ivy-posframe不生效

(require 'ivy-posframe)
;; display at `ivy-posframe-style'
;; (setq ivy-posframe-display-functions-alist '((t . ivy-posframe-display)))
(setq ivy-posframe-display-functions-alist '((t . ivy-posframe-display-at-frame-center)))
;; (setq ivy-posframe-display-functions-alist '((t . ivy-posframe-display-at-window-center)))
;; (setq ivy-posframe-display-functions-alist '((t . ivy-posframe-display-at-frame-bottom-left)))
;; (setq ivy-posframe-display-functions-alist '((t . ivy-posframe-display-at-window-bottom-left)))
;; (setq ivy-posframe-display-functions-alist '((t . ivy-posframe-display-at-frame-top-center)))
(ivy-posframe-mode 1)

启动之后没效果。