from gi.repository import Gtk

win = Gtk.Window()

win.connect("destroy", lambda w: Gtk.main_quit())

def show_new_win(w) :
	win = Gtk.Window()
	gla = Gtk.GLArea()
	win.add(gla)
	win.show_all()

box = Gtk.Box()
box.set_orientation(Gtk.Orientation.HORIZONTAL)
bu = Gtk.Button("test")
bu.connect("clicked", show_new_win)
box.pack_start(bu, False, False, 0)

gla = Gtk.GLArea()
box.pack_start(gla, True, True, 0)



win.add(box)

win.show_all()

Gtk.main()
