Frontend Development

Interface Protocol

Frontends subclass implementation and implement lem-if:* generics.

Required Methods

;; Core
(lem-if:invoke impl function)           ; Start event loop
(lem-if:display-width impl)             ; Screen width (chars)
(lem-if:display-height impl)            ; Screen height (chars)
(lem-if:update-display impl)            ; Flush to screen

;; Views
(lem-if:make-view impl window x y w h use-modeline)
(lem-if:delete-view impl view)
(lem-if:set-view-size impl view w h)
(lem-if:set-view-pos impl view x y)

;; Rendering
(lem-if:render-line impl view x y objects height)
(lem-if:clear-to-end-of-window impl view y)

Implementation Capabilities

Set in class definition:

(defclass my-impl (implementation)
  ()
  (:default-initargs
   :name :my-frontend
   :support-floating-window t
   :window-left-margin 1))

Event Handling

Send events to core via send-event:

(send-event (lambda () (execute-key-sequence keys)))

Reference

• frontends/sdl2/ - Full-featured GUI
• frontends/ncurses/ - Terminal
• frontends/fake-interface/ - Testing stub