Re: non-breaking spaces in view-mode

[Roland Winkler]

On Wed Jan 26 2005 Stefan Monnier wrote:
> > About a year ago I unintentionally changed my setup so that Emacs
> > used multibyte mode instead of unibyte mode.  I was rather surprised
> > that suddenly VM produced many strange results -- till I figured out
> > that it was the multibyte mode.  So I switched back to unibyte mode.
> > I haven't had any problems with VM since then.
> 
> Hmm... That's bad.  We should get VM to fix their multibyte
> support.

I've been using VM for more than ten years. Kyle, the author of VM,
used to improve it continously. Unfortunately, for about a year
there has been hardly any update. 

VM-7.19 was released 29 September 2004, which Kyle announced with
the words "I'm back from the dead." However, this release contained
mostly bugfixes. Since then, Kyle has disappeared once again from
the VM news groups. I find this very unfortunate, but it will make
it more difficult to get better multibyte support from VM.

> > No matter whether it is unibyte mode or multibyte mode (or `emacs -nw'),
> > Emacs-21.3 displays `\240' as a white space, which is what I expect to see.
> 
> Thanks.  Do you remember approximately when this changed?

I have a CVS from Dec 18, 2004 which displays the `\240'. 
Before I downloaded this version, I was using a CVS emacs for quite
some time. This CVS emacs did not display the `\240'. It always
displayed white spaces. I will check in my backup files when I
downloaded this version of CVS emacs.

> BTW, I cannot reproduce your problem: when I try the following (with the
> latest Emacs-CVS):
> 
>    LANG=fr_CH.ISO8859-1 emacs --unibyte -Q ~/tmp/foo
> 
> The code \240 in the file ~/tmp/foo is displayed as a space.
> Same thing of course if I set EMACS_UNIBYTE instead of passing
> the --unibyte argument.

I have LANG=en_US. Does this make a difference? I have used
LANG=en_US for many years.

...No, it doesn't make any difference for me. 
With LANG=fr_CH.ISO8859-1, I get the very same results I reported before

- In multibyte mode, emacs displays non-breaking spaces with a
  colored backslash and a space.

- In unibyte mode, emacs displays non-breaking space as `\240'.

- Always, "emacs -nw" displays non-breaking space just as a space,
  no matter whether it is unibyte mode or multibyte mode.

Is there any other environment variable that could influence this
behavior?

What do you see with "emacs -nw"?

> > I am just curious here: Is unibyte mode not supported anymore?
> > Well, when one uses packages like vm one needs the backward
> > compatibilty (though I know it makes maintanance of emacs much more
> > difficult).
> 
> It is still supported, but we're discouraging its use. It was
> useful back when most packages hadn't been adapted to Mule, but
> nowadays there is rarely any reason to use unibyte mode and so
> we're making less effort to try and make sure that unibyte mode
> works "as best it can" (it often uses guesses and so necessarily
> breaks down in some cases).

Maybe the info node "Enabling Multibyte" of the emacs manuel could
state more explicitly that the use of unibyte mode is discouraged.

Roland