focus is not the current focus widget, and is focusable, sets
it as the focus widget for the window. If
the focus widget for this window. To set the focus to a particular
widget in the toplevel, it is usually more convenient to use
gtkWidgetGrabFocus instead of this function.
gtkWindowSetFocus(object, focus = NULL)
- widget to be the new focus widget, or
NULLto unset any focus widget for the toplevel window. [ allow-none ]