Re: List of major modes? // "switch-to-mode"??

[Kevin Rodgers <ihs_4664@yahoo.com>]

David Reitter wrote:
 > Thanks for your help with this.
 >
 > Here is my fusion of your code, not using the documentation strings,
 > but using apropos-internal to speed things up:
 >
 > (apropos-internal
 > "-mode\\'"
 > (lambda (mode)
 >    (and (commandp mode)
 >     (not (string-match "\\`turn-\\(on\\|off\\)-"
 >                (symbol-name mode)))
 >     (not (assq mode minor-mode-alist)))))
 >
 > Here's why I wanted this:
 >
 > I'd like to come up with a function switch-to-buffer that could be  used
 > interactively instead of M-x, with the advantage that completion  would
 > only complete mode names, and it would be able to display a  list of
 > modes (together with the first lines of their documentation  strings) .

In what way is "used interactively" different from `M-x'?

What does switch-to-buffer have to do with major modes?

You can modify the interactive behavior of any command like this:

(defadvice some-command (before weird-interaction activate)
   "Read arguments with `weird-interaction'."
   (interactive (weird-interaction)))

 > Has anyone already written something like this? (or is there an Emacs
 > function that I don't know of...?)

If you want to display the documentation in the *Completions* buffer, it
will be returned along with the mode name.  But you could then select
just the mode name from that:

(let* ((major-modes
         (apropos-internal "-mode\\'"
                           (lambda (mode)
                             (and (commandp mode)
                                  (string-match "\\`Major mode\\>"
                                                (documentation mode))))))
        (completions
         (mapcar (lambda (mode)
                   (let* ((doc-string (documentation mode))
                          (text (format "%s (%s)"
                                        mode
                                        (substring doc-string 0
                                                   (string-match "\n"
 
doc-string)))))
                     (list text)))
                 major-modes))
        (completed-string (completing-read "Major mode (w/docstring): "
                                           completions)))
   (substring completed-string 0 (string-match " " completed-string)))

It would be better if you could associate the docstring as a tool tip
over the mode name in the *Completions* buffer, but text properties seem
to get removed when the completions are inserted into the buffer:

(let* ((major-modes
         (apropos-internal "-mode\\'"
                           (lambda (mode)
                             (and (commandp mode)
                                  (string-match "\\`Major mode\\>"
                                                (documentation mode))))))
        (completions
         (mapcar (lambda (mode)
                   (let* ((doc-string (documentation mode))
                          (tooltip (substring doc-string 0
                                              (string-match "\n" 
doc-string)))
                          (mode-name (copy-sequence (symbol-name mode))))
                     (put-text-property 0 (1- (length mode-name)) 'help-echo
                                        mode-name)
                     (list mode-name)))
                 major-modes)))
   (completing-read "Major mode (w/docstring): " completions))

-- 
Kevin Rodgers