Re: Usage of standard-display-table in MSDOS

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 5 Sep 2010 02:32:43 +0300
> From: "Ehud Karni" <ehud@unix.mvs.co.il>
> Cc: eliz@gnu.org, emacs-devel@gnu.org
> Reply-to: ehud@unix.mvs.co.il
> 
> 1. lit1 - the sample file.
> 2. lit1-tty.png - how it should show on text terminal.
> 3. lit1-x.png   - how it should show on X.
> 
> I can do it if I read the file with the iso-latin-1 coding-system
> and change the display table to show the Hebrew glyphs for the Hebrew
> [#xE0-#xFA] bytes. But in this way it is not Hebrew characters (e.g.
> for the new bidi display). I want it the other way around, to read it
> with hebrew-iso-8bit and to to tweak the display table to show all
> the bytes not belonging to the Hebrew set.

The file includes Hebrew characters encoded in both hebrew-iso-8bit
and cp862, as well as line-drawing characters from cp862.

Barring bugs in the display table handling, you should be able
eventually to set up standard-display-table to display all the Hebrew
characters as you'd expect to see them, and display the line-drawing
characters correctly as well.  (Judging by the sample file, I'd
suggest to use cp862 rather than hebrew-iso-8bit, because much more
characters are from cp862.  However, you say elsewhere that most of
the characters in your files are hebrew-iso-8bit, so maybe the sample
file is not representative enough.)

But if you want all the Hebrew characters to be treated by Emacs as
such (e.g., for bidi display), no matter what's their encoding in the
file, you will have to define a coding-system that will decode them
all into Unicode codepoints of Hebrew characters.  There's a problem
you will need to solve for defining such a coding system: it has 2
different encodings for the same character, one from hebrew-iso-8bit,
the other from cp862.  So you will need to decide how will Hebrew
characters be encoded when the file is saved.

Alternatively, we could expose in Lisp the char-table used by the bidi
reordering engine for reordering characters, where you could change
the bidi class of the non-Hebrew characters that are displayed as
Hebrew.  Until now, there was no plausible use-case for changing that
table (and frankly, I'd prefer not to go there, as futzing with that
table could potentially cause trouble).