diff --git a/ui/app/internal/gpu/gpu.go b/ui/app/internal/gpu/gpu.go
index 9f9f6bd0..9f2a854c 100644
--- a/ui/app/internal/gpu/gpu.go
+++ b/ui/app/internal/gpu/gpu.go
@@ -667,7 +667,7 @@ func (d *drawOps) newPathOp() *pathOp {
 func (d *drawOps) collectOps(r *ui.OpsReader, state drawState) int {
 loop:
 	for {
-		data, ok := r.Decode()
+		data, refs, ok := r.Decode()
 		if !ok {
 			break
 		}
@@ -678,7 +678,7 @@ loop:
 			state.t = state.t.Mul(op.Transform)
 		case ops.TypeClip:
 			var op gdraw.OpClip
-			op.Decode(data, r.Refs)
+			op.Decode(data, refs)
 			if op.Path == nil {
 				state.clip = f32.Rectangle{}
 				continue
@@ -702,17 +702,17 @@ loop:
 			}
 		case ops.TypeColor:
 			var op gdraw.OpColor
-			op.Decode(data, r.Refs)
+			op.Decode(data, refs)
 			state.img = nil
 			state.color = op.Col
 		case ops.TypeImage:
 			var op gdraw.OpImage
-			op.Decode(data, r.Refs)
+			op.Decode(data, refs)
 			state.img = op.Img
 			state.imgRect = op.Rect
 		case ops.TypeDraw:
 			var op gdraw.OpDraw
-			op.Decode(data, r.Refs)
+			op.Decode(data, refs)
 			off := state.t.Transform(f32.Point{})
 			clip := state.clip.Intersect(op.Rect.Add(off))
 			if clip.Empty() {
diff --git a/ui/app/window.go b/ui/app/window.go
index 60365c52..74c0f152 100644
--- a/ui/app/window.go
+++ b/ui/app/window.go
@@ -156,7 +156,7 @@ func collectRedraws(r *ui.OpsReader) (time.Time, bool) {
 	var t time.Time
 	redraw := false
 	for {
-		data, ok := r.Decode()
+		data, _, ok := r.Decode()
 		if !ok {
 			break
 		}
diff --git a/ui/draw/draw.go b/ui/draw/draw.go
index e3e3dc09..92690d21 100644
--- a/ui/draw/draw.go
+++ b/ui/draw/draw.go
@@ -31,13 +31,11 @@ func (i OpImage) Add(o *ui.Ops) {
 	data := make([]byte, ops.TypeImageLen)
 	data[0] = byte(ops.TypeImage)
 	bo := binary.LittleEndian
-	ref := o.Ref(i.Img)
-	bo.PutUint32(data[1:], uint32(ref))
-	bo.PutUint32(data[5:], uint32(i.Rect.Min.X))
-	bo.PutUint32(data[9:], uint32(i.Rect.Min.Y))
-	bo.PutUint32(data[13:], uint32(i.Rect.Max.X))
-	bo.PutUint32(data[17:], uint32(i.Rect.Max.Y))
-	o.Write(data)
+	bo.PutUint32(data[1:], uint32(i.Rect.Min.X))
+	bo.PutUint32(data[5:], uint32(i.Rect.Min.Y))
+	bo.PutUint32(data[9:], uint32(i.Rect.Max.X))
+	bo.PutUint32(data[13:], uint32(i.Rect.Max.Y))
+	o.Write(data, []interface{}{i.Img})
 }
 
 func (i *OpImage) Decode(data []byte, refs []interface{}) {
@@ -45,19 +43,18 @@ func (i *OpImage) Decode(data []byte, refs []interface{}) {
 	if ops.OpType(data[0]) != ops.TypeImage {
 		panic("invalid op")
 	}
-	ref := int(bo.Uint32(data[1:]))
 	sr := image.Rectangle{
 		Min: image.Point{
-			X: int(bo.Uint32(data[5:])),
-			Y: int(bo.Uint32(data[9:])),
+			X: int(bo.Uint32(data[1:])),
+			Y: int(bo.Uint32(data[5:])),
 		},
 		Max: image.Point{
-			X: int(bo.Uint32(data[13:])),
-			Y: int(bo.Uint32(data[17:])),
+			X: int(bo.Uint32(data[9:])),
+			Y: int(bo.Uint32(data[13:])),
 		},
 	}
 	*i = OpImage{
-		Img:  refs[ref].(image.Image),
+		Img:  refs[0].(image.Image),
 		Rect: sr,
 	}
 }
@@ -69,7 +66,7 @@ func (c OpColor) Add(o *ui.Ops) {
 	data[2] = c.Col.G
 	data[3] = c.Col.B
 	data[4] = c.Col.A
-	o.Write(data)
+	o.Write(data, nil)
 }
 
 func (c *OpColor) Decode(data []byte, refs []interface{}) {
@@ -94,7 +91,7 @@ func (d OpDraw) Add(o *ui.Ops) {
 	bo.PutUint32(data[5:], math.Float32bits(d.Rect.Min.Y))
 	bo.PutUint32(data[9:], math.Float32bits(d.Rect.Max.X))
 	bo.PutUint32(data[13:], math.Float32bits(d.Rect.Max.Y))
-	o.Write(data)
+	o.Write(data, nil)
 }
 
 func (d *OpDraw) Decode(data []byte, refs []interface{}) {
diff --git a/ui/draw/path.go b/ui/draw/path.go
index 9a0758a8..dbbb7812 100644
--- a/ui/draw/path.go
+++ b/ui/draw/path.go
@@ -3,7 +3,6 @@
 package draw
 
 import (
-	"encoding/binary"
 	"math"
 
 	"gioui.org/ui"
@@ -37,20 +36,15 @@ func (p *Path) Data() interface{} {
 func (c OpClip) Add(o *ui.Ops) {
 	data := make([]byte, ops.TypeClipLen)
 	data[0] = byte(ops.TypeClip)
-	bo := binary.LittleEndian
-	ref := o.Ref(c.Path)
-	bo.PutUint32(data[1:], uint32(ref))
-	o.Write(data)
+	o.Write(data, []interface{}{c.Path})
 }
 
 func (c *OpClip) Decode(d []byte, refs []interface{}) {
-	bo := binary.LittleEndian
 	if ops.OpType(d[0]) != ops.TypeClip {
 		panic("invalid op")
 	}
-	ref := int(bo.Uint32(d[1:]))
 	*c = OpClip{
-		Path: refs[ref].(*Path),
+		Path: refs[0].(*Path),
 	}
 }
 
diff --git a/ui/internal/ops/ops.go b/ui/internal/ops/ops.go
index 481f81aa..b0fa805c 100644
--- a/ui/internal/ops/ops.go
+++ b/ui/internal/ops/ops.go
@@ -2,8 +2,11 @@ package ops
 
 type OpType byte
 
+// Start at a high number for easier debugging.
+const FirstOpIndex = 200
+
 const (
-	TypeBlockDef OpType = iota
+	TypeBlockDef OpType = iota + FirstOpIndex
 	TypeBlock
 	TypeTransform
 	TypeLayer
@@ -20,18 +23,33 @@ const (
 )
 
 const (
-	TypeBlockDefLen       = 1 + 4
-	TypeBlockLen          = 1 + 4
+	TypeBlockDefLen       = 1 + 4 + 4
+	TypeBlockLen          = 1 + 4 + 4
 	TypeTransformLen      = 1 + 4*2
 	TypeLayerLen          = 1
 	TypeRedrawLen         = 1 + 8
-	TypeClipLen           = 1 + 4
-	TypeImageLen          = 1 + 4 + 4*4
+	TypeClipLen           = 1
+	TypeImageLen          = 1 + 4*4
 	TypeDrawLen           = 1 + 4*4
 	TypeColorLen          = 1 + 4
-	TypePointerHandlerLen = 1 + 4 + 4 + 1
-	TypeKeyHandlerLen     = 1 + 4 + 1
+	TypePointerHandlerLen = 1 + 1
+	TypeKeyHandlerLen     = 1 + 1
 	TypeHideInputLen      = 1
 	TypePushLen           = 1
 	TypePopLen            = 1
+
+	TypeBlockDefRefs       = 0
+	TypeBlockRefs          = 0
+	TypeTransformRefs      = 0
+	TypeLayerRefs          = 0
+	TypeRedrawRefs         = 0
+	TypeClipRefs           = 1
+	TypeImageRefs          = 1
+	TypeDrawRefs           = 0
+	TypeColorRefs          = 0
+	TypePointerHandlerRefs = 2
+	TypeKeyHandlerRefs     = 1
+	TypeHideInputRefs      = 0
+	TypePushRefs           = 0
+	TypePopRefs            = 0
 )
diff --git a/ui/key/key.go b/ui/key/key.go
index e8e0c393..128525a5 100644
--- a/ui/key/key.go
+++ b/ui/key/key.go
@@ -3,8 +3,6 @@
 package key
 
 import (
-	"encoding/binary"
-
 	"gioui.org/ui"
 	"gioui.org/ui/internal/ops"
 )
@@ -73,30 +71,26 @@ const (
 func (h OpHandler) Add(o *ui.Ops) {
 	data := make([]byte, ops.TypeKeyHandlerLen)
 	data[0] = byte(ops.TypeKeyHandler)
-	bo := binary.LittleEndian
 	if h.Focus {
 		data[1] = 1
 	}
-	bo.PutUint32(data[2:], uint32(o.Ref(h.Key)))
-	o.Write(data)
+	o.Write(data, []interface{}{h.Key})
 }
 
 func (h *OpHandler) Decode(d []byte, refs []interface{}) {
-	bo := binary.LittleEndian
 	if ops.OpType(d[0]) != ops.TypeKeyHandler {
 		panic("invalid op")
 	}
-	key := int(bo.Uint32(d[2:]))
 	*h = OpHandler{
 		Focus: d[1] != 0,
-		Key:   refs[key].(Key),
+		Key:   refs[0].(Key),
 	}
 }
 
 func (h OpHideInput) Add(o *ui.Ops) {
 	data := make([]byte, ops.TypeHideInputLen)
 	data[0] = byte(ops.TypeHideInput)
-	o.Write(data)
+	o.Write(data, nil)
 }
 
 func (Edit) ImplementsEvent()  {}
diff --git a/ui/key/queue.go b/ui/key/queue.go
index 2727b3eb..cd0582f0 100644
--- a/ui/key/queue.go
+++ b/ui/key/queue.go
@@ -80,14 +80,14 @@ func resolveFocus(r *ui.OpsReader, focus Key) (Key, listenerPriority, bool) {
 	var hide bool
 loop:
 	for {
-		data, ok := r.Decode()
+		data, refs, ok := r.Decode()
 		if !ok {
 			break
 		}
 		switch ops.OpType(data[0]) {
 		case ops.TypeKeyHandler:
 			var op OpHandler
-			op.Decode(data, r.Refs)
+			op.Decode(data, refs)
 			var newPri listenerPriority
 			switch {
 			case op.Focus:
diff --git a/ui/ops.go b/ui/ops.go
index 3c2ec380..1de22759 100644
--- a/ui/ops.go
+++ b/ui/ops.go
@@ -9,7 +9,7 @@ import (
 // Ops holds a list of serialized Ops.
 type Ops struct {
 	// Stack of block start indices.
-	stack []int
+	stack []pc
 	// Serialized ops.
 	data []byte
 	// Op references.
@@ -17,17 +17,22 @@ type Ops struct {
 }
 
 type OpsReader struct {
-	pc    int
+	pc    pc
 	stack []block
-	Refs  []interface{}
+	refs  []interface{}
 	data  []byte
 
 	pseudoOp [1]byte
 }
 
 type block struct {
-	retPC int
-	endPC int
+	retPC pc
+	endPC pc
+}
+
+type pc struct {
+	data int
+	refs int
 }
 
 var typeLengths = [...]int{
@@ -47,16 +52,51 @@ var typeLengths = [...]int{
 	ops.TypePopLen,
 }
 
+var refLengths = [...]int{
+	ops.TypeBlockDefRefs,
+	ops.TypeBlockRefs,
+	ops.TypeTransformRefs,
+	ops.TypeLayerRefs,
+	ops.TypeRedrawRefs,
+	ops.TypeClipRefs,
+	ops.TypeImageRefs,
+	ops.TypeDrawRefs,
+	ops.TypeColorRefs,
+	ops.TypePointerHandlerRefs,
+	ops.TypeKeyHandlerRefs,
+	ops.TypeHideInputRefs,
+	ops.TypePushRefs,
+	ops.TypePopRefs,
+}
+
 type OpBlock struct {
-	idx int
+	pc pc
+}
+
+type opBlockDef struct {
+	endpc pc
 }
 
 // Begin a block of ops.
 func (o *Ops) Begin() {
-	o.stack = append(o.stack, o.Size())
-	data := make([]byte, ops.TypeBlockDefLen)
-	data[0] = byte(ops.TypeBlockDef)
-	o.Write(data)
+	o.stack = append(o.stack, o.pc())
+	// Make room for a block definition. Filled out in End.
+	o.data = append(o.data, make([]byte, ops.TypeBlockDefLen)...)
+}
+
+func (op *opBlockDef) decode(data []byte) {
+	if ops.OpType(data[0]) != ops.TypeBlockDef {
+		panic("invalid op")
+	}
+	bo := binary.LittleEndian
+	dataIdx := int(bo.Uint32(data[1:]))
+	refsIdx := int(bo.Uint32(data[5:]))
+	*op = opBlockDef{
+		endpc: pc{
+			data: dataIdx,
+			refs: refsIdx,
+		},
+	}
 }
 
 // End the most recent block and return
@@ -64,9 +104,13 @@ func (o *Ops) Begin() {
 func (o *Ops) End() OpBlock {
 	start := o.stack[len(o.stack)-1]
 	o.stack = o.stack[:len(o.stack)-1]
-	blockLen := o.Size() - start
+	pc := o.pc()
+	// Write the block header reserved in Begin.
+	data := o.data[start.data : start.data+ops.TypeBlockDefLen]
+	data[0] = byte(ops.TypeBlockDef)
 	bo := binary.LittleEndian
-	bo.PutUint32(o.data[start+1:], uint32(blockLen))
+	bo.PutUint32(data[1:], uint32(pc.data))
+	bo.PutUint32(data[5:], uint32(pc.refs))
 	return OpBlock{start}
 }
 
@@ -77,41 +121,51 @@ func (o *Ops) Reset() {
 	o.data = o.data[:0]
 }
 
-func (o *Ops) Ref(r interface{}) int {
-	o.refs = append(o.refs, r)
-	return len(o.refs) - 1
-}
-
-func (o *Ops) Write(op []byte) {
+func (o *Ops) Write(op []byte, refs []interface{}) {
 	o.data = append(o.data, op...)
+	o.refs = append(o.refs, refs...)
 }
 
-// Size returns the length of the serialized Op data.
-func (o *Ops) Size() int {
-	return len(o.data)
+func (o *Ops) pc() pc {
+	return pc{data: len(o.data), refs: len(o.refs)}
+}
+
+func (b *OpBlock) decode(data []byte) {
+	if ops.OpType(data[0]) != ops.TypeBlock {
+		panic("invalid op")
+	}
+	bo := binary.LittleEndian
+	dataIdx := int(bo.Uint32(data[1:]))
+	refsIdx := int(bo.Uint32(data[5:]))
+	*b = OpBlock{
+		pc: pc{
+			data: dataIdx,
+			refs: refsIdx,
+		},
+	}
 }
 
 func (b OpBlock) Add(o *Ops) {
 	data := make([]byte, ops.TypeBlockLen)
 	data[0] = byte(ops.TypeBlock)
 	bo := binary.LittleEndian
-	bo.PutUint32(data[1:], uint32(b.idx))
-	o.Write(data)
+	bo.PutUint32(data[1:], uint32(b.pc.data))
+	bo.PutUint32(data[5:], uint32(b.pc.refs))
+	o.Write(data, nil)
 }
 
 // Reset start reading from the op list.
 func (r *OpsReader) Reset(ops *Ops) {
-	r.Refs = ops.refs
+	r.refs = ops.refs
 	r.data = ops.data
 	r.stack = r.stack[:0]
-	r.pc = 0
+	r.pc = pc{}
 }
 
-func (r *OpsReader) Decode() ([]byte, bool) {
-	bo := binary.LittleEndian
+func (r *OpsReader) Decode() ([]byte, []interface{}, bool) {
 	for {
-		if r.pc == len(r.data) {
-			return nil, false
+		if r.pc.data == len(r.data) {
+			return nil, nil, false
 		}
 		if len(r.stack) > 0 {
 			b := r.stack[len(r.stack)-1]
@@ -119,28 +173,40 @@ func (r *OpsReader) Decode() ([]byte, bool) {
 				r.pc = b.retPC
 				r.stack = r.stack[:len(r.stack)-1]
 				r.pseudoOp[0] = byte(ops.TypePop)
-				return r.pseudoOp[:], true
+				return r.pseudoOp[:], nil, true
 			}
 		}
-		t := ops.OpType(r.data[r.pc])
-		n := typeLengths[t]
-		data := r.data[r.pc : r.pc+n]
+		t := ops.OpType(r.data[r.pc.data])
+		n := typeLengths[t-ops.FirstOpIndex]
+		nrefs := refLengths[t-ops.FirstOpIndex]
+		data := r.data[r.pc.data : r.pc.data+n]
+		refs := r.refs[r.pc.refs : r.pc.refs+nrefs]
 		switch t {
 		case ops.TypeBlock:
-			blockIdx := int(bo.Uint32(data[1:]))
-			if ops.OpType(r.data[blockIdx]) != ops.TypeBlockDef {
+			var op OpBlock
+			op.decode(data)
+			if ops.OpType(r.data[op.pc.data]) != ops.TypeBlockDef {
 				panic("invalid block reference")
 			}
-			blockLen := int(bo.Uint32(r.data[blockIdx+1:]))
-			r.stack = append(r.stack, block{r.pc + n, blockIdx + blockLen})
-			r.pc = blockIdx + ops.TypeBlockDefLen
+			var opDef opBlockDef
+			opDef.decode(r.data[op.pc.data : op.pc.data+ops.TypeBlockDefLen])
+			retPC := r.pc
+			retPC.data += n
+			retPC.refs += nrefs
+			r.stack = append(r.stack, block{retPC: retPC, endPC: opDef.endpc})
+			r.pc = op.pc
+			r.pc.data += ops.TypeBlockDefLen
+			r.pc.refs += ops.TypeBlockDefRefs
 			r.pseudoOp[0] = byte(ops.TypePush)
-			return r.pseudoOp[:], true
+			return r.pseudoOp[:], nil, true
 		case ops.TypeBlockDef:
-			r.pc += int(bo.Uint32(data[1:]))
+			var op opBlockDef
+			op.decode(data)
+			r.pc = op.endpc
 			continue
 		}
-		r.pc += n
-		return data, true
+		r.pc.data += n
+		r.pc.refs += nrefs
+		return data, refs, true
 	}
 }
diff --git a/ui/pointer/pointer.go b/ui/pointer/pointer.go
index 013824ac..9ff9062a 100644
--- a/ui/pointer/pointer.go
+++ b/ui/pointer/pointer.go
@@ -3,7 +3,6 @@
 package pointer
 
 import (
-	"encoding/binary"
 	"time"
 
 	"gioui.org/ui"
@@ -72,26 +71,20 @@ const (
 func (h OpHandler) Add(o *ui.Ops) {
 	data := make([]byte, ops.TypePointerHandlerLen)
 	data[0] = byte(ops.TypePointerHandler)
-	bo := binary.LittleEndian
 	if h.Grab {
 		data[1] = 1
 	}
-	bo.PutUint32(data[2:], uint32(o.Ref(h.Key)))
-	bo.PutUint32(data[6:], uint32(o.Ref(h.Area)))
-	o.Write(data)
+	o.Write(data, []interface{}{h.Key, h.Area})
 }
 
 func (h *OpHandler) Decode(d []byte, refs []interface{}) {
-	bo := binary.LittleEndian
 	if ops.OpType(d[0]) != ops.TypePointerHandler {
 		panic("invalid op")
 	}
-	key := int(bo.Uint32(d[2:]))
-	area := int(bo.Uint32(d[6:]))
 	*h = OpHandler{
 		Grab: d[1] != 0,
-		Key:  refs[key].(Key),
-		Area: refs[area].(Area),
+		Key:  refs[0].(Key),
+		Area: refs[1].(Area),
 	}
 }
 
diff --git a/ui/pointer/queue.go b/ui/pointer/queue.go
index ef22218a..2299bf27 100644
--- a/ui/pointer/queue.go
+++ b/ui/pointer/queue.go
@@ -39,7 +39,7 @@ type handler struct {
 
 func (q *Queue) collectHandlers(r *ui.OpsReader, t ui.Transform, layer int) {
 	for {
-		data, ok := r.Decode()
+		data, refs, ok := r.Decode()
 		if !ok {
 			return
 		}
@@ -57,7 +57,7 @@ func (q *Queue) collectHandlers(r *ui.OpsReader, t ui.Transform, layer int) {
 			t = t.Mul(op.Transform)
 		case ops.TypePointerHandler:
 			var op OpHandler
-			op.Decode(data, r.Refs)
+			op.Decode(data, refs)
 			q.hitTree = append(q.hitTree, hitNode{level: layer, key: op.Key})
 			h, ok := q.handlers[op.Key]
 			if !ok {
diff --git a/ui/ui.go b/ui/ui.go
index 7a0592aa..c31ec3ca 100644
--- a/ui/ui.go
+++ b/ui/ui.go
@@ -77,7 +77,7 @@ func (r OpRedraw) Add(o *Ops) {
 			bo.PutUint64(data[1:], uint64(nanos))
 		}
 	}
-	o.Write(data)
+	o.Write(data, nil)
 }
 
 func (r *OpRedraw) Decode(d []byte) {
@@ -110,7 +110,7 @@ func (t OpTransform) Add(o *Ops) {
 	bo := binary.LittleEndian
 	bo.PutUint32(data[1:], math.Float32bits(t.Transform.offset.X))
 	bo.PutUint32(data[5:], math.Float32bits(t.Transform.offset.Y))
-	o.Write(data)
+	o.Write(data, nil)
 }
 
 func (t *OpTransform) Decode(d []byte) {
@@ -129,7 +129,7 @@ func (t *OpTransform) Decode(d []byte) {
 func (l OpLayer) Add(o *Ops) {
 	data := make([]byte, ops.TypeLayerLen)
 	data[0] = byte(ops.TypeLayer)
-	o.Write(data)
+	o.Write(data, nil)
 }
 
 func (l *OpLayer) Decode(d []byte) {