Re: completion-ui.el question: my vimpulse-show-completion-menu function always gives me an empty menu

[Jason Spiro]

Hi list, hello Toby,

As you may know, I am working on vimpulse[1] which extends viper-mode
to emulate the most useful Vim keys in Emacs.  I am hoping to add C-n
and C-p completion to vimpulse, and I am wondering how to do so.

I am hoping to use hippie-expand because it can complete:

- words,
- filenames, and
- entire buffer lines

among other things.[2]  Dabbrev seems to basically only complete
words.  I am trying to emulate Vim's completion behavior, and Vim can
complete all those things and more.[3]

> As an Elisp coder, you're not supposed to invoke *any* completion
> interface explicitly, as you've tried to do. Deciding which combination
> of user-interfaces to use is the user's business, not the package
> writer's. Maybe some users want to use menu completion, but others
> prefer to see a list in the echo area, whilst still others just want a
> tooltip to popup after a delay, etc. etc. Completion-UI offloads those
> choices onto the user, which is where they should be.

OK.  I will tell vimpulse users they should set certain Completion-UI
settings themselves to get something closer to Vim completion.  But
meanwhile, I still have a question about the code I am writing myself
for testing purposes.

;; Begin code {{{

(require 'completion-ui)

;; Note: This code has an additional bug in addition to the problem I
;; am asking about in this mailing list message:
;; When called with a MAXNUM of nil, this func sometimes fails.  (Seems
;; to work the first time, then fail all times after, in such cases.
;; To fix, call with a normal MAXNUM.)
(defun vimpulse-try-hippie-expand-listed-functions (prefix &optional maxnum)
;  (interactive "*MString to expand:
;nMaximum number of expansions, or nil for unlimited: ")
(setq expansions nil)
(with-temp-buffer
  (insert-string prefix)
  (hippie-expand nil)
  (unless (string-equal (current-message) "No expansion found")
    (while (and
            (not (string-equal
                  (current-message)
                  "No further expansions found"))
            (if maxnum (not (= (length expansions) maxnum))))
      ;; Hippie-expand was designed to be run interactively.  If
      ;; this-command and last-command are equal, it assumes it's
      ;; being called as a "repeated use" (additional call without
      ;; moving the point) and searches for additional expansions
      ;; with the same prefix.  So, make this-command and
      ;; last-command equal.
      (setq this-command last-command)
      (hippie-expand nil)
      (add-to-list 'expansions (buffer-string))
      (buffer-string)
    ))
  expansions))

(defun jason-problem-demo ()
(interactive)
(setq-default completion-function
'vimpulse-try-hippie-expand-listed-functions)
(setq completion-function 'vimpulse-try-hippie-expand-listed-functions)
;; is this always necessary?  Am I even ever supposed to call it?
(completion-setup-overlay 'prefix)
(completion-show-menu))

;; }}} End code

Whenever I start typing a word then run
M-x jason-problem-demo I get an empty menu.  Why?

Am I using
completion-show-menu wrong?  It errors on me if I don't call
completion-setup-overlay first, so I call it first.  Should I?

Cheers,
Jason[5]

[1] http://www.emacswiki.org/cgi-bin/wiki/vimpulse.el

[2] Unfortunately hippie-expand can't complete multiple-word sequences
like dabbrev can when you press M-/ SPC M-/ SPC M-/.  Vim can do it:
just press CTRL-X CTRL-P repeatedly.  But I hope I'll eventually fix
that.

Then again, maybe I'll never have time to make that change to
hippie-expand.  So maybe I should have Completion-UI call
dabbrev-expand instead.

[3] e.g. CTRL-X CTRL-T for thesaurus completion, or many other[4] things.

[4] http://ianua.initd.org/vimit/vim63/html/insert.html#ins-completion

[5] P.S. You may want to mention in the completion-ui documentation at
the top of the file that
http://www.emacswiki.org/cgi-bin/wiki/CompletionUI#toc2 has examples
of how to use completion-ui with dabbrev and etags.  If I knew that
info, it would have saved me time. :-)

--
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