FindFunc

find-function

;;; Commentary:
;;
;; The funniest thing about this is that I can't imagine why a package
;; so obviously useful as this hasn't been written before!!
;; ;;; find-func
;; (find-function-setup-keys)
;;
;; or just:
;;
;; (load "find-func")
;;
;; if you don't like the given keybindings and away you go!  It does
;; pretty much what you would expect, putting the cursor at the
;; definition of the function or variable at point.
;;
;; The code started out from `describe-function', `describe-key'
;; ("help.el") and `fff-find-loaded-emacs-lisp-function' (Noah Friedman's
;; "fff.el").

Suggestion

widen before jump

find-function/find-variable with widen does not work. – rubikitch

(defun find-function-do-it (symbol type switch-fn)
  "Find Emacs Lisp SYMBOL in a buffer and display it.
TYPE is nil to search for a function definition,
or else `defvar' or `defface'.

The variable `find-function-recenter-line' controls how
to recenter the display.  SWITCH-FN is the function to call
to display and select the buffer.
See also `find-function-after-hook'.

Set mark before moving, if the buffer already existed."
  (let* ((orig-point (point))
	(orig-buf (window-buffer))
	(orig-buffers (buffer-list))
	(buffer-point (save-excursion
			(find-definition-noselect symbol type)))
	(new-buf (car buffer-point))
	(new-point (cdr buffer-point)))
    (when buffer-point
      (when (memq new-buf orig-buffers)
	(push-mark orig-point))
      (funcall switch-fn new-buf)
      (widen)                           ;added!
      (when new-point (goto-char new-point))
      (recenter find-function-recenter-line)
      (run-hooks 'find-function-after-hook))))