bug#20322: 25.0.50; indent-tabs-mode should default to nil

[Dmitry Gutov <dgutov@yandex.ru>]

On 04/15/2015 07:10 PM, Eli Zaretskii wrote:

> If it turns out that most of the modes need indent-tabs-mode set to
> nil, you can make it the default in prog-mode, or even in fundamental
> mode.

Make it the default in fundamental mode means changing the default value 
of the variable.

> As long as the modes that don't need to avoid tabs are changed
> to have the same default as now, I won't object.

I'm not aware of any popular programming language that doesn't work with 
tabs for indentation. So "need" is a pretty strong word. If the 
statistics show that spaces are more popular on GitHub for C and C++, 
why not follow the logical conclusion and change the defaults for those 
modes, too?

Note that cc-mode also services the needs of Emacs users writing Java 
and Objective-C (all seven of them), and those folks must be relatively 
modern-inclined.

And while I wouldn't mind leaving this bee's nest "as is", there's no 
way to do that just for C and C++ without introducing additional 
complication for users that *do* want to use spaces with those langs.

>> Like I said, in the end that would call for the change of the
>> default value. In the meantime, should we have an
>> xxx-indent-tabs-mode variable per major mode?
>
> I don't see a need for a mode-specific variable in this case; do you?

How, then, will the users change that value? With `add-hook', 
`xxx-mode-hook' and a lambda function?

That's a significant jump in complexity from what's currently needed to 
change `indent-tabs-mode' - either `setq-default', or actually using the 
`Customize' interface.

Think back to the four "how to configure indentation" steps I listed in 
an earlier email. Now mode-hooks and lambdas will add one or two new 
ones, and without a variable, the user will have to figure out somehow 
that the major mode function changes the `indent-tabs-mode' value.

It wouldn't have simplified the scenario for me: at the time I 
configured Emacs both for JavaScript *and* C (and a few other 
languages), to do tutorials, exercises and that kind of stuff.

>>> The vast majority of people I work with use tabs, FWIW.
>>
>> Do they use 8-column offsets, then?
>
> No (that's how I know they use tabs in the first place!).

One of us doesn't understand the other here. Just to be sure: I meant 
`c-basic-offset', not `tab-width'.

> For a customizable option, this is not an issue.  I can understand
> that the new generation may want to get rid of tabs, but since most of
> that generation don't work in C/C++, I think we can leave those alone
> for now.

The question is not what the majority of the "new generation" works in 
(probably Java, or PHP), but what fraction of C/C++ programmers uses spaces.

Anyway, just for an arbitrary example, here's the three projects using 
C++ that I've looked at most recently. All relevant to Emacs's code 
assistance (which is the area I'm paying attention to lately):

https://github.com/Sarcasm/irony-mode
https://github.com/AndersBakken/rtags
https://github.com/Valloric/ycmd

None of them use tabs.