bug#22786: 25.1.50; eww arabic rendering

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: mohamed.hibti@gmail.com,  22786@debbugs.gnu.org
> Date: Wed, 02 Mar 2016 17:08:40 +0000
> 
> > Do we have a literal syntax for _any_ character?
> 
> We have ?\s (presumably because people found ?  too annoyingly
> fragile).  Thinking about it a bit more, I think it would be kinda nice
> to have a literal syntax for all Unicode characters.

We have categories, so you can use \cX where X is a single letter
which denotes a category.  Se "M-x describe-categories".  This is
similar to ?\s, but the available categories are rather ad-hoc.

> Something like...  er...  ?\ucLEFT-TO-RIGHT-OVERRIDE and
> \?ucPILE-OF-POO?  We have that table already, so perhaps that's
> feasible?

It's feasible, but is it really useful?  How is it different from just
typing the character in the first place?

> But it's, of course, more important for the control characters, because
> they're just incomprehensible if you just ?💩 them...

"C-x =" usually does the job for me.

> > Btw, these controls display as thin spaces on GUI frames, and as just
> > spaces on a TTY; for best results you could cover each control with an
> > invisible text property, which would make them entirely invisible.
> 
> Hm...  perhaps it's good to (vaguely) show that they're there?  I'm not
> sure.

Could be.  I think by default they shouldn't show, but we could have
an option to reveal them.