() Joe Riel <joer@san.rr.com>
() Sun, 11 May 2014 14:40:13 -0700

   Is there an existing elisp function that displays just the defs
   [first line] and doc-strings in an elisp source buffer?

I don't think so.  However, you can use hideshow like so:

 (defun display-docstring-and-code-line-counts (ov)
   (when (eq 'code (overlay-get ov 'hs))
     (let ((beg (overlay-start ov))
           (end (overlay-end ov)))
       (save-excursion
         (goto-char (overlay-start ov))
         (forward-line 1)
         (when (looking-at "\\s-*\"")
           (forward-sexp 1)
           (cond ((eolp)
                  ;; purposeful
                  (forward-line 1)
                  (skip-chars-forward "[:space:]")
                  (move-overlay ov (setq beg (point)) end))
                 (t 
                  ;; unbearable lightness
                  (delete-overlay ov)
                  (setq ov nil)))))
       (when ov
         (overlay-put
          ov 'display (propertize 
                       (format " ... / %d"
                               (count-lines beg end))
                       'face 'font-lock-warning-face))))))
 
 (setq hs-set-up-overlay
       'display-docstring-and-code-line-counts)
 
The line-count stuff is because this code is dervived from the
example given in `C-h v hs-set-up-overlay'.  The important part is
the call to ‘move-overlay’.  Readers of source code (src/buffer.c)
will note that ‘delete-overlay’ returns nil, but that is not
documented.  Had it been, i would have reversed the sense of the
innermost COND and used IF:

           (if (not (eolp))
               ;; unbearable lightness
               (setq ov (delete-overlay ov))
             ;; purposeful
             (forward-line 1)
             (skip-chars-forward "[:space:]")
             (move-overlay ov (setq beg (point)) end))

But that's just a question of style.  Mogrify at will, YMMV, etc...
 
-- 
Thien-Thi Nguyen
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