At work, I very commonly have to look up bits of information about strings in my code. For instance, we might use an incomprehensible ID, "a587fg", to refer to a customer with a perfectly comprehensible name, "FooCorp". It's fairly easy to define a function and bind it to a key mapping to look up a thing under point -- but what I'd much prefer is an ElDoc-style "here's some info about thing-under-point in the echo area, automatically" situation.

My reflex was to go to ElDoc itself, but I can't get it to work and I've no idea why. My best theory so far is that ElDoc only triggers on symbols -- which, of course, an arbitrary string isn't, and probably shouldn't be.

So: maybe I'm wiring up ElDoc wrong? Maybe there's a better way to do info-of-string-at-point? Who can help me understand how to get this working?

For reference, here's how I'm wiring things up:

(defun my-eldoc-function ()
  "Get info about string at point"
  (let (the-str)
    (if (setq the-str (thing-at-point 'string t))
        (my-str-doc-fun the-str) ;; Returns a string or nil

(set (make-local-variable 'eldoc-documentation-function)
  • Perhaps a minor mode that does the echoing as the cursor moves around -- is that what you were thinking?
    – Emacs User
    Dec 3, 2015 at 18:57
  • Yep -- that's precisely what I have in mind. I've already defined the minor mode, and have this lookup done as a function triggered by a key command; now I want to be able to lookup a value just by putting point on it.
    – Gastove
    Dec 3, 2015 at 19:29

1 Answer 1


It is not very clear to me what's the string that you wanted, and thing-at-point doesn't understand either. The following displays corresponding commit summary if point is at hash 36dbe6f (see eldoc-documentation-function's docstring to learn how to change it, your way seems not correct).

(defun foo-eldoc-documentation-function ()
  (let ((str (thing-at-point 'word)))
    (when (string= "36dbe6f" str)
      "* 36dbe6f More emacs-module.c fixes for wide ints")))

(add-function :before-until (local 'eldoc-documentation-function)
  • Oh huh. I may have fallen prey to emacswiki again -- it provides a completely different example than you do. I'll try your approach and check out the doc string and report back.
    – Gastove
    Dec 3, 2015 at 19:30

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