// When a cross is declared in its object literal form, it may not have the appropriate window.
// this function creates a new X11 window for the cross with the correct geometry depending
// on its Icon* parameters.
func (c *Cross) CreateWindow(X *xgbutil.XUtil, icons_per_direction int, bg_color uint32) (*xwindow.Window, error) {

	// calculate the dimensions of the spars of our cross +
	// width/height reflect the vertical-orientation rectangle
	width := c.IconMargin*2 + c.IconSize
	// padding between the icons, margin on the edges
	height := c.IconSize*icons_per_direction + c.IconPadding*(icons_per_direction-1) + c.IconMargin*2

	// intitialize a basic window for the cross
	win, err := xwindow.Generate(X)
	if err != nil {
		return nil, err
	}

	win.Create(X.RootWin(), 0, 0, height, height,
		xproto.CwBackPixel|xproto.CwOverrideRedirect, bg_color, 1)

	// the rects we will be adding together to form the shape of the cross
	vert := xrect.New(0, 0, width, height)
	horiz := xrect.New(0, 0, height, width)
	struts := []xrect.Rect{vert, horiz}

	geom, err := win.Geometry()
	if err != nil {
		return nil, err
	}

	// center struts over window
	x, y := util.CenterChild(vert, geom)
	vert.XSet(x)
	vert.YSet(y)
	x, y = util.CenterChild(horiz, geom)
	horiz.XSet(x)
	horiz.YSet(y)

	// build the cross shape from our friendly rectangles
	err = ComposeShape(X, win.Id, struts)
	if err != nil {
		return nil, err
	}

	// add the window to our cross struct
	c.Window = win

	// create icons from our images
	clr := RGB(bg_color)
	if c.imagesToBecomeIcons != nil {
		icons := make(map[string]*Icon, len(c.imagesToBecomeIcons))
		for name, img := range c.imagesToBecomeIcons {
			icon := NewIcon(X, img, win.Id)
			icon.Background = clr
			icons[name] = icon
		}
		c.Icons = icons
	} else {
		return nil, errors.New("Cross: you must create crosses using the NewCross function (this cross has now iconsToBecomeImage)")
	}

	return win, nil
}

func newParent(X *xgbutil.XUtil, cid xproto.Window) (*Parent, error) {
	parent, err := xwindow.Generate(X)
	if err != nil {
		logger.Error.Printf("Could not create a parent window for client "+
			"with id '%d' because: %s", cid, err)
		logger.Error.Fatalf("In a state where no new windows can be created. " +
			"Unfortunately, we must exit.")
	}

	err = parent.CreateChecked(X.RootWin(), 0, 0, 1, 1,
		xproto.CwEventMask,
		xproto.EventMaskSubstructureRedirect|
			xproto.EventMaskButtonPress|xproto.EventMaskButtonRelease)
	if err != nil {
		return nil, err
	}

	err = xproto.ReparentWindowChecked(X.Conn(),
		cid, parent.Id, 0, 0).Check()
	if err != nil {
		return nil, err
	}

	return &Parent{parent}, nil
}

// compose a number of rectabgles into a window shape
func ComposeShape(X *xgbutil.XUtil, dst xproto.Window, rects []xrect.Rect) (err error) {

	combine_bounds := make([]shape.CombineCookie, len(rects))
	combine_clip := make([]shape.CombineCookie, len(rects))

	var operation shape.Op

	for i, rect := range rects {
		// make rectangular window of correct goemetry
		win, err := xwindow.Generate(X)
		if err != nil {
			log.Fatalf("ComposeShape: Error creating rectange %v window.", rect)
			return err
		}
		win.Create(X.RootWin(), rect.X(), rect.Y(), rect.Width(), rect.Height(), xproto.CwBackPixel, 0xffffff)

		// choose operation. on the first one, we want to set the shape.
		if i == 0 {
			operation = shape.SoSet
		} else {
			operation = shape.SoUnion
		}

		// combine window request
		x, y := int16(rect.X()), int16(rect.Y())

		combine_kind := shape.Kind(shape.SkBounding)
		combine_bounds[i] = shape.CombineChecked(X.Conn(), operation, combine_kind, combine_kind, dst, x, y, win.Id)
		combine_kind = shape.Kind(shape.SkClip)
		combine_clip[i] = shape.CombineChecked(X.Conn(), operation, combine_kind, combine_kind, dst, x, y, win.Id)
	}
	return nil
}

func newWindow(X *xgbutil.XUtil) {
	win, err := xwindow.Generate(X)
	if err != nil {
		log.Fatal(err)
	}
	win.Create(X.RootWin(), 0, 0, 200, 200,
		xproto.CwBackPixel|xproto.CwEventMask,
		0, xproto.EventMaskButtonRelease)
	win.WMGracefulClose(
		func(w *xwindow.Window) {
			xevent.Detach(w.X, w.Id)
			mousebind.Detach(w.X, w.Id)
			w.Destroy()
			xevent.Quit(X)
			Done <- true
		})

	win.Map()

	err = mousebind.ButtonReleaseFun(
		func(X *xgbutil.XUtil, ev xevent.ButtonReleaseEvent) {
			newWindow(X)
		}).Connect(X, win.Id, "1", false, false)

	if err != nil {
		log.Fatal(err)
	}
}

func newWindow(X *xgbutil.XUtil, width, height int) *xwindow.Window {
	var (
		err error
		win *xwindow.Window
	)
	win, err = xwindow.Generate(X)
	if err != nil {
		log.Fatal(err)
	}
	win.Create(X.RootWin(), 0, 0, width, height,
		xproto.CwBackPixel|xproto.CwEventMask,
		0, xproto.EventMaskButtonRelease)
	win.WMGracefulClose(
		func(w *xwindow.Window) {
			xevent.Detach(w.X, w.Id)
			mousebind.Detach(w.X, w.Id)
			w.Destroy()
			xevent.Quit(X)
		})

	win.Map()

	if err != nil {
		log.Fatal(err)
	}
	return win
}

func newWindow(controlCh *controlCh, X *xgbutil.XUtil, width, height int) *xwindow.Window {
	var (
		err error
		win *xwindow.Window
	)

	win, err = xwindow.Generate(X)
	if err != nil {
		panic(err)
	}

	win.Create(X.RootWin(), 0, 0, width, height,
		xproto.CwBackPixel|xproto.CwEventMask,
		0, xproto.EventMaskButtonRelease)

	// Xorg application exits when the window is closed.
	win.WMGracefulClose(
		func(w *xwindow.Window) {
			xevent.Detach(w.X, w.Id)
			mousebind.Detach(w.X, w.Id)
			w.Destroy()
			xevent.Quit(X)
			controlCh.exit <- true
		})

	// In order to get ConfigureNotify events, we must listen to the window
	// using the 'StructureNotify' mask.
	win.Listen(xproto.EventMaskButtonPress |
		xproto.EventMaskButtonRelease |
		xproto.EventMaskKeyPress |
		xproto.EventMaskKeyRelease |
		xproto.EventMaskStructureNotify)
	win.Map()
	return win
}

// New allocates and initializes a new DockApp.  NewDockApp does not initialize
// the window contents and does not map the window to the display screen.  The
// window is mapped to the screen when the Main method is called on the
// returned DockApp.
func New(x *xgbutil.XUtil, rect image.Rectangle) (*DockApp, error) {
	win, err := xwindow.Generate(x)
	if err != nil {
		log.Fatalf("generate window: %v", err)
	}
	win.Create(x.RootWin(), 0, 0, rect.Size().X, rect.Size().Y, 0)

	// Set WM hints so that Openbox puts the window into the dock.
	hints := &icccm.Hints{
		Flags:        icccm.HintState | icccm.HintIconWindow,
		InitialState: icccm.StateWithdrawn,
		IconWindow:   win.Id,
		WindowGroup:  win.Id,
	}
	err = icccm.WmHintsSet(x, win.Id, hints)
	if err != nil {
		win.Destroy()
		return nil, fmt.Errorf("wm hints: %v", err)
	}
	img := xgraphics.New(x, rect)
	err = img.XSurfaceSet(win.Id)
	if err != nil {
		img.Destroy()
		win.Destroy()
		return nil, fmt.Errorf("xsurface set: %v", err)
	}
	app := &DockApp{
		x:   x,
		img: img,
		win: win,
	}
	return app, nil
}

func (f *Borders) newPieceWindow(ident string,
	cursor xproto.Cursor) *xwindow.Window {

	win, err := xwindow.Generate(f.X)
	if err != nil {
		logger.Error.Printf("Could not create a frame window for client "+
			"with id '%d' because: %s", f.client.Id(), err)
		logger.Error.Fatalf("In a state where no new windows can be created. " +
			"Unfortunately, we must exit.")
	}

	err = win.CreateChecked(f.parent.Id, 0, 0, 1, 1,
		xproto.CwBackPixmap|xproto.CwEventMask|xproto.CwCursor,
		xproto.BackPixmapParentRelative,
		xproto.EventMaskButtonPress|xproto.EventMaskButtonRelease|
			xproto.EventMaskButtonMotion|xproto.EventMaskPointerMotion,
		uint32(cursor))
	if err != nil {
		logger.Warning.Println(err)
	}

	f.client.FramePieceMouseSetup("borders_"+ident, win.Id)

	return win
}

func (m *TrayManager) Manage() bool {
	m.destroyOwnerWindow()

	win, _ := xwindow.Generate(TrayXU)
	m.owner = win.Id

	xproto.CreateWindowChecked(TrayXU.Conn(), 0, m.owner, TrayXU.RootWin(), 0, 0, 1, 1, 0, xproto.WindowClassInputOnly, m.visual, 0, nil)
	TrayXU.Sync()
	win.Listen(xproto.EventMaskStructureNotify)
	return m.tryOwner()
}

// newWindow creates a new window with a random background color. It sets the
// WM_PROTOCOLS property to contain the WM_DELETE_WINDOW atom. It also sets
// up a ClientMessage event handler so that we know when to destroy the window.
// We also set up a mouse binding so that clicking inside a window will
// create another one.
func newWindow(X *xgbutil.XUtil) {
	counter++
	win, err := xwindow.Generate(X)
	if err != nil {
		log.Fatal(err)
	}

	// Get a random background color, create the window (ask to receive button
	// release events while we're at it) and map the window.
	bgColor := rand.Intn(0xffffff + 1)
	win.Create(X.RootWin(), 0, 0, 200, 200,
		xproto.CwBackPixel|xproto.CwEventMask,
		uint32(bgColor), xproto.EventMaskButtonRelease)

	// WMGracefulClose does all of the work for us. It sets the appropriate
	// values for WM_PROTOCOLS, and listens for ClientMessages that implement
	// the WM_DELETE_WINDOW protocol. When one is found, the provided callback
	// is executed.
	win.WMGracefulClose(
		func(w *xwindow.Window) {
			// Detach all event handlers.
			// This should always be done when a window can no longer
			// receive events.
			xevent.Detach(w.X, w.Id)
			mousebind.Detach(w.X, w.Id)
			w.Destroy()

			// Exit if there are no more windows left.
			counter--
			if counter == 0 {
				os.Exit(0)
			}
		})

	// It's important that the map comes after setting WMGracefulClose, since
	// the WM isn't obliged to watch updates to the WM_PROTOCOLS property.
	win.Map()

	// A mouse binding so that a left click will spawn a new window.
	// Note that we don't issue a grab here. Typically, window managers will
	// grab a button press on the client window (which usually activates the
	// window), so that we'd end up competing with the window manager if we
	// tried to grab it.
	// Instead, we set a ButtonRelease mask when creating the window and attach
	// a mouse binding *without* a grab.
	err = mousebind.ButtonReleaseFun(
		func(X *xgbutil.XUtil, ev xevent.ButtonReleaseEvent) {
			newWindow(X)
		}).Connect(X, win.Id, "1", false, false)
	if err != nil {
		log.Fatal(err)
	}
}

// This is a slightly modified version of xgraphics.XShowExtra that does
// not set any resize constraints on the window (so that it can go
// fullscreen).
func showImage(im *xgraphics.Image, name string, quit bool) *xwindow.Window {
	if len(name) == 0 {
		name = "xgbutil Image Window"
	}
	w, h := im.Rect.Dx(), im.Rect.Dy()

	win, err := xwindow.Generate(im.X)
	if err != nil {
		xgbutil.Logger.Printf("Could not generate new window id: %s", err)
		return nil
	}

	// Create a very simple window with dimensions equal to the image.
	win.Create(im.X.RootWin(), 0, 0, w, h, 0)

	// Make this window close gracefully.
	win.WMGracefulClose(func(w *xwindow.Window) {
		xevent.Detach(w.X, w.Id)
		keybind.Detach(w.X, w.Id)
		mousebind.Detach(w.X, w.Id)
		w.Destroy()

		if quit {
			xevent.Quit(w.X)
		}
	})

	// Set WM_STATE so it is interpreted as a top-level window.
	err = icccm.WmStateSet(im.X, win.Id, &icccm.WmState{
		State: icccm.StateNormal,
	})
	if err != nil { // not a fatal error
		xgbutil.Logger.Printf("Could not set WM_STATE: %s", err)
	}

	// Set _NET_WM_NAME so it looks nice.
	err = ewmh.WmNameSet(im.X, win.Id, name)
	if err != nil { // not a fatal error
		xgbutil.Logger.Printf("Could not set _NET_WM_NAME: %s", err)
	}

	// Paint our image before mapping.
	im.XSurfaceSet(win.Id)
	im.XDraw()
	im.XPaint(win.Id)

	// Now we can map, since we've set all our properties.
	// (The initial map is when the window manager starts managing.)
	win.Map()

	return win
}

// newWndow creates a new window and dies on failure.
// This includes mapping the window but not setting up the event handlers.
// (The event handlers require the channels, and we don't create the channels
// until all images have been decoded. But we want to show the window to the
// user before that task is complete.)
func newWindow(X *xgbutil.XUtil) *window {
	xwin, err := xwindow.Generate(X)
	if err != nil {
		errLg.Fatalf("Could not create window: %s", err)
	}

	w := &window{
		Window: xwin,
	}
	w.create()

	return w
}

func NewWindow(width, height int) (w *Window, err error) {

	w = new(Window)
	w.width, w.height = width, height

	w.xu, err = xgbutil.NewConn()
	if err != nil {
		return
	}

	w.conn = w.xu.Conn()
	screen := w.xu.Screen()

	w.win, err = xwindow.Generate(w.xu)
	if err != nil {
		return
	}

	err = w.win.CreateChecked(screen.Root, 600, 500, width, height, 0)
	if err != nil {
		return
	}

	w.win.Listen(AllEventsMask)

	err = icccm.WmProtocolsSet(w.xu, w.win.Id, []string{"WM_DELETE_WINDOW"})
	if err != nil {
		fmt.Println(err)
		err = nil
	}

	w.bufferLck = &sync.Mutex{}
	w.buffer = xgraphics.New(w.xu, image.Rect(0, 0, width, height))
	w.buffer.XSurfaceSet(w.win.Id)

	keyMap, modMap := keybind.MapsGet(w.xu)
	keybind.KeyMapSet(w.xu, keyMap)
	keybind.ModMapSet(w.xu, modMap)

	w.events = make(chan interface{})

	w.SetIcon(Gordon)
	w.SetIconName("Go")

	go w.handleEvents()

	return
}

func main() {
	// Connect to the X server using the DISPLAY environment variable.
	X, err := xgbutil.NewConn()
	if err != nil {
		log.Fatal(err)
	}

	// Anytime the keybind (mousebind) package is used, keybind.Initialize
	// *should* be called once. It isn't strictly necessary, but allows your
	// keybindings to persist even if the keyboard mapping is changed during
	// run-time. (Assuming you're using the xevent package's event loop.)
	// It also handles the case when your modifier map is changed.
	keybind.Initialize(X)

	// Create a new window. We will listen for key presses and translate them
	// only when this window is in focus. (Similar to how `xev` works.)
	win, err := xwindow.Generate(X)
	if err != nil {
		log.Fatalf("Could not generate a new window X id: %s", err)
	}
	win.Create(X.RootWin(), 0, 0, 500, 500, xproto.CwBackPixel, 0xffffffff)

	// Listen for Key{Press,Release} events.
	win.Listen(xproto.EventMaskKeyPress, xproto.EventMaskKeyRelease)

	// Map the window.
	win.Map()

	// Notice that we use xevent.KeyPressFun instead of keybind.KeyPressFun,
	// because we aren't trying to make a grab *and* because we want to listen
	// to *all* key press events, rather than just a particular key sequence
	// that has been pressed.
	xevent.KeyPressFun(
		func(X *xgbutil.XUtil, e xevent.KeyPressEvent) {
			// keybind.LookupString does the magic of implementing parts of
			// the X Keyboard Encoding to determine an english representation
			// of the modifiers/keycode tuple.
			// N.B. It's working for me, but probably isn't 100% correct in
			// all environments yet.
			log.Println("Key:", keybind.LookupString(X, e.State, e.Detail))
		}).Connect(X, win.Id)

	// Finally, start the main event loop. This will route any appropriate
	// KeyPressEvents to your callback function.
	log.Println("Program initialized. Start pressing keys!")
	xevent.Main(X)
}

func newParent(X *xgbutil.XUtil, cid xproto.Window) (*Parent, error) {
	parent, err := xwindow.Generate(X)
	if err != nil {
		logger.Error.Printf("Could not create a parent window for client "+
			"with id '%d' because: %s", cid, err)
		logger.Error.Fatalf("In a state where no new windows can be created. " +
			"Unfortunately, we must exit.")
	}

	// clientAttrs, err := xproto.GetWindowAttributes(X.Conn(), cid).Reply()
	// if err != nil {
	// return nil, fmt.Errorf("Could not get window attributes: %s", err)
	// }

	// visual := clientAttrs.Visual
	// vdepth := getVisualDepth(X, visual)
	visual := X.Screen().RootVisual
	vdepth := X.Screen().RootDepth
	// logger.Debug.Printf("Visualid: %x, Depth: %d", visual, vdepth)
	err = xproto.CreateWindowChecked(X.Conn(),
		vdepth, parent.Id, X.RootWin(),
		0, 0, 1, 1, 0, xproto.WindowClassInputOutput, visual,
		xproto.CwEventMask,
		[]uint32{
			xproto.EventMaskSubstructureRedirect |
				xproto.EventMaskButtonPress |
				xproto.EventMaskButtonRelease |
				xproto.EventMaskFocusChange,
		}).Check()
	if err != nil {
		return nil, fmt.Errorf("Could not create window: %s", err)
	}

	err = xproto.ReparentWindowChecked(X.Conn(),
		cid, parent.Id, 0, 0).Check()
	if err != nil {
		return nil, fmt.Errorf("Could not reparent window: %s", err)
	}

	return &Parent{
		Window:      parent,
		MoveState:   &MoveState{},
		ResizeState: &ResizeState{},
		isMapped:    false,
	}, nil
}

func newWindow(X *xgbutil.XUtil, width, height int) *xwindow.Window {
	var (
		err error
		win *xwindow.Window
	)
	win, err = xwindow.Generate(X)
	if err != nil {
		log.Fatal(err)
	}
	win.Create(X.RootWin(), 0, 0, width, height,
		xproto.CwBackPixel|xproto.CwEventMask,
		0, xproto.EventMaskButtonRelease)
	win.WMGracefulClose(
		func(w *xwindow.Window) {
			xevent.Detach(w.X, w.Id)
			mousebind.Detach(w.X, w.Id)
			// w.Destroy()
			xevent.Quit(X)
			application.Exit()
		})

	// In order to get ConfigureNotify events, we must listen to the window
	// using the 'StructureNotify' mask.
	win.Listen(xproto.EventMaskStructureNotify)

	win.Map()

	xevent.ConfigureNotifyFun(
		func(X *xgbutil.XUtil, ev xevent.ConfigureNotifyEvent) {
			reshape(int(ev.Width), int(ev.Height))
		}).Connect(X, win.Id)

	// err = mousebind.ButtonReleaseFun(
	// 	func(X *xgbutil.XUtil, ev xevent.ButtonReleaseEvent) {
	// 		newWindow(X)
	// 	}).Connect(X, win.Id, "1", false, false)

	if err != nil {
		log.Fatal(err)
	}
	return win
}

func main() {
	var err error
	X, err = xgbutil.NewConn()
	if err != nil {
		log.Fatal(err)
	}

	clientids, err := ewmh.ClientListGet(X)
	if err != nil {
		log.Fatal(err)
	}

	for _, clientid := range clientids {
		name, err := ewmh.WmNameGet(X, clientid)
		if err != nil {
			continue
		}

		if name == "Super Hexagon" {
			HexWindow = xwindow.New(X, clientid)
			break
		}
	}

	if HexWindow == nil {
		log.Fatal("Couldn't find Super Hexagon window.")
	}

	//Create a window
	DisplayWindow, err = xwindow.Generate(X)
	if err != nil {
		log.Fatalf("Could not generate a new window X id: %s", err)
	}
	dgeom, _ := HexWindow.DecorGeometry()
	DisplayWindow.Create(X.RootWin(), 0, 0, dgeom.Width(), dgeom.Height(), xproto.CwBackPixel, 0)
	DisplayWindow.Map()

	//Start the routine that updates the window
	go updater()

	xevent.Main(X)
}

// newWindow creates the window, initializes the keybind and mousebind packages
// and sets up the window to act like a real top-level client.
func newWindow(X *xgbutil.XUtil) *Window {
	w, err := xwindow.Generate(X)
	if err != nil {
		errLg.Fatalf("Could not create window: %s", err)
	}

	keybind.Initialize(w.X)
	mousebind.Initialize(w.X)

	err = w.CreateChecked(w.X.RootWin(), 0, 0, 600, 600, xproto.CwBackPixel, 0xffffff)
	if err != nil {
		errLg.Fatalf("Could not create window: %s", err)
	}

	// Make the window close gracefully using the WM_DELETE_WINDOW protocol.
	w.WMGracefulClose(func(w *xwindow.Window) {
		xevent.Detach(w.X, w.Id)
		keybind.Detach(w.X, w.Id)
		mousebind.Detach(w.X, w.Id)
		w.Destroy()
		xevent.Quit(w.X)
	})

	// Set WM_STATE so it is interpreted as top-level and is mapped.
	err = icccm.WmStateSet(w.X, w.Id, &icccm.WmState{State: icccm.StateNormal})
	if err != nil {
		lg("Could not set WM_STATE: %s", err)
	}

	// _NET_WM_STATE = _NET_WM_STATE_NORMAL
	// not needed because we we set FS later anyway?
	//ewmh.WmStateSet(w.X, w.Id, []string{"_NET_WM_STATE_NORMAL"})

	w.Map()

	err = ewmh.WmStateReq(w.X, w.Id, ewmh.StateToggle, "_NET_WM_STATE_FULLSCREEN")
	if err != nil {
		lg("Failed to go FullScreen:", err)
	}
	return &Window{w}
}

func main() {
	X, err := xgbutil.NewConn()
	if err != nil {
		log.Fatal(err)
	}

	// Create the cursor. You can find a list of available cursors in
	// xcursor/cursordef.go.
	// We'll make an umbrella here, with an orange foreground and a blue
	// background. (The background it typically the outline of the cursor.)
	// Note that each component of the RGB color is a 16 bit color. I think
	// using the most significant byte to specify each component is good
	// enough.
	cursor, err := xcursor.CreateCursorExtra(X, xcursor.Umbrella,
		0xff00, 0x5500, 0x0000,
		0x3300, 0x6600, 0xff00)
	if err != nil {
		log.Fatal(err)
	}

	// Create a new window. In the create window request, we'll set the
	// background color and set the cursor we created above.
	// This results in changing the cursor only when it moves into this window.
	win, err := xwindow.Generate(X)
	if err != nil {
		log.Fatal(err)
	}
	win.Create(X.RootWin(), 0, 0, 500, 500,
		xproto.CwBackPixel|xproto.CwCursor,
		0xffffffff, uint32(cursor))
	win.Map()

	// We can free the cursor now that we've set it.
	// If you plan on using this cursor again, then it shouldn't be freed.
	// (i.e., if you try to free this before setting it as the cursor in a
	// window, you'll get a BadCursor error when trying to use it.)
	xproto.FreeCursor(X.Conn(), cursor)

	// Block. No need to process any events.
	select {}
}

// newGradientWindow creates a new X window, paints the initial gradient
// image, and listens for ConfigureNotify events. (A new gradient image must
// be painted in response to each ConfigureNotify event, since a
// ConfigureNotify event corresponds to a change in the window's geometry.)
func newGradientWindow(X *xgbutil.XUtil, width, height int,
	start, end color.RGBA) {

	// Generate a new window id.
	win, err := xwindow.Generate(X)
	if err != nil {
		log.Fatal(err)
	}

	// Create the window and die if it fails.
	err = win.CreateChecked(X.RootWin(), 0, 0, width, height, 0)
	if err != nil {
		log.Fatal(err)
	}

	// In order to get ConfigureNotify events, we must listen to the window
	// using the 'StructureNotify' mask.
	win.Listen(xproto.EventMaskStructureNotify)

	// Paint the initial gradient to the window and then map the window.
	paintGradient(X, win.Id, width, height, start, end)
	win.Map()

	xevent.ConfigureNotifyFun(
		func(X *xgbutil.XUtil, ev xevent.ConfigureNotifyEvent) {
			// If the width and height have not changed, skip this one.
			if int(ev.Width) == width && int(ev.Height) == height {
				return
			}

			// Compress ConfigureNotify events so that we don't lag when
			// drawing gradients in response.
			ev = compressConfigureNotify(X, ev)

			// Update the width and height and paint the gradient image.
			width, height = int(ev.Width), int(ev.Height)
			paintGradient(X, win.Id, width, height, start, end)
		}).Connect(X, win.Id)
}