purpose of c2ffi was to see how common lisp can access sdl + cairo , to this end this part of the project has been a success.

difficulty is display code is locked up in an event loop

if wish to draw something , it has to be in the event loop

find functional approach to coding gives easier to understand answers

much less headache if the system is mainly functional because those class of bugs do not creep in

whereas mutation ...

but a hash map , surely mutation is a good thing ?

....

what like now is to see how to code a user interface using sdl and cairo .

for example , visualise a running common lisp program , debug it , see solution played out in real time , ability to step forwards and backwards , check values , evaluate expressions

problems come up are if mutation is allowed , then how can we step backwards in time ?

mutation raises other difficulties like sharing between threads , can we use a value if our value is over-written ?

....

here is version use common lisp + c2ffi to generate relevant procedure bindings

actually can write most of it without an automated scripting c2ffi to extract clang llvm headers and struct information from c files / header files

nice experiment to see what it takes to get something off the ground

really want a back end that suffers details of graphics , front end simply says

2 dimensional graphics protocol

clear-buffer draw-rectangle filled orange draw-lines present-buffer

...

wrote a little package in lem that mirrors tetris example in source tree

use arrow keys to move a square on screen

M-x start-lisp-repl (load "welcome.lisp") C-x 2 split screen vertically C-x o other screen M-x welcome

each buffer is clipped it appears

debian ubuntu packages are woe-fully out of date .

quicklisp common lisp "swank" server is over a year or two old.

(ql:quickload :swank) 
; hose perfectly good swank-2.29.1 version with 2.28 version
; which then complains when try to 

; unless we change ~/.sbclrc file to read 

(setf asdf:*central-registry*
       (list* '*default-pathname-defaults*
              #p"/home/terry/src/slime-2.29.1/"
              #p"/usr/share/common-lisp/systems/"
              asdf:*central-registry*))

;;(asdf:oos 'asdf:load-op :swank)

built using LLVM 17 from llvm.sh needed a stable version of debian

achieved using a chroot environment and downloading entire distribution just to build c2ffi