google-translate.el を使ったときに、翻訳する言語を自動で切り替える。

google-translate-auto.el

(require 'google-translate)
(global-set-key "\C-ct" 'google-translate-at-point-auto)

(defun set-google-translate-language (source target)
     (custom-set-variables
      '(google-translate-default-source-language source)
      '(google-translate-default-target-language target)
      )
     )

(defun google-translate-at-point-auto (beg end)
  (interactive "r")
  (if (string-match "[^\x01-\x7E]" (buffer-substring-no-properties beg end))
      (set-google-translate-language "ja" "en")  ; region contains 2 byte character
      (set-google-translate-language "en" "ja")
      )
  (google-translate-at-point)
  )