diff --git a/cmd/go.mod b/cmd/go.mod
index 6d1497e2..c583b72e 100644
--- a/cmd/go.mod
+++ b/cmd/go.mod
@@ -3,7 +3,7 @@ module gioui.org/cmd
 go 1.13
 
 require (
-	gioui.org v0.0.0-20200521183411-67382bec3949
+	gioui.org v0.0.0-20200523202849-2451750782b8
 	github.com/chromedp/cdproto v0.0.0-20191114225735-6626966fbae4
 	github.com/chromedp/chromedp v0.5.2
 	golang.org/x/image v0.0.0-20190802002840-cff245a6509b
diff --git a/cmd/go.sum b/cmd/go.sum
index f11d3be2..71d0e62d 100644
--- a/cmd/go.sum
+++ b/cmd/go.sum
@@ -1,6 +1,6 @@
 dmitri.shuralyov.com/gpu/mtl v0.0.0-20190408044501-666a987793e9/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
-gioui.org v0.0.0-20200521183411-67382bec3949 h1:Nvvyn28PT4kyRKBKg04QY2ZU6y9J1hFGJtBDV5VyBmM=
-gioui.org v0.0.0-20200521183411-67382bec3949/go.mod h1:AHI9rFr6AEEHCb8EPVtb/p5M+NMJRKH58IOp8O3Je04=
+gioui.org v0.0.0-20200523202849-2451750782b8 h1:TB+F3jDAVjNemdtgc8yfvsPy1xWkyn7JLOsm5r+YUuQ=
+gioui.org v0.0.0-20200523202849-2451750782b8/go.mod h1:AHI9rFr6AEEHCb8EPVtb/p5M+NMJRKH58IOp8O3Je04=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802 h1:1BDTz0u9nC3//pOCMdNH+CiXJVYJh5UQNCOBG7jbELc=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
 github.com/chromedp/cdproto v0.0.0-20191114225735-6626966fbae4 h1:QD3KxSJ59L2lxG6MXBjNHxiQO2RmxTQ3XcK+wO44WOg=
diff --git a/cmd/gogio/testdata/red.go b/cmd/gogio/testdata/red.go
index b71d02c5..67ef722b 100644
--- a/cmd/gogio/testdata/red.go
+++ b/cmd/gogio/testdata/red.go
@@ -14,6 +14,7 @@ import (
 	"gioui.org/io/pointer"
 	"gioui.org/io/system"
 	"gioui.org/layout"
+	"gioui.org/op"
 	"gioui.org/op/paint"
 )
 
@@ -39,6 +40,11 @@ const (
 // when a frame is ready. Initially we want to notify about the first frame.
 var notify = notifyInvalidate
 
+type (
+	C = layout.Context
+	D = layout.Dimensions
+)
+
 func loop(w *app.Window) error {
 	topLeft := quarterWidget{
 		color: color.RGBA{R: 0xde, G: 0xad, B: 0xbe, A: 0xff},
@@ -53,30 +59,29 @@ func loop(w *app.Window) error {
 		color: color.RGBA{R: 0x00, G: 0x00, B: 0x00, A: 0x80},
 	}
 
-	gtx := new(layout.Context)
+	var ops op.Ops
 	for {
 		e := <-w.Events()
 		switch e := e.(type) {
 		case system.DestroyEvent:
 			return e.Err
 		case system.FrameEvent:
-
-			gtx.Reset(e.Queue, e.Config, e.Size)
+			gtx := layout.NewContext(&ops, e.Queue, e.Config, e.Size)
 			layout.Flex{Axis: layout.Vertical}.Layout(gtx,
-				layout.Flexed(0.5, func() {
-					layout.Flex{Axis: layout.Horizontal}.Layout(gtx,
+				layout.Flexed(0.5, func(gtx C) D {
+					return layout.Flex{Axis: layout.Horizontal}.Layout(gtx,
 						// r1c1
-						layout.Flexed(0.5, func() { topLeft.Layout(gtx) }),
+						layout.Flexed(0.5, func(gtx C) D { return topLeft.Layout(gtx) }),
 						// r1c2
-						layout.Flexed(0.5, func() { topRight.Layout(gtx) }),
+						layout.Flexed(0.5, func(gtx C) D { return topRight.Layout(gtx) }),
 					)
 				}),
-				layout.Flexed(0.5, func() {
-					layout.Flex{Axis: layout.Horizontal}.Layout(gtx,
+				layout.Flexed(0.5, func(gtx C) D {
+					return layout.Flex{Axis: layout.Horizontal}.Layout(gtx,
 						// r2c1
-						layout.Flexed(0.5, func() { botLeft.Layout(gtx) }),
+						layout.Flexed(0.5, func(gtx C) D { return botLeft.Layout(gtx) }),
 						// r2c2
-						layout.Flexed(0.5, func() { botRight.Layout(gtx) }),
+						layout.Flexed(0.5, func(gtx C) D { return botRight.Layout(gtx) }),
 					)
 				}),
 			)
@@ -105,7 +110,7 @@ type quarterWidget struct {
 
 var red = color.RGBA{R: 0xff, G: 0x00, B: 0x00, A: 0xff}
 
-func (w *quarterWidget) Layout(gtx *layout.Context) {
+func (w *quarterWidget) Layout(gtx layout.Context) layout.Dimensions {
 	if w.clicked {
 		paint.ColorOp{Color: red}.Add(gtx.Ops)
 	} else {
@@ -128,4 +133,5 @@ func (w *quarterWidget) Layout(gtx *layout.Context) {
 			notify = notifyInvalidate
 		}
 	}
+	return layout.Dimensions{Size: gtx.Constraints.Max}
 }
diff --git a/example/glfw/main.go b/example/glfw/main.go
index fe45ad20..2946851e 100644
--- a/example/glfw/main.go
+++ b/example/glfw/main.go
@@ -29,6 +29,7 @@ import (
 	"gioui.org/io/pointer"
 	"gioui.org/io/router"
 	"gioui.org/layout"
+	"gioui.org/op"
 	"gioui.org/unit"
 	"gioui.org/widget"
 	"gioui.org/widget/material"
@@ -71,7 +72,7 @@ func main() {
 	gofont.Register()
 	f := new(goglFunctions)
 	var queue router.Router
-	gtx := new(layout.Context)
+	var ops op.Ops
 	th := material.NewTheme()
 	backend, err := giogl.NewBackend(f)
 	if err != nil {
@@ -92,7 +93,7 @@ func main() {
 		}
 		width, height := window.GetSize()
 		sz := image.Point{X: width, Y: height}
-		gtx.Reset(&queue, &glfwConfig{scale}, sz)
+		gtx := layout.NewContext(&ops, &queue, &glfwConfig{scale}, sz)
 		draw(gtx, th)
 		gpu.Collect(sz, gtx.Ops)
 		gpu.BeginFrame()
@@ -104,10 +105,10 @@ func main() {
 
 var button widget.Clickable
 
-func draw(gtx *layout.Context, th *material.Theme) {
-	layout.Center.Layout(gtx, func() {
-		material.Button(th, "Button").Layout(gtx, &button)
-	})
+func draw(gtx layout.Context, th *material.Theme) layout.Dimensions {
+	return layout.Center.Layout(gtx,
+		material.Button(th, &button, "Button").Layout,
+	)
 }
 
 func registerCallbacks(window *glfw.Window, q *router.Router) {
diff --git a/example/go.mod b/example/go.mod
index cec3fa55..a4a42312 100644
--- a/example/go.mod
+++ b/example/go.mod
@@ -3,7 +3,7 @@ module gioui.org/example
 go 1.13
 
 require (
-	gioui.org v0.0.0-20200521183411-67382bec3949
+	gioui.org v0.0.0-20200523202849-2451750782b8
 	github.com/go-gl/gl v0.0.0-20190320180904-bf2b1f2f34d7
 	github.com/go-gl/glfw/v3.3/glfw v0.0.0-20191125211704-12ad95a8df72
 	github.com/google/go-github/v24 v24.0.1
diff --git a/example/go.sum b/example/go.sum
index 0fc3c5da..40d3f18a 100644
--- a/example/go.sum
+++ b/example/go.sum
@@ -1,7 +1,7 @@
 cloud.google.com/go v0.34.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 dmitri.shuralyov.com/gpu/mtl v0.0.0-20190408044501-666a987793e9/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
-gioui.org v0.0.0-20200521183411-67382bec3949 h1:Nvvyn28PT4kyRKBKg04QY2ZU6y9J1hFGJtBDV5VyBmM=
-gioui.org v0.0.0-20200521183411-67382bec3949/go.mod h1:AHI9rFr6AEEHCb8EPVtb/p5M+NMJRKH58IOp8O3Je04=
+gioui.org v0.0.0-20200523202849-2451750782b8 h1:TB+F3jDAVjNemdtgc8yfvsPy1xWkyn7JLOsm5r+YUuQ=
+gioui.org v0.0.0-20200523202849-2451750782b8/go.mod h1:AHI9rFr6AEEHCb8EPVtb/p5M+NMJRKH58IOp8O3Je04=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
 github.com/go-gl/gl v0.0.0-20190320180904-bf2b1f2f34d7 h1:SCYMcCJ89LjRGwEa0tRluNRiMjZHalQZrVrvTbPh+qw=
 github.com/go-gl/gl v0.0.0-20190320180904-bf2b1f2f34d7/go.mod h1:482civXOzJJCPzJ4ZOX/pwvXBWSnzD4OKMdH4ClKGbk=
diff --git a/example/gophers/main.go b/example/gophers/main.go
index 73a925d3..af916f65 100644
--- a/example/gophers/main.go
+++ b/example/gophers/main.go
@@ -20,6 +20,7 @@ import (
 	"gioui.org/io/key"
 	"gioui.org/io/system"
 	"gioui.org/layout"
+	"gioui.org/op"
 	"gioui.org/unit"
 
 	"github.com/google/go-github/v24/github"
@@ -77,7 +78,7 @@ func initProfiling() {
 
 func (a *App) run() error {
 	a.ui.profiling = *stats
-	gtx := new(layout.Context)
+	var ops op.Ops
 	for {
 		select {
 		case users := <-a.updateUsers:
@@ -125,7 +126,7 @@ func (a *App) run() error {
 					}
 				}
 			case system.FrameEvent:
-				gtx.Reset(e.Queue, e.Config, e.Size)
+				gtx := layout.NewContext(&ops, e.Queue, e.Config, e.Size)
 				a.ui.Layout(gtx)
 				e.Frame(gtx.Ops)
 			}
diff --git a/example/gophers/main_test.go b/example/gophers/main_test.go
index 5b7018d1..bc147f75 100644
--- a/example/gophers/main_test.go
+++ b/example/gophers/main_test.go
@@ -7,14 +7,18 @@ import (
 	"testing"
 
 	"gioui.org/layout"
+	"gioui.org/op"
 )
 
 func BenchmarkUI(b *testing.B) {
 	fetch := func(_ string) {}
 	u := newUI(fetch)
-	gtx := new(layout.Context)
+	var ops op.Ops
 	for i := 0; i < b.N; i++ {
-		gtx.Reset(nil, nil, image.Point{800, 600})
+		gtx := layout.Context{
+			Ops:         &ops,
+			Constraints: layout.Exact(image.Pt(800, 600)),
+		}
 		u.Layout(gtx)
 	}
 }
diff --git a/example/gophers/ui.go b/example/gophers/ui.go
index 4890dba2..60903832 100644
--- a/example/gophers/ui.go
+++ b/example/gophers/ui.go
@@ -65,6 +65,11 @@ type user struct {
 
 var theme *material.Theme
 
+type (
+	C = layout.Context
+	D = layout.Dimensions
+)
+
 func init() {
 	gofont.Register()
 	theme = material.NewTheme()
@@ -106,7 +111,7 @@ func argb(c uint32) color.RGBA {
 	return color.RGBA{A: uint8(c >> 24), R: uint8(c >> 16), G: uint8(c >> 8), B: uint8(c)}
 }
 
-func (u *UI) layoutTimings(gtx *layout.Context) {
+func (u *UI) layoutTimings(gtx layout.Context) {
 	if !u.profiling {
 		return
 	}
@@ -120,17 +125,17 @@ func (u *UI) layoutTimings(gtx *layout.Context) {
 	runtime.ReadMemStats(&mstats)
 	mallocs := mstats.Mallocs - u.lastMallocs
 	u.lastMallocs = mstats.Mallocs
-	layout.NE.Layout(gtx, func() {
-		layout.Inset{Top: unit.Dp(16)}.Layout(gtx, func() {
+	layout.NE.Layout(gtx, func(gtx C) D {
+		return layout.Inset{Top: unit.Dp(16)}.Layout(gtx, func(gtx C) D {
 			txt := fmt.Sprintf("m: %d %s", mallocs, u.profile.Timings)
 			lbl := material.Caption(theme, txt)
 			lbl.Font.Variant = "Mono"
-			lbl.Layout(gtx)
+			return lbl.Layout(gtx)
 		})
 	})
 }
 
-func (u *UI) Layout(gtx *layout.Context) {
+func (u *UI) Layout(gtx layout.Context) {
 	for i := range u.userClicks {
 		click := &u.userClicks[i]
 		for _, e := range click.Events(gtx) {
@@ -156,159 +161,155 @@ func (u *UI) newUserPage(user *user) *userPage {
 	return up
 }
 
-func (up *userPage) Layout(gtx *layout.Context) {
+func (up *userPage) Layout(gtx layout.Context) {
 	l := up.commitsList
 	if l.Dragging() {
 		key.HideInputOp{}.Add(gtx.Ops)
 	}
-	l.Layout(gtx, len(up.commits), func(i int) {
-		up.commit(gtx, i)
+	l.Layout(gtx, len(up.commits), func(gtx C, i int) D {
+		return up.commit(gtx, i)
 	})
 }
 
-func (up *userPage) commit(gtx *layout.Context, index int) {
+func (up *userPage) commit(gtx layout.Context, index int) layout.Dimensions {
 	u := up.user
 	msg := up.commits[index].GetMessage()
 	label := material.Caption(theme, msg)
 	in := layout.Inset{Top: unit.Dp(16), Right: unit.Dp(8), Left: unit.Dp(8)}
-	in.Layout(gtx, func() {
-		layout.Flex{Axis: layout.Horizontal}.Layout(gtx,
-			layout.Rigid(func() {
+	return in.Layout(gtx, func(gtx C) D {
+		return layout.Flex{Axis: layout.Horizontal}.Layout(gtx,
+			layout.Rigid(func(gtx C) D {
 				sz := gtx.Px(unit.Dp(48))
 				cc := clipCircle{}
-				cc.Layout(gtx, func() {
+				return cc.Layout(gtx, func(gtx C) D {
 					gtx.Constraints = layout.Exact(gtx.Constraints.Constrain(image.Point{X: sz, Y: sz}))
-					u.layoutAvatar(gtx)
+					return u.layoutAvatar(gtx)
 				})
 			}),
-			layout.Flexed(1, func() {
+			layout.Flexed(1, func(gtx C) D {
 				gtx.Constraints.Min.X = gtx.Constraints.Max.X
-				layout.Inset{Left: unit.Dp(8)}.Layout(gtx, func() {
-					label.Layout(gtx)
-				})
+				return layout.Inset{Left: unit.Dp(8)}.Layout(gtx, label.Layout)
 			}),
 		)
 	})
 }
 
-func (u *UI) layoutUsers(gtx *layout.Context) {
+func (u *UI) layoutUsers(gtx layout.Context) {
 	layout.Stack{Alignment: layout.SE}.Layout(gtx,
-		layout.Expanded(func() {
-			layout.Flex{Axis: layout.Vertical}.Layout(gtx,
-				layout.Rigid(func() {
+		layout.Expanded(func(gtx C) D {
+			return layout.Flex{Axis: layout.Vertical}.Layout(gtx,
+				layout.Rigid(func(gtx C) D {
 					gtx.Constraints.Min.X = gtx.Constraints.Max.X
-					layout.UniformInset(unit.Dp(16)).Layout(gtx, func() {
+					return layout.UniformInset(unit.Dp(16)).Layout(gtx, func(gtx C) D {
 						sz := gtx.Px(unit.Dp(200))
 						cs := gtx.Constraints
 						gtx.Constraints = layout.Exact(cs.Constrain(image.Point{X: sz, Y: sz}))
-						material.Editor(theme, "Hint").Layout(gtx, u.edit)
+						return material.Editor(theme, u.edit, "Hint").Layout(gtx)
 					})
 				}),
-				layout.Rigid(func() {
+				layout.Rigid(func(gtx C) D {
 					gtx.Constraints.Min.X = gtx.Constraints.Max.X
 					in := layout.Inset{Bottom: unit.Dp(16), Left: unit.Dp(16), Right: unit.Dp(16)}
-					in.Layout(gtx, func() {
-						e := material.Editor(theme, "Hint")
+					return in.Layout(gtx, func(gtx C) D {
+						e := material.Editor(theme, u.edit2, "Hint")
 						e.TextSize = unit.Sp(14)
 						e.Font.Style = text.Italic
-						e.Layout(gtx, u.edit2)
+						return e.Layout(gtx)
 					})
 				}),
-				layout.Rigid(func() {
-					layout.Stack{}.Layout(gtx,
-						layout.Expanded(func() {
+				layout.Rigid(func(gtx C) D {
+					return layout.Stack{}.Layout(gtx,
+						layout.Expanded(func(gtx C) D {
 							gtx.Constraints.Min.X = gtx.Constraints.Max.X
-							fill{rgb(0xf2f2f2)}.Layout(gtx)
+							return fill{rgb(0xf2f2f2)}.Layout(gtx)
 						}),
-						layout.Stacked(func() {
+						layout.Stacked(func(gtx C) D {
 							in := layout.Inset{Top: unit.Dp(16), Right: unit.Dp(8), Bottom: unit.Dp(8), Left: unit.Dp(8)}
-							in.Layout(gtx, func() {
+							return in.Layout(gtx, func(gtx C) D {
 								lbl := material.Caption(theme, "GOPHERS")
 								lbl.Color = rgb(0x888888)
-								lbl.Layout(gtx)
+								return lbl.Layout(gtx)
 							})
 						}),
 					)
 				}),
-				layout.Flexed(1, func() {
+				layout.Flexed(1, func(gtx C) D {
 					gtx.Constraints.Min.X = gtx.Constraints.Max.X
-					u.layoutContributors(gtx)
+					return u.layoutContributors(gtx)
 				}),
 			)
 		}),
-		layout.Stacked(func() {
+		layout.Stacked(func(gtx C) D {
 			in := layout.UniformInset(unit.Dp(16))
-			in.Layout(gtx, func() {
+			return in.Layout(gtx, func(gtx C) D {
 				for u.fab.Clicked(gtx) {
 				}
-				material.IconButton(theme, u.fabIcon).Layout(gtx, u.fab)
+				return material.IconButton(theme, u.fab, u.fabIcon).Layout(gtx)
 			})
 		}),
 	)
 }
 
-func (u *UI) layoutContributors(gtx *layout.Context) {
+func (u *UI) layoutContributors(gtx layout.Context) layout.Dimensions {
 	l := u.usersList
 	if l.Dragging() {
 		key.HideInputOp{}.Add(gtx.Ops)
 	}
-	l.Layout(gtx, len(u.users), func(i int) {
-		u.user(gtx, i)
+	return l.Layout(gtx, len(u.users), func(gtx C, i int) D {
+		return u.user(gtx, i)
 	})
 }
 
-func (u *UI) user(gtx *layout.Context, index int) {
+func (u *UI) user(gtx layout.Context, index int) layout.Dimensions {
 	user := u.users[index]
 	in := layout.UniformInset(unit.Dp(8))
-	in.Layout(gtx, func() {
-		centerRowOpts().Layout(gtx,
-			layout.Rigid(func() {
+	dims := in.Layout(gtx, func(gtx C) D {
+		return centerRowOpts().Layout(gtx,
+			layout.Rigid(func(gtx C) D {
 				in := layout.Inset{Right: unit.Dp(8)}
 				cc := clipCircle{}
-				in.Layout(gtx, func() {
-					cc.Layout(gtx, func() {
+				return in.Layout(gtx, func(gtx C) D {
+					return cc.Layout(gtx, func(gtx C) D {
 						dim := gtx.Px(unit.Dp(48))
 						sz := image.Point{X: dim, Y: dim}
 						gtx.Constraints = layout.Exact(gtx.Constraints.Constrain(sz))
-						user.layoutAvatar(gtx)
+						return user.layoutAvatar(gtx)
 					})
 				})
 			}),
-			layout.Rigid(func() {
-				column().Layout(gtx,
-					layout.Rigid(func() {
-						baseline().Layout(gtx,
-							layout.Rigid(func() {
-								material.Body1(theme, user.name).Layout(gtx)
-							}),
-							layout.Flexed(1, func() {
+			layout.Rigid(func(gtx C) D {
+				return column().Layout(gtx,
+					layout.Rigid(func(gtx C) D {
+						return baseline().Layout(gtx,
+							layout.Rigid(material.Body1(theme, user.name).Layout),
+							layout.Flexed(1, func(gtx C) D {
 								gtx.Constraints.Min.X = gtx.Constraints.Max.X
-								layout.E.Layout(gtx, func() {
-									layout.Inset{Left: unit.Dp(2)}.Layout(gtx, func() {
-										material.Caption(theme, "3 hours ago").Layout(gtx)
-									})
+								return layout.E.Layout(gtx, func(gtx C) D {
+									return layout.Inset{Left: unit.Dp(2)}.Layout(gtx,
+										material.Caption(theme, "3 hours ago").Layout)
 								})
 							}),
 						)
 					}),
-					layout.Rigid(func() {
+					layout.Rigid(func(gtx C) D {
 						in := layout.Inset{Top: unit.Dp(4)}
-						in.Layout(gtx, func() {
+						return in.Layout(gtx, func(gtx C) D {
 							lbl := material.Caption(theme, user.company)
 							lbl.Color = rgb(0xbbbbbb)
-							lbl.Layout(gtx)
+							return lbl.Layout(gtx)
 						})
 					}),
 				)
 			}),
 		)
 	})
-	pointer.Rect(image.Rectangle{Max: gtx.Dimensions.Size}).Add(gtx.Ops)
+	pointer.Rect(image.Rectangle{Max: dims.Size}).Add(gtx.Ops)
 	click := &u.userClicks[index]
 	click.Add(gtx.Ops)
+	return dims
 }
 
-func (u *user) layoutAvatar(gtx *layout.Context) {
+func (u *user) layoutAvatar(gtx layout.Context) layout.Dimensions {
 	sz := gtx.Constraints.Min.X
 	if u.avatarOp.Size().X != sz {
 		img := image.NewRGBA(image.Rectangle{Max: image.Point{X: sz, Y: sz}})
@@ -317,14 +318,14 @@ func (u *user) layoutAvatar(gtx *layout.Context) {
 	}
 	img := widget.Image{Src: u.avatarOp}
 	img.Scale = float32(sz) / float32(gtx.Px(unit.Dp(float32(sz))))
-	img.Layout(gtx)
+	return img.Layout(gtx)
 }
 
 type fill struct {
 	col color.RGBA
 }
 
-func (f fill) Layout(gtx *layout.Context) {
+func (f fill) Layout(gtx layout.Context) layout.Dimensions {
 	cs := gtx.Constraints
 	d := cs.Min
 	dr := f32.Rectangle{
@@ -332,7 +333,7 @@ func (f fill) Layout(gtx *layout.Context) {
 	}
 	paint.ColorOp{Color: f.col}.Add(gtx.Ops)
 	paint.PaintOp{Rect: dr}.Add(gtx.Ops)
-	gtx.Dimensions = layout.Dimensions{Size: d}
+	return layout.Dimensions{Size: d}
 }
 
 func column() layout.Flex {
@@ -350,12 +351,11 @@ func baseline() layout.Flex {
 type clipCircle struct {
 }
 
-func (c *clipCircle) Layout(gtx *layout.Context, w layout.Widget) {
+func (c *clipCircle) Layout(gtx layout.Context, w layout.Widget) layout.Dimensions {
 	var m op.MacroOp
 	m.Record(gtx.Ops)
-	w()
+	dims := w(gtx)
 	m.Stop()
-	dims := gtx.Dimensions
 	max := dims.Size.X
 	if dy := dims.Size.Y; dy > max {
 		max = dy
@@ -370,6 +370,7 @@ func (c *clipCircle) Layout(gtx *layout.Context, w layout.Widget) {
 	}.Op(gtx.Ops).Add(gtx.Ops)
 	m.Add()
 	stack.Pop()
+	return dims
 }
 
 const longTextSample = `1. I learned from my grandfather, Verus, to use good manners, and to
diff --git a/example/hello/hello.go b/example/hello/hello.go
index 5bfc6f31..8cc34091 100644
--- a/example/hello/hello.go
+++ b/example/hello/hello.go
@@ -11,6 +11,7 @@ import (
 	"gioui.org/app"
 	"gioui.org/io/system"
 	"gioui.org/layout"
+	"gioui.org/op"
 	"gioui.org/text"
 	"gioui.org/widget/material"
 
@@ -30,14 +31,14 @@ func main() {
 func loop(w *app.Window) error {
 	gofont.Register()
 	th := material.NewTheme()
-	gtx := new(layout.Context)
+	var ops op.Ops
 	for {
 		e := <-w.Events()
 		switch e := e.(type) {
 		case system.DestroyEvent:
 			return e.Err
 		case system.FrameEvent:
-			gtx.Reset(e.Queue, e.Config, e.Size)
+			gtx := layout.NewContext(&ops, e.Queue, e.Config, e.Size)
 			l := material.H1(th, "Hello, Gio")
 			maroon := color.RGBA{127, 0, 0, 255}
 			l.Color = maroon
diff --git a/example/kitchen/kitchen.go b/example/kitchen/kitchen.go
index 7b89fa05..1c60f29d 100644
--- a/example/kitchen/kitchen.go
+++ b/example/kitchen/kitchen.go
@@ -22,6 +22,7 @@ import (
 	"gioui.org/font/gofont"
 	"gioui.org/io/system"
 	"gioui.org/layout"
+	"gioui.org/op"
 	"gioui.org/text"
 	"gioui.org/unit"
 	"gioui.org/widget"
@@ -37,7 +38,10 @@ type scaledConfig struct {
 }
 
 type iconAndTextButton struct {
-	theme *material.Theme
+	theme  *material.Theme
+	button *widget.Clickable
+	icon   *widget.Icon
+	word   string
 }
 
 func main() {
@@ -81,8 +85,11 @@ func saveScreenshot(f string) error {
 	if err != nil {
 		return err
 	}
-	gtx := new(layout.Context)
-	gtx.Reset(nil, &scaledConfig{scale}, sz)
+	gtx := layout.Context{
+		Ops:         new(op.Ops),
+		Config:      &scaledConfig{scale},
+		Constraints: layout.Exact(sz),
+	}
 	th := material.NewTheme()
 	kitchen(gtx, th)
 	w.Frame(gtx.Ops)
@@ -100,7 +107,7 @@ func saveScreenshot(f string) error {
 func loop(w *app.Window) error {
 	th := material.NewTheme()
 
-	gtx := new(layout.Context)
+	var ops op.Ops
 	for {
 		select {
 		case e := <-w.Events():
@@ -110,7 +117,7 @@ func loop(w *app.Window) error {
 			case system.DestroyEvent:
 				return e.Err
 			case system.FrameEvent:
-				gtx.Reset(e.Queue, e.Config, e.Size)
+				gtx := layout.NewContext(&ops, e.Queue, e.Config, e.Size)
 				for iconButton.Clicked(gtx) {
 					w.WriteClipboard(lineEditor.Text())
 				}
@@ -154,134 +161,125 @@ var (
 	swtch               = new(widget.Bool)
 )
 
-func (b iconAndTextButton) Layout(gtx *layout.Context, button *widget.Clickable, icon *widget.Icon, word string) {
-	material.ButtonLayout(b.theme).Layout(gtx, button, func() {
+type (
+	D = layout.Dimensions
+	C = layout.Context
+)
+
+func (b iconAndTextButton) Layout(gtx layout.Context) layout.Dimensions {
+	return material.ButtonLayout(b.theme, b.button).Layout(gtx, func(gtx C) D {
 		iconAndLabel := layout.Flex{Axis: layout.Horizontal, Alignment: layout.Middle}
 		textIconSpacer := unit.Dp(5)
 
-		layIcon := layout.Rigid(func() {
-			layout.Inset{Right: textIconSpacer}.Layout(gtx, func() {
-				size := gtx.Px(unit.Dp(56)) - 2*gtx.Px(unit.Dp(16))
+		layIcon := layout.Rigid(func(gtx C) D {
+			return layout.Inset{Right: textIconSpacer}.Layout(gtx, func(gtx C) D {
+				var d D
 				if icon != nil {
-					icon.Layout(gtx, unit.Px(float32(size)))
-					gtx.Dimensions = layout.Dimensions{
+					size := gtx.Px(unit.Dp(56)) - 2*gtx.Px(unit.Dp(16))
+					b.icon.Layout(gtx, unit.Px(float32(size)))
+					d = layout.Dimensions{
 						Size: image.Point{X: size, Y: size},
 					}
 				}
+				return d
 			})
 		})
 
-		layLabel := layout.Rigid(func() {
-			layout.Inset{Left: textIconSpacer}.Layout(gtx, func() {
-				l := material.Body1(b.theme, word)
+		layLabel := layout.Rigid(func(gtx C) D {
+			return layout.Inset{Left: textIconSpacer}.Layout(gtx, func(gtx C) D {
+				l := material.Body1(b.theme, b.word)
 				l.Color = b.theme.Color.InvText
-				l.Layout(gtx)
+				return l.Layout(gtx)
 			})
 		})
 
-		iconAndLabel.Layout(gtx, layIcon, layLabel)
+		return iconAndLabel.Layout(gtx, layIcon, layLabel)
 	})
 }
 
-func kitchen(gtx *layout.Context, th *material.Theme) {
-	widgets := []func(){
-		func() {
-			material.H3(th, topLabel).Layout(gtx)
-		},
-		func() {
+func kitchen(gtx layout.Context, th *material.Theme) layout.Dimensions {
+	widgets := []layout.Widget{
+		material.H3(th, topLabel).Layout,
+		func(gtx C) D {
 			gtx.Constraints.Max.Y = gtx.Px(unit.Dp(200))
-			material.Editor(th, "Hint").Layout(gtx, editor)
+			return material.Editor(th, editor, "Hint").Layout(gtx)
 		},
-		func() {
-			e := material.Editor(th, "Hint")
-			e.Font.Style = text.Italic
-			e.Layout(gtx, lineEditor)
+		func(gtx C) D {
 			for _, e := range lineEditor.Events(gtx) {
 				if e, ok := e.(widget.SubmitEvent); ok {
 					topLabel = e.Text
 					lineEditor.SetText("")
 				}
 			}
+			e := material.Editor(th, lineEditor, "Hint")
+			e.Font.Style = text.Italic
+			return e.Layout(gtx)
 		},
-		func() {
+		func(gtx C) D {
 			in := layout.UniformInset(unit.Dp(8))
-			layout.Flex{Alignment: layout.Middle}.Layout(gtx,
-				layout.Rigid(func() {
-					in.Layout(gtx, func() {
-						material.IconButton(th, icon).Layout(gtx, iconButton)
-					})
+			return layout.Flex{Alignment: layout.Middle}.Layout(gtx,
+				layout.Rigid(func(gtx C) D {
+					return in.Layout(gtx, material.IconButton(th, iconButton, icon).Layout)
 				}),
-				layout.Rigid(func() {
-					in.Layout(gtx, func() {
-						iconAndTextButton{th}.Layout(gtx, iconTextButton, icon, "Icon")
-					})
+				layout.Rigid(func(gtx C) D {
+					return in.Layout(gtx, iconAndTextButton{theme: th, icon: icon, word: "Icon", button: iconTextButton}.Layout)
 				}),
-				layout.Rigid(func() {
-					in.Layout(gtx, func() {
+				layout.Rigid(func(gtx C) D {
+					return in.Layout(gtx, func(gtx C) D {
 						for button.Clicked(gtx) {
 							green = !green
 						}
-						material.Button(th, "Click me!").Layout(gtx, button)
+						return material.Button(th, button, "Click me!").Layout(gtx)
 					})
 				}),
-				layout.Rigid(func() {
-					in.Layout(gtx, func() {
+				layout.Rigid(func(gtx C) D {
+					return in.Layout(gtx, func(gtx C) D {
 						l := "Green"
 						if !green {
 							l = "Blue"
 						}
-						btn := material.Button(th, l)
+						btn := material.Button(th, greenButton, l)
 						if green {
 							btn.Background = color.RGBA{A: 0xff, R: 0x9e, G: 0x9d, B: 0x24}
 						}
-						btn.Layout(gtx, greenButton)
+						return btn.Layout(gtx)
 					})
 				}),
-				layout.Rigid(func() {
-					in.Layout(gtx, func() {
-						material.Clickable(gtx, flatBtn, func() {
-							layout.UniformInset(unit.Dp(12)).Layout(gtx, func() {
-								layout.Center.Layout(gtx, func() {
-									material.Body1(th, "Flat").Layout(gtx)
-								})
+				layout.Rigid(func(gtx C) D {
+					return in.Layout(gtx, func(gtx C) D {
+						return material.Clickable(gtx, flatBtn, func(gtx C) D {
+							return layout.UniformInset(unit.Dp(12)).Layout(gtx, func(gtx C) D {
+								return layout.Center.Layout(gtx, material.Body1(th, "Flat").Layout)
 							})
 						})
 					})
 				}),
 			)
 		},
-		func() {
-			material.ProgressBar(th).Layout(gtx, progress)
-		},
-		func() {
-			layout.Flex{Alignment: layout.Middle}.Layout(gtx,
-				layout.Rigid(func() {
-					material.CheckBox(th, "Checkbox").Layout(gtx, checkbox)
-				}),
-				layout.Rigid(func() {
-					layout.Inset{Left: unit.Dp(16)}.Layout(gtx, func() {
-						material.Switch(th).Layout(gtx, swtch)
-					})
+		material.ProgressBar(th, progress).Layout,
+		func(gtx C) D {
+			return layout.Flex{Alignment: layout.Middle}.Layout(gtx,
+				layout.Rigid(
+					material.CheckBox(th, checkbox, "Checkbox").Layout,
+				),
+				layout.Rigid(func(gtx C) D {
+					return layout.Inset{Left: unit.Dp(16)}.Layout(gtx,
+						material.Switch(th, swtch).Layout,
+					)
 				}),
 			)
 		},
-		func() {
-			layout.Flex{}.Layout(gtx,
-				layout.Rigid(func() {
-					material.RadioButton(th, "r1", "RadioButton1").Layout(gtx, radioButtonsGroup)
-				}),
-				layout.Rigid(func() {
-					material.RadioButton(th, "r2", "RadioButton2").Layout(gtx, radioButtonsGroup)
-				}),
-				layout.Rigid(func() {
-					material.RadioButton(th, "r3", "RadioButton3").Layout(gtx, radioButtonsGroup)
-				}),
+		func(gtx C) D {
+			return layout.Flex{}.Layout(gtx,
+				layout.Rigid(material.RadioButton(th, radioButtonsGroup, "r1", "RadioButton1").Layout),
+				layout.Rigid(material.RadioButton(th, radioButtonsGroup, "r2", "RadioButton2").Layout),
+				layout.Rigid(material.RadioButton(th, radioButtonsGroup, "r3", "RadioButton3").Layout),
 			)
 		},
 	}
 
-	list.Layout(gtx, len(widgets), func(i int) {
-		layout.UniformInset(unit.Dp(16)).Layout(gtx, widgets[i])
+	return list.Layout(gtx, len(widgets), func(gtx C, i int) D {
+		return layout.UniformInset(unit.Dp(16)).Layout(gtx, widgets[i])
 	})
 }
 
diff --git a/example/tabs/slider.go b/example/tabs/slider.go
index 08f21c90..ba192fda 100644
--- a/example/tabs/slider.go
+++ b/example/tabs/slider.go
@@ -26,13 +26,13 @@ type Slider struct {
 }
 
 // PushLeft pushes the existing widget to the left.
-func (s *Slider) PushLeft(gtx *layout.Context) { s.push = 1 }
+func (s *Slider) PushLeft() { s.push = 1 }
 
 // PushRight pushes the existing widget to the right.
-func (s *Slider) PushRight(gtx *layout.Context) { s.push = -1 }
+func (s *Slider) PushRight() { s.push = -1 }
 
 // Layout lays out widget that can be pushed.
-func (s *Slider) Layout(gtx *layout.Context, w layout.Widget) {
+func (s *Slider) Layout(gtx layout.Context, w layout.Widget) layout.Dimensions {
 	if s.push != 0 {
 		s.last, s.next = s.next, new(op.Ops)
 		s.offset = float32(s.push)
@@ -68,20 +68,20 @@ func (s *Slider) Layout(gtx *layout.Context, w layout.Widget) {
 		op.InvalidateOp{}.Add(gtx.Ops)
 	}
 
+	var dims layout.Dimensions
 	{
-		prev := gtx.Ops
 		if s.next == nil {
 			s.next = new(op.Ops)
 		}
 		s.next.Reset()
+		gtx := gtx
 		gtx.Ops = s.next
-		w()
-		gtx.Ops = prev
+		dims = w(gtx)
 	}
 
 	if s.offset == 0 {
 		op.CallOp{Ops: s.next}.Add(gtx.Ops)
-		return
+		return dims
 	}
 
 	var stack op.StackOp
@@ -92,25 +92,26 @@ func (s *Slider) Layout(gtx *layout.Context, w layout.Widget) {
 
 	if s.offset > 0 {
 		op.TransformOp{}.Offset(f32.Point{
-			X: float32(gtx.Dimensions.Size.X) * (offset - 1),
+			X: float32(dims.Size.X) * (offset - 1),
 		}).Add(gtx.Ops)
 		op.CallOp{Ops: s.last}.Add(gtx.Ops)
 
 		op.TransformOp{}.Offset(f32.Point{
-			X: float32(gtx.Dimensions.Size.X),
+			X: float32(dims.Size.X),
 		}).Add(gtx.Ops)
 		op.CallOp{Ops: s.next}.Add(gtx.Ops)
 	} else {
 		op.TransformOp{}.Offset(f32.Point{
-			X: float32(gtx.Dimensions.Size.X) * (offset + 1),
+			X: float32(dims.Size.X) * (offset + 1),
 		}).Add(gtx.Ops)
 		op.CallOp{Ops: s.last}.Add(gtx.Ops)
 
 		op.TransformOp{}.Offset(f32.Point{
-			X: float32(-gtx.Dimensions.Size.X),
+			X: float32(-dims.Size.X),
 		}).Add(gtx.Ops)
 		op.CallOp{Ops: s.next}.Add(gtx.Ops)
 	}
+	return dims
 }
 
 // smooth handles -1 to 1 with ease-in-out cubic easing func.
diff --git a/example/tabs/tabs.go b/example/tabs/tabs.go
index 50e65273..5c20ddd0 100644
--- a/example/tabs/tabs.go
+++ b/example/tabs/tabs.go
@@ -13,6 +13,7 @@ import (
 	"gioui.org/f32"
 	"gioui.org/io/system"
 	"gioui.org/layout"
+	"gioui.org/op"
 	"gioui.org/op/paint"
 	"gioui.org/unit"
 	"gioui.org/widget"
@@ -34,14 +35,14 @@ func main() {
 func loop(w *app.Window) error {
 	gofont.Register()
 	th := material.NewTheme()
-	gtx := new(layout.Context)
+	var ops op.Ops
 	for {
 		e := <-w.Events()
 		switch e := e.(type) {
 		case system.DestroyEvent:
 			return e.Err
 		case system.FrameEvent:
-			gtx.Reset(e.Queue, e.Config, e.Size)
+			gtx := layout.NewContext(&ops, e.Queue, e.Config, e.Size)
 			drawTabs(gtx, th)
 			e.Frame(gtx.Ops)
 		}
@@ -70,32 +71,38 @@ func init() {
 	}
 }
 
-func drawTabs(gtx *layout.Context, th *material.Theme) {
-	layout.Flex{Axis: layout.Vertical}.Layout(gtx,
-		layout.Rigid(func() {
-			tabs.list.Layout(gtx, len(tabs.tabs), func(tabIdx int) {
+type (
+	C = layout.Context
+	D = layout.Dimensions
+)
+
+func drawTabs(gtx layout.Context, th *material.Theme) layout.Dimensions {
+	return layout.Flex{Axis: layout.Vertical}.Layout(gtx,
+		layout.Rigid(func(gtx C) D {
+			return tabs.list.Layout(gtx, len(tabs.tabs), func(gtx C, tabIdx int) D {
 				t := &tabs.tabs[tabIdx]
 				if t.btn.Clicked(gtx) {
 					if tabs.selected < tabIdx {
-						slider.PushLeft(gtx)
+						slider.PushLeft()
 					} else if tabs.selected > tabIdx {
-						slider.PushRight(gtx)
+						slider.PushRight()
 					}
 					tabs.selected = tabIdx
 				}
 				var tabWidth int
-				layout.Stack{Alignment: layout.S}.Layout(gtx,
-					layout.Stacked(func() {
-						material.Clickable(gtx, &t.btn, func() {
-							layout.UniformInset(unit.Sp(12)).Layout(gtx, func() {
-								material.H6(th, t.Title).Layout(gtx)
-							})
+				return layout.Stack{Alignment: layout.S}.Layout(gtx,
+					layout.Stacked(func(gtx C) D {
+						dims := material.Clickable(gtx, &t.btn, func(gtx C) D {
+							return layout.UniformInset(unit.Sp(12)).Layout(gtx,
+								material.H6(th, t.Title).Layout,
+							)
 						})
-						tabWidth = gtx.Dimensions.Size.X
+						tabWidth = dims.Size.X
+						return dims
 					}),
-					layout.Stacked(func() {
+					layout.Stacked(func(gtx C) D {
 						if tabs.selected != tabIdx {
-							return
+							return layout.Dimensions{}
 						}
 						paint.ColorOp{Color: th.Color.Primary}.Add(gtx.Ops)
 						tabHeight := gtx.Px(unit.Dp(4))
@@ -105,25 +112,25 @@ func drawTabs(gtx *layout.Context, th *material.Theme) {
 								Y: float32(tabHeight),
 							},
 						}}.Add(gtx.Ops)
-						gtx.Dimensions = layout.Dimensions{
+						return layout.Dimensions{
 							Size: image.Point{X: tabWidth, Y: tabHeight},
 						}
 					}),
 				)
 			})
 		}),
-		layout.Flexed(1, func() {
-			slider.Layout(gtx, func() {
+		layout.Flexed(1, func(gtx C) D {
+			return slider.Layout(gtx, func(gtx C) D {
 				fill(gtx, dynamicColor(tabs.selected))
-				layout.Center.Layout(gtx, func() {
-					material.H1(th, fmt.Sprintf("Tab content #%d", tabs.selected+1)).Layout(gtx)
-				})
+				return layout.Center.Layout(gtx,
+					material.H1(th, fmt.Sprintf("Tab content #%d", tabs.selected+1)).Layout,
+				)
 			})
 		}),
 	)
 }
 
-func bounds(gtx *layout.Context) f32.Rectangle {
+func bounds(gtx layout.Context) f32.Rectangle {
 	cs := gtx.Constraints
 	d := cs.Min
 	return f32.Rectangle{
@@ -131,7 +138,7 @@ func bounds(gtx *layout.Context) f32.Rectangle {
 	}
 }
 
-func fill(gtx *layout.Context, col color.RGBA) {
+func fill(gtx layout.Context, col color.RGBA) {
 	dr := bounds(gtx)
 	paint.ColorOp{Color: col}.Add(gtx.Ops)
 	paint.PaintOp{Rect: dr}.Add(gtx.Ops)