`completion-in-region'

[Leo <sdl.web@gmail.com>]

Hello,

I experimented with this new feature yesterday by using it in my local copy of
snippet.el and AUCTeX completion. I think the feature is elegant in that it
allows consistent behaviour of TAB by (setq tab-always-indent 'complete). I
have also quite a few problems (I suspect the feature is not yet stable).

completion-in-region allows a complete customise of its behaviour through
completion-in-region-functions. But minibuffer-message blocks execution for
minibuffer-message-timeout seconds (default to 2) unless there's input from
user.

For example if I define my own:
(defun my-completion-in-region (next-fun start end collection predicate)
  (when (funcall next-fun start end collection predicate)
  BODY))

BODY will only be executed after 2 seconds that gives a false slow user
experience. I can work around this problem by let-binding
minibuffer-message-timeout to 0. But I think some improvement can be done
here.

`minibuffer-complete' seems entirely designed for interactive use since it
does not pass on the return value from completion--do-completion, something
desirable when writing a function for completion-in-region-functions. One can
still use try- all- test-completion(s) but that seems to defeat the purpose of
completion-in-region.

Ever since enable (setq tab-always-indent 'complete), I have found the (ding)
noise due to no match occurs far too often and very annoying.

The above comments are based on my experience to write two completions: one
for TeX: I want the completion to automatically include a 'close' string (i.e.
{} for LaTeX macros etc.), I can write a function for
completion-at-point-functions which returns '(beg end completion-function) and
do the adding in completion-function but it is difficult to control the
position of point so that it locates between {}. Another solution is to
customise completion-in-region through completion-in-region-functions but I
need to isolate the interference between functions in
completion-in-region-functions.

Another for snippet (similar to abbrev), complete the snippet (abbrev) and
then expand if completion succeeds.

Leo