Root.setFocus
void setFocus(gtk.widget.Widget focus = null)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 [gtk.widget.Widget.grabFocus] instead of this function.
Parameters
focus | widget to be the new focus widget, or null to unset the focus widget |