Re: Supporting tabs for indentation, spaces for alignment

[Alan Mackenzie]

Hello, Davis.

On Fri, Apr 12, 2019 at 16:39:16 +0000, Herring, Davis wrote:
> [Sent off-list because I don't know whether my DMARC issues have been
> addressed.  Feel free to share it there if you'd like to make a public
> reply.]

I'm doing this.  I believe these mail issues, as they interact with
mailing lists, are a Hard Problem.  I'm not sure how much progress has
been made on this by the admins, but they certainly haven't been
disregarding the problem.

> > Getting concrete again, my understanding (please correct me if I am
> > wrong) of what you are suggesting is: "continuation" CC Mode source
> > lines should be indented with tabs up to the indent position of the
> > "main" line, and spaces after that.  For some value of
> > "continuation" and "main" (see below).

> I'm not saying your description in terms of CC Mode internals was
> incorrect, but I'd like to provide an implementation-independent
> description that can be easily verified.  (Also, in case it hasn't
> been posted recently, the Emacs Wiki discusses this idea in some depth
> <https://www.emacswiki.org/emacs/SmartTabs>.)

Thanks, I've read that.  I've also downloaded the pertinent Elisp file.
I'm not quite sure how smart-tabs-mode works, yet, so I'm also not sure
what a secific CC Mode implementation could add.

> The definition of "continuation" is simply that tabs are used whenever
> the user chooses the width of indentation and spaces are used whenever
> the editor chooses it (by comparing column positions in the text).

So, roughly speaking, if a CC Mode "offset" is + or ++, then tabs would
be appropriate, otherwise spaces.

> There is a tacit assumption here that the amounts of indentation
> chosen by the user are expressed in units of tabs.  Conveniently, CC
> Mode already defines indentation in terms of levels, so this just
> means that a level equals a tab--i.e., that c-basic-offset and
> tab-width are not independent.  It probably makes sense to, when this
> style is engaged, (setq tab-width c-basic-offset) after computing the
> latter from whatever other style information since it is more specific
> than any global setting of tab-width.

Yes.  I'll work out the precise details.

But I'm now wondering why I should want to write a CC Mode specific
implementation.

> Hope this helps,

Very much so, thanks!

> Davis

-- 
Alan Mackenzie (Nuremberg, Germany).