Re: [emacs-bidi] Treatment of LRE,RLE,LRO,RLO,PDF,LRM,RLM

[Kenichi Handa]

In article <address@hidden>, Eli Zaretskii <address@hidden> writes:

> > But, if we do that, users lose control exactly which part of
> > text he selects or delete, exactly where to insert a text
> > because he can't put cursor between LRM, etc. and the
> > following character.

> Is that necessarily bad?  I'm not sure this will constitute a problem
> in the usual cases.

Just for viewing or for cuting&pasting the whole paragraph,
the hide-mode I wrote in the previous mail won't constitute
a problem.  I think that is an usual case.

A problem happens when one wants to put point at (before or
after) those formatting characters or wants to insert/delete
those characters, which doesn't seem like a usual case.

For instance, just after one inserts RLE, it can be deleted
by DEL.  But, once one moves point (and thus RLE is composed
with the following char), he must use C-d to delete that
RLE.

In addition, we have some technical problem in composing.

For instance, if you have this text:
  r2l contents is embeded here [RLE] R2L CONTENTS [PDF].
the current bidi code generates glyphs in this visual order:
   ... here [PDF] STNETNOC L2R [RLE].
and that means we can't compose [PDF] with the following ".".

And what should we do when the last character is one of
formatting characters?

At last, it seems like an abuse of composition in this case
because those formatting characters don't construct a
grapheme cluster with the following char.

> In general, I believe the recommendation is not to display zero-width
> characters.

The hide-mode doesn't display them.

---
Kenichi Handa
address@hidden