Re: [Emacs-diffs] trunk r116461: Connect electric-indent-mode up with CC Mode. Bug #15478.

[Alan Mackenzie]

Hello, Stefan.

On Sun, Mar 23, 2014 at 09:37:09PM -0400, Stefan wrote:
> > The actual definition of "electricity" is found in the Emacs manual, page

> Use in other packages shows that people have understood the notion of
> "electric" to mean many other things beside the very restricted
> semantics you point to.

Yes, but as used in "electric indentation", I think the terminology, and
the methodology, has been as in C Mode's definition up until very
recently.

> > No.  To keep Elisp properly indented, you merely have to depress
> > whichever key is bound to `newline-and-indent', whether that be RET, or
> > C-j, or whatever.

> "whichever key is bound to `newline-and-indent'" would be C-j and not
> RET in all Emacsen released so far, so I see we violently agree.

> > Electric indentation doesn't come into it.

> Of course it does because electric-indent changes the behavior such that
> RET can be (or has to be in 24.4) used instead of C-j.  But you knew
> that, obviously.

OK, I meant "electric indentation" as defined in the manual page -
"reindenting the current line".  This has nothing to do with which way
round C-j and RET are bound.

> > You'll want electric indentation on some other character you've just
> > typed.

> Indeed that's also good.  But I don't know of any such character we
> could use globally in electric-indent-chars, so it's up to each major
> mode to specify which chars to use.

Yes.

> > No.  If electric indentation has already happened after typing the
> > semicolon/comma/brace, the alignment of the subsequent comment will
> > remain undisturbed.  If RET puts the alignment out, you're cursing it.

> Then I misunderstood and don't know what you're talking about.  Can you
> give a scenario?

Assume that electric indentation happens on \n, and not on {.  You type
in a { (which is intrinsically 4 characters too indented, for some value
of 4) then do M-; to insert a comment at comment-column.  You fill in the
comment, do C-e then RET.  The ensuing electric indentation on RET puts
out the alignment of the comment:

                            if (foo)       /* aligned comment */
                            {          /* coment misaligned by e-i-m */

> >> What would be more optimal?
> > A mode-dependent or buffer-local dependent setting, as well as, rather
> > than instead of.

> We have that: electric-indent-local-mode and electric-indent-inhibit.

OK, for electric-indent-local-mode, which is gradually becoming
prominent.  But I though electric-indent-inhibit was a variable for major
modes, not users - a mode initialisation thing, rather than a user
configuration variable.

> > Why can't we simply have RET bound to `newline-and-indent' and C-j
> > bound to `newline' in programming modes, as discussed and, pretty much
> > agreed on, in emacs-devel last autumn?

> Lack of patch implementing this (supposed) simple change?

Here is what I propose, and am willing to do:
1. For electric indentation:
  a - Restore `newline' and `newline-and-indent' to their traditional
    functionality, and remove `electric-newline-and-maybe-indent'.
  b - Simplify `electric-indent-post-self-insert-function' such that it
    reindents only the line on which the self-inserting character is
    typed.
  c - Reform `electric-indent-local-mode' as a first-class minor mode and
    `electric-indent-mode' as a global version of it.
2. For making RET indent the new line in programming modes:
  a - Bind RET to `newline-and-indent' and C-j to `newline' in
    `prog-mode-map' and possibly in certain other major mode maps (to be
    discussed).
  b - (Maybe) create a minor mode to restore RET and C-j to traditional
    bindings.

The above will leave electric-indent-mode functioning pretty much as it
currently does.  What do you say?

> > Incidentally, in Emacs -Q, Text Mode and Fundamental Mode have gone back
> > to the unwanted state of RET doing `newline-and-indent'.  Should I raise
> > another bug report?

> You can, but it's not a bug.  It's a feature (not sure what you mean by
> "back" since it's been this way ever since I enabled
> electric-indent-mode by default, AFAIK).

Apologies: I thought Text Mode had been restored to the traditional
bindings in the last few months.

> So make this bug report specific about a particular circumstance where
> the behavior is undesirable, or about how hard it is to disable it.

I think RMS's bug #16156, reproduced and being discussed on a parallel
thread, is a good enough example, so there's not much point in me opening
a new one.

>         Stefan

-- 
Alan Mackenzie (Nuremberg, Germany).