Completions in Semantic

[Chong Yidong]

Hi Eric,

The completion code implemented by the semantic/complete package appears
to be quirky.  For instance:

 emacs
 M-x semantic-mode RET
 C-x C-f ~/emacs/src/xdisp.c   [visit xdisp.c in in the Emacs tree]
 C-c , j
 window[TAB]

Semantic now displays a *Completions* window with the following
contents:

 Possible completions are:
 window

But this message is misleading, because that's definitely not the only
completion.  Type:

 _[TAB]

and the *Completions* window is updated with

 Possible completions are:
 window_text_bottom_y   window_box_width        window_box_height

On a more general note, this is one of the drawbacks to the approach
taken in semantic/complete.el, i.e. trying to reimplement completion.
We've painstakingly ironed out a lot of bugs in the standard Emacs
completion code, and it makes no sense to redo all that for Semantic
unless there's a good reason.  (Not to mention inconsistency issues).

In the commentary to semantic/complete.el, you write that using
`all-completions' and `try-completion' isn't practical because they are
too slow when there are large numbers of tags.  How sure are you that
that's true?  Nowadays, the completions code is very flexible; for
instance, you can pass `all-completions' and `try-completion' a
collector function instead of a flat completion table.  Can't
semantic/complete.el make use of this functionality?