Re: Emacs 23 character code space

[Eli Zaretskii <eliz@gnu.org>]

> From: Kenichi Handa <handa@m17n.org>
> CC: emacs-devel@gnu.org
> Date: Thu, 27 Nov 2008 10:29:50 +0900
> 
> To convert between a character sequence and a byte sequence,
> Emacs actually does two steps of conversions as below.
> 
> 
> characters --(1)-> (charset code-point) pairs --(3)-> bytes
>            <-(2)--                            <-(4)--     
> 
> For the encoding of (1), Emacs uses infomaiton of coding
> system to decide which charset to use, and then uses
> informaiton of the selected charset to get a code point.
> For the decoding of (2), Emacs uses informaiton of charset
> to get character codes. 
> 
> For the encoding of (3) and the decoding of (4), Emacs uses
> only information of coding system.

Thanks.

However, does this two-step procedure make a difference for a Lisp
programmer?  It sounds like this is an internal implementation detail
that happens transparently, so Lisp programmers shouldn't care about
it.

My original confusion was about when character sets are exposed to
Lisp application programs.  I understand that one situation is when
Emacs displays a character with some font.  Are there other
situations?