FWIW. O manual do emacs desencoraja o uso de window-system
como um predicado.
Do not use window-system and initial-window-system as predicates or boolean flag variables, if you want to write code that works differently on text terminals and graphic displays. That is because window-system is not a good indicator of Emacs capabilities on a given display type. Instead, use display-graphic-p or any of the other display-*-p predicates described in Display Feature Testing.
Eu uso isso para desativar a barra de rolagem e a barra de ferramentas quando estiver em uma exibição gráfica.
(if (display-graphic-p)
(progn
(tool-bar-mode -1)
(scroll-bar-mode -1)))