func main() {
gtk.Init(&os.Args)
window := gtk.NewWindow(gtk.WINDOW_TOPLEVEL)
window.SetTitle("GTK DrawingArea")
window.Connect("destroy", gtk.MainQuit)
vbox := gtk.NewVBox(true, 0)
vbox.SetBorderWidth(5)
drawingarea := gtk.NewDrawingArea()
var p1, p2 point
var gdkwin *gdk.Window
var pixmap *gdk.Pixmap
var gc *gdk.GC
p1.x = -1
p1.y = -1
colors := []string{
"black",
"gray",
"blue",
"purple",
"red",
"orange",
"yellow",
"green",
"darkgreen",
}
drawingarea.Connect("configure-event", func() {
if pixmap != nil {
pixmap.Unref()
}
allocation := drawingarea.GetAllocation()
pixmap = gdk.NewPixmap(drawingarea.GetWindow().GetDrawable(), allocation.Width, allocation.Height, 24)
gc = gdk.NewGC(pixmap.GetDrawable())
gc.SetRgbFgColor(gdk.NewColor("white"))
pixmap.GetDrawable().DrawRectangle(gc, true, 0, 0, -1, -1)
gc.SetRgbFgColor(gdk.NewColor(colors[0]))
gc.SetRgbBgColor(gdk.NewColor("white"))
})
drawingarea.Connect("motion-notify-event", func(ctx *glib.CallbackContext) {
arg := ctx.Args(0)
mev := *(**gdk.EventMotion)(unsafe.Pointer(&arg))
var mt gdk.ModifierType
if mev.IsHint != 0 {
gdkwin.GetPointer(&p2.x, &p2.y, &mt)
} else {
p2.x, p2.y = int(mev.X), int(mev.Y)
}
if p1.x != -1 && p2.x != -1 && (gdk.EventMask(mt)&gdk.BUTTON_PRESS_MASK) != 0 {
pixmap.GetDrawable().DrawLine(gc, p1.x, p1.y, p2.x, p2.y)
gdkwin.Invalidate(nil, false)
}
colors = append(colors[1:], colors[0])
gc.SetRgbFgColor(gdk.NewColor(colors[0]))
p1 = p2
})
drawingarea.Connect("expose-event", func() {
if pixmap == nil {
return
}
gdkwin.GetDrawable().DrawDrawable(gc, pixmap.GetDrawable(), 0, 0, 0, 0, -1, -1)
})
drawingarea.SetEvents(int(gdk.POINTER_MOTION_MASK | gdk.POINTER_MOTION_HINT_MASK | gdk.BUTTON_PRESS_MASK))
vbox.Add(drawingarea)
window.Add(vbox)
window.SetSizeRequest(400, 400)
window.ShowAll()
gdkwin = drawingarea.GetWindow()
gtk.Main()
}
