example/kitchen: include example of affine transforms

Include an example of transforming the entire UI in the example.

Signed-off-by: Viktor <viktor.ogeman@gmail.com>

cmd/go.mod

@@ -3,7 +3,7 @@ module gioui.org/cmd
 go 1.13
 
 require (
-	gioui.org v0.0.0-20200619103721-0b713032fbff
+	gioui.org v0.0.0-20200621092036-cee045bf92fb
 	github.com/chromedp/cdproto v0.0.0-20191114225735-6626966fbae4
 	github.com/chromedp/chromedp v0.5.2
 	golang.org/x/image v0.0.0-20200618115811-c13761719519

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 v0.0.0-20200619103721-0b713032fbff h1:R2UG6O+TdOkC+S7jeIvcTmrKIAazXn90siDdAWnF4bg=
+gioui.org v0.0.0-20200621092036-cee045bf92fb h1:7i3eFfl0r6oeZPSQClZysU9gZwwgDScXkbrv1/CBtic=
-gioui.org v0.0.0-20200619103721-0b713032fbff/go.mod h1:jiUwifN9cRl/zmco43aAqh0aV+s9GbhG13KcD+gEpkU=
+gioui.org v0.0.0-20200621092036-cee045bf92fb/go.mod h1:jiUwifN9cRl/zmco43aAqh0aV+s9GbhG13KcD+gEpkU=
 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=

example/go.mod

@@ -3,7 +3,7 @@ module gioui.org/example
 go 1.13
 
 require (
-	gioui.org v0.0.0-20200619103721-0b713032fbff
+	gioui.org v0.0.0-20200621092036-cee045bf92fb
 	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

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 v0.0.0-20200619103721-0b713032fbff h1:R2UG6O+TdOkC+S7jeIvcTmrKIAazXn90siDdAWnF4bg=
+gioui.org v0.0.0-20200621092036-cee045bf92fb h1:7i3eFfl0r6oeZPSQClZysU9gZwwgDScXkbrv1/CBtic=
-gioui.org v0.0.0-20200619103721-0b713032fbff/go.mod h1:jiUwifN9cRl/zmco43aAqh0aV+s9GbhG13KcD+gEpkU=
+gioui.org v0.0.0-20200621092036-cee045bf92fb/go.mod h1:jiUwifN9cRl/zmco43aAqh0aV+s9GbhG13KcD+gEpkU=
 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=

example/kitchen/kitchen.go

@@ -18,6 +18,7 @@ import (
 
 	"gioui.org/app"
 	"gioui.org/app/headless"
+	"gioui.org/f32"
 	"gioui.org/font/gofont"
 	"gioui.org/io/router"
 	"gioui.org/io/system"
@@ -127,7 +128,15 @@ func loop(w *app.Window) error {
 				if *disable {
 					gtx = gtx.Disabled()
 				}
-				kitchen(gtx, th)
+				if checkbox.Changed() {
+					if checkbox.Value {
+						transformTime = e.Now
+					} else {
+						transformTime = time.Time{}
+					}
+				}
+
+				transformedKitchen(gtx, th)
 				e.Frame(gtx.Ops)
 			}
 		case p := <-progressIncrementer:
@@ -140,6 +149,30 @@ func loop(w *app.Window) error {
 	}
 }
 
+func transformedKitchen(gtx layout.Context, th *material.Theme) layout.Dimensions {
+	if !transformTime.IsZero() {
+		dt := float32(gtx.Now.Sub(transformTime).Seconds())
+		angle := dt * .1
+		op.InvalidateOp{}.Add(gtx.Ops)
+		defer op.Push(gtx.Ops).Pop()
+		tr := f32.Affine2D{}
+		tr = tr.Rotate(f32.Pt(300, 20), -angle)
+		scale := 1.0 - dt*.5
+		if scale < 0.5 {
+			scale = 0.5
+		}
+		tr = tr.Scale(f32.Pt(300, 20), f32.Pt(scale, scale))
+		offset := dt * 50
+		if offset > 200 {
+			offset = 200
+		}
+		tr = tr.Offset(f32.Pt(0, offset))
+		op.Affine(tr).Add(gtx.Ops)
+	}
+
+	return kitchen(gtx, th)
+}
+
 var (
 	editor     = new(widget.Editor)
 	lineEditor = &widget.Editor{
@@ -163,6 +196,7 @@ var (
 	icon                *widget.Icon
 	checkbox            = new(widget.Bool)
 	swtch               = new(widget.Bool)
+	transformTime       time.Time
 )
 
 type (
@@ -268,7 +302,7 @@ func kitchen(gtx layout.Context, th *material.Theme) layout.Dimensions {
 		func(gtx C) D {
 			return layout.Flex{Alignment: layout.Middle}.Layout(gtx,
 				layout.Rigid(
-					material.CheckBox(th, checkbox, "Checkbox").Layout,
+					material.CheckBox(th, checkbox, "Transform").Layout,
 				),
 				layout.Rigid(func(gtx C) D {
 					return layout.Inset{Left: unit.Dp(16)}.Layout(gtx,