[Arcana] extending input methods in emacs sucks

[Noah Friedman]

There is a babel of different input method systems in emacs.  A lot of them
use "quail".  Some are more direct (e.g. `ucs').  Some of them I just can't
tell how they work.

Anyway.  All I wanted was to be able to type a euro symbol without having
to remember what its unicode character number was.  I usually use the
rfc1345 input method, but of course the euro isn't defined in that.  

And as long as I was adding currency symbols, I wanted a common mnemonic
prefix for all of them since I couldn't remember the others either.

This is my completely graceless solution.


;; This is a macro so it can be used with approximately the same syntax as
;; quail-define-rules.
(defmacro quail-annotate-input-method (method &rest bindings)
  "Add new bindings to quail-based input methods"
  (when (symbolp method)
    (setq method (symbol-name method)))
  `(progn
     (require 'quail)
     (unless (assoc ,method quail-package-alist)
       (load ,(format "quail/%s" method)))
     (let ((quail-orig (quail-name)))
       (unwind-protect
           (progn
             (quail-select-package ,method)
             (quail-define-rules ((append t)) , at bindings))
         (when quail-orig
           (quail-select-package quail-orig))))))

;; Put all the common currency symbols on a "&$" prefix.
;; Calling decode-char is a no-op in emacs 23, but emacs 22 doesn't use ucs
;; native coding.
(eval-after-load 'rfc1345
  '(let ((bindings (mapcar (lambda (p)
                             (list (car p) (decode-char 'ucs (cadr p))))
                           '(("&$c" #x00a2)   ; cent
                             ("&$p" #x00a3)   ; british pound
                             ("&$u" #x00a4)   ; generic currency sign
                             ("&$y" #x00a5)   ; yen
                             ("&$e" #x20ac)   ; euro
                             ))))
     ;; macro application for the lose
     (eval `(quail-annotate-input-method rfc1345 , at bindings))))