Support for multibyte/wide characters in vis(3)

["J.R. Oldroyd" <jr%opal.com@localhost>]

Hi all,

Back in mid-2012 I did some work on the FreeBSD version of vis(3) to
add multibyte/wide character support.  This allows printable characters
in non-ASCII locales to be displayed as such, rather than displaying
them as \M-x sequences when LC_CTYPE is set to other than ASCII locales.

By the time I got round to submitting this patch, I found that Brooks
Davis had recently removed the FreeBSD vis(3) and imported the NetBSD
version instead in order to add the additional interfaces to the FreeBSD
library.  I have therefore had to merge my multibyte/wide char support
into the NetBSD version.

In the process of doing so, I found a bug in the NetBSD version in
which istrnvis() and istrnvisx() both handle expansion of the "extra"
argument and then call istrsnvis() and istrsnvisx() which also handle
expansion of the "extra" argument.  This results in double processing
of the extra argument, which is an error.  I have fixed this error.

Furthermore, it became clear that the five internal ixxx() functions
which all did something similar to one another were unnecessary.  It
is possible to simplify this code to just one internal function,
istrsnvisx() which is used by all the stub functions.  My update also
makes this code simplification.

In summary, this vis(3) update offers these improvements:

        - bug fix of double processing of the "extra" arg in
          some cases

        - code simplification by removing four ixxx() functions

        - multibyte/wide character support

I have tested this on FreeBSD and verified that vis(1), ps(1) and
mtree(1) still work as expected.  I've also done some additional
testing with a small program that exercises the new interfaces.

The FreeBSD vis(1) does require a small patch of its own in order to
properly read in multibyte characters.  I have not checked whether or
not the NetBSD vis(1) also needs this patch, but I'm including a
link to the FreeBSD vis(1) diff in case something similar is also
needed on NetBSD.

The FreeBSD ps(1) and mtree(1) did not require any changes to work
with the multibyte vis(3).

Do let me know of any errors or problems with this version and I'll
be happy to take a look at things.

Here are links to the updates:
        http://opal.com/jr/freebsd/vis/vis3/netbsd-vis.c
        http://opal.com/jr/freebsd/vis/vis1/vis.c.diff

The changes to vis(3) are rather extensive, so some explanation may be
helpful.  The changes come down into the following:

        - using wchar_t and wide char string library functions
          for the internal processing

        - changing "src", "dst", "extra" and associated vars to
          use wchar_t and renaming function arguments to be "mbsrc"
          etc to distinguish the multibyte strings

        - adding "L" to all wide char strings and character constants

        - using calloc() to allocate space for the internal wide
          char arrays and free() to clean them up

        - removal of check of isascii()

        - simplification of five ixxx() functions into one which
          also allowed removal of the HAVE() macro

        - fix double-processing of "extra" arg in two cases

        - minor style(9) adjustments

Thanks for considering this.

        -jr