ttk.go
func focusWindow(w *Window) {
	if w == nil {
		return
	}
	_, found := windows[w.id]
	if !found {
		return
	}
	if focus == w {
		return
	}
	prevFocus = focus
	focus = w

	resizeAndRender(w)
}
func focusWindow(w *Window) {
	if w == nil {
		return
	}
	_, found := windows[w.id]
	if !found {
		return
	}
	if focus == w {
		return
	}
	prevFocus = focus
	focus = w

	resizeAndRender(w)
}
// focus on provided window. This will implicitly focus on a window widget
// that can have focus.  Render and flush it onto the terminal.
// focus shall be called from queue context.