Lacking Natural Simplicity

Random musings on books, code, and tabletop games.

Fun With Emacs: Unicode and #'describe-char

T. Kurt Bond

2008-08-15 12:07

Ever use the emacs command describe-char? It's even more fun with proper unicode lookup data!

;; First, we'll bind it to a key.
(global-set-key "\C-cD" #'describe-char)

;; Now we'll download it if necessary.
(let ((udf-url "http://www.unicode.org/Public/UNIDATA/UnicodeData.txt")
      (udf-dest "~/tmp/UnicodeData.txt"))
  (if (file-readable-p udf-dest)
      ;; Let describe-char know it exists.
      (setq describe-char-unicodedata-file udf-dest)
    ;; It doesn't exist, and we need to download it!
    (when (y-or-n-p (format "You need to download %s ! Do it? " udf-url))
      ;; Really weird: wget -O 'file' complains that file doesn't exist.
      (let* ((cmd (format "cd ~/tmp/ && wget -O %s --progress=dot '%s'"
                          udf-dest udf-url))
             (buf (get-buffer-create (format " *wget '%s'*" udf-url)))
             (proc (start-process-shell-command "wget-unicode-Data"
                                                buf cmd)))
        (display-buffer buf)
        (set-process-sentinel
         proc
         `(lambda (proc event)
            (unless (string-match "^finished" event)
              (error "unexpected status '%s' getting '%s'" ,udf-url event))
            (setq describe-char-unicodedata-file ,udf-dest)
            (message "Try describe-char now! ☣☥☸▧◉✘✽☮⅙▧⚅☑☢☹☺♠♥♦♣♨♻⚔")))
        (message "Downloading... check describe-char later")
        nil))))

Once this is run and it tells you to try describe-char you can position your cursor over one of the Unicode characters in the message (“C-h e” to display the “Messages” buffer) and press “C-cD” and look for the “Name:” line. You'll see something like this:

      character: ♻ (299515, #o1110773, #x491fb, U+267B)
        charset: mule-unicode-2500-33ff (Unicode characters of the range U+2500..U+33FF.)
     code point: #x23 #x7B
         syntax: w    which means: word
    buffer code: #x9C #xF2 #xA3 #xFB
      file code: #xE2 #x99 #xBB (encoded by coding system mule-utf-8)
        display: terminal code #xE2 #x99 #xBB
   Unicode data:
           Name: BLACK UNIVERSAL RECYCLING SYMBOL
       Category: other symbol
Combining class: Spacing
  Bidi category: Other Neutrals

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