public void set_has_window (bool has_window)
Specifies whether this has a Window of its own.
Note that all realized widgets have a non-null “window” pointer (
get_window never returns a null window when
a widget is realized), but for many of them it’s actually the Window of one of its parent
widgets. Widgets that do not create a window for themselves in
realize must announce this by calling this function with
This function should only be called by widget implementations, and they should call it in their
whether or not this has a window.