Re: Treatment of LRE,RLE,LRO,RLO,PDF,LRM,RLM

[Kenichi Handa <handa@m17n.org>]

In article <E1PCr8f-0003bZ-UC@fencepost.gnu.org>, Eli Zaretskii <eliz@gnu.org> writes:

> > Char-table to control displaying of glyphless characters.
> > Each element, if non-nil, is an ASCII acronym string (displayed in a box)
> > or one of these symbols:
> >   hexa-code: display with hexadecimal character code in a box
>     ^^^^^^^^^
> Suggest to name this "hex-code" instead.

As Google search found much more pages of "hex code" than
"hexa code", ok, I'll change the name..

> >   empty-box: display with an empty box
> >   thin-space: display with 1-pixel width space
> >   zero-width: don't display
> > 
> > It has one extra slot to control the display of a character for which
> > no font is found.  The value of the slot is `hexa-code' or `empty-box'.
> > The default is `empty-box'.

> What will happen on a TTY?

Ah, I forgot to mention about that.  At first, empty-box,
hexa-code, and acronym are displayed by using a new face
glyphless-char which is defined as this.

(defface glyphless-char
  '((((type tty)) :inherit underline)
    (t :height 0.6))
   ...)

And, for tty, as it's impossible to do the same thing as
graphic terminal, the current code does this:

thin-space: same as empty-box
hexa-code: display "U+XX", "U+XXXX", "U+XXXXXX" ,
	"E+XXXXXX" depends on the character code (the last
        one is for a character of code >= #x110000).
acronym: surround an acronym by "[" and "]" as this:
	"[ZWNJ]", "[LRE]"

At the moment, that is hardcoded in the function
produce_glyphless_glyph of term.c.

And, for tty, `no-font' means a character not encodable by
the terminal coding system.

> > glyphless-char-control is a variable defined in `characters.el'.
>   ^^^^^^^^^^^^^^^^^^^^^^
> Suggest to name this "glyphless-char-display-control".

I thought that name was too long, but if people prefer it, I
don't mind renaming to it.

---
Kenichi Handa
handa@m17n.org