// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"bytes"
	"context"
	"fmt"
	"image"
	"image/color"
	"math"
	"net/netip"
	"time"

	"gioui.org/f32"
	"gioui.org/font/opentype"
	"gioui.org/io/pointer"
	"gioui.org/io/system"
	"gioui.org/layout"
	"gioui.org/op"
	"gioui.org/op/clip"
	"gioui.org/op/paint"
	"gioui.org/text"
	"gioui.org/unit"
	"gioui.org/widget"
	"gioui.org/widget/material"
	qrcode "github.com/skip2/go-qrcode"
	"golang.org/x/exp/shiny/materialdesign/icons"
	"tailscale.com/client/tailscale/apitype"
	"tailscale.com/ipn"
	"tailscale.com/tailcfg"
	"tailscale.com/version"

	_ "embed"

	"eliasnaur.com/font/roboto/robotobold"
	"eliasnaur.com/font/roboto/robotoregular"

	_ "image/png"
)

type UI struct {
	theme *material.Theme
	store *stateStore

	// root is the scrollable list of the main UI.
	root layout.List
	// enabled is the switch for enabling or disabling the VPN.
	enabled widget.Bool
	search  widget.Editor

	exitLAN widget.Bool

	// webSigin is the button for the web-based sign-in flow.
	webSignin widget.Clickable

	// googleSignin is the button for native Google Sign-in.
	googleSignin widget.Clickable

	// openExitDialog opens the exit node picker.
	openExitDialog widget.Clickable

	signinType signinType

	setLoginServer    bool
	loginServer       widget.Editor
	loginServerSave   widget.Clickable
	loginServerCancel widget.Clickable

	self  widget.Clickable
	peers []widget.Clickable

	// exitDialog is state for the exit node dialog.
	exitDialog struct {
		show    bool
		dismiss Dismiss
		exits   widget.Enum
		list    layout.List
	}

	runningExit bool // are we an exit node now?

	qr struct {
		show bool
		op   paint.ImageOp
	}

	intro struct {
		list  layout.List
		start widget.Clickable
		show  bool
	}

	menu struct {
		open          widget.Clickable
		dismiss       Dismiss
		show          bool
		showHistory   []showChange
		showDebugMenu bool

		useLoginServer widget.Clickable
		copy           widget.Clickable
		reauth         widget.Clickable
		bug            widget.Clickable
		beExit         widget.Clickable
		exits          widget.Clickable
		about          widget.Clickable
		logout         widget.Clickable
	}

	// The current pop-up message, if any
	message struct {
		text string
		// t0 is the time when the most recent message appeared.
		t0 time.Time
	}

	shareDialog struct {
		show    bool
		dismiss Dismiss
		list    layout.List
		// peers are the nodes ready to receive files.
		targets []shareTarget
		loaded  bool
		error   error
	}

	// aboutDialog is state for the about dialog.
	aboutDialog struct {
		show    bool
		dismiss Dismiss
	}

	// ossLicenses is the button to show the OSS licenses.
	ossLicenses widget.Clickable

	icons struct {
		search     *widget.Icon
		more       *widget.Icon
		exitStatus *widget.Icon
		done       *widget.Icon
		error      *widget.Icon
		logo       paint.ImageOp
		google     paint.ImageOp
	}
}

type shareTarget struct {
	btn     widget.Clickable
	target  *apitype.FileTarget
	info    FileSendInfo
	cancel  func()
	updates <-chan FileSendInfo
}

type signinType uint8

// An UIPeer is either a peer or a section header
// with the user information.
type UIPeer struct {
	// Owner of the peer.
	Owner tailcfg.UserID
	// Name is the owner's name in all caps (for section headers).
	Name string
	// Peer is nil for section headers.
	Peer *tailcfg.Node
}

// menuItem describes an item in a popup menu.
type menuItem struct {
	title string
	btn   *widget.Clickable
}

const (
	headerColor = 0x496495
	infoColor   = 0x3a517b
	white       = 0xffffff
)

const (
	keyShowIntro = "ui.showintro"
)

const (
	noSignin signinType = iota
	webSignin
	googleSignin
)

type (
	C = layout.Context
	D = layout.Dimensions
)

var (
	//go:embed tailscale.png
	tailscaleLogo []byte
	//go:embed google.png
	googleLogo []byte
)

func newUI(store *stateStore) (*UI, error) {
	searchIcon, err := widget.NewIcon(icons.ActionSearch)
	if err != nil {
		return nil, err
	}
	moreIcon, err := widget.NewIcon(icons.NavigationMoreVert)
	if err != nil {
		return nil, err
	}
	exitStatus, err := widget.NewIcon(icons.NavigationMenu)
	if err != nil {
		return nil, err
	}
	doneIcon, err := widget.NewIcon(icons.ActionCheckCircle)
	if err != nil {
		return nil, err
	}
	errorIcon, err := widget.NewIcon(icons.AlertErrorOutline)
	if err != nil {
		return nil, err
	}
	logo, _, err := image.Decode(bytes.NewReader(tailscaleLogo))
	if err != nil {
		return nil, err
	}
	google, _, err := image.Decode(bytes.NewReader(googleLogo))
	if err != nil {
		return nil, err
	}
	face, err := opentype.Parse(robotoregular.TTF)
	if err != nil {
		panic(fmt.Sprintf("failed to parse font: %v", err))
	}
	faceBold, err := opentype.Parse(robotobold.TTF)
	if err != nil {
		panic(fmt.Sprintf("failed to parse font: %v", err))
	}
	fonts := []text.FontFace{
		{Font: text.Font{Typeface: "Roboto"}, Face: face},
		{Font: text.Font{Typeface: "Roboto", Weight: text.Bold}, Face: faceBold},
	}
	ui := &UI{
		theme: material.NewTheme(fonts),
		store: store,
	}
	ui.intro.show, _ = store.ReadBool(keyShowIntro, true)
	ui.icons.search = searchIcon
	ui.icons.more = moreIcon
	ui.icons.exitStatus = exitStatus
	ui.icons.done = doneIcon
	ui.icons.error = errorIcon
	ui.icons.logo = paint.NewImageOp(logo)
	ui.icons.google = paint.NewImageOp(google)
	ui.root.Axis = layout.Vertical
	ui.intro.list.Axis = layout.Vertical
	ui.search.SingleLine = true
	ui.loginServer.SingleLine = true
	ui.exitDialog.list.Axis = layout.Vertical
	ui.shareDialog.list.Axis = layout.Vertical

	// If they've ever set the control plane, give them the debug menu right away.
	if v, _ := ui.store.ReadString(customLoginServerPrefKey, ""); v != "" {
		ui.menu.showDebugMenu = true
	}

	return ui, nil
}

func mulAlpha(c color.NRGBA, alpha uint8) color.NRGBA {
	c.A = uint8(uint32(c.A) * uint32(alpha) / 0xff)
	return c
}

func (ui *UI) onBack() bool {
	b := ui.activeDialog()
	if b == nil {
		return false
	}
	*b = false
	return true
}

func (ui *UI) activeDialog() *bool {
	switch {
	case ui.qr.show:
		return &ui.qr.show
	case ui.menu.show:
		return &ui.menu.show
	case ui.shareDialog.show:
		return &ui.shareDialog.show
	case ui.exitDialog.show:
		return &ui.exitDialog.show
	case ui.aboutDialog.show:
		return &ui.aboutDialog.show
	}
	return nil
}

type showChange struct {
	at    time.Time
	shown bool
}

func (ui *UI) setMenuShown(v bool) {
	if v == ui.menu.show {
		return
	}
	ui.menu.show = v

	now := time.Now()
	const recent = 5 * time.Second
	recentHistory := ui.menu.showHistory[:0]
	for _, hi := range ui.menu.showHistory {
		if now.Sub(hi.at) < recent {
			recentHistory = append(recentHistory, hi)
		}
	}
	ui.menu.showHistory = append(recentHistory, showChange{
		at:    now,
		shown: v,
	})
	if len(ui.menu.showHistory) >= 6 {
		ui.menu.showDebugMenu = true
	}
}

func (ui *UI) layout(gtx layout.Context, sysIns system.Insets, state *clientState) []UIEvent {
	// "Get started".
	if ui.intro.show {
		if ui.intro.start.Clicked() {
			ui.store.WriteBool(keyShowIntro, false)
			ui.intro.show = false
		}
		ui.layoutIntro(gtx, sysIns)
		return nil
	}

	var events []UIEvent

	if ui.enabled.Changed() {
		events = append(events, ConnectEvent{Enable: ui.enabled.Value})
	}

	for _, e := range ui.search.Events() {
		if _, ok := e.(widget.ChangeEvent); ok {
			events = append(events, SearchEvent{Query: ui.search.Text()})
			break
		}
	}
	for ui.menu.open.Clicked() {
		ui.setMenuShown(!ui.menu.show)
	}

	netmap := state.backend.NetworkMap
	var (
		localName, localAddr string
		expiry               time.Time
		userID               tailcfg.UserID
		exitID               tailcfg.StableNodeID
	)
	if netmap != nil {
		userID = netmap.User
		expiry = netmap.Expiry
		localName = netmap.SelfNode.DisplayName(false)
		if addrs := netmap.Addresses; len(addrs) > 0 {
			localAddr = addrs[0].Addr().String()
		}
	}
	if p := state.backend.Prefs; p != nil {
		exitID = p.ExitNodeID
	}
	if d := &ui.exitDialog; d.show {
		if newID := tailcfg.StableNodeID(d.exits.Value); newID != exitID {
			d.show = false
			events = append(events, RouteAllEvent{newID})
		}
	} else {
		d.exits.Value = string(exitID)
	}
	if ui.exitLAN.Changed() {
		events = append(events, ExitAllowLANEvent(ui.exitLAN.Value))
	}

	if ui.googleSignin.Clicked() {
		ui.signinType = googleSignin
		events = append(events, GoogleAuthEvent{})
	}

	if ui.webSignin.Clicked() {
		ui.signinType = webSignin
		events = append(events, WebAuthEvent{})
	}

	if ui.loginServerSave.Clicked() {
		text := ui.loginServer.Text()
		ui.showMessage(gtx, "Login server saved")
		events = append(events, SetLoginServerEvent{URL: text})
		ui.setLoginServer = false
	}
	if ui.loginServerCancel.Clicked() {
		ui.setLoginServer = false
	}

	if ui.menuClicked(&ui.menu.useLoginServer) {
		ui.setLoginServer = true
		savedLoginServer, _ := ui.store.ReadString(customLoginServerPrefKey, "")
		ui.loginServer.SetText(savedLoginServer)
	}

	if ui.menuClicked(&ui.menu.copy) && localAddr != "" {
		events = append(events, CopyEvent{Text: localAddr})
		ui.showCopied(gtx, localAddr)
	}

	if ui.menuClicked(&ui.menu.reauth) {
		events = append(events, ReauthEvent{})
	}

	if ui.menuClicked(&ui.menu.bug) {
		events = append(events, BugEvent{})
		ui.showCopied(gtx, "bug report marker to clipboard")
	}

	if ui.menuClicked(&ui.menu.beExit) {
		ui.runningExit = !ui.runningExit
		events = append(events, BeExitNodeEvent(ui.runningExit))
		if ui.runningExit {
			ui.showMessage(gtx, "Running exit node")
		} else {
			ui.showMessage(gtx, "Stopped running exit node")
		}
	}

	if ui.menuClicked(&ui.menu.exits) || ui.openExitDialog.Clicked() {
		ui.exitDialog.show = true
	}

	if ui.menuClicked(&ui.menu.about) {
		ui.aboutDialog.show = true
	}

	if ui.ossLicenses.Clicked() {
		events = append(events, OSSLicensesEvent{})
	}

	if ui.menuClicked(&ui.menu.logout) {
		events = append(events, LogoutEvent{})
	}

	for i := range ui.shareDialog.targets {
		t := &ui.shareDialog.targets[i]
		select {
		case t.info = <-t.updates:
		default:
		}
		if !t.btn.Clicked() {
			continue
		}
		switch t.info.State {
		case FileSendTransferring, FileSendConnecting:
			t.cancel()
			t.info.State = FileSendNotStarted
			t.updates = nil
			continue
		}
		t.info = FileSendInfo{
			State: FileSendConnecting,
		}
		ctx, cancel := context.WithCancel(context.Background())
		t.cancel = cancel
		updates := make(chan FileSendInfo, 1)
		t.updates = updates
		events = append(events, FileSendEvent{
			Target:  t.target,
			Context: ctx,
			Updates: func(info FileSendInfo) {
				select {
				case <-updates:
				default:
				}
				updates <- info
			},
		})
	}

	for len(ui.peers) < len(state.Peers) {
		ui.peers = append(ui.peers, widget.Clickable{})
	}
	if max := len(state.Peers); len(ui.peers) > max {
		ui.peers = ui.peers[:max]
	}

	const numHeaders = 6
	n := numHeaders + len(state.Peers)
	needsLogin := state.backend.State == ipn.NeedsLogin
	if !needsLogin {
		ui.qr.show = false
	}
	rootGtx := gtx
	if ui.activeDialog() != nil {
		rootGtx.Queue = nil
	}
	ui.root.Layout(rootGtx, n, func(gtx C, idx int) D {
		var in layout.Inset
		if idx == n-1 {
			// The last list element includes the bottom system
			// inset.
			in.Bottom = sysIns.Bottom
		}
		return in.Layout(gtx, func(gtx C) D {
			switch idx {
			case 0:
				return ui.layoutTop(gtx, sysIns, &state.backend)
			case 1:
				if netmap == nil || state.backend.State < ipn.Stopped {
					return D{}
				}
				for ui.self.Clicked() {
					events = append(events, CopyEvent{Text: localAddr})
					ui.showCopied(gtx, localAddr)
				}
				return ui.layoutLocal(gtx, sysIns, localName, localAddr)
			case 2:
				return ui.layoutExitStatus(gtx, &state.backend)
			case 3:
				if state.backend.State < ipn.Stopped {
					return D{}
				}
				return ui.layoutSearchbar(gtx, sysIns)
			case 4:
				if !needsLogin {
					return D{}
				}
				return ui.layoutSignIn(gtx, &state.backend)
			case 5:
				// Formerly "No internet connection", which has been removed.
				return D{}
			default:
				if needsLogin {
					return D{}
				}
				pidx := idx - numHeaders
				p := &state.Peers[pidx]
				if p.Peer == nil {
					name := p.Name
					if p.Owner == userID {
						name = "MY DEVICES"
					}
					return ui.layoutSection(gtx, sysIns, name)
				} else {
					clk := &ui.peers[pidx]
					if clk.Clicked() {
						if addrs := p.Peer.Addresses; len(addrs) > 0 {
							a := addrs[0].Addr().String()
							events = append(events, CopyEvent{Text: a})
							ui.showCopied(gtx, a)
						}
					}
					return ui.layoutPeer(gtx, sysIns, p, userID, clk)
				}
			}
		})
	})

	ui.layoutExitNodeDialog(gtx, sysIns, state.backend.Exits)

	ui.layoutShareDialog(gtx, sysIns)

	ui.layoutAboutDialog(gtx, sysIns)

	// Popup messages.
	ui.layoutMessage(gtx, sysIns)

	// 3-dots menu.
	if ui.menu.show {
		ui.layoutMenu(gtx, sysIns, expiry, exitID != "" || len(state.backend.Exits) > 0, needsLogin)
	}

	if ui.qr.show {
		ui.layoutQR(gtx, sysIns)
	}

	return events
}

func (ui *UI) layoutQR(gtx layout.Context, sysIns system.Insets) layout.Dimensions {
	fill{rgb(0x232323)}.Layout(gtx, gtx.Constraints.Max)
	return layout.Center.Layout(gtx, func(gtx C) D {
		return drawImage(gtx, ui.qr.op, unit.Dp(300))
	})
}

func (ui *UI) FillShareDialog(targets []*apitype.FileTarget, err error) {
	ui.shareDialog.error = err
	ui.shareDialog.loaded = true
	targetSet := make(map[tailcfg.NodeID]int)
	if ui.shareDialog.show {
		// Update rather than replace list.
		for i, t := range ui.shareDialog.targets {
			targetSet[t.target.Node.ID] = i
		}
	} else {
		ui.shareDialog.targets = nil
	}
	for _, t := range targets {
		if i, ok := targetSet[t.Node.ID]; ok {
			ui.shareDialog.targets[i].target = t
		} else {
			ui.shareDialog.targets = append(ui.shareDialog.targets, shareTarget{target: t})
		}
	}
}

func (ui *UI) ShowShareDialog() {
	ui.shareDialog.show = true
}

func (ui *UI) ShowMessage(msg string) {
	ui.message.text = msg
	ui.message.t0 = time.Now()
}

func (ui *UI) ShowQRCode(url string) {
	ui.qr.show = true
	q, err := qrcode.New(url, qrcode.Medium)
	if err != nil {
		fatalErr(err)
		return
	}
	ui.qr.op = paint.NewImageOp(q.Image(512))
}

// Dismiss is a widget that detects pointer presses.
type Dismiss struct {
}

func (d *Dismiss) Add(gtx layout.Context, color color.NRGBA) {
	defer clip.Rect(image.Rectangle{Max: gtx.Constraints.Min}).Push(gtx.Ops).Pop()
	pointer.InputOp{Tag: d, Types: pointer.Press}.Add(gtx.Ops)
	paint.Fill(gtx.Ops, color)
}

func (d *Dismiss) Dismissed(gtx layout.Context) bool {
	for _, e := range gtx.Events(d) {
		if e, ok := e.(pointer.Event); ok {
			if e.Type == pointer.Press {
				return true
			}
		}
	}
	return false
}

func (ui *UI) layoutExitStatus(gtx layout.Context, state *BackendState) layout.Dimensions {
	var bg color.NRGBA
	var text string
	switch state.ExitStatus {
	case ExitNone:
		return D{}
	case ExitOffline:
		text = "Exit node offline"
		bg = rgb(0xc65835)
	case ExitOnline:
		text = "Using exit node"
		bg = rgb(0x338b51)
	}
	return material.Clickable(gtx, &ui.openExitDialog, func(gtx C) D {
		gtx.Constraints.Min.X = gtx.Constraints.Max.X
		return layout.Stack{}.Layout(gtx,
			layout.Expanded(func(gtx layout.Context) layout.Dimensions {
				sz := image.Point{
					X: gtx.Constraints.Min.X,
					Y: gtx.Constraints.Min.Y,
				}
				defer clip.Rect(image.Rectangle{Max: sz}).Push(gtx.Ops).Pop()
				paint.ColorOp{Color: bg}.Add(gtx.Ops)
				paint.PaintOp{}.Add(gtx.Ops)
				return layout.Dimensions{Size: sz}
			}),
			layout.Stacked(func(gtx layout.Context) layout.Dimensions {
				return layout.Inset{
					Top:    unit.Dp(12),
					Bottom: unit.Dp(12),
					Right:  unit.Dp(24),
					Left:   unit.Dp(24),
				}.Layout(gtx, func(gtx C) D {
					return layout.Flex{Alignment: layout.Middle}.Layout(gtx,
						layout.Flexed(1, func(gtx C) D {
							return layout.Flex{Axis: layout.Vertical}.Layout(gtx,
								layout.Rigid(func(gtx C) D {
									lbl := material.Body2(ui.theme, text)
									lbl.Color = rgb(white)
									return lbl.Layout(gtx)
								}),
								layout.Rigid(func(gtx C) D {
									node := material.Body2(ui.theme, state.Exit.Label)
									node.Color = argb(0x88ffffff)
									return node.Layout(gtx)
								}),
							)
						}),
						layout.Rigid(func(gtx C) D {
							return ui.icons.exitStatus.Layout(gtx, rgb(white))
						}),
					)
				})
			}),
		)
	})
}

// layoutSignIn lays out the sign in button(s).
func (ui *UI) layoutSignIn(gtx layout.Context, state *BackendState) layout.Dimensions {
	return layout.Inset{Top: unit.Dp(48), Left: unit.Dp(48), Right: unit.Dp(48)}.Layout(gtx, func(gtx C) D {
		const (
			textColor = 0x555555
		)

		border := widget.Border{Color: rgb(textColor), CornerRadius: unit.Dp(4), Width: unit.Dp(1)}

		if ui.setLoginServer {
			return layout.Flex{Axis: layout.Vertical, Alignment: layout.Middle}.Layout(gtx,
				layout.Rigid(func(gtx C) D {
					return layout.Inset{Bottom: unit.Dp(16)}.Layout(gtx, func(gtx C) D {
						return Background{Color: rgb(0xe3e2ea), CornerRadius: unit.Dp(8)}.Layout(gtx, func(gtx C) D {
							return layout.UniformInset(unit.Dp(8)).Layout(gtx, func(gtx C) D {
								return layout.Flex{Alignment: layout.Middle}.Layout(gtx,
									layout.Flexed(1,
										material.Editor(ui.theme, &ui.loginServer, "https://controlplane.tailscale.com").Layout,
									),
								)
							})
						})
					})
				}),
				layout.Rigid(func(gtx C) D {
					return layout.Inset{Bottom: unit.Dp(16)}.Layout(gtx, func(gtx C) D {
						return border.Layout(gtx, func(gtx C) D {
							button := material.Button(ui.theme, &ui.loginServerSave, "Save")
							button.Background = color.NRGBA{} // transparent
							button.Color = rgb(textColor)
							return button.Layout(gtx)
						})
					})
				}),
				layout.Rigid(func(gtx C) D {
					return border.Layout(gtx, func(gtx C) D {
						button := material.Button(ui.theme, &ui.loginServerCancel, "Cancel")
						button.Background = color.NRGBA{} // transparent
						button.Color = rgb(textColor)
						return button.Layout(gtx)
					})
				}),
			)
		}

		return layout.Flex{Axis: layout.Vertical, Alignment: layout.Middle}.Layout(gtx,
			layout.Rigid(func(gtx C) D {
				if !googleSignInEnabled() {
					return D{}
				}
				return layout.Inset{Bottom: unit.Dp(16)}.Layout(gtx, func(gtx C) D {
					signin := material.ButtonLayout(ui.theme, &ui.googleSignin)
					signin.Background = color.NRGBA{} // transparent

					return ui.withLoader(gtx, ui.signinType == googleSignin, func(gtx C) D {
						return border.Layout(gtx, func(gtx C) D {
							if ui.signinType != noSignin {
								gtx.Queue = nil
							}
							return signin.Layout(gtx, func(gtx C) D {
								gtx.Constraints.Max.Y = gtx.Dp(unit.Dp(48))
								return layout.Flex{Alignment: layout.Middle}.Layout(gtx,
									layout.Rigid(func(gtx C) D {
										return layout.Inset{Right: unit.Dp(4)}.Layout(gtx, func(gtx C) D {
											return drawImage(gtx, ui.icons.google, unit.Dp(16))
										})
									}),
									layout.Rigid(func(gtx C) D {
										return layout.Inset{Top: unit.Dp(10), Bottom: unit.Dp(10)}.Layout(gtx, func(gtx C) D {
											l := material.Body2(ui.theme, "Sign in with Google")
											l.Color = rgb(textColor)
											return l.Layout(gtx)
										})
									}),
								)
							})
						})
					})
				})
			}),
			layout.Rigid(func(gtx C) D {
				label := "Sign in with other"
				if !googleSignInEnabled() {
					label = "Sign in"
				}
				return ui.withLoader(gtx, ui.signinType == webSignin, func(gtx C) D {
					return border.Layout(gtx, func(gtx C) D {
						if ui.signinType != noSignin {
							gtx.Queue = nil
						}
						signin := material.Button(ui.theme, &ui.webSignin, label)
						signin.Background = color.NRGBA{} // transparent
						signin.Color = rgb(textColor)
						return signin.Layout(gtx)
					})
				})
			}),
		)
	})
}

func (ui *UI) withLoader(gtx layout.Context, loading bool, w layout.Widget) layout.Dimensions {
	cons := gtx.Constraints
	return layout.Stack{Alignment: layout.W}.Layout(gtx,
		layout.Stacked(func(gtx C) D {
			gtx.Constraints = cons
			return w(gtx)
		}),
		layout.Stacked(func(gtx C) D {
			if !loading {
				return D{}
			}
			return layout.Inset{Left: unit.Dp(16)}.Layout(gtx, func(gtx C) D {
				gtx.Constraints.Min = image.Point{
					X: gtx.Dp(unit.Dp(16)),
				}
				return material.Loader(ui.theme).Layout(gtx)
			})
		}),
	)
}

// layoutIntro lays out the intro page with the logo and terms.
func (ui *UI) layoutIntro(gtx layout.Context, sysIns system.Insets) {
	fill{rgb(0x232323)}.Layout(gtx, gtx.Constraints.Max)
	ui.intro.list.Layout(gtx, 1, func(gtx C, idx int) D {
		return layout.Flex{Axis: layout.Vertical}.Layout(gtx,
			// 9 dot logo.
			layout.Rigid(func(gtx C) D {
				return layout.Inset{Top: unit.Dp(80), Bottom: unit.Dp(48)}.Layout(gtx, func(gtx C) D {
					return layout.N.Layout(gtx, func(gtx C) D {
						sz := gtx.Dp(unit.Dp(72))
						drawLogo(gtx.Ops, sz)
						return layout.Dimensions{Size: image.Pt(sz, sz)}
					})
				})
			}),
			// "tailscale".
			layout.Rigid(func(gtx C) D {
				return layout.N.Layout(gtx, func(gtx C) D {
					return drawImage(gtx, ui.icons.logo, unit.Dp(200))
				})
			}),
			// Terms.
			layout.Rigid(func(gtx C) D {
				return layout.Inset{
					Top:   unit.Dp(48),
					Left:  unit.Dp(32),
					Right: unit.Dp(32),
				}.Layout(gtx, func(gtx C) D {
					terms := material.Body2(ui.theme, termsText)
					terms.Color = rgb(0xbfbfbf)
					terms.Alignment = text.Middle
					return terms.Layout(gtx)
				})
			}),
			// "Get started".
			layout.Rigid(func(gtx C) D {
				return layout.Inset{
					Top:    unit.Dp(16),
					Left:   unit.Dp(16),
					Right:  unit.Dp(16),
					Bottom: sysIns.Bottom,
				}.Layout(gtx, func(gtx C) D {
					start := material.Button(ui.theme, &ui.intro.start, "Get Started")
					start.Inset = layout.UniformInset(unit.Dp(16))
					start.CornerRadius = unit.Dp(16)
					start.Background = rgb(0x496495)
					start.TextSize = unit.Sp(20)
					return start.Layout(gtx)
				})
			}),
		)
	})
}

// menuClicked is like btn.Clicked, but also closes the menu if true.
func (ui *UI) menuClicked(btn *widget.Clickable) bool {
	cl := btn.Clicked()
	if cl {
		ui.setMenuShown(false)
	}
	return cl
}

// layoutShareDialog lays out the file sharing dialog shown on file send intents (ACTION_SEND, ACTION_SEND_MULTIPLE).
func (ui *UI) layoutShareDialog(gtx layout.Context, sysIns system.Insets) {
	d := &ui.shareDialog
	if d.dismiss.Dismissed(gtx) {
		ui.shareDialog.show = false
	}
	if !d.show {
		return
	}
	d.dismiss.Add(gtx, argb(0x66000000))
	layout.Inset{
		Top:    sysIns.Top + unit.Dp(16),
		Right:  sysIns.Right + unit.Dp(16),
		Bottom: sysIns.Bottom + unit.Dp(16),
		Left:   sysIns.Left + unit.Dp(16),
	}.Layout(gtx, func(gtx C) D {
		return layout.Center.Layout(gtx, func(gtx C) D {
			gtx.Constraints.Min.X = gtx.Dp(unit.Dp(250))
			gtx.Constraints.Max.X = gtx.Constraints.Min.X
			return layoutDialog(gtx, func(gtx C) D {
				return layout.Flex{Axis: layout.Vertical}.Layout(gtx,
					layout.Rigid(func(gtx C) D {
						// Header.
						d := layout.Inset{
							Top:    unit.Dp(16),
							Right:  unit.Dp(20),
							Left:   unit.Dp(20),
							Bottom: unit.Dp(16),
						}.Layout(gtx, func(gtx C) D {
							l := material.Body1(ui.theme, "Share via Tailscale")
							l.Font.Weight = text.Bold
							return l.Layout(gtx)
						})
						// Swallow clicks to title.
						var c widget.Clickable
						gtx.Queue = nil
						return c.Layout(gtx, func(gtx C) D { return d })
					}),
					layout.Rigid(func(gtx C) D {
						if d.loaded {
							return D{}
						}
						return layout.UniformInset(unit.Dp(50)).Layout(gtx, func(gtx C) D {
							return layout.Center.Layout(gtx, func(gtx C) D {
								sz := gtx.Dp(unit.Dp(32))
								gtx.Constraints.Min = image.Pt(sz, sz)
								gtx.Constraints.Max = gtx.Constraints.Min
								return material.Loader(ui.theme).Layout(gtx)
							})
						})
					}),
					layout.Rigid(func(gtx C) D {
						if d.error == nil {
							return D{}
						}
						sz := gtx.Dp(unit.Dp(50))
						gtx.Constraints.Min.Y = sz
						return layout.UniformInset(unit.Dp(20)).Layout(gtx, func(gtx C) D {
							return layout.W.Layout(gtx, func(gtx C) D {
								return material.Body2(ui.theme, d.error.Error()).Layout(gtx)
							})
						})
					}),
					layout.Flexed(1, func(gtx C) D {
						gtx.Constraints.Min.Y = 0
						return d.list.Layout(gtx, len(d.targets), func(gtx C, idx int) D {
							node := &d.targets[idx]
							target := node.target.Node
							lbl := target.ComputedName
							offline := target.Online != nil && !*target.Online
							if offline {
								lbl = lbl + " (offline)"
							}
							w := material.Body2(ui.theme, lbl)
							if offline {
								w.Color = rgb(0xbbbbbb)
								gtx.Queue = nil
							}
							return material.Clickable(gtx, &node.btn, func(gtx C) D {
								return layout.UniformInset(unit.Dp(16)).Layout(gtx, func(gtx C) D {
									return layout.Flex{Alignment: layout.Middle}.Layout(gtx,
										layout.Flexed(1, w.Layout),
										layout.Rigid(func(gtx C) D {
											sz := gtx.Dp(unit.Dp(16))
											gtx.Constraints.Min = image.Pt(sz, sz)
											switch node.info.State {
											case FileSendConnecting:
												return material.Loader(ui.theme).Layout(gtx)
											case FileSendTransferring:
												return material.ProgressCircle(ui.theme, float32(node.info.Progress)).Layout(gtx)
											case FileSendFailed:
												return ui.icons.error.Layout(gtx, rgb(0xcc6539))
											case FileSendComplete:
												return ui.icons.done.Layout(gtx, ui.theme.Palette.ContrastBg)
											default:
												return D{}
											}
										}),
									)
								})
							})
						})
					}),
				)
			})
		})
	})
}

// layoutExitNodeDialog lays out the exit node selection dialog.
func (ui *UI) layoutExitNodeDialog(gtx layout.Context, sysIns system.Insets, exits []Peer) {
	d := &ui.exitDialog
	if d.dismiss.Dismissed(gtx) {
		d.show = false
	}
	if !d.show {
		return
	}
	d.dismiss.Add(gtx, argb(0x66000000))
	layout.Inset{
		Top:    sysIns.Top + unit.Dp(16),
		Right:  sysIns.Right + unit.Dp(16),
		Bottom: sysIns.Bottom + unit.Dp(16),
		Left:   sysIns.Left + unit.Dp(16),
	}.Layout(gtx, func(gtx C) D {
		return layout.Center.Layout(gtx, func(gtx C) D {
			gtx.Constraints.Min.X = gtx.Dp(unit.Dp(250))
			gtx.Constraints.Max.X = gtx.Constraints.Min.X
			return layoutDialog(gtx, func(gtx C) D {
				return layout.Flex{Axis: layout.Vertical}.Layout(gtx,
					layout.Rigid(func(gtx C) D {
						// Header.
						return layout.Inset{
							Top:    unit.Dp(16),
							Right:  unit.Dp(20),
							Left:   unit.Dp(20),
							Bottom: unit.Dp(16),
						}.Layout(gtx, func(gtx C) D {
							l := material.Body1(ui.theme, "Use exit node...")
							l.Font.Weight = text.Bold
							return l.Layout(gtx)
						})
					}),
					layout.Flexed(1, func(gtx C) D {
						gtx.Constraints.Min.Y = 0
						// Add "none" exit node, then "Allow LAN" checkbox, then the exit nodes.
						n := len(exits) + 2
						return d.list.Layout(gtx, n, func(gtx C, idx int) D {
							if idx == 0 {
								btn := material.CheckBox(ui.theme, &ui.exitLAN, "Allow LAN access")
								return layout.Inset{
									Right:  unit.Dp(16),
									Left:   unit.Dp(16),
									Bottom: unit.Dp(16),
								}.Layout(gtx, btn.Layout)
							}
							node := Peer{Label: "None", Online: true}
							if idx >= 2 {
								node = exits[idx-2]
							}
							lbl := node.Label
							if !node.Online {
								lbl = lbl + " (offline)"
							}
							btn := material.RadioButton(ui.theme, &d.exits, string(node.ID), lbl)
							if !node.Online {
								btn.Color = rgb(0xbbbbbb)
								btn.IconColor = btn.Color
							}
							return layout.Inset{
								Right:  unit.Dp(16),
								Left:   unit.Dp(16),
								Bottom: unit.Dp(16),
							}.Layout(gtx, btn.Layout)
						})
					}),
				)
			})
		})
	})
}

// layoutAboutDialog lays out the about dialog.
func (ui *UI) layoutAboutDialog(gtx layout.Context, sysIns system.Insets) {
	d := &ui.aboutDialog
	if d.dismiss.Dismissed(gtx) {
		d.show = false
	}
	if !d.show {
		return
	}
	d.dismiss.Add(gtx, argb(0x66000000))
	layout.Inset{
		Top:    sysIns.Top + unit.Dp(16),
		Right:  sysIns.Right + unit.Dp(16),
		Bottom: sysIns.Bottom + unit.Dp(16),
		Left:   sysIns.Left + unit.Dp(16),
	}.Layout(gtx, func(gtx C) D {
		return layout.Center.Layout(gtx, func(gtx C) D {
			gtx.Constraints.Min.X = gtx.Dp(unit.Dp(250))
			gtx.Constraints.Max.X = gtx.Constraints.Min.X
			return layoutDialog(gtx, func(gtx C) D {
				return layout.Flex{Axis: layout.Vertical}.Layout(gtx,
					layout.Rigid(func(gtx C) D {
						// Header.
						return layout.Inset{
							Top:    unit.Dp(16),
							Right:  unit.Dp(20),
							Left:   unit.Dp(20),
							Bottom: unit.Dp(16),
						}.Layout(gtx, func(gtx C) D {
							l := material.Body1(ui.theme, "About")
							l.Font.Weight = text.Bold
							return l.Layout(gtx)
						})
					}),
					layout.Rigid(func(gtx C) D {
						return layout.UniformInset(unit.Dp(16)).Layout(gtx, func(gtx C) D {
							return material.Body1(ui.theme, "version "+version.Short()).Layout(gtx)
						})
					}),
					layout.Rigid(func(gtx C) D {
						return material.Clickable(gtx, &ui.ossLicenses, func(gtx C) D {
							return layout.UniformInset(unit.Dp(16)).Layout(gtx, func(gtx C) D {
								return material.Body1(ui.theme, "Open Source Licenses").Layout(gtx)
							})
						})
					}),
				)
			})
		})
	})
}

func layoutMenu(th *material.Theme, gtx layout.Context, items []menuItem, header layout.Widget) layout.Dimensions {
	return layoutDialog(gtx, func(gtx C) D {
		// Lay out menu items twice; once for
		// measuring the widest item, once for actual layout.
		var maxWidth int
		var minWidth int
		children := []layout.FlexChild{
			layout.Rigid(func(gtx C) D {
				return layout.Inset{
					Top:    unit.Dp(16),
					Right:  unit.Dp(16),
					Left:   unit.Dp(16),
					Bottom: unit.Dp(4),
				}.Layout(gtx, func(gtx C) D {
					gtx.Constraints.Min.X = minWidth
					dims := header(gtx)
					if w := dims.Size.X; w > maxWidth {
						maxWidth = w
					}
					return dims
				})
			}),
		}
		for i := 0; i < len(items); i++ {
			it := &items[i]
			children = append(children, layout.Rigid(func(gtx C) D {
				return material.Clickable(gtx, it.btn, func(gtx C) D {
					return layout.UniformInset(unit.Dp(16)).Layout(gtx, func(gtx C) D {
						gtx.Constraints.Min.X = minWidth
						dims := material.Body1(th, it.title).Layout(gtx)
						if w := dims.Size.X; w > maxWidth {
							maxWidth = w
						}
						return dims
					})
				})
			}))
		}
		f := layout.Flex{Axis: layout.Vertical}
		// First pass: record and discard operations
		// and determine widest item.
		m := op.Record(gtx.Ops)
		f.Layout(gtx, children...)
		m.Stop()
		// Second pass: layout items with equal width.
		minWidth = maxWidth
		return f.Layout(gtx, children...)
	})
}

func layoutDialog(gtx layout.Context, w layout.Widget) layout.Dimensions {
	return widget.Border{Color: argb(0x33000000), CornerRadius: unit.Dp(2), Width: unit.Dp(1)}.Layout(gtx, func(gtx C) D {
		return Background{Color: rgb(0xfafafa), CornerRadius: unit.Dp(2)}.Layout(gtx, w)
	})
}

// layoutMenu lays out the menu activated by the 3 dots button.
func (ui *UI) layoutMenu(gtx layout.Context, sysIns system.Insets, expiry time.Time, showExits bool, needsLogin bool) {
	ui.menu.dismiss.Add(gtx, color.NRGBA{})
	if ui.menu.dismiss.Dismissed(gtx) {
		ui.setMenuShown(false)
	}
	layout.Inset{
		Top:   sysIns.Top + unit.Dp(2),
		Right: sysIns.Right + unit.Dp(2),
	}.Layout(gtx, func(gtx C) D {
		return layout.NE.Layout(gtx, func(gtx C) D {
			menu := &ui.menu
			if ui.setLoginServer {
				return D{}
			}
			if needsLogin {
				var items []menuItem
				title := "Tailscale " + version.Short()
				if ui.menu.showDebugMenu {
					items = append(items, menuItem{title: "Change server", btn: &menu.useLoginServer})
				}
				items = append(items, menuItem{title: "About", btn: &menu.about})
				return layoutMenu(ui.theme, gtx, items, func(gtx C) D {
					l := material.Caption(ui.theme, title)
					return l.Layout(gtx)
				})
			}
			items := []menuItem{
				{title: "Copy my IP address", btn: &menu.copy},
			}
			if showExits {
				items = append(items, menuItem{title: "Use exit node...", btn: &menu.exits})
			}
			items = append(items,
				menuItem{title: "Bug report", btn: &menu.bug},
				menuItem{title: "Reauthenticate", btn: &menu.reauth},
				menuItem{title: "Log out", btn: &menu.logout},
			)

			var title string
			if ui.runningExit {
				title = "Stop running exit node"
			} else {
				title = "Run exit node"
			}
			items = append(items, menuItem{title: title, btn: &menu.beExit})

			items = append(items, menuItem{title: "About", btn: &menu.about})

			return layoutMenu(ui.theme, gtx, items, func(gtx C) D {
				var expiryStr string
				const fmtStr = time.Stamp
				switch {
				case expiry.IsZero():
					expiryStr = "Expires: (never)"
				case time.Now().After(expiry):
					expiryStr = fmt.Sprintf("Expired: %s", expiry.Format(fmtStr))
				default:
					expiryStr = fmt.Sprintf("Expires: %s", expiry.Format(fmtStr))
				}
				l := material.Caption(ui.theme, expiryStr)
				l.Color = rgb(0x8f8f8f)
				return l.Layout(gtx)
			})
		})
	})
}

func (ui *UI) layoutMessage(gtx layout.Context, sysIns system.Insets) layout.Dimensions {
	s := ui.message.text
	if s == "" {
		return D{}
	}
	now := gtx.Now
	d := now.Sub(ui.message.t0)
	rem := 4*time.Second - d
	if rem < 0 {
		return D{}
	}
	op.InvalidateOp{At: now.Add(rem)}.Add(gtx.Ops)
	return layout.S.Layout(gtx, func(gtx C) D {
		return layout.Inset{
			Left:   sysIns.Left + unit.Dp(8),
			Right:  sysIns.Right + unit.Dp(8),
			Bottom: sysIns.Bottom + unit.Dp(8),
		}.Layout(gtx, func(gtx C) D {
			return Background{Color: rgb(0x323232), CornerRadius: unit.Dp(5)}.Layout(gtx, func(gtx C) D {
				return layout.UniformInset(unit.Dp(12)).Layout(gtx, func(gtx C) D {
					l := material.Body2(ui.theme, s)
					l.Color = rgb(0xdddddd)
					return l.Layout(gtx)
				})
			})
		})
	})
}

func (ui *UI) showMessage(gtx layout.Context, msg string) {
	ui.message.text = msg
	ui.message.t0 = gtx.Now
	op.InvalidateOp{}.Add(gtx.Ops)
}

func MaxDp(p1, p2 unit.Dp) unit.Dp {
	if p1 > p2 {
		return p1
	}
	return p2
}

// layoutPeer lays out a peer name and IP address (e.g.
// "localhost\n100.100.100.101")
func (ui *UI) layoutPeer(gtx layout.Context, sysIns system.Insets, p *UIPeer, user tailcfg.UserID, clk *widget.Clickable) layout.Dimensions {
	return material.Clickable(gtx, clk, func(gtx C) D {
		return layout.Inset{
			Top:    unit.Dp(8),
			Right:  MaxDp(sysIns.Right, unit.Dp(16)),
			Left:   MaxDp(sysIns.Left, unit.Dp(16)),
			Bottom: unit.Dp(8),
		}.Layout(gtx, func(gtx C) D {
			gtx.Constraints.Min.X = gtx.Constraints.Max.X
			return layout.Flex{Axis: layout.Vertical}.Layout(gtx,
				layout.Rigid(func(gtx C) D {
					return layout.Inset{Bottom: unit.Dp(4)}.Layout(gtx, func(gtx C) D {
						name := p.Peer.DisplayName(p.Peer.User == user)
						return material.H6(ui.theme, name).Layout(gtx)
					})
				}),
				layout.Rigid(func(gtx C) D {
					var bestIP netip.Addr // IP to show; first IPv4, or first IPv6 if no IPv4
					for _, addr := range p.Peer.Addresses {
						if ip := addr.Addr(); !bestIP.IsValid() || bestIP.Is6() && ip.Is4() {
							bestIP = ip
						}
					}
					l := material.Body2(ui.theme, bestIP.String())
					l.Color = rgb(0x434343)
					return l.Layout(gtx)
				}),
			)
		})
	})
}

// layoutSection lays out a section title (e.g. "My devices").
func (ui *UI) layoutSection(gtx layout.Context, sysIns system.Insets, title string) layout.Dimensions {
	return Background{Color: rgb(0xe1e0e9)}.Layout(gtx, func(gtx C) D {
		return layout.Inset{
			Top:    unit.Dp(16),
			Right:  MaxDp(sysIns.Right, unit.Dp(16)),
			Left:   MaxDp(sysIns.Left, unit.Dp(16)),
			Bottom: unit.Dp(16),
		}.Layout(gtx, func(gtx C) D {
			l := material.Body1(ui.theme, title)
			l.Color = rgb(0x6f797d)
			return l.Layout(gtx)
		})
	})
}

// layoutTop lays out the top controls: toggle, status and menu dots.
func (ui *UI) layoutTop(gtx layout.Context, sysIns system.Insets, state *BackendState) layout.Dimensions {
	in := layout.Inset{
		Top:    unit.Dp(16),
		Bottom: unit.Dp(16),
	}
	return Background{Color: rgb(headerColor)}.Layout(gtx, func(gtx C) D {
		return layout.Inset{
			Top:   sysIns.Top,
			Right: MaxDp(sysIns.Right, unit.Dp(8)),
			Left:  MaxDp(sysIns.Left, unit.Dp(16)),
		}.Layout(gtx, func(gtx C) D {
			return layout.Flex{Alignment: layout.Middle}.Layout(gtx,
				layout.Rigid(func(gtx C) D {
					return in.Layout(gtx, func(gtx C) D {
						if state.State <= ipn.NeedsLogin {
							return D{}
						}
						sw := material.Switch(ui.theme, &ui.enabled, "Enable VPN")
						sw.Color.Enabled = rgb(white)
						if state.State < ipn.Stopped {
							sw.Color.Enabled = rgb(0xbbbbbb)
							sw.Color.Disabled = rgb(0xbbbbbb)
						}
						return sw.Layout(gtx)
					})
				}),
				layout.Flexed(1, func(gtx C) D {
					return in.Layout(gtx, func(gtx C) D {
						return layout.Inset{Left: unit.Dp(16)}.Layout(gtx, func(gtx C) D {
							lbl := material.Body1(ui.theme, statusString(state.State))
							lbl.Color = rgb(0xffffff)
							return lbl.Layout(gtx)
						})
					})
				}),
				layout.Rigid(func(gtx C) D {
					btn := material.IconButton(ui.theme, &ui.menu.open, ui.icons.more, "Open menu")
					btn.Color = rgb(white)
					btn.Background = color.NRGBA{}
					return btn.Layout(gtx)
				}),
			)
		})
	})
}

func statusString(state ipn.State) string {
	switch state {
	case ipn.Stopped:
		return "Stopped"
	case ipn.Starting:
		return "Starting..."
	case ipn.Running:
		return "Active"
	case ipn.NeedsMachineAuth:
		return "Awaiting Approval"
	case ipn.NeedsLogin:
		return "Tailscale"
	default:
		return "Loading..."
	}
}

func (ui *UI) showCopied(gtx layout.Context, addr string) {
	ui.showMessage(gtx, fmt.Sprintf("Copied %s", addr))
}

// layoutLocal lays out the information box about the local node's
// name and IP address.
func (ui *UI) layoutLocal(gtx layout.Context, sysIns system.Insets, host, addr string) layout.Dimensions {
	return Background{Color: rgb(headerColor)}.Layout(gtx, func(gtx C) D {
		return layout.Inset{
			Right:  MaxDp(sysIns.Right, unit.Dp(8)),
			Left:   MaxDp(sysIns.Left, unit.Dp(8)),
			Bottom: unit.Dp(8),
		}.Layout(gtx, func(gtx C) D {
			return Background{Color: rgb(infoColor), CornerRadius: unit.Dp(8)}.Layout(gtx, func(gtx C) D {
				return material.Clickable(gtx, &ui.self, func(gtx C) D {
					return layout.UniformInset(unit.Dp(16)).Layout(gtx, func(gtx C) D {
						gtx.Constraints.Min.X = gtx.Constraints.Max.X
						return layout.Flex{Axis: layout.Vertical}.Layout(gtx,
							layout.Rigid(func(gtx C) D {
								return layout.Inset{Bottom: unit.Dp(4)}.Layout(gtx, func(gtx C) D {
									name := material.H6(ui.theme, host)
									name.Color = rgb(0xffffff)
									return name.Layout(gtx)
								})
							}),
							layout.Rigid(func(gtx C) D {
								name := material.Body2(ui.theme, addr)
								name.Color = rgb(0xc5ccd9)
								return name.Layout(gtx)
							}),
						)
					})
				})
			})
		})
	})
}

func (ui *UI) layoutSearchbar(gtx layout.Context, sysIns system.Insets) layout.Dimensions {
	return Background{Color: rgb(0xf0eff6)}.Layout(gtx, func(gtx C) D {
		return layout.Inset{
			Top:    unit.Dp(8),
			Right:  MaxDp(sysIns.Right, unit.Dp(8)),
			Left:   MaxDp(sysIns.Left, unit.Dp(8)),
			Bottom: unit.Dp(8),
		}.Layout(gtx, func(gtx C) D {
			return Background{Color: rgb(0xe3e2ea), CornerRadius: unit.Dp(8)}.Layout(gtx, func(gtx C) D {
				return layout.UniformInset(unit.Dp(8)).Layout(gtx, func(gtx C) D {
					return layout.Flex{Alignment: layout.Middle}.Layout(gtx,
						layout.Rigid(func(gtx C) D {
							col := mulAlpha(ui.theme.Palette.Fg, 0xbb)
							return ui.icons.search.Layout(gtx, col)
						}),
						layout.Flexed(1,
							material.Editor(ui.theme, &ui.search, "Search by machine name...").Layout,
						),
					)
				})
			})
		})
	})
}

// drawLogo draws the Tailscale logo using vector operations.
func drawLogo(ops *op.Ops, size int) {
	scale := float64(size) / 680
	discDia := float32(170 * scale)
	off := int(math.Round(172 * 1.5 * scale))
	tx := op.Offset(image.Pt(off, 0))
	ty := op.Offset(image.Pt(0, off))

	defer op.Offset(image.Point{}).Push(ops).Pop()

	// First row of discs.
	row := op.Offset(image.Point{}).Push(ops)
	drawDisc(ops, discDia, rgb(0x54514d))
	tx.Add(ops)
	drawDisc(ops, discDia, rgb(0x54514d))
	tx.Add(ops)
	drawDisc(ops, discDia, rgb(0x54514d))
	row.Pop()

	ty.Add(ops)
	// Second row.
	row = op.Offset(image.Point{}).Push(ops)
	drawDisc(ops, discDia, rgb(0xfffdfa))
	tx.Add(ops)
	drawDisc(ops, discDia, rgb(0xfffdfa))
	tx.Add(ops)
	drawDisc(ops, discDia, rgb(0xfffdfa))
	row.Pop()

	ty.Add(ops)
	// Third row.
	row = op.Offset(image.Point{}).Push(ops)
	drawDisc(ops, discDia, rgb(0xfffdfa))
	drawDisc(ops, discDia, rgb(0x54514d))
	tx.Add(ops)
	drawDisc(ops, discDia, rgb(0xfffdfa))
	tx.Add(ops)
	drawDisc(ops, discDia, rgb(0x54514d))
	row.Pop()
}

func drawImage(gtx layout.Context, img paint.ImageOp, size unit.Dp) layout.Dimensions {
	img.Add(gtx.Ops)
	sz := img.Size()
	aspect := float32(sz.Y) / float32(sz.X)
	w := gtx.Dp(size)
	h := int(float32(w)*aspect + .5)
	scale := float32(w) / float32(sz.X)
	defer op.Affine(f32.Affine2D{}.Scale(f32.Point{}, f32.Point{X: scale, Y: scale})).Push(gtx.Ops).Pop()
	paint.PaintOp{}.Add(gtx.Ops)
	return layout.Dimensions{Size: image.Pt(w, h)}
}

func drawDisc(ops *op.Ops, radius float32, col color.NRGBA) {
	r := int(math.Round(float64(radius)))
	r2 := int(math.Round(float64(radius * .5)))
	defer clip.RRect{
		Rect: image.Rect(0, 0, r, r),
		NE:   r2, NW: r2, SE: r2, SW: r2,
	}.Push(ops).Pop()
	paint.ColorOp{Color: col}.Add(ops)
	paint.PaintOp{}.Add(ops)
}

// Background lays out a widget and draws a color background behind it.
type Background struct {
	Color        color.NRGBA
	CornerRadius unit.Dp
}

func (b Background) Layout(gtx layout.Context, w layout.Widget) layout.Dimensions {
	m := op.Record(gtx.Ops)
	dims := w(gtx)
	sz := dims.Size
	call := m.Stop()
	// Clip corners, if any.
	if r := gtx.Dp(b.CornerRadius); r > 0 {
		defer clip.RRect{
			Rect: image.Rect(0, 0, sz.X, sz.Y),
			NE:   r, NW: r, SE: r, SW: r,
		}.Push(gtx.Ops).Pop()
	}
	fill{b.Color}.Layout(gtx, sz)
	call.Add(gtx.Ops)
	return dims
}

type fill struct {
	col color.NRGBA
}

func (f fill) Layout(gtx layout.Context, sz image.Point) layout.Dimensions {
	defer clip.Rect(image.Rectangle{Max: sz}).Push(gtx.Ops).Pop()
	paint.ColorOp{Color: f.col}.Add(gtx.Ops)
	paint.PaintOp{}.Add(gtx.Ops)
	return layout.Dimensions{Size: sz}
}

func rgb(c uint32) color.NRGBA {
	return argb((0xff << 24) | c)
}

func argb(c uint32) color.NRGBA {
	return color.NRGBA{A: uint8(c >> 24), R: uint8(c >> 16), G: uint8(c >> 8), B: uint8(c)}
}

const termsText = `Tailscale is a mesh VPN for securely connecting your devices. All connections are device-to-device, so we never see your data.

We collect and use your email address and name, as well as your device name, OS version, and IP address in order to help you to connect your devices and manage your settings. We log when you are connected to your network.`