Re: cairo and character encoding issues

[Ethan A M. <merritt@u.washington.edu>]

On Friday 23 November 2007 19:37, Allin Cottrell wrote:
> On Fri, 23 Nov 2007, Ethan A Merritt wrote:
> > 
> > > lascaux [1235] ./gnuplot...
> > 
> > > gnuplot> show locale
> > > 
> > >         LC_CTYPE is en_US.UTF-8
> > >         LC_TIME is C
> 
> This is puzzling.
> 
> 1) If LC_CTYPE is en_US.UTF-8 then g_get_charset should certainly 
> return UTF-8, which it is not doing in the cairo driver.
> 
> 2) How did LC_CTYPE _get_ to be equal to en_US.UTF-8 at this point 
> in execution, when the only command that has been issued is "show 
> locale"? 

Puzzling indeed.  With the help of many trace statements, I find that
the locale is loaded during the first call to readline_ipc() in rlgets(),
which is itself called from gp_get_string(). The body of this routine is listed below:

  /* get a line from stdin, and display a prompt if interactive */
  static char*
  gp_get_string(char * buffer, size_t len, const char * prompt)
  {
  # if defined(READLINE) || defined(HAVE_LIBREADLINE)
    if (interactive)
        return rlgets(buffer, len, prompt);
#              ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    else
        return fgets_ipc(buffer, len);
  # else /* !(READLINE || HAVE_LIBREADLINE) */
    if (interactive)
        PUT_STRING(prompt);

    return GET_STRING(buffer, len);
  # endif /* !(READLINE || HAVE_LIBREADLINE) */
  }

So we see that the use of this input path depends on the setting of "interactive"
and the presence/absence of READLINE support.

> 3) Anyway, by the time you plot a graph using cairo the LC_CTYPE 
> setting has reverted to "C".  I've verified that by sticking a 
> print before the g_get_charset() invocation:

I can't reproduce that. Once the locale gets set, it sticks.  As you would expect.


I am thinking that regardless of any possible bugs in the cairo processing,
we should be consistent and always call setlocale(LC_CTYPE,"").

Can anyone see a problem if we load the locale from the environment immediately
on program entry?


-- 
Ethan A Merritt