GoNCurses refresh background window after foreground window moves

I am trying to understand how does ncurses work. Here is one example I am struggling to understand and make it work.

First the idea:

• Window 1 (stdscr) with background and printed text
• Window 2 (sWin) over Window 1 with different background
• Moving Window 2 over Window 1

And here is the setup:

stdscr, _ := gc.Init()
defer gc.End()
gc.Echo(false)
gc.Cursor(0)
gc.CBreak(true)
stdscr.SetBackground('#')
stdscr.MovePrint(12, 15, "ABCDEFGHIJKLMNOPQ...")
stdscr.NoutRefresh()
y, x := 10, 20
sWin, _ := gc.NewWindow(4, 8, y, x)
sWin.Keypad(true)
sWin.SetBackground('.')
sWin.Box(0, 0)
sWin.NoutRefresh()
gc.Update()

And a very simple for loop that will help with moving the foreground window:

main:
for {
	// stdscr.Erase()
	// stdscr.NoutRefresh()
	sWin.MoveWindow(y, x)
	sWin.NoutRefresh()
	gc.Update()
	switch sWin.GetChar() {
	case gc.KEY_RIGHT:
		x++
	case gc.KEY_DOWN:
		y++
	case 'q':
		break main
	}
}
sWin.Delete()
stdscr.Delete()

Now when I move window 2 the one in the background does not refresh and a trail is left:

##########################
#######┌┌┌┌┌──────┐#######
#######│││││......│#######
##ABCDE│││││......│...####
#######└└└└└──────┘#######
##########################
##########################

When I uncomment stdscr.Erase() and stdscr.NoutRefresh() I fix the trail but of course I lose all the data on the background window such as the text "ABCDEFGHIJKLMNOPQ...":

#####################
#######┌──────┐######
#######│......│######
#######│......│######
#######└──────┘######
#####################
#####################

I tried making Window 2 a sub window of the main one but it did not work. How can I fix/handle this? And how are overlapping windows managed in general with ncurses?
Thanks!

curses doesn't support that directly (see the panel library. Otherwise, you'll have to use touchwin as a workaround (done with dialog and cdk).