct {
-	ops     *Ops
+	ops     *opsData
 	version int
 	pc      pc
 }
@@ -86,6 +108,10 @@ type opBlockDef struct {
 	endpc pc
 }
 
+type opAux struct {
+	len int
+}
+
 func (p OpPush) Add(o *Ops) {
 	o.Write([]byte{byte(ops.TypePush)}, nil)
 }
@@ -101,6 +127,16 @@ func (o *Ops) Begin() {
 	o.Write(make([]byte, ops.TypeBlockDefLen), nil)
 }
 
+func (op *opAux) decode(data []byte) {
+	if ops.OpType(data[0]) != ops.TypeAux {
+		panic("invalid op")
+	}
+	bo := binary.LittleEndian
+	*op = opAux{
+		len: int(bo.Uint32(data[1:])),
+	}
+}
+
 func (op *opBlockDef) decode(data []byte) {
 	if ops.OpType(data[0]) != ops.TypeBlockDef {
 		panic("invalid op")
@@ -128,15 +164,24 @@ func (o *Ops) End() OpBlock {
 	bo := binary.LittleEndian
 	bo.PutUint32(data[1:], uint32(pc.data))
 	bo.PutUint32(data[5:], uint32(pc.refs))
-	return OpBlock{ops: o, pc: start, version: o.ops.version}
+	return OpBlock{ops: &o.ops, pc: start, version: o.ops.version}
 }
 
 // Reset clears the Ops.
 func (o *Ops) Reset() {
+	o.inAux = false
 	o.stack = o.stack[:0]
 	o.ops.reset()
 }
 
+// Internal use only.
+func (o *Ops) Aux() []byte {
+	if !o.inAux {
+		return nil
+	}
+	return o.ops.data[o.auxOff+ops.TypeAuxLen : o.auxOff+ops.TypeAuxLen+o.auxLen]
+}
+
 func (d *opsData) reset() {
 	d.data = d.data[:0]
 	d.refs = d.refs[:0]
@@ -149,6 +194,26 @@ func (d *opsData) write(op []byte, refs []interface{}) {
 }
 
 func (o *Ops) Write(op []byte, refs []interface{}) {
+	switch ops.OpType(op[0]) {
+	case ops.TypeAux:
+		// Write only the data.
+		op = op[1:]
+		if !o.inAux {
+			o.inAux = true
+			o.auxOff = o.ops.pc().data
+			o.auxLen = 0
+			header := make([]byte, ops.TypeAuxLen)
+			header[0] = byte(ops.TypeAux)
+			o.ops.write(header, nil)
+		}
+		o.auxLen += len(op)
+	default:
+		if o.inAux {
+			o.inAux = false
+			bo := binary.LittleEndian
+			bo.PutUint32(o.ops.data[o.auxOff+1:], uint32(o.auxLen))
+		}
+	}
 	o.ops.write(op, refs)
 }
 
@@ -165,7 +230,7 @@ func (b *OpBlock) decode(data []byte, refs []interface{}) {
 	refsIdx := int(bo.Uint32(data[5:]))
 	version := int(bo.Uint32(data[9:]))
 	*b = OpBlock{
-		ops: refs[0].(*Ops),
+		ops: refs[0].(*opsData),
 		pc: pc{
 			data: dataIdx,
 			refs: refsIdx,
@@ -186,12 +251,12 @@ func (b OpBlock) Add(o *Ops) {
 
 // Reset start reading from the op list.
 func (r *OpsReader) Reset(ops *Ops) {
-	r.ops = ops.ops
+	r.ops = &ops.ops
 	r.stack = r.stack[:0]
 	r.pc = pc{}
 }
 
-func (r *OpsReader) Decode() ([]byte, []interface{}, bool) {
+func (r *OpsReader) Decode() (EncodedOp, bool) {
 	for {
 		if len(r.stack) > 0 {
 			b := r.stack[len(r.stack)-1]
@@ -203,22 +268,28 @@ func (r *OpsReader) Decode() ([]byte, []interface{}, bool) {
 			}
 		}
 		if r.pc.data == len(r.ops.data) {
-			return nil, nil, false
+			return EncodedOp{}, false
 		}
+		key := OpKey{ops: r.ops, pc: r.pc.data, version: r.ops.version}
 		t := ops.OpType(r.ops.data[r.pc.data])
 		n := typeLengths[t-ops.FirstOpIndex]
 		nrefs := refLengths[t-ops.FirstOpIndex]
 		data := r.ops.data[r.pc.data : r.pc.data+n]
 		refs := r.ops.refs[r.pc.refs : r.pc.refs+nrefs]
 		switch t {
+		case ops.TypeAux:
+			var op opAux
+			op.decode(data)
+			n += op.len
+			data = r.ops.data[r.pc.data : r.pc.data+n]
 		case ops.TypeBlock:
 			var op OpBlock
 			op.decode(data, refs)
-			blockOps := op.ops.ops
+			blockOps := op.ops
 			if ops.OpType(blockOps.data[op.pc.data]) != ops.TypeBlockDef {
 				panic("invalid block reference")
 			}
-			if op.version != r.ops.version {
+			if op.version != op.ops.version {
 				panic("invalid OpBlock reference to reset Ops")
 			}
 			var opDef opBlockDef
@@ -244,6 +315,6 @@ func (r *OpsReader) Decode() ([]byte, []interface{}, bool) {
 		}
 		r.pc.data += n
 		r.pc.refs += nrefs
-		return data, refs, true
+		return EncodedOp{Key: key, Data: data, Refs: refs}, true
 	}
 }

ui/pointer/queue.go

@@ -39,11 +39,11 @@ type handler struct {
 
 func (q *Queue) collectHandlers(r *ui.OpsReader, t ui.Transform, layer int) {
 	for {
-		data, refs, ok := r.Decode()
+		encOp, ok := r.Decode()
 		if !ok {
 			return
 		}
-		switch ops.OpType(data[0]) {
+		switch ops.OpType(encOp.Data[0]) {
 		case ops.TypePush:
 			q.collectHandlers(r, t, layer)
 		case ops.TypePop:
@@ -53,11 +53,11 @@ func (q *Queue) collectHandlers(r *ui.OpsReader, t ui.Transform, layer int) {
 			q.hitTree = append(q.hitTree, hitNode{level: layer})
 		case ops.TypeTransform:
 			var op ui.OpTransform
-			op.Decode(data)
+			op.Decode(encOp.Data)
 			t = t.Mul(op.Transform)
 		case ops.TypePointerHandler:
 			var op OpHandler
-			op.Decode(data, refs)
+			op.Decode(encOp.Data, encOp.Refs)
 			q.hitTree = append(q.hitTree, hitNode{level: layer, key: op.Key})
 			h, ok := q.handlers[op.Key]
 			if !ok {

ui/text/editor.go

@@ -10,7 +10,6 @@ import (
 
 	"gioui.org/ui"
 	"gioui.org/ui/draw"
-	"gioui.org/ui/f32"
 	"gioui.org/ui/gesture"
 	"gioui.org/ui/key"
 	"gioui.org/ui/layout"
@@ -49,11 +48,6 @@ type Editor struct {
 	clicker gesture.Click
 }
 
-type linePath struct {
-	path *draw.Path
-	off  f32.Point
-}
-
 const (
 	blinksPerSecond  = 1
 	maxBlinkDuration = 10 * time.Second
@@ -170,10 +164,9 @@ func (e *Editor) Layout(ops *ui.Ops, cs layout.Constraints) layout.Dimens {
 		if !ok {
 			break
 		}
-		path := e.Face.Path(str)
 		ui.OpPush{}.Add(ops)
 		ui.OpTransform{Transform: ui.Offset(lineOff)}.Add(ops)
-		draw.OpClip{Path: path}.Add(ops)
+		e.Face.Path(str).Add(ops)
 		draw.OpDraw{Rect: toRectF(clip).Sub(lineOff)}.Add(ops)
 		ui.OpPop{}.Add(ops)
 	}

ui/text/label.go

@@ -100,11 +100,10 @@ func (l Label) Layout(ops *ui.Ops, cs layout.Constraints) layout.Dimens {
 		if !ok {
 			break
 		}
-		path := l.Face.Path(str)
 		lclip := toRectF(clip).Sub(off)
 		ui.OpPush{}.Add(ops)
 		ui.OpTransform{Transform: ui.Offset(off)}.Add(ops)
-		draw.OpClip{Path: path}.Add(ops)
+		l.Face.Path(str).Add(ops)
 		draw.OpDraw{Rect: lclip}.Add(ops)
 		ui.OpPop{}.Add(ops)
 	}

ui/text/measure.go

@@ -6,7 +6,7 @@ import (
 	"fmt"
 	"image"
 
-	"gioui.org/ui/draw"
+	"gioui.org/ui"
 	"gioui.org/ui/layout"
 	"golang.org/x/image/math/fixed"
 )
@@ -35,7 +35,7 @@ type Layout struct {
 
 type Face interface {
 	Layout(str string, singleLine bool, maxWidth int) *Layout
-	Path(str String) *draw.Path
+	Path(str String) ui.OpBlock
 }
 
 type Alignment uint8