func main() {
	var cx, cy, cw, ch, midy int
	message := "Now is the time for all good men to come to the aid of the party"

	w, h := openvg.Init()
	var speed openvg.VGfloat = 15.0
	var x openvg.VGfloat = 0
	midy = (h / 2)
	fontsize := w / 50
	cx = 0
	ch = fontsize * 2
	cw = w
	cy = midy - (ch / 2)

	rx, ry, rw, rh := openvg.VGfloat(cx), openvg.VGfloat(cy), openvg.VGfloat(cw), openvg.VGfloat(ch)
	// scroll the text, only in the clipping rectangle
	for x = 0; x < rw+speed; x += speed {
		openvg.Start(w, h)
		openvg.Background(255, 255, 255)
		openvg.FillRGB(0, 0, 0, .2)
		openvg.Rect(rx, ry, rw, rh)
		openvg.ClipRect(cx, cy, cw, ch)
		openvg.Translate(x, ry+openvg.VGfloat(fontsize/2))
		openvg.FillRGB(0, 0, 0, 1)
		openvg.Text(0, 0, message, "sans", fontsize)
		openvg.ClipEnd()
		openvg.End()
	}
	bufio.NewReader(os.Stdin).ReadBytes('\n')
	openvg.Finish()
	os.Exit(0)
}

func init() {
	width, height = openvg.Init()
	flag.Float64Var(&size, "s", float64(width)*.05, "bubble size")
	flag.IntVar(&niter, "n", width/6, "number of iterations")
	flag.Float64Var(&opacity, "o", 0.5, "opacity")
	flag.Parse()
	rand.Seed(int64(time.Now().Nanosecond()) % 1e9)
}

// show the current time, weather and headlines
func main() {
	var (
		section    = flag.String("h", "u.s.", "headline type (arts, health, sports, science, technology, u.s., world, hn)")
		location   = flag.String("loc", "40.6213,-74.4395", "lat,long for weather")
		bgcolor    = flag.String("bg", "slateblue", "background color")
		textcolor  = flag.String("tc", "white", "text color")
		width      = flag.Int("width", 0, "screen width")
		height     = flag.Int("height", 0, "screen height")
		smartcolor = flag.Bool("sc", false, "smart colors")
		thumb      = flag.Bool("tn", false, "show thumbnails")
	)
	flag.Parse()

	// initial display
	dw, dh := openvg.Init()
	if *width > 0 && *height > 0 {
		dw, dh = *width, *height
	}
	openvg.Start(dw, dh)
	canvas := display{
		width:     openvg.VGfloat(dw),
		height:    openvg.VGfloat(dh),
		bgcolor:   *bgcolor,
		textcolor: *textcolor,
	}
	canvas.countdown()
	openvg.End()
	canvas.clock(*smartcolor)
	canvas.weather(*location)
	canvas.headlines(*section, *thumb)

	// update on specific intervals, shutdown on interrupt
	dateticker := time.NewTicker(1 * time.Minute)
	weatherticker := time.NewTicker(5 * time.Minute)
	headticker := time.NewTicker(10 * time.Minute)
	sigint := make(chan os.Signal, 1)
	signal.Notify(sigint, os.Interrupt)

	for {
		select {
		case <-dateticker.C:
			canvas.clock(*smartcolor)
		case <-weatherticker.C:
			canvas.weather(*location)
		case <-headticker.C:
			canvas.headlines(*section, *thumb)
		case <-sigint:
			openvg.Finish()
			os.Exit(0)
		}
	}
}

// main initializes the system and shows the picture.
// Exit and clean up when you hit [RETURN].
func main() {
	rseed()
	openvg.SaveTerm()
	nargs := len(os.Args)
	w, h := openvg.Init()
	openvg.RawTerm()
	progname := os.Args[0]
	n := 5
	if nargs > 2 {
		n, _ = strconv.Atoi(os.Args[2])
	}
	if nargs > 1 {
		switch os.Args[1] {
		case "help":
			usage(progname)
			os.Exit(1)
		case "advert":
			advert(w, h)
		case "image":
			imagetable(w, h)
		case "text":
			tb(w, h)
		case "textplay":
			textplay(w, h)
		case "astro":
			planets(w, h, "You are here")
		case "fontsize":
			fontrange(w, h)
		case "raspi":
			raspi(w, h, "The Raspberry Pi")
		case "loop":
			loop(w, h)
		case "demo":
			demo(w, h, n)
		case "rand":
			rshapes(w, h, n)
		case "test":
			testpattern(w, h, "hello, world")
		case "rotate":
			rotext(w, h, n, "Raspi")
		case "gradient":
			gradient(w, h)
		default:
			refcard(w, h)
		}
	} else {
		refcard(w, h)
	}
	WaitEnd()
}

// main plots data from specified files or standard input in a
// grid where plotc specifies the number of columns.
func main() {
	w, h := openvg.Init()
	openvg.Start(w, h)
	openvg.FillColor("white")
	openvg.Rect(0, 0, gwidth, gheight)
	filenames := flag.Args()
	if len(filenames) == 0 {
		doplot(beginx, beginy, "")
	} else {
		plotgrid(beginx, beginy, filenames)
	}
	openvg.SaveEnd("vgplot.raw")
	bufio.NewReader(os.Stdin).ReadByte()
	openvg.Finish()
}

func InitDisplay(iw, ih int) {
	sWidth, sHeight = openvg.Init()
	iWidth, iHeight = iw, ih
	out = make([]C.VGubyte, iw*ih*VG_CHANS)

	// clear screen to opaque black
	openvg.StartColor(sWidth, sHeight, "black", 1.0)
	openvg.End()

	// apply scale transform so images fill the screen
	ScaleImage(float64(sWidth)/float64(iWidth),
		float64(sHeight)/float64(iHeight))

	fmt.Printf("Image display initialised to (%d, %d)\n", iw, ih)
}

// raspberry pi, scaled to the screen dimensions
func main() {
	w, h := openvg.Init()
	midx := openvg.VGfloat(w) / 2
	midy := openvg.VGfloat(h) / 2
	rw := midx
	rh := (rw * 2) / 3
	fontsize := w / 25
	openvg.Start(w, h)
	openvg.Background(255, 255, 255)
	makepi(midx-(rw/2), midy-(rh/2), rw, rh)
	makepi(200, 100, 75, 50)
	openvg.FillRGB(128, 0, 0, 1)
	openvg.TextMid(midx, midy-(rh/2)-openvg.VGfloat(fontsize*2), "The Raspberry Pi", "sans", fontsize)
	WaitEnd()
}

func main() {

	width, height := openvg.Init()

	w := openvg.VGfloat(width)
	h := openvg.VGfloat(height)
	y := h / 2
	var (
		margin  openvg.VGfloat = 100.0
		minsize openvg.VGfloat = 7.0
		labeloc openvg.VGfloat = 100.0
	)
	bgcolor := "black"
	labelcolor := "white"
	maxsize := (h / 2) * 0.05

	origin := sun.distance
	mostDistant := neptune.distance
	firstSize := mercury.radius
	lastSize := neptune.radius

	openvg.Start(width, height)
	openvg.BackgroundColor(bgcolor)

	for _, p := range solarSystem {
		x := vmap(p.distance, origin, mostDistant, margin, w-margin)
		r := vmap(p.radius, firstSize, lastSize, minsize, maxsize)

		if p.name == "Sun" {
			openvg.FillRGB(p.color.Red, p.color.Green, p.color.Blue, 1)
			openvg.Circle(margin-(r/2), y, r)
		} else {
			light(x, y, r, p.color)
			openvg.Circle(x, y, r)
		}
		if p.name == "Earth" && len(os.Args) > 1 {
			openvg.StrokeColor(labelcolor)
			openvg.StrokeWidth(1)
			openvg.Line(x, y+(r/2), x, y+labeloc)
			openvg.StrokeWidth(0)
			openvg.FillColor(labelcolor)
			openvg.TextMid(x, y+labeloc+10, os.Args[1], "sans", 12)
		}
	}
	openvg.End()
	bufio.NewReader(os.Stdin).ReadByte()
	openvg.Finish()
}

func main() {
	setOptions()
	rand.Seed(time.Now().Unix())
	w, h := openvg.Init()
	width, height := openvg.VGfloat(w), openvg.VGfloat(h)
	initParticles(width, height)
	openvg.Start(w, h)
	i := 0
	for {
		draw(width, height)
		i++
		if alternate && i == nswitch { // switch launch direction every nswitch draws
			directionRTL = !directionRTL
			i = 0
		}
	}
}

func main() {
	width, height := openvg.Init() // OpenGL, etc initialization

	w2 := float64(width / 2)
	h2 := float64(height / 2)
	w := float64(width)

	openvg.Start(width, height)                               // Start the picture
	openvg.BackgroundColor("black")                           // Black background
	openvg.FillRGB(44, 77, 232, 1)                            // Big blue marble
	openvg.Circle(w2, 0, w)                                   // The "world"
	openvg.FillColor("white")                                 // White text
	openvg.TextMid(w2, h2, "hello, world", "serif", width/10) // Greetings
	openvg.SaveEnd("hello.raw")                               // End the picture
	bufio.NewReader(os.Stdin).ReadBytes('\n')                 // Pause until [RETURN]
	openvg.Finish()                                           // Graphics cleanup
}

func main() {
	var loop = flag.Bool("loop", false, "Loop the show")
	var resize = flag.Bool("resize", false, `Resize image to fit the screen.`)
	var bgcolor = flag.String("bg", "black", `Background color (named color or rgb(r,g,b)).`)
	var delay = flag.Duration("delay", 2*time.Second, "Delay between pictures")
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "usage: %s [ flags ] images...\n", os.Args[0])
		flag.PrintDefaults()
		os.Exit(1)
	}

	flag.Parse()
	w, h := openvg.Init()
	images := []image.Image{}
	imgcount := 0
	for _, imgfile := range flag.Args() {
		fmt.Fprintf(os.Stderr, "loading %q ", imgfile)
		img, err := getimage(imgfile, w, h, *resize)
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			continue
		}
		images = append(images, img)
		imgcount++
		fmt.Fprintln(os.Stderr, "ok")
	}
	for {
		for _, img := range images {
			ib := img.Bounds()
			imw, imh := ib.Max.X-ib.Min.X, ib.Max.Y-ib.Min.Y
			openvg.Start(w, h)
			openvg.BackgroundColor(*bgcolor)
			x, y := openvg.VGfloat(w)/2-openvg.VGfloat(imw)/2, openvg.VGfloat(h)/2-openvg.VGfloat(imh)/2
			openvg.Img(x, y, img)
			openvg.End()
			time.Sleep(*delay)
		}
		if !*loop {
			break
		}
	}
}

func main() {
	width, height := openvg.Init() // OpenGL, etc initialization

	w := openvg.VGfloat(width)
	h := openvg.VGfloat(height)

	openvg.Start(width, height)     // Start the picture
	openvg.BackgroundColor("white") // Black background
	openvg.FillColor("black")
	var x, y, spacing openvg.VGfloat

	x = w * 0.10
	y = h * 0.90
	fontsize := 24
	spacing = openvg.VGfloat(fontsize) * 2
	var data = []string{
		"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",
		"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f",
		"\x20\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f",
		"\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f",
		"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f",
		"\x50\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c\x5d\x5e\x5f",
		"\x60\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f",
		"\x70\x71\x72\x73\x74\x75\x76\x77\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f",
		"\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f",
		"\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f",
		"\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf",
		"\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf",
		"\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf",
		"\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf",
		"\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef",
		"\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff",
	}
	for i, s := range data {
		openvg.Text(x-(spacing*2), y, fmt.Sprintf("%2x", i), "mono", fontsize)
		openvg.Text(x, y, s, "mono", fontsize)
		y -= spacing
	}
	openvg.End()                              // End the picture
	bufio.NewReader(os.Stdin).ReadBytes('\n') // Pause until [RETURN]
	openvg.Finish()                           // Graphics cleanup
}

func main() {
	width, height := openvg.Init() // OpenGL, etc initialization

	w2 := float64(width / 2)
	h2 := float64(height / 2)
	w := float64(width)

	stops := []openvg.Offcolor{
		{0.0, openvg.RGB{44, 100, 232}, 1.0}, // blue-ish
		{0.5, openvg.RGB{22, 50, 151}, 1.0},  // darker blue
		{1.0, openvg.RGB{88, 200, 255}, 1.0}, // lighter blue
	}

	openvg.Start(width, height)                               // Start the picture
	openvg.BackgroundColor("black")                           // Black background
	openvg.FillRadialGradient(w2, 0, w2, w2, w*.5, stops)     // Big blue marble
	openvg.Circle(w2, 0, w)                                   // The "world"
	openvg.FillColor("white")                                 // White text
	openvg.TextMid(w2, h2, "hello, world", "serif", width/10) // Greetings
	openvg.SaveEnd("hvg.raw")                                 // End the picture
	bufio.NewReader(os.Stdin).ReadBytes('\n')                 // Pause until [RETURN]
	openvg.Finish()                                           // Graphics cleanup
}

func main() {
	var nr = flag.Int("n", 500, "number of objects")
	var message = flag.String("m", "Go/OpenVG", "message")
	var bgcolor = flag.String("bg", "white", "background color")
	var fgcolor = flag.String("fg", "maroon", "text color")

	flag.Parse()
	rseed()

	width, height := openvg.Init()
	fw := openvg.VGfloat(width)
	fh := openvg.VGfloat(height)

	openvg.Start(width, height)
	openvg.BackgroundColor(*bgcolor)
	for i := 0; i < *nr; i++ {

		red := uint8(rand.Intn(255))
		green := uint8(rand.Intn(255))
		blue := uint8(rand.Intn(255))
		alpha := randf()

		x := randf() * fw
		y := randf() * fh
		radius := randf() * fw / 10

		openvg.FillRGB(red, green, blue, alpha)
		openvg.Circle(x, y, radius)
	}
	openvg.FillColor(*fgcolor)
	openvg.TextMid(fw/2, fh/2, *message, "sans", width/25)
	openvg.End()

	bufio.NewReader(os.Stdin).ReadBytes('\n')
	openvg.Finish()
}

func main() {
	var (
		filename     = flag.String("f", "svgcolors.txt", "input file")
		fontname     = flag.String("font", "sans", "fontname")
		neg          = flag.Bool("neg", false, "negative")
		showrgb      = flag.Bool("rgb", false, "show RGB")
		showcode     = flag.Bool("showcode", true, "show colors and codes")
		circsw       = flag.Bool("circle", true, "circle swatch")
		outline      = flag.Bool("outline", false, "outline swatch")
		fontsize     = flag.Int("fs", 12, "fontsize")
		rowsize      = flag.Int("r", 32, "rowsize")
		colw         = flag.Float64("c", 340, "column size")
		swatch       = flag.Float64("s", 16, "swatch size")
		gutter       = flag.Float64("g", 12, "gutter")
		err          error
		tcolor, line string
	)

	flag.Parse()
	f, oerr := os.Open(*filename)
	if oerr != nil {
		fmt.Fprintf(os.Stderr, "%v\n", oerr)
		return
	}
	width, height := openvg.Init()

	openvg.Start(width, height)
	fw := openvg.VGfloat(width)
	fh := openvg.VGfloat(height)
	if *neg {
		openvg.FillColor("black")
		openvg.Rect(0, 0, fw, fh)
		tcolor = "white"
	} else {
		openvg.FillColor("white")
		openvg.Rect(0, 0, fw, fh)
		tcolor = "black"
	}
	top := fh - 32.0
	left := openvg.VGfloat(32.0)
	cw := openvg.VGfloat(*colw)
	sw := openvg.VGfloat(*swatch)
	g := openvg.VGfloat(*gutter)
	in := bufio.NewReader(f)

	for x, y, nr := left, top, 0; err == nil; nr++ {
		line, err = in.ReadString('\n')
		fields := strings.Split(strings.TrimSpace(line), "\t")
		if nr%*rowsize == 0 && nr > 0 {
			x += cw
			y = top
		}
		if len(fields) == 3 {
			var red, green, blue uint8
			fmt.Sscanf(fields[2], "%d,%d,%d", &red, &green, &blue)
			openvg.FillRGB(red, green, blue, 1)
			if *outline {
				openvg.StrokeColor("black")
				openvg.StrokeWidth(1)
			}
			if *circsw {
				openvg.Circle(x+sw/2, y+sw/2, sw)
			} else {
				openvg.Rect(x, y, sw, sw)
			}
			openvg.StrokeWidth(0)
			openvg.FillColor(tcolor)
			openvg.Text(x+sw+openvg.VGfloat(*fontsize/2), y, fields[0], *fontname, *fontsize)
			var label string
			if *showcode {
				if *showrgb {
					label = fields[1]
				} else {
					label = fields[2]
				}
				openvg.FillColor("gray")
				openvg.TextEnd(x+cw-(sw+g), y, label, *fontname, *fontsize)
			}
		}
		y -= (sw + g)
	}
	openvg.End()
	bufio.NewReader(os.Stdin).ReadBytes('\n')
	openvg.Finish()
}

func main() {
	flag.Usage = func() {
		fmt.Fprintf(os.Stdout,
			`usage: %s [ opts ] image-path

Set specified image as an overlay screen via OpenVG lib.
Default is to put this image to the center.

`, os.Args[0])
		flag.PrintDefaults()
	}

	var resize bool
	var bg_color string
	flag.BoolVar(&resize, "resize", false, `Resize image to fit the screen (using "convert" binary.`)
	flag.StringVar(&bg_color, "bg-color", "",
		`Background color to use with centered image, in RRGGBB (hex, e.g. "aabbcc") format.`)

	flag.Parse()
	if flag.NArg() != 1 {
		log.Print("ERROR: Exactly one image-path argument must be specified.")
		flag.Usage()
	}
	var r, g, b uint8
	var err error
	if len(bg_color) == 0 {
		r, g, b = 0, 0, 0
	} else if len(bg_color) == 6 {
		n, err := strconv.ParseUint(bg_color[:2], 16, 8)
		if err == nil {
			r = uint8(n)
			n, err = strconv.ParseUint(bg_color[2:4], 16, 8)
		}
		if err == nil {
			g = uint8(n)
			n, err = strconv.ParseUint(bg_color[4:6], 16, 8)
		}
		if err == nil {
			b = uint8(n)
		}
	}
	if err != nil {
		log.Fatalf("ERROR: Failed to parse bg-color value (%v): %v", bg_color, err)
	}
	image_path := flag.Args()[0]

	exit_code := 0
	defer func() {
		os.Exit(exit_code)
	}()

	openvg.SaveTerm()
	w, h := openvg.Init()
	openvg.RawTerm()
	defer openvg.Finish()
	defer openvg.RestoreTerm()

	image_conf, err := get_image_conf(image_path)
	if err == nil && resize && (image_conf.Width != w || image_conf.Height != h) {
		image_path, err = resize_image(w, h, image_path)
	}
	if err != nil {
		log.Printf("ERROR: Failed to process image (%v): %v", image_path, err)
		exit_code = 1
	} else {
		sig_chan := make(chan os.Signal, 1)
		signal.Notify(sig_chan, os.Interrupt, os.Kill,
			syscall.SIGHUP, syscall.SIGTERM, syscall.SIGALRM)

		openvg.Start(w, h)
		openvg.Background(r, g, b)
		if resize {
			openvg.Image(0, 0, w, h, image_path)
		} else {
			x, y := openvg.VGfloat(w)/2-openvg.VGfloat(image_conf.Width)/2,
				openvg.VGfloat(h)/2-openvg.VGfloat(image_conf.Height)/2
			openvg.Image(x, y, image_conf.Width, image_conf.Height, image_path)
		}
		openvg.End()

		_ = <-sig_chan
	}
}

func main() {
	var resize = flag.Bool("resize", false, "Resize image to fit the screen.")
	var bgcolor = flag.String("bg", "black", "Background color (named color or rgb(r,g,b)).")
	var fgcolor = flag.String("fg", "white", "text color (named color or rgb(r,g,b)).")
	var title = flag.String("t", "", "text annotation")
	var fontsize = flag.Float64("fp", 2.0, "fontsize %")
	var px = flag.Float64("px", 50, "x position %")
	var py = flag.Float64("py", 50, "y position %")
	var texty = flag.Float64("ty", 0, "text y %")
	var exit_code int
	defer func() {
		os.Exit(exit_code)
	}()
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, `usage: %s [ flags ] image-path

Set specified image as an overlay screen via OpenVG lib.
Default is to put this image to the center.

`, os.Args[0])
		flag.PrintDefaults()
		exit_code = 1
		return
	}

	flag.Parse()
	if flag.NArg() != 1 {
		fmt.Fprintf(os.Stderr, "Exactly one image-path argument must be specified.\n")
		flag.Usage()
		exit_code = 2
		return
	}

	openvg.SaveTerm()
	w, h := openvg.Init()
	openvg.RawTerm()
	defer openvg.Finish()
	defer openvg.RestoreTerm()

	img, err := getimage(flag.Args()[0], w, h, *resize)
	if err != nil {
		exit_code = 3
		return
	}
	ib := img.Bounds()
	imw, imh := ib.Max.X-ib.Min.X, ib.Max.Y-ib.Min.Y
	sig_chan := make(chan os.Signal, 1)
	signal.Notify(sig_chan, os.Interrupt, os.Kill, syscall.SIGHUP, syscall.SIGTERM, syscall.SIGALRM)

	openvg.Start(w, h)
	openvg.BackgroundColor(*bgcolor)
	var x, y openvg.VGfloat
	if *px < 0 || *px > 100 {
		x = openvg.VGfloat(w)/2 - openvg.VGfloat(imw)/2
	} else {
		x = openvg.VGfloat(w)*openvg.VGfloat(*px/100) - openvg.VGfloat(imw)/2
	}

	if *py < 0 || *py > 100 {
		y = openvg.VGfloat(h)/2 - openvg.VGfloat(imh)/2
	} else {
		y = openvg.VGfloat(h)*openvg.VGfloat(*py/100) - openvg.VGfloat(imh)/2
	}
	openvg.Img(x, y, img)
	if len(*title) > 0 {
		var typ openvg.VGfloat
		fs := openvg.VGfloat(*fontsize/100.0) * openvg.VGfloat(w)
		if *texty == 0 {
			typ = y - fs*1.5
		} else {
			typ = openvg.VGfloat(h) * openvg.VGfloat(*texty/100)
		}
		openvg.FillColor(*fgcolor)
		openvg.TextMid(x+openvg.VGfloat(imw)/2, typ, *title, "sans", int(fs))
	}
	openvg.End()

	_ = <-sig_chan
}

func main() {
	flag.StringVar(&mincolor, "mincolor", "maroon", "minute color")
	flag.StringVar(&facecolor, "facecolor", "white", "face color")
	flag.StringVar(&hrcolor, "hourcolor", "gray", "hour color")
	flag.StringVar(&secolor, "secolor", "maroon", "second color")
	flag.StringVar(&digitcolor, "digitcolor", "black", "digit color")
	flag.StringVar(&dotcolor, "dotcolor", "silver", "dotcolor")
	flag.StringVar(&framecolor, "framecolor", "gray", "frame color")
	flag.StringVar(&centercolor, "centercolor", "black", "center color")
	flag.StringVar(&handstyle, "handstyle", "combo", "handstyle (combo, arrow, or round)")
	flag.BoolVar(&showdigits, "showdigits", true, "show digits")
	flag.BoolVar(&showdots, "showdots", true, "show dots")
	flag.BoolVar(&secline, "secline", false, "show second hand")
	flag.Parse()

	width, height := openvg.Init()
	cx := openvg.VGfloat(width / 2)
	cy := openvg.VGfloat(height / 2)
	facesize := openvg.VGfloat(cy * 0.5)
	textsize := facesize / 10.0
	framesize := facesize * 2.5
	hourstroke := textsize
	minstroke := hourstroke * .6

	// set up the ticker and signal handler
	ticker := time.NewTicker(1 * time.Second)
	sigint := make(chan os.Signal, 1)
	signal.Notify(sigint, os.Interrupt)

	// main loop: for each second, draw the clock components
	openvg.Start(width, height)
	for {
		select {
		case <-ticker.C:
			// get the current time
			hr, min, sec := time.Now().Clock()

			// compute element coordinates
			hx, hy, mx, my, sx, sy := timecoord(cx, cy, facesize, hr, min, sec)

			// frame and clock face
			frame(cx, cy, framesize, facesize, textsize, framecolor, facecolor)
			face(cx, cy, facesize, int(textsize*1.5))

			// hour and minute hands
			switch handstyle {
			case "round", "r":
				roundhand(cx, cy, mx, my, minstroke, mincolor)
				roundhand(cx, cy, hx, hy, hourstroke, hrcolor)
			case "arrow", "a":
				arrowhand(cx, cy, mx, my, facesize*0.9, minangles[min], 0, mincolor)
				arrowhand(cx, cy, hx, hy, facesize*0.6, hourangles[hr%12], min, hrcolor)
			case "combo", "c":
				combohand(cx, cy, mx, my, facesize*0.9, minstroke/2, minangles[min], 0, mincolor)
				combohand(cx, cy, hx, hy, facesize*0.6, minstroke/2, hourangles[hr%12], min, hrcolor)
			default:
				combohand(cx, cy, mx, my, facesize*0.9, minstroke/2, minangles[min], 0, mincolor)
				combohand(cx, cy, hx, hy, facesize*0.6, minstroke/2, hourangles[hr%12], min, hrcolor)
			}

			// second indicator
			secondhand(cx, cy, sx, sy, textsize)

			// center dot
			centerdot(cx, cy, textsize)

			// make the picture
			openvg.End()
		case <-sigint:
			openvg.Finish()
			return
		}
	}
}