Re: [Phpwiki-talk] tab-width

[Jeff D. <da...@da...>]

Just to clarify, the php-mode tab-width setting does not affect how
far blocks of code are indented (c-basic-offset controls that, and
I'm not suggesting changing that).

The tab-width setting (in combination with indent-tabs-mode (see below))
just controls how emacs achieves that indentation.  If tab-width is
set to 4 (as PEAR dictates), then emacs assumes that a tab character
in the text moves to the next multiple of 4 columns.    The problem with
this, is that most text file viewers assume that a tab moves to the
next multiple of 8 columns, so code which looks fine when viewed
with a tab-width setting of 4 can look severely mangled when viewed
with other programs.

> I actually rangled over this for some time with some programmer friends. I
> think I posted a link to this list that was something written by jwz about
> why you should not use tabs at all. It was pretty sound.

Yes, I agree.  Setting indent-tabs-mode to 'nil forces php-mode not to
use tabs at all, and just indent with spaces.  This is good.

The problem is that unless great care is taken to eliminate all tabs
in the source code, some tabs will remain.  When indentation is
achieved with a mixture of spaces and tabs, then things get particularly
badly munged when viewed by a viewer with a different idea of what the
tab-width is.


I think the intention of the PEAR standards is that indentation be 
achieved using only tabs.  This allows individuals to adjust
the displayed indentation just by changing the tab-width.
The problem is that even when tab-width == c-basic-offset, emacs
does not really guarantee that all indentation is achieved using
tabs rather than spaces.

If you use, e.g. 'less' to view the PEAR source code (at least
the version I've got) the problem will be immediately obvious.
In general, most blocks are indented 8 columns (since tabs were
used) --- that's ugly and hard to read as you point out, but at least
the indentation still properly shows the block structure.
However some lines in the PEAR code are indented with spaces.
Those lines only shift blocks over four columns.  The result
is that nothing lines up with anything.