If @focus is not the current focus widget, and is focusable, sets it as the focus widget for the root.
If @focus is %NULL, unsets the focus widget for the root.
To set the focus to a particular widget in the root, it is usually more convenient to use [method@Gtk.Widget.grab_focus] instead of this function.
widget to be the new focus widget, or %NULL to unset the focus widget
See Implementation
If @focus is not the current focus widget, and is focusable, sets it as the focus widget for the root.
If @focus is %NULL, unsets the focus widget for the root.
To set the focus to a particular widget in the root, it is usually more convenient to use [method@Gtk.Widget.grab_focus] instead of this function.