public unowned Display get_display ()
Get the `GdkDisplay` for the toplevel window associated with this widget.
This function can only be called after the widget has been added to a widget hierarchy with a `GtkWindow` at the top.
In general, you should only create display specific resources when a widget has been realized, and you should free those resources when the widget is unrealized.
the `GdkDisplay` for the toplevel for this widget.