Causes @widget to have the keyboard focus for the GtkWindow it's inside.
If @widget is not focusable, or its ::grab_focus implementation cannot
transfer the focus to a descendant of @widget that is focusable, it will
not take focus and %FALSE will be returned.
Calling [method@Gtk.Widget.grab_focus] on an already focused widget
is allowed, should not have an effect, and return %TRUE.
Causes @widget to have the keyboard focus for the GtkWindow it's inside.
If @widget is not focusable, or its ::grab_focus implementation cannot transfer the focus to a descendant of @widget that is focusable, it will not take focus and %FALSE will be returned.
Calling [method@Gtk.Widget.grab_focus] on an already focused widget is allowed, should not have an effect, and return %TRUE.