gotk glib.TimeoutAdd() single execution

gotk_timeoutadd_single.go

// This code contains no error checking for brevity.
// Always check your errors, kids!
package main

import (
	"fmt"

	"github.com/gotk3/gotk3/glib"
	"github.com/gotk3/gotk3/gtk"
)

type Gui struct {
	window  *gtk.Window
	label   *gtk.Label
	counter int
}

func main() {
	gtk.Init(nil)
	gui := GuiNew()
	gui.window.ShowAll()
	gtk.Main()
}

// Creates a window with a label showing a counter.
func GuiNew() *Gui {
	win, _ := gtk.WindowNew(gtk.WINDOW_TOPLEVEL)
	win.Connect("destroy", func() { gtk.MainQuit() })
	label, _ := gtk.LabelNew("Test 0")
	win.Add(label)
	gui := Gui{win, label, 0}
	glib.TimeoutAdd(500, gui.callback)
	return &gui
}

// Periodically called to increase the counter on the label.
func (g *Gui) callback() bool {
	g.counter += 1
	g.label.SetText(fmt.Sprintf("Test %d", g.counter))
	// ### This next line shouldn't be necessary... ###
	glib.TimeoutAdd(500, g.callback)
	// ### ... because callback() returns 'true'.   ###
	return true
}