Cautionary Tales Incomptable ECL SDL2 C lisp.

Opens a blank window, which reads keypresses and modifier keys until closed (escape or a normal way of quitting quits)

$ doas pkg_add sdl2 ecl
$ ecl
> (ext:install-c-compiler)
> (setf c:*user-ld-flags* "-lSDL2")
> (compile-file "keys.ecl.lisp" :load t)
> (sdl2-receive-keys) ; pops up a window. Use Esc or your wm to quit
((:|Left Alt| (:LCTRL :LALT :NUM) 1073742050 4416)
 (:A (:LCTRL :LALT :NUM) 97 4416)
 (:|Right Shift| (:RSHIFT :NUM) 1073742053 4098)
 (:|Return| (:RSHIFT :NUM) 13 4098))

(ffi:clines "
#include <stdio.h>

#include <SDL2/SDL.h>

SDL_Renderer *renderer;
SDL_Window *window;
SDL_Event e;
")

(defun c-keyname (sdlk) "
sdlk should be an e.key.keysym.sym originating int.
"
  (let ((cstring (ffi:c-inline (sdlk) (:int) :cstring "SDL_GetKeyName(#0)" :one-liner t)))
    (ffi:convert-from-cstring cstring)))

(defun interpret-mods (keymod) "
keymod should be an e.key.keysym.mod originating int.
"
  (let ((mods '((:lshift .    #x1)
                (:rshift .    #x2)
                (:lctrl  .   #x40)
                (:rctrl  .   #x80)
                (:lalt   .  #x100)
                (:ralt   .  #x200)
                (:lgui   .  #x400)
                (:rgui   .  #x800)
                (:num    . #x1000)
                (:caps   . #x2000)
                (:mode   . #x4000)
                (:scroll . #x8000))))
    (loop :for mod :in mods
          :for kw := (car mod)
          :for hx := (cdr mod)
          :unless (zerop (logand hx keymod))
            :collect kw)))

(defun sdl2-receive-keys (&aux (keys ()))
  (let ((key 0) ; int (ie default enum)
        (mod 0)) ; uint16
    (declare (:int key mod))
    (ffi:c-progn (key mod)
   "
if (SDL_Init(SDL_INIT_VIDEO) < 0)
"
   (error "%s failed" 'SDL_INIT_VIDEO)
   "
if (SDL_CreateWindowAndRenderer(
        640, 480, SDL_WINDOW_RESIZABLE,
        &window, &renderer))
"
   (error "%s failed" 'SDL_WINDOW_RESIZABLE)
   "

for (;;) { 
SDL_SetRenderDrawColor(renderer,0,0,0,255);
SDL_RenderClear(renderer);
SDL_RenderPresent(renderer);
SDL_Delay(25);

while (SDL_PollEvent(&e))
        if (e.type == SDL_QUIT) {
quit:
            SDL_DestroyRenderer(renderer);
            SDL_DestroyWindow(window);
            SDL_Quit();"
            (return-from sdl2-receive-keys (nreverse keys)) "
        } else if (e.type == SDL_KEYDOWN)
            if (e.key.keysym.sym == SDLK_ESCAPE) goto quit;
        else {
            #0 = (int)e.key.keysym.sym;
            #1 = (int)(e.key.keysym.mod & 65475);"
            (push (list (intern (c-keyname key) :keyword)
                        (interpret-mods mod)
                        key
                        mod)
                  keys)
        "}}")))

4. But what does it mean

Author: Screwlisp

Created: 2024-06-06 Thu 19:07

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